(25 years of research experience)
My core interest and expertise lies in teaching and research in geotechnical arena.
I am particularly interested in following:
No. | Details | Publications Total | Publications -2007 to 2016 |
---|---|---|---|
1 | Journal Publications | 175 | 124 |
3 | Geotechnical Special Publications | 7 | 7 |
3 | Books | 8 | 6 |
4 | Book Chapters | 8 | 5 |
5 | Edited Journals and Conference Proceedings | 14 | 10 |
6 | Conference Papers | 275 | 139 |
- | Total | 487 | 291 |
List of Five most important papers published (full papers enclosed)
Practical equivalent continuum model has been developed by establishing new sets of statistical relationships between the uni-axial compressive strength and elastic modulus of jointed rock mass versus the joint factor. These relations were arrived from statistical analysis of large amount of experimental data collected from different sources in literature and also carrying out some selected experiments. This experimental data covers a wide range of intact rock and joint fabric. Equivalent continuum model has been developed for the jointed rock by incorporating the statistical relationships arrived which expresses the joint rock properties as a function of intact rock properties and joint fabric.
Finite element model (program) has been developed for easy and efficient modeling of jointed rock mass using equivalent continuum approach. Also, new FISH function has been developed for the model using nonlinear hyperbolic model to incorporate in FLAC 2D and FLAC 3D programs. To corroborate the results, the analysis of the rock mass was carried out by modeling of the joints explicitly using the interface element along with an elasto-plastic material model for the intact rock. Different strength criteria available for jointed rocks were incorporated in the numerical analysis code.
A comparative study of the existing empirical strength criteria for jointed rocks was made to give a better insight in understanding the different failure criteria. Several large scale underground openings in jointed rock mass (such as Shiobara power cavern, Tokyo; Nathpha Jakri power house; Kirunavara mine slope) have been simulated using the developed practical equivalent continuum model and the obtained results compared very well with the field measurements of deformation in those structures at different locations.
Discrete Element Modeling (DEM) technique was used to obtain microscopic information at grain scale level and an attempt has been made to describe compaction behavior, strength mobilization and shear zone formation in granular materials as a result of micro-structural changes associated with macroscopic deformations. The effect of grain size and gradation of particle sizes on the mechanical behavior of granular media is being addressed. In order to explain the effect of size, gradation and confining pressure on the volume change and strength behavior of coarse grained soils, numerical simulations were carried out on a wide range of sizes, gradation and confining pressure using both 2-dimensional circular disc elements and 3-dimensional spherical elements based on Discrete Element Models (DEM). For this purpose the author had modified and developed new DEM programs and also several post-processing tools required for viewing the results. The long-term goal will be to develop a constitutive model for granular materials for transfer of research results to practical applications. More details, See
Increasing concern about the liquefaction of sandy grounds during earthquakes has prompted more comprehensive studies of granular media subjected to cyclic loading investigating into the mechanism of loss of strength, realized as a result of the progressive development of pore pressures. To explore in-depth understanding of the cyclic behavior of cohesionless soils, in this investigation, the granular media was considered as an assemblage of particles rather than as a continuum. In this investigation, numerical simulations were carried out using 2 - Dimensional assemblage of discs and 3-dimensional assemblage of spheres to address monotonic and cyclic behavior of sands from micromechanical considerations. The models were validated for both monotonic and cyclic loading conditions. Simultaneously extensive laboratory cyclic triaxial testing has been carried out to explain the liquefaction behaviour of sands from Bhuj, Ahmedabad and Assam areas. These results were compared with DEM modeling results to understand the fundamental processes at particulate level during liquefaction.
Geocell embedded foundations on sand, soft clay and layered sand-clay systems have been studied using well instrumented model experiments in the laboratory. A new concept of geocells for foundations for improving the bearing capacity of soils has been looked at using in-depth laboratory model testing studying the effects of pocket sizes, size of geocells, basal layers and other aspects. A study of the deformation and strength behaviour of reinforced soil foundations both under static and dynamic loading conditions below a circular foundation has been carried out extensively by varying many parameters coupled with numerical simulations using FLAC 3D.
The last two decades witnessed significant progress in the evaluation of local site effects and dramatic examples of its effect in reality during an earthquake as well. Prof. Sitharam’s contribution is in the area of local site effects to ascertain the effect of local soils on the buildings during an earthquake and its response to shaking. One needs to identify sub-regions within the urban centre (essence of microzonation) that will then respond in a similar way to peak horizontal acceleration induced by an earthquake. Microzonation studies carried earlier in India followed different procedures. Most of these studies lacked appropriate/ geotechnical/geophysical investigations required for seismic microzonation. Prof. Sitharam carried out microzonation of Lucknow (in Indo-Gangetic belt) and Bangalore city. For the first time, Prof. Sitharam studied the dynamic behavior of sandy soils from different parts of India through experiments to understand the strain dependent nonlinearity effects on soils, liquefaction and post liquefaction behaviour of sandy soils from India. It is here Prof. Sitharam’s contribution in understanding geotechnical characterization of Indian soils at a larger scale of 1:20000 for seismic microzonation. Studies carried out have generated amplification and peak ground acceleration (PGA) maps based on analysis of large amount of geotechnical data collated from large number of borehole data in different parts of the city and also geophysical data (measured shear wave velocity profiles). Acceleration time history at the ground surface and the response spectra have also been generated and presented for these cities. This is further confirmed through the ambient noise survey. Uncertainties in source parameters and propagation effects have invariably limit our ability to resolve site response. Based on the available data, ground motions have been simulated and expected Peak Ground Accelerations (PGA) at rock depths were calculated based on deterministic as well as probabilistic methods and in some cases using source models. Microzonation of Bangalore and Lucknow has been carried out scientifically with detailed geophysical tests using Multichannel Analysis of Surface Waves technique supported by large number borehole/SPT test data and appropriate methods to evaluate the ground response analyses to evaluate the hazard accurately at the ground surface. Geophysical methods overcome the drawback of exploring on larger volumes and some of the other problems inherent in conventional geotechnical investigation techniques. Prof. Sitharam extended the concept for the evaluation of seismic hazard for South India considering local site effects using probabilistic and deterministic approaches incorporating logic tree methodology considering events and earthquake sources within 300km from the boundary. The effect of particle shape on the macroscopic response of the granular matter under monotonic and cyclic undrained loading conditions were studied using particulate models to understand dynamic behaviour, liquefaction and post liquefaction behaviour.
Sustainable Development Issues and Directions in Urban Science and Engineering have been attempted which includes seismic microzonation of urban areas, smart city technologies, a framework to measure socio-economic impact of developmental programmes including performance assessment of public transport corporations.
While damaging effects of earthquakes have been known for long time, the contribution of soils to the magnitude and pattern of earthquake damage was not widely appreciated until recently. The local geological and soil conditions can profoundly influence all of the characteristics – amplitude, frequency content, and duration – of strong ground motion. Significant earthquake damage and loss of life has been directly related to the effect of local site conditions and liquefaction in several recent earthquakes (eg., 1985 Mexico earthquake, 1989 Loma Prieta Earthquake, 1994 Northridge, 1995 Kobe Earthquake, and Bhuj earthquake 2001). The local site effects play an important role in earthquake resistant design. Both the local site conditions and liquefaction related damage are very essential component of a comprehensive assessment of seismic hazard and are attributed to geotechnical / geophysical characteristics of soil overburden closure to the ground. A complete site characterization is essential for the seismic site classification and site response studies, which are carried out by detailed geotechnical/geophysical investigations. There is a clear role for geological and geotechnical data in evaluating the ground motions and in turn in the study of seismic hazard and preparation of geotechnical data driven microzonation maps to provide an effective solution for city planning. We have carried out seismic microzonation of Bangalore urban centre and Lucknow (capital city for Uttara Pradesh) urban centre and national documents have been released. Seismic microzonation of Agartala urban centre (capital of Tripura) and Izwal (capital city of Mizoram) have also been completed. We have also completed the work of seismic microzonation of Indira Gandhi Centre for Atomic Research at Kalpakkam. I was also involved as one of the member of Seismic microzonation of Delhi (NCR) region, which is being carried out by IMD-EVRC. Further, as a convener of the subgroup on geotechnical investigations at National Disaster Management Authority (NDMA), Govt of India carried out detailed deliberations at Department of Civil Engineering, Indian Institute of Science, Bangalore under the chairmanship of Honorable member of NDMA, we have prepared a national document on the geotechnical / geophysical investigations for seismic microzonation studies of urban centers in India. This report is going to pave the way for taking up seismic microzonation studies on a scientific and rational basis in several urban centers in India.
A book on “earthquake preparedness “has been prepared highlighting Do’s and Don’ts during and after earthquakes for different stakeholders. This has been translted in to Bengali, Nepali, Gujarati, Hindi. Plans to translate this into all the languages in zone IV and Zone V.
Urban development in developing countries has become a greater challenge as more than half of the planet’s population (over three billion people) lives in urban areas and particularly more in developing countries in Asia and Africa. Global urbanization process should be supported rather than fought considering the structural nature of urbanization and its contribution to the country’s economic, social and cultural development. Cities and the Environment should be made sustainable and the role of technology assumes greater importance to effectively contribute to the sustainable development of cities. Technological innovation characterizes our society in India today and more so in our city Bangalore. Bangalore city plays a major role in the dissemination of the information and communication technologies. These technological innovations is both a cause and consequence of urban development and urbanization, playing the leading role in the structuring of our cities and also embodying the response to the new emerging needs of the people living in our cities. In this direction, a large collaborative project has been submitted to Robert Bosch Centre at IISc jointly with Bangalore Metropolitan Transport Corporation (BMTC) and IBM-India Research Lab. Three workshops and three symposiums have been organized to address the smart city technologies in the year 2011-2012. The details are as follows:
Symposium on "Smart Mobility and Energy Concepts for Megacities" on 19th May 2011 This symposium is part of the initiative of the National Academy of Science and Engineering under the project "German Indian Partnership for IT Systems (GRIP IT)". The project funded by the German Federal Ministry of Education and Research is planned to act as a catalyst for future research and development collaborations between India and Germany by bringing together the German and Indian Partners from the world of academics and industry. The focus of the symposium is on Smart Cities and its major components of Mobility and Energy.
The objective of this symposium is to set the platform for discussion on some of the significant factors such as the socio-economic challenges by megacities, urban governance topics, citizens' engagement, role of NGO's etc, for the effective deployment of technology to make cities smarter to overcome the challenges of rapid urbanization in India.
Symposium – Smart City Technologies as Innovation drivers on 25th April 2012: There are many attempts by the international community’s urging the need for transfer of urban technologies adapting to the major problems confronting public authorities, economic providers and users in the domains of transport, water, energy, sanitation, health, education and habitat considering environmental, social and economic aspects. ICT’s such as mobile information and communication systems with wireless sensor networks offer promising potential for the environment in developing countries. ICT’s can provide innovative solutions that will encourage sustainability along with new tools for disaster risk reduction. The technology is always connected to other technical and social networks and also on global trends and markets. Technologies used or developed in developing countries are characterized by their great diversity created through the use of ancient traditions and thus they are more socially and technologically more innovative. Some of the details can be found in CiSTUP reports:
Efforts are also done to create examples on Non motorized transport in our campus by proposing a rent a bicycle system in IISc and e-mobility .
The performance evaluation of public bus transport operations in Karnataka has been done by using quantitative and qualitative data collected from four state run transport units (SRTUs), namely Karnataka State Road Transport Corporation (KSRTC), North West Karnataka Road Transport Corporation (NWKRTC), North East Karnataka Road Transport Corporation (NEKRTC) and Bangalore Metropolitan Transport Corporation (BMTC). KSRTC, NWKRTC and NEKRTC are public transport organizations connecting cities and villages and BMTC is an urban public transport organization. Mysore city bus transportation has been studied for impact of intelligent transport system (ITS) on Mysore city transport. Quantitative data is analyzed by ratio analysis and benchmarking technique to determine the possible savings from fuel, staff and capital expenditure, this technique gives only financial statement analysis, since it compares the performance of the SRTUs or divisions or depots with respect to the top performing entity in its peer group, in order to evaluate the profitability of SRTUs or divisions or depots. For analyzing multiple inputs and outputs, non-parametric and multivariate techniques such as data envelopment analysis (DEA) is used along with multivariate techniques such as principal component analysis (PCA) and analytical hierarchy process (AHP). The results show that bootstrapped-DEA is ideally suited for quantitative analysis of SRTUs of Karnataka. A comprehensive study on the all the SRTUs of Karnataka at depot, division level are done and determined which quantitative method is suited for depot level, division level and SRTU level studies. The methodology for qualitative data collection and analysis to know the performance has also been arrived from this work. User and operator perception studies of different SRTU’s of Karnataka have been done to evaluate the performance of these corporations from qualitative techniques. Operation and financial performance including profitability studies of Mysore urban transportation (Mysore city transport division) has been carried out before and after implementation of intelligent transport system (ITS). The optimization technique is used to solve the dead kilometer problem of BMTC routes. The dead kilometer minimization model was formulated, which is a mixed integer programming problem, to get the optimal solution considering the capacity of the depot and time period of operation for the chosen network. An optimization technique has been developed for solving the dead kilometer problem in the operations of BMTC buses for the Volvo division. The alternative depot locations have been identified to reduce the dead kilometer, leading to large amount of savings for the corporation. From the detailed analyses using non parametric techniques, multivariate and multi-criteria techniques along with perception surveys, strategies and recommendations have been arrived at to improve performance of the public transport corporations.
The main objective of this research is to evaluate the socio economic impact of the development programs like JnNURM, development of Roads project etc, on the intended target area of in and around Bangalore. Data Envelopment Analysis is used to evaluate the distance function in the calculation of Malmquist index (MI). MI gives the productivity change between two time periods and is calculated as the geometric mean of two ratios measured with reference to the time period and time period respectively. A new approach is presented by interpreting the two ratios of MI separately using the distance functions to identify the productivity change between two time periods. Two case studies were considered. The impact of implementation of Jawaharlal Nehru National Urban Renewal Mission (JnNURM) on Bangalore Metropolitan Transport Corporation (BMTC) is studied using the proposed method. Also the socio economic impact of the roads developed by Government of Karnataka under the name of “5054-Decongestion of Roads project” in and around Bangalore was also studied.
Involved in very important projects for the nation such as Dynamic testing and analysis of foundations for Human Centrifuge at Indian Aerospace medicine at Bangalore, Dynamic property evaluation for foundation design of 3 axis motion simulator at ADE, Bangalore, Moon Tracking 32m and 18m dia antenna foundation investigations and design for ISTRAC and ISRO (Dept of Space), 32m dia antenna foundation design at Nazafgarh, New Delhi. Dynamic stability of compacted sand fill in the Nuclear Island, PFBR project for IGCAR, Kalpakkam, India.
Also, responsible for designing more than 25 designs of raw water ponds, ash ponds, red mud ponds, and tailing ponds across India. Evaluated hazard and developed design response spectra for design of offshore pipeline and onshore platform in Yemen.