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Study on permeability and hydrodynamic dispersion in jointed rock

节理岩石渗透率和水动力弥散研究

基本信息

批准号：
07555443
负责人：
ODA Masanobu
金额：
$ 1.09万
依托单位：
Saitama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

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.

1)开展了理论和数值研究，重点是对裂隙几何形状如何影响裂隙体内渗透率和水动力弥散等水力现象有一个基本的了解。渗透率张量kappa&lt；ij&gt；是用长度表示的。裂纹的孔径和取向加上一个无量纲标量波长，这取决于裂纹之间的连通性。通过对Robinson公式的推广，给出了作为现有裂纹密度和各向异性函数的波长的一般表达式。弥散张量D&lt；ij&gt；由两个不同的源组成。第一个原因是，每个示踪剂都被迫沿着方向偏离平均路径的裂缝移动。第二个原因是水头在整个裂纹体中分布不均匀。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，都变得越来越重要。水头分布变得非常不均匀，特别是当总水头坡度平行于裂缝的优先方向时。2)岩石结构可以是定性的，也可以是一般的。用张量描述的。为了说明这种张量如何适用于描述岩石结构的目的，引入了裂隙张量作为节理和断层对岩石结构的指标度量，并对其进行了详细的讨论，以阐明其几何意义。对四个圆柱形花岗岩试件，分别在90℃的热水中浸泡0、180、1030和2000天，进行了检验，以确定是否可以通过纯显微镜观察来确定裂纹张量。将所确定的裂纹张量用于花岗岩试件。渗透率张量的估计与实验确定的渗透率值非常一致。