长江三峡花岗岩坡面管流实验研究

该研究在湖北省秭归县花岗岩坡面下部开挖了一长度为 2 .9m ,深度为 2 .2 3～ 2 .6 0m的土壤剖面 ,经现场观察发现土管主要集中分布在B层 (花岗岩分化程度较高的层次 )和C层 (花岗岩分化程度较低的层次 )的过渡带附近 .在坡面下部坡脚部位垂直于坡长方向上 ,每米宽度大约分布有土管 5～ 7个 .近两个降雨季节的多场天然降雨及管流观测结果表明 ,只要有一定强度的降雨出现 ,土壤剖面中就会产生管流现象 .管流出现的时间、管流历时与降雨强度、降雨历时、土壤前期水分含量和土管所处的土壤剖面位置等因素有关 .土壤水分含量高、降雨强度大时 ,在降雨历时 1h前后即有管流出现 .不同土管的管流流量在一场降雨过程中具有相似的水文波形 ,即上升阶段的历时较短 ,其切线方程表现出较大的正斜率 .随降雨过程的停止 ,管流的水文波形呈缓慢的下降趋势 ,其切线方程表现出较平缓的负斜率 .管流流量对降雨雨强变化响应较为敏感 ,在一次降雨过程中 ,雨强的微小变化会导致管流水文波形的明显反映 .尤其是阵雨的出现 ,会使缓慢下降的管流流量水文波形下降得更为缓慢或转而产生小幅度的回升

A study on pipe flow on the slope of granite region of the Three Gorges Area of Yangtze River.

One soil section of 2.9 m in length, 2.23～2.60 m in depth was dug in the lower part of one granite section in Zigui County of Hubei Province. The on|the|spot observation found that the soil pipes are mainly distributed in the transitional zone between the floor layer B (the higher level of granite weathering) and the floor layer C (the lower level of granite weathering). In the lower part of the slope, where its foot is vertical to the direction of its length, there are about 5～7 soil pipes per meter.During several natural rainfalls in two recent rainfall seasons, the observation on pipe flow indicates that: the pipe flow will appear when the rainfall intensity reaches a certain level, and that the flux of water movement in soil section is much larger than that following Darcy's law. The appearing and lasting time of pipe flow is related to the rainfall intensity, duration of rainfall, the previous water content of soil and the location of soil pipe in soil section.The pipe flow will appear when the duration of rainfall exceeds 1 hour, if the soil water content and the rainfall intensity are high. During rainfall, the pipe flow has similar hydrologic wave shape, namely the duration of increasing phase is short, which is expressed as bigger positive slope. When the rainfall stops, the pipe {flow's} hydrologic wave shape may show a slow downtrend, namely is expressed as mild negative slope. Pipe flow is sensitive to the changes of rainfall intensity during the rainfall. Even a small change of intensity of rainfall will be distinctly reflected in pipe flow's hydrologic wave shape. Especially, showers may make pipe {flow's} hydrologic wave shape downtrend slower, or cause small bounce.