【摘要】 "5·12"汶川地震20余天后,在四川省安县的安昌镇东南的李家院子村附近陆续出现了几十个地表塌陷坑并持续扩大。本文以李家院子地表塌陷坑群为研究对象,根据其所在的地层、岩性、地下水、溶蚀作用和上覆土体的工程地质特性定性的探讨了该塌陷坑群的成因。初步认定钙质胶结砂砾基岩的存在是地表塌陷的先决条件;强烈的地震动导致基岩岩体碎裂、解体、塌陷、并压密,同时出现超孔隙水压力,这使上层土体失去支持并开始启动塌陷;余震的地震振动荷载作用导致地下土洞的形成和发展,地下水的变化起到加速作用;上覆土体的工程地质特性决定了塌陷坑在地表的浑圆形状。同时本文也注意到机械溶蚀和隐伏断层活动两种诱导因素的可能,并简要阐述了相关背景依据。更多还原

【Abstract】 More than fifty ground collapse pits were formed in succession about 20 days after the "5.12" Wenchuan Great Earthquake.They were in Lijiayuanzhi village at the southeastern of Anchang town,Anxian county in front of Longmen Shan.This paper analyzes the possible reasons of the pit formation using the properties of strata,rock,groundwater,erosion and topsoil.Primarily,it was the pre-condition that the calcareous cemented sandy conglomerate of Jurassic period presented below the ground surface.The rock collapse and excess pore water pressure caused by serious seismic ground motion were the start-up factors.Aftershocks resulted in the emergence and development of soil holes.Furthermore,groundwater change accelerated this process.Last,the soil engineering properties determined the shape of the pits.At the same time,this paper also pays attention to other possible reasons including buried fault activity and soil particle loss due to groundwater flow.The paper presents the relavant background evidences.It is desirable that this paper would bring some innovative ideas to find out the real reasons of the pit formation.更多还原