Monitoring And Numerical Simulation Analysis For Large-scale Deep Foundation Pit Of KAIDE Square GUTIAN Project

With the rapid development of Chinese economy,urbanization becomes faster.In December 2011,town population have account for more than 50%,the floor space of city average per person's usable turns less.Developing and utilizing underground space has become an effective way to alleviate the pressure of the city ground space.After entering the 21 st century,urban underground engineering is developing at a full speed,all kinds of underground parking,underground traffic,underground mall,underground warehouses can be seen everywhere.The scale and depth of foundation pit turn deeper and lager,the deformation is becoming more and more difficult to control.For large-scale deep foundation pit,especially soft soil area,if the deformation is too large,it's easy to cause the slope instability and heavy losses;If strictly limit deformation within the scope of the safety early warning value,it's certainly that we have to constantly increase the stiffness of supporting structure constantly,as well as reduce the speed of the foundation pit precipitation and excavation,which will not only greatly increase the cost and time of foundation pit engineering,and sometimes is difficult to live up.So,the studying of the deformation law and deformation mechanism of large-scale deep foundation pit has great significance in optimizing the supporting structure and reducing accident in foundation pit engineering.The KAIDE square GUTIAN project foundation pit engineering is a typical large-scale deep foundation pit engineering in soft soil foundation of Wuhan.Many kinds of deformation index in the pit,especially horizontal displacement alarm value have been far beyond specification,but the excavation engineering construction has still finished,without large effects on the surrounding environment.In this paper,we treat KAIDE square GUTIAN project as an example,Through the methods of theoretical analysis,field monitoring,data analysis and numerical simulation.Combining the project form of foundation pit supporting and monitoring datas,studying the large-scale deep foundation pit in soft soil deformation law and deformation mechanism.Combining with the surroundings,construction progress and monitor datas,analyzing abnormal situation and and the main treatment measures during foundation pit engineering construction,summing up a quicksand treatment method in foundation pit of a set of effective measures.The main research work and achievements are as follows:(1)Combining with the foundation pit supporting structure design,making feasible scheme of foundation pit monitoring item,finish monitoring the project of foundation pit engineering,collecting all kinds of the foundation pit monitoring data.(2)Bonding with supporting form of this foundation pit engineering project,analyzing the emphases and difficulties of the foundation pit engineering,combining with the monitoring data,summarizing large deep foundation pit deformation law under the soft soil foundation,researching deformation mechanism.(3)Studying the pavement cracks around of The KAIDE square GUTIAN project foundation pit engineering,and the supporting piles breaking,quicksand in pit bottom,researching the reasons and its control measures adopted.The failed and successful experiences of two governance in foundation pit pit quicksand were studying to summarize up a set of effective methods of foundation ditch quicksand governance.(4)Using large-scale finite element software MIDAS GTS NX,finding a three-dimensional excavation and supporting model of the foundation pit engineering,simulating and analyzing deformation and stress of foundation pit,and comparing with the monitoring data,they are consistent.The count of simulating the excavation calculation shows that maintaining structure can keep stability of the foundation pit,guiding the construction effectively.