Experimental study on the mechanical behavior and mesoscopic damage of Guiyang red clay during triaxial loading

Abstract

Red clay is a kind of regional residual clay formed through the physical and chemical weathering of carbonate rocks in a warm environment and under damp climate conditions. These clays have special physical and mechanical properties including a large void ratio, low compressibility, and good mechanical engineering properties. The exhausted saturation test, consolidated undrained shear test, and nuclear magnetic resonance test of red clay samples were conducted to reveal the evolution law of the pore structure and the effect of meso-damage on the mechanical behavior of Guiyang laterite during triaxial loading. The results show that the nuclear magnetic resonance T2 spectrum of Guiyang red clay under conventional triaxial loading mainly shows three peaks, and each single peak corresponds to a pore type. With the gradual application of load, the number of micro pores in red clay increases, and the radius decreases gradually at the meso level. The number of medium-large pores decreases, and the pore radius increases gradually. At the macro-level, the shear surface of red clay begins to form slowly and gradually develops to the stage of slip and compaction. The strength of the particles on the shear surface is gradually lost, and the deformation of soil becomes larger and larger. In addition, during the initial stage of shear, the shear strength of soil is mainly provided by its cohesive strength. With the gradual progress of shear, the cohesion will decrease, and the friction angle will increase, at which time the shear strengths will consist of cohesive strength and friction strength, respectively.