The Research About Influence On Land Subsidence Duing To Pit Dewatering At The Great East Gate Station Of Hefei Rail Transit Line1

With the continuous development of our national economy, more and more cities started using underground space to subway construction as the considering of the growing tension floor space transportation requirements. From August 7, 2009,the city of Hefei officially started construction of the subway project, as to year 2020 total of 12 rail lines complete its construction,according to the plan.For the construction of these projects,there will inevitably form lots of large,deep and complex subway pits and the majority of these pits are concentrated in the urban flow of people, close to many of the surrounding buildings in the downtown. Because the underground water level of Hefei is high, in front of the station construction, pit dewatering must be carried out to ensure that the soil stay in a dry state during the process of pit excavation. Large,deep pit dewatering accompanied with the whole process of pit excavation. There is a correlation between the two, it may lead to adverse influence of the surrounding environment. To the areas with complex geological and water conditions, the dewatering may lead to adverse influence of the surrounding environment, resulting in the loss of the people and state property. In this paper, we take a example of Hefei Great East Gate railway station foundation pit dewatering, using seepage- stress coupling to analysis the impact of land subsidence during the process of pit precipitation and excavation.Firstly, this paper describes the current status of the common foundation pit dewatering studies and common pit precipitation method and its scope of application. Described what is the scene stated pumping tests and how to make use of the hydrological conditions to derivate parameters R, K and give the advice to choose the pit support condition;Then summarize the mechanism of pit precipitation causing land subsidence, conclude the current calculation methods of land subsidence caused by pit dewatering and analysis the existing Great East Gate Station monitoring data;Finally, using software MIDAS / GTS / NX to create the model of Great East Gate Station standard pit in order to react pit dewatering and excavation process of the station,we studied the pit pore water pressure, horizontal displacement envelope, the uplift of pit Bottom;Contrast considering the impact of seepage model and not considering model, and analysis the impact to the relevant parameters of soil changes to land subsidence caused by pit dewatering and excavation.