A Study On Stability And Adjacent Buildings' Deformation Of Retaining Structures Induced By Deep Foundation Pit Excavation

With the gradual expansion of urbanization,the available space of urban surface is gradually reduced,and the development of urban underground space has become an inevitable choice for the development of urban scale.At present,underground space engineering projects have rich achievements and experience,but complex geological conditions,construction environment and other factors have led to greater uncertainty in the actual construction process of underground space projects,and collapse of the retaining structure still occurs frequently.And triggered a series of subsequent disasters.At the same time,the excavation size of the foundation pit project has gradually increased and the depth has gradually increased.The requirements for the deformation of the envelope structure and the settlement of adjacent buildings and ground surface have become stricter.Therefore,it is of great practical significance to explore the variation characteristics of the displacement field of adjacent soil caused by excavation of deep foundation pit and its influence on adjacent buildings.Based on the excavation data of foundation pit excavation in Hangzhou,Shanghai and other places,combined with Plaxis2D numerical simulation and theoretical analysis,the variation characteristics of deep foundation pit excavation process and its influencing factors on adjacent buildings are analyzed.Work and innovation are as follows:(1)By establishing the Plaxis2d finite element model to simulate the influence of the foundation pit damage on the surrounding pit retaining structure and the surrounding environment of the retaining structure:the support failure in each horizontal level causes the axial force of the adjacent horizontal support to increase,and the underground near the inner support The shear force and bending moment of the continuous wall increase,and the maximum point is the horizontal inner support at the bottom of the foundation pit;the horizontal support at the bottom of the foundation pit has the greatest impact on the retaining structure.At the same time,the horizontal horizontal support failure has more obvious influence on the settlement of the ground and deep soil around the foundation pit than the other internal support damage.(2)Based on the engineering geological data of Shanghai and Hangzhou,a large number of finite element models are established.According to the calculation results of the finite element model,when the deformation of the foundation pit retaining structure is flexural deformation,the lateral displacement curve of the ground surface is similar to the surface settlement curve,but the maximum value of the lateral displacement of the ground surface is far from the maximum point of the surface subsidence,and the surface is far away.The maximum value of lateral displacement is smaller than the maximum point of surface settlement;the analysis of finite element results shows that the lateral displacement curve of the ground surface can also be fitted by the skewed distribution curve,and the formula of the lateral displacement distribution curve of the surface when the retaining structure is flexed and deformed can be obtained.And use the actual project to verify.(3)Studying the deep foundation pit project of Kerry Center in Hangzhou with deep excavation depth,deep excavation and tight excavation red line in deep soft clay area,study the proximity of deep foundation pit excavation process The impact of the changing nature of historicity protected buildings.(4)Select the study of five deep-seated subway deep foundation pits in Shanghai soft soil area,and analyze the measured data of different soil conditions,lateral displacement of surrounding structure,adjacent surface settlement and adjacent pipeline settlement.Study the effect of spatial effects caused by deep foundation pit excavation on adjacent pipelines.