Practical determination of mechanical design parameters of intact rock considering scale effect

As a rule, the change in mechanical properties of rock by specimen size is regarded as scale effect. A rock mass basically consists of two components: intact rock and discontinuities, each of which has different scale effects. In order to numerically analyze the behavior of discontinuous rock masses, sufficient mechanical properties must be determined not only for discontinuities but also for intact rock taking into consideration the different scale effects. This paper reviews the scale effect on strength and deformation characteristics of intact rock, and also discusses the possibility of using standard specimens to estimate strength and deformation characteristics of actual-scale rock. Finally, we propose an adequate method for the practical determination of mechanical design parameters based on the above discussions.