Analysis of underground excavation in rocks

Abstract

This report aims to perform analytical and numerical analysis of underground excavation in rocks. Stresses induced in underground excavation may pose significant problem and might eventually lead to the instability and failure of the tunnel. Chapter 3 provides the induced stresses analysis for circular tunnel using Kirsch’s closed form solutions. Another deterministic approach by Duncan Fama is used to find out the radius of the yielded zone (plastic zone) and the tunnel wall displacements for a circular tunnel subject to internal pressure and far field stresses. The purpose is to find out the factors which affect the instability and displacements of the underground excavations. Both Kirsch and Duncan Fama’s closed form solutions are compared with Phase2 program separately to check for the closeness of the results obtained.Chapter 4 provides numerical analysis by employing the First Order Reliability Method (FORM) by Low & Tang 2004 and as well as Response Surface Method (RSM). Reliability analysis is used to account for the uncertainties of the input parameters. FORM is used to find the reliability index and the corresponding probability of failure for both normal and non-normal distributions. The results obtained from FORM and RSM are compared with those obtained from Monte Carlo Simulations using the software @RISK.