Study On Building Settlement And Reinforcement Pretreatment In Shield Construction In Taiyuan

Shield tunnel construction will destroy the original equilibrium state of the ground around the tunnel,resulting in loss of soil around the tunnel and resulting in surface settlement.When the distance between the building and the shield tunnel is close,the foundation of the building will also be settled due to the settlement of the lower part and the surrounding soil,causes the building superstructure to tilt or even crack and other problems,this has become one of the core problems that need to be solved urgently in the process of shield tunneling.This article is aimed at the special geological conditions of the floodplain of Fenhe in Taiyuan,construction condition of shield tunnel construction adjacent to shallow foundation building,through theoretical analysis,on-site monitoring and numerical simulation,settlement law of adjacent buildings and different reinforcement pretreatment measures during shield tunnel construction are studied.The main research work and results are as follows:(1)During shield construction,the settlement of each monitoring point of the building mainly occurs between the 30～60 ring after the palm face reaches 20 m in front of the building,the settlement of the building is not obvious when the shield face of the shield reaches the bottom of the building,explained that the existence of buildings constrains the surrounding strata settlement,and the settlement of the buildings is shown as a whole.(2)During shield construction,the presence of surface structures has little effect on the final settlement,settlement change at the same position is less than 1mm.However,it was found that the front of the 10 ring building began to settle when the building existed,Settlement of the 5th ring without construction at the same location began to occur,it is verified that the existence of the building will constrain the surrounding strata,consistent with on-site monitoring data.(3)As the thickness and aspect ratio of shallow foundation buildings increase,the final settlement of the front of the building is reduced,and the settlement of the middle and rear of the building is not obvious,timing of settlement in all parts of the building remains basically the same,it shows that the restrictive change of the surrounding stratum by the building is not obvious and the overall settlement is enhanced.With the grouting pressure,the thrust of the face,the depth of the shield tunnel,the distance between the building and the shield tunnel,settlement of the building changes and the effect of each part is basically the same,which has little effect on the settlement law.(4)Compound anchor pile reinforcement can reduce building settlement,effect of reducing the vertical and horizontal settlement difference of buildings is generally,reinforcement effect is better and economical when the spacing is 1.5 times the pile diameter.Reinforcement around and under the building can effectively reduce building settlement,reduce the difference between horizontal and vertical settlement of buildings,But as the thickness increases,the effect of reducing settlement decreases,surrounding grouting layer plays a major role.Shield tunnel circumferential grouting reinforcement not only reduces the settlement of the building,but also reduces the vertical and horizontal settlement differences,as the thickness of the grouting reinforcement ring increases,the reinforcement effect also decreases.