RESEARCH ON FORMATION MODE AND MECHANISM OF LAYERED ROCK SURFACE FRACTURES UNDER UNIAXIAL TENSION LOAD
BAO Chunyan1，TANG Chun?an1，TANG Shibin1，CAI Ming2，YU Qun1
(1. Center for Rock Instability and Seismicity Research，Dalian University of Technology，Dalian，Liaoning 116024，China；
2. Geomechanics Research Center，Laurentian University，Ontario P3E6B5，Canada)
Abstract：Fractures initiated from free surface of layered rocks，which are called surface cracks，often terminate at the interface which divides the fractured layer and the matrix layer，but can continue to propagate along the interface. A numerical simulation is carried out to study the mechanism of surface fracturing process including micro-fracture formation，propagation，coalescence，nucleation，fracture infilling，fracture saturation，termination，and interface delamination. A model with a fractured surface subjected to uniaxial tension is simulated firstly. It is found that the stress distribution between fractures depends on the fracture spacing；and the stress distribution will directly affect the fracture mode. New fractures can either appear in the surface layer(parallel to existing fractures)，or appear between the layers(interface peeling). Furthermore，an existing fracture can propagate to the underlying layer with no fracture inserting(fracture saturation). Secondly，material homogeneity is considered in the simulation；and the results show that the stress distributions in homogeneous and heterogeneous models are different. A smaller stress is required to produce the same fracture spacing in the heterogeneous model；and the critical values of the spacing to layer thickness ratio at fracture saturation are almost the same. Lastly，stresses in a few sections during fracture formation are analyzed；and it is found that stress transformation can be used to explain the mechanism of fracture saturation. A fitting curve of the relationship between strain and spacing to layer thickness ratio is obtained. It is found that fracture spacing in the case of interface delamination is greater than that without interface delamination. Stress transition between the two layers on fracture spacing in the fracture process is also investigated，with a focus on stress transfer mode.
包春燕1，唐春安1，唐世斌1，蔡 明2，于 群1. 单轴拉伸作用下层状岩石表面裂纹的形成模式及其机制研究[J]. 岩石力学与工程学报, 2013, 32(3): 474-482.
BAO Chunyan1，TANG Chun?an1，TANG Shibin1，CAI Ming2，YU Qun1. RESEARCH ON FORMATION MODE AND MECHANISM OF LAYERED ROCK SURFACE FRACTURES UNDER UNIAXIAL TENSION LOAD. , 2013, 32(3): 474-482.
2013, Vol. 32 
