Stability Analysis And Model Test For Excavation Of Foundation Pit Closed To River In Hefei

Because the foundation pit engineering in subway is very complicated at its scale and surrounding environment, and the safety and stability are vastly important during the process of subway construction. Grasping the deformation and stress characteristics correctly in the process of excavation is of vital significance for the reasonable design and safety construction of track traffic engineering.On the background of deep foundation pit engineering in Dadongmen railway station, the excavation and the supporting theory are stated. By using the software GeoStudio, we analyzed the impact of water level changes on the overall stability of foundation pit. The distribution of soil pressure and deformation mechanism foundation pit under the excavation were studied by the use of laboratory scale model test, and excavation effect of foundation pit affected by water nearby was also presented. The results are that:(1) Through theoretical analysis, laboratory test and numerical analysis, the earth pressure distribution and deformation mechanism under the excavation of the foundation pit are explored, the process of action, mode of action and effect by nearby water are revealed. The development trend of the earth and regular pattern of the building around the foundation pit can also be obtained.(2) Nanfeihe river has a certain influence to the stability of foundation pit in the Dadongmen railway station; the effect of seepage is bad for the stability of foundation pit. When the depth of underground continuous wall is more than 40 meters, the foundation pit is safe. The depth of underground continuous wall has big difference to the excavation of the foundation pit. In order to ensure the stability and safety during excavation, the depth of underground continuous wall must be large enough.(3) The stress around foundation decrease when the excavation depth is increased; furthermore, the measured soil pressure is greatest when the soil depth is same to excavation depth; it is also mentioning that the variation curves of stress amplitude have obvious inflection points when the excavation is approaching the river. Meantime, the increment of lateral displacement deformation of foundation pit is tending to be great. The cures of displacement not closed to the river will be steady and smooth; however, the curves will abruptly decrease when the soil is at a certain depth.The results provide a reference for the design of subway foundation pit in Hefei as well as other similar projects.