冻结层状红砂岩三轴蠕变特性及本构模型研究

Study of triaxial creep mechanical properties and constitutive model of frozen stratified red sandstone

为探讨冻结、三轴应力条件下层状红砂岩蠕变失稳规律,采用自主研发的DRTS-500型动力扰动低温岩石三轴试验系统对-10℃,围压为8MPa下不同节理面倾角的层状红砂岩进行三轴压缩试验和三轴蠕变试验,建立了冻结层状红砂岩三维蠕变模型.结果表明:冻结层状红砂岩轴向初始蠕变特性、非线性蠕变特性以及蠕变破坏形式受层理方向影响显著;所提出的新模型可以精确描述冻结层状红砂岩在三轴压缩条件下的轴向、径向蠕变全过程曲线,且该模型在描述初始蠕变阶段和非线性蠕变阶段时优于经典西原模型和改进西原模型.研究成果对西北地区层状岩层中立井冻结法施工时冻结岩壁支护时间、非线性变形预测以及井筒安全性评价具有一定的参考价值.

In order to investigate laws of creep instability of the stratified red sandstone under freezing and triaxial stress,triaxial compression tests and triaxial creep tests were conducted on stratified red sandstone samples under-10 ℃ and 8 MPa using the self-developed DRTS-500 dynamic disturbance subzero rock triaxial testing system.Three-dimensional creep models of frozen stratified red sandstone were established.The results show that axial initial creep properties,nonlinear creep properties,and creep compression failure forms of frozen stratified red sandstone are strongly related to bedding plane.The proposed new model can accurately describe the whole process of axial and radial creep curves of frozen stratified red sandstones which were under triaxial compression condition.Compared with the classical Nishihara model and improved Nishihara model,the new model is more superior in describing the initial phase and the nonlinear creep phase.The results are instructive to supporting time,nonlinear deformation prediction,and safety evaluation of frozen rock wall during shaft sinking by freezing method in stratified rock strata in Northwest China.