Study On The Influence Of Static Pressure Pile Construction On The Deformation Of Existing Metro Shield Tunnel

Due to the polymerization effect of the subway,a large number of high-rise buildings are built adjacent to the subway,and static pressure piles are often used for pile foundations.Static pressure piles are dumping replacement piles,which will produce soil squeezing effect,especially the large-area pile group driving will cause large lateral displacement of deep soil,leading to cracks and water seepage of existing subway tunnels.Based on the Xuzhou Zhongshan International Project,this paper uses theoretical calculations,numerical simulations and field measurements to analyze the distribution of the displacement and stress fields of the Q₃ clay layer in the Xuzhou area of statically-pressed piles,and study the influence of single pile,micro-pile group and large-area pile group penetration on the deformation law of existing subway tunnels.The specific work and main conclusions are as follows:（1）Considering the large geometric deformation,contact and material nonlinearity,initial stress field and other factors,the simulation calculation is difficult,and the ABAQUS finite element software three-dimensional static pressure pile penetration process simulation is realized.Based on the Mohr-Coulomb material circular hole expansion theory,the system elaborates the radial displacement value when the surrounding soil is Xuzhou old clay.It has been verified that the theoretical solution of circular hole expansion is basically consistent with the numerical solution curve,and the established three-dimensional static pressure pile penetration simulation finite element method is reasonable.The cloud map of soil displacement around the pile is in the shape of a“gourd”,the ground surface is uplifted and deformed,and stress concentration occurs at the tip of the pile;The radial,vertical displacement and radial stress decay logarithmically with the increase of the radial distance;The lateral displacement of the deep soil within the pile driving depth is greater than that of the shallow soil;The vertical displacement at 10 times the pile diameter hardly changes along the depth direction.（2）The single-pile-soil-tunnel three-dimensional model is established to analyze the law of tunnel deformation caused by single-pile driving.After the pile sinking is completed,the tunnel takes the shape of a"vertical duck egg"and rotates counterclockwise away from the static pressure pile.The horizontal displacement is greater than the vertical direction,the left arched waist has the largest horizontal displacement value,and the right arched waist is the smallest.When the pile sinking speed is lower than 0.1m/s,the maximum displacement value of the tunnel is basically unchanged.When it exceeds 0.1m/s,the displacement value increases exponentially with the increase of speed.There is a"critical pile sinking depth"before which the tunnel displacement value increases as the pile sinking depth increases,and the displacement value remains unchanged when the depth exceeds this depth.Deep-buried tunnels are less affected than shallow-buried tunnels.（3）The displacement value of the tunnel caused by the driving of the micro-pile group is much larger than that of the single pile,and the displacement value tends to be similar to the increase of multiples with the increase of the number of pile driving.The deformation of the tunnel facing the tunnel is the largest,followed by the U-shaped route,and the distance away from the tunnel has the least impact.Excavation of anti-extrusion holes is used to reduce the horizontal displacement of the tunnel by 2%to15%,and the vertical displacement of the vault top and arch bottom are 11%to 14%and 13%to 18%,respectively.（4）In order to avoid the problem of large soil deformation,the simulation calculation of small strain of circular hole expansion is further studied,combined with the hole group effect method,to solve the problem of grid hole grouping,and realize the numerical simulation of large-area group piles.It provides an idea for the future study of large-area pile group driving.Based on the calculation results of the simulation method,it is compared and analyzed with the field measured data.The horizontal displacement value of the right-line tunnel at 10 o’clock is calculated by finite element to be 26mm,which is greater than 21mm of the monitoring data,and the simulation result is more consistent with the change trend of the field measured value.This paper has 81 pictures,9 tables,and 92 references.