Research On Land Subsidence Mechanism And Prediction Of Settlement In Cangzhou Area

Due to rapid development of industrialization and urbanization, land subsidenceoccurs commonly in the North China Plain, and has become the main environmentalproblem factor impacting regional sustainable economic and social development.This thesis choose Cangzhou, a typical land subsidence area in the North ChinaPlain as the study object, systematically analyzes the mechanism of land subsidence inthis area, simulates the temporal and saptial change and development ofthe groundwater dynamic field by a groundwater numerical model and then forecaststhe development trend of land subsidence in Cangzhou area.The geological environment data related to land subsidence have been collectedand analyzed comprehensively. With MapGIS spatial analysis method and startingfrom the regional geological and hydrogeological conditions, quantitative relationshipbetween ground settlement and deep groundwater exploitation is concluded inCangzhou region and the North China Plain. Then a typical test borehole in landsubsidence area of Cangzhou was selected to analyze the physical characteristics,compression deformation laws, and permeability characteristics of clay. At last,the mechanism of land subsidence in Cangzhou area is analyzedAccording to regional stratigraphic structure and permeability characteristics ofclay, a groundwater flow model of cangzhou area was built with the ProcessingModflow. With this contructed groundwater model, the maximum water depths of theIII aquifer in two mining conditions in2020were predicted to be106.8m and101.2m, respectively. Regression equations were contructed between water leveldepth and accumulative settlement, and between groundwater abstraction andaccumulative settlement, respectively. With these regression equations, thedevelopment trend of land subsidence in Cangzhou in2020was predicted. The resultsshow that the maximum accumulative subsidence is predicted to be3002.7mm and3004.7mm respectively in the current abstraction pattern, and predicted to be2590.2m and2986.3mm respectively in the reduction of abstraction scenario. Theresults also indicate that the center of ground subsidence is still located in Cangzhou City in the prediction period, which further illustrate the relationshipbetween groundwater exploitation and land subsidence and provide the basis for thecomprehensive management and prevention of land subsidence.Finally, the north section in Cangzhou of the Beijing-Shanghai High-speedRailway was selected as the study area. With considering some facters such as theterrain, landform and engineering geological conditions, using the AHP method andcomprehensive analysis method, a hazard evaluation model was constructed withArcGIS to conduct division evaluation of hazard in the study area. Base on theevaluation results, corresponding prevention measures of ground settlement are putforward, providing the basis for city planning, construction and development in thefuture.