Coupling Relationship between Groundwater and Ground Fissures of Land Subsidence in Xi'an City and Risk Prevention and Control Technology

The ground fissures of land subsidence are developed in Xi'an, which are rare in the world and have been a hot research area in this field. In recent years, new trends have emerged, seriously restricting the development of cities and threatening the safe operation of major projects such as metro. After collecting and analyzing 254 groundwater dynamic monitoring data, this paper summarizes the development history of groundwater resources in Xi'an and the dynamic change law of groundwater head, analyses the relationship between ground fissures in land subsidence and the decline of groundwater level, and puts forward the risk prevention and control technology of ground fissures in land subsidence based on groundwater head management. The results show that the ground fissures of land subsidence in Xi'an are result in the comprehensive action of many factors. The occurrence and development process of these fissures and their severity are closely related to the decline of groundwater head, which have been affected by the thickness of clay layer. The center of groundwater head depression funnel basically coincides with the center of land subsidence in space, and the development time of land subsidence lags falls behind that of groundwater head depression for 2-3 years, and then the subsidence occurs. The related rate is the accumulated maximum land subsidence of 50 mm for every 1 m drop of groundwater head. And the rebound of groundwater head will cause short-term and small amount of land rebound, which can alleviate or restrain land subsidence. After excavated the monitoring data of historical groundwater head and ground subsidence ground fissures, the warning threshold and risk prevention and control technology of ground subsidence ground fissures has been established on the basis of groundwater head.