DISCUSSION ON ENERGY DISSIPATION MECHANISM IN SEEPAGE-CHEMICAL DAMAGE-SOFTENING PROCESS OF SOFT ROCK

Red bed soft rock has the characteristics of softening when it encounters water. The comprehensive effects of seepage, chemical and mechanical damage under rainfall conditions result in engineering geological hazards, which is one of the hot and difficult issues in geotechnical engineering field. Based on the principle of energy dissipation, the seepage, chemical and damage effects in the softening process of soft rock are studied. The main seepage, chemical and damage energy variables are extracted. The effect of seepage-chemical-damage on the softening process of soft rock and the mechanism of energy dissipation are discussed. The energy dissipation process is analyzed with triaxial test of soft rock. The results show that under the combined action of seepage-chemical-damage effect, water forms seepage in soft rock, which accelerates the softening process. The chemical interaction between soft rock and seepage accelerates the development of fracture-pore damage. The development of fracture-pore damage in soft rock in turn promotes the seepage and chemical action. From the energy point of view, the ultimate strain energy of soft rock can be reduced after softening. Seepage provides energy, but also consumes the energy of soft rock itself through chemical effect, which reduces strength and caused damage. Therefore, the softening process of soft rock is a process of energy dissipation. In this process, the fluctuation and dissipation of seepage, chemical and mechanical damage energy, material exchange and non-linear positive feedback make soft rock undergo phase transition from equilibrium to non-equilibrium, and finally soften and destroy intact soft rock to form dissipative structure.