MECHANISM AND MODEL OF LAND SUBSIDENCE AFFECTED BY MULTI AQUIFER IN COASTAL MEGA CITY

The elevation of coastal cities is a precious resource. Under the conditions of climate change and sea level rise, land subsidence leads to the loss of elevation of coastal cities, which seriously threatens the safety of cities. It is of great significance to analyze the influence of multi-layer aquifer on land subsidence, study the mechanism of land subsidence and ensure the safe elevation of the city. In this paper, the research site is the mining and irrigation deep wells in Shanghai. We extract water level contour of each aquifer and surface subsidence curve, combined with the superposition of MAPGIS software, and digitize the isopotential line. Then we obtained the data of multi-layer groundwater level and land subsidence from 2011 to 2019 by taking the deep wells of mining and irrigation in Shanghai as sampling points. The correlation between multi-layer groundwater level and land subsidence is established by using multiple regression method. The ground subsidence of regions with relatively high determination coefficient R² is greatly affected by deep groundwater exploitation, recharge and engineering precipitation, while the ground subsidence of regions with relatively low determination coefficient R² is greatly affected by excavation and unloading of engineering construction, long-term load of high-rise buildings and dense building groups, and subway vibration. Our research provides prediction equations for the development trend of land subsidence under the pattern of mining and irrigation in the future, and can provide a reference basis for the control of land subsidence in Shanghai.