Research On Settlement Effect On Surrounding Environment Caused By Dewatering And Excavating For Deep Foundation Pit Of Metro Station In LanZhou

In order to solve the shortage of land and traffic congestion issues in Lanzhou City, the rail transit was developed in Lanzhou, rail transportation is bound to excavate some deep foundation pit. Most of the city subway excavation is closely linked to buildings and municipal facilities, if the precipitation and excavation are not controlled properly. it may result in the sink or tilt of surrounding buildings, and may pose a threat to the building even incalculable loss. Therefore, it is particularly important to the research for the Settlement of surface and surrounding buildings caused by precipitating and excavating in Lanzhou.Rely on Wulipu station project of Lanzhou Rail Transit Line 1 in this paper, during excavation by field measurement and numerical analysis of surface buildings and underground pipelines displacements around the pit were analyzed. The main research contents and results are:(1) Summarize the methods and conditions of dewatering of the Deep foundation Pit Systematically, and the deformation mechanism and calculation of surface subsidence caused by precipitation, precipitation and support ways and methods Wulipu station deep excavation carried out in detail;(2) The analysis of Ground subsidence curves of different pit excavation depth shows that: when the structure strength of foundation pit is good, the vertical displacement curve of outside soil exhibits the "spoon" shape, the maximum surface subsidence occurred at a distance of pit 5 ~ 10 m, the maximum surface subsidence is 26.8mm; when appeared batter piles and broken piles on the envelope during excavation, and appeared sand leaking drain phenomenon, the vertical displacement curve of outside soil exhibits the " triangular " shape, occurred at pit aside,the surface subsidence is 43.5mm; For pit excavation in rich water on Lanzhou area, Ensure the construction quality of the building envelope is very important.(3) The settlement of pipelines on the surrounding of end well of foundation pit are larger, the largest settlement is 39.8mm, Due to the complex construction, During excavation, Pay special attention to the overall settlement and differential settlement,Avoid the pipeline deformation is too large caused by differential settlement.(4) To analysis the Foundation excavation and precipitation process of FSI, analyzing every step of precipitation and sedimentation caused by excavation, the results showed that the effect of precipitation on land subsidence pit can not be ignored, after the excavation is completed, the maximum settlement is 25.6mm, wherein the amount of land subsidence caused by the Foundation precipitation is 9.29 mm, the theoretical settlement excavation should consider the role of water.(5) Considering the dewatering of foundation pit, analysis the simulation value and monitoring value of ground surface settlement, the results show that the excavation considering the dewatering is more can reflect the real deformation of the soil and retaining structure.(6) According to foundation pit dewatering during excavation monitoring data can be seen, the use of drilling bitten pile plus steel support in the form of envelope structure, and the use of well dewatering groundwater treatment methods for ensuring the security and stability of the pit is better.