Analysis Of The Influence Of Foundation Pit Excavation On Engineering Piles In A Soft Soil Area

With the rapid development of urbanization and the intensification of urban space,the conditions for building projects in limited space are getting higher and higher,and the requirements for foundation pit engineering are also increasing correspondingly.In this paper,a foundation pit project in Kunming City,Yunnan Province is taken as the research background.The thick silty clay is commonly found in the site.During the excavation process,no reasonable layered and subsection excavation is carried out.Has been based on the research background,using three dimensional finite element analysis software MADIS/GTS model of three-dimensional excavation,explores the excavation process,the thickness of earth layering excavation,excavation sequence and excavation every block length of pit engineering horizontal displacement of the pile top,and the change of the internal factors of pit engineering pile engineering horizontal displacement of the pile top,the main conclusions are as follows:(1)The influence of the thickness of excavation in layers on the horizontal displacement of the pile top in the pit was studied,and eight excavation schemes with different thickness of layers were designed.By comparing the simulation results,it can be seen that the horizontal displacement of the engineering pile can be effectively reduced by excavation in layers,and the thickness of excavation in layers is proportional to the horizontal displacement of the pile top.Considering the time and economy of excavation,for the miscellaneous filling soil and soft clay with excavation depth less than 3m,the excavation can be carried out in layers with excavation of 1m each time.For soft clay and silty clay whose excavation depth is between 3m and 5m,layered excavation can be carried out with the thickness of no more than 0.7m each time.(2)The influence of the length of subsection excavation on the horizontal displacement of the pile top in the pit was studied,and four excavation schemes with different subsection lengths were designed.By comparing the simulation results,it can be seen that the subsection excavation can effectively reduce the horizontal displacement of the pile top,and the horizontal displacement of the pile top is proportional to the length of subsection excavation.With the decrease of the length of supranational excavation,the decreasing range of the horizontal displacement of pile top gradually decreases,indicating that if the length of supranational excavation continues to decrease,it has little significance to control the horizontal displacement of pile top of engineering pile,and will affect the economy of excavation.Therefore,the length of subsection excavation is 18 m,and the excavation effect is optimal.(3)Under the same excavation condition,the influence of pile diameter on horizontal displacement of engineering pile is studied.The pile diameter is inversely proportional to the horizontal displacement of the pile top,and the decreasing range of the horizontal displacement of the pile top decreases gradually when the pile diameter changes with an increment of100 mm.It can be inferred that when the pile diameter increases to a certain extent,the horizontal displacement of pile top will no longer change or change slightly.In practical engineering,the diameter of piles can be appropriately increased to reduce the excavation and unloading caused by pile deviation and provide double insurance for construction acceptance.(4)Under the same excavation condition,the influence of pile length on horizontal displacement of engineering pile is studied.The pile length is inversely proportional to the horizontal displacement of the pile top,and when the pile length changes with an increment of1 m,the decreasing range of the horizontal displacement of the pile top gradually decreases.Increasing pile length has some effect on controlling the deviation degree of pile in excavation in soft soil area,but it is inferior to increasing pile diameter.