基于摩擦角修正的异性岩石结构面抗剪强度准则

Peak Shear Strength Criterion for Discontinuities with Different Rock Types Based on Revisiting Frictional Angle

异性岩石结构面在三峡库区广泛发育,准确评估其峰值剪切强度对库区岩体稳定性评价至关重要.采用类岩石材料浇筑若干具有相同形貌、不同壁岩强度组合的异性结构面试块,在0.3~3.0 MPa常法向应力下开展直剪试验,并引入“壁岩强度组合系数λ”来表征岩石抗压强度和基本摩擦角对异性结构面峰值剪切强度的综合影响.结果表明,异性结构面的峰值剪切强度随λ的增加而呈非线性降低,降低程度主要受粗糙度控制,而与法向应力关系不明显.采用简单幂函数分析了峰值摩擦角与λ之间的关系,并在此基础上建立含三维形貌参数的异性岩石结构面抗剪强度经验准则.最后,利用在三峡库区采集的天然样品进一步验证了新准则对天然异性岩石结构面峰值剪切强度评估的可靠性.新准则可在一定程度上为三峡库区含异性结构面的岩体稳定性评价提供理论依据.

Discontinuities with different rock types are widely distributed in the Three Gorges reservoir area,and accurately evaluating the peak shear strengths of them is vital for rock mass stability analysis in this reservoir area.A batch of rock-like joint replicas with the same natural morphology but different joint wall strength combinations is prepared,and direct shear tests are conducted on them under constant normal stresses ranging from O.3 to 3.0 MPa.Further,the joint wall strength combination coefficient(a)is introduced to capture the combined effect of rock compressive strength and basic angle on the peak shear strength of discontinuities with different rock types.Testing results illustrate that the peak shear strengths of discontinuities with different rock types decrease non-linearly with increasing,and the decrease degree is mainly controlled by roughness while showing no obvious relationship with normal stress.A simple power law function is selected to analyze the correlation between the peak friction angles and a,and an empirical strength criterion with the inclusion of three-dimensional morphology parameters is developed to predict the peak shear strengths of discontinuities with different rock types.Finally,natural samples collected from the Three Gorges reservoir area are used to further validate the reliability of the new criterion for evaluating the peak shear strength of natural discontinuities with different rock types.To some extent,the new criterion can provide a theoretical basis for the stability evaluation of rock masses containing discontinuities with different rock types in the Three Gorges reservoir area.