Study On The Reinforcement Of Soil For Shield Launching In Sandy Pebble Stratum

The departure of shield tunneling is an important step in the process of shield tunnel construction. The determination of the reasonable area of improve strata could direct affect the shield tunnel construction process safely or not. At present, study on the determination of the reasonable area of departure and arrival of shield tunneling mainly focus on the clay strata. Because of the special mechanical properties about sandy cobble strata, we must establish the reasonable mechanical computational model when determine the reasonable scope of the departure and arrival of shield tunneling.Based on the departure of shield tunneling project in the first line of Changsha subway, establish four simply supported computational model of the mechanical on the improvement area of the departure of shield tunneling about sandy cobble strata, determine the improvement scope of the end strata, use the finite element numerical simulate analysis method, eatablish the3d numerical simulation,anslysis the surface displacement caused by shield originating,vault subsidence,such as content analysis.combine with the actual monitoring data, detail analysis the improvement area of the end about sandy cobble strata. The main contents include:(1) According to the engineering actual situation, using the elastic mechanics and higher mathematics analytic method, carry reasonable simplified on the actual project situation, combined with its boundary conditions, establish reasonable computational mechanical model, list the equilibrium equation、geometric equation and physical equation, to solve the mathematical analytical results;(2) Using the MIDAS/GTS2.6finite element calculation software for geotechnical and underground engineering, establish3d finite element calculation model of the shield starting of the railway station,.Through the calculation of finite element numerical simulation,analysis the calculation results of finite element numerical simulation; (3) Analysis the on-site monitoring data.according to the practical observation data, sunnarizes the surface settlement in sandy pebble stratum of shield starting related laws.and contrast the measured data and finite element numerical simulation data.