Ground Settlement Of Small Radius Curve Subway Induced By Shield Construction

With the improvement of urban development and the unimpeded and environmental demand for public transportation,China's subway construction has entered a stage of rapid development,and shield construction is gradually applied in the subway construction.The soil deformation and surface settlement induced by subway shield construction will affect the construction safety and become an important risk source especially when penetrating under structure.At present,the settlement analysis caused by subway shield construction is mainly based on linear line,and the applicability of settlement calculation model needs to be further studied under the condition of small radius curve caused by line steering.Through theoretical analysis and numerical simulation,the thesis works the law and influencing factors of surface settlement induced by subway shield excavation under the condition of small radius curve,summarizes the construction settlement control measures,and carries out verification and analysis based on settlement monitoring in engineering cases.The main research work and conclusions are as follows:(1)Considering the formation loss caused by curve fitting correction and the asymmetry of boundary conditions,the Peck formula was modified under the condition of small radius curve;Based on the hypergeometric theory of double-line tunnel,the practical engineering form of Peck formula in the ground settlement analysis of hyperbolic subway shield construction is derived.Considering the influence of the forward tunnel,a proposed formula is proposed to determine the width coefficient of settling trough in the back tunnel.(2)Single curve and hyperbolic subway shield construction models under different buried depths were established by using FLAC3 D program,and the soil deformation caused by subway shield construction under small radius curve was simulated.The thesis systematically analyzes the sensitivity of the influence of curve radius,superstructure additional stress,grouting pressure,soil warehouse pressure,pipe segment model and the change of elastic modulus of grouting equivalent layer on the surface settlement,and summarizes the construction settlement control measures.(3)Combined with the construction control and settlement monitoring analysis of Shijiazhuang metro line 3 small-radius curve shield tunneling,the applicability and effectiveness of settlement control of Peck formula and FLAC3 D numerical simulation in settlement prediction and analysis of small-radius single curve and hyperbolic subway shield tunneling were preliminarily verified.The results show that if smaller radius of curvature and deeper of tunnel is buried,the trend of the distribution for ground settlement trough is larger.If the radius of curvature is not less than 250 m,the settlement difference between the inside and outside of the curve in the transverse distribution of ground settlement is generally not more than 1 mm.In the soil parameters,soil modulus and friction Angle have a high sensitivity to the influence of settlement.When the superstructure's additional stress is small(less than 100 k Pa),it has little influence on the surface settlement,while the additional stress over a certain value significantly increases the surface settlement.