Papers by RAMENDU BIKAS SAHU
SYNOPSIS Investigation of collapse of a five storey residential building in Calcutta is described... more SYNOPSIS Investigation of collapse of a five storey residential building in Calcutta is described. The failure occurred soon after construction but, fortunately, before occupation. Detailed soil investigation revealed that a bowl-shaped depression, 5. 5 m deep, existed in the collapsed building area whichwassubsequentlyfilledup. Thefoundationra.ftwasplaced 5.325 m below ground level and the subsequent filling put an overburden pressure of varying magnitude resulting in non-uniform pressure on the subsoil. This was apparently not considered in design. Factor of safety was found to be low against bearing capacity failure and the building tilted towards the heavier load concentration. This caused over-stressing,in structural elements which gradually failed and ultimately led to the collapse of the building.
This paper studies the performance improvement due to the presence of Geocell layer at the base o... more This paper studies the performance improvement due to the presence of Geocell layer at the base of the embankment over soft clay deposit. The experimental study was carried out by conducting tests on model embankments overlying soft clay with reinforcement by Geocell mattress at the interface between the earthen embankment and soft clay foundation bed, by varying its parameters like aspect ratio (pocket size), and type of infill material. The experiments have also carried out for Unreinforced and Geogrid reinforced foundation soil beneath the earthen embankment, to show comparative performance and ground improvement due to soil reinforcement using Geocell mattress. Test results indicated a considerable percentage reduction in settlements, lateral deformations and percentage increase in ultimate capacity of Geocell reinforced embankments, over unreinforced and Geogrid-reinforced embankment.
ISH Journal of Hydraulic Engineering, 2014
The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Lecture notes in civil engineering, 2023
Geocells is being used in various geotechnical engineering applications, like, embankments, roadw... more Geocells is being used in various geotechnical engineering applications, like, embankments, roadways, railways, slope protection etc., in order to improve their overall performance. In the present study, behavior of a model embankment 400mm high constructed over a layer of geocell, formed using geogrid, without and with basal reinforment on top of a 550mm thick very soft foundation bed was studied under incremental load. Pressure was applied in increments on the top of the embankment and pressure-settlement behavior of the embankment was monitored continuously until the failure was reached. It was observed that improvement factor increases with the inclusion of basal reinforcement below the geocell layer with same pocket size of geocell.
International Journal of Geo-Engineering, 2021
Stress controlled cyclic triaxial tests have been carried out on coastal sand of Digha, West Beng... more Stress controlled cyclic triaxial tests have been carried out on coastal sand of Digha, West Bengal, India at different frequencies, confining pressures, relative densities and number of loading cycles for determination of influence of these parameters on cyclic strength (expressed in terms of cyclic stress ratio) and initial liquefaction of Digha sand. The test results provide evidence that increasing density of sand increases liquefaction potential, though it has been found that increase in effective confining pressure reduces cyclic strength of sand. Cyclic strength of sand decreases with increase of number of loading cycles at a specific density and a particular confining pressure. It has been observed that frequency of loading cycles does have any significant influence on the number of cycles for initial liquefaction of Digha sand. An empirical correlation has been developed on cyclic strength of sand based on these parameters and it has been found that this correlation fits qu...
Generally, for piled raft foundation predictions are made of pile load sharing and settlements at... more Generally, for piled raft foundation predictions are made of pile load sharing and settlements at the end of construction only. However, the time-dependent settlement of piled raft foundation has important role to play in design of piled raft resting on soft clay. In this paper, the results of laboratory model study on time dependent settlement of piled raft in soft clay were analyzed. This study aims to establish the importance of the consolidation settlement in the design of piled raft foundation on soft clay. Model tests were performed to evaluate the influence of raft size, pile spacing and length on the time dependent settlement of piled raft foundation. The result shows that settlement reduction ratio of piled raft reduces with the increase in pile to raft area ratio as well as slenderness ratio of the piles. Ratio of total settlement to immediate settlement increases with the increase in pile to raft area ratio.
Lecture Notes in Civil Engineering, 2021
International Journal of Geotechnical Engineering, 2021
Active earth pressure distribution against the braced wall depends on the mode of wall movement, ... more Active earth pressure distribution against the braced wall depends on the mode of wall movement, which may be translational or rotational. The pressure distribution is generally non-linear resultin...
International Journal of Geomechanics, 2018
Indian Geotechnical Journal, 2015
The construction of braced excavations in urban areas requires control of surrounding ground move... more The construction of braced excavations in urban areas requires control of surrounding ground movements since excessive ground movements damage adjacent properties. Reasonably good amount of work on numerical analysis and field studies on the estimation of ground surface settlement adjacent to excavation have been reported in the literature. However, theoretical studies or mathematical modeling have not been well addressed in the literature. This paper presents a simplified design approach for estimation of wall deflection where diaphragm wall is assumed as continuous beam. Earth pressure in the backfill side is taken as load, exerted on the beam and strut load along with earth pressure in cut side represents support of the beam. Peck’s earth pressure diagram for braced wall is used for load calculation while Terzaghi’s equation is considered to derive coefficient of modulus of subgrade reaction. Applicability of the proposed approach has been verified by comparing the estimated values of wall deflection with the measured values of three different case studies.
International Journal of Geotechnical Engineering, 2014
The paper deals with an experimental investigation of design parameters for nondisplacement pile ... more The paper deals with an experimental investigation of design parameters for nondisplacement pile in sand. The study was envisaged to find out the influence of stress level on the parameters like N q , d, K s tan d, etc. by performing laboratory tests on a steel pile buried in sand bed. In one set, the sand bed was subjected to controlled vertical stress, and in another set, controlled horizontal stress was applied. Density of sand was varied, and different stresses were applied to evaluate point bearing, shaft friction, and total capacities. The parameters required to predict the axial capacity of pile have been found to vary with stress applied on the sand bed. However, at higher stress range, the values have shown tendency to attain constant magnitude. The parameters at higher stress range have been found to tally more or less with those used in general engineering practice. A factor, friction ratio, which is generally used in interpreting static cone penetration test data, has been found to be about 2%.
Indian Geotechnical Journal, 2014
The construction of braced excavations in urban areas requires control of surrounding ground move... more The construction of braced excavations in urban areas requires control of surrounding ground movements since excessive ground movements damage adjacent properties. Design of this type construction involves proper estimation of soil parameters. Prediction of these soil parameters may be done by controlled laboratory tests simulating actual field conditions. Laboratory tests carried out with small size samples sometimes do not replicate the field situations comprising variations in soil properties with depth specially for stratified soils. So, field data are largely being used for estimation of various soil parameters related to analysis and design of braced excavations. Precise prediction of parameters is possible if inverse method is used as the identified parameters are representative of macroscopic soil mass as a whole. The present paper works out back-analysis of soil stiffness parameters on the basis of three reported case studies. Here the braced wall has been considered as a continuous beam with soil from backfill side is acting as load and strut as well as soil from cut side act as support. Optimization (both constrained and unconstrained) technique is used for predicting values of coefficients of soil subgrade modulus. The predicted deflections are found to be quite close to the measured values which support the proposed method of parameter estimation.
International Journal of Geotechnical Engineering, 2012
Braced excavation in urban areas requires control of ground movements as well as wall deflection.... more Braced excavation in urban areas requires control of ground movements as well as wall deflection. Generally, interpolation from empirical database or numerical analysis by finite element method is used for estimation of ground settlement. But these methods are relatively complex and sometimes important assumptions are invalid at different situations. A design approach for calculating ground settlement around excavation is proposed by Bolton & Osman (2006) assuming a plastic deformation mechanism. Here, this design method is extended on the basis of ground settlement profile suggested by Peck (1969) and reported case studies of Kolkata Metro Excavation(Som, 1991). From the assumed deformation function average shear strain mobilized in each zone is calculated. The Mobilized shear stress beneath and around the excavation are found by equating potential energy loss and work done by the soil within deformed zone. This stability equation may be useful for the designers to calculate ground surface movement and wall deflection at different stages of excavation at different depth.
SN Applied Sciences
In the present study, an advanced nonlinear finite-element based 3D numerical study has been carr... more In the present study, an advanced nonlinear finite-element based 3D numerical study has been carried out to investigate the effects of axial loading on dynamic response of soil-pile system in liquefiable layered soil deposits of Kolkata city. An advanced soil constitutive law based on multi-yield surface plasticity model implemented in fully-coupled u-p formulation is adopted for soil-fluid interaction and pore water pressure development reasonably. The present model is validated with the past experimental results. Then, a detailed systematic parametric study is performed for numerical simulation of pile failures in layered soil deposit under axial loading by taking into account various soil conditions, pile and ground motion parameters. It is seen that the depth of liquefaction (DL) is decreased from 11.5 to 1.5 m adjacent to the pile when the axial load on pile increases from 0 to 1327 kN. Parametric studies also reveal that the bending moment response of pile under axial loading ...
Indian Geotechnical Journal
Lecture notes in civil engineering, 2022
Lecture notes in civil engineering, 2022
Geomechanics and Engineering, 2021
The excess pore pressure increases under undrained cyclic loading which cause decrease in effecti... more The excess pore pressure increases under undrained cyclic loading which cause decrease in effective stress followed by possible failure in the soft soil. With the inclusion of vertical drains radial drainage allows quick dissipation of excess pressure during cyclic loading and thereby failure of foundation soil may be avoided. The present study aims for analytical closed-form investigation on soft cohesive deposit under radial flow consolidation through vertical drains with no smear when subjected to long-term rapid cyclic loading. The mathematical formulation of pore pressure including degree of consolidation under cyclic loading is developed by using Green
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Papers by RAMENDU BIKAS SAHU