汶川地震诱发的地面塌陷成因

Cause of Ground Collapse Triggered by the Wenchuan Earthquake

针对目前由汶川地震诱发的地面塌陷研究尚少的现状,以北川县安昌镇开茂村水没河流域地面塌陷坑群为研究对象,根据所处的地质环境条件,通过现场调查、工程勘察及钻孔岩土试验,探讨了地震诱发的地面塌陷成因及机制。认为塌陷区第四系松散层上部含细颗粒的饱和粉土、粉质粘土和下部粗颗粒的饱和砂层、砂砾层等的存在是产生地面塌陷的前提,强烈的地震诱发了砂土液化是产生地面塌陷的内因,而塌陷坑的陆续出现说明了地面塌陷一般都有个时间发展过程,是一种渐进性质的破坏;且地下水动力条件的改变、真空吸蚀作用、余震作用以及强降雨加剧了潜蚀作用,最终导致地面塌陷的产生与发展。结果表明:这些塌陷坑群的出现主要是由地震砂土液化和潜蚀作用共同作用的结果。

According to the current situation of the limited research on ground collapse caused by the Wenchuan earthquake, the groups of ground collapse pit in the Shuimo River Basin are regarded as research objects in Kaimao Village,Anchang Town. The cause and mechanism of ground collapse induced by the Wenchuan earthquake are discussed by site investigation and engineering investigation, embarked on the geological environmental background in the paper. Ground collapse occurs on the premise that the upper area of Quaternary alluvium saturated with fine particles of silt, silty clay, and lower saturated coarse sand, gravel and other produce, sand liquefaction which is trig- gered by the strong earthquake is the internal cause of ground collapse. Furthermore, the emergence of ground col- lapse pits in succession shows that there is a development process of time in common when it occurs, while it is also a gradual damage. And the change of hydrodynamic conditions, vacuum erosion process, aftershocks and heavy rain- fall aggravate the process of suffosion, the interaction of those process results in the emergence and development of ground collapse finally. It is indicated that those collapse pit groups are mainly caused by seismic sand liquefaction and suffosion.