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Jitendra Sharma
B.Eng.[Mumbai], M.Tech. [IIT-Kanpur], Ph.D.[Cantab]
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My research interests are in the area of classical Soil Mechanics and Geotechnical Engineering. I am particularly interested in fundamental soil behaviour assessed using Critical State Soil Mechanics framework, Geotechnical Centrifuge Modelling, Numerical Modelling of Soil-structure Interaction, Ground Improvement using Geosynthetics and Soft Ground Tunnelling. |
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Completed Research Projects
Geosynthetic-reinforced Embankments on Soft Clay
The UK Transportation Research Laboratory (TRL) sponsored this project. The total funding was $260,000 over three years. The project involved planning, design, execution and reporting of centrifuge model tests. Novel techniques for measuring the tension induced in the model geosynthetic reinforcement and for installation of model wick drains in the soft clay layer were developed. The major finding of the project was the relatively small contribution provided by the geosynthetic reinforcement towards the reduction of mobilized shear strength of the clay layer. The results from the project indicated that the main virtue of geosynthetic reinforcement is the reduction or total elimination of lateral thrust in the embankment. Therefore, it can not provide a significant improvement in the factor of safety against failure if the bearing capacity of the clay foundation is insufficient. The project has also established the advantages of using geosynthetic reinforcement in combination with wick drain installation for constructing embankments on very soft, normally consolidated clay layers. The results of this project are published in Computers & Geotechnics and Geotextiles & Geomembranes journals. Back to Top
Grouting to alleviate Ground Settlement due to Tunnelling
This project was sponsored by the UK Engineering and Physical Sciences Research Council (EPSRC) and involved experimental simulations of compaction and hydrofracture grouting using the Cambridge University 10 m beam and 2 m drum centrifuges. A total funding of $280,000 over three years was awarded for this project. A rather simple but powerful technique for the simulation of propagating surface settlement trough due to tunnel excavation was developed. This technique can be applied to a wide variety of physical modelling scenarios in geotechnical engineering. The results from this project established the importance of choosing the grouting location with respect to the tunnel heading. The results of this project are published in ASTM Geotechnical Testing Journal. Back to Top
Centrifuge Modelling of Anchor Piles for Deep-sea TLPs
A consortium of North American oil companies that included Shell, Conoco and Gulf Canada sponsored this project. It was a high-intensity, short-duration project with a total funding of $212,000 over a period of six months. It involved the investigation of the formation of gap around the pile when subjected to a large number of horizontal displacement cycles as well as the interaction between two piles connected by a rigid pile cap. The project has revealed that the depth of the zone of reduced resistance near the surface of the soil is not constant as assumed in current design practice. It was seen to be increasing as the magnitude of lateral load or displacement increased in successive cyclic loading sequences. The results from this project were directly used in the design of anchor piles for TLPs in the Gulf of Mexico. A paper based on the results of this project was published in OTC2004 conference and was given the Best Paper Award by the ASCE Coast, Oceans, Ports and Rivers Institute (COPRI). Back to Top
Radial Consolidation around Vertical Drains
The Government of Singapore provided the $215,000 grant for this project under the Academic Research Program. The project involved conducting large-scale laboratory tests that simulated radial consolidation around a vertical drain. Several important factors such as the smearing of the clay during installation of vertical drain and the discharge capacity of the vertical drains were taken into account. The spatial distribution of excess pore water pressure during the insertion and withdrawal of the mandrel was recorded continuously. The results of the laboratory tests were back-analyzed using a customized finite element code that took into account the variation of permeability with void ratio and non-linear relationship between the hydraulic gradient and the seepage velocity. The results have indicated the existence of a wider-than-expected disturbed zone around the vertical drain - partly due to smearing and partly due to change in void ratio due to dissipation of excess pore pressure. The project also confirmed the existence of non-Darcian flow in the soil that is in close vicinity to the vertical drain. Some of the results of this project are published in Canadian Geotechnical Journal and ASCE Geotechnical Special Publication No. 112. Back to Top
Modelling of Urban Soil-structure Interaction Problems
Since the beginning of my job as Assistant Professor at NTU, Singapore, I have taken a keen interest in numerical modelling of urban soil-structure interaction problems. Singapore faces a lot of such problems because of its small area and high population density, particularly in the Central Business District [CBD]. I have collaborated closely with the Land Transport Authority [LTA] and the Public Works Department [PWD] on the North-East Line project [NELP] and the Changi Airport Line project [CALP]. In particular, I closely followed the case history of deep excavation for the underground car park of a major hospital building next to existing metro tunnels. The tunnels and the diaphragm walls of the excavation were instrumented and this provided me with good quality field data that I back-analyzed using a geotechnical analysis software. The project identified the need to plan well in advance and to choose appropriate stiffness of tunnel lining. It was found that if the tunnels are likely to be subjected to soil movements due to adjacent construction, it is better to use relatively flexible lining system. The results of this project are published in Tunnelling and Underground Space Technology Journal and Proceedings of ITA World Tunnel Congress in Durban, 2000. Back to Top
Serviceability-based Design of Reinforced Embankments on Soft Clay
The project was funded by the University of Saskatchewan President's NSERC grant and the New Faculty Graduate Student Support provided by the College of Graduate Studies and Research. The project involved deformation analysis of unreinforced and reinforced embankments with the aim of proposing a serviceabilty criterion for the design of such embankments. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. While most design methods predict large magnitudes of mobilized tension, measurements from field trials and laboratory tests have indicated that the magnitude of mobilized tension is quite small. This can be attributed to the limited available shear strength of the clay-reinforcement interface. In most situations, the embankment is able to satisfy overall equilibrium only at the expense of exceeding the available shear strength at this interface. This results in the embankment undergoing large deformations and therefore, becoming unserviceable. Most design methods completely ignore the deformation of the embankment and do not allow for the slip at the clay-reinforcement interface. The proposed serviceability criterion limits the shear stresses applied at the clay-reinforcement interface to prevent excessive deformation of the structure caused by the slip at the clay-reinforcement interface. The results of this project are being prepared for publication in Geotextile & Geomembrane and Computers & Geotechnics. Back to Top
Soil-structure interaction of a braced deep excavation in an urban environment
This project was funded by the NSERC Discovery Grant program. It involved conducting finite element back-analyses of a well-documented case history of a braced deep excavation in an urban environment. The main objective of the project was to establish key parameters that control the influence of ground deformation caused by the deep excavation on the adjacent structures such as pile and raft foundations, tunnels and buried pipes. The main outcome of the project was the development of a preliminary design chart for estimation of ground deformations around a deep excavation on the basis of the stiffness of the retaining wall and the stiffness of the ground. A paper describing the finite element back analyses is currently under review for publication in the Indian Geotechnical Journal. A second paper based on the design chart is being prepared for Geomechanics & Geoengineering. Back to Top
Shear strength of geomembrane-soil interface under unsaturated conditions
This project was run in collaboration with my colleague Dr. Ian Fleming and was funded by the NSERC Discovery Grant program. A series of interface direct shear tests were conducted using a smooth HDPE geomembrane and an unsaturated silty sand. A miniature pore-water pressure transducer was installed at the interface to monitor the changes in matric suction during shear. It was found that matric suction present in the unsaturated soil affects the shear strength behaviour of the interface at low normal stress values. At higher normal stress values, the behaviour is governed by soil particles embedding into the geomembrane. The findings of this project are published in Geotextiles & Geomembranes and Canadian Geotechnical Journal. The paper published in Geotextiles & Geomembranes was adjudged as one of the three best papers published in the journal in the year 2006. Back to Top
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