Proceedings of the Indian Geotechnical Conference 2019

Good quality of subgrade soil is required to maintain the standards in the field of highway construction. Sometimes, the available soil may not satisfy the desired standards, therefore, it is required to improve the soil properties through various methods. Mechanical and chemical stabilization methods are mostly useful for the stabilization of subgrade soils. In this study, subgrade soil is considered as clay soil, coconut fibers and micro fine cement are used to stabilize it. Micro fine cement is blast furnace slag-based cement and Portland-based cement intended for grouting applications. Portland-based micro fine cement is used, which helps in improving the stiffness of paving materials, particularly those which include silt or clayey soils in the subgrade or base layer. Micro fine cement grout possesses high strength, durability, better flow properties and bleed characteristics than Ordinary Portland cement. Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests are carried out to assess the strength and penetration characteristics for different combination of clay soil with coconut fibers and micro fine cement. Coconut fibers are added to the soil at different percentages from 0.5 (0.5) 2 considering aspect ratios 30, 50, 70 and 90. The study is extended with the addition of 1% micro fine cement to the coconut fiber and soil mixture.

In this study, finite element analyses are carried out using PLAXIS 3D software for realistic prediction of stress and deformation in granular sub-base layer of an unreinforced section as well as section reinforced with Geocell. The behavior of sub-base and subgrade soil has been simulated using linear elastic model and Mohr–Coulomb yield criterion, respectively. Geocell has been simulated as plate material and tyre pressure has been simulated using loading on circular plate. Slow cyclic testing in various stages has been performed with varying loads to study the resilient behavior of reinforced and unreinforced granular layers and the Modulus Improvement Factor (MIF) is determined due to the Geocell inclusion. The finite element model has been validated with the field test results of load and deformation conducted on trial sections built near Dandeli Reserve forest in Karnataka state highway No. 6 (Saride et al. 2016). This model has also been used to study the effect of Geocell reinforcement in the pavement sections given by IRC 37-2018 in their design catalogue. It has been observed that the MIF values obtained by introducing the Geocell as a reinforcement in the base layer comes down when compared with various field studies and laboratory studies due to the restriction of minimum thickness of base layer to be maintained as per IRC guidelines.

The behavior of stabilized subgrade soil subjected to cyclic Wetting and Drying (W–D) in the region, where temperature and climatic variations are significant like Rajasthan (temperature rises up to 50 °C), is essential for understanding its long-term durability. In the present study, effect of cyclic W–D on the strength behavior of lime treated black cotton soil cured up to 28 days has been investigated. The objectives have been achieved by performing the detailed characterization of materials used and by investigating the Unconfined Compressive Strength (UCS) of soil treated with optimum lime content (6%). The lime treated sample cured up to 28 days has been selected by considering the fact that formation of cementitious compounds of Al-and Si-hydrates, which are mainly responsible for strength improvement, needs longer time periods. The UCS has been determined for lime treated soil cured up to 28 days without and with subjected to W–D (up to 50 °C) for one and four cycles. The results showed that the improvement in soil plasticity has been observed immediately after addition of lime. The strength of lime treated soil tested in drying state increases over the curing period and number of W–D cycles. The increase in strength can be attributed to the pozzolanic reactions which happen over time and thereby, formation of compacted matrix with formation of cementitious compound.

Transportation is the major factor in the economic, social and overall development of any country. Railways are the key to achieve such a fast track development in lesser time. Indian Railway (IR) has put itself in challenge of gaining competency and a large share of the transportation market, as was in the old days. And as these changes are happening very fast, a simultaneous development in the technology must undergo swift transformation. This paper presents application of globally tested and accepted technology of resilient mats made from recycled rubber, used in rail track foundation as Under Sleeper Pads (USP) or as Under Ballast Mats (UBM). But global standards are completely different from Indian Standards, so some modifications are necessary before application. In this paper, a standard section of rail track currently adopted by Indian Railways is compared with the section modified with the application of resilient mat. When analysed, various benefits such as improved life cycle of track, reduced maintenance cost, etc., have been seen. So this could be a game changer technology for IR to achieve goal within the approved budget and the allocated time period. Also the stability of track was seen to be improved sufficiently with the use of resilient mats to operate semi high-speed trains and higher axle loads.

Enormous quantities of waste by-products, like fly ash, red mud, granulated blast furnace slag (GBFS), silica fume and many more, are being produced every year all over the world from several industrial activities. These wastes are unloaded near the plants or in lagoons that conquering quite a lot of hectares of valuable land which may cause harm to environment. India is one of the primary producers of many industrial wastes, in which fly ash, and different slags are generating in massive amounts. Although the slags from the steel industry have acceptable quality to utilise for road works, their use on Indian roads construction is limited. The work is meant to determining the amount of corex slag by the weight of the mix that can be used in the subgrade layer/embankment of road construction. Strength properties of various soil-corex slag-lime mixes, namely compressive strength and stiffness in terms of flexure strength studied in the laboratory investigation for 7 and 28 days curing period. Also, relationships have been proposed to determine the flexural modulus of corex slag + lime stabilised expansive soil from its compressive strengths.

Resilient modulus (MR) is the critical input parameter for the characterization of pavement geo-materials subjected to repeated traffic loading. The effectiveness of a material in stabilizing soil for the subgrade layer of pavement is usually assessed by MR estimated from quasi-static tests (California bearing ratio and unconfined compression strength), but these tests are not the accurate representation of repeated traffic loading, and hence the MR must be determined through laboratory cyclic triaxial test. This review examined more than 35 research papers published over the period 1995 to 2019 and identified 15 stabilizers that have been tested for soil stabilization under cyclic triaxial loading. The analysis of these articles highlights three different categories of stabilizers: first, waste materials such as fly ash, cement kiln dust, oil shale ash ground granulated blast furnace slag, dolime, bottom ash and lignin, second, chemical stabilizers such as lime, cement, lignosulfonate, sodium alginate bio-polymer and an ionic soil stabilizer and third, fibres such as polypropylene and lignin. The soils subjected to the test were organic clay and inorganic soils such as clay, sand, gravel containing soil and black cotton soil. The present paper discusses the effect of confining stress, cyclic deviator stress, number of load applications, curing period and dosage of the stabilizer on the MR of the stabilized soils. The analyses of these articles help understand the importance of cyclic triaxial test for proper characterization of stabilized soils for use in pavement construction. The fact that only a limited number of stabilizers for the soil has been studied so far, this review identifies a scope of determining the MR of materials that are potential soil stabilizers for future research.

It is often necessitated to stabilize and reinforce the structurally unsound soil to bear the traffic load. Different types of sustainable materials are being increasingly used in highway engineering to facilitate rapid construction and to ensure better performance. In the present study a series of plate load tests were conducted on a two layered flexible pavement system (field model) consisting of a locally available sand subgrade layer of eighty cm thickness and an aggregate WBM layer of varying thickness of ten cm, fifteen cm and twenty cm, respectively. In the interface between the sand subgrade layer and the WBM layer of the pavement system, locally available coconut coir mat as geotextile reinforcement material was placed either in single layer or in double layers. These tests were conducted on the above materials with and without coconut coir mat to find the reinforcing effect imparted by coconut coir mat. The values of modulus of subgrade reaction (K), the modulus of elasticity (E) and the ultimate bearing capacity (qu) were determined from the plate load test results for all the test bed conditions Finally, for all the three different thicknesses of WBM layers the percentage change in K, E and qu values using coconut coir mat (both for single layer and double layer) with respect to the corresponding values without coconut mat was calculated and it was observed that the fifteen cm WBM layer over the subgrade with double layer coconut coir mat gives the maximum percentage variation.

Subgrade in flexible pavement is considered as the foundation of pavement structure. Improvement in subgrade stiffness in terms of California Bearing Ratio (CBR) is done by placing suitable thickness of compacted subgrade with higher CBR. Such increase in subgrade CBR reduces the total pavement thickness and increases the durability of pavement against rutting failure. Present paper deals with formulation of a methodology for determination of suitable thickness of a compacted subgrade on the top of weak natural subgrade using mechanistic-empirical design approach. In this paper, the allowable vertical stress on top of a compacted subgrade has been determined from the CBR—depth relationship corresponding to the axle load and tyre pressure developed by Yoder and Witczak. Moreover, the vertical compressive strain on the top of the natural subgrade has been determined from the rutting criteria as recommended in IRC-37:2018. The two layered system with compacted subgrade with higher CBR on weak natural subgrade with lower CBR has been transformed in this paper into a homogenous system by Odemark’s method to use the formulations of mechanistic approach. The thickness of compacted subgrade thus has been back calculated so that the layered system can withstand the design load repetitions by limiting the vertical compressive strain on the top of natural subgrade. It has been found that, appropriate thickness of compacted subgrade is necessary to achieve the specified CBR when placed over the weak natural subgrade for specified axle load repetitions. Such layer thickness significantly varies with the ratio of elastic modulus in a two layered system. In this backdrop, the concept of effective CBR as recommended in IRC:37-2018 and the provision of SP:72-2015 specification for adopting a fixed thickness of compacted subgrade in low volume rural road need to be revisited.

Highways or roads are best source/medium to connect a place to another place. Road is technically named as pavement and pavements are classified as flexible pavement and rigid pavement on basis of regional conditions [1]. Laying the flexible pavement on expansive or black cotton soil adds another challenge to engineers. If not properly laid, the pavement may fail soon. For the prevention of these failures, many researchers have contributed by performing experiments on black cotton soil added with waste materials and discussion made “How thickness of pavement gets affected by waste materials?” In this research paper, the experimental study on design of flexible pavement test results of Atterberg’s limit and California bearing test are summarized. Many researchers tried to improve the engineering properties of black cotton soil (BCS) by addition of Kota stone slurry, Recron 3s fibre, sugarcane bagasse ash, pond ash and coir fibre (CF), etc. In this research work, the flexible pavement is designed by stabilized expansive soil. The soil is stabilized by sugarcane bagasse ash, Kota stone slurry, brick dust and marble dust. The liquid limit, plastic limit, plasticity index and soaked California bearing ratio test were performed in a geotechnical laboratory.

Flexible pavements are frequently damaged with excessive cracks, settlements, and potholes due to various reasons. There are many options to maintain and repair such defects depending upon serviceability standard, funds available, and priorities for maintenance operations. Since last few decades geo-synthetic materials are introduced in market for wide range of geotechnical applications such as reinforcement, separator, drainage, gabions, etc. In this study, an attempt is made to study the effectiveness of non-woven geotextile for repair of potholes. For this, geotextile was used over a patch of the potholes to act as reinforcement and drainage overlaid by the aggregates. To check the effectiveness of the geotextile performance, cyclic plate load test was carried out in the laboratory model of 0.8 m × 0.8 m × 0.8 m tank to measure settlement. The same set of the test was also conducted by simulating potholes and repaired without geotextile layer, and then the comparison of the settlement was done to check the performance of the geotextiles. It was found that pavement with geotextile produces 45% less settlement than pavement without geotextile.

The soil in the highway material as subgrade plays an important role in the pavement component, which is an integral part of pavement. It is desirable to have the pavement with the good subgrade soil. But this is challenging in the case when the subgrade soil is expansive in nature. In order to obtain the better performance, various soil stabilizers are used to improve the subgrade soil properties. In the present study black cotton soil is used which is expansive in nature and is treated with conventional additive Lime with the dosage of (2, 4, 6, 8, 10% by weight of soil) and non conventional additive. Terrazyme with (50–250 ml/m3 of soil) with the increment of 50 ml and chemical based additive Terrasil with (0.2–1.0 kg/m3) with the increment of 0.2 kg/m3. The study aimed to identify the physical & chemical change behavior of soil when it is stabilized with different additives. Chemical modification in the soil due to additives plays an important role in physical modification of soil. Laboratory test program was aimed at evaluating the potential chemical parameters such as: pH, Silica, Aluminium oxide, Ferrous oxide, Chlorides, Sulphates, Calcium oxide and Magnesium oxide that are responsible to increase the strength and volumetric change behavior of modified soil treated with various additives.

Expansive soils when subjected to change in water content would undergo commonly swelling and shrinkage a cyclic process seasonally. Cohesive non-swelling method is one of the techniques used to control the swelling and shrinkage behaviour of these soils. On the other hand, using of waste materials in the pavement construction especially on clayey sub-grade has been in progress all over the world. Copper slag is one of the waste materials, which is being used for various applications in civil engineering. The laboratory test results related to soaked CBR (California Bearing Ratio) test conducted on a stabilized copper slag cushion-soil system for various thickness ratios ranging from 0.25 to 1.00 and stabilized with lime and cement separately are discussed. The increase in soaked CBR with the addition of lime from 2 to 10% to the copper slag for the thickness ratios of 0.25 to 1.00 was from 4 to 35 times when compared with no cushion, whereas, with the addition of cement from 2 to 10% to the copper slag for the same thickness ratios was noticed from 7 to 39 times. The results showed that the soaked CBR increases as the ratio of the thickness of cushion to the thickness of the expansive soil bed is increased and also with the increase in percentage of admixture.

Backfill material is one of the major constituents of Geosynthetic reinforced soil (GRS) structures. Current design guidelines conventionally recommend the use of free draining granular material as a backfill material. Owing to the fact that difficulty in finding these materials has increased the use of locally available marginal soil for the construction site as an alternative backfill. Use of marginal fill can reduce the transportation cost and environmental impact due to soil excavation and thereby reduce the overall construction cost of GRS structures. Major concern in using marginal soils as backfill is the build up of positive pore water pressure during construction, which reduces the internal shearing resistance of the soil. It also reduces the interface shear strength between the reinforcement and fill materials. The current study focuses on the shear behavior of marginal soil (SC type) and non-woven geotextile system under UU and CU triaxial testing conditions. Specimens were prepared at their maximum dry density (MDD) and optimum moisture content (OMC) with the change in number of geotextile layers. The test results revealed that the shear strength of reinforced soil increased with the number of geotextile layers in both UU and CU triaxial testing conditions. The pore pressure evolution showed the increased contractive response of marginal soil-geosynthetics system with the addition of geotextile layers. Failure pattern of the geotextile reinforced specimens exhibited bulging/barrel failure patterns between adjacent geotextile layers unlike shear band formations in unreinforced soil specimens.

The use of geosynthetic reinforced soil structures in various geotechnical engineering applications is increased in recent times. Conventionally, free-draining materials such as coarse to medium sands are used as reinforced fill material. However, the availability of sands are decreasing rapidly, and that raised certain economical and environmental issues. Fly ash is a good alternative to the sand as reinforced fill material. It is a by-product generated due to coal combustion and contains silt-sized hollow spherical particles having very low specific gravity. In the current research, an attempt has been made to evaluate the shear behaviour of the fly ash-geosynthetic system under undrained triaxial conditions. A series of undrained triaxial compression tests were performed on 100 mm diameter and 200 mm height specimens of fly ash having zero to four layers of woven and non-woven geotextiles at 100, 200 and 300 kPa confining pressures. The peak deviatoric stress was enhanced with the insertion of geotextile layers due to an increase in effective confining pressure within the specimen, generated by the mobilisation of large tensile forces at fly ash-geotextile interfaces. The rise in shear strength was more prominent in the case of woven geotextile as compared to non-woven due to its high stiffness and high load carrying capacity. The post-peak softening response was reduced, and the hardening response was increased as the number of geotextile layers increased. The values of shear strength parameters (c and φ) had been increased from unreinforced to four layers of geotextile-fly ash system except for a single layer system.

The frequency of rainfall-triggered landslides is increasing across the world. Infiltration of rainwater into the slopes with low permeable soil increases the pore water pressure and reduces the stability of slopes. Also, in the recent past, Kerala experienced many rainfall-triggered landslides. One of the most efficient way to prevent rainfall-triggered landslides would be the usage of composite geosynthetics which can combine the functions of pore pressure dissipation and reinforcements. In the present study, soil is collected from a nearby site where landslide has occurred and the geotechnical characterisation of the soil was carried out. An attempt was made to investigate the performance of steep soil slopes with and without the geosynthetics when subjected to rainfall, numerically. The study highlights the importance of the use of a composite geogrid in reinforced soil slopes composed of locally available marginal soil.

In the present study, laboratory one-dimensional consolidation studies under sustained loads have been carried out on pure soft saturated clay of 250 mm thickness in tank having inside dimensions of 570 mm × 570 mm. The clay bed was loaded at its center with the aid of a circular steel plate of 170 mm diameter and 20 mm thickness. Similar tests were performed by placing a layer of geocell mattress having opening 40 mm by 40 mm and 25 mm height. For these cases, the sustained load applied varied from 0.01, 0.1, 0.2, 0.3, 0.4, 0.8, 1.6 and 3.2 kg/cm2 for the time duration up to 90% consolidation for each load. The termination criteria considered was a maximum stress of 3.2 kg/cm2 or 70 mm whichever is early. Tests results of geocells were compared with the pure clay condition. This paper presents result of time vs settlement and load versus settlement for the various cases studied.

The usage of geosynthetic materials as a ground improvement technique has gained widespread approval due to its quality of construction, simplicity, and time-saving parameter. This study focuses on the use of geosynthetic geotextile as a reinforcement material for increasing strength properties of soils. This paper presents result of unconsolidated-undrained triaxial compression tests for investigating the behavior and failure mechanism of geotextile reinforced soils such as clay and red soil. The influence of varying number and locations of geotextile with varying confining pressures were studied. The test results show that shear strength and deformation resistance of reinforced soils significantly increased with the number and location of geotextile layers.

Due to the scarcity of soils having high bearing capacity, the need for ground improvement posed major challenges to the geotechnical engineering professionals. Amongst the many ground improvement techniques, the use of geosynthetics is always a preferred choice in the field of soil improvement. Geogrids are polymeric products formed by joining intersecting ribs. It has been recognized as a good alternative material to geosynthetics for reinforcement applications, due to its large spaces and good engineering behavior. The aim of present study is to determine the effect of Combigrid reinforcement on bearing capacity of sand. For this, three model footings of rectangular, square, and circular shape having the same equivalent area of 100 cm2 are taken and the comparison of results are made. In all the tests, the placement density is maintained by rainfall method, equivalent to relative density of 30% which indicate loose state of sand behavior. The model test tank of size 500 mm × 500 mm × 600 mm is used. The ultimate bearing capacity of footing on sand is determined from the load-settlement curve. The tests are performed by placing the first layer of reinforcement at different depths. Parametric studies have also been made with different number of reinforcing layers and some significant observation have identified.

Geosynthetics materials are having wide application in Geotechnical Engineering field. It is available in different forms and can be applied as per the different functions like separator, lining, barrier, filter, reinforcement, etc., in various application area of Geotechnical Engineering field. One of the application of Geosynthetics material in pavement construction as a separator and/or moisture barrier enhances the performance of pavement. In this study the strength parameter of woven coir mat, Jute mat, and geomembrane was analyzed through CBR (California Bearing Ratio) test. In this study, soil aggregate system was used in the CBR mold with and without the geosynthetics material. The soaked and unsoaked CBR value of geotextile and geomembrane was determined and found that their application in the pavement construction can be very effective.

The use of geosynthetics for the improvement of sandy soil is widely acknowledged. However, the effect of using geosynthetics is negligible for the small settlement of foundation resting over it. Therefore, prestressing the geotextile has a beneficial effect on the performance of the foundation even for the small settlement. In this study, the behavior of the square footing resting on the prestressed geotextile-reinforced sand is carried out through both laboratory model test and numerical analysis. The experimental study is performed using 100 mm × 100 mm (B × B) square footing embedded at a depth of 50 mm, resting on unreinforced sand and sand reinforced with both geotextile and prestressed geotextile. It is found that placing the geotextile at 0.2B depth below the footing gives the maximum improvement. The improvement of the study is reported in terms of bearing capacity ratio and settlement reduction ratio. Prestressing of the geotextile shows 73% reduction in the settlement and 261% increment in the bearing capacity in comparison to footing resting on unreinforced sand. The results of the numerical analysis using Plaxis 3D is found to be in good agreement with the experimental study.

Numerical model test results for the ultimate bearing capacity (UBC) of a shallow strip footing resting on geogrid reinforced sand subjected to eccentric vertical loading are presented in the study. The numerical modelling is carried out using finite element tool Plaxis 3D in which the footing of size 5 m × 1 m × 0.1 m (L × B × t) is modelled as plate element which rests on soil volume of 5.05 m × 11 m × 8 m (L × B × H). Deep footing mechanism (i.e. width of reinforcement b is equal to the width of the footing B) is adapted in the present study. Several influencing parameters like relative density of sand (Dr, %), embedment ratio (Df/B), eccentricity ratio (e/B) and number of reinforced layers (N) have been considered to observe the UBC of the footing. 216 numbers of numerical model conditions have been developed where Dr (%) varies from 25 to 75% @25%, Df/B varies from 0 to 1 @0.5, e/B varies from 0 to 0.15 @0.05 and N varies from 0 to 5 @1. The Plaxis model is created and analyzed, following HS Small model. The study reveals that irrespective of Df/B and e/B, among all the simulated conditions, the influence of reinforcement is significant for Dr = 25%. It is observed that the failure envelope is shifting from symmetry to one side as the loading is changing from centric vertical to eccentric vertical. The optimum number of reinforced layers (N) for all the cases was found to be in the range of 2–3, after which the effect of reinforcement seems to have marginal effect on the UBC of the footing.

Facia is an important component of geosynthetic reinforced soil (GRS) system provided to control the erosion of backfilled material, to prevent the damage of reinforced material, and to give the aesthetically pleasing appearance. The increased use of marginal fills in the construction of a GRS wall created certain issues of differential settlement between the facia system and reinforced fill. This differential settlement caused additional forces at the connection joint of facia and reinforcement and sometimes resulted in shear breakage of reinforcement and the collapse of the structure. Hence, the aim of the current research is to develop a design and construction sequence of a new kind of facia system for marginal fills that eliminate the issues related to the differential settlement and prevent the functionality of the structure. Soil nails are used in the proposed facia system to connect the full height panel facia to wrap-around GRS wall. The design of GRS wall and soil nail is done according to the provisions given by design codes, and the steps for the combined design is discussed. An attempt was made to give the mathematical formulation of the additional pull-out force generated inside the soil nails due to the differential settlement. It is proposed to add this additional force in the design checks of soil nails for the combined system. The construction sequence of the proposed system is suggested by considering the easiness and stability at each stage of construction.

The geosynthetic reinforced soil techniques have emerged as exciting engineering techniques mainly due to their cost effectiveness, technical simplicity and ease of construction. They are considered superior as compared to other alternatives in the context of their stability even under seismic conditions. This paper aims at understanding the effects of the width and location of surcharge loads on the performance of the geosynthetic reinforced soil walls. The numerical simulations of a geosynthetic reinforced soil wall is analyzed using the finite element software PLAXIS 2D. A very fine mesh was used with water table at great depth for the analysis. A multi-stage construction was simulated and plastic analysis was carried out. Different combinations of surcharge are applied and the stresses developed in the soil, displacements at the top, middle, and toe of the wall and maximum strains developed in the wall for the different surcharge combinations were plotted and analyzed.

The soil reinforcement interaction is a major issue in the design of reinforced soil structures. In order to study it, pullout parameters such as pullout friction or cohesion between reinforcement and soil are selected. The pullout parameters are determined by means of the pullout test. The reinforcements were embedded in a granular medium. Reinforcements increase the shear stress in the soil mass through the tensile force in the reinforcement. The reinforcement used were natural geotextiles, mainly due to its eco-friendly and biodegradable nature. The natural geotextiles were anchored in order to enhance the pullout resistance. Wooden anchors were used due to its non-corrosive nature. On adding anchors, the passive pressure area between the anchors and the geotextile increases during the pullout procedure, as a result of which the pullout resistance of the reinforcement increases. The Geotextile- Anchor system is tested using the pullout test where the variables used are anchor density, anchor length (20, 15 and 10 cm) and overburden pressure (2, 3, and 5 kPa). From the experimental results, the pullout resistance of soil under loading conditions increased on the provision of anchors in the reinforcement and its effectiveness increases with increase in overburden pressure.

A significant number of the pavement structures fail a long time before their design life due to the poor quality of construction materials, inadequate compaction, inadequate preparation of the subgrade, overloading, etc. There are two methods to overcome this issue. The primary choice is by increasing the thickness of various layers and the other alternative is by increasing the strength and rigidity of the pavement layers which lowers stresses on the pavement layers. Rutting is a common feature observed in flexible pavements supported on weak subgrades. Reinforcing the weak subgrades is one of the promising alternatives to alleviate the pavement surface rutting. Geocell reinforcement, a three-dimensional confinement increases the load-carrying capacity of the soil. In the present study, the improvement in the strength and stiffness of flexible pavement systems using geocell confinement is investigated by placing geocell in the subgrade soil. The finite element analysis of the model will be done by using the ANSYS tool and analytical results such as Strains generated in each layer and propagation of stresses are studied.

Different types of anchors are used for offshore and onshore structures to resist uplift forces. In case of soft clay the uplift capacity may be increased with geotextile reinforcements. In the present study an attempt has been made to find uplift capacity of model plate anchors of sizes 50 mm × 50 mm and 75 mm × 75 mm, in reinforced and unreinforced soil with embedment ratios of 1, 2, and 3. Properties of clay and geotextile have been appropriately obtained by carrying out relevant laboratory tests. Model anchor tests have been carried out by applying monotonic loads through pulley arrangement and recording displacements using Linear Variable Differential Transformer (LVDT). To supplement the experimental results, numerical analyses have been carried out using ABAQUS software, simulating experimental models with similar plate sizes and embedment ratios. The experimental results agree well with the numerical ones. The geotextile layer has been considered to be placed for an extent of four times the anchor width at a distance of 0.25 times the embedment depth from the bottom of the anchor. It has been observed that pullout capacity increases with increase of plate size on an average by 113% for unreinforced clay when the plate size increases from 50 to 75 mm. For 50 mm plate with embedment ratio equal to 1 the improvement has been found to be 25% and the same has been found to be 36% and 31% for embedment ratio 2 and 3, respectively. This improvement has been found to be higher for larger plate sizes.

The behavior of Geotextile reinforced force on reinforced embankment was analyzed in this study. The embankment was backfilled with flyash (80%) and clay(20%) soil and the safety factors obtained from general limit equilibrium and finite element analysis. Variable Geotextile stiffness of 50–2000 kN/m and varying spacing, Sv of 0.4 and 0.5 m were taken as reinforcement and series of finite element (FEM) analyses were carried out with GEO5-FEM software. The FEM analysis results showed that the maximum geo-reinforcement force was observed in first layer of Geotextile, placed at bottom of the embankment in the range of 0.66 kN/m at extreme ends to 2.34 kN/m at central region of embankment. There was no force developed in geotextile from both sides of embankment boundary upto 5 m. Amongst the total number of 15th layers of geotextile (Sv = 0.5 m), and 19th layers of Geotextile (Sv = 0.4 m), the Geotextile forces were observed only upto the 13th layer and 16th layer of Geotextile reinforced embankment, respectively. Beyond these layers, there are no forces in geotextile. Hence, there is no requirement of Geotextile reinforcements at top 1.0–1.2 m of the embankment crest width. From this observation it can also be concluded that for further economy, the tensile strength or stiffness of each layer of Geotextile can be varied for a given reinforced embankment slope by providing geotextile of higher strength or stiffness at the bottom of the embankment and lower strength or stiffness at the top of the embankment. It results in savings in terms of cost, time, material, and execution.

Extraction of iron ore through open cast mining technique is most common and popular practice in India. The method is also very cost effective and more profitable as entire mineral is being excavated from the mine. But it creates major environmental hazards by generation of huge quantity of mine waste and its dumping on nearby land. Mine waste is collected and stored as dump which occupies a huge space. The dumps are categorized depending on its use like, waste dump and subgrade dump. However, to produce best steel grade material, the iron ore is processed and cleaned through wet technology. The rejected waste known as slime is collected and stored in pond. After evacuation of water/moisture from the slime it is stored as slime dump for future use. In most of the cases the height of dumps reaches beyond its limit and tends to collapse. By this way in most of the cases the dumps become overburden (OB Dump) and destabilizes. Eventually, due to presence of very fine quality of material high rate of erosion takes place in slime dumps owing to precipitation and wind which further affect the stability of dump. The situation gradually becomes worst causing serious environmental pollution and degradation of nearby land. Mining can become more environmentally sustainable by developing and integrating best environmental practices in mining operations. These practices include preventing soil, air, and water pollution, adoption of zero liquid discharge, reduced energy consumption, adequate waste utilization, social awareness, and conducting successful reclamation activities. In order to stabilize the OB Dumps appropriate measures need to be taken for rehabilitation and ensure erosion control of slope with suitable material along with adopting bioengineering technique. Jute geotextile (JGT) an eco-friendly, cost effective, material developed by Jute Geotextile Cell (JGT) of National Jute Board, Ministry of Textiles, Govt. of India is being widely used all over the world in various forms for mitigating such soil related problems. Performance of JGT has been reported to be much superior technically to other available materials meant for erosion control works apart from its environmental advantages. It possesses high tensile strength, biodegradable characteristics and is commonly used for erosion control, road construction, hill slope management, etc. The use of JGT on trial basis in Noamundi Iron Mine of TATA steel Ltd in slime dump management was undertaken for the 1st time. The results observed within a period of 3 months after application of JGT was highly encouraging. Vegetation was grown through the openings of JGT and the slime dump was stabilized. The features of the site, methodology adopted along with properties of JGT and its effect are explained in this paper.

The usage of geosynthetic material as ground improvement technique has gained its widespread approval due to its quality of construction, simplicity and time-saving parameter. This study focuses on the use of geocells made from geotextiles as a reinforcement material for reducing settlement. A structure of these cells interconnected by joints to form a cellular network could be used for the confinement of soil. This paper represents results of laboratory model tests on square footings supported by geocell reinforced soil beds such as sand and red soil. The influence of varying parameters such as depth to the first layer of geocell, the width of geocell, the height of geocells and the density of soil were studied. It was found that the load-carrying capacity of the foundation can be significantly enhanced by the inclusion of geocells and also the configuration and arrangement of geocell reinforcement has a pivot role in the performance.

This study reviews the available design methods for the use of geogrid in unpaved roads. Characterization and properties of geogrid for effective utilization in pavements have been discussed briefly. The effective optimal location in the pavement, minimum number, interaction coefficient, and tensile strength criteria of geogrid have been well explained in this study. This study also includes results of experimental work, small scale laboratory test, and field performance of geogrid reinforced flexible road pavement. Currently, there is no proper guideline available for the use of geogrid reinforcement in flexible pavements. All the past application of geogrid in pavements is mainly based on experience, field study, laboratory study, and few limited available guidelines. This study provides a detail description of previous findings and research gap for the use of future research.

The stability of embankments supported on soft clay foundation is a complex problem. To improve the stability of embankment and its foundation, the most feasible option is to reinforce the locally available soil with suitable geosynthetics since granular soil is now very scarce and costly. The effectiveness of geosynthetic reinforcement embedded in cohesive soil is very less due to build-up of pore water pressure, creep and less interaction with soil. Moreover geosynthetics demonstrate their beneficial effects only after considerable settlements, since the strains occurring during initial settlements are not sufficient to generate significant tensile stress in the reinforcement. Prestressing the geosynthetic and encapsulating it in a thin granular soil layer is a promising technique to reduce the requirement of granular soil and to increase the load bearing capacity without the occurrence of large settlements. This paper investigates the beneficial effects of prestressing the geosynthetic and encapsulating it in a thin layer of granular soil when used to reinforce a soft soil foundation of an embankment. A series of finite element analyses are carried out using the FE software PLAXIS 2D, and its results are validated by comparing them with those obtained from laboratory scale load tests. It is observed that the load–settlement behaviour can be considerably improved by reinforcing the soft clay foundation with prestressed geosynthetic encapsulated in a thin layer of granular soil. The improvement is significantly influenced by the magnitude of prestress in the geosynthetic reinforcement.

Soft soil particularly clayey soil has a very low value of California bearing ratio (CBR). As the CBR value is low the thickness of the granular layer is more, which is resulting in the higher cost of pavement. To overcome this issue, geosynthetics (geogrids) are mainly used in the granular layer of pavement as reinforcement. For cost-effectiveness and durability of pavement, geosynthetics are used from the last 2–3 decades but still, there is no proper design philosophy available for use of geogrid in the flexible pavement. To quantify the benefits of geogrid reinforcement, field studies were conducted on the geogrid reinforced test section constructed on Mandvi-Serulla state highway by using falling weight deflectometer (FWD). Results of FWD data confirmed that the modulus value of geogrid reinforced layer is increased by 1.40 times than that of the unreinforced granular layer. A finite element model was also developed in PLAXIS 2D to justify the benefits of geogrid reinforcement against fatigue and rutting failure.

The present scenario in India demands maximum transit facilities to develop at a low cost within shortest feasible time. Analysis performed on majority of the failed roads owe them to the founding soil over which these roads were constructed. Jute geotextiles, produced abundantly in this subcontinent, may be used beneficially and economically with great efficacy for stabilization of such weak subgrades. Though there have been extremely limited but successful construction of roads over soft soils using jute geotextile in India, their systematic use is yet to be resorted to. Since, the experience gained from their adoption in practice and also from ongoing research certainly prove to be rewarding, the geotechnical community should perhaps exploit this potential and encourage such applications which result in enhanced performance of highways at an optimal cost. A tentative design methodology thought to be adopted for this is also presented.

The surcharge due to building and roads affects the subsurface and ground behaviour and causes the settlement problem. The settlement problem is more effective when the structure is built on expansive soil. Because of settlement resulting damage and repair work may cost a considerable high amount, an accurate modelling of subsurface condition and prediction of ground-structure interaction can help to avoid such a foundation problem. In this study, settlement analysis by using conventional method and two-dimensional finite element (2D FEM) modelling are both carried out and the results are compared. Settlement analysis by using the conventional approach is performed for the particular geometry by using Terzaghi’s one-dimensional consolidation theory. The compressibility coefficient involved in the formula is determined from consolidation test data. Thereafter settlement results are presented as settlement prediction on-time rate for comparison purpose. Then after 2D FEM analysis is performed for the same soil data and soil model is generated using FEM computer program. The results obtained from the analysis are compared with conventional method results. Terzaghi’s equation, which is used in the conventional approach, is a logarithm function whereas 2D FEM analysis based on linear function according to Hook’s law of linear elastic stress–strain relationship. Three different soil layers, which have different E and γ value determined for each layer and thickness of each layer is considered. The number variable affecting the results restrained comparison between conventional and 2D FEM settlement to be qualitative.

The assessment of soil properties for the design of structure requires a wide range of tests. Sampling difficulty, time and cost constraints forces the practitioners to adopt correlations existing among the in situ tests and the physical or mechanical properties of soils. This paper presents the application of neural network to predict the cone side resistance (qs) obtained in the cone penetration test (CPT) for the cohesive soil based on plasticity index (PI), consistency index (CI) and the under drained shear strength (Su). Feed-forward back propagation algorithm was used for this purpose for the development of neural network model which was developed using 50 in situ dataset collected from the literature. Finally, the cone side resistance obtained from the developed neural network model was compared with the measured cone side resistance obtained from the CPT tests reported in literature. Further, the sensitivity analysis was performed to study the impact of plasticity index, consistency index and the under drained shear strength on the cone side resistance. The results of this study reveal that the developed neural network model was able to predict cone side resistance accurately.

This paper presents a bearing capacity estimation of the rough strip and circular footings embedded in dense sand overlain by loose sand strata. Numerical study is carried out using finite element analysis (FE) wherein the soil was assumed to obey Mohr–Coulomb’s yield criterion with either associated (ψ = ϕ) or non-associated flow rule (ψ < ϕ). The bearing capacity was computed for different values of soil friction angle of the top and bottom layer (ϕ1 and ϕ2, respectively), depth of the footing (Df) from the surface and the thickness of top dense layer (H). The comparison was made with those of the available literatures wherever applicable.

In this paper, Artificial Neural Network (ANN) and Genetic Expression Programming (GEP) have been used to develop two Liquefaction Index (LI) equations which will be able to predict effectively whether a soil layer at any depth would liquefy or not in case of an earthquake. 226 post-liquefaction Cone Penetration Test (CPT) data (133 are liquefied cases and the rest 93 are non-liquefied cases) have been collected from published literature and using the collected data, an ANN and a GEP model have been built. From each developed model, a LI equation has been developed which uses CPT data of soil and Peak Ground Acceleration (PGA) as inputs and returns either 1 or 0 (1 means liquefaction may occur and 0 means liquefaction may not occur). A comparative study between both the models has also been conducted in this study.

Vertical drains are often used to accelerate the consolidation settlement in soft clays subjected to preloading. Even though there are a variety of ground improvement techniques available, prefabricated vertical drains (PVD) in combination with preloading have become a popular method for soft soil problems as it provides an effective solution. Marine clay is one such type of soft soil which is highly compressible and causes severe distress to the structure constructed over it. In this study, a numerical investigation is carried out to explore a better insight into consolidation behavior of Marine clay improved with PVD. A surcharge load of 25 kPa is applied to accelerate the consolidation process. The analysis is carried out using the finite element software ABAQUS, employing the modified Cam-Clay theory. The aim of this study is to investigate the effect of smear on the settlement rate with different drain spacing (Drain spacing ratio n = 10, 15, 20) and for two different thickness of clay layers.

The flexible pavement consists of different thickness of layers of different materials. CBR, elastic modulus, moisture condition, unit weight are the basic characters of subgrade for the design of pavement components. Characterization of CBR is of primary importance for all flexible pavement-related tasks. CBR is a laborious and time-consuming test, therefore many researchers have suggested ANN techniques to predict CBR because it provides much better alternative. As per the IRC recommendation, CBR should be found for a soaked specimen of subgrade soil. The study presents the application of ANN for estimation of CBR of clay-gravel mixture under soaked condition. Nine different clay percentage and five different moisture range were selected for conducting CBR tests. In the analysis, dry unit weight parameter was made standardized using mean particle size of the mixtures and surcharge weight which was kept on the mould to provide vertical confinement while penetration of the plunger during testing. To determine the contribution of each independent variable, many methods have been proposed for sensitivity analysis. In the present study, Garson, Olden and Lek's profile models were developed using neural network to assess the influence of the parameters. From both the models contribution of independent variables is visualized. CBR values are found to reduce continuously when blending with clay fraction, but moisture content has more negative impact than clay on CBR values. The unit weight has strongest relationship with CBR. The strength of model that was developed has been examined in terms of standard error and co-efficient of determination. The standard error is 0.08800434 and R2 values are 0.9316485 of the generated model. It shows that the ANN technique is able to learn the relation between CBR and soil mass.

Geosynthetic encased granular columns are used to effectively stabilize marine soft clay deposits with low undrained shear strength. The present study focuses on assessing the behaviour of geosynthetic encased granular columns in very soft clays using two FE approaches namely 2D axisymmetric and 3D unit cell. The study compares the results obtained for three cases namely virgin soft clay without any granular column, ordinary granular column and geosynthetic encased granular column. The effectiveness of geosynthetic encasement is examined by assessing the length of the geosynthetic encasement and the tensile secant modulus of the geosynthetic on the dissipation of excess pore pressures and settlement. Additionally the settlement reduction ratio parameter is also investigated for both the approaches and the results are compared.

Construction of shallow footing near the sloping ground is a common practice in the hilly region. However, bearing capacity estimation of such footings requires special attention due to the interference of slope geometry with the failure zone of the footing. It has been observed that the bearing capacity of footing reduces substantially for such cases as compared to the plain ground due to the lesser passive resistance offered by the disturbed failure zone of the footing. In this regard, the conventional limit analysis-based bearing capacity theories are noticed to provide conservative results which lead to uneconomical design of the sub-structure. A finite element-based numerical study has been carried out in the present study to investigate the bearing capacity of strip footings resting on the sandy sloping ground. The influence of setback ratio and the effect of inclined loading on the load-carrying capacity of the footing has been investigated, and the results are discussed in details.

The present study focused to estimate the angle of internal friction (ɸ) of cohesionless soil and cohesive (c-ɸ) soil considering field standard penetration test (SPT) data. Based on the SPT data an empirical correlation has been established between standard penetration number N and internal friction angle to predict the friction angle of soils. All the field standard penetration test data are collected from six different places of East India. Regression analyses were performed using the SPT data collected from 40 different boreholes containing 330 data points. The SPT N values obtained from different sites are observed to vary between 4 and 70. The in-situ bulk density of undisturbed samples recovered through pitcher sampler is in the range of 17.90–18.90 kN/m3. In situ water content and fines content observed plays an important role in case of c-ɸ soil, hence plasticity index (PI) and fines content (p) are also included in model equation in case of c-ɸ soil. The predicted results obtained from developed model equation appears to be in good agreement with existing equations in various literature. By using regression analysis, the empirical equations are developed. The most important thing is to find out the friction angle of c-ɸ soil which is useful for the fields. The estimated equations are verified by validating the correlations with experimental values obtained from field which in turn can be used for geotechnical engineering design problems. Thus, the study provides a simplified and faster analysis of angle of internal friction for different types of soils.

Pipelines are an important element of modern infrastructure as they are the carrier of essential transportation materials. The proper knowledge of the soil-pipe interaction mechanism leads to the better performance of the buried pipe system. This paper describes the study of the behavior of a flexible pipe, buried in sandy soil. Numerical analysis was performed using MIDAS GTS NX finite element software. A pipe having an outer diameter of 0.45 m and 10 mm thickness, subjected to the strip surface load was modeled. The strip load was varied from 0 to 100 kPa. Two types of pipe materials, namely; Polyvinyl Chloride (PVC) and High-Density Polyethylene (HDPE) were examined. The analysis was performed in loose, medium dense, and dense sandy soil; with different burial depths of pipe, having embedment ratio 1,2 and 3. The analysis revealed the decreasing nature of pipe deflection with the increase in embedment depth, whereas the crown stress was found to be minimum for the embedment ratio 2. The detailed analysis showing the influence of pipe stiffness, soil stiffness, and pipe burial depth on the vertical pipe deflection and crown stress is presented in this paper.

Prefabricated Vertical Drains (PVDs) is one of the most common methods used for improving the engineering properties of soft clayey deposits. These are used to accelerate the consolidation process of treated ground and thereby speed-up the construction activities. Different techniques can be combined with PVDs to augment the efficiency of the method. Application of vacuum is such a technique which in combination with PVDs helps to accelerate the dissipation of excess pore pressure under embankments. This paper presents the equivalent plane strain modeling of the vacuum consolidation combined with PVDs and surcharge loading, using the finite element program ABAQUS. Settlement and excess pore pressures obtained from the analyses were compared with the observed field values as mentioned in the literature. Influence of spacing of the drains on the consolidation behavior is also studied. A comparative study is conducted between the modeling methods proposed by Indraratna and Redana, J Geotech Geoenviron Eng 123(5):474–478 (1997) and Chai et al., J Geotech Geoenviron Eng 127(11):965–972 (2001). Also, the settlement obtained from the equivalent plane analyses is compared with the analytical solution proposed by Hansbo, Ground Eng 12:5 (1979).

Soil-foundation interaction studies are quite useful to evaluate the behavior of shallow foundations, especially for flexible foundations. The soil and foundation parameters which affect the base pressure and settlement below shallow foundations includes the type of soil, soil compressibility, modulus of elasticity of soil, foundation dimensions, and thickness. Additionally, variation in loading parameters also have significant effect on the behavior of foundation. The foundation may behave as flexible or rigid foundation depending on the variation in loading. Hence, it would be interesting to understand the influence of variation in loading on behavior of shallow foundations. In this regard, the present study evaluates the effect of change in magnitude of loading on shallow foundations. For the study isolated foundation and raft foundation have been considered and analysed in Staad Pro. Four different magnitude of loading on the columns supported by the foundation have been considered in the study. Further, the foundations have been modeled in PLAXIS 2D software and the results have been compared with that obtained from STAAD Pro. in order to understand the influence of modeling soil as discrete springs (in STAAD Pro.) and continuum (in Plaxis 2D). From the study, it is observed that magnitude of loading has significant influence on behavior of foundation. The base pressure and settlement obtained from STAAD Pro. analysis is relatively uniform. However, the base pressure distribution obtained from PLAXIS 2D analysis varies significantly, although the settlement response is more uniform. The study demonstrates the soil-foundation interaction response of shallow foundations under different loading condition by using STAAD Pro. and Plaxis 2D analysis.

Piles are generally used to support superstructures such as bridge abutments, high -rise buildings, and transmission towers, which are subjected to heavy axial forces as well as lateral forces. Nowadays, construction of these structures near the natural or man-made slopes has been increased due to the unavailability of flat grounds. To support the heavy loads coming from the superstructure, normal conventional piles (0.3–0.6 m as per IS 2911) may not be sufficient for some situations, especially located near slopes. The mobilization of the ultimate load-carrying capacity of large diameter piles is different from standard conventional piles given in IS 2911. In this study, the behavior of large diameter piles resting on or near the cohesionless soil slopes is studied using a finite element method. The effect of various influencing parameters like slope gradient, the diameter of pile, length to diameter ratio of pile, and location of water table on the axial and lateral load-carrying capacity of the pile have been studied.

Piled-raft foundations give an affordable foundation alternative to areas where the performance of the raft alone can’t fulfill the structural design requirements. Under these circumstances, the expansion of a set number of piles to support raft may improve the ultimate load capacity, the average settlement as well as differential settlement performance, and the essential thickness of the raft. In this study, an attempt has been made to describe the different methodologies of modeling the soil–structure–foundation system for piled raft foundation and a 3-dimensional finite element model of a piled raft foundation is proposed to simulate the case of a piled raft foundation through PLAXIS 3D software which accounts for pile-to-pile, raft-to-pile, pile-to-soil, and raft-to-soil interactions. The model will be utilized to examine the impact of the key parameters affecting the performance of piled raft foundation during uniform loading and building column reactions on piled raft in case of clayey and sandy soil. A parametric study is additionally conducted to show the impact of different geometrical parameters on the performance of piled raft foundation. The results of this study could be used as guidelines for achieving economical design for piled raft foundations and to lead to additional research in this area.

Pile foundation is a mostly used type of deep foundation to transfer superstructure load into the subsoil and bearing layers. However, accurate prediction of the elastic settlement of pile is difficult concerning complicated pile–soil interaction phenomenon. The present paper deals with the analysis of single and double-stepped pile and proposed evaluation are conducted with the aid of finite element software PLAXIS 2D. In this analysis, load-settlement behaviour of a single conventional, single stepped and double-stepped pile is evaluated in granular soil. For the single conventional pile, single stepped and double-stepped pile, the parameters like the total volume of the pile, the total length of pile, the deformation properties of surrounding soil and pile kept constant for all the cases to study the variation in behaviour. In the double-stepped pile, the diameter of the pile for upper, middle, and lower portion has been varied to study the effect on the load-settlement response for regular and inverted manner. The results obtained from the analysis of the single conventional pile, single stepped pile, and double-stepped pile were compared with the experimental results of F. Kirzhner, and G. Rosenhouse which were performed in 1982 in Ashkelon South power station in Israel. Results show the better performance behaviour of the regular double-stepped pile as compared to the inverted double-stepped pile; single stepped and single conventional pile.

In an established foundation design, it is usual to consider initially the use of shallow foundation. If shallow foundation is not adequate, deep foundation such as a pile foundation is recommended. Unlike the predictable pile foundation design in which the piles are designed to carry the major amount of load, the design of a Piled Footing allows the load to be collectively transferred between the footing and pile as well increase in capacity due to confinement below footing. Hence, it is important to take this complex soil–structure interaction effect into account. The present work is an attempt to determine the increase in capacity of piled footing due to the increase in skin friction of the pile beneath the shallow footing due to the confinement offered to the sand by the shallow footing. A parametric study is carried out only for cohesionless soil. The foundation type is circular footing over the circular pile of uniform cross-section. For this, different geometrical data viz. diameter of footing and diameter & length of the pile has been chosen after a review of different researches carried out in this area. To handle such type of soil–structure interaction problem, numerical simulation is done with the help of FEM software, PLAXIS 2D. While using PLAXIS 2D, the axisymmetric condition for modelling the pile, 15 nodded triangular elements, and Mohr–Coulomb model for the soil properties are used. After analyzing sets of problems in PLAXIS, it is concluded that Piled Footing proves to be advantageous for footing resting on loose sand rather than dense sand due to enhancement of skin friction beneath footing. The skin friction is increased even in dense sand, but at the cost of losing the capacity of shallow footing.

Application of geostatistical techniques for in situ site characterization has received much attention in the last couple of decades. Kriging is one of the popular and accurate geostatistical techniques for the interpolation of spatially varied random variables. This study considers the development of a generalized ordinary kriging algorithm for use with site characterization. Ordinary kriging with a constant mean of stationary variable was applied to generate contour map and the error variance map to infer on the spatial variation of the parameter under consideration. In this study, the clay content parameter from a refinery project area in Orissa is interpolated using ordinary kriging technique. A generalized MATLAB code is developed to select the best fit semi-variogram for the sample data, to apply ordinary kriging technique, and to generate the surface profile. The spatial distribution of clay content values across the region is studied using prediction surface, and accuracy is checked using error variance profiles. Results of the analysis are also compared with simulation using ArcGIS based geostatistical analyst® and cross-validated using statistical parameters. Our results conclude that the proposed algorithm can be extended to predict other in situ soil properties in the field of geotechnical engineering.

Piles are subjected to lateral loading due to wind or wave action and earthquakes. Therefore, it is important to understand the pile response under the action of lateral loads. The study of laterally loaded pile response requires a proper assessment of soil–structure interaction phenomenon involving the interaction between the pile and the surrounding soil. The deflection of pile is an important factor to be considered in understanding the behavior of laterally loaded piles. Pile foundations are majorly utilized in coastal regions and are generally susceptible to slopes. Hence, to understand the effect of sloping ground on a laterally loaded pile is a necessity. The lateral loads may act on both directions (in the forward direction of slope and reverse) depending on natural phenomenon. Though, various experimental studies have been done to understand the effect of slope on laterally loaded piles, the effect of loading direction is predominantly not considered. In this paper, the results of the laboratory model tests performed to study the effect of slope and loading direction on laterally loaded piles installed in cohesionless soil (Muthukkumaran, Int J Geomechan ASCE 14(1):1–7, 2014 [1]) are validated using FEM software PLAXIS 3D. The slope of 1V:1.5H is maintained throughout the experimental set. The relative densities, distance from the crest of slope toward both sides (slope and embankment) and loading direction are variables that are considered. The pile capacity in sloping grounds is compared to that in the horizontal ground and the influence of slopes on the pile capacity is also discussed.

Excavation support system is essential component of modern time, where buildings with multiple basements are essential for parking and other purpose in large cities, where adjoining buildings are already functional. The purpose of this work is to present the comparison of the behavior of sheet pile wall at critical depth obtained from conventional method and finite element analysis. The conventional methods used in the structural design of sheet pile walls are based on the limit equilibrium approach. Program in MATLAB software is developed for this purpose. This program is evolved from simplified method for design of flexible retaining structure, which is introduced by the Herman Blum (1951). It is noted that conventional design method for retaining structures is unable to determine deformation of structure which is important for serviceability consideration. Hence finite element method was used to perform numerical modeling and analyses to evaluate the structural response and the behavior of wall. PLAXIS 2D software is used for this purpose. Present work is an attempt to study the behavior of cantilever and anchored sheet pile wall penetrating in homogeneous cohesionless and cohesive soil, c-φ soil, and layered soil for the excavation depth of 3 and 6 m.

Bearing capacity is an important aspect to design a footing located on or near a slope as the conventional two sided failure mechanism due to shear failure may transit to a one sided slope failure when influence of slope is significant. In contrast with conventional limit equilibrium method postulating a log-spiral failure mechanism, this study adopts a discretization procedure known as Discontinuity Layout Optimization (DLO) technique to generate a kinematically admissible failure mechanism using LimitState:GEO. Parameters such as horizontal setback distance, footing width, slope inclination angle, internal friction angle, cohesion and unit weight of soil are taken into consideration to investigate the effect on bearing capacity. Slope of different regions of India are considered for parametric study. The study shows that with increase in slope angle, bearing capacity decreases but increases with increase in other parameters. The failure mechanism of the footing is changed after a particular setback distance as influence of slope is negligible.

Structural Design Practice has transformed from conventional Working Stress Method to Limit State Method—Load and Resistance Factor Design (ACI) or Partial Safety Factor approach (IS Code). Geotechnical Design Philosophy is in the transformation stage to implement Load and Resistance Factor Design (LRFD). Eurocode-7 accommodates three design approaches (DAs) that allow partial factors to be introduced at the beginning of the calculations (strength partial factors) or at the end of the calculations (resistance partial factors), or some intermediate combinations thereof. IS 6403 provides guideline to calculate ultimate bearing capacity for shallow foundations. It gives bearing capacity factors and other factors, viz., inclination factors, depth factors, shape factors, etc., and accounts for the effect of water table. To calculate allowable bearing pressure a Factor of Safety 2.50 is recommended separately by IS 1080. Eurocode 7 provides guideline for proportioning shallow foundations using partial safety factors for Action, Material Parameters, and Resistance. The Action includes Dead Loads as well as Imposed Loads. Material Parameters includes shear parameters “c” and “φ” in drained and/or undrained state. The Resistance Factors are assigned based on the design methods used. For shallow foundations three design approaches are considered for which partial safety factors are given. Parametric study is carried out to compare the ratio of capacity obtained from IS Code WSM and EC7 LSM for different soil type (c-soil, phi—soil, and c-phi soil) keeping other parameters constant.

Rock Quality Designation (RQD) of a site is a very important engineering property from geotechnical considerations. RQD is very useful in identifying potential problems related to bearing capacity, settlement, slope stability problems and also serves as warning indicator of low quality rock zones that requires greater scrutiny. However, due to time and cost considerations, geotechnical investigations are carried out at larger spacing which calls for appropriate techniques for estimation of data at intermediate locations for appropriate judgements. An earlier study reported IDW (Inverse distance weighing method) to be appropriate methodology for 20 m level below ground level at the site. It was deemed necessary to examine whether similar technique would be applicable for other layers also. This paper deals with estimation of RQD values at intermediate locations from an available coarse grid data using various spatial interpolation techniques for different depths. Geo-statistical methods selected for the present study are K nearest neighbour (KNN) mean method, Inverse Distance Weighing (IDW) method and Trend Surface Analysis (TSA). Spatial interpolation has performed at depths 20, 25 and 29 m below ground level. IDW and KNN methods estimated the RQD values at all depths with good accuracy followed by TSA method. It is observed that site-specific parameters obtained for best performance are different for different depths. It is necessary to analyse the data at each level and perform spatial interpolation to obtain the site-specific parameters to obtain best results.

One of the terminology which quantifies the amount of damage to the tunnel face, invert, crown, and sidewall is damage distance. It is the minimum distance where blast provoked discontinuities are formed beyond the periphery of newly excavated face. This distance mostly contains the unnatural discontinuities developed due to blasting. In order to cater to the uncertainties and prediction of large numbers of outcomes for different combinations of controllable and uncontrollable parameters, probabilistic analysis has been carried out in this study. As input for probabilistic analysis, the controllable parameters taken into considerations are maximum charge per delay (W), perimeter charge factor (P), specific charge (q), and as uncontrollable parameters rock quality index (Q). Data has been compiled from the literature pertaining to three different underground tunnels. The relationship between damage distance and the input parameters have been determined by drawing scatter plots implementing simple regression. These input have then been used to develop a deterministic model for prediction of damage distance. Following this, the probabilistic analysis employing Monte-Carlo (MC) simulation has been carried out. The existing blast design has been found to have 100% probability of occurrence for damage distance greater than 1 m. The occurrence of 1 and 2 m damage distance has been found to be inevitable. In order to mitigate the intensity of damage distance, a proper blast design can be chosen by trial methods implementing probabilistic analysis.

Condition monitoring of underground structures has always posed a challenge to researchers and maintenance engineers. There are many tools and methods available which sometimes becomes tedious when monitoring inaccessible locations. Electro-Mechanical Impedance (EMI) technique is a new condition monitoring technique which is proved to be efficient in detecting damages in reinforced concrete and steel structures in both local and global domains. There have been attempts of using this technique for monitoring rocks under various types of loading. EMI technique involves the deployment of smart piezo-based sensors like Lead Zirconate Titanate (PZT) patches on the host structure which is to be monitored. The present study highlights some numerical and experimental studies on PZT patch and rock interaction which are crucial for developing a monitoring system for rocks. A stage-wise analysis has been presented to develop a better understanding of bonding piezo sensors on rocks. The results of the analysis have helped in composing a method of bonding piezo sensors while taking care of the intricate details. The steps used in bonding have a significant effect on the recorded signals hence, influence the damage detection capability of the bonded piezo sensors.

Tunnels in rock are integral part of contemporary old and modern smart cities in hilly terrain to provide services and transportation. Tunnels have been the lifeline of the metropolitan cities since decades. Tunnelling have reduced the time of travel, saved money, reduced number of accidents and also reduced the human impact on the ecology of the hilly regions. Hilly regions are seismically active zones and have several minor earthquakes at a shorter span of time. Himalayan mountains are young folded mountains and have been affected by several earthquakes of large magnitude in last century. Hence, stability study of tunnels in hills is very crucial. This present study focuses on the effects of rock mass weathering, due to geological and other changes, on the stability of tunnels subjected to earthquakes. The 2D plane strain elastoplastic model has been adopted for the numerical analysis using finite element software. A model of dimensions 42 m x 42 m has been developed having an overburden of 500 m. The different shapes of the tunnel are also varied to understand their stability. Plasticity theory of failure given by Mohr–Coulomb has been incorporated to simulate the constitutive properties of rock mass. The physical properties of basalt have been adopted for this study. The different weathering classes of basalt used in this study are fresh basalt, slightly weathered basalt, medium weathered basalt and highly weathered basalt. The earthquake data of acceleration time history has been taken from the records of the Koyna earthquake, which was a 6.4 M magnitude earthquake. This study will help to understand the stability of the smart city tunnels subjected to the earthquake in hilly regions. This paper concluded that weathering has detrimental effects on the seismic stability of smart city tunnels. The deformations reduce by 34% with the increase in the depth of overburden in case of arch-shaped tunnels, in case of circular-shaped tunnels the deformations reduce by 42% and in case of horseshoe-shaped tunnels deformations reduces by 28% of deformations at shallow depth of overburden.

Rockfall is a geological hazard for highways and areas located in mountainous terrain. Analysis of rockfall is of major importance due to its effect on the transportation system, buildings, and various other infrastructure facilities. It is caused in the regions of high seismic activity or heavy rainfall. Determination of bounce height, kinetic energy, and translational velocity of a falling rock are necessary for the design of mitigation systems. This research work is carried out using numerical simulation program Rocfall 6.0 to determine the effect of rockfalls at four different sites in the Theng slope situated in Sikkim. The deterministic analysis is not able to incorporate the wide variability of the different geotechnical properties. Hence, considering the pitfalls of deterministic analysis, a stochastic analysis is implemented using Monte-Carlo simulation technique, considering the velocity of the moving block and coefficient of restitution as its input parameter. In this simulation technique, the truncated normal distribution is used and the coefficient of variation is considered approximately 10%. Finally, a sensitivity analysis of barrier system is performed. From this sensitivity analysis, the location, height, and inclination of the barrier are obtained.

Tunneling in jointed rock is always a challenge for the engineer on site, due to the existence of unfavorable lineages. The presence and orientation of fractures will affect the redistribution of stresses and any uncontrolled ground movement will induce additional loads on the boundary. Further the complexity arrives when two or more tunnels intersect each other, leading to more instability. Hence, discrete element modelling of Cross-tunnel was carried out considering, three tunnel shapes, i.e. D-shape, horseshoe tunnel with flat invert and horseshoe tunnel with curved invert. The analysis allowed the computation of the complete stresses and deformation patterns around the tunnel excavated in jointed rock conditions, comparing with Intact rock/continuum model. In discontinuum model (Jointed rock) model, in the vicinity of the openings, the surfaces are very much affected due to occurrence of tensile stresses and also, floor heaving and crown displacements were observed to be distinctive. This effect was relatively reduced for the case of horseshoe shaped tunnel with curved side walls and curved invert conditions.

Many hydroelectric, transportation, rail and metro rail projects are under construction in the country. The underground structures for these projects especially tunnels and caverns are mostly constructed on/in rocks. The presence of joints, shear zones and shear seams significantly effect the rock behavior under loading and unloading conditions. The shear zones and heavy seepage conditions pose challenging conditions for engineers and shall be handled in systematic manner.The paper presents the analysis of double lane tunnel of more than 9.5 m diameter in a poor & challenging geological conditions for a project, located in Northern India. The in-situ stress conditions are anisotropic in nature with major in-situ stress ratio of 0.55 and minor in-situ stress ratio of 0.45, thereby making the tunnel behavior complex. The three major joint sets along the tunnel alignment adds to the complexity of the problem. The stress-deformation analysis has been carried out using RS 2 software using Mohr–Coulomb model. The excavation has been simulated in two stages for the tunnel i.e., heading and benching. The analysis has been carried out, to decide upon the optimal support system for the tunnel. The wedge analysis is also carried out to find out the effect of intersecting joints along the tunnel alignment.Based on the stress-deformation analysis and analyzing the stress behavior, deformation characteristics and plastic zones around the tunnel, the optimal support system is decided and implemented at site. The support measures in terms of shotcrete with wiremesh/SFRS, forepoling, lattice girders and grouting are adopted.

Tunnels are important underground structures which require due attention at all stages of their construction process. This task involves huge expenditure and time. Hence, other factors which may affect the functioning of the tunnel in the long run must also be incorporated in the studies. With the growing demand of space for developing various facilities, the best possible way to economize the underground space is being looked after. The purpose of this paper is to study the tunnel behaviour addressing both issues of space and impact loading, i.e. twin circular tunnels running parallel to each other are analyzed under impact loading. Synthetic rock material is prepared in the laboratory and its engineering properties are determined. These properties are used to develop FEM model of the twin tunnel using ABAQUS to study stress and displacements induced in the rock model due to incidence of impact load. The point of load application has a major effect on the deformations in the tunnels. This effect is studied by considering two cases of point of load application on the top surface: (i) at the midpoint between the tunnels, and (ii) at the centre of one of the tunnels. Extent of damage suffered by the tunnels due to combined effect of rock strength, magnitude and application of impact load and overburden depth is quantified.

Physico-mechanical behavior of reservoir rocks in static condition of an oil field is critical to assess the stability of wellbore and other production related issues. Especially if the rock formation is anisotropic, the problem becomes more complex. An attempt is made in this paper to present test results of anisotropic Tipam sandstone from Digboi oil fields of Upper Assam, India under static conditions. The collected sandstone samples subjected to rock mechanics tests at different angles β = 0°, 30°, 45°, 60°, 90° were conducted. Also, high-pressure triaxial tests in static loading were conducted in dry and saturated conditions. The reservoir 1D and 3D Mechanical Earth model was carried out using Techlog and Petrel software from two wellbore data sets up to a depth of 2400 m to assess the wellbore stability incorporating anisotropy into consideration. The results indicate that the wells are critical at β = 45°, under saturated conditions. Necessary wellbore stability measures are recommended based on the results of Digboi oil field.

Tunnels are the underground passages used for transportation and other purposes. Tunnel lining adds the structural strength and saves the rock from air slakes. This paper contains study of ground conditions which includes variation in stratification and effect of ground water table. Based on these conditions of stratification and ground water the problem of deformation of tunnel and stresses developed on tunnel are solved considering field situations. For this purpose, 3D analysis is done by Midas GTS NX software. Various parameters of soil/rock such as porosity, cohesion, friction angle, Poisson’s ratio, Young’s modulus, Geological Strength Index, etc., have been used. Various cases tried for concrete lining and its effect on deformation is studied at key points of tunnel. By taking iterations and comparing results of all the cases, final conclusion is drawn. Thus, the soil structure interactive analysis for various conditions have been tried and results obtained at selected key points on the tunnel lining are tabulated graphically which are useful for the preliminary design of tunnel lining under appropriately selected conditions. This work is useful to the practitioners, design engineers, consultants, researchers, and construction professionals to decide the preliminary thickness of lining with certain approximations.

For site investigations pertaining to hydropower project(s), often the suitable in-situ testing protocols are limited in open terrains due to constraints in carrying out them on rock masses. Such scenarios necessitate the utilization of available resources to the best possible extent, in carrying out sampling procedures required for evaluation of design parameters like shear strength (concrete over rock; rock over rock) and deformability characteristics of rock mass. In order to carry out these tests, it is mandatory to get enough upward reaction for the expected structural loads (which are usually of higher magnitude), for better engineering judgements. These loads will have to be compounded to the conservative side, by at least 1.5–2 times of the expected design loads. In order to meet this requirement, particularly in drift areas (small audits), the crown reaction due to cover is sufficient. However, in most of the open terrains, the reaction is provided by relying on Kent-ledge arrangement by providing sufficient loading arrangement such as sand bags, concrete blocks, etc., a time taking process involving considerable risk. The current manuscript deals with instances encountered under difficult open terrains in carrying out required tests, and suggests suitable site specific solutions with available resources within the working area. The authors believe that, the proposed solutions presented in this manuscript will benefit the practicing engineers and stake holders working in the geotechnical investigations pertaining to in-situ rock testing.

In the Himalayan region, geology of rock mass is highly complex and fragile and hence excavation of large size underground structures in such a material is a very difficult job. Excavation of large size tunnels and caverns becomes safe if the condition of the ground is known a-priori. Knowledge of the ground condition will not only help in proper design of support system but will also help in keeping contingency plans ready before any untoward eventuality. It is therefore necessary to develop a simple framework that will predict the ground condition. In this paper, a unique multiple-graph based framework has been proposed for the preliminary estimation of ground conditions during tunneling through rock masses. This method has been established based on the estimation of three quantities in a logical sequence, viz., rock mass strength, competence factor, and finally the ground condition. A new empirical ground condition classification has also been suggested in this paper for both soft and hard rock masses. The proposed framework is validated by applying it to five tunnel sections from Sawra-Kuddu Hydroelectric Project in Himachal Pradesh, India. The proposed framework is an efficient tool for quick prediction of ground condition in the preliminary stages of design as well as during the excavation of tunnels.