Foundation and Forensic Geotechnical Engineering

The present investigation proposes a suitable pile foundation system for a horizontal solar axis tracker (HSAT) to be constructed at Kutch, Gujarat. The analysis is carried out based on the soil properties obtained from ten different borehole locations. Considering the economic viability and duration of the project, two types of pile foundations, such as bored cast in-situ and driven piles, are proposed. The optimum geometry of the pile foundation (length and diameter) for different boreholes under various loading conditions is obtained using the recommendations of the Bureau of Indian Standards and Brom’s theory. Further, the recommended geometry of the piles is modeled in the commercially available finite element software PLAXIS 3D with the actual soil and pile parameters. The results obtained from the theoretical and numerical analysis are compared to obtain the safe and economical design of the pile foundations for the proposed HSAT system. Since the project location falls under the active seismic zone (Zone V), the pseudo-static analysis is conducted to provide a better insight into the performance of the proposed foundation system under the seismic condition. The lateral load is found to be the critical parameter in the design of the piles. The performance of the driven piles is found to be better in silty sand compared to the bored cast in-situ piles.

For the past three decades, a novel technique for bored pile static capacity evaluation using the bidirectional static load test (BDSLT or O-cell method) has been proven beneficial to the traditional axial load testing method in various aspects. Nevertheless, as the BDSLT method uses a loading mechanism within the pile, completely different from the top-down pile loading testing method, many researchers and designers have been concerned that the BDSLT method would give an inaccurate result. This paper focuses on the comparison of both testing procedures using load test data to give confidence in the piled foundations of soil. In order to assess the validity of both testing methods in soil conditions, pile load tests were performed on two 1500 mm diameter cast-in-place concrete piles of 26.0 m long to a test load of 20,900 kN under the same geotechnical conditions in Kuwait. Geokon model 4200 strain gauges were installed on the piles at six designated locations with four numbers at each level. Based on the analysis, it is confirmed that both methods are accurate to assess the pile settlement at the design and ultimate test loads. Hence, it is identified that BDSLT is an innovative, feasible replacement of the conventional static load test to determine the static behavior of bored piles to ensure a safe foundation system in the construction industry.

The ring footings are usually adopted as a foundation for a structure having circular geometry. Generally, the bearing capacity of ring footing is evaluated either experimentally or numerically for different radii ratios. The radii ratio (r_i/r_o) of the ring footing is defined as the ratio of inner radius (r_i) to its outer radius (r_o). The bearing capacity of the ring footing having flat base is found to be optimum for radii ratio from 0.25 to 0.35. However, the effect of inclined base on the bearing capacity of the ring footing is not examined. In this study, the effect of inclined base on the bearing capacity of the ring footing is evaluated using finite element (FE) analysis. The vertical bearing capacity of the ring footing with varying base inclination (≤0, 5, 10, 15°) and different radii ratio (r_i/r_o = 0 to 0.75) is evaluated. The bearing capacity ratio (BCR), defined as ratio of ultimate bearing capacity of ring footing with inclined base to the flat base, corresponding to different radii ratio and varying soil friction angles is evaluated. Based on the FE results and comparison made in the study, future direction is drawn on evaluation of bearing capacity of ring footing.

Geotechnical design standards are the basic and most important tools for geotechnical design of foundations. Diversities and commonalities of codal provisions between countries occur worldwide. This paper attempts to carry out a comparative study of Indian and Eurocode Standards for design of foundations. The scope of this paper is limited to comparison of geotechnical design principles and practices of spread and pile foundations as per Indian and Eurocode 7. The relevant Indian Standards for Spread and Pile Foundations like IS 1904, IS 6403, IS 2911, IS 8009, IS 12070 and European Standard Eurocode 7 are considered. Design examples on estimation of bearing resistances as per Eurocode 7 and Indian Standards are also discussed in this paper.

This paper presents a parametric study conducted numerically for large piled rafts on stiff clay. The pile number, pile length, pile spacing and raft thickness effects were evaluated on the behavior of large piled rafts in terms of the differential and average settlements, bending moment of the raft and load sharing. The configurations of piled raft adopted in the study ranged from 5 × 5 to 13 × 13 piles distributed uniformly underneath the raft. The pile length was varied between 10 and 30 times the diameter of the pile. The pile spacing effect was observed for any piled raft configuration such that the area enclosed by the pile group underneath the raft varied from 0.2 to 0.9 times the raft area. The raft thickness was varied to ensure that its stiffness changed from flexible to intermediate and to rigid. Results of the study show that average settlement reduces with increment in pile number and pile length. The differential settlement decreases as raft thickness increases but at the cost of higher bending moments. The addition of piles is not beneficial in reducing the bending moments when compared to an unpiled raft. With an increase in the number of piles and pile spacing, there is an increment in the load the piles carry. For the same pile number and pile spacing, linear increment of the loads the piles carry was observed with increasing pile length.

Pile foundations are often used to transfer axial loads through shaft and base into deep soil strata in which the pile–soil response is nonlinear and difficult to predict. The testing of large bored piles by using conventional kentledge is difficult and uneconomical. Instead of testing with Osterberg (O)-cell is being used in recent times, in which the load application is bidirectional. The upward load application is against the gravity and is resisted only by the shaft and in the downward direction is resisted by both shaft and base resistances for O-cell placed at some depth from top. In this study, a simple approach is proposed to analyze the load versus displacement curves obtained for both upward and downward responses. Ultimate resistances and initial stiffnesses of shaft and base are estimated from the downward load–movement curve and ultimate resistance and initial stiffness for the shaft response only is obtained from the upward load versus movement curve by Chin’s method assuming nonlinear hyperbolic responses for both. The proposed method is applied to a few available O-cell test data. Initial shaft stiffnesses, ultimate shaft resistances and percentage variations for the two sets of results for both directions were obtained and compared. This study helps the designers to predict the O-cell pile responses better and validates the initial design.

3D finite element analyses were conducted to understand the performance of large piled-raft foundations on sand by considering the influence of geometric parameters like the spacing and length of piles, and thickness of raft on differential and average settlements, bending moment and load sharing ratio. The piled-raft with 4 × 4 pile configuration and pile length and pile spacing varying from 20 to 50 and 4 to 16 times the pile diameter, respectively, were considered for the study. The raft thickness was varied such that its stiffness ranged from extremely flexible to extremely rigid case. It is observed that for all the considered pile lengths, with increase in spacing of pile, differential settlement initially decreases and attains a minimum value, and thereafter, it increases. For any pile length, the change in average settlement with pile spacing is negligible. The increase in the load sharing ratio with increasing pile length is not found to be significant for higher pile lengths. For thicker rafts, the differential settlement becomes negligible at all pile spacing. However, for lower raft thickness, differential settlement initially reduces for lower pile spacing and then increases for higher spacing of pile. For lower spacing of pile, the average settlement increases with increase in thickness of raft, whereas for higher spacing of pile, there is no significant change in average settlement with variation in raft thickness. With increase in the thickness of raft, raft bending moment increases but it does not affect the load taken by piles significantly.

Most theories of bearing capacity of foundations on or in ground are based on the assumption that soil is incompressible and its stress–strain behavior is rigid-perfectly plastic following Mohr–Coulomb failure criteria. Menard (1957) proposed a theory for estimation of limit pressure for pressure meter that incorporates compressibility of soils in the form of rigidity index, \(I_{\text{r}} = G/c_{\text{u}}\) (ratio of shear modulus to undrained shear strength of soils). Vesic (1973) derived compressibility factors for cohesive–frictional soils for the estimation of the ultimate bearing capacity of footings. The present study focuses on the variation of bearing pressure factor \((N_{{\text{cf}}} = q/c_{\text{u}} )\) for circular footings on soft ground with settlement, for a wide range of rigidity indices \((I_{\text{r}} )\). Finite element axisymmetric analysis is carried out to evaluate the bearing pressure, q, versus settlement responses for circular footings for a range of \(I_{\text{r}}\) from which \(N_{{\text{cf}}}\) is obtained at different settlement ratios (SR). Perfectly rigid plastic response, i.e., incompressible soil is achieved for \(I_{\text{r}} = 5000\) at SR of 0.25%. Normalized \(N_{{\text{cf}}}^{\prime}\) (ratio of \(N_{{\text{cf}}}\) of compressible soil to that of incompressible one) are derived as function of rigidity index, \(I_{\text{r}}\) for different normalized \({\text{SR}}^{\prime}\) (ratio of SR of compressible to incompressible soil).

Raft foundation for a 35-storeyed residential tower in Noida bearing on alluvial soils was analyzed using PLAXIS 3D software to assess the pressures and settlement at foundation level. To develop realistic geotechnical parameters to input into the finite element model, the borehole data were supplemented with in-situ pressuremeter tests and cross-hole shear tests. Using the updated soil parameters, the soil–structure interaction analysis justified the use of raft foundation without the need for piles.

With substantial increase of industrialization, large quantities of toxic waste remain untreated, which is a serious geo-environmental issue. Pile foundation is being extensively used at many such sites to support weak soils, where the load transfer mechanism is either through skin friction, end bearing, or both. The present research paper focuses on influence of contamination on load–settlement characteristics of RCC model pile foundation for two different slenderness ratios (8 and 10) by carrying out experimental model test on both contaminated and non-contaminated soil subjected to various load inclinations (0°, 30°, 45° and 60°) from vertical axis. Various parameters analyzed and compared in this study are ultimate inclined bearing capacity, deflection, moment, soil resistance (p), engineering properties of soil, mineralogical content of soil and effect of lateral component on inclined bearing capacity. Various theories are used to estimate vertical and lateral capacity of the pile. P–Y curve is also constructed and used to calculate deflection, moment and soil resistance for the applied load. Experimental result of the model test is compared with the inclined capacity calculated using Meyerhof’s interaction equation. This investigation has revealed that contamination of soil leads to reduction in the bearing capacity. Also, there is a direct correlation established between increase in angle of load inclination with reduced bearing capacities, and increase in L/D ratio with increase in bearing capacities of pile.

When the raft settlement exceeds allowable values, the application of piled-raft foundation is more common. Nowadays, combined piled-raft foundation gives a greater effectiveness in load sharing when it is subjected to vertical loads. But when the narrow building is subjected to wind or seismic load with some eccentricity, it can tilt the building permanently. To minimize this problem and to increase the stability of the building, combined piled-raft foundation gives a wider solution. In present study, an effort has been made to examine the piled-raft foundation subjected to eccentric load by 3D finite element modeling through ABAQUS software. The analysis was made by changing soil’s Young’s modulus in different layers, and it is found that load carrying capacity of piled-raft foundation is greatly affected by pile spacing to diameter ratio (i.e., s/d = 3, 4, 5) and eccentricity ratio (i.e., e/B = 0, 0.1, 0.25, 0.4). The load versus displacement curves for piled-raft systems are assessed and effects of different pile group configurations such as 3 × 3, 4 × 4 and 5 × 5 on load carrying capacity are observed. Further, in case of eccentric loading, the load transfer behavior of the applied load in both piles and raft are also evaluated. From the load displacement curve, it is observed that the load carrying capacity of piled-raft foundation increases when the spacing between the piles increases in the piled-raft foundation as the group interaction effect is reduced in this case.

This paper deals with the shape optimization of onshore wind turbine foundations. The importance of renewable energy is gaining importance globally. Onshore wind energy gained importance in countries with potential to generate renewable energy due to reducing the use of other non-renewable energy sources. The aim is to study different shapes configurations of onshore wind turbine foundations. Variables considered in the study are shape of the foundation, wind load and various angles of application of wind load. Simulation and analysis were carried out using STAAD Pro software to determine the forces on the foundation, while soil behavior was analyzed using PLAXIS 3D to better understand settlement behavior. A comparative study was carried out to check the parameters such as resultant forces, volume of materials concrete and steel required, settlement and strain characteristics of soil and safety factors. The most preferred configuration is a circular shape based on the variables and parameters considered in the study, but considering the ease of constructability, the configuration recommended is octagonal which is practical for onshore wind turbine applications.

The external load acted upon the piled raft is divided between the piled raft components, i.e., piles and the raft present in the piled raft system. But such perception of load distribution does not include interactions among the raft and the piles or among all piles present in a group, and in order to involve such interaction nature, some researchers have presented a load distribution coefficient. Therefore, the major goal of this study is to measure the load distribution coefficient for the piled raft system through numerical modeling. To comprehend the effect of various parameters on the load distribution coefficient, the raft width, number of pile, pile spacing-to-diameter ratio and thickness of clay soil to pile embedded length are altered. The profiles of load distribution coefficient for different design variables are presented in this study, and it can be found that the load distribution coefficient maintains a nonlinear profile with the normalized settlement of the piled raft system, where the load distribution coefficient increases with the increase in the normalized settlement by following a power law. Considering all the model configurations, it is observed that the range of load distribution coefficient \((\xi_{{\text{PR}}} )\) varies between 0.75 and 1.11. This phenomenon indicates that the \(\xi_{{\text{PR}}}\) mostly has a negative effect on the piled raft system. Due to this negative influence of the load distribution coefficient on piled raft system, a proper valuation of this coefficient is very much essential before designing any piled raft system.

In this article, a numerical study is presented to estimate the capacity of the strip foundations located on undrained clay slopes and subjected to the combined action of V-H or V-M loadings. A series of ‘Probe’ analyses is performed using OptumG2 (a finite element limit analysis package) for 2D plane-strain soil slope models with different inclinations, to develop the V-H and V-M capacity envelopes considering both lower- and upper-bound solution. To understand the effect of slope inclination on the capacity envelopes of foundations on slopes, the results are compared for the same foundation located on flat ground. The vertical capacity of foundations on the slope (β = 40°) was significantly reduced (≈15%) as compared to the same foundation on flat ground. It was observed that the V-H capacity envelope of the foundation on the slope was more asymmetric as compared to the asymmetry in the case of V-M capacity envelope. These capacity envelopes of the foundation on slopes help to further understand the possible failure mechanism of the foundation-slope system.

Pile foundations are very common in use for multi-story buildings having complex shapes, sizes and loading patterns. Thus, it is extremely important to estimate the foundation behavior under dynamic loading to avoid any catastrophe and/or failure of serviceability conditions. In view of that, the present study is envisaged to investigate the behavior of pile foundations of symmetric and asymmetric buildings under earthquake load. The study has performed the displacement analysis of piles with different configurations as mentioned including the pile length. For this purpose, a seven-story building is modeled in different symmetric and asymmetric configurations (shapes). The behavior of piles, positioned along the periphery of superstructure, is monitored based on different parametric variations. A finite element software, PLAXIS 3D, is used for this investigation program. The pseudo-static method is adopted to determine the displacement of piles under dynamic loading conditions. Responses of piles, along the depths, are monitored by gradually increasing the horizontal acceleration. It is found that pile displacements at various depths in symmetrical buildings (e.g., square and/or rectangular shapes) are higher than unsymmetrical buildings (e.g., ‘E’, ‘L’ and ‘T’ shaped, etc.) under similar horizontal acceleration. Further, it has been noticed that displacements of individual piles at various depths for a symmetrical building are the same; while it is different for an asymmetrical building.

In general, the pile foundations have extensive applications, and predominantly, pile is using at a place where large axial forces are transfers between superstructure and ground. In some cases, like an earthquake zone, liquefaction zone, structures in a massive wind zone, retaining structures, to increases the slope stability, etc., the primary role of the pile is to transfer both vertical and horizontal (lateral) forces. Based on the different applications of the pile foundations, it is showed as the study on the responses of the pile foundations due to axial and lateral forces are equally important. Many works of literature are available for the analysis of pile responses due to axial force, lateral forces and their combinations. The literature also indicates a lack in the studies of pile behaviors due to lateral soil movements, especially lateral soil movement due to the surcharge load. This present study is about the lateral responses of a free head pile in homogenous sandy soil medium at slope crest, under the influences of varying surcharge loads, ground slopes and relative densities of soil. Consider the varying surcharge loads at two different locations (A and B) with a constant span of 5 m to study its effects on the pile. The loading position A starts immediately from the end of the active wedge, and the loading position B starts from 10 m away from the end of the active wedge. Both the surcharge loading positions will ensure with and without interactions between the pressure bulb of surcharge loads and active wedge. This study considers the varying ground slope as (1V:1.5H, 1V:2H and 1V:2.5H) and relative densities of soil as 70%. Develop the two-dimensional finite element models with standard fixities boundary conditions in PLAXIS 2D and calculating the lateral responses of the pile at slope crest (bending moment and deflections) by considering various lateral forces (surcharges load and ground slopes) on it.

The structural design of a foundation depends upon the internal stresses developed in it at various conditions of loading and support. This paper investigates the influence of flexural rigidity of the footing and shear strength of underlying soil on the internal stresses developed in the foundation, by carrying out a series of laboratory scale loading tests on model footings supported on granular soil. A flexible model footing is fabricated with GI sheet of dimension 100 × 50 × 2 mm. The flexural rigidity is increased by fixing stiffeners of 2 mm diameter steel rods. The shear strength of supporting granular soil is varied by mixing fly ash at various proportions. The load–settlement behavior and the increase in curvature of footing with applied stress for various cases are determined from laboratory scale load tests. Finite element analyses are carried out with the software PLAXIS 3D, and the results are compared with those obtained from laboratory scale load tests for validation. The internal stress in footing is determined analytically from the measured curvature in laboratory scale load tests and numerically from finite element analyses. It is observed from the results that the internal stress distribution in a foundation is considerably influenced by the flexural rigidity of the footing and shear strength of supporting soil.

The contamination of soil due to accidental spillage of oil happens quite often along highways connecting petroleum refineries. Many accidents of overturning of trucks in these highways have been reported in the recent past. Oil contamination can also occur due to exploded oil well, destruction of oil storage tanks, breakage of pipelines, etc. During these spillages, the oil will permeate into the ground and the engineering properties of soil get altered. Many researchers have investigated the influence of varying percentages of contamination on the engineering properties of soil. This paper investigates the influence of oil spill on the load–settlement behavior of footings of adjacent structures. The influence of eccentricity of the point of spill, quantity of oil spill on the load–settlement behavior and tilt of footing is investigated through a series of laboratory scale load tests. The relation between the quantity of oil spill and the extent of contamination, oil content at various distances from point of spill, etc., are determined experimentally. It is observed that the tilt of footing and variation in load–settlement behavior is significantly influenced by the quantity of oil spill and distance between the point of spill and footing. Based on the results obtained from experimental studies, the extent of damage occurring to a footing due to a nearby oil spill has been quantified.

Three-dimensional FE analyses using PLAXIS 3D have been carried out to study the behavior of single vertical and battered piles under combined action of axial and lateral load in different homogenous non-cohesive soil conditions. The variation of ultimate lateral load with pile head deflection with and without axial load has been obtained to examine the effect of friction angles (ϕ) of sand and batter angles of pile (β) on the ultimate pile capacity. Results indicate that the axial load, pile batter angle and sand friction angle significantly influence the lateral response of battered piles. Under the influence of axial load, P (=0.2 P_u, 0.4 P_u, P_u being ultimate axial load), the percentage increase in lateral capacity (I_H) increases with the increase in pile batter angle, β. For a negative battered pile, I_H values are almost same for both medium and dense sands. While for positive battered piles, in case of dense sands, I_H varies considerably with friction angles of sand, reaching a value of 44% for β = 20°. Further, a multiple linear regression equation, with R² value = 0.921, has been developed using MS-Excel with lateral capacity (H) as response and angle of internal friction of sand bed, ϕ (=a), diameter of pile (=b), the ratio of P/P_u (=c) and batter angle, β (=d) as predictors. The variation of results predicted by the regression model and that computed from the numerical model are found to be within 25%.

Many previous studies analyzed the footing resting on cohesionless soil slopes. The present study focuses on determining bearing capacity on clayey soil slopes through the finite element method associated with limit analysis. The soil consistency has been varied from soft to hard. The bearing capacity and slope factors representing the slope effect on bearing capacity are presented in the study. The bearing capacity factor enhances with an increase in the soil strength, footing depth and setback. The slope factor increases with setback and reduces with footing depth and slope inclination. The increase in bearing capacity with footing depth is relatively less visible in the sloping ground than level ground. Contrary to this, the increase in bearing capacity with soil strength is more visible on slopes.

Analysis of laterally loaded piles is a relatively complex, but very important part of pile foundation analysis. Generally, the methods of solution related to laterally loaded long piles are based on the popular ‘subgrade modulus’ approach. Design codes currently used for design of offshore piles prescribe for analysis based on nonlinear ‘p-y’ data, which is essentially the ‘subgrade modulus’ approach. The ‘p-y’ data represent the stress–displacement relation of soil when stressed laterally. Relatively, simplified analyses are also carried out for lateral loading of piles which require the application of appropriate subgrade parameters. However, difficulty often arises while carrying out simplified analysis in the selection of appropriate subgrade parameter η_h, which is the coefficient of variation of the modulus of horizontal subgrade reaction or constant of horizontal subgrade reaction. The results of simplified solutions may vary significantly when compared with results of analysis using detailed ‘p-y’ data if inappropriate values of η_h are used in simplified analyses. To examine the issue and calibrate the parameter η_h, analysis was carried out for steel tubular piles embedded in normally consolidated clay using nonlinear ‘p-y’ data and the equivalent values of η_h were back-calculated for use in relatively simplified approaches. The ‘p-y’ data for clays were derived for static loading following the procedure given by the international code API RP 2GEO (American Petroleum Institute: Geotechnical and Foundation design Considerations, API, Washington, DC, 2014, [4]). Based on the study, appropriate values of η_h were calibrated using relatively simplified methods. It is shown that results of simplified solutions match very well with the results of the more detailed analysis when appropriate values of η_h are used. Further, the degradation of the values of η_h with increasing lateral load in pile was also examined. Based on the study, the range of appropriate equivalent values of η_h is suggested for use in similar pile–soil conditions for static lateral loading of pile.

Full-scale pile load test is the most common approach to validate theoretical pile capacity. Static load testing of foundation piles is still considered as the best way to assess load carrying capacity of piles. Application of rate of loading, time increment or imposed displacement is the key factors for various testing methods. Sometimes, it is not possible to test the pile up to the failure; often pile does not reach ultimate pile capacity under the applied load. Applied load and measured pile head movement are to be examined during the entire test especially for axial pile load test. Challenges faced during installation and testing of a large diameter pile simulating marine conditions are covered in this paper. Reaction frame of 3600 T connected to four large diameter piles is designed as kentledge for pile load test, in the present case. This paper also illustrates pile installation challenges, simulation of marine conditions on land, importance of base cleaning, key aspects of reaction frame set up, discussion on test results and practices adopted in conducting large capacity pile load test.

The rock-socketed piles are large diameter bored piles socketed to bed rock that are widely adopted foundation practice to carry heavy axial and lateral loads. It is a usual practice to neglect the effect of soil cover during the design of axially loaded rock-socketed piles. Unlike, the axial load case, the depth and nature of soil cover is found to have significant role in the behavior of rock-socketed piles when subjected to lateral loading. In this work, a numerical analysis conducted in finite element tool, ABAQUS, on laterally loaded rock-socketed piles is presented. The finite element model was validated using an experimental study found in literature. Further, a detailed parametric study was carried out to investigate the influence of depth and shear strength parameters of the soil cover on the lateral load response of rock-socketed pile. For short and moderate length piles considered in this study, the geometric parameters such as soil cover depth, socket length, and ratio of soil cover depth to socket length were found to have profound effect on the lateral load response of rock-socketed piles. The effect soil cover depth was also found to be relatively independent of the shear strength characteristics of soil.

This paper confirms that the foundation system of the Taj Mahal consists of wells, arches and piers constructed from stone blocks, bricks, water tight mortar and some local materials. However, there is a dearth of construction information available for comparison between then and now. This paper has extracted data from available literature for conducting the forensic analysis of the Taj Mahal foundation wells. The foundation capacity is evaluated. The possible triggers for failure of foundation are discussed. Some techniques required to conserve the monument in the future are also discussed. The settlement of the foundation has already occurred as per previous research. Yet the Taj minarets continue to tilt outward. This paper concentrates on the present foundation bearing capacity considering the pile–raft action of the foundation which is inadequate. Air and river pollution can hasten the degradation of the foundation.

Heritage Impact Assessment (HIA) is engineered way to quantify the possible risk to the heritage structures and sites from the proposed construction activities nearby. A case study on the evaluation of HIA of the proposal near the heritage structures David Yale and Joseph Hyner’s Tomb, which is under the protection of Archeological Survey of India (ASI), is reported in this paper. The proposal consists of the demolition of the old law college building and auditorium located in proximity of the monument and the construction of the subordinate court complex around the monument. The case study addresses the concerns of the demolition and the proposed new construction and the impact it may have on the value of the heritage site and the structural stability of the monument. The HIA is carried out based on the proposal assessment, value assessment and structural risk assessment comprising of condition assessment, vibration assessment and soil settlement assessment. From the structural risk assessment, it can be concluded that the monument is in a high risk due to demolition of the abandoned old law college building near the monument. Therefore, the demolition and construction nearby may require mitigative measures. Considering the risk factor, the mitigative measures to be followed during the demolition and proposed construction are suggested. The recommendations are provided to increase the cultural and aesthetic value of the property and to make it an environment-friendly project.

Rainfall-induced landslides are a potential threat to the communities that live in tropical and subtropical hilly regions. The reduction in soil shear strength due to decreased negative pore-water pressure during infiltration is the major cause of these slides. The presence of vegetation alters the hydrological and shear characteristics of the slope. A numerical study was undertaken on the influence of various vegetation (root depth, soil cover fraction, potential evapotranspiration, leaf area index) and climatic factors (temperature, relative humidity, wind speed) for a past landslide in East Khasi district of Meghalaya, India 2019. The study caters the effects of evapotranspiration and root water uptake by vegetation. The numerical analysis results showed an improvement in factor of safety (FOS) due to vegetation consideration and accurately predicted the landslide. A parametric study was performed with different vegetation parameters. The root depth influence was critical; as the root depth increased, the FOS increased for a given slip circle. The effects of temperature, relative humidity and wind speed controlled the evaporation flux and played a significant role in net infiltration flux during a prolonged period but were negligible during a critical rainfall event. The study area had a vegetation cover with pine trees with a shallow root depth (~1 m) compared to other indigenous flora. These can also be an effective factor to the landslide occurred.

Two molasses tanks of each 24 m diameter and 9.7 m high were built in the premises of Sugar Complex and Cogen Plant at Tumkur village, Shahpur Mandal, Yadgir dist., Karnataka. A 24 m diameter base slab of one of the molasses tanks was failed during erection of the steel tank and the other one started failing during the hydrotesting. To identify the factors that caused failure of base slab, an investigation was carried out by going through the site conditions, drawings and specifications of the work execution. The natural ground level (NGL) in the tank area is varying from 2.6 to 3.8 m deep from filled-up ground level (FGL). The tank finished floor level (FFL), i.e., top level of base slab of tank is 0.75 m above the filled-up ground level. A 24 m diameter RCC base slab of 150 mm thick was resting on a 350 mm circular RCC wall having 1.85 m strip footing and also on a central steel I Section (ISLB 350) having a square footing of size 2.15 m. The measured top surface levels of the failed 24 m diameter slab are same at the edge and central support portions, i.e., 366.875. In between edge and central support portions, the levels are 366.72 and 366.65. There is about 200 mm sagging noticed in the slab between the portions of edge and central support. In this paper, the reasons of failure of base slab are discussed based on the geotechnical investigations carried out in the filled-up ground within and outside the tank area. The natural ground possesses the required design bearing capacity, but the filled-up ground was not compacted as per the specifications furnished in the design report.

This paper discusses the application and features of driven spun piles and reviews the challenges that are faced in the geotechnical design and site execution of the same. The geological challenges faced are varying estuarine geological conditions, negative skin friction, underlying weaker layer and susceptibility to liquefaction. The paper details about each of these challenges, its cause and the economical design approach to be adopted. An economical design approach without compromising the conventional conservative design can be arrived at by modifying the geotechnical design of piles based on the project risk and the reliability of geotechnical investigation.