Abstract:

With the Permian limestone in Chongqing Wulong area as research object, the relations among yield strength, rock peak intensity, residual strength and confining pressure were studied through triaxial test. According to the plastic mechanics theory, the stress-strain curve under the 0-15MPa confining pressure of limestone can be divided into the following five phases: dense phase, elastic phase, yield phase, softening phase and flow plastic phase. Moreover, the mechanical model of each phase was proposed. In addition, yield phase and softening phase as two representative phases were discussed in depth. In yield phase, the nonlinear constitutive equation in yield phase was established with the principal strain as important parameter in association with Mises and Mohr-Coulomb yield rules. In softening phase, the constitutive equation in softening phase was deduced according to Mohr-Coulomb yield rules and plastic softening theory. Results of the constitutive equations were consistent with test results, which vindicated the accuracy and practicality of the models. These conclusions provide significant reference for similar slope stability researches.

Key words: rock mechanics, limestone, triaxial test,  stress-strain relation, mechanical model