Estimation of Modulus of Deformation by Different Methods for an Underground Cavern—A Case Study

In the design of underground excavations for mining and civil engineering activities, it is essential to analyse the stability of excavations through numerical modelling. For the design of any underground structures, the value of modulus of deformation of rock mass plays a vital role. The modulus of deformation value may be estimated based on different empirical relations available in the literature. A lot of empirical relations were available in the literature proposed by different authors for estimating the modulus of deformation based on the rock mass characteristics and intact rock properties. It can be measured in situ by carrying out in situ testing like Uniaxial jacking test, Plate loading test, and Goodman jack test. Carrying out the in situ tests for the determination of the value of modulus of deformation is difficult, expensive and time-consuming. The in situ value of modulus of deformation determined by carrying out each of these test methods will yield different values as the testing technique involved differs from each other. The value can also be estimated by applying back analysis from numerical modelling based on the observed displacements in the field. In this paper, the variations in the value of modulus of deformation estimated by available empirical relations, in situ test method and back-calculated from the numerical analysis have been studied for an underground cavern. From this study, it can be observed that the in situ value of modulus of deformation is also higher when compared with that of the back calculated value from numerical modelling for this case study.