Analysis of sinkholes in a karst area adjacent to three mines in south China

Abstract

Eighty-six sinkholes occurred in a karst area of 2 km2 from 1990 to 2016, resulting in cracked houses and abandoned farmland. The affected area is adjacent to three underground mines with mining depth up to 600 m below ground. Sinkhole characteristics, hydrogeochemical and isotopic data, and groundwater-gas pressure measurements were evaluated to understand the dynamic karst system. An aquiclude layer was identified between the Triassic Nanlinghu Formation and Donggangling Formation, leading to recognition of two karst groundwater subsystems—Dongmaanshan subsystem and Nanlinghu subsystem. The sinkholes occurred in the Dongmaanshan subsystem where Xinhua Copper Mine and a water supply wellfield are located, and the influence distance can reach 1.2 km. A larger groundwater cone of depression induced by dewatering in a pyrite mine and gold mine in the Nanlinghu subsystem caused differential settlement. Because the sinkhole occurrence is sensitive to groundwater extraction in the Dongmaanshan subsystem, it is recommended that underground engineering activities should be avoided in this subsystem in future land use planning unless effective measures are taken to prevent groundwater level decline and high-frequency groundwater-gas pressure monitoring is implemented.