Deformation Analysis Of Deep Foundation Pit Excavation Of A Reconstruction Project In Hefei City

With the development of science and technology and the acceleration of urbanization,the contradiction between urban space expansion and land scarcity has become more and more fierce.The development of underground space is also being further exploited,resulting in an increasing scale of foundation pit engineering..Under such a background,the excavation of the foundation pit will inevitably lead to the deformation of the foundation pit,how to control the deformation,ensure the safety of the foundation pit construction,and reduce the damage impact of the project to the surrounding environment has become a top priority.Based on the engineering example of the deep foundation pit reverse construction method of a certain renovation project in Hefei City,according to the deformation monitoring results of the foundation pit engineering,the monitoring data of the lateral wall movement and the surface settlement outside the pit caused by the foundation pit excavation are analyzed.The deformation form and law of the foundation pit during excavation are revealed.Through the software FLAC-3D,the numerical simulation of the deep foundation pit excavation process of the reverse method is carried out.The selection of structural unit,the selection of constitutive model,the determination of model parameters,etc.are discussed,and the underground in the excavation process is obtained.The deformation of the continuous wall,the settlement of the surrounding soil,and the uplift of the pit bottom;and the comparison with the monitoring results,although the simulation results are deviated from the monitoring results,the change laws are basically the same,thus verifying the reliability of the model.The construction of deep foundation pits has certain guidance and reference significance.Through the research of this subject,it can be concluded that the overall shape of the underground continuous wall deformation is arched,and the maximum horizontal displacement is located at the depth of 1/3 of the excavation surface.Therefore,in the construction process of the actual foundation pit excavation,the monitoring points should be arranged reasonably.The key monitoring points should be at the midpoint and corner of the underground continuous wall.The settlement of the surrounding soil presents a groove-like distribution.The maximum settlement of the soil around the foundation pit occurs within 0.5～0.6 times of the excavation depth from the edge of the foundation pit,and the excavation depth range from the edge of the foundation pit is the soil settlement.The key monitoring points,while at the same time 2 times the excavation depth from the edge of the foundation pit,can appropriately reduce the soil settlement monitoring points.With the gradual excavation of the foundation pit,the vertical displacement of the pile top is slightly downward and then increased,but the maximum vertical displacement is negligible,but when the vertical displacement of the envelope is large,it should be immediately Take corresponding measures to ensure the safety of the foundation pit.