Study on permeability and hydrodynamic dispersion in jointed rock

1)一个理论以及数值研究已经进行了特别强调发展一个基本的理解裂纹几何形状如何影响水力现象，如渗透率和水力分散在裂纹体。渗透性张紧系数kappa_<ij>以长度表示。裂纹的孔径和方向加上一个无量纲标量λ，取决于裂纹之间的连通性。通过推广罗宾逊公式，给出了λ随裂纹密度和各向异性变化的一般表达式。色散张量D_<ij>由两个不同的源组成。第一个原因是示踪剂沿沿着裂纹运动，而裂纹的运动方向偏离平均路径，第二个原因是水头在裂纹体中的分布不均匀。第二个源不仅在裂纹密度较低时，而且在裂纹排列高度各向异性时具有越来越重要的作用。水头的分布变得极不均匀，尤其是当总水头梯度与裂隙的择优取向平行时。2）岩石结构可以定性地，也可以一般地。用张量来描述。为了说明这种张量对岩石结构的描述是如何有用的，引入了裂纹张量作为节理和断层岩石结构的指标度量，并详细讨论了裂纹张量的几何意义。本文研究了四个圆柱形花岗岩试件在90 ℃热水中分别浸泡0、180、1030和2000天后的裂纹张量是否能用纯显微观察来确定。用这样确定的裂纹张量对花岗岩试件进行了分析。渗透率张量的估计与实验确定的渗透率值非常一致。

1) A theoretical as well as a numerical study has been carried out with special emphasis on developing a basic under-standing of how crack geometry influences hydraulic phenomena such as permeability and hydrodynamic dispersion in cracked bodies. The permeability tenser kappa_<ij> is formulated in terms of length. aperture and orientation of cracks plus one more non-dimensional scalar lambda depending on conneetivity among cracks. By extending the Robinson's formula, a general expression for lambda is given as a function of density and anisotropy of existing cracks. Dispersion tenser D_<ij> consists of two different sources. The first comes from the fact that each tracer is forced to move along cracks the directions of which deviate from the mean path. The second comes from non-uniform distribution of hydraulic head throughout a cracked body. The second source has increasing importance not only when crack density is low, but also when crack arrangement is highly anisotropic. The distribution of head becomes extremely non-uniform, especially when overall hydraulic head gradient is parallel to the preferred orientation of cracks.2) Rock structure can be qualitatively, as well as generally. described by using tensors. In order to show how such a tensor is useful for the description purpose of rock structure, a crack tensor is introduced as an index measure for the rock structure by joints and faults, and is discussed in detail to clarify the geometrical meaning. Four cylindrical specimens of granite, which are immersed in hot water of 90 for 0,180,1030 and 2000 days respectively, are examined to see if the crack tensors can be actually determined by purely microscopic observation. Using thus determined crack tensors for the granite specimens. permeability tensors are estimated in good agreement with experimentally determined permeability values.