广州金沙洲岩溶地面塌陷地质灾害成因分析

广州金沙洲是岩溶地面塌陷危害较严重的地区之一，至目前已发生塌陷24个，主要集中分布在某高铁隧道两侧，与隧道垂直距离小于400 m；塌陷的形成与发展与金沙洲地质环境条件脆弱、高铁隧道施工抽排地下水有很大的关系。调查表明，金沙洲北东向断裂构造发育，隐伏灰岩见洞率60 %～76.9 %，线岩溶率最大达52.58 %，部分地段灰岩上覆土体厚度小于15 m。金沙洲某高铁隧道施工期间多个时段排水强烈，排水量达2 000～3 000 m 3 /d，导致地下水位剧烈波动，并引发了20多个岩溶地面塌陷，而在隧道施工之前及在隧道施工不抽排水的个别时段，区内均无塌陷发生。上述岩溶塌陷发育特征表明，脆弱的地质环境条件是金沙洲岩溶地面塌陷的内在因素，而高铁隧道施工抽排地下水则是岩溶地面塌陷的直接诱发因素。

Research on the reason for geologic disaster by karst surface collapse at Jinshazhou in Guangzhou

As one of the most serious karst collapse areas in Guangzhou City, there are 24 collapse spots at Jinshazhou. The collapse spots mainly distribute on the sides of a high speed rail tunnel with the vertical distance from the tunnel less than 400 m. The formation and development of collapses have close relationship with fragile geologic environment and high-speed rail tunnel construction. According to the survey, NE trending fault is quite developed at Jinshazhou, revealed hole-rate between ranges from 60 % to 76.9 % in concealed limestone, the linear karst-rate is up to 52.58 %, the thickness of the overlying earth on some sections of limestone is less than 15 m. Drainage is strong during the construction of high-speed rail tunnel. The amount of pumping groundwater comes up to 2 000～3 000 m 3 /d, which leads to groundwater table severely fluctuates and results more than 20 collapses. There are no collapse occurred when the tunnel stop pumping. The development characteristics of karst collapse shows that fragile geologic environment is the inherent factor leading to karst collapse at Jinshazhou, while the high-speed rail tunnel pumping is a predisposing factor direct leading to collapse.