Numerical Simulation Analysis Of Support Structure Characteristics During Excavation Of Foundation Pit In Soft Soil Area Of Coastal Cofferdam

Based on the deep foundation pit project of a certain land in Changsha Island,Zhoushan City,this paper analyzes the deformation behavior of the foundation pit supporting structure in the soft soil area of the cofferdam in the excavation stage.The finite element analysis software is used to establish a certain place in Changchun Island.The three-dimensional model of the deep foundation pit is numerically simulated.The factors affecting the deformation of the supporting structure during the excavation stage are found through the analysis of the current situation.The orthogonal test table is established by orthogonal test principle to study the sensitivity of the deformation control of the supporting structure.The finite element software is used for simulation analysis;the key factors affecting the deformation behavior of the supporting structure during the foundation excavation stage and their laws are found,and the following conclusions are obtained:(1)In the excavation stage of the foundation pit,the deformation of the supporting pile is in the shape of two small and large bows,which is different from the deformation of the supporting pile in the inland area.The soft soil area of the coastal cofferdam is soft,low in strength and high in compressibility.The large horizontal displacement occurs at a position of about 2 meters below the excavation surface.From the deformation of the supporting pile as a whole,it is known that the deformation conforms to the space-time effect of the foundation pit deformation,that is,the central displacement of the side of the foundation pit.Larger,smaller corners,the position of the maximum displacement of the support pile is also deeper in the middle,and the corner is relatively shallow.(2)The numerical simulation results obtained by using the three-dimensional model established by software show that the deformation law and shape of the simulated retaining piles at other positions are basically consistent with the deformation laws and forms obtained by the on-site monitoring.Since the support pile is simulated by the plate unit,the overall deformation of the support pile is relatively poor due to the better integrity of the plate unit,so the displacement relative deformation of the corner of the simulated support pile is smaller than that of the on-site monitoring.(3)Using the orthogonal test,the five factors affecting the horizontal displacement of the retaining wall are found in the five factors: the thickness of the retaining wall,the depth of the retaining wall,the size of the inner supporting section,the size of the crown beam,and the depth of the intercepting curtain.The two factors are: the thickness of the retaining wall and the size of the inner support section.(4)With the increase of the thickness of the retaining wall,its maximum horizontal displacement is decreasing,while the horizontal displacement of the wall top is increasing;as the size of the inner support section increases,the maximum horizontal displacement of the retaining wall continues.Decrease,but the change is not large,and the horizontal displacement of the top of the wall is reduced by a large margin.