Abstract: The excavation of large underground caverns easily induces brittle cracking failure of high sidewall under high ground stress and other complex condition. Based on Mohr-Coulomb criterion and tensile strain criterion, a new composite tensile-shear yield criterion of high sidewall for large underground powerhouse was proposed. At first, according to the elastoplastic theory, associated and non-associated plastic flow rule were adopted independently for tension and shear yield. The calculation formula of this rule is deduced in detail in the finite difference method; and the dividing boundary of tensile and shear yield surface in stress space is determined. Then dynamic link library of the software is programmed adopting the C language; and the criterion can be used in the general software. Finally, taking the Lashiwa hydropower station located in the high geostress region for example, compared to FLAC3D own tensile-shear yield criterion, the results show that the tensile failure of high sidewall is obvious; and plastic zone and stress relaxation area is smaller by considering the tensile strain yield criterion; the proposed criterion can describe brittle cracking failure features of hard rock for high sidewall. Calculation of large hard rock underground caverns proves that the proposed criterion is reasonable.

Key words: rock mechanics, underground powerhouse, tensile strain criterion, numerical simulation