Study On Influence Factors Of Deep Foundation Pit Deformation Of A Metro Station In Kunming Based On FLAC3D

The rapid development of national economy greatly promote the construction of the urban underground rail transit.The excavation of underground subway station is a typical geotechnical engineering problems.Usually, the subway station laying along the main road with heavy traffic flow and the complex environment. So, the surrounding deformation caused by excavation should been taken serious. This paper takes Kunming metro line 3 as the background, uses finite difference software FLAC3D to analyzes the deformation law of deep excavation in metro station.(1) Analyze the sensitivity of parts of the Cam-Clay model parameters.The change of the parameters influence on displacement of retaining structure and soil.(2) Simulating the excavation procedure of standard section of the subway station deep foundation,concluding the general deformation rule of retaining structure and soil at each stage.(3) Using "virtual displacement method" to apply pre-stress on steel support to study the loss mechanism of pre-stress, and the analysis results shows that the stability axial force after the losing of pre-stress is more representative of the actual construction condition of pre-stress force applied.Research also found that the apply of the pre-stress will change the distribution of axial force between supports in vertical direction. Considering the control of deformation, the apply of pre-stress on steel support can effectively reduce the displacement both on underground retaining wall and the soil, but have a weaker influence on swell deformation in the bottom soil.(4) To keep the total steel support number unchanged, analyzes the effects of adding vertical support to control the deformation.Analysis found that, compared with using double support, to increase the number of vertical support is more effective to control the deformation.(5) Research analysis the influence of soil overbreak to the deformation.For the overbreak at the same position,the deformation of foundation pit will increase non-linearly along with the depth of overbraek increase.For the same overbreak depth in different position, the deformation of retaining structures and soil is more sensitive to the overbreak in deeper layer of soil with higher stress level than the superficial one.(6) Analyze the deformation of foundation pit excavation with considering of segmentation and stage.The result verify the spatial effect of foundation pit and proved the rationality of stage by stage analytical method with simplification using in standard section...