| Due to the lack of land resources in the city,it is inevitable to encounter the problem of interaction between adjacent projects.Pile foundation is one of the common foundation forms in engineering construction,when the pile foundation construction is close to the existing tunnel.More attention should be paid to the interaction between the two adjacent constructions.Based on the Shenzhen Qianhai Trading Plaza project as the background,the surrounding environment of the tunnel is divided into three situations:soil layer,rock layer and part of soil layer.The three-dimensional numerical model is established by using the finite element software FLAC3Dto simulate and analyze the influence of rotary drilling construction on the existing underground subway tunnel and the protection measures（1）The principle of the vibration of surrounding environment caused by the construction of rotary drilling is introduced.The dynamic load forms produced by the rotary drilling construction are analyzed,including the excitation force,frequency and loading time.The propagation law of stress wave in medium and relevant control standards are summarized.（2）The reliability of the numerical model of pile soil tunnel is verified by comparing the model with the related research and combining with theoretical analysis.Based on the analysis of the influence of rotary drilling on the tunnel in complex stratum,the paper systematically analyzes the position that rotary drilling has a great influence on the tunnel.With the increase of excavation depth,it appears at the arch top,arch bottom and wall near the tunnel side respectively.It is found that the influence of rotary drilling on the tunnel is greater than that of excavation rock.The technology of full casing wall protection is introduced,and it is concluded that the effect of rotary drilling on subway tunnel can be effectively reduced,and the vibration speed can be reduced by 88%at the maximum.（3）The influence of rotary drilling on the tunnels in different strata is analyzed by numerical simulation.The results show that the influence of rotary drilling on the tunnel in rock stratum is less than that of soil layer,and the maximum vibration velocity of tunnel in rock layer is 75%lower than that in soil layer.The influence of distance between pile foundation and tunnel is studied.It is found that the greater the distance between pile foundation and existing tunnel,the less influence the rotary drilling construction has on the existing tunnel.It is recommended to adopt the construction technology of full casing wall protection downward rotary drilling within 8m of metro tunnel. |
