关键词: 深部砂岩；真三轴试验；变形特征；应力分界点；Mogi-Coulomb准则

Abstract: A series of true triaxial compression tests on sandstone were carried out based on the true triaxial testing machine. The sandstone samples were taken from a gas storage facility， with a buried depth of 3600 meters. The strength and deformation characteristics of deep sandstone under true triaxial stress were studied， and the elastic modulus， cohesion， friction angle and peak failure strength of deep sandstone and shallow sandstone were compared. The results show that with the increase of the intermediate principal stress， the peak strength of the deep sandstone will also increase， the crack initiation stress and the damage stress of the deep sandstone will also increase， and the intermediate principal strain at the peak will decrease. With the increase of sandstone depth， the elastic modulus， cohesion and friction angle of sandstone all show an increasing trend. The octahedral shear stress of the peak failure strength of the shallow rock and the effective mean normal stress show a nonlinear relationship， while the octahedral shear stress of the peak failure strength of the deep rock has a linear relationship with the effective mean normal stress. And the Mogi-Coulomb criterion is more suitable for reflecting the strength characteristics of deep sandstone at failure.

Key words: deep sandstone; true triaxial test; deformation characteristics; stress breakpoint; Mogi-Coulomb criterion