| With the continuous and rapid development of my country’s urbanization process,the development and utilization of underground space is also gradually intensified.In the increasingly rapid development of deep foundation pit projects,it continues to show larger and larger scales,deeper and deeper excavations.Obvious features such as extremely complex surrounding environment.For many years,the design of deep foundation pits has focused on strength control,and it is difficult to meet the sensitive requirements for deformation of the complex environment surrounding deep foundation pit projects.At present,there have been many studies on the deformation control during the construction of deep foundation pits in soft soil areas,and corresponding codes and regulations have been formulated according to the regional characteristics.However,there is little research on how to effectively control the deformation of the foundation pit in the deep foundation pit engineering in the sand and gravel area.Therefore,according to the sand and gravel stratum conditions in Chengdu area,this thesis has carried out research on the deformation law and deformation control of deep foundation pit in Chengdu area.The research contents are as follows:Analyzed deep foundation pit deformation control theory,mainly including deep foundation pit retaining structure type,deformation mechanism,deformation influencing factors,deformation control principle and deformation control method;Based on deep foundation pit survey report and construction data in Chengdu area,the geological environment was analyzed Conditions,and through the analysis of actual monitoring data,the deep foundation pit vertical displacement of the pile top,the maximum lateral displacement of the retaining structure,and the relationship between the maximum surface settlement and the excavation depth and other laws of the deep foundation pit;Through a typical engineering case in Chengdu area,the monitoring The data is analyzed for the vertical displacement of the pile top,the horizontal displacement of the pile,the surface settlement and the deformation law of the support axial force;Use Coulomb GEO5 software to carry out numerical simulation for different working conditions,and the vertical displacement of the pile top and the pile body are compared and analyzed.The simulation and monitoring values of horizontal displacement and surface settlement;according to the deformation law of deep foundation pits in Chengdu area,the proposed value of early warning for deep foundation pits in Chengdu area is proposed.Under this premise,the Coulomb GEO5 software is used to establish a two-dimensional finite element model and analyze the difference Deformation law of foundation pit under pile diameter,different insertion ratio,different ground overload and different precipitation conditions;According to the deformation law of Chengdu area,numerical simulation results,and based on safety and economic analysis,an effective deformation control design method and Deformation control construction measures.The conclusions are as follows:The main manifestations of the deformation of the foundation pit are the uplift of the soil at the bottom of the pit,the deformation and displacement of the retaining structure,and the settlement of the surrounding ground;Geological conditions,design,and construction are the main factors affecting the deformation of the deep foundation;The deformation control of the deep foundation mainly includes deformation prediction,Dynamic design and information construction monitoring and monitoring;the maximum vertical displacement range of the pile top of the enclosure structure is between 0.02%H～0.06%H,the average maximum vertical displacement is 0.04%H;And the maximum lateral displacement of the enclosure structure is 0.02% Within the range of 0.02%H～0.17%H,the average maximum lateral shift is 0.09%H,the maximum lateral shift position is between 0.16～1.10 H,the average position is 0.5H;The maximum surface settlement is between 0.02%H～0.11%H.The average value is0.06%H,and the maximum settlement influence range appears between 0.5～0.7H from the foundation pit;The average value of the maximum lateral displacement of the envelope structure has a linear relationship with the average value of the maximum surface settlement,and the ratio is about 1.34;When the excavation of the foundation pit is shallow,the top of the pile of the partial enclosure structure will bulge,and the horizontal displacement of the pile will increase with the increase of the excavation depth,and the position of the maximum horizontal displacement will move down accordingly;In the early stage of excavation,the ground subsidence was large and uneven settlement occurred.In the later stage of excavation,the settlement value became stable after reaching a certain value;the first support significantly reduced the horizontal displacement of the top of the retaining pile and could affect the pile deformation curve It is parabolic;the deformation trend obtained by using Coulomb GEO5 simulation data and actual data is basically the same,which can reflect the deformation law of the foundation pit;increasing the insertion ratio can effectively control the deformation of the pile.The innovations are as follows:According to the actual monitoring data of a large number of deep foundation pits in Chengdu area,the deformation laws of vertical displacement of pile top,maximum lateral displacement of retaining structure,and relationship between maximum surface settlement and excavation depth are studied,typical engineering cases are used to conduct deformation laws The verification and analysis were performed;And a numerical model was established through Coulomb GEO5 software,and it was foundthat the simulation results are in good agreement with the deformation trends of the monitoring results.The research results of the thesis can be used to guide the design and construction of deep foundation pit engineering in Chengdu area,and provide an important reference for the deep foundation pit deformation control technology in the future. |
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