How to select rock mass parameters for analysis and design

摘要

Strength and modulus of rock mass suggested from RMR, Q and GSI have been examined with modulus ratio, Mrj, for their reliability. The design parameters adopted in some case studies based on these rock mass classifications are presented. The modulus ratios of rock masses are found to be much higher than those of intact rock, even with back analyses. Based on joint factor, Jf , compressive strength, modulus, cohesion and friction angle were estimated and applied in the analysis of a few cases. The predictions of deformations agreed well with the field measurements. Estimation of normal (Kn) and shear (Ks) stiffness of rock mass under various conditions of joint system is covered in some detail. When dilatancy component is separated in direct shear tests, the scale effect appears to be insignificant. Further, when to adopt equivalent continuum model for rock mass is suggested.