弱化节理剪切力学特征的颗粒流模拟研究

在黏结颗粒模型中引入强度弱化因子生成弱化介质材料，进行弱化模型试件的单轴抗压强度试验。结果表明，弱化作用在降低试件单轴抗压强度的同时，还将导致试件弹性模量逐步下降。这一结果符合相关室内试验的研究成果。为进一步对岩石强度弱化模拟方法进行效果检验，利用颗粒流程序内置的FISH语言建立弱化岩石节理直剪试验模型，进行不同法向应力条件下弱化岩石节理的直剪试验。结果表明：弱化节理模型试件表现出类似于真实节理的一系列宏观剪切力学特征；不同壁面弱化程度条件下，节理模型试件的抗剪强度及剪切峰值膨胀角的试验结果与法向应力的依存关系均符合经典的JRC-JCS模型。由此表明，所采用的岩石强度弱化模拟方法可以较好地再现岩石介质的强度弱化效应。通过模型试件内微裂纹发展演化特征的研究表明，壁面弱化作用可导致试件内裂纹发育数目的快速增长、微裂纹分布范围的迅速扩大，以及剪切裂纹发育比例的迅速提高，由此从细观角度揭示了弱化节理面更易于产生宏观剪切破坏的原因。研究成果可以为弱化岩石节理的抗剪强度及大型岩质边坡的稳定性研究提供参考。

Particle flow modeling of shear character of weakened joint

First of all, weakened material is generated by introducing strength reduction factor(SRF) into bonded-particle model(BPM), hereafter, uniaxial compressive strength tests on weakened specimens are performed. The results indicate that: the weakening effect both reduces uniaxial compressive strength of the specimen and leads to a gradual decline in elastic modulus of the specimen, which is consistent with findings of related laboratory tests. In order to further examine the effects of the proposed weakening method, a numerical model for direct shear tests on weakened rock joint is developed by means of a computer program, which is written by a built-in language named FISH in particle flow code (PFC); and then direct shear tests are conducted at various normal stresses. Tests results indicate that: the shear character of weakened joints corresponds well to that of real rock joints, in addition to the dependencies of shear strength and peak dilatation angle on normal stresses are also conform well to the classical JRC-JCS model. It is suggested that the rock strength reduction method adopted in this study could preferably simulate the effect of strength reduction of rock material. Finally, investigation of evolution feature of microcracks within specimens shows that: attenuation of joint wall will lead to a rapid growth and development as well as rapid expansion of distribution range of microcracks, and will also result in a rapid increase in the proportion of shear cracks in specimens. As a result, the reason for a weakened joint is more susceptible to arise shear failure is revealed from mesoscopic angle. Research results in this article may provide a reference for the study of shear strength of rock joints，and for the study of stability of large-scale rock slopes.