Study On Ground Disturbance In Sandy Stratum Using Earth Pressure Balance(EPB)Shield

Based on the interval shield tunnels of metro in china,the mechanism of ground disturbance caused by EPB shield tunneling was discussed.Using the ?800mm EPB shield tunneling model test system,the dynamic driving process of EPB shield tunneling was fully simulated,and the impact of EPB shield tunneling on the ground displacement was analyzed.Meanwhile,the granular discrete element numerical method(DEM)was used to analyze the impact of ground loss on the ground displacement and the tunnel face stability respectively.The main works and research achievements include:1.The whole process of laboratory test of EPB shield tunneling,which include face excavation,discharging earth,advance,segment installation etc.was carried out by using the?800mm EPB shield tunneling model test system.And both the horizontal and vertical ground displacement were measured.2.Using the discrete element numerical method(DEM),the biaxial test models were established considering different ground loss,the influence law of the ground displacement.The relationship between macroscopic parameters and macroscopic parameters of sand was calibrated.And the ground stress caused by different ground loss was obtained.Furthermore,according to the final settlement of model tests,Peck formula was used in the inversely calculates.Firstly,the coefficient of surface subsidence trough width and ground loss were obtained by model tests;Secondly,the ground loss of four sections acquired by model test was equivalent to the shield tail void of the DEM models;and then the four different shield tail voids of DEM models were considered,Finally,the surface subsidence trough was obtained and compared with that of model tests.3.Using servo control method to study the face stability under different site-stress.By setting different support stress ratio of excavation face,the effects of different excavation face support stress ratio on excavation face deformation and surface displacement was analyze.And based on this,a reasonable excavation face support stress ratio was put forward to maintain the stability of excavation face.