不同卸荷路径下的页岩蠕变特性试验研究

Experimental Study on Creep Characteristics of Shale under Different Unloading Paths

地下硐室围岩流变现象显著,对硐室开挖与运营造成巨大威胁。以某深埋矿井巷道页岩为例,参照地下硐室实际开挖情况设计轴压与围压等比卸荷应力路径,同时开展恒轴压卸围压、等比卸荷两种应力路径下的蠕变试验,研究页岩在不同卸荷路径下的蠕变力学特性。试验结果显示:①页岩在两种卸荷路径下的蠕变特性十分明显,轴向应变量值始终高于侧向应变;②岩石在破坏应力水平下的轴向应变增长程度小于侧向应变,岩石的侧向扩容较为明显;③等比卸荷和恒轴压卸围压条件下的岩石长期强度分别为47.69 MPa和62.85 MPa,等比卸荷应力条件下岩石更易屈服破坏。研究成果可为地下硐室长期稳定性研究提供一定参考。

The rheological phenomenon of surrounding rock of underground chamber is remarkable,which poses a great threat to the excavation and operation of underground chamber.Taking a deep mine roadway shale as an example,the stress path with equal ratio of axial pressure and confining pressure unloading was designed according to the actual excavation of underground chamber.Creep tests under two stress paths of constant axial pressure unloading confining pressure and equal ratio unloading were carried out at the same time to study the creep mechanical properties of shale under different unloading paths.The results show these as follows.Firstly,the creep behavior of shale under two unloading paths is very obvious,and the axial strain is always higher than the lateral strain.Secondly,the axial strain increases less than the lateral strain under the failure stress level,and the lateral dilatancy of the rock is obvious.Thirdly,the long-term strength of rock under the condition of constant axial pressure unloading and constant axial pressure unloading confining pressure is 47.69 MPa and 62.85 MPa,respectively,and the rock under the condition of constant axial pressure unloading is more likely to yield failure.The research results provide some reference for the long-term stability study of underground chamber.