侧向受拉脆性岩石压缩本构及蠕变失效研究

Research into the compressive constitutive and creep failure properties of brittle rocks under the lateral tension

轴向压缩作用下,脆性岩石侧向应力严重影响岩石力学特性。侧向压应力影响下的轴向压缩岩石力学行为已经得到广泛研究,然而侧向拉应力对轴向压缩岩石力学行为影响研究很少。本文基于脆性岩石翼型裂纹扩展模型中,初始裂纹面法向应力与剪切应力的正负方向为判断依据,研究了侧向拉应力对轴向压缩力学行为的影响。发现恒定的侧向拉应力作用下,轴向压缩应力渐进变化过程中,脆性岩石内部细观初始裂纹面的法向应力只能为压缩应力,不存在拉应力情况。分析了从侧向压应力到拉应力转化过程中,脆性岩石轴向压应力与细观裂纹扩展长度关系、轴向压应力与轴向应变关系、岩石峰值强度、裂纹启裂应力及初始弹性模量的变化规律。并分析了侧向拉应力对岩石蠕变裂纹长度、裂纹速率、轴向应变及应变率演化曲线,以及对蠕变失效时间及稳态蠕变应变率的影响。讨论了侧向拉压应力突变转化以及侧向拉应力分级增大对轴向压缩岩石蠕变演化行为影响。该研究为深部地下工程围岩稳定性评价提供了一定理论依据。

The lateral stress strongly influences the mechanical properties of brittle rock under axial compressive loadings,which was widely studied.However,the lateral tensile stress effect on the mechanical properties under axial compression is rarely studied.Based on the conditions of the positive and negative directions of the normal and shear stresses acting on the initial crack surface in the wing crack growth model,the effect of the lateral tensile stress on the axial compressive mechanical behaviors is studied.The normal stress is only the compressive stress and could not be the tensile stress on the initial crack surface in brittle rock under constant lateral tensile stress and the axial progressive compressive stress.The relation between axial stress and wing crack length,the axial stress-strain relation,the peak strength,the crack initiation stress,and the initial elastic modulus are analyzed during the transformation from the lateral compression to the lateral tension.The effects of the lateral stress on the evolutions of the wing crack length,crack velocity,axial strain and strain rate,the creep failure time,and the stationary strain rate during creep are also analyzed.The compressive creep behaviors of rock influenced by stress paths of the sudden change between the lateral tension and compression,and the lateral stepping tension are discussed.The results provide a theoretical help for the stability of surrounding rock in deep underground engineering.