泥岩中软弱夹层的剪切力学特性研究

Study on shear mechanical properties of mudstone with weak intercalation

软弱夹层对斜坡及围岩稳定性影响较大,对其剪切力学特性及破坏模式的研究具有实际工程意义。以甘肃天水地区的泥岩及软弱夹层为研究对象,基于三轴不排水剪试验和数值模拟方法对不同倾角软弱夹层试样开展剪切力学特性研究,分析其应力–应变关系,探讨其剪切破坏特征。结果表明,试验、理论解与数值结果基本一致,试样剪切破坏均是在软弱层内部发生。随软弱层厚度和倾角的增加,倾角在0°~60°范围内,试样的剪切强度逐渐降低;缓倾角软弱层发生挤压鼓胀破坏,倾角大于15°时,沿软弱层发生剪切滑移;当软弱层较薄时,试样发生沿结构面的剪切,软弱层较厚时,发生软弱层内部挤压,或软弱层接触面剪切滑移。不一致的是软弱层倾角0°~15°,试验和理论解显示试样破坏切穿软弱层,而数值研究发现软弱层无明显剪切变形,在软弱层内部发生挤压鼓胀。

Weak intercalation has great influence on slope and surrounding rock stability. The study on shear mechanical properties and failure modes of weak intercalation has practical engineering significance. In this study,mudstone with weak intercalation in Tianshui,Gansu province was studied. Based on triaxial undrained shear test and numerical analysis,shear mechanical properties of remodeling weak intercalated layer samples with different dip angles were investigated. The stress-strain relationship of the weak intercalation was analyzed,and the shear failure characteristics were discussed. The results show that the experimental and theoretical analysis results are basically consistent with the numerical results and that the shear failure occurs inside the weak layer. With increasing the thickness and the dip angle of the weak layer,the shear strength of the sample decreases gradually in the range of 0°–60° of the dip angle. The weak layer with a low dip angle shows crushed and inflated failure while occurs shear slip along the weak layer as the dip angle is greater than 15°. When the weak layer is thin,the sample is sheared along the structural plane. While the weak layer is thick,extrusion occurs inside the weak layer,or shear slip occurs on the contact surface of the weak layer. What is inconsistent is that,when the dip angle of the weak layer is 0°–15°,the experimental and theoretical analysis results indicate that failure occurs by cutting through the weak layer,while the numerical study shows that there is no obvious shear failure in the weak layer and the failure reflects extrusion and swelling within the weak layer.