Stress-Hydraulic Pressure Coupling Experimental Investigation On Maokou Limestone

The Maokou limestone was made into standard specimens with size of Phi 50mmx100mm. MTS 815 was employed to conduct the experiments with different confining pressure and hydraulic pressure. The influence of confining pressure and hydraulic pressure difference to axial peak strength, cracks initiation strength, damage strength, elastic modulus and Poisson's ratio was analyzed. It is suggested that the axial peak strength, cracks initiation strength and damage strength increase with increasing of confining pressure. The axial peak strength, cracks initiation strength and damage strength decrease with increasing of hydraulic pressure difference. The hydraulic pressure difference minimizes the shear strength of specimens, while it has little influence to internal friction angle. The Young's modulus increases and Poisson's ratio decreases with increasing confining pressure. The Young's modulus decreases and Poisson's ratio increases with increasing the hydraulic pressure difference. When specimens are under uniaxial compression, the failure presents typical tensile failure. However, it shows shear failure when the specimens are under triaxial compression and hydraulic pressure. Moreover, under triaxial compression, the failure mode transforms from shear failure to tensile-shear failure with increasing confining pressure.