Effects of Soil Porosity on Slope Stability and Debris Flow Runout at a Weathered Granitic Hillslope
Effects of Soil Porosity on Slope Stability and Debris Flow Runout at a Weathered Granitic Hillslope
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DOI：
10.2136/vzj2005.0044
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发表时间：
2006-01
影响因子：
2.8
通讯作者：
M. Mukhlisin;K. Kosugi;Y. Satofuka;T. Mizuyama
中科院分区：
文献类型：
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作者：
M. Mukhlisin;K. Kosugi;Y. Satofuka;T. Mizuyama
分析和预测强降雨引起的边坡失稳需要精确的降雨入渗模型。在本研究中，开发了一个数值模型来模拟二维雨水渗入非饱和山坡、饱和区的形成以及由此产生的边坡稳定性变化。随后利用该模型分析了风化花岗岩山坡上土壤孔隙度参数（即饱和土壤含水量θs和有效土壤孔隙度[ESP]）对边坡失稳发生、位移物质的含水条件以及泥石流运动的影响。我们通过施加不同的降雨条件、坡度初始湿度、土壤厚度和坡度进行模拟。结果表明，当斜坡表层土壤的ESP值较大时，其持水能力较大，从而延缓水更深地渗入地下。因此，地下更深处的孔隙水压力的增加也被延迟。这样，较大的 ESP 值有助于延缓边坡破坏。在小风暴条件下，当表层土具有较大的ESP值时，边坡不易发生破坏。然而，较大的ESP往往会增加驱离物的含水量，从而导致移动距离更快、更长，泥石流沉积更多，从而增加下游地区遭受破坏的风险。
Accurate models of rainfall infiltration are needed for analysis and prediction of slope failure induced by heavy rainfall. In this study, a numerical model was developed to simulate two‐dimensional rainwater infiltration into an unsaturated hillslope, the formation of a saturated zone, and the resultant changes in slope stability. This model was subsequently used to analyze the effects of soil porosity parameters (i.e., saturated soil water content θs and effective soil porosity [ESP]) on the occurrence of slope failure, the moisture conditions of the displaced material, and the movement of debris flow on weathered granitic hillslopes. We conducted the simulations by imposing various conditions of rainfall, initial wetness of the slope, soil thickness, and slope gradient. Results showed that when the surface soil of a slope has a relatively large ESP value, it has a greater capacity for holding water and therefore delays deeper water infiltration into the subsurface. Consequently, the increase in pore water pressure in the subsurface at a greater depth is also delayed. In this manner, the greater ESP value contributes to delaying slope failure. Under small storm conditions, slope failure tends not to occur when the surface soil has a relatively large ESP value. However, a greater ESP tends to increase the water content of the displaced matter, which results in faster and longer travel distances, and more deposition of debris flow, thus increasing the risk of damage in downstream regions.