基于实测结构面网络的岩体渗流特性分析

以甘肃北山核废料处置预选场址中的某均质区为研究对象,利用实测迹长与隙宽的关系确定隙宽并根据以往的压水试验资料对隙宽进行修正。基于数字化量测方法获得的结构面网络模型,考虑实际地应力的作用,采用离散元方法进行渗流—应力耦合分析,确定了均质区内各测区的等效渗透系数及主渗透方向。根据现场观测的结构面填充和胶结及以往压水试验的反演,将垂直于最大水平主应力方向的结构面隙宽替换为花岗岩等效隙宽进行渗流分析。此外,提出一种反映实际渗流快慢的等效路径渗透系数,该渗透系数是基于连通路径上不同渗流段渗透系数的综合值。在确定等效路径渗透系数计算方法的基础上,研究了各测区最大,最小等效路径渗透系数及其方向(最短渗流路径)。结果表明,该均质区岩体中真实渗流路径上的等效路径渗透系数明显大于渗流断面上的等效渗透系数,而且往往取决于渗透系数最小的渗流段。

Analysis of Seepage Characteristics of Fractured Rock MassBased on Measured Discontinuity Network

One selected homogeneity located in Gansu Beishan radioactive waste disposal candidate site is investigated. The aperture is determined by its relationship with the measured trace length, and is modified according to the previous packer test data. Given the discontinuity network model based on digital method and the effect of in-situ stress on permeability of single fracture, coupled mechanical-hydraulic analysis is performed by discrete element method, giving rise to the magnitudes of equivalent permeability coefficient and principal seepage directions of every zones of selected homogeneity. Based on the on-site observation of the fracture filling minerals and cements on apertures and the inversion of the previous packer test, apertures of the discontinuities which are perpendicular to maximum horizontal principal stress direction are replaced by the equivalent apertures of granite. Furthermore, a method is proposed to reflect the actual seepage velocity: equivalent path permeability coefficient, which makes allowance for integrative features of each seepage segment of one connected path. An application of the method of equivalent path permeability above proceeds through the calculation of the maximum and minimum equivalent path permeability coefficient and seepage direction of every zones (shortest path). Results show that the equivalent path permeability coefficient of the flow path is greatly larger than equivalent permeability coefficient of seepage section and depends on the flow segment whose permeability coefficient is minimum.