玄武岩体及其层间错动带的渗透性特征  

The Study of Permeability of Basalts and Its Shear Zone

作　　者：蒋小伟[1] 万力[1] 宋刚[2] 王旭升[1] 

机构地区：[1]中国地质大学水资源与环境学院,北京100083 [2]中国水电顾问集团华东勘测设计研究院,杭州310014

出　　处：《工程勘察》2008年第10期25-29,75,共6页Geotechnical Investigation & Surveying

基　　金：国家自然科学基金项目:深部岩体工程特性的理论和实验研究(50639090);国家自然科学基金项目:裂隙岩体渗透性空间分布规律及其渗流特性(40528003)

摘　　要：玄武岩体具有重要的工程价值,而层间错动带在玄武岩体中很常见,很大程度上控制着地下水流场分布。因此玄武岩体及其层间错动带的水文地质特征有必要深入研究。采用压水试验数据,有效地分析了西南某水电站玄武岩中层间错动带C2的渗透特征。比较层间错动带C2所在压水试验段与其上下段的透水率后发现,层间错动带虽然在垂向上主要起隔水作用,但是水平上渗透性较好,其大小受层间错动带的深度和厚度的影响。通过将部分压水试验段的透水率与深度作回归分析,发现地质成因一致、岩性相对均一的岩体,其渗透性与所处深度呈负指数关系,表明了自重应力对渗透性的控制作用。这种渗透性与所处深度之间的负指数关系式中,回归系数受岩性均一程度影响,衰减系数也受岩性的影响。在此基础上,研究了单一层间错动带的渗透性随深度的关系。Rock masses mainly composed of basalts are increasingly encountered in many engineering problems due to their low permeability. Shear zones, which are widely occurred in basalts, have a significant effect on groundwater flow field. As a result, the hydrogeologial characteristic of basalts and shear zones needs to be studied in detail. The permeability of a shear zone, C2, in the basalt of a dam site in southwestern China is effectively analyzed by using packer test data. By comparing the Lugeon values of the test sections tapping the shear zone with that of the adjacent test sections, it is observed that although the vertical hydraulic conductivity of the shear zone is extremely low, the horizontal hydraulic conductivity of the shear zone is large, and the value of horizontal hydraulic conductivity is affected both by its thickness and depth. By using regression analysis, it is found that in the test sections of a rock mass with the same geologic origin and relatively homogeneous lithology, the relationship between the Lugeon values and corresponding depths obeys by the exponential law, which indicates that geostatic stress is a major factor controlling the distribution of permeability. In the exponential model, the coefficient of determination and the decay coefficient are both influenced by the degree of homogeneity of the rock mass. Furthermore, the Lugeon values of the shear zone through depth are obtained.

关 键 词：玄武岩 层间错动带 渗透性 负指数分布 

分 类 号：P641.2[天文地球—地质矿产勘探] P641.73[天文地球—地质学]