基于野外水力试验的玄武岩渗透性及尺度效应

在金沙江溪洛渡水电站坝区玄武岩中，进行了3种水力试验，探讨玄武岩渗透性及其尺度效应。平硐渗水试验的试验尺度为1～2 m，渗透系数为10-4～101 m/d，非常离散；地下水示踪试验的尺度为70～145 m，渗透系数为10-0.5～100.5 m/d，非常集中；压水试验的试验尺度为4～7 m，渗透系数值10-2～100 m/d。试验结果显示渗透系数随着试验尺度的增加而增大，笔者认为产生尺度效应的原因在于非均质性。小尺度试验常作用在局部基质段或单条裂隙上，而大尺度试验常穿越几条大裂隙，所获得的渗透系数值要大于前者。在进行裂隙岩体地下水渗流研究时，针对不同尺度的研究对象，应选择不同尺度的野外水力试验来求取渗透系数。

Permeability of basalt and its scale effect based on field hydraulic tests

Permeability of the basalt and its scale effect have been discussed through three kinds of field hydraulic tests at the dam site of Xiluodu Hydroelectric Station. The permeability value K from water seepage test in adits with the test scale 1-2 m is dispersed between 10^-4 and 10^1m/d. K from groundwater tracer test with the test scale 70-145 m is concentrated between 10^-0.5 and 10^0.5m/d. K from water pressure test in borehole with the test scale 4-7 m is between 10^-2 amd 10^0 m/d, Three kinds of test results indicate that K increases with the hydraulic test scale. This paper attributes the scale effect to heterogeneity of fractured rock. Small-scale tests are often performed in local matrix or single fracture with bad connectivity. Large-scale tests often cross a few large fractures or faults with better connectivity so that K is larger than the value from small-scale tests. When we study groundwater flow of fractured rock, for study areas with different scales, field hydraulic tests with corresponding scale should be selected to study the permeability of fractured rock.