ANALYSIS OF TUNNELS IN ELASTO-PLASTIC AND VISCO-ELASTIC MEDIA

Abstract

observational and empirical, available for analysis of tunnels, The empirical approaches are based on rock mass classification systems. Observational approach basically represnets a 'built as you go' philosophy, and the analytical solutions are mostly based on some simplifying assumptions about the behaviour of surrounding medium. In most of the analyses, surrounding medium is assumed to be elastic or elasto-plastic and the effects of time dependent mechanical properties of medium are generally ignored. It has been known for some time that pressure on lining increases with lapse of time. Therefore, effect of time dependent mechanical properties shall be taken into consideration. In this study, analysis of a head race tunnel under project Maneri-Bhali stage II has been considered using both plastic and viscous properties of the medium. A Fortran program has been developed on the basis of Sakurai (1970) analysis for 'Analysis of Tunnels in Elasto-elastic and Visco-Elastic Media'. Using the above Fortran program, a parameteric study has also been carried out to investigate effect of parameters like (3*/G, installation time of lining etc. on the pressure acting on tunnel lining.