Suresh R. Dash

Landscape Changes in the Andaman and Nicobar Islands (India) after the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami

Lifeline systems in the Andaman and Nicobar islands performed poorly during the December 2004 Great Sumatra earthquake and tsunami. Several power stations and transmission lines were damaged by the ground shaking, affecting the electric power supply to parts of the islands. Telecommunication services were severely affected because of destruction of several telephone exchanges. These services were restored quickly by government agencies. The dams and reservoirs, which supply potable water, sustained minor damage from ground shaking. However, segmented pipelines connecting the dams and reservoirs to various storage sites broke at several places, which significantly affected the water supply for a few days. Ground shaking damaged several elevated as well as ground-supported storage tanks. Damage related to tsunami waves was substantial in the 500–1,000-m strip immediately next to the coastline.

Response and Recovery in India after the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami

The rescue and relief work undertaken in the Andaman and Nicobar islands and in mainland India after the 26 December 2004 Indian Ocean tsunami was massive. A number of new initiatives undertaken by the government and nongovernmental agencies were innovative and successful. Also, since the tsunami was not a typical disaster for India, it raised a number of new concerns related to reconstruction along the coast.

Performance of Structures in the Andaman and Nicobar Islands (India) during the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami

The damage sustained by buildings and structures in the Andaman and Nicobar islands area was due to earthquake shaking and/or giant tsunami waves. While damage on Little Andaman Island and all the Nicobar Islands was predominantly tsunami-related, damage on islands north of Little Andaman Island was primarily due to earthquake shaking even though tsunami waves and high tides were also a concern. In general, the building stock consists of a large number of traditional and non-engineered structures. Many traditional structures are made of wood, and they performed well under the intensity-VII earthquake shaking sustained along the islands. However, a number of new reinforced concrete (RC) structures suffered severe damage or even collapse. Also, extensive damage occurred to the coastal and harbor structures in the Andaman and Nicobar islands.

The Effect of the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami on Transportation Systems in India's Andaman and Nicobar Islands

Boats and ships are the major modes of transportation among the Andaman and Nicobar group of islands. The Andaman Trunk Road also forms an important part of the transportation system in the Andaman Islands north of Port Blair. The harbor structures in the islands were the most affected during the ground shaking; the result heavily disrupted the lives of the island residents. These transportation systems are expected to be in working condition after a major disaster, to facilitate the search and rescue operations and the relief work in the affected areas. A reconnaissance team surveyed the damage that the 2004 earthquake and tsunami caused to the transportation structures in the islands. Damage was observed in all transportation systems, including harbors, highways, airports, and hangars.

Scaling Factor for Generating P-Y Curves for Liquefied Soil from Its Stress-Strain Behavior

The technique of constructing a p-y curve relies upon the similarity between load-deformation characteristics of pile with the stress-strain behavior of the interacting soil as observed in many recent experimental studies. From a dimensional analogy of pile-soil interaction with flow type strain field, the strain distribution in soil due to pile deflection (y) can be considered proportional to the y/D ratio, where D is the diameter of the pile. When the depth of the construction is deep, the pile-soil interaction can be considered as a plain strain model. To obtain the p-y curve from stress-strain curve, scaling factors such as Ms and Ns are normally used. Although these scaling factors are well calibrated and are being used in practice since long for standard soil, its applicability and values for liquefied soil is very limited. This paper provides a simplified methodology of developing these scaling factors suitable for liquefiable soils by using a numerical procedure with virtual work principle.

Probabilistic Analysis of Buried Pipeline Response Subjected to Fault Crossing

Deterministic analysis aims to demonstrate that a facility is tolerant to identified faults/hazards that are within the ‘design basis’, thereby defining the limits of safe operation. However, it cannot address the risk and uncertainty associated with it adequately, especially when the degree of uncertainty is high, like in seismic events. Deterministic analysis and design can provide an appropriate degree of safety to a set of loading parameters, whereas, a probabilistic analysis and design can provide a rational design based on acceptable risk and reliability of the system performance. In this paper, the major variables that greatly influence the performance of buried pipelines subjected to fault crossing has been identified and their coefficient of variance were selected. Monte-Carlo simulation has been implemented to find out the pipeline response in terms of maximum strain in the pipeline. Different cases were taken by keeping coefficient of variance (COV) constant while changing the subsequent parameters individually as well as combined. For various state of risk, the probabilistic distribution of pipeline strain has been obtained and finally a factor of safety (FOS) is calculated as the ratio of characteristic mean response and deterministic mean (response), for various probability of exceedance (acceptable risk).

Non-destructive strength and stiffness evaluation of cement-stabilised granular lateritic soils

Modulus of pavement materials is an important input parameter for the mechanistic design of pavements. As the bound layers such as cement-stabilised materials fail in flexure, flexural modulus (FM) is generally used as the modulus of stabilised material for the analysis of pavements. FM is determined from four-point bending tests under cyclic loading, but this process is a time-consuming exercise and therefore non-destructive method such as ultrasonic pulse velocity test (UPV test) may be employed for rapid determination of the modulus of elasticity of the material. In this study, ultrasonic pulse velocity of cement-stabilised granular lateritic soil (CLS) samples was determined using the UPV test and were correlated with the compressive strength, flexural strength and FM of 28-days cured stabilised specimens. It has been observed that the variation in pulse velocity determined from the UPV test shows good agreement with the variation of compressive strength and flexural strength of the stabilised lateritic granular soil samples considered in the study. Correlation was also established between the FM determined from the cyclic flexural test and constrained modulus determined from the UPV test on CLS beam samples.

Durability and shrinkage studies of cement stabilsed granular lateritic soils

ABSTRACT Cement stabilised materials are increasingly being used in pavement structural layers to solve the issue of scarcity of good quality stone aggregates and also to enhance the performance of the pavement. In addition to the strength and stiffness, the performance of pavements layers also largely depends upon the durability and shrinkage characteristics of stabilised materials used as base and subbase layers. The research reported in this paper focuses on the laboratory durability and shrinkage characteristics of cement stabilised granular lateritic soils (CLS). Wet–Dry (W–D) durability test and soaked UCS tests were conducted on CLS samples to evaluate the minimum dosage requirement of the binder. Preliminary studies were also done to assess the water absorption characteristics of CLS. Shrinkage properties of CLS were assessed through drying shrinkage tests. Effect of moisture content and cement content on ultimate drying shrinkage was also established in this study.

Strength and Stiffness Studies of Cement Stabilized Granular Lateritic Soil

A huge network of rural roads is being developed in India under the most ambitious Prime Minister’s rural connectivity programme, PMGSY (Pradhan Mantri Gramin Sadak Yojna). Under this programme, thousands of kilometers of rural roads are being constructed in the country, which require good quality pavement materials like crushed stone. The scarcity of natural aggregates has compelled to use marginal materials or locally available soils in structural layers of these pavements, which would reduced the cost of the project. Granular lateritic soils are widely available in many parts of India and presently, this is also used as sub-base material in different rural road projects, where it satisfies the code specifications. However, granular lateritic soils of some locations do not satisfy the strength and plasticity requirement of sub-base layer. But, they can probably be made suitable through stabilization. Though stabilization of soil by cement or lime is a well known process of improving the strength and stability of soil, the strength and stiffness parameters of stabilized lateritic soils in terms of modulus of rupture, resilient modulus, flexural modulus have very limited reference in literature. Therefore, in this study an attempt has been made to characterize the cement stabilized lateritic soils for use in sub-base and base layers in rural road pavements. A comprehensive laboratory testing programme has been conducted on cement stabilized granular lateritic soil samples collected from five different places of eastern India to study various strength parameters such as compressive strength, modulus of rupture and stiffness properties in terms of flexural modulus of cement stabilized granular lateritic soil. In this paper, strength and stiffness developments of cement stabilized granular lateritic soil in 7 days and 28 days have been studied and its suitability as a structural layer in rural roads has been investigated. Suitable modulus values of cement stabilized granular lateritic soils have been proposed which can be used as an input parameter for the input in mechanistic design of roads. Also relationships have been proposed to determine modulus of rupture and flexural modulus of cement stabilized granular lateritic soil from its compressive strengths.

PORE WATER PRESSURE GENERATION AND DISSIPATION NEAR TO PILE AND FAR-FIELD IN LIQUEFIABLE SOILS

The degree of liquefaction as characterised by the excess pore water pressure plays an important role in defining soil strength and stiffness. The pile-soil interaction in liquefiable soil, if modelled using BNWF model, the strength and stiffness of the soil springs can be suitably reduced by using a reduction factor. This reduction mainly depends on the soil type, its SPT/CPT value and the degree of liquefaction. Ideally this reduction should be based on the excess pore water pressure near the pile. However, it is difficult to estimate the degree of liquefaction near the pile. Hence, the lateral resistance of liquefied soil at soil-pile interface is normally characterized by the degree of liquefaction expected in the soil at the site without considering the influence of pile. Though, excess pore pressure near to the pile could be the governing parameter of soil resistance, it is hard to characterize the expected value of it in a field condition, as it depends on many parameters including soil type, shear loading, pile dimension, gap formation near to pile that facilitates easy dissipation of excess pore water pressure (EPWP), soil densification during pile driving, etc. Hence, to understand the difference between the far- field and near-pile response of liquefied soil, one high quality centrifuge test results are studied in this paper. The pattern of excess pore water pressure generation and development has been compared for both near-pile and far- field. The results are critically reviewed and discussed in this paper.