TIME DEPENDENT DEFORMATION MODULUS OF ROCKS IN TUNNELS

Abstract

For safe and sound design of engineering structures in rock masses it is essential to have knowledge of the mechanical behaviour of rocks. Designs are carried out according to insitu properties and physical conditions of rocks. Yet unlike other materials, rocks generally present unforeseen problems and pose more challenges to the designer. In this study, uniaxial jacking test data (Mahrotra 1992), and data from U.P.I.R.I., Roorkee, has been collected for predicting modulus of elasticity (E6), rock mass modulus (E1) and modified Hoek and Brown's (1980) strength parameter (s). The field data of non-squeezing conditions has been collected from Goel (1994) to predict deformation modulus of rock mass (Ed). Closure-time data from Goel and Dube (1995), has been collected to predict time for ninety percent closure (T90) and to check time dependency of modulus of deformation. Using above parameters, model equations and dimensionless closure-time curve is derived. These correlations and model equations are useful to engineers involved in the designs, investigations and constructional activities of underground structures.