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This paper explores the geotechnical feasibility for constructing coastal reservoir in Arabian Sea off Mangaluru coast. This envisages storing fresh water in a reservoir along the coast by building a sea dike to impound the flood waters of Netravati River. On one side, the dike will ensure the required quantity of freshwater flow from Netravati River to the reservoir without being drained to the sea. On the other side, the sea dike will prevent seawater from entering the reservoir, avoiding the salt contamination of the freshwater supply. Present study presents detailed investigation of the soil profiles of surrounding region of Mangaluru to explore the site condition at off Ullal beach. Lithological data on the Netravati estuary were also presented with key observation on the soil profiles in the area proposed for location of coastal reservoirs. The key finding of the study is that the region offshore of Ullal is devoid of sand and is comprised mainly of soft Silty clays. Lithological data of nine foundations at Netravati Bridge near Ullal are also presented in this paper. Based on the findings of geotechnical investigations, the paper concludes that construction of sea dike in Arabian Sea off Mangaluru coast is feasible. [ABSTRACT FROM AUTHOR]

Rocks are generally regarded as linearly elastic even though the manifestations of nonlinearity are prominent. The variations of elastic constants with varying strain levels and stress conditions, disagreement between static and dynamic moduli, etc., are some of the examples of nonlinear elasticity in rocks. The grain-to-grain contact, presence of pores and joints along with other compliant features induce the nonlinear behavior in rocks. The nonlinear elastic behavior of rocks is demonstrated through resonant column tests and numerical simulations in this paper. Resonant column tests on intact and jointed gypsum samples across varying strain levels have been performed in laboratory and using numerical simulations. The paper shows the application of resonant column apparatus to obtain the wave velocities of stiff samples at various strain levels under long wavelength condition, after performing checks and incorporating corrections to the obtained resonant frequencies. The numerical simulation and validation of the resonant column tests using distinct element method are presented. The stiffness reductions of testing samples under torsional and flexural vibrations with increasing strain levels have been analyzed. The nonlinear elastic behavior of rocks is reflected in the results, which is enhanced by the presence of joints. The significance of joint orientation and influence of joint spacing during wave propagation have also been assessed and presented using the numerical simulations. It has been found that rock joints also exhibit nonlinear behavior within the elastic limit. [ABSTRACT FROM AUTHOR]

The wave propagation in jointed rock mass depends on many factors, in particular the wave frequency, existing stress conditions and the induced strain levels. When the wavelength of the propagating wave is much longer than the spacing of the joints, it is referred to as long-wavelength condition. This is a dominant condition in seismological studies due to the presence of closely spaced joints in rocks. A comprehensive study on long-wavelength propagation of shear and compression waves in very weak rocks has been carried out with the help of a resonant column apparatus using a model material (plaster of Paris) at various strain levels. The working principle and suitability of the apparatus for testing stiff samples are discussed. The velocity reductions of shear and compression waves across joints are obtained. The influence of frictional and filled joints in attenuating stress waves under various strain levels is analysed. Wave velocities are found to be reduced with increasing strain levels and decreasing joint spacing. The joints with gouge material are more efficient at damping the waves. It is recognised that wave velocity reductions and damping across joints are functions of confining stress and strain levels induced in very weak rocks. [ABSTRACT FROM AUTHOR]

Knowledge of wave propagation across rock joints is necessary for understanding distinctions between wave attenuation and lithology. Whenever a propagating seismic wave strikes a rock joint at an angle not normal to the joint, wave transformation occurs. The rock joints existing in the field are not oriented in the condition for normal incidence of the wave; hence, wave transformations are very common. In this paper, transformations of P and Sv waves have been modeled numerically with the help of a distinct element method. Validation of the numerical model has been carried out by comparing the wave velocities obtained from bender/extender elements. The dependence of the transformation of obliquely striking waves on the frequency of incident waves and stiffness of the joint has been studied. The velocities of propagating waves and the ratios of stress amplitudes of propagating waves with respect to the incident wave have been obtained and compared for all the possible angles of incidence. The wave velocities and amplitudes of propagating stress waves are found to be dependent on the angle of incidence of the waves at the rock joint. It was observed that the transformed waves that are of the same type as the incident wave contain more energy. [ABSTRACT FROM AUTHOR]

Geocells are three-dimensional expandable panels with a wide range of applications in geotechnical engineering. A geocell is made up of many internally connected single cells. The current study discusses the joint strength and the wall deformation characteristics of a single cell when it is subjected to uniaxial compression. The study helps to understand the causes for the failure of the single cell in a cellular confinement system. Experimental studies were conducted on single cells with cell pockets filled up with three different infill materials, namely silty clay, sand, and the aggregates. The results of the experimental study revealed that the deformation of the geocell wall decreases with the increase in the friction angle of the infill material. Experimental results were also validated using numerical simulations carried out using Lagrangian analysis software. The experiment and the numerical results were found to be in good agreement with each other. A simple analytical model based on the theory of thin cylinders is also proposed to calculate the accumulated strain of the geocell wall. This model operates under a simple elastic solution framework. The proposed model slightly overestimates the strains as compared with experimental and numerical values. [ABSTRACT FROM AUTHOR]

The results of the laboratory investigation performed on clay beds reinforced with natural (bamboo) and commercial (geosynthetics) reinforcement materials are reported in this paper. To use bamboo effectively, three-dimensional cells (similar to geocells) and two-dimensional grids (similar to geogrids) are formed using bamboo (termed bamboo cells and bamboo grids, respectively). The performance of clay beds reinforced with bamboo cells and bamboo grids is compared with that of clay beds reinforced with geocells and geogrids. The bearing capacity of the clay bed increased by six times when a combination of geocell and geogrid was used. The ultimate bearing capacity of the clay bed reinforced with bamboo cell and bamboo grid was found to be 1.3 times more than that of clay bed reinforced with geocell and geogrid. In addition, substantial reduction in the footing settlement and the surface deformation was observed. The tensile strength and surface roughness of bamboo were found to be nine times and three times, respectively, higher than geocell materials. The bamboo was treated chemically to increase its durability. Although the performance of bamboo was reduced by 15-20% after the chemical treatment, its performance was better than its commercial counterparts. [ABSTRACT FROM AUTHOR]

The demand for mineral products has increased substantially in recent years due to the rise in economic development. This results in the production of a significant volume of tailings waste. Due to this reason, the height (H) of existing tailings pond (TP) is frequently raised to accommodate the excess tailings released. This article presents a case study in which the stability of a TP, which was raised in phases to increase its storage capacity, is examined to understand its suitability for closure. While raising the heights in phases, geosynthetic reinforcements were introduced across the height of embankments to enhance the overall stability of TP. Furthermore, the height was increased by utilizing both downstream (D/S) as well as upstream (U/S) construction techniques. While examining the suitability of TP for closure, elaborate two-dimensional numerical simulations are performed to assess the overall stability of reinforced embankments of TP using finite-element-based software RS2. Initially, the stability analyses are carried out for the embankments at the end of final construction (i.e. after raising the height of TP) by utilizing the shear strength reduction technique. Subsequently, the stability of embankments is examined by incorporating the effect of seepage using partially coupled stress-seepage analyses. Results obtained from both analyses are expressed in terms of the critical strength reduction factor (SRF). Moreover, an attempt has been made to study the effect of beach width in determining the location of the phreatic line (which plays a vital role in assessing the overall stability of TP) within the TP. A decreasing trend in the SRF is observed when the beach widths behind the TP embankments are reduced from 5H to zero. Furthermore, the point of exit of phreatic line at the D/S slope of TP embankments is significantly lowered (for both D/S and U/S case) when the beach widths are increased from 0 to 5H. In addition, the critical SRF is observed to increase by 28.71% and 15.60% for D/S and U/S case respectively, when the geosynthetic reinforcements are used within the TP embankments. Overall, the TP in its current state is found to be stable, and with no further scope for raising, dry closure is recommended. [ABSTRACT FROM AUTHOR]

A detailed study on the postliquefaction undrained shear behavior of sand-silt mixtures at constant void ratios is presented in this article. The influence of different parameters such as density, amplitude of cyclic shear stress, and drainage conditions on the postliquefaction undrained response of sand-silt mixtures has been investigated, in addition to the effect of fines content. The results showed that the limiting silt content plays a vital role in the strength of the soil under both cyclic and monotonic shear loading. Both the liquefaction resistance and postliquefaction shear strength of the soils are found to decrease with an increase in the fines content until the limiting silt content is reached. However, further increase in the silt content beyond the limiting silt content increases the liquefaction resistance as well as the postliquefaction shear strength of the soils. It is also observed that these variations on the liquefaction and postliquefaction resistance of soils are closely related to the variations in relative density. [ABSTRACT FROM AUTHOR]

The effect of non-plastic fines (silt) on the undrained monotonic response of saturated and isotropically consolidated sand specimens prepared to various measures of their density was studied in detail through various approaches namely gross void ratio approach, relative density approach, sand skeleton void ratio approach, and interfine void ratio approach. Specimens of 50 mm in diameter and 100 mm in height were tested at a rate of loading of 0.6 mm/min for this purpose. The limiting silt content and the relative density of a specimen were found to influence the undrained monotonic response of sand-silt mixtures to a great extent. Undrained monotonic response was observed to be independent of silt content at very high relative densities; however the presence of fines significantly influenced this response of loose to medium dense specimens. Individual and combined analyses of undrained monotonic peak strengths which are closely related to the liquefaction related problems have been done in this paper to assess the variation patterns. [ABSTRACT FROM AUTHOR]

In this paper, the problem of site characterization is treated as a task of function approximation of the large existing data from standard penetration tests (SPTs) in three-dimensional subsurface of Bangalore, India. More than 2,700 field SPT values (N) has been collected from 766 boreholes spread over an area of 220-km2 area in Bangalore, India. To get N corrected value (Nc), N values have been corrected for different parameters such as overburden stress, size of borehole, type of sampler, length of connected rod. In three-dimensional analysis, the function Nc=Nc(X,Y,Z), where X, Y, and Z are the coordinates of a point corresponds to Nc value, is to be approximated with which Nc value at any half-space point in Bangalore, India can be determined. An attempt has been made to develop artificial neural network (ANN) model using multilayer perceptrons that are trained with Levenberg-Marquardt back-propagation algorithm. Also, a geostatistical model based on ordinary kriging technique has been adopted. The knowledge of the semivariogram of the Nc values is used in the ordinary kriging method to predict the Nc values at any point in the subsurface of Bangalore, India where field measurements are not available. The results obtained show that ANN model is fairly accurate in predicting Nc values. In case of ordinary kriging, a new type of cross-validation analysis shows that it is a robust model for prediction of Nc values. A comparison between the ANN and geostatistical model demonstrates that the ANN model is superior to Geostatistical model in predicting Nc values in the subsurface of Bangalore, India. [ABSTRACT FROM AUTHOR]

Two algorithms are outlined, each of which has interesting features for modeling of spatial variability of rock depth. In this paper, reduced level of rock at Bangalore, India, is arrived from the 652 boreholes data in the area covering 220 sq⋅km. Support vector machine (SVM) and relevance vector machine (RVM) have been utilized to predict the reduced level of rock in the subsurface of Bangalore and to study the spatial variability of the rock depth. The support vector machine (SVM) that is firmly based on the theory of statistical learning theory uses regression technique by introducing ε-insensitive loss function has been adopted. RVM is a probabilistic model similar to the widespread SVM, but where the training takes place in a Bayesian framework. Prediction results show the ability of learning machine to build accurate models for spatial variability of rock depth with strong predictive capabilities. The paper also highlights the capability of RVM over the SVM model. [ABSTRACT FROM AUTHOR]

In this paper an attempt has been made to evaluate the spatial variability of the depth of weathered and engineering bedrock in Bangalore, south India using Multichannel Analysis of Surface Wave (MASW) survey. One-dimensional MASW survey has been carried out at 58 locations and shear-wave velocities are measured. Using velocity profiles, the depth of weathered rock and engineering rock surface levels has been determined. Based on the literature, shear-wave velocity of 330 ± 30 m/s for weathered rock or soft rock and 760 ± 60 m/s for engineering rock or hard rock has been considered. Depths corresponding to these velocity ranges are evaluated with respect to ground contour levels and top surface levels have been mapped with an interpolation technique using natural neighborhood. The depth of weathered rock varies from 1 m to about 21 m. In 58 testing locations, only 42 locations reached the depths which have a shear-wave velocity of more than 760 ± 60 m/s. The depth of engineering rock is evaluated from these data and it varies from 1 m to about 50 m. Further, these rock depths have been compared with a subsurface profile obtained from a two-dimensional (2-D) MASW survey at 20 locations and a few selected available bore logs from the deep geotechnical boreholes. [ABSTRACT FROM AUTHOR]

This paper presents the results of numerical simulations using the three-dimensional discrete element method (DEM) on the critical state behaviour of isotropically compressed and rebounded assemblies of granular materials. Drained and undrained (constant volume) numerical simulations were carried out. From these numerical simulations of drained and undrained tests, it has been shown that the steady state is same as the critical state. Critical state for both isotropically compressed and rebounded assemblies form unique curved line that can be approximated by a bilinear line as proposed by Been et al. [Géotechnique 41(3): 365–381, 1991]. Further more, evolution of the internal variables such as average coordination number and induced anisotropy coefficients during shear deformation has been studied. [ABSTRACT FROM AUTHOR]

The article reports on the result of the evaluation of undrained response from drained triaxial shear tests using discrete element methods (DEM) simulations and experiments. It was observed from the numerical simulations using DEM that an excellent correlation exists between the predicted undrained shear response from drained triaxial simulations and undrained shear simulations. The result shows that DEM simulations can simulate undrained shear response realistically, without explicitly incorporating pore water pressures. However, from the laboratory experiments on sand samples, it was observed that there is some scatter in the predicted undrained shear test results from drained triaxial tests, when compared with the undrained shear test results.

The determination of the overconsolidation ratio (OCR) of clay deposits is an important task in geotechnical engineering practice. This paper examines the potential of a support vector machine (SVM) for predicting the OCR of clays from piezocone penetration test data. SVM is a statistical learning theory based on a structural risk minimization principle that minimizes both error and weight terms. The five input variables used for the SVM model for prediction of OCR are the corrected cone resistance (qt), vertical total stress (σv), hydrostatic pore pressure (u0), pore pressure at the cone tip (u1), and the pore pressure just above the cone base (u2). Sensitivity analysis has been performed to investigate the relative importance of each of the input parameters. From the sensitivity analysis, it is clear that qt=primary in situ data influenced by OCR followed by σv, u0, u2, and u1. Comparison between SVM and some of the traditional interpretation methods is also presented. The results of this study have shown that the SVM approach has the potential to be a practical tool for determination of OCR. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a geostatistical model to evaluate the spatial and depth variability of Standard Penetration Test (SPT) data from Bangalore, India. The database consists of 766 boreholes spread over a 220 km2 area, with several SPT values (N) in each of them. The geostatistical analysis is done for N corrected (Ncorrected) values. The Ncorrected value has been corrected for different parameters such as overburden stress, size of the bore hole, type of sampler, hammer energy and length of the connecting rod. The knowledge of the semivariogram of the SPT data is used with kriging theory to estimate the values at points in the subsurface of Bangalore where field measurements are not available. The model is used to compute the variance of estimated data. The model predicts reasonably well the SPT data. The geostatistical model provides valuable results that can be used for seismic hazard analysis, site response and liquefaction studies for the development of microzonation maps. The predicted N values from the developed model can also be used to estimate the subsurface information, allowable bearing pressure of soils and elastic modulus of soils. [ABSTRACT FROM AUTHOR]

Recent developments in studies of soil response to earthquake loadings have made it possible to incorporate the rates of pore water pressure build-up in soils in to nonlinear response analyses of the grounds. Such pore pressure changes help in computing the changes in stress-strain behaviour of soils in the deposit progressively as the earthquake progresses. The rate and magnitude of pore pressure generation in soils during seismic loading will have important effects on the shear strength, stability, and settlement characteristics of a soil mass, even if the soil does not liquefy. The results in terms of pore pressure response in soils from a series of experimental investigations using strain-controlled cyclic triaxial tests on soils samples collected from liquefied sites are presented in this paper. The effect of relative density, amplitude of cyclic shear strain, number of loading cycles, confining pressure and frequency of cyclic loading on the pore pressure build-up are studied. Analytical expressions are proposed using regression analysis to define mean relationships between normalized pore water pressure and normalized cycles for the prediction of pore water pressure build-up in silty sands. Also, the pore water pressure build-up in soils is independent of frequency of loading. [ABSTRACT FROM AUTHOR]

A simple practical equivalent continuum numerical model for simulating the behavior of jointed rock mass has been extended to three-dimensional using FLAC3D. This model estimates the properties of jointed rock mass from the properties of intact rock and a joint factor (Jf), which is the integration of the properties of joints to take care of the effects of frequency, orientation, and strength of joint. A new FISH function has been written in FLAC3D specifically for modeling jointed rocks using the Duncan and Chang hyperbolic model. This model has been validated first with simple element tests at different confining pressures for different rocks with different joint configurations. Explicit modeling of the joints has also been done in element tests and results obtained compare well with the results of equivalent continuum model and also with experimental results. Further, this has been applied for a case study of a large underground power house cavern in the Himalayas. The analysis has been done under various stages of excavation, assigning a null model available in FLAC3D for simulating the excavation. [ABSTRACT FROM AUTHOR]

The effect of a base geogrid layer below the geocell mattress in sand, sand overlying soft clay, and soft clay foundation beds has been studied using a series of laboratory scale load tests. A rigid circular model footing was used to apply static monotonic loading on the foundation beds with and without geocell reinforcement. The model test results show that the provision of an additional layer of planar geogrid at the base of the geocell mattress further increases the performance of the footing in terms of bearing capacity and reduction in surface heave of the foundation bed. It is also observed that the beneficial effect of the base geogrid layer becomes negligible with increasing height of the geocell mattress beyond the influence of the depth of the footing. Strain measurements in the base geogrid layer indicate that it is more effective with the limited heights of the geocell mattress. The earth pressure cells embedded in the subgrade soil provide evidence that when the base geogrid is provided below the geocell mattress, the footing pressure is distributed more uniformly over an extended area. [ABSTRACT FROM AUTHOR]

The potential benefits of geocell reinforcement in soft clay foundations have been studied by a series of laboratory-scale static load tests on a rigid circular footing placed on a fill surface. Parameters of the test program include depth of placement of the geocell layer, width and height of the geocell layer, and influence of an additional layer of planar geogrid at the base of the geocell mattress. With the provision of geocell reinforcement, the load-carrying capacity of the soft clay foundation can be improved by a factor of up to 4.8 times that of the unreinforced soil. Heaving of the soil can be reduced substantially by providing geocell reinforcement of sufficient height and width. Further improvement in performance could be obtained with the provision of an additional layer of planar geogrid at the base of the geocell mattress. [ABSTRACT FROM AUTHOR]

This paper describes laboratory model tests to determine the bearing capacity of an embedded circular footing supported by multiple layers of geogrid-reinforced sand beds. The embedment depth ratio of the footing was varied from zero to 06. The tests were conducted with one variety of geogrid in sand compacted to 70% relative density. Besides load settlement data, deformations on fill surface, strain in geogrid layer and pressure distribution in soil subgrade (below the geogrid layers) were measured. The test results demonstrate that the ultimate bearing pressure increases with embedment depth ratio of the foundation. With the provision of multiple layers of geogrid reinforcement in the sand bed, high-performance improvement is obtained, in terms of both increase in bearing capacity and reduction in surface deformation. Also, the footing pressure is redistributed more uniformly over a wider area on the subgrade soil. Strain measurements in the geogrid layers indicate that the geogrid reinforcement is more effective in the region below the footing width. [ABSTRACT FROM AUTHOR]

This paper deals with the statistical analysis of the uniaxial compressive strength and of the elastic modulus of jointed rock masses under different confining pressures. Properties of the rock masses with different joint fabric, with and without gouge have been considered in the analysis. A large amount of experimental data of jointed rock masses from the literature has been compiled and used for this statistical analysis. The uniaxial compressive strength of a rock mass has been represented in a nondimensional form as the ratio of the compressive strength of the jointed rock to the intact rock. In the case of the elastic modulus, the ratio of elastic modulus of jointed rock to that of intact rock at different confining pressures is used in the analysis. The effect of the joints in the rock mass is taken into account by a joint factor. The joint factor is defined as a function of joint frequency, joint orientation, and joint strength. Several empirical relationships between the strength and deformation properties of jointed rock and the joint factor have been arrived at via statistical analysis of the experimental data. A comparative study of these relationships is presented. The effect of confining pressure on the elastic modulus of the jointed rock mass is also considered in the analysis. These empirical relationships are incorporated in a nonlinear FEM code to carryout the equivalent continuum analysis of jointed rock masses. The method presented in this paper recognizes that the jointed rock mass will act both as an elastic material and a discontinuous mass. The results obtained by the model with equivalent properties of the jointed rock mass predict fairly well the behavior of jointed rock mass. [ABSTRACT FROM AUTHOR]

Existing Ground Motion Prediction Equations (GMPE) in practice for North East India have been developed using limited or simulated datasets of recorded ground motions. The current study presents the development of a new GMPE based on a well-established model considering actual recorded ground motion data comprising of acceleration, magnitude, and hypocentral distances. A larger dataset with magnitudes ranging from 4.2 to 6.9 and up to 640 kms, with a total of 204 recordings is used in non-linear multiple-regression. The newly developed GMPE could predict ground acceleration realistically over larger ranges of distance and magnitudes, compared to existing GMPEs. [ABSTRACT FROM AUTHOR]

A comprehensive deterministic seismic hazard assessment (DSHA) of the north and central Himalayas (NCH) is attempted in the current study using recently developed strong-motion data-based region-specific ground motion prediction equations (GMPEs). Two source models, linear and point sources are used for hazard assessment. An updated seismotectonic map of the NCH is developed by identifying and merging the seismic sources from the Seismotectonic Atlas (SEISAT 2000) developed by the Geological Survey of India and recent literature, and a homogenized, declustered up-to-date earthquake catalogue with events since 250 BC. The NCH is divided into grids of size approximately 5 km × 5 km, and the bedrock level peak ground acceleration (PGA) at the center of each grid point is estimated using a region-specific GMPE considering both source models. The PGA values estimated at these points are exported to a GIS platform to develop a seismic hazard map of the region, separately for different sources, average and maximum of both the sources. It is observed from the current study that the PGA estimated is apparently greater than what is recommended in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the NCH. Research highlights: SHA based on the state of the art DSHA technique has been carried out using various source models and recently developed region-specific GMPEs with an updated homogenized and declustered catalogue. Deterministic Seismic Hazard contour maps have been developed representing the bedrock level horizontal acceleration developed using linear and point sources. The newly developed hazard maps for the North and Central Himalayas shows higher PGA in the range of 0.4g to 0.7g towards the plate boundary region and a decreasing trend towards the peninsular shield region and the southern alluvial plains, except at the National Capital Region. The PGA estimated are comparatively higher than the design horizontal acceleration prescribed for these regions in BIS 1893. [ABSTRACT FROM AUTHOR]

A new region-specific Ground Motion Prediction Equation (GMPE) was developed for the North and Central Himalayas purely based on recorded strong motion data. The GMPE was generated using multiple-regression, considering ground acceleration, magnitude, and hypocentral distance. An updated larger dataset was used in the present study, making the new equation applicable to a larger magnitude range of 4.1 to 7.8 and distance range up to 1560 kms, thus overcoming a major limitation of currently available region-specific GMPEs. The new GMPE was validated and observed to predict ground acceleration more accurately with noticeably less residuals as compared to existing GMPEs. [ABSTRACT FROM AUTHOR]

Recently developed region-specific GMPEs are used for a comprehensive seismic hazard analysis (SHA) of the North and Central Himalayas (NCH) using a probabilistic approach considering two source models. Vulnerable seismic sources in the areas are identified based on the Seismotectonic Atlas (Dasgupta et al. 2000), published by the Geological Survey of India. An up to date, homogenized and declustered earthquake catalogue is compiled from various sources, with earthquake data since 250 BC, to create a new digitized seismotectonic representation of the region. Regional seismic zones having similar seismicity are recognized based on the Gutenberg-Richter (GR) parameters and the region is delineated into 5 seismic zones. The study area is divided into grids of size 0.05° × 0.05° and the hazard in terms of Peak Ground Acceleration (PGA) at the centre of each grid point is estimated and presented as hazard maps for individual seismic sources, maximum of all sources, and average of both sources. From the current study, it could be concluded that the PGA estimated in the regions is comparatively higher than what is reported in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the region. [ABSTRACT FROM AUTHOR]

The present study attempts to assess the seismic hazard parameters (a, b and M c) and their spatial variation in western Himalaya, central Himalaya and Indo-Gangetic plain areas (19–38 ∘ N and 72–91 ∘ E ). The earthquake catalogue is prepared from different available sources, within a region of 500 km surrounding the study area, in moment magnitude scale. The maximum likelihood estimation method is used for spatial variation of seismicity parameters. The study area is disaggregated into small grids of 0.5 ∘ × 0.5 ∘ , and the spatial variation of seismicity parameters is analysed for the complete catalogue period. A significant variation in seismicity parameters is observed while moving from west to east along the Himalayan belt within the study area. Due to significant variations in seismicity parameters, instead of assigning a lumped value of seismic hazard parameter to the entire region, distributed seismic hazard parameter is assigned by dividing the entire area into five zones, of similar level of seismicity. The estimated seismicity parameter a for these zones varies from 4.28 to 6.18, and for b, it varies from 0.80 to 1.03. Using these Gutenberg–Richter parameters a and b, the present study estimated the return periods and probability of different magnitudes of earthquake for each zone. [ABSTRACT FROM AUTHOR]

Information about the topics discussed at a workshop held at the Centre for the Infrastructure Sustainable Transport and Urban Planning, Indian Institute of Science, Bangalore, India on April 22, 2010 is presented. Topics include the significance of transport sector in modern economies, the state of the road infrastructure and the implementation of intermodal transport. It also featured several executives in the transport industry including Kota Harinarayana, Ashish Verma and Anurag Kumar.

Geotextiles and geogrids have been in use for several decades in variety of geo-structure applications including foundation of embankments, retaining walls, pavements. Geocells is one such variant in geosynthetic reinforcement of recent years, which provides a three dimensional confinement to the infihl material. Although extensive research has been carried on geocell reinforced sand, clay and layered soil subgrades, limited research has been reported on the aggregates/ballast reinforced with geocells. This paper presents the behavior of a railway sleeper subjected to monotonic loading on geocell reinforced aggregates, of size ranging from 20 to 75 mm, overlying soft clay subgrades. Series of tests were conducted in a steel test tank of dimensions 700 mm × 300 mm × 700 mm. In addition to the laboratory model tests, numerical simulations were performed using a finite difference code to predict the behavior of geocell reinforced ballast. The results from numerical simulations were compared with the experimental data. The numerical and experimental results manifested the importance that the geocell reinforcement has a significant effect on the ballast behaviour. The results depicted that the stiffness of underlying soft clay subgrade has a significant influence on the behavior of the geocell-aggregate composite material in redistributing the loading system. [ABSTRACT FROM AUTHOR]

A numerical simulation of laboratory model tests was carried out to develop an understanding of the behaviour of geocell-reinforced sand, and soft clay foundation beds under a circular footing. The influence of the geometrical parameters of the geocell (width, and height, ) on the overall performance of the footing was investigated and the pressure-settlement responses of geocell-reinforced foundation beds were predicted and compared with the unreinforced test results. Simulations were also carried out on conventional-type planar geogrid reinforcement to study the relative performance of both reinforcement forms. The influence of the boundary constrains on the behaviour of the foundations was also studied. In all the cases, good agreement between the results obtained from numerical simulations and laboratory experiments was observed. The results demonstrated that the geocell mattress redistributed the footing pressure over a wider area thereby improving the performance of the footing. The pressure-settlement responses corresponding to geocell-reinforced beds were found to be much stiffer in comparison with the unreinforced case indicating that a substantial reduction in footing settlement can be ascertained. The influence of rigid boundaries on the results of reinforced foundation beds in this study was found to be negligible. [ABSTRACT FROM AUTHOR]

Laboratory model test results for the bearing capacity of circular footings supported by geocell-reinforced sand beds are presented. Footing load-settlement response, deformations at the fill surface, strains in the geocell wall and pressure distributions below the geocell mattress were measured. The test results demonstrate that significant performance improvement can be obtained in terms of both increased bearing capacity and reduced surface deformation by providing geocell reinforcement in the sand bed. Pressure measurements indicate that the footing pressure is redistributed more uniformly over a wider area on the subgracle soil, indicating that the geocell-reinforced sand bed behaves as a composite mass. [ABSTRACT FROM AUTHOR]

North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0–480 km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended. [ABSTRACT FROM AUTHOR]