SIMULATION OF FIELD TESTS FOR MODULUS OF DEFORMATION OF ROCK MASSES

Abstract

Modulus of deformation is an important parameter which defines the engineering behaviour of rock mass. It is generally determined by in-situ methods like Plate Loading Test, Plate Jacking Test etc. Due to difficulties encountered while conducting in-situ tests, modulus of deformation is often estimated by design engineers on basis of empirical correlations developed for the purpose on the basis of available field test data. For the interpretation of in-situ test data, the rock mass behaviour is assumed to be elastic which does not represent the actual behaviour of rock mass in nature. In the present work, simulation of plate jacking test has been carried out for chalk for which field data was readily available from the CBIP, (1988). The analysis considers the elasto-plastic response of the rock mass through Mohr-Coulomb yield criterion and the theory of plasticity. The analysis has been performed using the finite element method with the help of ABAQUS 6.7. The modulus of deformation of rock mass has been determined from load intensity versus strain response of rock mass corresponding to different parameters. It has been observed that modulus of deformation is greatly affected by engineering properties of rock mass. This analysis also provides an alternate method of choosing an appropriate empirical correlation for predicting the modulus of deformation of rock mass in situations where the field conditions are very difficult and do not permit conducting a plate jacking test in the field.