土坡失稳的有效降雨量研究

降雨易引起花岗岩残积土边坡失稳。在分析降雨对边坡土体含水率影响的基础上，通过饱和度和含水率的关系推求出土体从非饱和过渡到饱和的有效降雨量。结果表明：对土质边坡，并非所有的降雨都会引起边坡的失稳，降雨入渗使边坡土体从非饱和向饱和状态发展，当边坡土体饱和度达到一定程度的时候易产生边坡失稳；土坡存在饱和区和非饱和区的临界深度，降雨对边坡的影响即为使得该深度以上的土体从非饱和过渡到饱和的过程，须采取不同的抗剪强度来计算处于临界深度上下两部分土体的稳定状态。研究结果对确定土坡失稳的降雨量阀值、进一步认识滑坡失稳机制，对滑坡的预测预报具有理论及实际意义。

On effective rainfall of slope instability

The shallow instability of granite residual soil slope could easily induced by rainfall. Based on the analyses of influence of rainfall on the water content of slope soil, the effective rainfall resulting in soil from unsaturated to saturated condition is derived from the relationship between saturation and water content. Results show that not all rainfall will cause the instability of soil slope, and only when the soil saturation caused by rainfall infiltration reaches a certain degree the slope fails. There exists a critical depth in the unsaturated and saturated zone of slope above which the rainfall infiltration leads to a transition in soil from unsaturated to saturated, different shear strength could be used to calculate the stability of soil which was divided into fluctuation two parts by the critical depth. The soil unsaturated zone and saturated zone can be taken to calculate the stability of the soil condition. The results are useful for determining rainfall threshold of slope instability, so as to further understand the mechanism of landslide instability and landslide prediction.