水力劈裂对岩体中自然裂纹的影响研究

建立了求解自然裂纹和水力裂纹扩展的扩展有限元法，对裂纹附近区域的节点采用广义形函数，并采用线增函数消除混合单元，以提高裂纹附近的精度。引入水力劈裂的非耦合模型，即假设裂纹中的水压力为均布力；用砂浆法（线段-线段接触法）结合增广型拉格朗日乘子法处理受压裂纹段的接触条件。并通过算例分析了以下内容：计算了受压裂纹和裂纹面分布均布水压力的水力裂纹的应力强度因子，并与解析解进行了比较，结果表明，提出的方法具有很高的精度；模拟了水力裂纹对自然裂纹面的影响，并分析了自然裂纹面上的接触力和接触状态。

Influence of hydraulic fracturing on natural fracture in rock mass

The extended finite element method (XFEM) is presented to simulate natural fracture and hydraulic fracture. The generalized nodal shape functions are used in a cluster of nodes around cracks. To improve the accuracy in the vicinity of crack, a ramp function is used to avoid the blending element problem. An uncoupled model is used for hydraulic fracturing, which assumes uniform water pressures at crack faces. The mortar method (segment-segment contact approach) in combination with the augmented Lagrange’s method is adopted to establish contact conditions between the closed natural fracture faces. Several numerical examples are analyzed in detail. In comparisons with analytical solutions, the proposed method obtains higher accuracy on computing the stress intensity factors of the pressurized crack and the hydraulic fracture with the uniform water pressure on the crack faces. The influence of hydraulic fracturing on natural fracture face is simulated, and the contact stress and contact condition on the natural fracture face are further analyzed.