广州夏茅村岩溶塌陷灾害特征及防治对策

The Formation Investigation and Remediation of Sinkhole in the Xiamao Village, Guangzhou

通过对广州夏茅村岩溶塌陷进行地质勘察,系统探讨了当地的地质环境条件、岩溶塌陷的灾害特征、岩溶发育条件和岩溶塌陷的形成原因。结果表明,区内第四系覆盖土层厚度大且分布不均,土洞大量发育,隐伏可溶岩的富水性好,溶洞发育;同时,覆盖层内的松散岩类孔隙水与下伏灰岩裂隙溶洞水之间的水力联系密切,含水砂层内地下水位的改变会直接引起下伏灰岩裂隙溶洞水的水位波动,构成岩溶塌陷的水动力因素;钻孔桩施工时钻孔揭穿覆盖层内土洞顶部的黏性土层盖板,造成盖板上部的细砂及淤泥流入土洞,是岩溶塌陷的直接触发因素。在此基础上,提出建立岩溶分布区的地下水动态长期监测网,对岩溶塌陷地段进行灌浆处理,是根治夏茅村岩溶塌陷的主要有效途径。

Sinkholes are common geohazards in karst areas and often cause life and economic losses. Karst collapses are random, fuzzy, sudden, and concealed owing to the randomness of karst cave and karst channel development. On December 19, 2008, five karst collapses and one land subsidence occurred in Xiamao village.The center of this karst collapse is the Northwest street of Xiamao village and Huafu street of Shayuanfang,Baiyun District, Guangzhou(23° 13′40″ N, 113° 14′47″ E). Karst collapses cause wall cracking, building inclination, and subsidence of ground foundation, with a depth of 2-4 m. In August 2015, a karst collapse was induced by drilling of a bored pile at a residential building construction site. Sinkhole hazards in Xiamao village have greatly affected the safety and life of residents. To prevent karst collapses, it is important to investigate the formation mechanism of the sinkholes. Based on the geological exploration of the aforementioned karst collapse in Xiamao village, Guangzhou, we discuss the local geological environment conditions and characteristics of karst development, and causes of karst collapse. The results show that the soluble rocks in and around Xiamao village are Carboniferous Hutian Formation limestone(C2 ht) and Permian Qixia Formation marl and carbonaceous marl(P2 q), hence the frequent karst collapses in the area. The Quaternary overburden in the area is thick and unevenly distributed, with several soil caves at the bottom, and the concealed soluble rock has high water content and is rich in karst caves, providing a good geological environment background for karst collapse.Furthermore, there is a close hydraulic connection between the pore water in the overburden soil and the water in the underlying limestone fractured caves. The change of the groundwater level in the water-bearing sand layer directly causes the water level of the underlying limestone fractured cave water to fluctuate, thus enabling the hydrodynamic factors of karst collapse. During the construction of the aforementioned bored pile, the borehole penetrated the soil cover on the top of the soil cave in the overburden, causing the fine sand and silt on the upper part of the cover to flow into the soil cave, triggering karst collapse. Therefore, establishing a long-term monitoring network of groundwater dynamics in karst distribution areas and grouting the karst-collapsed areas are effective ways for remediation of karst collapse in Xiamao village. Additionally, we can provide technical support to the local government in implementing karst collapse prevention measures in urban planning and construction.