中文摘要：

该文引入Rankine最大拉应力准则和Mohr—coulomb剪切破坏准则分别作为岩石基质的拉伸和压剪破裂判据，分析了单轴压缩下裂隙岩体的起裂机制。根据含单个椭圆裂隙的无限域岩体在单轴压缩下的应力理论解，编制了Matlab程序，计算分析了不同短轴与长轴比k和倾角。[（加载轴与裂隙长轴间的夹角）下的岩石基质应力集中系数、两种不同起裂机制的破裂函数值、开裂位置和开裂临界荷载。对多裂隙岩体，采用ABAQUS有限元软件进行了应力计算和起裂机制分析。计算结果表明：1）与单裂隙岩体相比，多裂隙岩体的岩石基质应力集中系数略大、起裂临界荷载略小，但起裂位置相同；2）随着裂隙倾角a的增大，岩石基质的主拉应力集中区由裂隙端部附近很小的区域逐渐变为裂隙中部的大面积区域，而主压应力集中区则反之；3）存在临界裂隙倾角a0，其值在45°附近。当裂隙倾角0〈口≤咖时，在裂隙端部同时有拉应力和压剪应力集中，拉破裂临界荷载小于压剪破裂临界荷载，但随着裂隙轴比的增大二者逐渐相等，表明岩体受拉破裂和压剪破裂共同影响越来越明显；当a0〈6（≤90°时，尽管拉破裂临界荷载大于压剪破裂临界荷载，但首先发生在裂隙端部的压剪破裂区范围很小，而随后将在裂隙中部或端部发生大量的拉伸破裂。上述分析结果与实验现象较为吻合。

英文摘要：

In this paper, with two cracking criteria, i.e., Rankine＇s maximum tensile stress theory and Mohr-Coulomb shear failure theory for tensile and shear crack initiation respectively, the cracking mechanism of fractured rock masses under uniaxial compression was analyzed. Based on the analytical solution to stress field of single inclined elliptic fracture in an infinite rock mass under far-field load, the factors of the principal stresses concentration surrounding the fracture and the cracking functions, cracking positions and the crack initiation loads of the two cracking mechanism were calculated for different ratio of the smaller to the larger semi-axis k of the elliptical fracture and fracture dip angle （the angle from the larger semi-axis of elliptic fracture to direction of the load） through a Matlab program. For rock masses containing multiple elliptic fractures, elastic stress fields were calculated by ABAQUS and cracking mechanisms were analyzed. It is concluded that： l） With the increaseof the number of fractures, the factors of the principal stresses concentration in the rock matrix increase slightly and the crack initiation loads decrease slightly, while the cracking positions are the same. 2） With the increase of fracture dip angle, the tensile stress concentration of the rock matrix changes from a small zone around fracture tip to a large zone surrounding the fracture, and vice versa for compressive stress, 3） There exists an critical fracture dip angle a0 which is around 45°; When 0〈a≤a0, i.e., the fracture dip angle is small, the tensile stress and shear stress are both concentrated in the vicinity of fracture tip and the tensile crack initiation load are close to the shear crack initiation load with the increase of the ratio of the smaller to the larger semi-axis k, which means that tensile cracks and shear cracks will appear simultaneously; While for a0〈a≤90°, i.e., the fracture dip angle is large, shear cracks or crushing zones will firstly initiate at the small region of