Researches Of Finite Element Simulation And Measured Datum Analysis Of Excavation Of Deep Foundation Pit

With the development of urban construction, more and more high-rise buildings and underground engineering spring up continuously, producing many problems in deep foundation pit construction. The increase of scale and depth of foundation pit brings unprecedented challenges to designers.Tianjin is located in soft soil area, and its geological conditions are quite complicated due to the weak formation and rich groundwater. The difficulty and risk of deep foundation pit construction is great, with some unfavorable conditions such as too many surrounding buildings, densely covered underground pipeline networks, short distance of roads, and so on. In order to prevent accidents, safety of the enclosure structures must be guaranteed in construction. In order to ensure the safety of deep foundation pit, researches should be done on the soil movements in excavation and the safety and stability of support system. In the paper, analysis and researches were done on a deep foundation pit in Nankai region, Tianjin Province. Based on the summary of previous researches, the arrangement and analysis on the inspection data in construction was done, and then some conclusions were achieved. Combined with engineering practice and finite element analysis, 3-d nonlinear finite element analysis was done on the double-layer ring beams of the foundation pit, using ANSYS. In the analysis, the soil, retaining pile and inside ring beam support system were regarded as a whole, with consideration of the interactions between support system and soil, the stress variation under different conditions was studied at the same time. The comparison between analysis results and field test data indicates that, it is safe to use the support system of double-layer inside ring beam in this project, which is suitable for other deep foundation pits in the region too. Then, according to the grey theory, program was established in the paper, and a method was proposed to predict the deformation and the internal force of the support system of the foundation pit.Based on the investigations above, the thought of combing with the construction monitoring, finite element analysis and continuously forecasting was proposed in the paper. The thought can provide theoretical basis and guidance for practical engineering, which is helpful to improve its design and safety, and it can also provide and accumulate valuable experiences for similar projects.