Abstract: A large number of tensile cracks are developed in the rock mass of anticline core. Scientific interpretation of this special and common geological phenomenon is conducive to the evaluation, utilization and deepening the understanding of the evolutionary mechanism of geological hazards in this area. The geological model of intermittent cracked rock mass located in the tensile stress zone of the anticline core was generalized into a periodic crack model, and the central crack mechanics model was further obtained, and the optimized linear field analysis method was introduced for research. The results show that: the higher the crack coalescence rate, the greater the increase effect of shape modified coefficient on the stress intensity factor at the crack tip. The stress modified value has the characteristics of nonlinear monotonic increase with respect to the crack coalescence rate and linear monotonic increase with respect to the external load. Taking limestone rock mass as an example, the tensile strength of rock mass obtained by various theoretical calculations shows that the obtained solution is reasonable. When the crack half-length is constant, the tensile strength of rock mass decreases with the increase of crack coalescence rate. When the crack coalescence rate is constant, the tensile strength decreases with the increase of the crack half-length. The tensile strength of rock mass is inversely proportional to the square root of crack half-length, which shows that the tensile strength of rock mass is nonlinear with the linear change of crack half-length. When the crack half-length is between 0.2 m and 2.0 m, the tensile strength of the limestone rock mass does not exceed 1.0 MPa. The optimized line field analysis method of fracture mechanics is more convenient and faster. And the static equilibrium factor of rock bridge is a key to solve the modified stress value, tensile stress, the stress intensity factor and the shape modified coefficient of rock bridge as well as the rock mass fracture characteristic parameters such as the tensile strength of rock mass with central crack. Meanwhile, the research results have certain theoretical value and engineering significance.

Key words: geotechnical engineering; rock mechanics; fracture mechanics; center crack; tension fracture; line field analysis method

摘要： 背斜核部岩体发育大量拉裂纹，科学解译这一特殊而普遍的地质现象有助于该地区对工程岩体质量的评价、利用并加深对地质灾害演化机制的认识。将位于背斜核部拉应力区的断续裂纹岩体地质模型概化为周期裂纹模型，进一步获取中心裂纹力学模型，引入优化后的线场分析法进行研究。结果表明：裂纹贯通率越高，形状修正系数对裂纹尖端应力强度因子的调增作用越大；应力修正值关于裂纹贯通率具有非线性单调递增特性，关于外荷载呈线性单调递增性质；以灰岩岩体为例，各种理论计算的岩体抗拉强度验证了模型的解是合理的；裂纹半长不变时，岩体抗拉强度随裂纹贯通率增大而降低；裂纹贯通率恒定时，岩体抗拉强度随裂纹半长增加而降低；岩体抗拉强度与裂纹半长的平方根成反比，表现出岩体抗拉强度随裂纹半长线性变化而呈非线性变化规律；裂纹半长介于0.2~2.0 m时，灰岩岩体的抗拉强度均未超过1.0 MPa。经优化后的断裂力学线场分析法更加方便快捷，而岩桥静力平衡因子是求解岩桥应力修正值、岩桥拉应力、应力强度因子、形状修正系数和含中心裂纹岩体抗拉强度等岩体断裂特征参数的关键，研究结果具有一定的理论价值和工程意义。

关键词: 岩土工程；岩体力学；断裂力学；中心裂纹；拉伸断裂；线场分析法