Proceedings of the Indian Geotechnical Conference 2022 Volume 10

Metro construction in congested urban areas often involves the excavation of new tunnels. Tunnel construction induces the ground settlement above and the prediction of greenfield settlement is well established for homogeneous soil conditions and can be estimated using semi-empirical or numerical modeling. This paper investigates the influence of ground surface settlement caused by tunnel construction in layered soil on existing structures using numerical modeling. The numerical modeling has been done by keeping the soil condition similar to the actual scenario with multi-layered soil like clay, silt and sand. The numerical method is validated by comparing it with the field settlement values. The study illustrates the results for two varying parameters such as the centre-to-centre distance between tunnel and loading of structure. The results show that the effect of tunnelling on the foundation lies within two times the tunnel diameter from the centre line of the tunnel and the displacement beneath the foundation increases with increasing the surcharge.

The self-weight consolidation behavior of slurries like dredged clay and mine tailings is governed by the finite-strain consolidation theory. This theory considers the hydraulic conductivity and compressibility of slurries as functions of the void ratio. The determination of these material functions is essential for understanding the settlement behavior of the concerned materials which is necessary for the safe and efficient disposal of these materials. The experimental procedures for the determination of these functional relations need elaborate setups and are time-consuming. Therefore, it is convenient to adopt methods based on numerical techniques for this purpose. In this paper, an inverse analysis method is proposed for the estimation of hydraulic conductivity function parameters from the settlement versus time behavior and initial conditions of slurry materials obtained from the settling column test. The finite difference solution of the governing equation for finite-strain consolidation was used for the forward analysis. The inverse analysis was carried out using Particle Swarm Optimization (PSO) algorithm combined with a gradient-based optimization algorithm fmincon. The method was tested using the synthetic settlement response of two slurries. The shortcomings of fmincon and PSO algorithms were discussed. The proposed method of back analysis estimated the hydraulic conductivity function parameters accurately when the compressibility function is known and is assumed to be time-invariant.

Black cotton soil is a problematic soil in the field of construction due to its poor shear behavior. The main objective of this study is to analyze the shear parameters of reinforced black cotton soil numerically using SIGMA/W in the Geo Studio tool. The study has been carried out to investigate the shear parameters of considered soil for different layers of reinforcement. The necessary boundary conditions have been applied for the numerical model. The numerical analysis has been performed considering various stresses and forces such as deviatoric stress, vertical stress, confining stress, and backpressure. The result in terms of effective stress, major principal stress, minor principal stress, total stress, and pore water pressure is obtained. The results obtained from numerical simulation are compared with those of the experimental studies of black cotton soil. This study shows that the results are within the marginal limits.

Rate-dependent shearing response of sand has been of major concern for several geotechnical applications related to dynamic compaction, mine blasts, pile driving and rapid load testing of piles, etc. In this regard, transient laboratory tests indicate that the mechanical behaviour of sand may vary significantly when the applied strain rate ranges from 10–5/s to 1/s or even higher. Such rate-dependent response of sand depends on the employed strain rate range along with sand morphology, stress and density state. In the present study, a recently proposed elastic-visco-plastic model by Mukherjee et al. (Mukherjee et al. in Acta Geotech 16:93–111, 2021) has been adopted for the assessment of rate-dependent mechanical behaviour of three different types of sand, i.e., crushed coral, silica and Toyoura sand. The predicted rate-dependent shearing response has been noticed to be in close agreement with the experimental observations from literature and the employed model aptly captures the rate effects in different sand types by altering the appropriate model parameters. All the three sand specimens have been subjected to the drained triaxial shearing at a same density and confining pressure, and the rate-induced strength enhancement has been assessed in terms of peak shear stress, peak friction angle and axial strain at peak.

The large disposal problem of fly ash can be minimized by using it to the maximum possible extent in the various geotechnical fields. When it is used in geotechnical applications such as the construction of ash dykes in earthquake-prone regions, maintaining its stability becomes a major concern because earthquake-induced instability can cause large lateral spreading of the ash material. Due to the inertia of height-raised ash dykes, earthquake generates significant horizontal and vertical forces. This allows the amount of particulate material to decrease its volume, causing a rise in pore pressure, and a decrease in the strength of the soil, leading to partial or complete collapse of the ash dykes. Mitigation of this problem requires a profound understanding of its dynamic behavior. In addition to this, different methods of raising ash dyke largely affect the performance of dyke during a seismic event. A dynamic response study and an analysis of the developing instability, which can be described in terms of amplification or displacement, are necessary for evaluating the performance of ash dykes under seismic loading circumstances. In this study, the suitability of the methods of raising ash dyke is proposed under the dynamic conditions. Efforts are made to perform dynamic response analysis of ash dyke by determining the amount of displacement and amplification in the ash dyke when it is subjected to earthquake motions. From dynamic response analysis of the ash dyke, it is obtained that the earthquake-induced displacement of the dykes can be as high as 4–5 m, and in the staged construction of ash dyke, upstream method of construction may not be a good alternative to be used in the earthquake-prone regions.

During intense earthquakes, numerous structures crumble due to the severe damage inflicted upon their substructures when the soil loses lateral support owing to liquefaction induced by the seismic activity. This study delves into the nonlinear characteristics of individual piles in sandy terrain caused by liquefaction triggered by earthquakes, employing 3D nonlinear FEM models via Opensees. Various thicknesses of single piles are examined with ground slightly inclined. The ground motion input consists of sinusoidal acceleration at a frequency of 2 Hz and amplitudes varying from 0.2 g. The data collected from sensors for both individual piles and pile groups are scrutinized for displacement, bending moment (BM), and excess PWP. Through this sequence of experiments, it’s noted that majority of the highest lateral loads on the piles occur during initial phases of lateral deformation, as excess PWP progress towards liquefaction. Subsequently, lateral loads appear to diminish for the liquefied stratum. It’s observed that the BM of piles in liquefiable areas considerably rises compared to non-liquefiable areas due to the loss of lateral support from the liquefied soil. Moreover, it is discovered that displacement at the pile base in saturated terrain is relatively minimal.

Geotechnical Engineering largely focuses on the complex nature of soils and rocks. Because this complexity creates a high level of ambiguity in the imitation of these materials’ nature. Genetic Programming (GP) has been initially developed by Koza (Genetic programming: on the programming of computers by natural selection. MIT Press, Cambridge (MA), 1992) and then used by many researchers in different areas including geotechnical engineering. This paper closely reviewed the application of GP in some areas of geotechnical engineering identified: settlement of the shallow foundation, bearing capacity of pile foundation, liquefaction assessment, estimation of pore water pressure, compaction parameters (OMC & MDD), soil-fiber composite assessment, free swell and swell pressure, the effectiveness of rolling dynamic compaction, prediction of soil water characteristic curve, and unconfined compressive strength (UCS). GP has been getting success over the years, because of its ability to find the relationship between the input variable and predict the output variable. This paper also discusses the future scope of GP in some unexplored areas of geotechnical engineering.

During the process of shearing, deformation of granular materials like dense sand is often noticed to concentrate within a narrow zone, commonly referred to as shear bands. Various studies show that the formation of shear band is influenced by the internal inhomogeneity of the granular assembly. Owing to various ways of specimen generation, internal inhomogeneity arises in sample while performing laboratory experiments or carrying out micromechanics-based simulations employing discrete element methods (DEM). Hence, understanding the effect of inhomogeneity, resulting from such sample generation techniques, on the formation of shear bands becomes imperative. In the present study, DEM-based biaxial test simulations have been performed on the dense sand specimens, which have been prepared following two sample generation techniques. Biaxial shearing of these specimens has been conducted by adopting a stress-controlled flexible boundary. It has been noticed that dense specimen shows buckling and bulging-type deformation accompanied with the formation of localized shear bands. The initiation and propagation of persistent shear bands have been analyzed from the spatial variation of porosity and particle rotations within the specimen. The position of shear band within the specimen differs due to presence of different initial inhomogeneity within the particle packing arrangement arising due to variation in the specimen generation process.

Machine Learning can be successfully utilized in geotechnical designing applications, where vulnerability is a portion of nature, to create a vigorous predictive model foundation for designing parameters/behaviors. Formerly, geotechnical plan parameters were not continuously straightforwardly measured from a research facility and in-situ tests or maybe frequently assessed from observational or numerical relationships that are created from regression fitting to a dataset. ML models were created to train a nearby dataset. The developing volume of data databases presents openings for progressed information examination methods from machine learning inquiries. Applied applications of ML are exceptionally distinctive from hypothetical or observational studies. The feasible applications of ML were examined and created a proposition for a seven-step preparation that can direct viable applications of ML in design. In this work, an ML model was developed to predict pile behaviors based on a cone penetration test (CPT). The ML model was used to develop approximately 500 data sets from the available literature. The ML model beats the conventional techniques when the predictions made by ML are compared to those provided by several conventional approaches in the study.

Over the past few decades, several researchers have suggested adequate experimental and numerical approaches to calculate the granular anchor piles’ (GAPs) uplift capacity in expansive soils. There haven’t been many studies done on the uplift potential of GAPs in loose sands. The outcomes of numerical analysis using PLAXIS 3D software to determine the maximum lift capability of single granular piles and group piles are presented in this paper. In loose sands, the foundation system is thought to be made up of a distinct number of consistently spaced GAPs. The analysis compares the effectiveness of varying configurations of GAP systems and investigates the effect of several factors such as the number of piles, n, and aspect ratio (L/D), as well as the properties of the materials for granular piles.

Landslides are one of the most challenging natural disasters occurring worldwide. In this regard, complete protection from a sliding soil mass may not be possible. However, various techniques are being used to hold back the failing soil long enough to evacuate. Flexible retaining walls are one among them. This study aims to numerically analyze and evaluate the use of sheet pile walls as a potential landslide barrier. An unconventional slope stabilization technique using parallelly oriented sheet pile walls, commonly known as Hardy Ribs, is adopted for this study. The effect of sheet piles on the slope displacement is studied in detail. The study is conducted using the Finite Element Method (FEM) with the employment of soil profile from a real landslide site. The soil was considered elastoplastic, obeying Mohr–Coulomb’s yield criteria, while the sheet pile was assumed linear elastic material by substituting properties of steel. The analysis was conducted with and without sheet pile and the results were compared. The study outcomes suggested that the sheet piles can effectively reduce soil’s lateral flow and further improve slope stability.

This study intends to investigate the settlement response of different configurations of group of piles subjected to compressive load. Using Plaxis 3D, large diameter cylindrical concrete piles were modelled as statically loaded single and in groups and numerical analysis were carried out. Load-settlement curves obtained from numerical analysis are utilized to estimate the efficiency coefficient of pile groups. Settlement response of the single pile from numerical analysis is validated with field test results obtained from published literature. Sensitivity analysis was carried out with different mesh sizes for optimization of results. The study indicates the decrease in efficiency coefficient with the increase in number of piles in group due to overlapping of stresses. Analysis of concentrically loaded single row pile groups shows that individual contribution of piles to the total group resistance decreases with increasing distance from the center of the group. Pertinence of the efficiency coefficient obtained from numerical analysis is assessed by comparing the results with those calculated from the well-known formulas available in public sources. Furthermore, results from analysis of selective pile group with Hardening Soil Model show marginally higher capacity as compared to Mohr–Coulomb model particularly for higher settlements.

The California bearing ratio (CBR) is an important input parameter in the design of flexible pavements. CBR is often determined in the laboratory involving a laborious and time-consuming testing procedure. In recent years, artificial intelligence (AI) and machine learning (ML) techniques have gained popularity in geotechnical engineering and can circumvent the laborious process of conducting laboratory testing to determine soil properties. This study presents the application of two AI models, viz., random forest regressor (RFR) and artificial neural network (ANN), to determine CBR based on soil basic and mechanical properties such as gradation, maximum dry density (MDD), optimum moisture content (OMC), liquid limit (LL), and plastic limit (PL). A large dataset of 652 data points was gathered from an extensive literature review consisting of all the basic and mechanical properties of soil along with the CBR value. The findings from the study reveal that the RFR model gave a high prediction performance with the coefficient of determination (R2) and mean squared error (MSE) equal to 0.92 and 16.2 respectively, whereas the ANN model resulted in the coefficient of correlation (R) and MSE equal to 0.95 and 28, respectively. Furthermore, sensitivity analysis was carried out to evaluate the most influencing soil parameters affecting the CBR. The results show that MDD has the greatest influence, followed by the percentage of fines, whereas PL has the least importance.

The maximum dry density and optimum moisture content are the compaction parameters of soil, determined by modified and standard proctor tests. The modified and standard proctor tests are heavy and light compaction tests. In this research, the factor affecting the compaction parameters and the estimation of heavy compaction parameters from light compaction parameters has been studied. The input parameters G, S, FC, $${D}_{60}$$ D 60 , $${D}_{50}$$ D 50 , $${D}_{30}$$ D 30 , $${D}_{10}$$ D 10 , $${C}_{u}$$ C u and $${C}_{c}$$ C c , are used to develop the regression models. Furthermore, Pearson's product-moment correlation coefficient depicts multicollinearity between gravel content and D10 for maximum dry density in both compaction conditions. Also, the coefficient of curvature has no relationship with compaction parameters. The results show that the index parameters ( $${D}_{60}$$ D 60 , $${D}_{50}$$ D 50 , $${D}_{30}$$ D 30 , $${D}_{10}$$ D 10 , $${C}_{u}$$ C u and $${C}_{c}$$ C c ) estimate the maximum dry density of soil better than other parameters (G, S, FC). However, the estimation of optimum moisture content is less accurate than maximum dry density for heavy and light compaction tests. The regression analysis between heavy and light compaction parameters shows that the regression models estimate the heavy compaction parameters with a correlation coefficient of more than 0.95 using light compaction parameters. Finally, this study concludes that the light compaction parameters of granular soil can estimate the heavy compaction parameters with acceptable results.

Settlement is the predominant criterion that governs the design of footing on frictional and cohesive frictional soil. Hence bearing pressure plays a key role in design of footing. To evaluate the bearing pressure, Teng, Meyerhof and other researchers proposed empirical formula and charts in terms of N values obtained from Standard Penetration Test (SPT). In the present study, soil investigation data obtained from four sites have been used to estimate the bearing pressure through empirical formula and finite element analysis. Finite element model is validated through the case studies available in the literature. Bearing pressure values for strip footing of width varying from 1.5 to 5.5 m were estimated. Further, an attempt has been made to check the reliability of empirical formula by comparing it with values obtained through numerical analysis. It is observed that if the SPT-N values are directly taken from the field tests, the results from Meyerhof expression were found to be in good agreement with the numerical model. Whereas, if only shear strength parameters are obtained from site, SPT-N value calculated indirectly using friction angle excludes the effect of cohesion. Hence, Meyerhof expression resulted in comparatively lower bearing pressure values.

Over the years, granular soil has been the predominant backfill material for reinforced wall construction due to its high strength, good drainage characteristics, and constant engineering properties. However, due to lack of availability, transportation issues, and economic issues with this type of soil, the use of poorly graded marginal soil as backfill has increased. Marginals backfill are soils having fines and plasticity index greater than 15% and 6, respectively. The objective of this paper is to numerically compare the performance of reinforced earth wall with clean granular fill and marginal fill. For this purpose, 2D FEM was simulated in ABAQUS software. The numerical model's accuracy was first validated by comparing numerical results with experimental wall. The results of wall lateral deformation, reinforcement load, and toe reaction in the wall are validated. Further parametric study is carried out to study the effect of surcharge, reinforcement length, and spacing, wall height on wall lateral displacement. Based on the results of these simulations, several considerations for the design of reinforced earth wall are identified.

In recent years, Kerala is facing heavy rainfall and due to that landslides and floods are occurring frequently. In 2021 heavy landslides occurred at Koottickal, Kottayam and life of the local people and embankments were in critical conditions. To suggest solutions for the problem, stability analyses were conducted. Field studies are time consuming and not feasible with the altered topography, hence numerical analysis plays a major role in the embankment studies. Finite element method by PLAXIS 3D is used in the numerical analysis of slope stability of embankment. The ground improvement techniques play a crucial role in the stability of embankments. The present study relates with the determination of stability of embankment according to the factor of safety and deformations with and without geogrid for toe angles 30°,45° and 60°.The factor of safety is increased by twice the initial value when the geogrid is placed into the embankments. Hence it is concluded that geogrid can be effectively used to prevent the slope failure due to frequently occurring landslides.

The interaction of soil and structure is important in the behaviour of structures under dynamic or static loading conditions. It has an impact on the behaviour of the soil and also how the pile behaves when the load is applied. The analysis is critical for predicting more precise behaviour of the structure and improving structural safety under extreme loading conditions. When subjected to lateral loads, a pile behaves like a transversely loaded beam. In response to applied load, the pile shifts horizontally, resulting in pile bending, rotation, or translation. Resistance to lateral loads is typically provided by the shear which is on the base of the cap, soil passive resistance on the face of the cap, and the passive resistance provided by the soil against the shaft of pile. If the lateral load towards the pile increases beyond the limit due to earthquake, wind action, naturals calamities, etc., casings can be provided to improve the lateral capacity. This paper presents the numerical study on lateral capacity of piles with different casing material with different thickness in cohesive soil. Steel, BFRC and Polypropylene fibre were used as casing materials. Pile with steel casing of 18 mm thickness shows minimum lateral deflection. Steel casings effectively improve the ultimate capacity of piles when lateral load is applied. Analysis is performed through the usage of PLAXIS 3-D software. The evaluation has become less difficult with the advent of excellent computers and software tools such as finite element analysis software.

Many geotechnical engineering constructions, including tunnels, sheet pile walls, bulkheads, earth retaining walls, and rail-road/highway abutments, rely on vertical plate anchors as their foundation. The vertical plate anchor resists the horizontal pullout force acting on these structures and imparts stability to these structures by restricting lateral movement. The influence of the aspect ratio (L/h ratio) of the vertical plate anchor embedded in the sand has been studied with the aid of the finite element method. The outcome shows that the non-dimensional breakout factor decreases with an increase in the aspect ratio up to 5 and thereafter marginal effect was noticed. Furthermore, the anchor capacity of a square plate anchor has also been studied, and found that the breakout factor decreases up to the size of 0.6 m × 0.6 m, and thereafter marginal reduction was observed and can be neglected.

A typical railway track structure is composed of different layers of constituent materials. The resulting contact interface between these layers results in displacement discontinuities and largely influences the strength-deformation behavior of the system. In order to assess and quantify the interactions that take place at these interfaces, the present study conducts Discrete Element Analysis (DEM) of large-scale direct shear interface tests using Altair EDEM software. These simulations use the extensive laboratory investigations earlier performed by [1] for validation. The shear stress parameter of the ballast-sub-ballast, ballast-concrete sleeper, ballast-steel sleeper, and ballast-geogrid are taken into consideration for this study. The contacts generated at the interfaces of different elements are also realized here. Since the contact interface behavior is largely influenced by the shape of the ballast, the number of contacts, and the inherent discontinuities, therefore the calibration of the modelled ballast and sub-ballast particles is also done in terms of static angle of repose value and bulk density before the actual test simulation. The plots of shear stress vs horizontal displacement values are obtained by extracting and relating them using the time parameter. The EDEM simulation results for the test cases are found in agreement with the laboratory test results with the variation lying within the range of ± 10%. The variation witnessed here may be because of the assumptions that are made during the simulation in order to reduce the computational time requirement.

Piled raft foundation is a combination of a shallow foundation (raft) and a deep foundation (pile group). In this type of foundation, the role of the raft is to provide the required bearing capacity, and the piles are used mainly as settlement reducers but can also contribute to the bearing capacity. In this paper, a numerical model was developed using the software PLAXIS 3D to analyze piled-raft foundations on layered soil. Layered soil, i.e., clay layer underlain by silty sand and then dense sand at lower layer with water table at a constant depth was assumed for the study. Here a drained condition was assumed and total vertical displacement was calculated using plastic calculations. The piles and raft were modeled using a plate element. A non-uniform vertical loading in the form of concentrated column loads has been imposed on the piled raft. The effect of some important design parameters on the performance of piled-raft foundations such as pile length, pile diameter, pile spacing, and raft thickness with varied numbers of piles on layered soil is studied. The effect of these parameters was studied in terms of their influence on the deformation of the piled raft foundation.

The anchors are used as a tension members which attached to the foundation of the structure, mainly to counter any vertical lift reaction or overturning moment or combination of both. Structures such as transmission towers, tension cable for suspension bridges, guyed lattice tower, marine structures like floating platforms and tension leg platform, and, buried pipelines carrying fluids are subjected to uplift forces like wind force and buoy-1ant force, which are inevitable and are much greater than the dead weight of the structure itself. This study uses Plaxis-3D to demonstrate the uplift behaviour of a horizontal square anchor plate in cohesionless soil. The study describes the load–displacement behaviour, representing the anchor plate's pullout capacity in terms of non-dimensional breakout factor, the impact of soil density, and the embedment depth of the pullout capacity.

Shrink-swell characteristics of expansive soils cause differential settlement beneath foundations, and the volume shift in the soil can cause serious structural damage, the elastic properties of the soil are one of the elements that are affected at the same time. These properties are also required for studying such soils using FEM modeling or software techniques. In the present investigation, an attempt has been made to establish a correlation between the elastic properties of expansive soil and the variation in its water content, which may be used directly for analytical studies. The stress–strain curve obtained from the triaxial test is used to compute the initial tangent modulus and secant modulus, while Poisson's ratio of soil is derived using unconfined compression tests at various strain values. The findings were compared to those of earlier studies. The R2 (strength of association) value was well above 0.92 for the obtained correlation for water content and Poisson's ratio. The values of tangent and secant modulus were observed to increase until the optimum moisture content was exceeded by 2–4 percent, after which they decreased.

Geocells are three-dimensional geosynthetics that consist of interconnected cells filled with soil. Reinforcing the soil with geocells improves the soil properties through friction, interlocking, and confinement. Many experimental studies were conducted to quantify the beneficial effects of geocell reinforcement in enhancing the stiffness and strength properties of the soil. However, not many numerical studies are available to understand the behaviour of geocell reinforced sand in triaxial compression. Due to the complexities involved in modelling the actual honeycomb shape of the geocell, most of the previous numerical studies were either conducted using Equivalent Composite Approach (ECA) or by approximating the actual shape of the geocells to simpler shapes like square, diamond or circular shape. FLAC3D was used to carry out numerical analyses in the current study. Triaxial compression tests on a cylindrical sample of unreinforced sand and sand reinforced with honeycomb-shaped geocells are simulated by implementing the actual shape of geocells. The parametric analysis was carried out on the validated numerical model to understand the effects of confining pressure, geocell diameter, modulus of the geocell material on stress–strain response of the geocell-reinforced sand.

The conventional design method (FHWA in Report FHWA0-IF-03–017, U. S. Department of Transportation, Federal Highway Administration, Washington, DC, 2003, [12]) and numerical modeling (PLAXIS 2D) have been adopted for the design of soil nail stabilized slope, and a comparison between the two methods is made by varying the design parameters. A 10 m vertical wall in lateritic soil with nails installed horizontally is considered, and a parametric study is performed on it. Variation in material properties such as cohesion, unit weight, and angle of shearing resistance was made and the output in terms of maximum lateral displacement and the Global Factor of Safety was obtained. It is noted that the conventional method assumes a constant value of output parameters (Maximum lateral displacement and Global Factor of Safety) whereas the results obtained from PLAXIS 2D show significant variation in the output parameters. The effect of varying geometric parameters such as back slope angle, the vertical spacing of nails, and facing thickness is also observed by PLAXIS 2D and presented.

Apart from the vertical load of the superstructure, the pile may be subjected to lateral loads caused by earthquakes, wind and water currents, vehicle loads, etc. Negligence of this lateral load may be dangerous if the structure is going to experience lateral thrust in any way. In previous studies, a single pile has been examined under lateral load for different soil characteristics, where deflection and maximum bending moment were determined. In the present study, dual pile (two) is taken with spacing of 2.5D and considered as a single unit. Lateral load is applied at the top of the dual pile, which is connected with a pile cap (connection plate). Experimental data of deflection is collected with the help of strain gauges installed over the periphery of each pile. In PLAXIS 3D software, a FEM model of the same setup with soil pile condition is created and analyzed. Results from both analyses are in good agreement and show that as the slope increases, lateral load capacity of the assembly decreases.

Marine Environment is one of the most challenging conditions to which Reinforced concrete (RC) elements get exposed. Chemical attack by salts of Chloride and Sulphate poses corrosion threat to reinforcements thus decreasing the durability of RC elements. This incurs extremely high rehabilitation costs around the globe annually. Chloride ingress through diffusion is the major cause of rebar corrosion. Critical parameters influencing the chloride diffusion revolve around uncertainties. This brings grave importance for the reliability based approach for the prediction of service life of such structures in terms of probability of failure. This study focuses on the prediction of service life of an RC element taking epistemic uncertainties involved in the marine environment into consideration. COMSOL Multiphysics model has been used to simulate the chloride diffusion into the considered RC element domain with suitable boundary conditions. Key parameters like Surface Chloride Concentration, Diffusion Coefficient, Concrete Cover Depth, and Concrete Composition are considered for the simulations. Regression analysis is carried out and is coupled with the First Order Reliability Method to model the uncertainties of the critical parameters involved. This study will also play a vital role in quantifying the impact of various parameters, optimizing the design of marine structures, and to develop cost-effective management strategies.

India is primarily dependent on thermal power plants for its energy needs. Large quantities of coal ashes emanate as a by-product of this process. Coal ashes produced in form of bottom ash and fly ash are often mixed with large quantities of water for wet disposal and sluiced to on-site ash ponds. Recently, considerable emphasis has been laid on suitable utilization of coal ashes in various infrastructure development projects. However, prior to any application their behavior, particularly, the shear strength characteristics under varied loading and drainage conditions needs to be carefully examined. In this study, a numerical model has been developed to analyze the post-peak strain softening behavior of coal ashes. A co-ordinate system transformation approach is employed based on the classical Duncan-Chang hyperbolic curve to model the softening behavior of undrained coal ashes. The validation of the model has been accomplished using triaxial data of six pond ash and four fly ash specimens randomly selected from various Indian power plants. Furthermore, a multi-variable regression analysis has also been carried out to develop empirical relationships between the model parameters and stress and strain values corresponding to peak and residual state, and confining pressure of the sample.

Geosynthetic reinforced soil (GRS) bridge abutments are becoming popular in recent days for various transportation infrastructures. Although several static analysis of bridge abutments have been carried out till date, very limited studies have been carried out regarding their dynamic performance. This paper carries out a numerical investigation of a bridge abutment subjected to seismic loading. Simulations were carried out using the finite element software, ABAQUS. After proper validation of the numerical model, fly ash was used as the backfill material to study the variation in the performance of the abutment in comparison to conventional backfill material. The results showed that the performance of the reinforced soil abutment using fly ash as the backfill material is satisfactory.

The influx of petroleum hydrocarbon into the aquifers due to piping leaks, an accidental spill of petroleum products, and leakage from underground fuel tanks at diesel and petrol pumps are some of the leading causes of aquifer pollution. This study presents a numerical model for subsurface investigation of benzene biodegradation in aquifers. Among the four BTEX (benzene, toluene, xylene, ethylbenzene) compounds, benzene is the most difficult to undergo degradation. This is because benzene has the highest C–H bond dissociation energy (473 kJ mol −1) among all the hydrocarbons. A fully implicit finite-difference approach is adopted here to analyse and solve the proposed numerical model, which is capable of obtaining the spatial variation in benzene concentrations. It is observed from the conducted research that biodegradation effectively limits the transport of benzene in aquifers. The investigation, in addition, can help in deducing the optimum rate at which electron acceptors are injected into the aquifer and the time required to reduce the concentration of benzene to desirable limits. The model also generates the scope of being used as a predicting tool for monitoring the efficacy of different biodegradation enhancement strategies in aquifers.

With the number of high-rise structures increasing day by day in metropolitan cities of most developing countries like India, the optimal choice of foundation is getting more attention. If the rock is available at reasonable depths and where the option of the open foundation is ruled out, the choice of engineers and consultants is to install piles in the rock so that the full structural capacity is utilized by mobilizing shaft and end bearing resistance. Rock socketed piles are bored cast in situ piles that are drilled and socketed into rock strata of adequate strength for a specific length (socket length) to achieve the design capacity. Several methods are available for evaluating the load-carrying capacity of these piles. As rock is a complex material, in addition to strength, several other rock mass properties like the influence of discontinuities also need due consideration in the design stages. In the present study, the influence of joints on pile performance is investigated using the finite element software, Plaxis 3D. Three-dimensional modelling is performed by simulating discrete joints as well as a jointed rock as a continuum. The performance of the rock socketed piles is discussed, and the results are systematically presented in this paper.

The civil engineering infrastructure such as roads and railways require embankments to maintain the designed gradient all along its alignment and also for flood protection. These embankments pass over different types of natural ground and when they pass over soft clay beds, several challenges are to be addressed in terms of lower bearing capacity, excessive settlements, and lateral deformations. When the unconfined compressive strength of clay bed is less than or equal to 5 kPa, traditional techniques such as stone columns, pre-loading with strip drains, and other modification techniques are considered to be time-consuming and uneconomical for a project. In such cases, piles are being adopted to support the embankment to keep pace with the project duration. However, the soft soil between the piles remains weak and the load transfer is to be facilitated by using a basal reinforcement at the top of piles. The basal reinforcement enables the system to develop the necessary arching action so that the load transfer takes place to the piles. In order to understand the load transfer mechanisms, several investigators have been working using numerical techniques. The present work is an attempt to study the influence of pile spacing, basal reinforcement stiffness, and its tensile strength in mobilizing the optimum soil-arching in order to facilitate the load spreading from the embankment to the piled clay bed using Plaxis-3D. The input parameters were kept as the cohesion of soft clay bed and pile material properties such as the modulus of elasticity (E) and Poisson’s ratio (µ). The pile spacing, reinforcement stiffness, and tensile strength were kept as variables.