Rate-dependent deformability and strength characteristics of rocks

Deformability and strength characteristics of rocks depend upon the stress rate or strain rate used in testing. This fact has implications for long-term behaviour of structures in rocks and is very important from the engineering point of view, say for underground cavern design, opening stability analysis, and prognosis of openings deformation in prolonged periods of time. In this study, the rate-dependent deformability and strength characteristics of rocks are focused on. First, some experimental results on rate-dependent characteristics of different rocks are presented, and then a data-base system developed for rate dependent characteristics of rocks is briefly described. The experimental results together with those from the data base system are used to see the variation of Young's modulus and Poisson's ratio as a function of strain rate. The variation of uniaxial peak compressive strength and corresponding peak strain dependency on strain rate are also studied from experimental results and the data base. Finally, some guidelines for formulating a visco-elasto-plastic constitutive law for modelling rate-dependent characteristics of rocks are briefly described.