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

Guidelines on the response analysis of rocking shallow foundations considering material uncertainties under earthquake loading are not available in any great detail. In this study, a reliability analysis of a bridge pier with a rocking shallow foundation (RSF) was performed, using the Monte Carlo simulation technique, applied on the performance functions of the bridge pier, approximated using the response surface method. The soil–structure interaction was modeled using a beam on the nonlinear Winkler foundation approach. Two ground motions, corresponding to moderate and strong seismic intensities, were used in the study. Four model configurations of the bridge pier–RSF system were considered, and the probabilities of failure were evaluated, corresponding to three performance levels. It was concluded that the probabilities of failure changed drastically with the performance level of the bridge pier. The results showed that the bridge pier–RSF system suffered minimal damage during the moderate earthquake and was effective in enhancing seismic performance during the strong earthquake. 

Reliability Analysis of a Bridge Pier Supported on a Rocking Shallow Foundation under Earthquake Loading

Seismic base isolation is achieved via inserting flexible isolator element between the foundation and superstructure which lengthens the vibration period and increases the energy dissipation. Values adopted for uncertain parameters in earthquake engineering deviate from their nominal values. The stochastic response analysis of the base-isolated building is studied considering uncertainties in the characteristics of the earthquakes. Artificial acceleration time histories developed using probabilistic ground motion model are used in the study. The uncertainties in peak ground acceleration, frequency content, and time duration are considered to develop 5,000 artificial acceleration time histories. A bilinear model of the isolator described by its characteristic strength, post-yield stiffness, and yield displacement is used, and the stochastic response is calculated by using an ensemble of generated earthquakes. The study also presents the results of seismic reliability analysis of the five-storey base-isolated building. The first-order reliability method (FORM) and Monte Carlo simulation (MCS) method are used to evaluate the probability of failure associated with the top floor acceleration response of the building. The top floor acceleration response statistics are used in the performance function considering 0.3 g as a maximum allowable acceleration, and the probability of failure is evaluated. The probability of failure evaluated using the FORM is fairly in good agreement with the value obtained by the MCS.

Seismic Reliability Analysis of Base-Isolated Buildings

Hybrid earth retaining structure (HERS) is an efficient solution for earth retention problems that face spatial constraints. Deformation and stability analyses of the HERS have not been studied rigorously. The present study focuses on the development of predictive equations for the estimation of maximum lateral facing displacement and global factor of safety of the mechanically stabilized earth (MSE) over the soil nail (SN) hybrid retaining (MSE/SN) wall, a category of the HERS. Multiple linear regression is performed using the method of least squares to develop the predictive equations. The regression models for the MSE/SN wall are proposed using the data generated from the finite element model of the MSE wall of heights 6, 8 and 10 m. The adequacy of the predictive equations is verified by evaluating the summary of fit statistics. The failure surface of the MSE/SN wall consists of two parts: (i) a linear surface which propagates internally through the bottom nail of the SN wall starting at the toe of the MSE/SN wall and propagates externally through the remaining height of the SN wall, and (ii) continuation of the linear surface externally behind the reinforcement through the MSE wall. It is concluded that the predominant deformation modes are base sliding, rotation about the base and local bulging of the MSE wall. The failure surface always passes through the soil nails and therefore, it is recommended that the ultimate pullout capacity of the nails should be assessed during the design of the MSE/SN walls.

Deformation and Stability Analyses of Hybrid Earth Retaining Structures

The present work is intended to study the effect of variation of seismic area source zone on hazard value for Chennai, India In the conventional Cornell-McGuire approach to probabilistic seismic hazard analysis, the seismic activity rate for an area source is most often determined using the Gutenberg-Richter (G-R) recurrence law The seismic area is delineated using geology, geography and/or seismotectonic characteristics of the region However if the area lies in a distributed seismicity region, the delineation into different area zones introduces subjectivity The impact of the areal extent of seismic area zone on the final hazard value is studied using two approaches - the conventional Cornell-McGuire and zone-free approaches It is observed that in the conventional Cornell-McGuire approach, the peak ground acceleration decreases when the area source zone is increased while maintaining all other seismicity parameters same In the kernel method, the PGA remained unchanged though the seismic source area is increased This is due to the fact that in the kernel method, the seismic activity rate is a spatially varying parameter unlike the seismic activity rate determined from the G-R recurrence law, which assumes a homogeneous distribution of the activity rate for each of the area source zones The uniform hazard spectra are obtained for various return periods by both the approaches It is observed that in the Cornell-McGuire approach, the variation in the extent of seismic source area has little effect on longer return periods as compared to the smaller return periods

Impact Analysis of Seismic Source Area Extent on Hazard Estimate for Chennai City

Heaving of expansive soil is a crucial phenomenon due to their excessive volume changes with variation in moisture regime, which in turn leads to substantial distress to the structures built on them The main objective of this study is to evaluate the effectiveness of micropile and performance of geotextile to resists upward movement of structures built over expansive soil For this study, the expansive clay compacted in a steel box of size 50 cm × 50 cm × 50 cm to a depth of 20 cm and analyzed with two different methods to control heaving of soil Firstly, four micropiles of 16 and 20 mm in diameter were inserted into the soil with and without frictional resistance The micropiles were fastened to the corners of footing of size 15 cm × 15 cm × 05 cm, with nut and bolt system Further, Geotextiles were reinforced below the footing at a vertical spacing of 01B and 03B as single and double layers Then the soil was saturated with water and the upward movement of model footings (swelling) was monitored with time Test results showed that maximum heave reduction was 79% for 20 mm diameter micropiles with frictional resistance

G. R. Dodagoudar

Papers

Reliability Analysis of a Bridge Pier Supported on a Rocking Shallow Foundation under Earthquake Loading

Seismic Reliability Analysis of Base-Isolated Buildings

Deformation and Stability Analyses of Hybrid Earth Retaining Structures

Impact Analysis of Seismic Source Area Extent on Hazard Estimate for Chennai City

Experimental Study of Heave Control Technique for Expansive Soil Using Micropiles and Geotextile Layers