Numerical Simulation Study On Land Subsidence Caused By Urban Construction

Land subsidence is an environment geological phenomenon. Soil surface compression reduces regional ground elevation induced by natural affects and man-made activities. It has some characteristics such as slow development,lasting for a long time,wide impact range,complex mechanism and great difficulty. It is a kind of geological disasters and a threat to resource utilization,environmental protection,economic development,urban construction and the people's livelihood.In recent years,in company with socio-economic instant development and the enlargement of intensity and scale of human engineering activity, the occurrence frequency of land subsidence have a obvious increase trend. At present, the research on land subsidence mainly focused on regional surface subsidence caused by the extraction of deep groundwater, but the impact of urban construction to the settlement has risen to the point that should not be overlooked. In our country, Tianjin is one of the city where have a high frequency of land subsidence. The latest monitoring data shows that settlement caused by urban constructions has risen to about 30 per cent of the total settlement in Tianjin, Particularly the impact of large-capacity high buildings on geological environment is very obvious. So the study on land subsidence caused by urban construction in Tianjin has an important significance not only in theory but also in reality.In the text, on the base of correctly aware the theory how can precipitation in the foundation trench and topside load affect the land subsidence, take the example of Wenzhou mansion foundation trench engineering in Tianjin Tanggu district, respectively proceed the numerical simulation research to the two situation by utilizing the processing modflow and FLAC3D.By the use of processing modflow to simulate the process of the land subsidence caused by precipitation in foundation, we can get the foundation trench interior subsidence, fringe maximal subsidence as well as the influence bound of the sediment. Subsequently, make a simulation and analysis to the factor that can invoke the occurrence of land subsidence and affect the subsidence in the deep foundation trench engineering. Finally, we can conclude some conclusion: the sediment amount have something to do with precipitation drawdown of foundation trench; in the engineering, we can use the low discharge-slow precipitation method in order to decrease the velocity of subsidence and subsidence difference between different location in the foundation trench; the route of disperse the pump well is also could decrease the subsidence difference between different location in the foundation trench; arrangement of the purdah reasonably could decrease the influence of subsidence to the fringe and the external of the foundation trench and the completed building which around the foundation trench, and so on. After the upper work completed, by the use of FLAC3D to make a simulation and analysis to land subsidence and the horizontal shift quantity caused by the topside load. When the calculation is over, we can respectively get the number of the land subsidence quantity of the center point of building and land subsidence quantity of the corner point of building is 113mm, 50mm.The distance of x,y direction movement is respectively 34.7mm and 34.6mm. In the end, I advise some correlative proposal regarding to the land subsidence research.