广西来宾市良江镇吉利村岩溶塌陷成因机制分析

Mechanism analysis of sinkholes formation at Jili village,Laibin City,Guangxi,China

2010年6月,一场极端暴雨事件过后,广西来宾市良江镇吉利村发生大规模岩溶塌陷,一个月内陆续产生了17处塌陷坑,其中3个塌陷坑逐渐扩大发展,最终形成一长约170m,深约38m的大塌陷坑,被称为"广西第一塌"。此次塌陷事件影响面积约1 500m^2,导致70户298人搬离家园。为了弄清吉利村岩溶塌陷的成因机制,在塌陷发生地区开展了地面调查、三维激光扫描、地球物理勘探、水文地质工程地质钻探、岩溶塌陷动力条件监测、降雨量监测等多项工作。分析结果表明:吉利岩溶塌陷为自然塌陷,是多种不良因素共同作用的结果,这些因素包括特殊的"水-土-岩"组合和极端暴雨,其中极端暴雨引起的地下水气压力的急剧变化是其主要动力因素;特殊的地质条件,决定了该区岩溶塌陷发生的特殊性,分析其形成过程,认为主要受气爆效应、水击效应和渗流潜蚀效应的综合作用。

After an extreme rainstorm event in June 2010, 17 sinkholes emerged at Jill village, Laibin City, Guangxi in a month. The impact area occupied more than 1,500 m2. Three of the sinkholes expanded and merged gradually and eventually developed into a large sinkhole which is 170 m long and 38 m deep. It is the largest sinkholes in Guangxi. In order to understand the formation mechanism, extensive investigations in- cluding field investigation, three-dimensional laser measurement, geophysical prospecting, exploratory bore- holes and real-time monitoring of karst water pressure and rainfall were conducted. The results indicated that sinkholes at Jill village were attributed to natural factors , which is the result of multiple adverse factors. These factors mainly include the special ＂water soil rock＂ combination and extreme rainstorm. The special geological conditions determine the particularity of the sinkholes. Analyzing the formation process and mechanism of the sinkholes, we think they were mainly controlled by the combination of gas explosion effect, water hammer effect and seepage erosion effect.