| With the rapid development of urban construction,high-rise buildings and urban subway projects are on the rising,resulting in a large number of deep foundation pit projects.Especially in the construction of deep foundation pit in the soft soil area which near the rivers,due to the lack of research on the degree of deformation control,it is easy to cause adverse effects on the surrounding environment.This research combined with the foundation pit project in the first stage of Lamei Road Station in Ningbo Rail Transit Line 5,exploring the influence of deep foundation pit dewatering excavation on surrounding environment and adjacent viaduct pile foundation in soft soil area which near the river.(1)Combine practical engineering with theoretical research.To carry out on-site monitoring on the deformation of foundation pit and pier,and the corresponding data are analyzed.It mainly analyzes the following four aspects:the horizontal displacement law of foundation pit retaining structure,the settlement law of the ground around the foundation pit,the variation law of the inner support axial force and the settlement law of the Sanguantang Bridge pier.The results show:the horizontal deformation of the envelope structure is a "bow"-shaped change pattern with a maximum horizontal displacement of 17.86 mm.The surface settlement around the ground has a "spoons" distribution,with a maximum settlement of 23.13mm.The axial force of the internal support is increasing with the excavation of the foundation pit.The maximum monitoring pressure value is-1492.64kN and does not exceed the axial force design value.The maximum settlement value of the bridge pier is 10.85mm,andthe uneven settlement of the adjacent pier is 3.09mm,which does not exceed the monitoring and control standards.(2)The finite element software Midas GTS is used to establish the numerical model of the influence of the supporting process of the foundation pit dewatering excavation to the pile foundation of the adjacent bridge.It mainly studies the change laws of horizontal displacement,internal support axial force,external surface settlement of foundation pit,displacement and bending moment and axial force of bridge pile foundation.Then,the results of monitoring data and numerical calculation are compared and analyzed.The deformation development trend of the two is basically consistent,which shows that the analytical model adopted is reasonable and reliable.The simulation results show that the pile foundation deformation and internal force values caused by excavation are within the control range,and the change of the bending moment of the pile foundation is consistent with that of the horizontal displacement of the pile foundation,which indicates that the supporting structure and construction measures used in the excavation of foundation pit can effectively control the deformation of foundation pit.And the influence on the adjacent viaduct is reduced.(3)On the above basis,to change the operating conditions based on the control variable method.Besides,the effects of different excavation depth,different supporting stiffness of foundation pit,distance between foundation pit and existing bridge on horizontal and vertical displacement of bridge pile foundation are studied.The results show that the excavation depth of the foundation pit is positively related to the deformation of the bridge pile foundation.The stiffness of the foundation pit retaining structure and the distance between the foundation pit and the existing bridge are negatively related to the deformation of the bridge pile foundation.The research method in this paper can be used to simulate the actual situation of foundation pit construction,and the theoretical analysis results are in good match with the measured data.In addition,the conclusion can be used as an effective reference for similar projects in the future. |
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