Effect of Excavation Stages on Clay Host Formation

Arab J Geosci DOI 10.1007/s12517-011-0382-8

ORIGINAL PAPER

Effect of excavation stages on stress and pore pressure changes for an underground nuclear repository

A. K. Verma & M. S. Saini & T. N. Singh & Avi Dutt & R. K. Bajpai

Received: 2 February 2011 / Accepted: 22 August 2011 # Saudi Society for Geosciences 2011

Abstract This paper provides a brief overview of evolution of deformations, stresses, and pore pressures due to different excavation stages during construction of an URL. Excavation of a rockmass develops damage zone of finite width around the excavated zone which is associated with changes in permeability and affect the fluid flow mechanism. In this study, a coupled hydromechanical (HM) analysis for a water saturated porous rock mass has been done which is caused by sequential excavation and backfill of vertical disposal pit of an URL. For this purpose, an Atomic Energy of Canada Limited’s in-floor concept for a deep geologic repository suitable for Indian condition has been used. Changes in rock deformations, stresses, strains and mechanically induced pore pressure in an undrained condition, during excavation, as well as those caused by mechanically induced rock deformations after backfill of the disposal pit have been modeled. A three-dimensional finite difference tool FLAC3D (Itasca Consulting Group Inc. FLAC-3D 1997) has been used for the analysis.

Keywords Hydro-mechanical . Underground geological repository . Flac3D . Coupled analysis . Pore pressure

Introduction Development of nuclear power in the 1950s was hailed as a major technological advancement providing an unlimited source of cheap power, without the shortcomings of finite hydrocarbon and hydroelectric resources (Witherspoon and Bodvarsson 2001). The disadvantages associated with highlevel waste (HLW) in the short-term are due to exposure of radiation and significant heat generation. Hence, there is a need to isolate it from the wider environment and to keep the wastes cool until...