Numerical Analysis And Support Optimization Of Deep And Large Special-shaped Foundation Pit

With the development and progress of the times,China’s urbanization process is gradually maturing,a large number of people migrating to the city has caused the city to have land shortage and other problems,so urban buildings continue to develop in the air,underground,high-rise buildings and deep foundation pits have become the product of urbanization development,and then put forward higher requirements for the depth of the foundation pit.The deeper the foundation pit,the more difficult it is to construct on site.Moreover,today’s foundation pit problems are not only limited to depth,but also many special-shaped foundation pits with diverse shapes,irregularities,and irregular shapes.The technical difficulties of foundation pit construction are more complex and three-dimensional,so it is necessary to formulate a more detailed and reasonable construction plan before construction to ensure the safety of the project.Taking a reservoir project in Hefei as an example,this paper compares and analyzes the actual monitoring data with the numerical simulation data,and elaborates the basic deformation theory of the foundation pit.By distinguishing working conditions,a step-by-step numerical model was established,and the safety of each stage of the project was analyzed.Using the control variable method,the bored piles inserted in the project were optimized and analyzed,and a more reasonable support scheme was formulated by comparing with the original data.The main work and research results of the paper are as follows:(1)The current status of research on foundation pit deformation and support optimization at home and abroad in recent years is summarized,and the specific content and practical significance of the research are described according to the actual situation.(2)Several common deformation forms such as surface settlement,foundation pit bottom uplift,and enclosure deformation were analyzed,and their influencing factors and corresponding protective measures were analyzed one by one.The earth pressure is divided into three categories: static earth pressure,active earth pressure and passive earth pressure,and then the Coulomb theory and Rankine theory are analyzed and derived from the active and passive aspects respectively,and the calculation formula of earth pressure is fully studied and applied.In addition,several other earth pressure calculation methods are introduced,and their use in combination can make the calculation results more accurate and close to reality.(3)Combined with actual engineering cases,the surrounding geography and human environment are introduced.The slope excavation method is adopted,which shortens the construction period and meets the project requirements.The project was monitored and distributed,focusing on monitoring the inflection point of the deep and large special-shaped foundation pit,and the change law was studied from the three aspects of horizontal displacement of the top of the enclosure pile,surface settlement and deep horizontal displacement of the enclosure pile,and used this as the actual basis to verify the reliability of the numerical simulation results.(4)Through the finite element analysis software(MIDAS-GTS)to simulate the excavation process of deep and large special-shaped foundation pit step by step,the bored pile in the project is equivalent to the underground continuous wall,and the surface settlement and horizontal displacement of the enclosure pile are simulated according to the inflection point of the deep special-shaped foundation pit,and the change curve is observed by the generated cloud map,and the surface settlement value increases and then decreases with the increase of the distance from the excavation point,and finally tends to a more stable state.The horizontal displacement value of the enclosure pile gradually decreases with the increase of its embedding depth,and finally tends to a stable value,which no longer changes significantly.It is proved that the supporting measures play a positive and reasonable role,and the settlement value and the horizontal displacement value of the enclosure pile do not exceed the early warning value,so the foundation pit is in a safe state as a whole.(5)Through the control variable method,the pile diameter,pile spacing and pile depth of the supporting pile were optimized and analyzed.A control group was set up to analyze the support effect through the change of surface settlement value,and a more reasonable support scheme was obtained,which provided guidance and suggestions for similar engineering cases in the future.Figure [77] table [9] reference [59]...