Correlation Between Field and Laboratory Deformability Moduli of Himalayan Sandstones

Abstract

The deformability properties of rock mass plays vital role in the design of civil engineering structures which are built in and on rock. Estimation of the deformability modulus through field tests is very expensive and challenging task. In general, for a massive or closely jointed rock mass, elastic modulus of rock material on small scale laboratory tests provides a preliminary assessment and judgement about modulus of deformation of rock mass (Em). In this study, an attempt was made to correlate modulus of deformation of rock mass with elastic modulus of intact rock at low stress levels (< 5 MPa). For this, field and laboratory investigations were carried out on massive sandstone located at Siwalik and Lesser Himalayan regions. For laboratory study, the sandstone samples were collected from the boreholes at the same location and identical depth and assessed elastic moduli at same stress levels, at which field tests on rock mass have been carried out. The study demonstrates the reliable estimation of Em from laboratory elastic modulus (E), for massive or less jointed rock mass, when assessed at low stress levels. Further, this paper also highlights the scale effect in the estimation of modulus of deformation.