Experimental study on mechanics and permeability characteristics of Jurassic red sandstone under hydro-mechanical coupling

Abstract

Jurassic red sandstone is widely distributed in the Three Gorges reservoir area. During the operation of the red sandstone reservoir, the hydro-mechanical coupling characteristics affect the stability of most landslides and rock slopes. In this paper, triaxial compression tests under different confining pressures and osmotic pressures are carried out on the Jurassic red sandstone in the Three Gorges Reservoir area by means of the multi-field coupled triaxial test system. The mechanical properties and permeability evolution characteristics of the red sandstone under triaxial compression are systematically studied. The results show that: ①The pre-peak stress-strain curve of red sandstone can be divided into pore compaction stage, elastic deformation stage, stable development stage of micro-cracks, and unsteady development stage. The mechanical parameters of red sandstone are negatively correlated with osmotic pressure and positively correlated with confining pressure. ②With the increasing of confining pressure, the failure mode of red sandstone transitions from tensile failure to shear failure.③The permeability under different osmotic pressures shows a "three-stage" evolution law of developing steadily firstly, then increasing slowly and increasing sharply lastly; the permeability under different confining pressures decreases firstly and then increases. ④The effects of osmotic pressure and confining pressure on rock are analyzed from the perspective of energy, and the degradation effect of seepage inrock and the inhibition effect of confining pressure on crack development are verified. The experimental results have guiding significance for the stability of bank slope.In this experiment, the strength, deformation and permeability characteristics of the little-reported Jurassic red sandstone were systematically studied, which is of complementary significance to the topic of seepage-stress coupling. The working conditions are determined according to the stress level of the rock mass on the slope of the Three Gorges reservoir area, and the test results have guiding significance for analyzing the stability of the slope in the reservoir area.

Keywords

• hydro-mechanical coupling
• jurassic red sandstone
• triaxial compression
• permeability characteristics
• energy dissipation