Confined Groundwater Simulation And Land Subsidence Predition In Fuyang City

Land subsidence caused by over exploitation of confined groundwater has become a global issue. It's also a current research focuse at home and abroad , the geological disaster has some characteristics of lower development, long time, extensive influence,enormous destruction and difficult control. Cenozoic loose bed in Fuyang area is about 500m~600m, there are three aquifer systems and two weaken permeable aquifer systems between these aquifer systems,among which the mid-deep and the deep confined aquifer systems are exploitation beds.The continuous high strength exploitation leads to large scale drops of water table continually and consolidation in adjacent aquifer, then induces serious land subsidence in large scale areas.During simulation on land subsidence, the groundwater flow change in the aquifer must be considered. When simulating groundwater flow change in aquifer, the"compression-releasing water"releasing from adjacent clay layer can not be ignored. At present, simulation of seepage is difficult to come true because the groundwater flow in clay layer is not fit to the Darcy flow. Therefore, the relationship equation between"compression-releasing water"and zoned consolidation volume is established, and step computational method is used for computation. Then, the one-dimensional consolidation and three-dimensional flow equations achieve indirect coupling.The monitoring data of water level and the measured data of land subsidence from January in 1996 to December in 2007 are used for model identifying. The result shows that water level isoline and groundwater level process of representative observation wells have high fitting accuracy; the error between calculated cumulate quantity and measured value is less than 3%.As a result, the next eight years of land subsidence cumulate quantity in Fuyang city are forecasted under two exploitation conditions by using the identified coupled model. The predictive values are 1780.2mm and 1715.4mm respectively when the quantity of groundwater exploitation are unchanged and reduced to 80% of maintenance quantity.