Research On Deformation Regularity Of Deep Foundation Pit In Soft Soil Area Of Kunming Lake

The excavation and utilization of urban underground space has become the focus of urban infrastructure,and there are more and more deep foundation pit projects in urban construction projects with the rapid development of urbanization in China.It easily leads to serious accidents and even could cause casualties and huge economic losses for the lack of proper design or precise construction in the actual construction.The research of the deep foundation pit in soft soil area deformation characteristics in Kunming has practical engineering background and research significance,because the origin of soft soil in Kunming area is complex,the engineering geological characteristics is more special,and it has a larger difference compared with China's current national standards which was established that based on the coastal areas.The object of this paper is a deep foundation pit in Kunming soft soil area.The research methods used in this paper include field test,nonlinear finite element method and theoretical method and so on,this paper studied the deformation and internal force of deep foundation pit and supporting structure under the combined arrangement of row piles and annular internal supports,and it also studied the influence on the stability caused by the thickness of support structure and embedded depth,and the results can be the reference of the practical engineering projects.The main contents of this paper are as follows:(1)Analyzing lake soft soil distribution regularity and engineering geological characteristics in Kunming,and putting forward several methods,such as row pile,annular inner support,slope spray anchor net and so on and combining with a large area foundation pit supporting scheme of unloading and reducing load on slope crest,according to the characteristics of a foundation pit in soft soil area of Kunming Lake.It is the first time to use this scheme in Kunming lake soft soil area in Foundation Pit Engineering,and this scheme has the advantages of reliable technology and convenient and safe construction.(2)Determining the content of the deep foundation pit,and the corresponding monitoring points and design programs and details of the content which aimed at the engineering geological conditions of the foundation pit construction in Kunming typical soft soil area.Synthetically analyzing the engineering monitoring data of the foundation pit in order to obtain the dynamic laws of the the supporting structure deformation and internal force in this construction environment.(3)Using the finite element analysis method,that is,MIDAS/GTS software system to build the model of the project,then simulating the related construction parameters,and comparing the simulation results with the actual measurement results.Finally we can found that the two are basically the same,which indicating that the construction can be controlled within the safety range.The corresponding results: With the depth of the foundation pit increased,the corresponding internal support is built,and the maximum displacement of the lateral displacement begins to show a downward trend,The displacement curve of the supporting structure gradually changes from the cantilever type displacement curve to the parabolic displacement curve.(4)There is a further study about the thickness of retaining wall and the influence of the embedded depth on the stability of the supporting structure using the numerical model.The results is that the deformation of the enclosure structure began to decline after the increase of these two parameters,however,the effect of preventing deformation is basically no changing when the two parameters achieve a critical value,but the costs begins to substantially increase.It means that the costs of the structure should be taken into consideration.