G. R. Dodagoudar

Bio: G. R. Dodagoudar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Finite element method & Seismic hazard. The author has an hindex of 14, co-authored 64 publications receiving 767 citations. Previous affiliations of G. R. Dodagoudar include Indian Institute of Technology Bombay & Indian Institutes of Technology.

Modelling of contaminant transport through landfill liners using EFGM

Abstract: Modelling of contaminant transport through landfill liners and natural soil deposits is an important area of research activity in geoenvironmental engineering. Conventional mesh-based numerical methods depend on mesh/grid size and element connectivity and possess some difficulties when dealing with advection-dominant transport problems. In the present investigation, an attempt has been made to provide a simple but sufficiently accurate methodology for numerical simulation of the two-dimensional contaminant transport through the saturated homogeneous porous media and landfill liners using element-free Galerkin method (EFGM). In the EFGM, an approximate solution is constructed entirely in terms of a set of nodes and no characterization of the interrelationship of the nodes is needed. The EFGM employs moving least-square approximants to approximate the function and uses the Lagrange multiplier method for imposing essential boundary conditions. The results of the EFGM are validated using experimental results. Analytical and finite element solutions are also used to compare the results of the EFGM. In order to test the practical applicability and performance of the EFGM, three case studies of contaminant transport through the landfill liners are presented. A good agreement is obtained between the results of the EFGM and the field investigation data. Copyright © 2009 John Wiley & Sons, Ltd.

An integrated geotechnical database and GIS for 3D subsurface modelling: Application to Chennai City, India

Abstract: Subsurface characterization and clear distinction between layer boundaries in geological profiles are essential for successful completion of engineering projects. Due to limitations in accessing the vast and diverse subsurface information, efficient management of geotechnical data is of special importance. This study presents the methodology of building a digitally formatted and integrated spatial database using geotechnical data and geographic information system (GIS). The development of comprehensive geotechnical (geo)-database involves (1) Collection of borehole data from various reputed sources, (2) Validation of data in terms of accuracy and redundancy and (3) Standardizing and organizing the geotechnical information for incorporating into the database. The database is then integrated with GIS to provide the advantage of visualizing, analysing and interpreting the geotechnical information spatially. In addition, stratigraphic data stored within the spatial database is utilized for constructing three-dimensional (3D) subsurface models. A simplified approach is developed for 3D subsurface modelling with a combination of the Relational database management systems (Microsoft Access), Arc-GIS and Spatial interpolation techniques. The proposed methodology is illustrated using nearly 175 borehole data collected from various projects aimed at providing an exhaustive database and an integrated 3D environment for the Chennai City of south India for better interpretation and decision-making in regard to sustainable urban development. The study also demonstrates the application of the developed subsurface model in evaluating the effectiveness of multichannel analysis of surface wave (MASW) tests to estimate the depth to bedrock, which will be of immense use in foundation studies and in ground response analysis.

Finite Element Evaluation of Vertical Bearing Capacity Factors $$N_{c}^{\prime }$$ N c ′ , $$N_{q}^{\prime }$$ N q ′ and $$N_{\gamma }^{\prime }$$ N γ ′ for Ring Footings

Abstract: In this study, the vertical bearing capacity factors $$N_{c}^{\prime }$$ , $$N_{q}^{\prime }$$ and $$N_{\gamma }^{\prime }$$ are evaluated for smooth and rough base ring footings resting on c–ϕ soil using the finite element method. The radii ratio, (ri/ro), is the ratio of internal radius to the external radius of the ring footing, is varied from 0 to 0.75 with an increment of 0.25. The friction angle of the soil is varied from 5° to 35°, dilation angle is zero and the Mohr–Coulomb yield criterion and non-associative flow rule are used. The study is extended for the soil having a friction angle of 35° considering the non-associative flow rule with a dilation angle of 5°. The bearing capacity factors are evaluated considering cohesion, surcharge and unit weight as three separate components. Then the superposition of the three components of the bearing capacity equation is analysed. A numerical example is considered to illustrate the applicability of the finite element analysis by comparing the bearing capacities with those of the Terzaghi’s classical equation. The finite element results are presented in the form of design charts and tables for practical use.

Meshfree analysis of two‐dimensional contaminant transport through unsaturated porous media using EFGM

Abstract: The development of numerical methods for modelling contaminant transport in the subsurface is of major importance in view of the numerous applications in the contaminant hydrogeology and geoenvironmental engineering. Conventional mesh-based numerical methods have some difficulties when dealing with contaminant transport problems wherein high advective velocities, low dispersivities and/or high contrast in dispersivity are involved. The present study aims at contributing to the numerical study of two-dimensional contaminant transport thorough unsaturated porous media using meshfree technique, namely element-free Galerkin method (EFGM). In the EFGM, an approximate solution is constructed entirely in terms of a set of nodes and no characterization of the interrelationship of the nodes is needed. The EFGM employs moving least squares approximants to approximate the function and uses the Lagrange multiplier method for imposing the essential boundary conditions. van Genuchten model is used for describing the hydrodynamic properties of the unsaturated porous media. MATLAB code is developed to obtain the numerical solution. Three numerical examples are presented and the results are compared with those obtained from the finite element method. The EFGM has generated stable and convergent results for advection-dominated transport problems. Copyright © 2009 John Wiley & Sons, Ltd.

Multivariate Density Estimation

Abstract: Exploring and identifying structure is even more important for multivariate data than univariate data, given the difficulties in graphically presenting multivariate data and the comparative lack of parametric models to represent it. Unfortunately, such exploration is also inherently more difficult.

Engineering geology maps: landslides and geographical information systems

Abstract: IAEG Commission No. 1—Engineering Geological Maps—is developing a guide to hazard maps. Scientists from 17 countries have participated. This paper is one of a series that presents the results of that work. It provides a general review of GIS landslide mapping techniques and basic concepts of landslide mapping. Three groups of maps are considered: maps of spatial incidence of landslides, maps of spatial–temporal incidence and forecasting of landslides and maps of assessment of the consequences of landslides. With the current era of powerful microcomputers and widespread use of GIS packages, large numbers of papers on the subject are becoming available, frequently founded on different basic concepts. In order to achieve a better understanding and comparison, the concepts proposed by Varnes (Landslide hazard zonation: a review of principles and practice, 1984) and Fell (Some landslide risk zoning schemes in use in Eastern Australua and their application 1992; Landslide risk assessment and acceptable risk. Can Geotech J 31:261–272, 1994) are taken as references. It is hoped this will also add to the international usefulness of these maps as tools for landslide prevention and mitigation. Six hundred and sixty one papers and books related to the topic are included in the references, many of which are reviewed in the text.

How Nature works

Abstract: Why Big Fierce Animals are Rare: An Ecologist's Perspective. By Paul Colinvaux. Pp.236. (Princeton University Press: New Brunswick, New Jersey, 1978.) $9.50.