COMPARATIVE STUDY ON TWO METHODS OF ROCK MASS STRENGTH PARAMETERS FOR APPLICATION IN HYDROPOWER ENGINEERING

Stress-induced failure of rock mass due to the conflicts between rock mass strength and relatively high in-situ stresses, has commonly occurred during the developments of hydropower projects in western China. Estimates of rock mass properties have thus become one of the important tasks in the engineering practice, which can have significant influence on decision-making for engineering problems. This paper examines the differences of considerations in two empirical methods of the Hydro-engineering approach and the Hoek-Brown method. It addresses the influences of three main factors on rock mass strengths. They include lithology, confinement level, and damage of intact rock. Then, it examines the applicability of the two empirical approaches to the condition where the three parameters soundly present. The findings suggest that (1) the influence of these three factors cannot be ignored on estimating rock mass properties; (2) the Hydro-engineering approach is applicable to low-stress conditions whereas less suitable in western area where stress appears relatively high; (3) the Hoek-Brown method is applicable to both circumstances, i.e., low stress condition typically in the areas of central and eastern China as well as complex geological conditions with high in-situ stresses represented with the area of western China.