Experimental Study on the Applicability of Failure Criteria for Rockfill in Three-Dimensional Stress Conditions

Using local materials to build rockfill dam favors the natural resources, but the strength characteristics of rockfill are quite different for each project, which makes it necessary to explore the applicability of failure criteria of rockfill. In this paper, four kinds of rockfill with different lithology are collected from different projects, using a large-scale true triaxial apparatus developed independently by the Changjiang River Scientific Research Institute, a series of true triaxial tests under different intermediate principal stress Ratio b [= (sigma (2)-sigma (3))/(sigma (1)-sigma (3))] are carried out. The results show that: Ratio b strongly affects the strength of rockfill, especially in the range of 0 < b < 0.25, compared with conventional triaxial tests, strength parameters show a significant increase; compared with several classical failure criteria, the Lade-Duncan failure criteria established by testing on fine sand show better applicability in describing the whole strength evolution process, due to particles breakage that will attenuate the strength of rockfill during big deformations, the Lade-Duncan failure criteria can be treated as the upper envelope for all four kinds of rockfill, the harder the samples' parent rock, the closer the strength to this upper envelope; SMP failure criteria show better applicability in the range of b < 0.25, so, when the effect of <sigma>(2) is not so significant, these criteria could be used to make an assistant determine for strength of rockfill; a plane strain test is also carried out, and when testing stress approaches peak value, Ratio b of all four kinds rockfill are within a narrow range of 0.16 to 0.20, in the case of limited test conditions, strength parameters of rockfill under three-dimensional stress conditions can be roughly estimated by plane strain test initially, and a simplified failure criteria is proposed.