Numerical Simulation Of Shield Tunnel Construction And The Selection Of Shield In Sandy Pebble Stratum

With the rapid development of cities, in the case of the saturated ground space utilization, utilization of underground space has become the hot spot, especially the construction of urban rail transit is more outstanding. The formation conditions and the surrounding environment on the construction technology require-ments are getting higher and higher, in the construction of urban rail transit, the shield method is widely used for its unique advantages.In sandy pebble formation, clay content is less, between particles and particles through the point-point contact and point-point transmitting force, being borned with discreteness, highly vulnerable to disturbance and deflection. This thesis project is based on the first line and seventh block of Changsha city rail transit, Railway Campus-West new interval shield tunnel project, technological means is Particles discrete element software, the main research is as follows:(1) build a particle discrete element mechanics model, and determining the needed parameters of building numerical model. By studying the discrete element theory, calibration method of the discrete element model parameter is used to determine the model parameters of discrete element model.(2) Establish a granular discrete element model of the shield tunneling process, discuss the influence of the downhill conditions on the limit support pressure on engineering geological conditions and determine the case of the reasonable limit support pressure.(3) change the shield support pressure in the sandy pebble formation, study the instability mechanism on the surface of the shield tunneling.(4) Select monitoring data of the sandy pebble stratum section, analysis and make evaluation, valid development law of the subsidence.(5) make seletion reseach on interval shield of sandy pebble formation based on the first line and seventh block of Changsha city rail transit, and make evaluation the adaptability of shield, state synchronous grouting process of shield in order to make guidance for engineering practice.