Optimization Design And Application Research Of Trench Pit For Pipe Corridor

With the acceleration of urbanization in China,it is an important task to promote the construction of comprehensive pipe corridor to accelerate the short board of urban underground infrastructure.However,the current design theory of support structure ignores the size effect of the pit,and if it is directly applied to the narrow strip type pit of pipe corridor trench,it will be too conservative and lead to poor economy,so it is necessary to improve the theoretical formula implemented by the current specification,so as to realize the optimal design of support structure of pipe corridor trench pit.The optimization of the support structure of the pipe corridor pit is divided into two parts according to the shape of the pit: open excavation section and circular working well.Based on a pipe corridor pit project in Wuhan,this paper uses literature survey,theoretical research and finite element numerical simulation to,firstly,improve the calculation method of the safety coefficient of overturning stability and uplift stability for the narrow strip pit in the open excavation section and analyze the influence of different factors on the overturning stability and uplift stability of the pit;secondly,for the circular working well in the pipe corridor pit,the equivalent calculation method of round arch effect is proposed for the circular working wells in pipe corridor foundation pits,which is convenient for engineering application.The main works are:(1)For the open excavation section of the pipe corridor pit,according to the basic principle of the current code pit stability calculation method,the influence of the width of the pit is added,the calculation formula of anti-overturning stability and anti-uplift stability is derived,and the support structure of the open excavation section case pit profile is optimized by using the modified formula,and a specific optimization plan is proposed.(2)The parameters of the pit profile of the open excavation section are appropriately simplified,and the effects of the pit width,soil parameters and design parameters on the overturning and uplift stability are compared and analyzed,and the calculation results of the theoretical formula implemented according to the current code are compared with the modified theoretical formula in this paper.(3)For the circular working well in the pipe gallery pit,the arch effect of the circular pit was equated to the stiffness coefficient of the horizontal spring support along the idea of the planar elastic foundation beam method,and the formula for calculating the stiffness coefficient of the horizontal spring support was derived based on the analytical solution of the circular cylinder subjected to uniform load in elastic mechanics and the displacement solution formula in material mechanics.Then,the equivalent stiffness coefficient of the arch effect of the circular pit is calculated based on the derived formula in combination with the case pit of the working well,and brought into the Li Zheng deep pit software for calculation,and the calculation results of the support structure design considering the arch effect are obtained.(4)ABAQUS finite element software was used to numerically simulate the case pit.For the open excavation section,the optimized pit model based on the modified formula was brought into the finite element calculation,and the simulation results showed that the optimized model could meet the stability requirements of the pit,thus verifying that it is feasible to design the support structure of the narrow strip type pit for the open excavation section of the pipe corridor according to the modified formula;for the circular working well in the pipe corridor pit,the numerical simulation results were compared with the calculation results of the Li Zheng deep pit software,and it was found that the calculation results of both were very close to each other,thus verifying the rationality of the equivalent calculation method of the circular arch effect.