Shield-driven Construction Cross Existed Line Ground Settlement Regularity & Parameter Optimization

The shield driving method has been one of the main construction methods in the metro engineering of our country. Tunnel construction technology with shield driven method is being widely used in building Metro engineering because of its'unique characteristics and advantages such as intelligence, safety and quickness, etc. However, it is inevitably caused ground surface settlements and soil distortion. Too much ground surface settlements and soil movement caused by shield tunneling can lead to pipelines and buildings around tunnel being damaged, economy expense and society blight.According to this practical project, Beijing Metro No.10 Line crosses under the Beijing Metro No.13 Line existed station structure, this paper has made an overall and systemic analytical study on crosswise surface settlement and the longitudinal surface settlement process which influence by metro tunnel construction with shield driven method through analyzing a mass of site monitoring data. The settlements in different period are concluded, the crosswise surface settlement influence scope, some construction factors to surface settlement has been analyzed too.With FLAC3D, this paper established the shield construction numerical model and simulated the influence on shield tunnel passes through existed structure. Through simulation, found the influence rule on existed structure by shield construction, discussed construction factors such as soil deformation modulus, different thickness of and different elastic modules of equivalent circle zone, control soil pressure, initial stress release rate influence on the surface settlement and structure deformation, studied the reasonable parameter value scope. Comparing with the approached curve and the calculated curve, the credibility of numerical simulation result and the feasibility of predicting the ground settlement through numerical simulation are verified. So it can be used to analyze the structure settlement due to the tunnel construction with shield.Through site monitor and numerical simulation result, technical measure and parameter optimization were given from foundation stability; inject slurry; controlling soil pressure, which mitigate the influence on the structure to least. The best shield construction condition was given at the end.