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This volume comprises select papers presented during the Indian Geotechnical Conference 2018. This volume discusses concepts of soil dynamics and studies related to earthquake geotechnical engineering, slope stability, and landslides. The papers presented in this volume analyze failures connected to geotechnical and geological origins to improve professional practice, codes of analysis and design. This volume will prove useful to researchers and practitioners alike.

### Seismic Response of Shallow Strip Footing with Log-Spiral Failure Mechanism Using Limit Analysis

Computation of seismic bearing capacity that reduced to a single coefficient $$N_{\gamma }^{^{\prime}}$$ N γ ′ along with the mathematical models of shallow strip footing resting on $$c - \phi$$ c - ϕ soil is done here. Upper-bound limit analysis method in pseudo-static approach with log-spiral failure mechanisms having the base angle of left triangular rigid block at left footing edge is assumed. Effects of both the horizontal and vertical seismic acceleration coefficients have been found to always reduce the bearing capacity ratio $${{N_{{\gamma {\kern 1pt} E}}^{^{\prime}} } \mathord{\left/ {\vphantom {{N_{{\gamma {\kern 1pt} E}}^{^{\prime}} } {N_{{\gamma {\kern 1pt} S}}^{^{\prime}} \;}}} \right. } {N_{{\gamma {\kern 1pt} S}}^{^{\prime}} \;}}$$ N γ E ′ / N γ S ′ significantly. From the results obtained by the present method of analyses, parametric studies have been done along with the comparative study with available solutions under seismic conditions to show the efficiency of the proposed modification. From the comparative study, it is seen that the present log-spiral failure mechanism result is found to be lesser than other researchers in the seismic case.

Litan Debnath, Sima Ghosh

### A Comparative Study of Soil Slope Stability Under Seismic Loading Condition

The stability of the earth slope during seismic loading conditions is an important topic in the geotechnical engineering field. Several researchers reported stability analysis of slope under static and seismic loading conditions. This paper represents a comparative study of homogeneous c − ϕ soil slope stability using different dynamic approaches considering planer, circular and log-spiral rupture surfaces. Also, this paper provides a comparative study between the values of factor of safety obtained by the analytical approach and numerical solution. Results obtained from the different approaches are presented in tabular form to understand the comparison of different approaches considering different failure surfaces. It is observed that values of factor of safety obtained by the dynamic analysis considering log-spiral rupture surface are lower than the corresponding values obtained by the dynamic analyses assuming circular and planer failure surface.

Suman Hazari, Sima Ghosh, Richi Prasad Sharma

### Landslide Susceptibility Analysis and Mapping in Sastha Valley of Periyar River Basin

Earth attracts objects toward its surface through the gravitational force and keeps everything in place. In the case of a slope, this gravitational force may cause the materials to move along it causing what is known as landslides. This study mainly focuses on analyzing the landslide susceptibility in Sastha valley of Periyar river basin, Idukki district, Kerala. The study area shows some paleo-landslide movements indicated by sparse tea plantations and sharp meandering of the river flowing through the valley. This motivated to analyze the stability of the slopes through an extensive field investigation in the area. The stability analysis is carried out under both steady and transient states using SLOPE/W and SEEP/W software. A factor of safety map of the study area is also prepared from the GIS-TISSA model. Finally, a landslide susceptibility map of the area is generated by leveraging the results from both field study and GIS model.

P. Preji, Biju Longhinos

### Investigations and Mitigation Measures of Landslide Affected Areas in Hill Roads of East Africa—Case Study on Projects of Ethiopia

Avik Kumar Mandal, S. Sailesh, Pradyot Biswas

### Stability Assessment of Cut Slopes Along Shivpuri–Kaudiyala Road (NH-58), Uttarakhand Himalayas

In the present study, slope stability assessment of selected cut slopes on a road stretch of approximately 25 km length along the National Highway (NH-58) between Shivpuri and Kaudiyala in the Lesser Himalaya of Uttarakhand has been carried out. This NH-58 connects Rishikesh with Badrinath and Kedarnath, two important Hindu shrines in Uttarakhand and also the border areas of the country. Hence, it is obvious that this highway is important from the pilgrimage, tourism and defense point of view. The present study includes characterization of rock mass, computation of slope mass classification ratings and comparison of different rock mass classification systems (such as RMR, GSI, SMR and CSMR) for 25 numbers of rock slopes along the selected road stretch. Also, kinematic analyses have been performed for all these slopes to understand the mode of slope failure. Further, stability analyses of a few significant road cut slopes have been carried out using a finite element tool.

Neeraj, Koushik Pandit, Shantanu Sarkar

### Multivariate Adaptive Regression Spline Based Reliability Analysis of Stability of Durgawati Earthen Dam

In the present paper, multivariate adaptive regression splines (MARS) method is used to carry out reliability analysis of Durgawati earthen dam. The steady and transient state seepage is considered while calculating reliability index $$\left( \beta \right)$$ β . The earthen dam is an important water retaining structure and serves the catchment area of Durgawati River in Bihar, India. The factor of safety (FOS) of the earthen dam against slope failure under steady and transient state is performed using GeoStudio-07 software. In order to account for the variability of material parameters over the body of the dam, a data set of material parameters [i.e., cohesion ( $$c$$ c ), angle of internal friction $$\left( \varphi \right)$$ φ and soil unit weight ( $$\gamma$$ γ )] are prepared, and MARS is used to calculate reliability index $$\left( \beta \right)$$ β for different realizations over the dam geometry. The reliability index $$\left( \beta \right)$$ β thus estimated shows that the dam is stable and safe from slope failure point of view under different seepage loadings.

V. Kumar, P. Samui, A. Burman, N. Himanshu

### Landslides Hazard Mapping Using High-Resolution Satellite Data

Landslides are one of the severe natural hazards induced by heavy rainfall, deforestation, slope failure and urban expansion. It can lead to significant loss of life and property in hilly and gully regions. Field studies that identify and map landslides are expensive and time-consuming as it includes the cost of the survey, travelling, workforce, and instrument. Although progression in technology and availability of high-resolution remote sensing data has now made it possible to identify landslides (satellite images and aerial photographs), accessibility to high-resolution satellite data is still an expensive and tedious procedure. Several studies have conducted in a GIS environment to map landslide zones, but the resolution of the open-source data is commonly coarse (30 m), which adds to the uncertainty of the outcome. In this study, application of the appropriate rule set with object-based image analysis (OBIA) technique has been used to identify landslides zones, through a combination of spectral, textural and geometrical properties of imagery and topographic data. It overcomes the shortcomings induced by pixel-based classification. For the current study, High spatial resolution data such as Google Earth imagery and CartoDEM (30 m) has been used. This approach shows an excellent prospect for quick and near-to-actual assessment of landslides zones which are generally induced by extreme rainfall events in the hilly regions of India. The methodology used has the potential to facilitate more reliable disaster management strategies. This study shows the potential of open-source data and emerging technology in the field of landslide assessment.

Saloni Jain, Rakesh Khosa, A. K. Gosain

### Analysis of Rainfall-Induced Slope Failure Using Monte Carlo Simulations: A Case Study

Climatic changes influence the depth of slip surface drastically. Slope failures particularly, failures caused by rainfall, slip surface lie above the water table (i.e., in unsaturated zone). In this zone, suction develops, which increases the slope stability in dry conditions. During rainfall, water infiltrates into the soil pores due to which suction stress decreases significantly, and thereby, stability of slope decreases. Relation between soil suction and soil water content can be represented using soil water characteristic curve (SWCC). The measured SWCC, hydraulic conductivity ( $$k_{\text{s}}$$ k s ) of the soil are inherently variable. Conventional approaches may render unrealistic safety of the slope sometimes, as they do not account for variability. Therefore, it is highly appropriate to develop a reliability-based design (RBD) for stability analysis of rainfall-induced slopes. In this study, an efficient reliability analysis using Monte Carlo Simulations (MCS) is presented for rainfall-induced slope failures. A case study on shallow slope failures near Seattle, Washington, which are of sandy colluvium deposits on steep coastal hill slopes, is presented.

A. S. S. Raghuram, B. Munwar Basha

### Probabilistic Assessment of Paglajhora Landslide Using SLOPE/W

This paper reports stability analysis of the dynamic and recurrent Paglajhora landslide which is situated in the upper subpart of the Shiva Khola basin in the Kurseong region of Darjeeling Himalayas in the state of West Bengal, India. The height of the affected slope is approximately 1540 m, having two porches with fluctuating slope variations. The lower portion frequently fails and causes blockage of roads damaging the NH-55 highway and cutting the Kalimpong region from other parts of the country. The problem of slope failure is further adverse due to various geological features, steep slopes, rugged topography and intense monsoonal rainfall. The study area is divided into two major lithotectonic units, the Higher Himalayan Crystalline Sequence (HHCS) and the Lesser Himalayan Sequence (LHS), separated by major ductile shear zone known as the Main Central Thrust. Parametric analysis of the slope with variation in slope height and slope angle has been performed using SLOPE/W software. The resulting change in the factor of safety is calculated. The analysis would help in understanding the possible failure scenarios of the landslide area, and effective measures could be taken to reduce the risk.

Abhirup Dikshit, Neelima Satyam

### Stability Analysis of Hill Slopes in The Nilgiris, Tamil Nadu

Landslide is a sudden slide of rock, debris and earth down the slope. The Nilgiris have always been under the threat of landslides in monsoon season. The Nilgiris is a hilly district with an area of 2500 km2 located in the North-Western part of Tamil Nadu. Rainfall is the major triggering factor of landslides in The Nilgiris (Chandrasekaran in Assessment of damages induced by recent landslides in Ooty, Tamil Nadu, India. IIT Bombay, Mumbai, India, pp 687–688, 2010). In this study, two sites have been selected where landslides occurred during monsoon in November 2009. The soil samples were collected from the sites of landslides. A detailed investigation was carried out on the soil samples and index properties; chemical composition and shear strength parameters were drawn. The critical surface for the slope was drawn graphically using Fellenius (1936) method, and the same was incorporated into the software through co-ordinates. Many studies have been carried out using numerical analysis for The Nilgiris area but in this study, realistic site conditions and parameters have been incorporated. The analysis was carried using wetting depths of 2 m, 3 m, 4 m and 5 m at the edge of the slopes and shear strength parameters in GEO 5 and PLAXIS 2D software. The analysis result shows that the infiltration of water into the slope results in the reduction of shear strength parameter of the soil which leads to the failure of the slope. The results of Geo 5 analysis and PLAXIS 2D analysis were compared, and the conclusions were drawn from it.

Praveen Kumar, Krishnamurthy Premalatha

### Effect of Joint Orientation on the Seismic Stability of Rock Slope with Transmission Tower

In India, the Himalayan region lies in the earthquake zone V. The occurrence of landslide hazard is common in the area. Therefore, it renders a necessity to analyze the stability of the slope before designing a slope or a structure near or on it. This paper includes the qualitative stability analysis of a slope located at Karcham Wangtoo in Wangtu, Kinnaur, Himachal Pradesh, India. The qualitative sense lies in the fact that the least stable condition is found by calculating the total maximum deformation and the maximum stresses. The factor of safety was not exclusively calculated. The effect of joint set orientation was analyzed for the stability of slope having static and dynamic loading. The static load includes the gravity load of rockmass, footing and transmission tower. The dynamic load was applied using the acceleration-time history of the Koyna earthquake of magnitude 6.4 on the Richter scale. The analysis was done using the Abaqus/CAE 6.13 software package. It was found that in static condition, 30° of angle of orientation of joint with slope are the critical angle for the instability. For the seismic loading, the critical angle of orientation of joint is found to be 45°. As the distance of footing from the edge of the slope was increased, the stability of slope increases.

### Landslide Hazard and Risk Assessment Along NH-108 in Parts of Lesser Himalaya, Uttarkashi, Using Weighted Overlay Method

The present study is focused on the landslide incidences which are very frequent in the Himalayan region. Economy in most of the Himalayan region thrives more on tourism; hence, it is essential to take proper attention in these areas. The objectives of the present study include generation of a landslide inventory, damage assessment, hazard mapping and subsequently risk analysis. The aim is to identify the causative factors responsible for landslide occurrences in these areas and then prepare susceptibility and vulnerability zonation maps. The study area is a 46 km long stretch of NH-108 covering 184 km2 of the area in Uttarkashi district of Uttarakhand, India. The entire analysis is carried out using weighted overlay approach in ArcGIS software. The susceptibility map of the region is prepared and categorized from low to very high susceptible zones. Accordingly vulnerability and risk map of the region are also prepared. The entities considered in risk assessment include agricultural land, roads and places of human settlements. The validation of the analyses results is carried out through field investigations and satellite imageries.

Pankaj Kumar, Anupam Mital, P. K. Champati Ray, Shovan L. Chattoraj

### Seismic Response of Gravity Retaining Wall

The behavior of retaining wall during an earthquake is a topic of major concern nowadays due to its grave consequences. IS 1893 adopts the force-based pseudo-static method for the design of retaining walls under seismic condition, which incorporates the additional seismic force into the static Coulomb’s theory. The lateral earth pressures derived from the M–O method are only true in its range of assumptions. In this paper, a numerical study based on the displacement-based approach is conducted for analyzing the seismic response of gravity retaining wall using the finite difference software FLAC-2D. A nonlinear time-history analysis of gravity retaining wall is conducted with actual earthquake data including the recent earthquakes in India. The validation of the numerical model is done by comparing the results with the already published literature. The results are presented in graphs and can be adopted for further studies.

### Some Studies on the Pseudostatic Analyses of Water Retention Type Tailings Dams

Tailings dams have been widely constructed to store the milled and mined out residual waste or tailings from the mining industry. These residues could be hazardous and/or toxic in nature; therefore, it is pertinent to design these storage structures in such a way that they are stable on the wake of slope failures due to accidents arising from natural and anthropogenic activities. In this paper, an attempt has been made to study the seepage and stability behaviour of water retention type tailings dams of different heights under static and seismic conditions. To this effect, the effect of horizontal drain on the seepage and stability behaviour of tailings dams was investigated using Soil Vision software. Seepage analyses were carried out using SVFLUX, and pseudostatic slope stability analyses were performed using SVSLOPE software for various combinations of horizontal and vertical seismic accelerations. It was found that the use of horizontal drain ensured the depletion of phreatic surface and improved the stability of the dam in the downstream side under both static and seismic conditions. A comparison has been made for obtaining the most suitable configuration for the construction.

Pankaj Kumar, B. V. S. Viswanadham

### Behavior of Reinforced Retaining Wall Against Railway Embankment Using Midas Under Static and Seismic Loading

Retaining walls are commonly used in the design of roadways and railways. Basically retaining walls are meant to carry lateral loads. Although many works from the literature suggest vivid methods to analyze and design these retaining structures, still there is enough scope to explore the problems faced in the analysis of retaining structures. In the present study, a retaining wall is considered to be supporting railway embankment. Backfill consists separate layers like natural soil, sub-ballast, and ballast. Load of sleepers and rails is also accounted. Load of rails is simulated using two point loads. Soil is assumed to be linearly elastic and is of Mohr–Coulomb’s characteristics. Geogrid is considered as reinforcing material in retaining wall. Midas is used to do FEM modeling of the problem. The wall is analyzed under static and seismic loading conditions. A detailed sensitivity analysis is carried out to understand the displacements of wall.

### Analysis of Retaining Wall in Static and Seismic Condition with Inclusion of Geofoam Using Plaxis 2D

This paper presents the study carried out to analyze the static and seismic behavior of the retaining wall and backfill soil. The lateral earth pressure on retaining wall plays an important role to ensure safety of such structure. The dynamic lateral earth pressure on retaining wall during earthquake condition is always greater than static lateral earth pressure and can induce large destabilizing force. Plaxis 2D software accomplishes the analysis of retaining wall in static and seismic conditions. The retaining wall with backfill material was analyzed with inclusion of compressive material EPS geofoam, which was placed at the interface of retaining wall and backfill material as an absorber to decrease lateral earth pressures on retaining wall. Parametric study of retaining wall has been done by changing various densities of EPS geofoam and thickness. This study shows that inclusion of EPS geofoam reduces the pressure on retaining wall in static as well as seismic condition.

### Static and Seismic Analysis of Twin Metro Underground Tunnels

In any metropolitan city, underground structures are key elements of a mass rapid transit system. In situations where metro underground construction is to be undertaken in poor soil strata, it is not possible to excavate a single large diameter tunnel for accommodating the two-way traffic of trains. It becomes therefore essential to have two parallel tunnels aligned either horizontally or vertically. In this paper, an attempt has been made to predict the influence of construction of a second tunnel, aligned either horizontally or vertically, after the construction of the existing first tunnel. The analysis has been carried out for both static and seismic conditions by varying the pillar width between the tunnels. Elasto-plastic finite element analysis has been carried out through Plaxis 2D software for the 1999 Chamoli earthquake of lower Himalaya. The analysis brought forth the fact that vertical stresses at critical points and the forces in RC liners of both horizontally and vertically aligned twin tunnels increase during the earthquake for a pillar width equal to half the diameter of tunnels. These vertical stresses and forces in RC liners have been found to reduce with increase in pillar width in case of vertically aligned twin tunnels, whereas a reverse situation arises in case of horizontally aligned twin tunnels.

### Soil-Structure Interaction Analysis of a Raft Foundation Supporting RC Chimney

Foundations supporting superstructure need to be designed for the reactions due to wind/seismic loads in addition to dead load, imposed load of the superstructures. In case of tall structures like chimneys, the base moments will be high and hence need to be checked for both maximum and minimum bearing pressures and ensure that the safe bearing pressure is not exceeded and also the possible uplift if any is limited to the guidelines suggested by the codes. In the present study, a foundation raft supporting 60 m high RCC ventilation stack is analyzed for various load combinations. The effects of soil-structure interaction have been considered in the detailed finite element analysis carried out. Soil-structure interaction (SSI) effects in both static and dynamic case with and without embedment effects are considered. In the foundation design, uncertainties in SSI are also accounted. The results obtained for various aspects mentioned above have been discussed.

Shilpa Dixit, Srinivasa Phanikanth Vedula, Srinivas Kakaraparthi

### Evolution in Liquefaction Strength of Ganga River Sand Due to Intrusion of Non-plastic Silt

Previous studies claim that the presence of higher proportion of plastic clay or silt particles in sandy deposits enhances the liquefaction strength of soil. However, the behavior of sand mixed with non-plastic silt is still a part of the enduring discussion among geotechnical researchers. The present study is carried out to determine the liquefaction strength of Ganga sand containing different percentages of non-plastic silt ranging from 0%, 5%, 10%, 20%, 30%, and 100%. Undrained strain-controlled cyclic triaxial tests have been carried out at 0.5 Hz frequency, 0.65% axial strain level, and confining pressure of 150 kPa. Considering generation of excess pore water pressure (EPWP) value of 0.95 as the criteria for liquefaction, the result suggests that the rate of EPWP generation has decreased initially upto 10% silt content, and thereafter, at 30% silt content the rate has increased tremendously which eventually got reduced at soil sample having 100% silt.

### Probabilistic Approach of Liquefaction Assessment for Guwahati Based on Shear Wave Velocity Values

Guwahati is one of the fastest growing cities in the North East India. It is situated along the banks of river Brahmaputra and is classified into seismic zone V in the seismic zonation map of India. The high seismic hazard in North East India points to the fact that earthquake-induced liquefaction assessment for these regions is necessary. Due to the large number of uncertainties associated with the evaluation of soil liquefaction, probabilistic liquefaction assessment has gained significance. In this study, liquefaction potential is evaluated by following a sequence of steps which include the generation of an earthquake catalogue, identification of the seismic sources, developing probabilistic seismic hazard, and probabilistic assessment of liquefaction potential. The use of probabilistic methods in liquefaction potential evaluation will help in quantifying the uncertainties involved in seismic hazard and soil resistance in a better way. The spatial maps showing the variation of factor of safety against liquefaction for different return periods are developed based on the shear wave velocity values. These results will help in delineating regions with high liquefaction hazard in the city thereby facilitating risk mitigation activities.

K. S. Vipin, S. D. Anitha Kumari

### Generalized Solution for the Critical Soil Wedge Angle Under Seismic Passive Earth Pressure Condition

In this paper, a generalized solution for the critical soil wedge angle under seismic passive earth pressure condition on the retaining wall is presented with plane failure surface using pseudo-static method. The development of an explicit expression for the critical soil wedge angle is presented in this paper using analytical method. The effects of different parameters like height of wall, slope of backfill, inclination of the back of wall, adhesion between the wall back face and soil backfill, properties of the backfill, and seismic coefficients on the critical soil wedge angle on the chosen wall are studied. The results from this method are compared with standard theoretical methods and show encouraging agreement.

Priyam Chatterjee, Bikash Chandra Chattopadhyay, Joyanta Maity

### Dynamic Slope Stability Analysis of Ash Dykes

Ash, a by-product obtained from the ignition of coal, is predominantly produced from thermal power plants based on coal. Disposal of the ash in land can be minimized by using the ash in various geotechnical, structural, and transportation engineering works. When ash is to be used in these works, properties of the pond ash under dynamic conditions must be ascertained to find its liquefaction potential under cyclic loading. The cyclic loading procedures to determine dynamic properties of ash commonly used in laboratory are simple shear, cyclic triaxial, and resonant column. In the current study, a series of strain-controlled tests were performed at various relative densities and effective confining pressures in cyclic-traxial apparatus to find the liquefaction potential of pond ash in the dyke. Finite element analysis was carried out using the GeoStudio software to find the factor of safety against slope stability. The factor-of-safety values were found to be more than 1.5 under both static and dynamic loading conditions. The bearing capacity of soil at first stage of ash dyke loading and pond ash at higher stages was found to be adequate.

P. Hari Prasad, K. Vineeth Reddy, G. Kalyan Kumar

### Analysis of Pile Under Seismic Motion Using Pseudo-static Approach

In the present study, pseudo-static approach has been used to assess the behaviour of a single pile subjected to seismic loading by FDM. Imperial Valley earthquake accelerogram has been scaled to 0.10 g, 0.13 g and 0.16 g peak bed rock acceleration (PBRA). These motions have been used to carry out equivalent linear method of ground response analysis (GRA) to get the peak ground acceleration (PGA) and deformation profile of soil column. The effect of shear wave velocity of soil mass, pile diameter, input motion, vertical load at pile head on behaviour of both free head and fixed head piles has been studied using pseudo-static approach. The study shows that the increase in PBRA and vertical load will increase the pile deflection and bending moment, whereas the increase in shear wave velocity of soil mass will cause reduction in pile deformation but an increase in bending moment.

Tanumaya Mitra, Kalyan Kumar Chattopadhyay, Ambarish Ghosh

### Ground Response Analysis and Determination of Liquefaction Potential Index

Four borehole data from 4/1 Moore Avenue, Tollygunge, Kolkata, were collected to carry out ground response and liquefaction analysis. Two scaled input motions with peak bed rock acceleration (PBRA) 0.10 and 0.16 g have been generated from original Imperial Valley Earthquake accelerogram. The peak ground accelerations (PGA) obtained from ground response analysis using DEEPSOIL software have been used to determine the probable depth of liquefiable soil for Mw of 6.8. Ground response analysis shows amplification of PGA from 0.10 to 0.143 g and 0.16 to 0.208 g. Liquefaction analysis result shows that the bore holes analyzed are not susceptible to liquefaction as the liquefaction potential index (LPI) values come out to be 0.0 indicating very low risk for the region.

Tanumaya Mitra, Kalyan Kumar Chattopadhyay, Ambarish Ghosh

### Probabilistic Seismic Hazard Analysis of Vadodara Region

The Vadodara region falls in seismic zone-III as per IS 1893:2016 and surrounded by highly active seismic sources. Seismicity of the Vadodara region has been determined by the evaluation of peak ground acceleration (PGA) model considering probabilistic framework. Probabilistic analysis has been carried out considering the earthquake data for the time interval between 1668 and 2017. The seismic parameter ‘b’ has been estimated as 0.815 ± 0.001 by adopting suitable recurrence relation. Four ground motion prediction relationships have been adopted to estimate the hazard of the study region. The PGA model at rock level has been quantified by dividing the study region into the grid size of 1 km × 1 km, which varies from 0.054 to 0.071 g and 0.104 to 0.139 g for 10% and 2% probability of occurrence in 50 years, respectively. The results will be further useful for designing earthquake-resistant structures, risk mitigation and future city planning.

Payal Mehta, T. P. Thaker

### Response of Monopile Supported Offshore Wind Turbine in Liquefied Soil

Offshore wind turbines (OWT) are the potential source of renewable energy. Monopile is a common choice as foundation for OWT, since this type of foundation has proved to be economical at shallow water depth and is designed for 25–30 years. These structures are designed as soft–stiff approach, where the fundamental frequency of soil–monopile–tower system is placed between the rotor frequency (1P) and blade passing frequency (3P for 3 bladed turbines). Design guidelines suggest that the fundamental frequency of the OWT system shall be at least 10% away from the 1P and 3P frequencies. Previous studies mostly focus on the behaviour of these structures under long-term cyclic loads. Limited studies are available on the behaviour of OWT structures in liquefied soil when subjected to earthquake loading. Soil surrounding the monopile may liquefy during earthquake which affects the dynamic response of OWT structures. In this study, dynamic behaviour of OWT structure in a liquefied soil is examined using numerical model in open-source code, OpenSees with aid of OpenSeePL. In this study, monopile is embedded in saturated silty sand with 60 m depth soil profile is considered. Spectrum consistent strong motion accelerogram is generated for various earthquake moment magnitudes. The dynamic analysis is carried out in time domain, and response of the OWT system is examined for various diameter and length of monopile, and magnitude of earthquake. Finally, design implications are suggested.

Sangeet Kumar Patra, Sumanta Haldar

### Reliability Analysis of Single Pile in Lateral Spreading Ground: A Three-Dimensional Investigation

Estimation of design forces in pile foundation is prevalently deterministic for all the practical purposes and thereby ignores the intrinsic uncertainties associated with the geotechnical parameters. Three-dimensional numerical investigations have been carried out using open-source software OpenSees considering a single free head pile embedded in three-layer soil profile with liquefiable sandy layer sandwiched between two non-liquefiable clayey soil layers. In the present study, the influence of uncertainties in geotechnical parameters on the response of pile foundation in case of lateral spreading ground conditions has been considered and response surface models were generated using response surface method (RSM). Reliability analyses have been performed using the first-order reliability method (FORM) for pile head deflection and bending moment. Finally, the performance of the pile foundation in spreading ground condition has been presented in terms of reliability index values. The study indicated that the performance of pile in laterally spreading soil is highly sensitive to the thickness of liquefiable soil and overlying non-liquefiable crust.

J. S. Rajeswari, Rajib Sarkar

### Influence of Soil–Structure Interaction in Elevated Water Tank

This paper presents the effect of soil–structure interaction (SSI) on the response of elevated water tank in different types of soil medium. Two intze-type elevated water tanks of the same capacity and the same dynamic characteristics, one with frame staging and the other with shaft staging, based on three different soil types are chosen to check the influence of SSI due to three representative earthquakes. Modeling of elevated water tank–soil foundation system is done using ANSYS Workbench®. Soil mass is considered large enough to avoid reflection of Rayleigh waves. While the bottom of the soil mass is considered fixed, vertical rollers are provided in the vertical faces of the soil mass to account for semi-infinite nature of the soil. Time history analysis is performed on the multiple systems. It is found that the gravity load design of Krishna Raju (Krishna Raju, Advanced reinforced concrete design (IS: 456-2000) (English), CBS Publisher, 2015) is not valid for seismicity-prone region.

Sutanuka Nath, Atanu Kumar Dutta

### Seismic Ground Response Analysis for Soil Site in Johor, Malaysia

Seismic ground response analysis (GRA) has been carried out for a soil site located in Johor, Malaysia, in order to know the degradation of soil layers overlying a bed rock subjected to a ground motion. In this paper, an effort has been made to critically study the results obtained by 1-D equivalent linear analysis and nonlinear analysis using DEEPSOIL v6.1, SHAKE 2000 and D-MOD 2000 for different modulus reduction and damping curves with two different soil models. The results are observed to be nearly similar for a lesser depth soil model unlike larger depth soil model, for which the results are slightly different. The results from DEEPSOIL v6.1, SHAKE 2000, and D-MOD 2000 are found to be different for a larger depth soil model. Nonlinear analysis is preferred as it takes into account the actual nonlinear characteristics of soil.

Anurag Sahare, Deepankar Choudhury

### Design of Pile Foundation System for Wharf Structure in Liquefiable Soils

Liquefaction of soils during an earthquake motion results in complete loss of shear strength and stiffness leading to huge lateral ground movements and further failure of structures. Therefore, it is recommended to include liquefaction hazard assessment of soils in design procedure to avoid future damage of structures. There exists some concurrence between liquefaction assessment of free field sites and liquefaction of soils beneath foundations which is still a controversial issue. In the present study, a pile supported wharf has been considered from Vishakhapatnam port (Andhra Pradesh). Liquefaction hazard assessment has been carried out, and depending upon the factor of safety against liquefaction; the pile foundation system has been redesigned against liquefaction. The results from the present study indicate an optimized pile configuration compared to conventional design procedure. Factor of safeties achieved are high enough to avoid liquefaction-induced failures.

### Ground Response Analysis of a Nuclear Power Plant Site in Southern India: A Nonlinear Approach

One-dimensional nonlinear ground response analysis is performed for a nuclear power plant site situated in east coast of south India. Since the strong motion records available for the study area are scarce, a synthetic ground motion time history developed for the same site by (James et al., Nat Hazards 71:419–462, 2014) and its scaled-up scaled-down versions are used as the input motion at bedrock level. A few more synthetic ground motion histories are also developed and applied as input motion in order to analyse the deviation in ground response with variation in frequency content and duration of bedrock motion. Martin–Finn–Seed pore pressure model is used to compute development of excess pore pressure during loading. The peak horizontal acceleration (PHA) profile, amplification spectra and response spectra at surface level for 5% damping are plotted for each location.

U. Veena, Naveen James, T. G. Sitharam

### Assessment of Soil Liquefaction Resistance by Finite Element Approach

Soil liquefaction is the source of several major damages during earthquakes on the material and human level. Liquefaction of soil occurs under dynamic or cyclic loading, due to which the soil loses its strength. A soil deposit subjected to seismic loading can be viewed as a binary system: it will either liquefy or not liquefy. Generalized linear models are versatile tools for predicting the response of a binary system and hence potentially applicable to liquefaction prediction. In the present study, a numerical procedure based on finite element technique is presented for evaluating the characteristics of soil liquefaction and the foundation response under seismic loading. The relative density of soil is an important parameter in prediction of liquefaction. However, this property varies from place to place with the density and nature of soil. Therefore, a double layered soil profile is used to model the change in relative density of soil with depth. A constitutive elasto-plastic model with dynamic loading is considered to study the phenomenon of liquefaction. The approach is presented through the simulation of five major earthquake data. The different parameters of simplified method as proposed by Seed and Idriss have been measured for the given field conditions, with varying magnitudes of earthquake and horizontal ground acceleration. The factor of safety has been calculated and is being used to denote the occurrence of liquefaction for all the cases of soil strata considered. Parametric studies are carried out considering different ranges of relative density of sand and earthquake magnitudes, and the corresponding factors of safety are proposed for the same.

### Liquefaction Susceptibility Mapping of Kollam Coastal Stretch, Kerala, Considering Geotechnical Parameters

The assessment of liquefaction potential is one of the important scientific problems for the geotechnical investigators. Liquefaction of loose saturated cohesionless soil during earthquake has been a major cause of damage due to earthquake for the buildings, earth embankments and other civil engineering structures. The study area of the coastal stretch of Kollam in western Kerala, India, mainly consists of coastal alluvial deposits and marine sand. Samples were collected along the length and width of coastal stretch of Kollam and are tested to obtain water content, dry density, fines content and the gradation curves. Limiting curves-based gradation criteria proposed by Tsuchida (1970) and empirical relation for stress ratio (SR) values obtained by Chien et al. (2002) were used for the calculation of liquefaction potential at sample locations. Spatial analysis of this data is done using QGIS to delineate the region into most liquefiable, liquefiable, less likely to be liquefiable and not liquefiable zones. The susceptibility map developed based on SR criteria is found to be in agreement with the liquefaction potential map developed by overlay of the two criteria which infer the dominant influence of dry density of the deposits of Kollam coastal stretch. Further, a ground truth examination of the final susceptibility map revealed that the zones in which water table lies within 0–5 m from ground level are more vulnerable to liquefaction in the Kollam coastal stretch. The proposed liquefaction susceptibility map can be used as a firsthand info on liquefaction potential of region which can aid in site-specific studies for future development.

S. K. Sithara, S. Surya, Sayana Parveen, Liz Maria Damiyan, Vinayak Mohan, A. Muhammed Siddik, S. Adarsh

### Finite Element Analysis of Foundation on Layered and Homogeneous Soil Deposit Under Dynamic Loading

An earthquake force causes severe damages to civil engineering structures and their foundations. Geographical statistic shows that almost 54% area of India vulnerable to earthquake. Hence, it is very important to analyze dynamic response of the foundation. In the present study, an attempt has been made to study the behavior of foundation resting on layered and homogeneous soil deposit under dynamic loading condition. Two types of soil systems have been considered for the analysis; one is the layered soil system consisting of loose sand at the top, soft clay at the bottom and medium sand in between, and the other one is the homogenous soil system with soft clay. The effect of water table on soil foundation system of both layered and homogeneous soil systems has also been studied. The foundation considered for the analysis is shallow foundation (continuous footing). The dynamic loading considered for the analysis is of the recent Nepal earthquake (Mw-7.8). The modeling of the soil foundation system has been carried out using two-dimensional finite element software CyclicTP. The response of shallow foundation resting on layered and homogeneous soil deposit under dynamic loading condition is presented in the form of horizontal and vertical displacement; ground acceleration; excess pore pressure and excess pore pressure ratio; and shear stress versus shear strain at various locations. The results have been compared to understand the effect of layered and homogeneous soil on dynamic response of soil foundation.

Abhay Kumar Verma, Supriya Mohanty

### Site Classification of Strong Motion Stations of Uttarakhand, India, Based on Standard Spectral Ratio, and Horizontal-to-Vertical Spectral Ratio Methods

Program for excellence in strong motion studies) (PESMOS) is an important accelerogram database in India consisting of earthquake records from 300 recording stations (RSs) located across the country. A major limitation of PESMOS database is the lack of accurate information on the seismic site class of RSs, which is essential for the utilization of ground motion records in seismic hazard and ground response studies. In the absence of in-situ field study data, site class of RSs can be determined indirectly analyzing recorded ground motions using empirical and semiempirical methods. In the present study, site class for 4 RSs located in the eastern region of Uttarakhand is established in accordance with the predominant frequency values obtained using standard spectral ratio method (SR), generalized inversion technique (GINV) as well as horizontal-to-vertical spectral ratio method (HVSR).

N. H. Harinarayan, Abhishek Kumar

### Seismic Site Classification and Site Period Determination of NIT Silchar Using MASW

Silchar is situated in the north-eastern region of India which comes under seismic zone-V. This region of India is bounded by several faults like Dauki fault, Indo-Myanmar subduction zone and Sitakunda–Teknaf fault. Most of the buildings in Silchar including some buildings at NIT Silchar developed cracks during Imphal Earthquake of magnitude Mw = 6.7 on 4th January 2016. Hence, seismic site classification becomes very crucial for the entire north-east region. In the present study, NIT Silchar campus has been taken as a study area. Multichannel analysis of surface waves (MASW) technique, one of the recent developments in geophysical methods, was carried out at nine sites within the campus and the average shear wave velocity (Vs30) upto 30 m depth was obtained. Three confirmatory boreholes were dug for validation. The study showed that NIT Silchar falls under seismic site class D category according to National Earthquake Hazards Reduction Program (NEHRP) Code. The fundamental site period obtained from MASW reveals that, the soil conditions at NIT Silchar pose a potential threat to four- and five-storey buildings due to resonance during earthquakes.

Arindam Saha, Kallol Saha, Ashim Kanti Dey

### Comparative Study of 1D, 2D and 3D Ground Response Analysis of Pond Ash from Odisha Under Different Earthquake Motions

It was attempted in the current study to study the one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) ground response of pond ash collected from Odisha under different earthquake motions. 1D ground response of pond ash deposit was studied by employing equivalent linear and nonlinear analysis methods, viz. SHAKE2000 and Cyclic1D software, respectively. 2D and 3D seismic response analysis of pond ash was investigated by employing Plaxis2D and Plaxis3D, respectively. Response of the pond ash deposit when subjected to Northeast India earthquake (Mw-7.5) and Nepal earthquake (Mw-7.8) was studied here in this study. Results of the response analyses were presented in terms of acceleration, displacement, excess pore pressure and excess pore pressure ratio. It was attempted to perform a comparative study on variation of stated parameters over 1D, 2D and 3D ground response analysis performed in this study. Variation in peak ground acceleration of 1D over 2D and 3D seismic response analysis of pond ash under Northeast India earthquake was 1.21 times and 1.46 times, respectively; whereas under Nepal earthquake was 0.72 times and 0.92 times, respectively. Maximum peak ground displacement was noticed in case of 3D ground response analysis. Pond ash was not susceptible to liquefaction when got excited under both the earthquakes.

M. V. Ravi Kishore Reddy, Supriya Mohanty, Rehana Shaik

### Effect of Soil Grain Size on Liquefaction Strength of Sandy Soil

This study is focused on estimating the difference in behavior between three soils: natural, medium and fine sand. Strain-controlled cyclic triaxial tests were conducted on all three types of soils. Samples were prepared using air pluviation method, and soil relative density was controlled between 10 and 20% (loose soil). The medium sand was considered as base case with a frequency of 0.5 Hz, axial strain of 0.5 mm and effective confining pressure of 100 kPa. The axial strains (0.1–1 mm) was also varied to find out the effect of various strain levels on excess pore water pressure generation and degradation of soil strength during cyclic loading. From the results, it can be concluded that the excess pore water pressure generation was much faster in fine sand than that in medium sand. This ultimately causes degradation of liquefaction strength at much faster rate in fine sand compared to that in medium sand.

### Seismic Vulnerability Assessment of Pile Foundation in Liquefied Soil Incorporating Ground Motion Uncertainty

Seismic design of pile foundation has given a special attention by the earthquake professionals in last decade after experiencing many failures due to moderate to severe earthquake. Dynamic soil–structure interaction (DSSI) was reported as an important phenomenon in seismic design, and however, used to explain failure mechanism of piles during past earthquakes. It is observed from past case studies that pile failures are mainly reported in liquefied ground. Hence, vulnerability assessment of pile foundation in liquefiable deposit considering different failure mechanism is important for ensuring seismic safety of pile foundation. Present study is an attempt in this direction. Vulnerability of pile foundation will be assessed by calculating probability of exceedance of serviceability limit state criteria incorporating ground motion uncertainty. The uncertainty factors considered in generating ground motions are consists of source and attenuation of earthquake, local geology and site condition and variability associated with seismic force determination. Monte Carlo simulation (MCS) technique is used for probabilistic analysis. Seismic response is obtained for soil-pile foundation-structure system using 3D finite element software, namely OPENSeeSPL (Edu version 2.7.2). The case study of Showa Bridge during 1964 Niigata earthquake is considered in present study to perform the reliability analysis. Finally, the vulnerability of pile foundation is presented in the form of fragility curves. The limited study indicates that probability of failure reaches 100% considering serviceability condition when PGA of ground motion exceeds 1.0 g. This study will help to revamp the present design guidelines of pile foundation.

Partha Bhowmik, Rajib Saha

### 1 g Shake Table Study on Seismic Behaviour of Model Structure Supported by Pile Foundation in Liquefiable Soil

Failure of pile foundation in liquefiable soil was evidenced in many past earthquakes. In fact, the complex interaction between soil, pile foundation and structure in liquefiable soil during seismic loading commonly known as seismic soil-pile foundation-structure interaction (SSPSI) is an important phenomenon which influences the dynamic behaviour of the whole structural system. Previously, SSPSI is generally disregarded in seismic design due to complexity in modelling and beneficial attributes of soil structure interaction as highlighted in previous codes. However, research indicates that argument still prevails with failure mechanism of pile foundation in liquefiable ground. In this context, present study is an attempt to assess the influence of dynamic interaction between soils, pile foundation and structure system during pre- and post-liquefaction stages by carrying out 1 g shake table experiments. Four physical models, consisting of 1 × 2 and 2 × 2, 3 × 3 and 4 × 4 pile groups supporting SDOF structure having fundamental period of 0.2 s and 2.0 s, respectively, are tested. Dynamic strain at pile head and pore water pressure is measured during pre- and post-liquefaction stages. Results indicate that pile foundation attracts higher forces and displacement during onset of liquefaction even though damping increases in the system. Finally, this study gives insight into the problem which may help in modifying existing seismic design guidelines for pile foundation supported structure in liquefiable soil.

Archana Kunwar, Swagata DebRoy, Rajib Saha

### Studying and Comparing the Declustered EQ Catalogue Obtained from Different Methods for Guwahati Region NE India

Declustering is a major step in any seismic hazard assessment approach and the choice of it controls the seismic activity estimation of the region. In this method, three different declustering methods are used for declustering the EQ catalogue collected around 500 km of Guwahati city. Completeness tests are performed on each of the declustered catalogue to find out the events which are complete with respect to magnitude and time. Further, complete catalogues are used to find out the Gutenberg–Richter (G–R) parameters from three different catalogues for the same seismotectonic province. Comparison is done on the basis of numbers of EQs in the declustered catalogues and on the basis of ‘a’ and ‘b’ parameters of the Gutenberg–Richter (G–R) recurrence law. Both ‘a’ and ‘b’ parameters are found varying based on the catalogues developed using each of the three methods clearly indicating that the choice of method may assign low to higher seismicity to the same region and same EQ catalogue.

Niranjan Borah, Abhishek Kumar

### 3D Finite Element Analysis of Seismic Behavior of Soil-Piled Raft-Structural System

Piled raft foundations are mainly used in case of high rise buildings and important structures to control total and differential settlement and to enhance the bearing capacity. Behavior of structural system placed on piled raft foundation during earthquake is considered fairly complex due to dynamic interaction between soil, pile, raft, and structure. Traditionally, piled raft foundation and structure under seismic load are designed without considering flexible base condition, although soil flexibility may have significant effect on the response of soil–pile raft–structure system. In this connection, present study is an attempt to numerically investigate the seismic behavior of piled raft supported structural system embedded in homogenous soft clay using 3D finite element model in ABAQUS/CAE v6.8. Two representative fixed base periods of structure, such as, 0.3 and 2.0 s which represents low, and high rise structure respectively are considered to be supported on piled raft foundation. Nonlinearity of soil is modeled by Mohr–Coulomb soil plasticity model. Elastic responses are obtained for both soil-piled raft–structure system and fixed base system with recorded motion of 1995 Kobe earthquake. Present study calculated the maximum shear forces at the column (VB,col) and pile head (VB,pile) and compared with those for the same structure in the fixed base condition (VB,fixed). Results indicated that shear force considerably increases in pile head for both low and high rise structures as compared to fixed base shear. Further, increase at pile head observed to be significant when pile length asymmetry introduced considering optimum pile group design philosophy. However, increase in shear at column is marginal in long period structure.

Chaidul Haque Chaudhuri, Rajib Saha

### Seismic Requalification of Pile-Supported Structure: Pseudo-Static Approach

Pseudo-static approaches often become handy due to their simplicity compared to the complex coupled continuum dynamic analysis and yield satisfactory results. A pseudo-static approach is employed herein to evaluate the response of a pile-supported structure located in a highly active seismic zone in northeast India. Pseudo-static approach essentially involves two main steps: estimation of maximum ground deformations and surface accelerations from a free field ground response study, combined with static analysis considering the surface acceleration and superstructure mass. In the present study, dynamic behavior of underlying soil strata was investigated using two high-quality element testing techniques—resonant column and dynamic simple shear tests. The dynamic soil properties were established and site-specific ground response study was conducted for the chosen site, using the artificially generated ground motions for the region. Equivalent static load was estimated from the surface acceleration obtained from free field ground response study. A three-dimensional finite element model has been developed and validated against the field lateral load test results. An increased magnitude of displacement and bending moment was observed with increased ground motion intensity. The peak bending moments induced for the scenario ground motions is higher than the plastic moment capacity of the pile section, displaying the probable failure of considered pile-supported structure.

Pradeep Kumar Dammala, Manoj Kumar Manne, A. Murali Krishna

### Earthquake Early Warning System

Earthquake early warning is considered as one of the real-time earthquake damage mitigation measures which detects seismic waves, analyzes and transmits information of the impending ground shaking at the potential user site. Earthquake warning is issued in order to reduce the damage caused by earthquake such as trains speed can be reduced, and people can move themselves to safer place. The basic requirement of an EEW system is the development of real-time algorithm for fast calculation of earthquake parameters. Earthquake warning is possible by detecting primary waves that travel more quickly than the secondary and Rayleigh waves. The reliable issuance of the warning depends on the accuracy of the calculated parameters. The parameters are estimated on the basis of initial portion of P-wave. Body waves are of two types, namely compressional waves and shear waves. Compressional waves or the P-waves are fast in velocity as compared to shear waves and are recorded first in the seismograph. On the other hand, shear wave or secondary waves are slower than P-wave, and most of the damage is caused due to S-wave. An EEW system warns about an area of forthcoming strong shaking, normally with a few tens of seconds of warning time before the arrival of destructive S-wave. Even a few sec warning will be useful for some emergency measures such as shut off gas pipelines to minimize fire hazards, to slow down rapid transit vehicles and safeguarding of computer facilities to avoid loss of data bases. This can be done by calculating EEW parameters such as τc and peak displacement from the initial 3 s of the P-waveform. With the help of these parameters, magnitude can be estimated, and warning can be provided.

Aarti Taneja, Aniket Desai, Ravi S. Jakka

### Dynamic Characteristics of Subsoil Deposit of Tripura by Nakamura Method

Determination of local site effect by calculating fundamental period and amplification of motion using Nakamura (Railway Tech Res Inst Q Rep 30:1–9, 1989) proposed H/V spectral ratio approach was recognized to be a simplified, reliable and well-accepted method. Both strong motion recordings and ambient noise recorded from micro-tremor can be used to construct the H/V spectral ratio. It is a well-known fact that the affect of body wave in an earthquake signal is relatively higher compared to Rayleigh wave and H/V spectral ratio approach is a useful method to differentiate the influence of both the waves. Tripura is one of the Northeastern states of India surrounded three sides by Bangladesh and rest by Assam which was categorized as the highest seismically vulnerable zone (BIS 2016). In fact, the geological history of Agartala, the capital city of Tripura, and other river valleys of Tripura are relatively young of Holocene age group. Significant depth of sedimentation with soft alluvial and fluvial type at top layers is also reported. Hence, the possibility of local site effect may lead to significant effects. From the above viewpoint, present study is an attempt to investigate dynamic characteristics and amplification ratio after analyzing strong motion records following Nakamura (Railway Tech Res Inst Q Rep 30:1–9, 1989) proposed H/V spectral ratio approach. The acceleration history record of January 3, 2017, earthquake epicentered at North part of Tripura is used to construct the H/V spectral ratio. Results indicate that peak amplitude of H/V spectra is recorded at around 1.65–1.75 Hz for both the sites, which comprises SH waves of higher energy content and further troughs are noted at higher frequencies confirming moderate effect of Rayleigh waves. This limited study highlights amplification potential in order of 1.65–1.75 Hz indicating influence of local site effect at various locations of Tripura and need of microzonation map of important towns.

Rajat Debnath, Rajib Saha

### Equivalent 1D Ground Response Analysis (GRA) of Black Cotton Soil for Three Different Sites Near Indore City

Seismic hazards have proved to be the most devastating having the potential for causing the greatest damages. The natures of forces and the energy that is released during an earthquake event are random in nature and unpredictable. To assess the hazards caused due to an earthquake, the quantification of the hazards becomes very important. As the soil profile of the site plays an important role in contributing to the hazards, ground response analysis is carried out for detailed analysis. In the current study, 1D ground response analysis has been carried out at three different locations near Indore, namely Reti Mandi (Indore), Manchaman, and Mahakal Temple (Ujjain) which have been subjected to two different earthquake motions namely Bhuj and Kobe’s Earthquake. Linear analysis using DEEPSOIL to estimate the free-field ground response has been carried out. The input parameters considered are input ground motion, shear wave velocity, damping ratio 5%, and dynamic soil properties. Standard penetration tests have been carried out at all the three sites at Indore. It is observed that the soil layers under study result in similar PGA after analyzing from both earthquake motions.

Deepshikha Shukla, Chandresh H. Solanki

### Pattern Recognition to Identify Susceptible Areas in Northwestern Himalaya

Regions in northern India, especially within the Himalayan arc, have experienced frequent disastrous earthquakes. Major seismic activity in India is concentrated along the geologically young and seismo-tectonically active Himalayan arc. An area between the latitude 25° N to 35° N and longitude 72° E to 90° E was considered for the study, which falls between the great Kangra earthquake of 1905 and the great Bihar–Nepal earthquake of 1934. The main objective of the study is to identify the areas of high seismic susceptibility using pattern recognition (PR) exercise. Areas which have experienced high seismicity and have complex tectonics are more prone to much frequent seismic activity in future and are defined as seismically susceptible areas. The pattern recognition technique started with the identification, selection, and extraction of features from the seismicity and tectonic data. Various features were identified from a circle of radius 25 km around each epicenter, known as the central earthquake. These features were then subjected to discriminant analysis, which constituted the training exercise of the PR technique. The discriminant functions obtained from this training exercise were then applied for the decision-making exercise to identify the susceptible areas. This resulted in the identification of susceptible area within the study area in the form of clusters. Various clusters were identified along the Himalayan arc, which are capable of producing damaging earthquake of significant magnitude. A dense cluster was observed between the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT), and Kishtwar Fault in west and Sundernagar Fault in east. The great Kangra earthquake is part of this dense cluster. A great amount of seismicity was also observed around MCT, east of Sundernagar Fault, in Uttarakhand and western Nepal. Epicenters of Uttarkashi (Mw = 6.8) and Chamoli (Mw = 6.7) earthquakes are within this cluster. Other dense clusters were also observed which trends transverse to the Himalayan arc and follows the Kaurik Fault system and in the vicinity of Lake Lighten Fault, in the Kashmir Tibet region.

Swati Singh Rajput, Ravi S. Jakka, Amita Sinvhal

### Modelling of Response of Tunnels Excavated in Squeezing Ground Condition

As a part of development of infrastructure in hill regions, many hydropower projects, all weather proof road and railway projects have been undertaken by the Government of India. The geology of hilly regions is very complex and fragile in nature. The rock masses are highly fractured and weathered. As a result, construction of large underground structures and their stability becomes a major issue in hilly regions. Therefore, it is necessary to understand the rock mass-tunnel support interaction in detail before any underground operation is undertaken in hilly regions. In this study, a case history of a Head Race Tunnel of Maneri Bhali Hydro-Electric Project Phase-I has been considered for investigation. The interaction phenomenon has been studied by using a novel finite element-based framework where elastic-perfectly plastic behaviour of poor rock mass is modelled by implementing actual Hoek–Brown yield criterion in association with non-associated plastic flow rule. Additionally, the elasto-plasticity in the behaviour of different tunnel support components has also been included in this framework. Under the scope of present study, tunnel convergence, plastic straining and the ground reaction curve were obtained for the considered tunnel section. The tunnel convergence obtained through present study is in good agreement with the field measured values of tunnel convergence. Hence, it can be said that the proposed framework is a convenient tool for detail analysis of the rock mass-tunnel support interaction and for design of supports of underground structures in poor-quality rock masses.

Dipaloke Majumder, M. N. Viladkar, Mahendra Singh

### Liquefaction Mitigation with Stone Columns for a Sewage Treatment Plant: A Case Study

Liquefaction of soil in the event of an earthquake is one among the major challenges in geotechnical engineering which may lead to catastrophic damages if proper mitigation measures are not provided. In this paper, a case study of a project site in Delhi (seismic zone IV) for a sewage treatment plant (capacity 318 MLD) has been considered. Based on the presence of poorly graded silty sand, low SPT N values and the presence of groundwater at shallow level, it has been worked out that the soil is susceptible to liquefaction. As a mitigation measure, ground improvement using vibro stone columns installed by dry bottom feed method has been adopted above which shallow foundations are proposed. CPTs have been performed on treated and untreated locations which have ascertained the improvement of soil, and the plate load tests performed have ensured the bearing capacity of the ground.

K. Ganesh Deepak, Jinu Mary Jacob

Reinforced soil has been successfully used in many geotechnical engineering applications where the soil as such is not strong enough to take up the loads. Many types of geosynthetics and fibers have been used as reinforcing elements. The study focuses on the use of multi-oriented reinforcements in improving the properties of the soil. Hexapods, horizontal–vertical orthogonal elements and 3D reinforcements are the three different types of 3D reinforcements used for soil stabilization. In the study, soil is reinforced with granular trenches that are reinforced with an optimum percentage of 3D inclusions. Triangular trenches having base width equal to twice the height (i.e., W/H = 2) are used for the study. Loads were applied through an automated and computer controlled hydraulic cyclic plate load testing equipment. Cyclic behavior of the reinforced soil is studied by conducting the tests at various amplitudes, i.e., 20, 40, 60 and 80% of ultimate static load. The frequency is maintained at 3 Hz. Similar study is carried out by varying the frequency, keeping the amplitude constant. It is seen that the reinforcements add an apparent cohesion to the cohesionless soil and also increase the angle of internal friction.

M. Hema, N. Unnikrishnan

### A Review on the Role of Geosynthetics in Preventing the Excessive Settlement and Mud Pumping of Ballasted Railway Track

Railways are the primary mode of public transport around the world and play a pivoting role in the day-to-day transportation needs of commuters. Hence, an improved railway track infrastructure demands high-quality control. Excessive settlement in rail tracks is a common failure phenomenon incurring an extra maintenance cost. Installation of railway tracks on soft grounds is a daunting task for any railway engineer. Inefficient drainage results in storage of impregnated water beneath the railway tracks. Consequently, under repeated wagon loading results in a phenomenon known as mud pumping. The present paper mainly reviews the role of geosynthetics to mitigate the mud pumping, thereby controlling the excessive settlement and degradation of the track geometry.

Ramesh Gedela, Rajagopal Karpurapu

### Strain Energy-Based Modeling of Soil Liquefaction Using Data-Driven Techniques

This paper presents the application of Gaussian Process Regression (GPR) and M5 Model Tree as two alternative data-driven modeling practices for prediction of soil liquefaction. The initial effective mean confining pressure (σ′mean), initial relative density after consolidation (Dr), percentage of fines content (FC), uniformity coefficient (Cu), Coefficient of curvature (Cc), mean grain size (D50), etc. are used as model inputs to predict strain energy density (W) required for triggering the liquefaction. The performance evaluation criteria like mean absolute relative error (MARE), coefficient of correlation (R), root mean square error (RMSE) for the validation datasets are found to be 6.381, 0.849, 0.266, respectively. Use of multiple statistical criteria and graphical plots confirmed the superiority of PuK Kernel-based Gaussian Process Regression (GPR) model over five different empirical models, two linear genetic programming (LGP)-based expressions, artificial neural network (ANN) and M5 Model Tree-based predictions. Further, a parametric sensitivity analysis performed on input parameters showed that σ′mean is the most influencing predictor to explain the variations of the capacity energy than other input parameters.