砂质泥岩各向异性特征试验研究

Experimental Study of Sandy Mudstone Anisotropic Properties

为研究砂质泥岩各向异性特征,取长轴与层面不同夹角的圆柱试样,在岩石试验机上做了三轴剪切试验,得到应力-应变曲线,分析了围压和夹角对砂质泥岩强度及破坏模式的影响。结果表明,砂质泥岩在相同围压下,峰值强度及残余强度的关系随夹角呈U型曲线,且其各向异性程度随着围压的增加而降低。根据莫尔-库伦强度准则,砂质泥岩的内摩擦角与粘聚力随夹角呈凹型曲线。其破坏模式表现出明显的各向异性,可分为三类,即张拉剪切复合破坏、沿层面剪切破坏和贯穿层面剪切破坏。其中90°为张拉剪切复合破坏,60°和45°为沿层面剪切破坏,30°和0°为贯穿层面剪切破坏。试验结果可为砂质泥岩地区相关工程稳定性分析提供参考。

In order to study anisotropy properties of sandy mudstone, conventional triaxial shear experiment was carried out for cylindrical specimen with different angles between long axis and bedding surface, based on rock testing machine; its stress-strain curves were obtained. The impact of confining pressure and bedding surface inclination angle on sandy mudstone strength and failure mode was analyzed. Results show that the relations among failure strength, residual strength and bedding surface inclination angle of sandy mudstone exhibit U-shape curves under the same confining pressure. The anisotropic degree decreases with the increase of confining pressure. Based on Mohr-Column criterion, the relations among sandy mudstone internal friction angle, cohesive strength and bedding surface inclination angle also exhibit U-shaped curves. Its failure mode exhibits obvious anisotropic characteristics. There are three categories of failure mode： tension-shear composite failure, sliding failure along bedding surface and shear failure penetrating bedding surface. When inclination angle is 90°, tension-shear composite failure occurs; When inclination angle are 60° and 45°, sliding failure along bedding surface occurs; When inclination angle are 30° and 0°, shear failure penetrating bedding surface occurs, respectively. Above results may provide reference for rock engineering stability in sandy mudstone areas.