| Deep foundation pit engineering always are surrounded with the complex building environment in city, and it is certain that excavation of deep foundation pit will lead to the strain of surrounding buildings. Reconstruction of deep foundation pit engineering to railway hub in Sha Pingba was simulated by PLAXIS finite element software with finite element model of strengthen and construction of deep foundation pit to analyze displacement and stress and plastic strain and stability during strengthen and construction of deep foundation pit in paper. In the meanwhile, the changes of effective stress and displacement of the soil and internal force and deformation of the supporting structure was researched with the process of deep foundation pit excavation, and the excavated slope stability was analyzed in the process. In order to ensure construction successfully, the surrounding main buildings was detected and the data was analyzed. The main conclusions are as follows.(1)The process of construction was simulated by PLAXIS to analyze displacement change trend during strengthen and construction of deep foundation pit. With the strengthening and construction of deep foundation pit gradually, the stress and deformation of slope soil and the stress supporting structure will change. The maximum horizontal displacement (2.85mm) is in the first step, and the maximum value is in the top of1#retaining wall, and the maximum value decreases gradually to constant value. Reasons for this trend may be anchor rod and the retaining wall reinforcement.(2) The process of construction was simulated by PLAXIS to analyze the change trend of effective stress and the plastic zone. The plastic zone centralized mainly in the anchorage zones and the soil interface and surface contact between excavation of soil and retaining wall. The foundation pit dewatering was adopted in slope in the process of excavation of foundation pit, and effective stress always is about-85kPa ensured the slope stability. Therefore, grouting solidification processing for anchor rod should be timely during the construction, and the quality of grouting must be ensured.(3)The internal force of supporting structure for deep foundation pit was simulated and analyzed by PLAXIS. As a result, axial force of retaining wall was mainly affected by anchor rod and the soil in the wall side. Due to the tension in anchor rod, Retaining wall axial force changes from stress concentration to uniform load along the retaining wall with the increase of excavation deep and retaining wall shear force distribution along the wall body has obvious mutation. The maximum bending moment in retaining wall remain in a stable condition during the excavation.(4)The finite element strength subtraction was used to analyze the stability of foundation pit during process of construction. The safety factor is greater than1.3during process of construction so that it can meet the requirement of the specifications, but the safety factor is with some volatility, so the monitors for displacement and internal force in slope is suggested.(5)The time-displacement curve and displacement vector diagram and result of artificial patrol was analyzed comprehensively. As a result, the monitoring data varied very small and chanced fluctuation (no obvious deformation trend) within the scope of measurement error. Analyzing the monitoring data and artificial patrol, Hua Yu Mansion and Liddell Mansion is not having been affected by the deep foundation pit engineering and the whole buildings is in steady state. |
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