循环荷载作用下岩石劈裂结构面剪切力学特性演化与影响因素研究

Shear mechanical characteristics evolution and influencing factors of rock discontinuities under cyclic loading

基于现有结构面剪切力学特性研究中对简单几何形态结构面研究多,天然形态结构面研究少,力学性质演化研究多,几何形态演化研究少的研究现状,通过巴西劈裂试验制备近天然形态岩石结构面,并采用模拟材料批量复制劈裂结构面试样的方法,开展循环荷载作用下岩石劈裂结构面的剪切力学特性演化规律与影响因素研究,分析法向应力、循环剪切次数、岩壁强度以及结构面粗糙度对循环剪切作用下岩体结构面力学特性和形貌特征的影响。最终通过在黏着摩擦理论-Barton经验公式中引入与循环剪切次数Nd有关的负指数假定劣化参数,提出了岩体结构面循环剪切强度公式。研究结果表明:法向应力、岩壁强度、结构面粗糙度越大,结构面的最大剪应力越大;法向应力、循环剪切次数、结构面粗糙度越大,岩壁强度越小,则归一化粗糙度参数越小。提出的循环剪切强度公式较好地验证了试验结果,可为工程安全设计提供理论参考。

Among the existing literature on shear mechanical properties of rock discontinuities, there are more researches on simple discontinuities than those on natural discontinuities, and more researches on mechanical properties evolution than those on geometric evolution. In this study, rock discontinuities in nearly natural forms are prepared through the Brazilian splitting test, and the splitting samples are produced with simulated materials. Then under cyclic loading, the shear property evolution laws and influencing factors of rock discontinuities are studied. The influences of normal stress, number of shear cycles, rock wall strength and roughness of rock discontinuity surface on mechanical properties and morphology of rock discontinuities under cyclic shearing are analyzed. Finally, by introducing the negative exponential deterioration parameter related to the number of shear cycles(Nd) into the adhesion theory of friction-Barton empirical formula, a formula for cyclic shear strength of rock discontinuities is proposed. The results show that with the increases of normal stress, rock wall strength and roughness of rock discontinuity surface, the maximum shear stress of rock discontinuities increases;with the increases of normal stress, number of shear cycles and roughness of rock discontinuity surface, the rock wall strength decreases and thus the normalized roughness parameters of rock discontinuities reduce. The proposed cyclic shear strength formula verifies the test results and provides a theoretical reference for engineering safety design.