中文摘要：

在岩石切削过程中,岩石的破坏形式对切削效率和切削参数的选择有重要的影响.本文为了研究岩石破坏形式的影响因素,利用颗粒流软件（PFC2D）建立了由颗粒簇组成岩石试样的数值仿真模型.通过大量的单轴压缩仿真实验和巴西仿真实验,确定了颗粒微观参数和岩石宏观参数之间的关系;研究了不同切削深度以及有无液柱压力情况下,岩石的破碎形式和过程.研究表明,当切削深度比较浅时,岩石主要为塑性破坏,表现为粉末状的颗粒在刀尖不断的堆积;当切削深度达到一定值后,岩石将会发生脆性破坏,表现为裂纹从刀尖开始沿着切削方向扩展,最终扩展至自由面而形成较大的切屑;颗粒簇法向强度比值影响着岩石切削过程中裂纹的扩展情况以及岩屑的形态;液柱压力对岩石的破坏形式也有很大的影响,随着液柱压力的增大,岩石破碎情况从平衡钻井时的切屑掉块变为过平衡钻井时的挤压破碎.

英文摘要：

It is well accepted that rock failure modes affect cutting efficiency, and knowledge of the failure transition is essential to the determination of optimum cutting parameters. In this paper, an attempt was made to research the factors influence the failure mode transition based on discrete element method （DEM）. For this purpose, the uniaxial compressive strength （UCS） and Brazilian tensile strength （BTS） tests are performed to calibrate the relations between micro-properties and macro-properties of the rock specimens which consist of the bonded clusters. The influences of cutting depth, hydrostatic pressure on failure mode transition in rock- cutting are researched by PFC2D. The results of the cutting simulation demonstrate that：The ductile failure occurring at shallow cutting depths, characterized by crushing of particles at the tip of the cutting tool and shearing of rock in front of cutting tool. The brittle failure occurring as the depth of cut increases beyond a threshold value, characterized by the development and propagation of macroscopic cracks ahead of the cutting tool. The ratio of intra-cluster normal bond strength to inter-cluster normal bond strength also has effect on the fracture evolution and chip morphology. Hydrostatic pressure could significantly influence the fracture evolution, inhibiting the formation of the long horizontal fracture. The cutting mechanism changes from a chip type mechanism under balanced drilling conditions, to a crushed type under overbalanced drilling conditions.