岩体中不同形式裂隙对渗流压力差损耗的影响

Influence of different rock fractures on loss of seepage pressure differential in rock mass

基于立方定律,推导出不同形式裂隙的流量计算公式,对常见的"人"字形分支裂隙、"T"字形分支裂隙及十字形交叉裂隙的流动规律进行理论和数值分析,认为流体在裂隙分支和交叉处的偏流及交汇作用产生的收缩及扩张效应是压力差耗损大于其他部位的主要原因。引入压力差损耗系数的概念,对公式进行无量纲化处理,得出影响压力差耗损系数的主要因素是雷诺数、裂隙偏转角度及隙宽比。对压力差损耗系数的变化规律进行分析,结果表明:雷诺数的大小与消耗在裂隙分支或交叉处的压力成正比;裂隙偏转角度的增加在一定程度上可以减小压力差的损耗;"人"字形和"T"字形裂隙隙宽比增大,会使流体经过分支或交叉处产生的压力差损耗减小,但由于"十"字形交叉裂隙中同时存在交汇和偏流作用,其结果与上述情况相反。

Calculation formula for different fracture flow is derived based on the cubic law. The formula is used to numerically analyze the flow pattern of several common fractures,including herringbone fracture,T- shaped fracture and crisscross fracture.The contraction and expansion effects caused by interaction and biased flow at the fracture branching and intersection points are believed to be the main cause for greater pressure loss. The formula is processed after non- dimensionalization by introducing the concept of differential pressure loss coefficient. It shows that Reynolds number,deflection angle of fracture and fracture width ratio are the main factors that influence the differential pressure loss coefficient. The analysis on variation of differential pressure loss coefficient shows： the magnitude of Reynolds number is directly proportional to the pressure dissipated at the intersection or branch of fracture; the pressure loss could be reduced by increasing the deflection angle of fracture; with increase of fracture width ratio of herringbone fractures and T- shaped fracture,the pressure loss at the fracture branching and intersection decreases,however,for crisscross fracture,the variation of pressure loss is opposite due to the interaction and biased flow.