Numerical Simulation And Measurement Analysis Of Construction Mechanics Of Deep Foundation Pit In Jinan Metro

With the continuous developing of urban construction,traffic congestion is becoming tremendous problem.Subway is an effective measure to alleviate urban traffic problems.Because of this development of subway construction,the deep foundation pit engineering of subway station is increasing.The characteristics of long construction period,strict codes' requirements,various construction technology and complex surrounding environment,which is more complicated than the general engineering construction.Due to the lack of research in Jinan area referring to the deep excavation and geotechnical investigation,the study on the construction mechanical characteristics and foundation pit deformation monitoring is required.Based on the case studies of deep foundation pit engineering of Jinan R1 west railway station and R3 new east station,the main contents and conclusions of this thesis are as follows:(1)Based on the widely literature review,the support strut of deep foundation pit engineering,the classical theory of earth pressure calculation and the deformation mechanism are summarized in this report detail.(2)According to the information relating to the geological exploration of Yanmazhuang West Station and the construction plan of deep foundation pit engineering,the numerical simulation analysis is carried out by FLAC 3D,and it is found that the theoretical deformation and stress change of deep foundation pit of subway station are obtained,which provides a reference for the formulation of construction plan on the spot.(3)According to the construction situation,this report optimizes the monitoring scheme of the deep foundation pit engineering of two subway stations,carries on the construction monitoring to the two projects.Through the analysis of the recorded data,the deformation performence of deep foundation pit engineering of subway station in Jinan area is fully determined as follow: the deformation curve of the inner surface settlement of the same monitoring section is "spoon" shape,and the horizontal displacement deformation of the retaining structure along the depth direction presents two small ends.The support axial force increases with the increase of excavation depth,but after the second and third bracing installation,the increasing trend gradually decreases until it is stable.Moreover,according to the different construction environment around the foundation pit,the factors which influence the deformation of foundation pit are analyzed.(4)Comparing the measured results with the numerical simulation,the deformation law is basically the same,but the numerical simulation is relatively idealized.The other factors considering the practical effect during construction process is not take into account such effect has led to the difference in the range of deformation between the two results.Therefore,only by combining the two methods between the field monitoring and numerical simulation,can we grasp the construction state more truthfully and objectively and finally guide the construction to ensure the safety and stability of foundation pit engineering.(5)Because the construction period is tight,there is the phenomenon of removing brace in advance during construction.Through the analysis of the measured data of the lateral support axial force and the horizontal displacement of the wall under the condition of the station deep foundation pit being removed in advance,it is concluded that the foundation pit will be deformed in advance and the supporting axial force on both sides will also increase.The results provide some references to ensure the time of bracing in advance and the strength requirement of concrete under the premise of safety and control.