1. Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mine,University of Science and Technology Beijing,Beijing　 100083,Chi- na; 2. State Key Laboratory of Safety Technology of Metal Mines,Changsha Institute of Mining Research Co. ,Ltd,Changsha　 410012,China; 3. Beijing Key Laboratory of Urban Underground Space Engineering,USTB,University of Science and Technology Beijing,Beijing　 100083,China

天然岩体中存在多组随机结构面,同时结构面几何上存在粗糙特性,基于这两种特性,建立了一种粗糙离散节理网络(Rough Discrete Fractures Network)RDFN模型,并基于颗粒流PFC2D开展了RDFN模型直剪条件下力学特性研究,与直线型DFN模型进行了对比。结果表明:节理几何粗糙特性对裂隙岩体的抗剪特性影响显著。相同加载条件下,考虑粗糙性后RDFN模型的抗剪强度、剪切模量均较DFN模型显著增高;DFN模型中微裂纹沿节理方向贯通,局部存在少量的基岩破坏,RDFN模型破坏模式相对复杂,沿剪切方向基岩单元破坏显著;随着样本尺寸的增大,节理模型的抗剪强度、剪切模量总体上均呈现降低趋势;尺寸效应分析结果表明抗剪指标均在尺寸达到4.0 m后趋于稳定。

Multiple discontinuities exist in the natural rock mass and these discontinuities are geometrically rough. In this paper,a rough discrete fractures network model (RDFN) considering the complex and rough geometry distribution of discontinuities is introduced and tested under direct shear test using PFC2D. The corresponding shear behaviors, such as shear strength,shear modulus and failure pattern,were studied and compared with the traditional linear dis- crete fractures network ( DFN) model. Numerical results show that fracture surface roughness can significantly affect the shear behavior of rock masses. The peak strength and shear modulus of the RDFN model are ralatively higher than those of the DFN model. The principal shear fractures in the DFN model mainly coincided along the linear joints. Parts of the intact rock elements were fractured. The failure pattern of RDFN model is much more complex and more intact rock elements were fractured after peak shear strength. The peak shear strength and modulus of all jointed rock models decrease with the increase of sample sizes. The value of shear modulus of the RDFN model is higher than that of the DFN model. The values of shear strength tend to be stabilized with the scale size reaching 4. 0 m according to the scale effect analysis.

WANG Peitao,REN Fenhua,CAI Meifeng. Mechanical analysis and size effect of rough discrete fractures network model under direct shear tests based on particle flow code[J]. Journal of China Coal Society,2018,43(4):976-983.