粗糙交叉裂隙非线性渗流特性研究
Research on nonlinear seepage characteristics of rough intersection fractures
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摘要: 交叉裂隙是构成岩体裂隙网络的重要部分,研究交叉裂隙的渗流特性对揭示岩体整个裂隙网络的渗流规律具有重要意义。通过建立交叉裂隙数值模型,设置不同的裂隙粗糙度(Joint RoughnessCoefficient,JRC)和交叉角度,求解Navier-Stokes方程,研究交叉裂隙的非线性渗流特性。结果表明:交叉裂隙的水力梯度与流量呈现出非线性关系,均可以用Forchheimer方程拟合;裂隙粗糙度对交叉裂隙的非线性渗流特性影响显著,随着粗糙度的增大,临界雷诺数Rec减小,非达西系数β减小。对局部流动状态进行分析,发现流体流经交叉点后存在明显的偏流效应,水流偏向压力小、速度大的方向,通过计算出口流量比重,验证了这一现象的存在。比较不同初始流动方向下的最大速度和压力,发现渗流方向对交叉裂隙渗流特性有显著影响。Abstract: Intersection fractures are an important component of the fractured networks in rock masses, and studying the seepage characteristics of intersection fractures is of great significance for revealing the seepage patterns of the entire fracture network in rock masses. By establishing a numerical model of intersection fractures and setting different Joint Roughness Coefficients (JRC) and intersection angles, the Navier-Stokes equations were solved to investigate the nonlinear seepage characteristics of intersection fractures. The results show that there is a nonlinear relationship between the hydraulic gradient and flow rate in intersection fractures,which can both be fitted by the Forchheimer equation. The fracture roughness has a significant impact on the nonlinear seepage characteristics of intersection fractures. As the roughness increases,the critical Reynolds number (Rec) decreases and the non-Darcy coefficient (β) also decreases. Through analyzing the local flow states,it was found that there is an obvious flow deflection effect after the fluid flows through the intersection, and the water flow tends towards the direction with lower pressure and higher velocity. The existence of this phenomenon was verified by calculating the proportion of outflow. Comparing the maximum velocity and pressure under different initial flow directions, it was found that the seepage direction has a significant impact on the seepage characteristics of intersection fracture.