南江“9·16”群发性缓倾浅层土质滑坡特征与成因机制研究

Study on characteristics and cause mechanism of grouping inclined-shallow soil mass landslides on September 16,2011 in Nanjiang

2011年"9·16"特大暴雨在四川南江县诱发数以千计的群发性缓倾浅层土质滑坡,且滑坡集中发生区域往往都是稳定性较好的大片良田和村落聚集地,值得高度关注。在充分调查研究此类滑坡特征与形成条件的基础上,利用Geo-studio数值分析手段及室内试验,系统地研究了强降雨条件下此类斜坡的入渗特征和稳定性状况。结果表明:这场暴雨在坡体内的入渗存在6m的最大入渗深度,湿润区所能涉及的范围有限;随着饱水浸润历时的增长,土体抗剪强度不断衰减,持续软化作用明显;土层越薄,基覆界面被浸润软化的时间越长,相应抗剪强度越低。降雨入渗特点和土体的饱水软化作用是导致滑坡呈现上述特点的主要原因。

Thousands of slow- inclination shallow soil landslide generated on September 16,2011 in Nanjiang County,Sichuan Province. Landslides typically occur over a large sheet of farmland and villages,it is worth concerning.A finite element software,Geo- Studio,was used to study the infiltration characteristics and stability conditions of landslides under the heavy rainfall on the basis of comprehensive investigations and studies the formation conditions and characteristics of landslides. Results from the parametric analyses show that: there is the biggest infiltration depth of 6m for the rainfall,and the moist area is limited; with an increase in infiltration time,shear strength of soil decreases continuously,the continued softening effect is obvious; the thinner the soil layer,the longer the time for softening of bedrock-cover interface and the lower the corresponding shear strength. The infiltration characteristics of rainfall and the softening effect of soil are the key factor to induce the shallow soil landslide.