地下隧道开挖中饱水围岩的力学特性研究

STUDY ON MECHANICAL PROPERTIES OF WATER-SATURATED SURROUNDING ROCK DURING UNDERGROUND TUNNEL EXCAVATION

为探究不同开挖方式对应的卸荷速率对饱水围岩的影响,对饱水砂岩开展了常规三轴压缩试验和轴向位移不变的卸围压(速率为0.1~5 MPa/s)试验。结果表明:在卸围压试验中环向变形是破坏的主要原因;随着卸围压速率的增加,破坏点的围压和轴向主应力增加且位于常规三轴压缩包络线外,环向能、总能和耗散能的变化量呈V形变化,试样的破坏模式由共轭剪切破坏转化为张应变+共轭剪切混合破坏,试样的剪胀角随着塑性剪切应变的增加先降低后增加。

In order to explore the influence of unloading rate corresponding to different excavation methods on saturated surrounding rock,conventional triaxial compression test and unloading confining pressure test with constant axial displacement(rate of 0.1~5 MPa/s)were carried out on saturated sandstone.The results show that the circumferential deformation is the main reason for the failure in the unloading confining pressure test.With the increase of unloading confining pressure rate,the confining pressure and axial principal stress of the failure point increase and are located outside the conventional triaxial compression envelope.The variation of circumferential energy,total energy and dissipation energy shows a V-shaped change.The failure mode of the specimen changes from conjugate shear failure to tensile strain+conjugate shear mixed failure.The dilatancy angle of the specimen decreases first and then increases with the increase of plastic shear strain.