Ground Characterization and Foundations

The present work encompasses a detailed study conducted on the effect of amount and type of fines on the properties of sand. The analysis is based on various tests including specific gravity, particle size analysis, consolidation tests, direct shear tests, etc., conducted on 17 soil combinations. The soil combinations were prepared by mixing sand with fines (0–40%) of different PI ranging from 0–15%. The variations in specific gravity, particle size characteristics (D50, Cu and Cc), limiting void ratios (emax and emin), angle of internal friction in loosest and densest possible state and compression index in loosest and densest state with respect to variations in the amount of fines and plasticity of fines are presented. Results indicate that there is a significant influence of fines on the properties of sand.

The permeability of soil plays an important role in estimating the quantity of seepage under foundation of hydraulic structures which in turn affect the stability of structures. Empirical correlations such as Hazen, Kozeny-Carman, Breyer, Slitcher, Terzaghi, USBR, Alyamani and Sen are function of grain sizes, porosity/void ratio, co-efficient of uniformity (Cu), co-efficient of curvature (Cc) and viscosity of pore fluids, etc. These correlations are quite effective for preliminary assessment of permeability during prefeasibility stage. However, at the designing stage, actual measurement of permeability is very important for structural integrity. Soil is not homogeneous, and permeability varies from location to location. Actual ground conditions vary from place to place. Moreover, soil profile is not uniform but varies from one section to other. In some places, it may be dense, partially dense and loose or submerged in water. Depending upon the condition of ground, permeability will also vary from place to place. Keeping in mind the various ground conditions, attempt has been made to determine the co-efficient of permeability on the soil samples remoulded at different compactness and moisture conditions. In the present study, attempt has been made to correlate permeability values obtained through different correlations with laboratories values.

Engineering properties are determined from various tests performed on undisturbed samples collected from the site. These test results depend upon the method of testing, loading conditions, strain rate, loading rate, etc. Some of the tests require a considerable amount of time. So for initial requirements like preparation of a budget, estimates, preliminary designs, etc., alternative methods have to be chosen. Many theoretical and prediction methods are already available in the literature; however, not much studies have been done for soils available in Kerala. Two major types of soils seen in Kerala are lateritic soil near the Western Ghats and soft soils in lowlands like Kuttanad and backwater environment. The objective of this paper is to develop predictive equation for determining the engineering properties from the available index properties for soil collected from Kerala. The main engineering properties considered are shear strength and coefficient of consolidation. For this study, the soil data was collected from various geotechnical consulting firms who have undertaken various infrastructural projects in Kerala. Artificial neural network (ANN) tool of MATLAB and regression analysis was used for predicting the properties. In ANN, Levenberg–Marquardt algorithm was used for training the network. From the results, it was concluded that, for Kerala soils, the developed predictive equation is more accurate than equations already available in literature. Also, the neural network tool can model the relation much reliable than conventional regression analysis.

For improving soil properties, use of natural fiber is advantageous because they are cheap, locally available, biodegradable and eco-friendly. Therefore, in the present investigation, coir fiber has been chosen as the reinforcement material and randomly included in to the soil at different percentages of fiber content, i.e., 0, 0.5, 1 and 1.5% by weight of raw soil. The soil used for this research is highly compressible soil. Length of fiber is considered as 20 mm for this study. The objective of this investigation is focused on the durability of soil reinforced with coir fiber. The compaction, unconfined compressive strength (UCC) and California bearing ratio (CBR) tests are conducted for each percentage of natural fiber mixed with soil. For finding the durability of coir-reinforced soil, the specimens for UCC test is prepared with optimum fiber content (OFC) by using concentrated hydrochloric acid (HCL) solution as pore fluid. The fibers with and without bitumen emulsion coating are used in the study. Thus, prepared samples are cured for 7 and 30 days. Based on the results obtained, it is observed that the inclusion of coir fiber improves the strength of the soil, and bitumen emulsion-treated coir fiber has more durability.

Organic soils are characterized by their high water holding capacity, low shear strength and large compressibility. The properties of organic soil have to be improved before using it for any construction purpose. Lime stabilization is one of the most popular methods used to enhance the properties of clayey soils. Previous studies have shown that the improving effect of lime gets deteriorated in the presence of organic matter with time. In this paper, an attempt is made to study the effect of longer curing period (up to 120 days) on the geotechnical properties of lime-treated organic soils. The tests were carried out on artificially prepared organic soil mixtures treated with 6% lime. Various laboratory tests like Atterberg limits test, free swell index test, unconfined compressive test and one-dimensional consolidation tests were conducted on artificial organic soil treated with lime at different curing periods (0, 7, 30, 60, 90 and 120 days) to examine the effect of each parameter. The test results reveal that the effect of lime stabilization is nullified by the presence of organic matter at longer curing periods. The plasticity characteristics of lime-treated organic soils varied with curing period. The unconfined compressive strength of lime-treated organic soil decreased after 90 days of curing. Compression index of lime-treated organic soil samples increased after 120 days curing period.

The shear strength of soil is not an intrinsic property of soil but varies over a considerable change under varying conditions. The shearing strength of soil depends on density, moisture content, grain size, particle shape and gradation. An attempt has been made in this project to study the shear strength characteristics of marine sand deposits along the Eastern coast of Tamil Nadu such as Pichavaram, Pazhayar, Nagapattinam and Samiyarpettai. Borehole sand at different depths was collected by conducting SPT. The soil samples were tested in loose dry, loose saturated, dense dry and dense saturated condition by direct shear test. Soil samples were collected at two different depths at each site. The different shear tests have been carried out at a constant strain rate of 0.25 mm per minute for all the 32 tests. The variation of the friction angle under different conditions has been discussed and presented in this work. Angle of internal friction for the above soils has been determined for peak shear strength and shear strength corresponding to a constant volume. There is considerable difference in the observed friction angles from the above two conditions. This difference is more for the saturated soils. Higher values of friction angles were observed for the sand collected from Nagapattinam and Samiyarpettai regions than that of the samples collected from Pichavaram and Pazhayar regions. This is due to the more angularity of the soil particles in the Nagapattinam and Samiyarpettai regions.

In this paper, the shrinkage behavior of silty clay soil widely found in Warangal is characterized under free evaporation condition over a wide range of suction. As a part of the research evaluation, a comprehensive laboratory test program was framed and conducted on the samples collected from Warangal. Slurries of soil samples were subjected to desaturation by evaporation, and the change in the sample dimension was captured with camera still images and Vernier caliper. The captured images were processed and used for quantifying the overall volume change. The shrinkage behavior was represented as soil shrinkage curve (SSC), and the curve exhibited three zones. The proportional or normal shrinkage was dominant with volume of water lost from the pores equaling the volume change in the sample. The structural and residual shrinkage phase indicated the loss of water from both inter- and intra-aggregate pore spaces with gradual increase in time. The study showed the existence of bimodal porosity in low plasticity soil and also discusses the reliable efficiency of the proposed experimental procedure to study the shrinkage behavior of soils with low plasticity.

Geotechnical site characterization plays significant role in brown field sites where heterogeneous materials get mixed with original soils during various stages of plant expansion over a long period. The Triad Approach developed by the United States Environmental Protection Agency (EPA) used in decision making for investigation in hazardous-waste sites is an effective strategy for site assessments. The term ‘Triad’ represents three elements: systematic project planning (SPP), dynamic work strategies (DWS), and use of real-time measurement (RTM) technologies. This concept can be extended to geotechnical characterization of brown field sites. This paper will describe the application of the Triad Approach for development of brown field project site inside a 100-year-old steel plant. This approach accelerates the characterization of the 45-acre project area, which consists of construction of new process plants in an existing steel plant site. Successful brown field site development requires the planning of geotechnical tests, data collection, analysis, and interpretation of field and laboratory results in timely and cost-effective manner. The planning and scheduling required to define potential criticalities and uncertainty in ground conditions allow designers to effectively use resources, optimize space constraints and develop response strategies that will mitigate risk with an eye to execution safety, ease, and time. The decision on foundation system and ground improvement required during the underground construction activity have great impact on brown field project schedule and overall cost. The triad approach consists of planned geotechnical investigation combined with systematic foundation planning based on real-time data that optimally uses available resources and accounts for space and time constraints. In addition, issues that were solved include the demarcation of the extent of heterogeneous fill material, determining further action for the areas of concern and specifying no action for other areas, and detailed investigation of specific impacted areas.

Ground improvement is a crucial and inevitable step in geotechnical engineering. Many stabilisers have been used all over the world to improve the problematic soil. The stabilized soil materials have a higher strength, lower permeability and lower compressibility than the native soil. In this study, sandy clay with silt is improved with the help of lime and palm fibre. Improvement in geotechnical properties is found out by conducting compaction and unconfined compressive strength. Here 2 cm long palm fibre with 0.1, 0.2, 0.3 and 0.4% are added to soil treated with 10% (OLC) lime. Up to an optimum percentage, shear strength increases with increase in fibre content. Also the value of strain increases with increase in fibre content. Tests are conducted for both random mix and horizontal mix of fibres. This research concludes that combination of lime and palm fibre is a better stabiliser for ground.

Expansive soils are perhaps the most challenging soils in the world. They are prone to swelling with variations in seasonal moisture conditions. Hence, this change in soil volume can cause significant structural damages in overlying light buildings such as highway pavements, low-story buildings, and alike. A number of attempts have been made to evaluate the swelling pressures of expansive soils using different methods by oedometer test set-up with applied stress. Till date, the direct method, for measuring the swelling pressure, has not received much attention. However, in case of expansive soils stabilized using chemical binder which is involved with time depended pozzolanic reaction, a direct measure of swelling pressure in swelling phase itself would perhaps be more reliable. Hence, in this study, a direct method was employed where a proving ring which was designed and calibrated to measure the amount of swelling pressure in the swelling phase itself. Swell-consolidation tests were employed as indirect methods. Results indicated that the highest swelling pressures were measured by swell-consolidation test. The lowest measures were produced by the direct method, respectively. It could be argued that during the swell-consolidation tests, the development of cementation particle might be affected to the swell pressure. In direct method, swell pressure has measured in the first 24 h, and hence, the impact of cementation on swell pressure might be less.

Lightweight structures that are constructed on clay would experience the uplift and settlement due to changes in moisture content. Soil with high plasticity could cause problems to the structures. Good numbers of options are available to stabilize the highly plastic clays. One such option in the recent past is the utilization of gypsum in soil stabilization. Gypsum can be derived from demolished building sites as waste. This paper presents the behavior of clay stabilized with gypsum, and also the effect of CaCl2 on the improvement of CBR and shear characteristics. The tests such as of standard compaction, California Bearing Ratio (CBR), free swell index (FSI), and direct shear are conducted. The proportions of gypsum used in the study are 0, 2, 4, 6, and 8% by dry weight of soil. A 2% CaCl2 is added to the clay which is stabilized at 6% gypsum in order to see the improvement in soil behavior. The results revealed that as % gypsum increases from 0 to 8%; initially, there was an increase in the maximum dry density (MDD) up to 4% gypsum content, and thereafter, it showed little decrease in MDD. The CBR of high plastic clay stabilized with gypsum showed marginal improvement. Free swell index of gypsum treated clay is reduced to almost 50% at 8% gypsum. For the gypsum stabilized clay when 2% CaCl2 is added, resulted in a further increase in CBR and MDD. The 6% gypsum and 2% CaCl2 addition to the high plastic clay resulted in improvement in strength and CBR values.

In geotechnical engineering practice, a better understanding of the fundamental behavior of soil will provide a focused insight to begin decisions on new and emerging geotechnologies. Owing to lack of availability of coarse-grained soils, fine-grained soils having different clay mineralogical compositions are being used as an alternative eco-friendly material for construction activities. The engineering behavior of such soils varies significantly due to the presence of kaolinite—the mineral which is least active and montmorillonite—the mineral which is most active in different percentage. To have a general trend behavior of these soils around the globe requires more time and financial implications. As per the present experiment done, we have tried to represent the natural fine-grained soils having clay minerals through artificially prepared soils in the laboratory by preparing a series of mix proportions of china clay–bentonite–sand in varying proportions. The physical properties of the mix proportions were determined as per BIS specifications. IS light and heavy compaction test were conducted on mix proportion akin to standard Proctor and modified Proctor tests. In addition, reduced standard and reduced modified Proctor tests (compacted at 60% of their respective energy level) were performed on the artificially prepared mix proportions. We made an effort to correlate the physical properties of the mix proportions with compaction characteristics. Very useful correlations were also developed between the compaction characteristics of the mix proportions, subjected to varying energy levels and clay mineralogical composition with plasticity characteristics. We also made an effort to compare the compaction characteristics of natural fine-grained soils having the similar composition of fines and clay mineralogy with that of mix proportions.

A large number of engineering hazards on constructions based on gypsum soils have been documented all over the world. Gypsum sands are especially found in the dry parts of the world. The problem of dissolution and settlement is one of the most widespread among gypsum soils. Gypsum sands are complex materials and the effect of the geotechnical parameters on settlement behavior of gypsum soils has been studied by several researchers over the years, but the results were found to be varying. Also, there have not been many geophysical investigation techniques that were used to study gypsum soils. In this study, the effect of several factors like gypsum content, water content, leaching and dissolution of gypsum and time on the settlement of reconstituted gypsum sands were investigated. Settlement due to initial moisture and leaching was studied by subjecting the soil specimens to a rapid drained loading of 200 kPa. The long-term settlement of the soil samples was studied using the consolidation test setup. Further, electrical resistivity tests were conducted on the soil samples using a four-electrode soil resistivity box. The effect of moisture content, gypsum content and density on electrical resistivity was investigated. The studies showed that settlement of the gypsum sands increased with gypsum content, initial moisture, leaching and time. The soil box resistivity tests showed that, moisture content had a major influence on resistivity, while gypsum content and density had less influence on the resistivity. Based on the results, it was concluded that electrical resistivity testing could be a moderately successful method for estimating the settlement of gypsum sands.

Liquefaction of soil is one of the important concerns for the geotechnical investigators, as it leads to major casualties after natural disasters like earthquakes. Potential of liquefaction mainly depends on the soil type and the magnitude of earthquake. Developing a liquefaction susceptibility map is one of the essential steps in disaster preparedness and this study proposed a novel framework for developing liquefaction susceptibility maps by correlating the soil investigation data with equivalent acceleration obtained using the site response analysis. The usefulness of the method is demonstrated by developing the liquefaction susceptibility map of soils across state of Kerala, India. In this approach, first the standard penetration test (SPT) N values of soil from a specific location was subjected to a correction corresponding to the fine content and plasticity index of the soil, to get the equivalent N value. Then, the equivalent acceleration was analysed through site response analysis using ProShake 2.0 software for a peak acceleration of 0.16 × g. The obtained results were corrected for a wave correction to scale down the earthquake magnitude corresponding to the study area. Subsequently, the point corresponds to equivalent N value and equivalent acceleration was superimposed with the universal reference liquefaction chart proposed by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) Japan to identify the zone of liquefaction susceptibility of the study area. The method is validated with different case histories from Kerala and extended to different soil types across the state.

In geotechnical engineering, a thorough understanding of the fundamental behaviour of soils plays a pivotal role in the engineering design of earthen structures. The engineering behaviour of coarse-grained soils is a physical phenomenon whereas for the fine-grained soil it is a physico-chemical phenomenon. The behaviour of fine-grained soil becomes more complex one due to the contradictory behaviour of principal clay minerals present i.e., Kaolinite, Montmorillonite in varying proportions in the soil matrix. Further, it is seldom observed that, owing to scare availability of coarse-grained soils at large quantity, forcing construction industry to use fine-grained soils having different clay mineralogy as an alternative material for a better construction. The plasticity characteristics of fine-grained soils predominantly control the engineering behaviour to greater extent. In the present experimental study, a series of mix proportions of commercially available China clay, Bentonite along with Sand were artificially prepared in the laboratory representing Kaolinite and Montmorillonite soils behaviour. The physical properties of the mix proportion were determined as per BIS specifications. The plasticity characteristics of mix proportion were correlated with plasticity characteristics of natural fine-grained soils. The new plasticity chart was developed which is akin to the IS plasticity chart. The activity of the mix proportions was also analysed and compared with that of natural fine-grained soils.

Over consolidated natural soils exhibit characteristic stress, known as pre-consolidation stress (σp1) which represents the maximum stress to which the soil has been subjected in the past. The soil used in various geotechnical mass applications like earthen embankments, dam, etc., will be subjected to some specified compactive effort which is akin to over consolidation. Hence, compacted soils are also expected to possess a characteristic stress similar to preconsolidation stress of over-consolidated natural soils. Compacted fine-grained soil application for civil engineering applications is becoming more vital role to non-availability of coarse-grained soils at large. The engineering behaviour of fine-grained soils becomes more complex because of the presence of different clay minerals in various proportions. The present experimental study aims to study the variation of pre consolidation stress of compacted fine-grained soils having same liquid limit, different plasticity characteristics and clay mineralogy subjected to light and heavy compaction energy levels. An attempt has been made for the detailed study of the variation of preconsolidation stress by five user-friendly methods documented in the literature with placement conditions, clay minerology and compaction energy levels. Very interesting observations were made with respect to variation of preconsolidation stress with clay mineralogy, compaction energy levels and placement conditions. Useful correlations were also developed for the estimation of preconsolidation stress with particular reference to the method of determination of σp1 and engineering behaviour like compaction characteristics. The study also highlights the role of clay minerology on pre-consolidation stress and placement condition.

Consolidation of problematic soils such as soft or compressible soils with high clay content can be overcome by preloading along with Prefabricated Vertical Drains (PVDs) which is one of the most common techniques used over the past few years. Parameters that influence consolidation or rate of settlement at the site are coefficient of consolidation for horizontal/radial flow, smear effects such diameter of and permeability of remolded or disturbed soil in the smear zone. In this paper, degree of consolidation at the end of construction (Utc), final settlements, SfA, from Asaoka plots for degree of consolidation with time factor, under ramp loading with smear effects (s), the ratio of diameter of smear zone to that of drain, and kh/ks, the ratio of permeability on in situ soil to that of soil in the smear zone), have been developed for different unit cell diameter ratios, n, and time factors, Tc, corresponding to end of construction. A new method for the estimation of in situ parameters such as Cr, s and kh/ks of the smear zone from the in situ measured time-settlement plot, is proposed.

A geophysical method named ground-penetrating radar (GPR) can be applied to geotechnical investigation to determine the underground conditions. In this study, a GPR is used to detect the ballast condition of the railway track. The ballast bed plays an important role in rail track keeping the gauge between sleepers and thereby position of the rails. As the train moves over the track, ballast helps to hold the track in place. Ballast fouling is formed by coal dust and the breakdown of ballast or from soil interference under the rail track. The rail track can be damaged substantially due to the fouling material such as coal, metal piece and large stone. This paper presents the non-destructive testing method, namely ground-penetrating radar (GPR) for identification of different types of materials. To detect the underground substructures, 800 MHz ground-coupled antenna was used. Constructed a model rail track with different fouling material are buried under the subsurface structures. This work is carried out in Civil Engineering laboratory, IISc, Bangalore. This research work presents the detection of underground structures like different metals, big-sized ballast and clean ballast. Find maximum change-point algorithm is proposed to detect the abrupt changes in the signal; by this, it will also detect the size of a target by calculating the start and end trace of the buried object. It is important for the diagnosis of ground substructures. This paper also describes the application of wavelet decomposition to detect the condition of the ballast viz clean or fouled. The wavelet decomposition finds the shape of the object by calculating the higher-order statistical parameters like skewness test and kurtosis test.

Problematic soil needs great care to deal with, due to their swelling and shrinkage characteristics. Due to moisture variation, the volume of the soil varies accordingly and often leads to differential settlement on superstructure and foundation. Such a nature of expansiveness of soil leads to create negative skin friction on the pile foundation, which further increased the cost of design and construction. To counteract such arisen problem, we made an extensive effort using an application of the geotextile in the foundation soil beside the traditionally available methods of stabilization by different means. A combined system of geotextile and micropile was tested in a series of the experimental plan with and without geotextile. The present study shows the findings of the extensive research which was carried out for understanding the effectiveness of geotextile micropile system. Field condition was constructed in the laboratory by a model tank. Heave action was examined using the dial gauge reading, and comparison was made with a footing base without micropile. Geotextile was used in the single and two-layer, single at 0.33 B and doubled at 0.33 B and 0.67 B from the footing plate. Test results show that it has a 48% reduction in heave by using the four micropiles. Further with adding the geotextile layers, it has 63 and 71% heave reduction for one- and two-layer geotextile, respectively.

Knowledge of the stress–strain properties of rock and rock mass is important for any rock engineering project involving rock. Deformability behaviour of rock or rock mass is denoted by modulus of deformation (Ed). Deformation modulus of intact rock can be evaluated in the laboratory, whereas field testing is required for in-situ modulus of discontinuous rock mass. Uniaxial jacking test is one of the direct methods used for the assessment of in-situ deformation modulus. Indirect methods based on correlations between rock mass classifications and deformation modulus developed by many researchers are also available. Results of 28 in-situ tests conducted on fresh, hard, compact, medium-grained sandstone have been compared with values derived from empirical equations developed by Bieniawski (Int J Rock Mech Min Sci Geomech Abst 15(5):237–247, [9]), Barton et al. (Application of the Q-system in design decisions concerning dimensions and appropriate support for underground installations, pp. 553–561, [13]), Serafim and Pereira (Consideration of the geomechanics classification of Bieniawski, pp. II33–II42, [10]), Barton (The influence of joint properties in modelling jointed rock masses. Balkema, Rotterdam [11], Barton in Estimating Rock Mass Deformation Modulus for Excavation Disturbed Zone Studies, [14]) and Singh and Bhasin (Q-system and deformability of rock mass, pp. 57–67, [15]). Q values of rock mass range from 3.4 to 10. The study reveals that the modulus from indirect estimates gives very high modulus of rock mass. Indirect estimate suggested by Barton (Barton in Estimating Rock Mass Deformation Modulus for Excavation Disturbed Zone Studies, [14]) for excavation disturbed zone, provides value near to direct estimate, i.e. in-situ data set. Study further reveals the empirical equations based on Q-system of rock classifications are valid for Q > 1.

A series of static cone penetration tests and undrained triaxial tests is performed to determine undrained shear strength of clayey soil. The field static cone penetration test is conducted on Marine Clay Soil near Naygaon West, Mumbai. It will be very precise, if we able determine the undrained shear strength of clayey soil using field tests. Therefore, in this research, we have developed empirical relationship between the parameters of static cone penetration test and triaxial test, so that using the field parameters we can able to determine undrained shear strength of clay soil. Mainly the static cone penetration test gives end bearing, frictional resistance, and corresponding cone factor of clay soil for various depths, which are then related with the laboratory parameters like Atterberg’s limits and undrained shear strength of clay for the same depths [1]. From the empirical relationship between field parameters and laboratory parameters, we are able to develop coefficient called as cone factor K, which will help us to determine undrained shear strength of soil directly on site for similar types of clayey soil [2].

Deformation modulus of rock is a basic parameter required for the design of any structure involving rock as foundation and abutments. The study of rock behaviour under external stresses is important for the safety analysis of the structure. A multipurpose project involving a 278 m high-concrete gravity dam in Eastern Himalayas is under investigation stage. The rock type is mainly feldspathic gneiss with biotite schist. Stresses on foundation rock on account of the proposed dam are expected to be of the order of 6–10 MPa. Due to limitations of testing equipment, uniaxial jacking tests could not be performed upto the desired stress level. Hence, in situ Borehole jack (commonly known as Goodman Jack) tests were preferred wherein stress of the order of 10 MPa was applied for evaluating the modulus of deformation of rock mass. Orientation of stress was varied to study the anisotropic behaviour of rock mass. Deformation modulus of feldspathic gneisses and anisotropic behaviour under different loading directions have been discussed in this paper. The tests were conducted in fresh rock simultaneously with drilling. This enabled to study the stress-deformation behaviour of rock representing the fresh rock without deterioration by way of weathering and other environmental factors.

The load–penetration behaviour of virgin soil is compared with initial lime consumption of the soil as lime column and lime column with 0.5% of Nano-Alumina in column form. Tests were conducted in CBR mould with a consistency index of 0.42 under soaked and unsoaked condition. Unsoaked condition tests were conducted after two hours of preparation of soil sample and for soaked condition, and the sample is immersed in the water for four days. Tests results from unsoaked condition show with inclusion of lime, the load-bearing increases by about 40% and with the addition of Nano-Alumina into the lime column, it increases by 105%. Whereas under soaked conditions, the increase in percentage is 20% for both soaked and unsoaked condition.

Rockfill dams are commonly being constructed to store the natural river water for using to generate the electricity, irrigation, drinking and industry etc. Rockfill material consisting of gravel, cobbles and boulders obtained either by natural riverbed and blasting the rock quarry. These materials are being used because of their inherent flexibility, capacity to absorb large seismic energy, reduce pore water pressure and adaptability to various foundation conditions. The engineering behavior of rockfill material affects due to mineral composition, particle size, shape, surface texture, confining pressure, gradation etc. Rockfill materials consist of particles of large size more than 1200 mm and this cannot be tested directly in the laboratory. Some kind of modeling technique is often used to scale down the size of particles so that the specimen prepared with smaller size particles can be tested in the laboratory. Among all modeling techniques, the parallel gradation technique is the most commonly used and the same has been used in the present study. The alluvial riverbed rockfill material is obtained from a hydropower project in Jammu & Kashmir. The maximum particle size used in the dam is 600 mm. For testing, the maximum particle size (dmax) is scaled down to 25, 50 and 80 mm by parallel gradation technique. All the dmax are tested for 87% relative density. Large size-drained triaxial tests are carried out with a specimen size of 381-mm diameter and 813-mm height with varying confining pressures from 0.6 to 1.8 MPa. Engineering behavior means stress–strain-volume change behavior of all the dmax under different confining pressures are studied and presented.

In the present study, to verify the developed methods, modelled riverbed rockfill material from Tehri dam old dobatta borrow area, Uttarakhand, India has been considered, tested and studied the material behaviour. Using the developed methods, ϕ, E and ν are predicted for all the tested modelled rockfill and compared with the test results. From the comparison, it is observed that both results match closely. Therefore, ϕ, E and ν value of the prototype rockfill material are predicted using the proposed methods for designing the rockfill dam. The advantage of the proposed methods is to determine the material parameters using index properties viz. UCS, UVC and RD without conducting large size triaxial shear tests. Developed methods are more realistic, economical, can be used where large size triaxial testing facilities are not available. A quarter of the triaxial specimen with axisymmetric geometry has been modelled using hierarchical single surface (HISS) constitutive model and DSC-SST2D computer software. Stress–strain-volume change behaviour of tested modelled rockfill was back predicted and compared with the experimental results. From the comparison, it is observed that both results match closely. Predicted the stress–strain-volume change behaviour for prototype rockfill material, and it is observed that its behaviour also follows similar trend as that of modelled rockfill material. Therefore, it is proposed that HISS constitutive model can be used to characterize the riverbed rockfill material successfully.

Many researchers with the help of artificial neural network (ANN) have tried to capture the nonlinear behavior of various inputs and output parameters relevant to soil deformation problems. The objective of this study is to calibrate neural network models for prediction of shear stress-shear strain behavior as per the Mohr–Coulomb criterion, from basic soil properties. ANN with feed-forward backpropagation method and recurrent neural network (RNN) training method is used to predict the desired output. The direct shear test is commonly used by geotechnical engineers to obtain the cohesion and angle of internal friction for field soils. The soil sample used in the experiment is 425 µm passing, and also, it includes soil as the main constituent with added bentonite of variable proportions. This research aims at investigating the reliability of using the direct shear test for soil sample with different percentage of bentonite with 10% water content by weight under an adequate shearing strain. The test is performed with three different loading conditions (a) 0.5 kg/cm2, (b) 1 kg/cm2 and (c) 1.5 kg/cm2. On comparing experimental results with predicted results obtained from the ANN model and RNN model, it is found that the RNN model gives better results.

Followed by the recent moderate January 3, 2017, Ambassa earthquake (Mw = 5.7) epicenter located at Dhalai district of Tripura, the state witnessed cases of ground failures due to liquefaction, landslides, and several cases of partial and complete damage of non-engineered/semi-engineered houses/buildings within the near vicinity of epicentral areas. Reconnaissanse study of failures prompted to carry out local site response analysis of important urban agglomeration in order to estimate the seismic hazard for a future event. Above all, Tripura is situated in the severely vulnerable zone (zone V) as per seismic zoning map of India. In this context, the present study is aimed to perform one-dimensional ground response analysis (1D GRA) of Agartala town, the capital place of Tripura where significant infrastructural growth is booming up presently due to its salient location in the global map. The geological condition of this area categorized as sedimented ‘Bengal basin’ with relatively younger alluvium/fluvial river deposits of Holocene age. Site classes D and E of the NEHRP classification are dominant in the area investigated. 1D nonlinear GRA is performed using DEEPSOIL on twenty representative boreholes data. Synthetic ground motion is generated considering past local earthquakes using Boore’s point source model (Boore 1983, 2003) and used in this study since reliable ground motion data from potentially damaging past earthquakes are scarce in this region.

Expansive soils are known as problematic due to their significant volume change during seasonal moisture fluctuation. The present study reports the suitability of alkali-activated fly ash as an alternate binder, to conventional stabilizers like cement, used to mitigate the volumetric shrinkage of expansive soil. Alkali-activated fly ash is an alternative binder in which liquid alkali activator (LAA) is added to FA, which consists of 50:50 sodium silicates (Na2SiO3) and sodium hydroxide (NaOH) solution by weight. Laboratory investigation includes the determination of volumetric shrinkage strain through image analysis and scanning electron microscopy (SEM) images at 7-, 14-, and 28-days curing period. Results indicate a significant reduction in volumetric shrinkage strains from 56 to 15, 11, and 5%, respectively, with a treatment of expansive soil with LAA/FA = 1, 1.25, and 1.5 at a curing period of 28 days. The SEM images captured to observe the microstructural changes at a 28-days curing period reveal that the right amount of dense crystalline products is formed at an LAA/FA = 1.5. From the analysis, an LAA/FA ratio of 1.25 may be considered as an optimum dosage to control the volumetric shrinkage strain.

A comparative study on the effect of nano-silica (NS) on physical, chemical, and microstructural characteristics of soft soil were investigated. Nano-silica is widely used in concrete and cement-stabilized soft soil to enhance macro performance. Up to now, the improvement of soft soil using nano-silica is not completely explored. In this study, a comparison has been done to determine the potential of nano-silica to stabilize the soil. Different experimental work has been performed, especially the standard proctor test, unconfined compressive strength (UCS), and California bearing ratio (CBR) of clay with highly compressible (CH) soil adding nano-silica. The soil considered here accommodates varying percentages of nano-silica (0.6, 0.8, 1, 1.5% by weight of soil) and is added for investigation of the relative strength enhance of soil. The present study is to evaluate the maximum dry density, unconfined compressive strength, and California bearing ratio of soil using varying percentages of nano-silica. The test outcomes explain that the shear strength, UCS, and CBR values of soil increase by the addition of nano-silica in soil. The result showed that the addition of nano-silica with soft soil can accelerate hydration, improve the interfacial zone between soil particles and binder, due to pozzolanic nature and fine particle size. By using scanning electron microscopy (SEM), the interaction at the interface between nano-silica and soil matrix was analyzed. And by energy-dispersive X-ray spectroscopy technique (EDS), the elements and chemical characteristics of soil are analyzed.

Expansive soils could be a problematic soil in construction industry as it exhibits volume change behaviour due to seasonal moisture changes. Chemical stabilization techniques are usually the most sought-after techniques to curtail the swell-shrink behaviour. The shrinkage behaviour of the expansive soil leads to a network of surface crack development which could progress into deeper depths. Moreover, the development of cracks could be an important indicator of various physical phenomena of geotechnical importance. The propagation of cracks induces loss of bearing capacity and slope instability and interferes with the functionality of the buried utility systems. In this study, an attempt is made to study the crack patterns of the virgin and the treated expansive soil; to understand the difference in the development patterns and their relation to macroscale properties. In this study, 0.5, 1.5, 3% Lignosulphonate and 2, 4% Lime were used as the chemical stabilizers. The additives amended soil samples for crack tests were laid on frictionless plates in circular shapes with the soil thickness of 3 mm and left to air dry at a constant temperature of 28 °C. The crack patterns were analyzed through digital image analysis techniques and the crack parameters such as the crack length, crack width, crack intersections, crack segments and crack intensity factor were analyzed. The treated soil depicts a variation in the propagation and direction of intersection of cracks. These analyses were interpreted with the fabric orientation and arrangement of the soil samples. The analyses of the crack pattern could help in understanding the macroscale behaviour of treated and untreated soil and many other related geotechnical phenomena.

The equipment used for soil excavation is subjected to the phenomenon of clogging. Clogging is the process of adhering soil to the surface of the equipment. This can lead to certain economic as well as technical issues to soil drilling activities. In this paper, a semi-empirical and physical stimulation approach is adopted to determine the clogging potential of Thonnakkal soil. The analysis was done with the help of the Atterberg limit test and a drilling equipment developed in the laboratory. In order to analyse the influence of swelling clay on clogging potential, soil mixtures were prepared by combining bentonite and Thonnakkal soil at different percentages and tests were performed. The drilling equipment was used to study the effect of penetration rate on the clogging potential. The changes in clogging potential at different water contents were also assessed.

A significant portion of the earth surface is subjected to arid and semi-arid climatic conditions as a result of which many soils encountered in engineering practise are classified as an unsaturated soil. An unsaturated soil exists between the ground surface and natural water table. The type of soil frequently undergoes wetting and drying process due to seasonal variations. Due to this process, expansive soil may undergo swelling-shrinkage process. Considering the similarity between wetting–drying and freezing–thawing process, this study was an attempt to analyse the effect of the freezing–thawing process on unconfined compressive strength (UCS) of expansive soil. For the experimental study, samples were moulded to achieve full compaction and field compaction (100, 95 and 85% of Proctor density) for different degree of saturation (60, 40 and 20% of optimum moisture content). The moulded samples were passed through required no. of the freezing–thawing cycles (0, 1, 3 and 5 nos.) and then tested for their UCS, respectively. Results showed the effect of the freezing–thawing cycles for different compaction energy on UCS of expansive soil. It was observed that the UCS value increases up to 3 cycles and then decreases for the full compaction for different degree of saturation. Whilst for field compaction, the UCS value reduces with the increasing no of freezing–thawing cycles.

A standard penetration test (SPT) is one of the in-situ tests conducted for onshore and near shore soil investigation projects. SPT test data are extensively used for estimation of soil design parameters needed for geotechnical analysis. However, quality and reliability of SPT results are, very often, not satisfactory due to various reasons such as variable height of fall of hammer, inclination of driving rods, improper release of hammer resulting in partial energy transfer. A study is carried out to determine SPT hammer efficiency for different hammer operating systems being used in India. SPT hammer energy measurements were carried out at three project sites using different SPT hammer operating system. This paper summarizes ways to improve quality of SPT test results and presents the results of energy measurements made using “SPT Analyser.”

Deformation modulus (Em) is one of the most important parameters needed for the evaluation of the rock mass behaviour under loading and unloading conditions. Many empirical correlations have been developed over the years to determine this parameter from various rock mass classification systems. Although the preliminary design of various components of a Hydro-electric power project is based on the empirically obtained parameters, which are found to deviate substantially in the field quite often. The field values of the rock mass deformation modulus can be determined by more direct tests like plate load test (PLT) and Plate Jacking test. In this paper, deformation modulus (Em) of the rock mass at the dam site is obtained using various empirical correlations relevant to the site conditions. An attempt has been made to develop an empirical correlation between deformation modulus and GSI at Pare H.E.P site consisting of weak rock mass. Additionally, some critical comments pertaining to the empirical correlation developed have been made in this paper.

Plastic which is a waste after its usage can be useful for improving the ground properties. Black cotton soils which are problematic for construction can be utilized safely by stabilizing it with lime and reinforcing it with waste plastic. The present study deals with the strength behavior of stabilized swelling soil. Unconfined compression, triaxial and CBR tests have been conducted on the soil which is stabilized with 12% lime and mixing it with different (0.25, 0.5, 0.75 and 1%) proportions of plastic waste. Plastic waste used in the study is thrown plastic bottles. These plastic bottles are made into small strips and mixed with lime stabilized soil. The strength characteristics of the stabilized soil are improved enormously after mixing it with plastic waste. This method is an economical method since plastic waste which is cheap and easily available is used as a reinforcement material instead of steel stirrups, plates, geosynthetics, etc.

The bentonite–sand (B:S) mixes are mostly used as liner/barrier material in the construction of landfills. The sand is mainly obtained from the river banks. The consumption of natural sand is quite high due to its excessive usage in the construction works that leads to its scarcity. To overcome this crisis, the partial or full replacement of sand by the promising geomaterial rock quarry dust (Q) can be an economic and effective solution. In this paper, the effect of the full replacement of sand by the waste material rock quarry dust on the unconfined compressive strength (UCS) of B:S mixes at different curing period was studied. Here, the B:S and B:Q mixes were prepared at their corresponding maximum dry density (MDD) and optimum moisture content (OMC). The UCS of all the mixes was evaluated at a curing period of 0, 3, 7 and 14 days. The result indicates that the UCS of B:Q mixes is higher than the UCS of B:S mixes for different curing periods. This study investigates whether the addition of the waste tyre dust (TD) can enhance the UCS of B:S and B:Q mixes at different curing periods. The TD content ranging from 2 to 16% by weight was used as an additive in various B:S and B:Q mixes. The highest UCS value was observed at TD = 14% for both the B:S and B:Q mixes. The UCS of the mixes increased with the increase in the curing period. The failure strain was found to increase with the increase in the tyre dust content in the mixes.

Analysis of time dependent behavior of clayey soils in vertical consolidation is carried out by plotting the experimental settlement, δ, with its differential (with respect to experimental time, t) dδ/dt. This is called the settlement versus rate of settlement (SRS) approach. A fastest rapid loading method is suggested that gives the coefficient of consolidation, cv values very close to true cv and also shows how near the calculated, and true cv values are by fuzzy logic. The merits and demerits are compared with popular methods. The SRS methods work even when the settlement-time-pressure data at the beginning of load increment is not known. The simple procedure for quantitative isolation of secondary consolidation and creep (from primary consolidation) is suggested. Six phases of consolidation are quantitatively identified instead of three (initial, primary, and secondary). Terzaghi’s one-dimensional consolidation equation is resolved in three parts; (1) parabolic 0–40%U, (2) transition 40–60%U, and (3) exponential 60–100%U, where U is the degree of consolidation. It is shown that the SRS plot is a very powerful and useful tool for consolidation analysis.

The concept of dispersive soils is particularly significant with reference to earthen dams, embankment, canals, etc. The comparatively less explored role of surface chemistry in understanding dispersive phenomenon leads to a state of doubt and confusions among various researchers. Dispersive soils are those with unique properties which under certain conditions deflocculates and are rapidly eroded and carried away by water flow. These soils are highly prone to erosion often leading to tunnel and gully erosion. Dispersive clays have an imbalance in the electrochemical forces between particles. This imbalance causes the minute soil particles in a dispersive clay to be repulsed rather than attracted to one another. Using dispersive clay soils in hydraulic structures, embankment dams, or other structures such as roadway embankments can cause serious engineering problems if these soils are not identified and used appropriately. The tendency for dispersive erosion in a given soil depends on variables such as mineralogy and chemistry of the clay, as well as dissolved salts in the water in soil pores and in the eroding water. The presence of exchangeable sodium is a main contributing chemical factor to dispersive clay behavior. The laboratory tests generally performed to identify dispersive clays are the crumb test, double hydrometer test, pinhole test, test of dissolved salts in the pore water, and the sodium absorption ratio (SAR). The extracted soil pore water is tested using routine chemical tests to determine the amounts of the main dissolved cations; calcium, magnesium, sodium, and potassium, in terms of milliequivalents per liter (mEq/L). The percent sodium and TDS (sum of the four metallic cations) are determined. This article discussed the characterization and identification of dispersive soils based on chemical methods. The mineralogical characterization of soils were also studied using X-ray diffraction (XRD). The soil samples from different projects were compared for dispersive behavior based on slandered tests. The results show that soils with higher concentration of exchangeable sodium and presence of typical clay mineralogy are responsible for dispersive behavior.

This paper presents study of the soft to very soft marine clay deposit, very thick and having challenging geotechnical engineering properties for a road embankment over it. These include a very low shear strength, high compressibility, low permeability, sensitivity, etc. It is the Maliya marine clay deposit in tidal swamp at Little Rann of Kachchh, an extremely flat coastal alluvium plain. This clay deposit is of 6.5 km width and up to 15 m thickness. Its engineering properties are determined through the elaborate laboratory testing program comprising of consolidated undrained CU circular direct shear box tests, vane shear tests, consolidation tests, and unconfined compression tests—all these tests on the undisturbed samples obtained at every 1.5 m from the bore-hole by the author up to 12 m depth. The field investigation consists of undisturbed sampling. The results of all these tests are presented in this paper for shear strength, strength versus strain characteristics, sensitivity, compressibility, and consolidation characteristics cv. The soil is mostly of CH group. Field moisture content exceeds liquid limit [60–70%]. Liquidity Index is compared. The values of the ratio of undrained shear strength to effective overburden pressure SU/p versus plasticity index Ip are determined and discussed. The top portion of this deposit, up to 2.4 m depth, is relatively stiff. Using ϕ = 0 analysis, stability analysis of a typical road embankment having 12 m top width and 7.5 m height and with berms and vertical sand drains is done incorporating the strength at 3% strain for the compacted embankment.

Estimation of settlement is a very significant part in the design of foundations. Standard penetration test (SPT) is a commonly adopted method of geotechnical investigations. However, variability of in situ conditions is the most challenging aspect of analysis and design based on settlements. Two methods are considered to estimate the settlements of shallow foundations. One is based on variation of SPT N values with depth and the other is based on tip resistance, qc which could be highly variable is further converted to SPT N based on mean or average particle size of the soil stratum. Settlements are estimated for three different sizes of footings in both the methods for a site explored by a large number of boreholes. The variability in the estimation of settlements for a given site conditions is determined. Relative advantages and limitations of the two methods of estimation of settlements are listed and presented.

Fly ash is a by-product of coal-based thermal power plants. Utilization of fly ash in geotechnical projects may provide a sustainable solution for its efficient disposal. In this regard, bearing capacity of fly ash deposits is of paramount importance for satisfactory performance of foundations built on these deposits. Fly ash deposits used for filling up of low-lying areas are often under unsaturated or partially saturated state, and therefore, incorporation of suction stress induced in fly ash due to the presence of matric suction becomes essential while estimating its bearing capacity. In this regard, unsaturated shear strength may be quantified using water retention characteristic curve (WRCC) fitting parameters. However, determination of WRCC parameters often involves various uncertainties arising mostly due to the limited number of test data, inherent limitation of measurement range of suction measuring instruments, etc. Furthermore, very limited studies are available in literature to address the problem of seismic bearing capacity of fly ash deposits under unsaturated framework. In the present study, probabilistic-based approach has been adopted to obtain the seismic bearing capacity of footing placed on fly ash deposit, incorporating the uncertainty of the random input parameters, by adopting a factorial design approach. Sensitivity of random variables, such as infiltration rate ratio (q/ks), WRCC fitting parameters of the fly ash and horizontal seismic acceleration coefficient (kh) on the seismic bearing capacity, is presented. A prediction model has also been developed considering variation of random input parameters.

Usually geosynthetic reinforcement in reinforced foundation beds is aligned in horizontal layers, but transversal to the application of gravity stresses to restrain the tensile strains developed in the soil through interfacial bond resistance limited by its tensile strength. Geosynthetic soil structures can accommodate large deformations before failure. Subgrade soil generally exhibits nonlinear behavior at large deformations. Present work analyzes nonlinear response of cohesive non-swelling (CNS) soil bed reinforced with geotextile reinforcement placed inclined from the edge of the footing toward the free end at an inclination varying between 0° and 20° and evaluated normalized bearing capacity values and compared with horizontally placed geotextile reinforcement considering kinematics and nonlinearity of soil bed. The variation of normalized bearing capacity with the angle of shearing resistance of soil, interface friction angle, stiffness of soil bed, relative fill stiffness factor, and transverse displacement is studied in addition to the effect of inclination of reinforcement. Improvement in normalized bearing capacity ratios with inclined reinforcement considering nonlinear soil bed is significant over and above the effect of transverse resistance of horizontal reinforcement.

This study explains the pull-out resistance of belled anchor pile under vertical tension, by using 1-g panel of belled anchor pile (2D) possessing embedment ratios (L/Wb) of 3–5, thickness ratios (Ws/Wb) of 0.28–0.46 and bell angles (α) of 45°–72° in dyed and non-dyed homogeneous dry sand deposit. Under vertical pull, the applied stresses are acting along the vertical plane of the panel, and so symmetrical nonlinear slip surfaces are formed in both the sides of each panel. To predict pull-out resistances, the slip surfaces are interpreted as 3D axisymmetric failure wedges surrounding the anchor models of same scale. The predicted pull-out resistance of each model is the combination of mobilised frictional shear and dead-weight of sand wedge. The values of pull-out resistance are within the range of 22.88–383.70 N. The pull-out resistances are increased with higher L/Db, lesser Ds/Db and α of anchor models based on variation in the horizontal extent of failure points in slip surfaces. The ratios of mobilised frictional shear to pull-out resistance (× 100, %) of anchors are within the range of 13.50 to 30.81%, and these values are decreased due to higher L/Db and increased due to higher Ds/Db and α. The ratios of dead-weight of sand wedge to pull-out resistance of anchors (× 100, %) are within the range of 69.20–86.50%, and these values are increased due to higher L/Db and decreased due to higher Ds/Db and α.

Foundations of certain structures are subjected to large moments and relatively small vertical and horizontal forces. Moments on the foundation base are mainly caused by horizontal forces acting on the structure. It tends to tilt the footing. This tilt increases with the increase of load eccentricity, and consequently the bearing capacity is reduced. Short bored pile or pier foundations are widely used in situations where moment-carrying capacity is the dominant design requirement. But such foundations are very costly, and it cannot be adopted for small structures. Published literature on the moment-deformation behaviour of shallow foundation is very scarce. This paper investigates the influence of moment acting on the structure, on the settlement and angular distortion of the footing by carrying out a series of laboratory scale load tests on model circular footing in clayey soil. The parameters varied are magnitude of moment, magnitude of vertical load, depth of foundation, etc. Finite element analyses are also carried out, and the results are compared with those obtained from laboratory studies for validation. It is observed that tilt increases with increase in moment initially and thereafter decreases. It is also observed that tilt decreases with increase in depth of footing. Moment acting on the structure influences the load-settlement behaviour, and also, load-settlement behaviour improves due to the addition of reinforced foundation bed below the footing.

The bearing capacity of foundations has always been one of the subjects of major interest in soil mechanics and foundation engineering. Evaluations of bearing capacity of vertically loaded shallow foundations on various soils have been studied by many researchers. There are structures where horizontal loading has greater influence, and much research has not been carried out to evaluate the horizontal load bearing capacity of shallow foundations. In this paper, extensive investigations are carried out to study the load-settlement behaviour of circular footing subjected to horizontal loads (H). The reduction in lateral compression of soil by providing micropiles beneath the footing is also studied. The research involved nonlinear finite element analyses using the FE software PLAXIS 2D, and the results were compared with those obtained from laboratory scale load tests. The parameters studied are influence of vertical load (P), embedment depth (D) on lateral displacement of footing and effect of combined lateral and vertical load on rotation of footing. It is observed that depth of foundation and vertical load influences the lateral load bearing capacity of footings. It is observed that the lateral deformation decreases with the increase in depth of foundation and vertical load. The rotation of the footing is also found to decrease with depth when the footing is subjected to combined lateral and vertical loading. Lateral compression of soil and rotation of footing can be reduced further by providing micropiles beneath the footing.

Construction of a 107-m (351 ft.)-high Shiva statue on a hillock at Nathdwara, Rajasthan, posed several challenges, both geotechnical and structural. Detailed geotechnical investigation showed the presence of quartzite rock from the ground surface that is highly fractured at shallow depths and improves in quality with increasing depth. Rock anchors were provided for stability against wind and earthquake loading. The slopes in the surrounding areas were stabilised effectively by suitable measures. The structure details and other aspects of the elegant monument are described.

Ground improvement is a must in present world where there is lack of land available for construction. Soil improvement can be done in various ways to increase the strength of soil. Soil reinforcement is one of the techniques available to enhance the quality of soil. Various tested techniques are available for this purpose. In this study, bamboo grids have been applied in horizontal layers like geo grids in a test tank to study the increase in bearing capacity under vertical loading. Easy availability, low cost, strong tensile strength, and environment friendly behavior are some of the reasons for selecting it. The study is conducted on a steel test tank with locally available Zone III sand. Load tests are conducted on a model circular footing with 0.18 m diameter (B) resting on sand with and without bamboo grids to compare the improvement factor for bearing capacity. The reinforcements are inserted in bed of sand with varying depths (B, 0.25B, 0.5B, B 1.5B) and in single and multiple layers. Depth to diameter ratio, number of grid layers, and shape of the aperture plays an important role in performance of model circular footing. At first, model circular footing without bamboo grid is tested, and experimental results are compared with various analytical equations available viz Terzaghi (1943), Meyerhof (1963), Hansen (1957, 1970), Vesic (1973), IS: 6403-1981 code. The proximity in the experimental results with Terzaghi establishes the reliability of the test setup. The models are tried with PLAXIS 2D® also.

The present investigation determines the ultimate bearing capacity of a surface strip footing resting on a reinforced embankment. The analysis is performed using the upper bound limit analysis, along with a multi-block failure mechanism. In this study, two factors named the increment factor (Ef), and the influence factor (Rf) are introduced to determine the effect of reinforcement and embankment slope on the bearing capacity, respectively. The influence of setback distance (SL), slope angle (β), cohesion (c), angle of internal friction (ϕ) of soil, and reinforcement depth (Sv) on the magnitude of Ef and Rf is explored. Soil is assumed to follow the Mohr–Coulomb failure criterion along with the associated flow rule. While determining the influence of the reinforcement on the bearing capacity, the reinforcement is assumed to be a strong one, i.e., the tensile strength is much higher than the force induced in the reinforcement. It can be conceived that the magnitude of Rf greatly depends on c, ϕ, SL, and Sv.

In the conventional design of a piled raft foundation, piles of uniform lengths are provided underneath the raft. However, it has been observed that in such cases, the peripheral piles either carry more loads as compared to central pile for a rigid raft, or central pile undergo more settlements than peripheral piles for a flexible raft. This paper attempts to evaluate the required length of the piles in the group for an optimum design of piled raft foundation founded on soft clay. Three-dimensional (3D) Finite Element (FE) models having different configurations of pile lengths and pile spacing were analyzed numerically using a general purpose finite element method (FEM)-based software ABAQUS. Mohr–Coulomb model is used to define the elasto-plastic soil behavior. 3 × 3 squared concrete piled raft foundations were designed with three different lengths of the piles used for the center pile, corner piles and edge piles for models with non-uniform pile lengths. The overall behavior of the piled raft foundation system is evaluated. The results have shown that the model having longest pile at center, intermediate length of piles at edges and shortest piles at the corners has the highest improvement in load-carrying capacity and maximum reduction in average and differential settlements when compared to the conventional piled raft foundation design.

Piled-raft foundation is a concept, which has received increasing recognition in recent years. Due to the complexity of piled-raft system, an accurate design relies on numerical modeling. This study is directed to developing a numerical model to analyze and identify the influence of parameters governing its performance. The developed model was based on the finite element technique and accounts for the interactions of pile-to-pile, pile-to-raft, raft-to-soil, and pile-to-soil. The results produced by the present model were validated with the available data in the literature. The analysis in the present study of decomposed components of raft and piles of piled-raft foundation embedded in sands includes the interaction effects. For this purpose, finite element analysis was performed using PLAXIS 3D for various foundation and soil conditions. A square raft was used to model the piled-raft. The developed model has been used to conduct a sensitivity analysis of the governing parameters that include pile length, pile spacing, and raft thickness. Furthermore, the effects of variations of soil modulus of elasticity, friction angle, dilatancy angle, and unit weight have also been examined. From decomposed load–settlement curves obtained from the analysis, the load-carrying capacity of piles is mobilized earlier than that of the raft, showing higher load-carrying proportion. As settlement further increases, raft tends to carry greater load than the piles. Due to the interactions between raft and piles, the load-carrying capacities of the decomposed components are smaller than those of the unpiled raft and pile group of the same configuration. As pile spacing increases, the load proportion of piles becomes higher.

Pile foundation is often used to transfer heavy loads deep into the soil. Pile derives its resistance from both shaft and base in case of axial loading. The pile-soil response is nonlinear and difficult to predict. Pile load tests are conducted on test piles, and the load–displacement response obtained is used to validate or modify the design. This study proposes a simple method to estimate the initial stiffnesses and the ultimate resistances of the shaft and the base of a pile from initial pile load test results assuming nonlinear hyperbolic responses of shaft and base. This new method would help designers to validate the design correlations and predict the pile responses better.

Pile foundation of engineering structures, such as bridges, offshore structures, and retaining walls, is frequently subjected to eccentric loads. Many deep foundation structures experience excessive settlement if subjected to eccentric loads. Several researchers have analyzed the problem and studied the behavior of deep foundation structures analytically. The main aim of this project report deals with the bearing capacity of single pile under vertical eccentric load in cohesion less soils. The purpose of the thesis is to study the load–displacement response of single pile [8] installed in soil bed when subjected to vertical eccentric loading for 60% and 70% relative densities [1, 2]. Single pile was fabricated with diameter 42 mm, 49 mm, 75 mm, and 100 mm for constant length of 500 mm. Tests were conducted using manual loading with four number of dial gauges. Most of the studies relate to the case of a vertical load applied centrally to the foundation. Simplified calculation approach for settlement of single pile is studied [6].However, when loads are applied axially and eccentrically to the foundation, the bearing capacity is different from centrally loaded pile model. Ultimate bearing capacity has been found out for central as well as eccentric loading conditions. This paper aims to investigate the response of the pile subjected to eccentric load and comparative results of the effect of diameter, the effect of relative densities, and the effect of eccentricity.

Pile is a structural element constructed to overcome heavy loads from superstructure, when proper bearing strata is not available at shallow depth. In Kerala, the low land and marine areas consist of soft clay, laterite, and sandy soils. These soils have low bearing capacity and shear strength, causing excessive settlement, and can lead to failure of structures. The prediction of bearing capacity of a bored cast in-situ pile is a complex problem, as it depends on installation method, concrete quality, ground condition, and pile geometry. It is considered that the reliable method for finding bearing capacity is pile load test, which is time consuming and costly. The bearing capacity can also be analyzed by empirical and analytical methods using soil data and SPT data. In this paper, the IS code method, α-method, β-method, and four SPT methods have been employed and summarized for comparison. Seven interpretation methods are used to interpret the failure load, and a suitable failure criterion has been determined. A database of 15 bored piles is collected from different sites in Kerala. The above chosen SPT methods are calibrated by the trial and error to propose a new formula. The Log-Normal approach is employed to all methods, and the distribution graph shows that the proposed formula predicts results with more accuracy and less scatter than other methods.

Borehole stability is a major problem to be resolved in all the piling sites. Support fluids play a major role in stabilizing the pile boreholes. Among the various support fluids commercially available for stabilizing boreholes, bentonite support fluid is commonly used in almost all piling sites. A study on the effect of these bentonite fluids at pile–soil interface will be highly beneficial for engineers. In this paper, an attempt is made to study the effect of bentonite layer on frictional resistance at pile–soil interface and how it affects the estimation of pile capacity. The behaviour of bentonite fluid in various types of soils was also studied.

Deep foundations are conventionally being adopted in construction of various structures ranging from bridges to skyscrapers. Bored cast-in-situ piles and drilled shafts have become a common choice of deep foundations, especially in urban areas, owing to the relatively minimal construction associated noise and vibration as opposed to driven pile. However, one of the major shortcomings of bored piles is the lower skin and tip resistances due to the installation effects (stress relief). In the current practice, empirical or semi-empirical correlations are generally adopted for estimating the unit skin friction of bored pile/drilled shafts which is not necessarily taking into account the actual soil state around pile subsequent to the installation. Since the soil state (properties and stresses) in the vicinity of pile will be significantly altered due to the installation processes, studying the evolution of soil state during the various construction stages as well as the loading stage will aid to estimate the residual confining stress and thus the unit skin resistance of pile. This can be made possible using cavity expansion and contraction solutions as the stress relaxation during the excavation of hole is analogous to a cylindrical cavity contraction (unloading) problem and subsequent concrete placement and axial loading resemble a cavity re-loading (i.e. expansion) problem. This paper presents a semi-analytical cylindrical cavity contraction and expansion solution procedure to predict the residual horizontal stress and consequently the skin friction of bored pile. The proposed approach was validated using two well-documented field test data of bored piles/drilled shafts in sand.

The distribution of load along the pile length is required to assess the performance of pile. Most of the studies of pile load tests are mainly aimed at overall behaviour of pile. Few tests report load transfer along the pile length under axial loading conditions. These are valuable to analyse the mobilization of shaft resistance and to estimate the load transfer mechanism during application of load. Present study analyses one such report which presents variations of axial loads with depth for few test piles. Mobilized shear stress as a function of displacement of pile is estimated for all these test piles, and a near unique shear stress–displacement relation obtained.

Coastal areas like Kochi, Nellore and Gujarat coasts have deep deposits of highly compressible clay layers. The developments of infrastructures in these areas need deep piles to support the tall and heavily loaded structures involved in the development. Such piles when they pass through such compressible layers are subjected to negative skin friction which reduces the allowable load on the piles. Under such circumstances, the only alternative is precast piles. Precast piles in a single segment have handling problem as well as installation problem. The maximum length that can be handled cannot be more than 15–18 m. Hence, the need for an effective system resulted in the advent of jointed piles. Although jointed piles are used extensively, published data on its performance under various types of loading and joint positions is very limited. This paper discusses the main features of design, performances of precast jointed piles under axial, lateral and combined load conditions. A parametric study was carried out by varying the pile joint location under four typical conditions. Load settlement response and the behavior of stress around the joint have been evaluated. An attempt was made to study the response of the jointed pile subjected to lateral soil movement due to excavation by two-dimensional analysis. ABAQUS 6.14 and PLAXIS 2D have been used for the analysis in this study.

Piles are deep foundations of relatively small diameter shaft, introduced into the soil by suitable means, to support the load coming on it from the superstructure when a good bearing stratum is not available near the ground surface. This study attempts an optimized design approach for single piles in order to evaluate the pile geometry, based on the ultimate bearing capacity of the pile within stipulated limits. A standalone software code has been developed as a result of this study. The code is written in MATLAB that incorporates genetic algorithm (GA) optimization technique to obtain optimum pile dimensions depending upon supporting soil condition and incoming loads. The pile is then designed satisfying all the structural requirements as per Indian Standards Code for Reinforced Concrete cast-in-situ pile, IS: 2911. The optimization and design procedure are demonstrated through the proposed software, and the results are verified manually. The optimum pile dimensions, reinforcement details and an estimate of the design are presented as the software output.

The presence of pile in natural or man-made slope is a common scenario. The effect of the active pile in a stable slope becomes void when it is moved away to a maximum distance of 5R (R-relative stiffness factor) from the crest of the slope towards the embankment under lateral load. In this paper, a numerical study is made to understand the development of stress zones around the pile when it is kept in a soil slope of 1 V:3H; the shear strength is maintained as 30 kPa. A prescribed displacement (5 mm) is applied at the pile head and the lateral load corresponding to it at varied position from the slope crest towards the embankment is studied. The slope effect becomes zero when the lateral load capacity of a single pile at a varied position from the slope crest is equal to the lateral load at horizontal ground. Until zero slope effect, the pile is moved, and the stress zone formed around the pile is studied.

This paper presents a critical review of some important aspects of the geotechnical design of bored piles with a view to evaluate the relevant provisions of Indian codes of practice in the context of international best practices. The following aspects are reviewed—critical depth concept of limiting skin and end bearing resistance, coefficient of earth pressure, minimum embedment into bearing stratum and reduction in end bearing resistance due to the presence of weak layers below the pile tip. It is shown that arguments against the validity of critical depth concepts seem to have gained more acceptance, and the international practice is moving away from the concept of limiting the skin and end bearing resistance on account of critical depth. Values of coefficient of earth pressure for bored piles recommended by Indian codes appear to be appreciably higher than those used internationally. The minimum embedment of two times the pile diameter into the bearing stratum for piles installed through weak strata and terminated in a competent bearing stratum recommended by IS 2911 looks reasonable. The presence of a weak stratum below the pile tip could have an effect on the end bearing resistance of piles. The limitations of the Indian codes with respect to this issue are highlighted, and recommendations from various sources are discussed. The implications of the above aspects for design are discussed, and suggestions for updating the Indian codes of practice are presented.

Multistoried buildings are subjected to a significant amount of lateral forces due to winds and earthquakes in onshore structures and forces due to water currents and heavy winds in offshore structures. Foundations supporting such structures as offshore wind turbines should resist extensive lateral forces and pullout forces. To sustain these loads, innovative types of pile foundations need to have experimented with in place of regular pile foundations for more economic and efficient performance. In this paper, an attempt is made to demonstrate the efficiency of adopting finned-piles concerning previous literature studies. This work highlights some of the experimental investigations, model studies, and numerical studies (FEM, FDM) adopted to find the usefulness of finned-piles in resisting the lateral loads. Some of the key-points of adopting such foundations are discussed. Finally, future untapped avenues explored on finned piles are also brought out in the paper.

Short bored cast-in-situ piles were installed for a solar power plant in western Rajasthan. The deposits at site consist of dune sand underlain by rock. The paper discusses the load–displacement behavior of 350 mm diameter 2.65–2.8 m long piles under pullout and lateral loading. To evaluate ultimate pullout capacity of piles which were not tested to failure, a hyperbolic model of load–displacement curve has been proposed. The pullout test data has been used to back-calculate the value of earth pressure coefficient, k. The lateral pile capacity has also been analyzed to evaluate the value of modulus of horizontal subgrade reaction.

This paper presents the results of experimental investigations of barrette foundations of various shapes, viz, rectangular, T-shape, cruciform shape and H-shape resting in sand and subjected to vertical and lateral loading. Model pile load tests were conducted in a laboratory setup and ultimate vertical and lateral capacities of the piles were determined. The results show that Barrettes have much higher ultimate vertical and lateral capacities as compared to that of a circular pile of same c/s area. The shape of barrette influences the ultimate vertical and lateral loading capacity of the pile.

Anchors have been developed for various purposes such as strengthening the slopes, retaining walls, stability of tunnels, and stability of foundations. There are many types of anchors depending on the type of load, type of structure, and local subsoil conditions. The behavior of anchors in the field indicates that the collapse mechanism and bearing capacity of the anchor can be determined by many factors. Most studies focus on massive models shaped anchor plates with various shapes (Helical, square) with a variation of the dimensions, depth, and type of load. In the present investigations, the uplift capacity of helical and square plate anchor resting in cohesionless soil deposit with different plate configurations was determined experimentally. Different types of anchor model were cast for experimental study, where mainly the number of plates, the depth of upper- and lowermost plates, and the ratio of spacing between the plates to the diameter of the plates were varied, and ultimate uplift and lateral capacity of each anchor was determined. In experimental investigation the uplift and lateral load carrying capacity of square and helical plate anchors are found to be increased with increase in embedment depth and spacing between the plates. In the present study the helical plate anchor system is more efficient than square plate anchor system as they are providing more uplift and lateral load-carrying capacity.

Helical piles have been used in construction applications for more than 150 years. Helical piles have gained in popularity that they are more frequently used for deep foundation types in geotechnical areas. In this paper, the results of numerical analysis of the helical pile are presented. For analytical study, a three-dimensional full-scaled finite element model was created by using finite element software MIDAS GTS NX. Results obtained were compared with the conventional hollow pile. The various parameters considered for the study were as follows: type of loading, number of Helix, Helix spacing and Helix diameter. The provision of such helices provides an ideal anchorage system due to the significant locking-up effect of the soil within the helices, resulting in increased pile capacity.

Nowadays in most high-rise buildings, the combination of both piles and raft are used since only raft cannot satisfy design requirements. So, by addition of piles with raft load carrying capacity also increase sand also reduces settlement. Piled Raft foundations have been considered as one of the most economical foundation systems and are widely used to support high-rise structures. In the present study, 3D finite-difference analysis was performed on Piled Raft foundation using FLAC3D software. In this mostly sandy soil is taken in two different layers (different Young’s modulus). Here, the analysis is done on both Pile Group and Piled Raft. In Pile Group, the pile cap is not in contact with the ground surface. In Piled Raft, raft top surface level is in the same level with the ground surface level. Also, load had been applied in two ways concentrated load at the center of the pile cap/raft and uniformly distributed load over the pile cap/raft. The effect of varying Pile cap/raft thickness has been considered in the paper. The diameter of pile is taken as 800 mm. The pile length taken is 35 m. The different load is applied to the different group of piles according to their safe bearing capacity. The result shows that as pile cap/raft thickness increases then the differential settlement decreases. By increasing pile cap/raft thickness, the maximum bending moment and maximum shear force increases. Result is also affected by different methods of loading. Differential settlement is less in case of uniformly distributed load compared to concentrated load at the center.

Structures such as transmission towers, high-rise buildings, offshore structures and suspension bridges are subjected to uplift, compressive forces and overturning moment due to wind or waves. Helical pile is a popular foundation choice in many countries and used to resist uplift, compressive forces and overturning moment. Helical piles are easy to instal without generating the spoils and can take load immediately after the installation that offers the cost-reducing alternative methods to reinforced concrete grouted anchors and driven piles. In this paper, to study the behaviour of helical pile in sand, laboratory tests are conducted on small-scale model piles of mild steel by varying the loading conditions and helical blade diameter. Results obtained from the tests are compared with conventional hollow pile. The length of pile, relative density, type of soil and pitch distance are kept constant during investigation. The provision of such helices may provide an ideal anchorage system because of the significant locking up effect of the soils within the helices, resulting in increased pile capacity.

A conventional vertical static load test on a pile provides limited information as only pile top load and displacement is monitored. Such testing does not provide any quantitative information on the load-transfer mechanism (i.e., magnitude of the toe resistance and the distribution of shaft resistance). Similarly, conventional lateral load test only provides the load–deflection curve for the top of the pile and pile deflection along the length as well as point of fixity is unknown. Yet, this information is what the consultant often needs in order to verify his design. Therefore, more and more frequently, the conventional test arrangement is expanded to include instrumentation to obtain the required information. This paper presents a case study for the instrumented tests performed in Kochi for a Test pile at Kochi Metro Rail Project. Geo Dynamics in association with Kochi Metro Rail Corporation (KMRL) performed state-of-the-art instrumentation studies during vertical as well as lateral load tests. Embedment type strain gages were installed in the pile during pile casting to perform instrumentation study. An inclinometer casing was also installed in order to monitor the deflection of pile along the length during lateral load test. The pile was a test pile (mono pile) with diameter of 2 m and length of 50 m. A crosshole sonic logging (CSL) test was also performed before the load tests for assessment of pile integrity.

Barrettes are common foundations for high-rise buildings, especially because of their high bearing capacity, vertical as well as lateral loads. Recently, barrettes have been demonstrated to be more useful for small plots receiving highly concentrated building loads with limited space between foundations. The idea of a single barrette that can replace a group of conventional piles results in a more stable, economical, and reliable foundation system. Bidirectional static load test (BDSLT), a modern full-scale proofing load test method, carried out using hydraulically driven, purpose-built, calibrated, sacrificial loading jacks installed within the foundation unit. This paper articulates the results of three barrette tests of 2.80 m × 1.20 m size of a 300 m high-rise Residential Tower in Business Bay, Dubai, UAE. The main objective of this load test was to proof-load the test barrettes over 180,000 kN (18000 tonnes). For this purpose, 9 × 900 tonnes of bidirectional capacity hydraulic jacks and eight levels of Geokon vibrating wire concrete embedment type strain gauges comprising four units at each level were utilized. The settlement results of a 47 m deep barrette indicate a total settlement of 6.5 mm at the working load of 54,000 kN that is in good agreement with the 6.20 mm induced from the bidirectional static load tests. The interpretation of the load test results pooled with finite element analyses aided optimization of the barrette capacities maintaining a sufficient factor of safety. The barrette total capacity was evaluated based on the load test results and interpretation of deformation, load distribution, induced unit skin friction, and up to 11% reduction of the current length was proposed.

Composite piles have been used generally for waterfront barriers, fender piles and bearing piles for light structures. Fibre-reinforced polymer (FRP) composite as a pile material can eliminate deterioration problems of conventional piling materials when exposed to harsh or marine aggressive environments. FRP composite piles are composed of a hollow FRP pipe that is filled before installation with an expanding concrete and is coated with a durable corrosion-resistant coating layer. However, researchers studies related to the use of FRP materials as pile are very limited. This paper presents the results of study related with the performance of fibre-reinforced polymer pile foundation resting in marine layered soil of Chennai port trust (India), with respect to its various parameters. For this purpose, analytical model of FRP pile was developed in MIDAS GTS NX software to simulate the pile foundation with different parameters studied. A defined soil model represents marine layered bed and pile embedded within it with varying slenderness ratio and subjected to vertical, uplift and lateral loading. Performance of pile group, with different number of piles in the group, was also analysed. FRP pile materials investigated were glass fibre-reinforced polymer (GFRP) and carbon fibre-reinforced polymer (CFRP), and the results were compared to the conventional concrete pile. The results show that the ultimate load capacity of FRP pile is higher than that of conventional concrete pile. Also, increasing the slenderness ratio increases the ultimate load capacity of pile.

Ancient and historical structures have always impressed the current generations. Especially, a few of these structures are not only visually attractive but are extremely stable owing to the kind of architecture and materials used in building them. The objective of the present study is to understand the engineering performance of Thanjavur Brihadeeswarar temple Garphagriha tower foundation for Static load conditions. This temple was constructed by the great Raja Raja Cholan who ruled Tamil Nadu in the period 1010 CE with help of Architect Kunjalamallan. The entire structure is made of the granites by using buzzle technology which means force applied at the top to prevent the movement of rock without any binder. Based on the discussion with an archaeologist who worked in Thanjavur Brihadeeswarar temple, it is understood that the Thanjavur temple Garbhagriha tower foundation is resting on sandbox (cushion type). Sandbox is a technique of filling sand mixture in relatively dense conditions within a rigid boundary. Generally, the temple foundation is designed for zero settlement. The study deals with numerical analysis for static load condition of temple tower foundation in sandbox. To determine the size of the foundation for zero settlement criteria, the thickness and depth of boundary are varied. Through static load analysis, engineering performance (settlement and vertical stress distribution variations) of the temple is evaluated.

Silos were constructed in the early 1970s in most parts of Canada on soft deposits by farmers with no or little technical assistance. The majority of these silos constructed on weak compressible deposits have overturned/tilted, and some even collapsed due to inadequate or insufficient bearing capacity and/or differential settlement and tilting. Bozozuk [1, 2] documented some of these failures and analysed the same based on the available theory of bearing capacity of foundations on homogeneous ground. The current study reassess two cases based on current and recent theories of bearing capacity of foundations on normally consolidated ground (strength increasing with depth, Davis and Booker [4]) with desiccated layer over it. A simple theory for bearing capacity of foundations on desiccated layer overlying a normally consolidated soil with undrained strength increasing linearly with depth is developed as an extension of Meyerhof’s theory for two-layered soil. The stability of the silos is reassessed based on the proposed approach.