应力Lode角对砂岩变形特性影响

 基于自主研发的“多功能真三轴流固耦合试验系统”，进行真三轴应力( )条件下，保持球应力、偏应力不变而改变应力Lode角试验，研究了球应力、偏应力不变条件下，应力Lode角旋转对岩石变形特性的影响。结果表明：3个主应变、体应变及偏应变均随应力Lode角的变化而改变；偏应力相等时， ， ， ， 及 随着偏应力比M(q/p)的增大而呈现递减趋势；球应力相等时，3个主应变、体应变及偏应变随着偏应力比M的增大呈现先减小后增大的趋势，且在M较大时失稳破坏。岩石破坏时形成多个近似垂直于 方向而平行于 ， 方向的破坏面，且强度值较常规加载明显偏小；偏应力比M对偏应变模量Gs有较大影响。球应力主要影响岩石的体积变化，且有一定的区间性；偏应力主要影响岩石的畸变，对岩石破坏起重要作用。试验砂岩的塑性变形受Lode角影响较大，塑形流动方向为 。  

Influence of stress Lode angle on deformation characteristics of sandstone

A series of experiments were carried out with the“multi-functional true triaxial experimental system modeling fluid-solid coupling”to investigate the effect of changing stress Lode angle on the deformation characteristics of sandstone under constant spherical stress and deviation stress( ). The results show that the principal，volumetric and deviatoric strains vary as the stress Lode angle changes. When the deviatoric stress is constant and the spherical stress is variable， ， ， ， and tend to decrease with the increasing of the M(q/p). When the spherical stress is kept constant and the deviatoric stress is variable，the principal，volumetric and deviatoric strains tend to decrease firstly and then to increase with the increasing of M，and the failure of sample occurs when the value of M is relatively large. Some failure planes are parallel approximately to and and perpendicular to . The strength value is significantly smaller than the ones under the conventional loading. The deviatoric stress ratio M has a great influence on the deviatoric strain modulus Gs. The spherical stress affects mainly the volume change of rock. The deviatoric stress affects mainly the rock distortion，and plays an important role in rock failure. The plastic deformation of the sandstone is mainly affected by the Lode angle and the flow direction is equal to .