考虑接触面积影响的粗糙节理渗流分析

Analysis of fluid flow through a rough joint considering effect of contact area

节理中接触面积的存在使得渗流曲折效应更加明显,将对渗流产生显著影响。为了研究节理接触面积对节理渗流的影响,建立节理渗流概念模型,推导得到了节理渗流的接触面积影响系数;然后在节理渗流计算公式中引入该影响系数,得到了考虑接触面积影响的渗流计算公式。同时,由于接触面积的存在使得渗流曲折因子的计算更为复杂,在获得节理隙宽分布的基础上提出了计算节理渗流曲折因子的五点比较法。然后以人工大理岩节理试件为研究对象,在获得其三维表面形貌的基础上,一方面对其进行不同接触状态下5级法向应力作用下的渗流试验;另一方面,在根据节理试件的三维表面形貌数据计算节理的渗流平均曲折因子和接触面积比的基础上,分别采用考虑接触面积影响的渗流计算公式和Zimmerman计算公式对节理试件在不同法向应力作用下的渗流体积流量进行计算,并将计算结果与实测值进行比较。结果表明:考虑接触面积影响的渗流计算公式计算结果与实测值吻合较好,从而验证了考虑接触面积影响的渗流计算公式的正确性,而Zimmerman计算公式高估了节理的渗流流量。

The contact area will make flow tortuosity more obvious and influence the flow rate significantly.In order to investigate the effect of contact area on fluid flow through joint,a conceptual flow model is established to obtain the contact influential coefficient.And the influential coefficient is introduced into the equation for flow rate calculation considering the effect of tortuosity;a new equation considering the effect of contact area is derived.As the contact area makes the calculation of tortuosity coefficient more complicated,an algorithm for calculating the average tortuosity coefficient is proposed based on the joint aperture distribution.An artificial marble joint is taken as an object and the surface topography data are scanned.In one hand,flow tests are carried out on the joint specimen under five levels of normal stresses.In the other hand,on the basis of the average tortuosity coefficients and contact area ratios of joint specimen under five levels of normal stresses calculated according to the joint surface topography data,the volumetric flow rates through joint specimen are predicted by the new equation considering contact area presented in this paper and Zimmerman＇s equation,respectively.Then the predictions of the two equations are compared with experimental observations.It is shown from the comparison results that the predictions of the new equation agree well with experimental observations,while Zimmerman＇s equation overestimates the flow rate through the joint,thus validating the veracity of the new equation.