応用水文 = Applied hydrology

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.

Multivariate Density Estimation

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.

Engineering geology maps: landslides and geographical information systems

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.

How Nature works

Experimental characterization of shrinkage and desiccation cracking in thin clay layer

The most important parameter in the kernel density estimator is the bandwidth or spread or window width. The bandwidth of the kernel density estimator, which follows the power law, is determined using the nearest neighborhood technique for the earthquake catalog which is divided into bins. For reliable hazard estimates, the magnitude bins used in developing the power law and estimating the spatial activity rate density function should be the same. It is important that consistency be maintained between the earthquake epicenters used in determining the bandwidth and the epicenters to which the bandwidth is applied subsequently. In this paper, the effect of epicenter data inconsistency on hazard estimates for various return periods for Chennai is evaluated. Two methods of binning are used, one in which the epicenters used in deriving the bandwidth is in line with the epicenters used in arriving at the spatial activity rate and the other where the epicenters used in deriving the bandwidth are just grouped by dividing the catalogue into equal bins. Seismic hazard estimations are compared using these two approaches of forming the magnitude bins for Chennai, Tamil Nadu, India. The peak ground acceleration (PGA) values obtained from Binning Methods 1 and 2 for 475 years return period are 0.0955g and 0.0802g respectively. The difference in PGA and peak spectral acceleration (PSA) from the two binning methods ranges from 20 to 10% with respect to Binning Method 1 for the return periods of 72 to 2475 years.

Effect of Epicenter Data Inconsistency in Determining Bandwidth and its Subsequent Use in Hazard Analysis for Chennai Using Kernel Smoothing Approach

In this paper, the seismic response analysis of deeply embedded ventilation stack is addressed by considering the effects of soil–foundation–structure interaction (SFSI). Seismic SFSI analysis of the stack subjected to a site-specific design ground motion is carried out using finite element method. A parametric sensitivity analysis is made to investigate the effect of embedment and shear wave velocity ratio of the subsurface profile on the seismic response of the stack. The first series of the SFSI analysis is carried out for the stack with surface footing using computer program SASSI 2000. The second set of analysis incorporates the effect of embedment on the seismic response of the stack. The flexible volume substructure method is used to analyze the seismic SFSI effects. It has been found that the seismic response at the various levels of the stack shows a strong dependence on stiffness of the subsurface profile and the depth of embedment. The spectral acceleration and relative displacement at the top ...

Seismic soil–foundation–structure interaction analysis of deeply embedded ventilation stack

Mechanically stabilized earth (MSE) retaining walls are the most suitable design alternatives to the conventional retaining walls due to their simple, rapid, and cost-effective construction, reduced right-of-way acquisition, etc.; hence, the MSE walls are used in many central, state, and private sector projects. But the design and analysis is a challenging task for geotechnical engineers. This paper deals with the study of stability and wall movement of a existing MSE wall constructed on a major state highway in central Texas, using a finite element (FE) analysis and limit equilibrium (LE) slope stability analysis program GEO5 2016. The detailed analyses for both internal and external stabilities were obtained from the finite element and limit equilibrium analysis, with a critical failure surfaces and the wall movement of a MSE wall. The factors of safety obtained from both analyses were compared. The study shows that the factors of safety obtained from finite element and the limit equilibrium analysis, for a given problem, match in an acceptable range with a different critical failure surfaces. Also, this paper deals with the effect of backfill soil and reinforcements on stability and excessive movements of MSE wall.

Numerical Analysis of MSE Wall Using Finite Element and Limit Equilibrium Methods

Mapping surficial and subsurface conditions play an important role in analysis and design of geotechnical structures and facilities. Spatial distribution of depth to soil-bedrock interface has a prime significance in developing input ground motion at the surface and estimating damage potential of an earthquake. This paper deals with the evaluation of spatial variability of soil-bedrock interface in Chennai, south India using Multichannel Analysis of Surface Wave (MASW) test and Standard Penetration Test (SPT) data. The MASW tests have been carried out at selected locations in Chennai city using 24 channel Geode and shear-wave velocity profiles are developed. Based on the MASW test results, a shear wave velocity (Vs) of around 300 m/s is obtained for weathered/soft rock, and a value of 700 m/s for hard rock in the present study. Depths corresponding to these velocity ranges are identified to estimate the position of soil-bedrock interface in the study area consisting of IIT Madras campus and its surrounding area. In addition, nearly 85 borelogs have been used to identify the main soil types and variation in depths to bedrock in the study area. A comprehensive geo-database containing all subsoil information has been designed to create three-dimensional borelog information and depth to bedrock interface. The spatial variability of depth to soil-bedrock interface at the locations where field measurements are not available has been mapped using spatial interpolation technique called kriging. The developed bedrock map indicates that the depth to soil-rock interface varies from 2 to 18 m in the study area. The evaluated depths to soil-bedrock interfaces have been compared and validated with the subsurface profile information obtained from a few selected borehole data and MASW test results. Further, the available SPT data can effectively be utilized for developing shear wave velocity distribution maps at different depths along the soil profile using the correlation between Vs and SPT-N values for different categories of soils of the study area. These maps will be of immense use for ground response studies and development of microzonation maps.

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Spatial Variability of Soil-Rock Interface in Chennai using Geophysical and Geotechnical data

This paper presents an alternative numerical method to model the two- dimensional contaminant transport through saturated porous media using a meshless method called Element Free Galerkin Method (EFGM). In EFGM, an approximate solution is constructed entirely in terms of a set of nodes and no elements or characterization of the interrelationship of the nodes is needed to construct the discrete equations. For analysis, the two-dimensional advection-dispersion equation with sorption is considered. The unknown concentration values are approximated by using moving least square approximants, which are constructed using a weight function, a linear basis function and a set of non-constant coefficients. A weak form of the governing equation is formulated and Lagrange multiplier method is used for enforcing the essential boundary conditions. MATLAB code is developed to obtain the numerical solution. Two numerical examples are presented to illustrate the applicability of the proposed method and the results are compared with those obtained from the finite element method.

G. R. Dodagoudar

Papers

Effect of Epicenter Data Inconsistency in Determining Bandwidth and its Subsequent Use in Hazard Analysis for Chennai Using Kernel Smoothing Approach

Seismic soil–foundation–structure interaction analysis of deeply embedded ventilation stack

Numerical Analysis of MSE Wall Using Finite Element and Limit Equilibrium Methods

Spatial Variability of Soil-Rock Interface in Chennai using Geophysical and Geotechnical data

Two-dimensional Contaminant Transport Modelling Using Meshless Method