| A thorough study at home and abroad on the movement and deformation laws of stratacaused by disturbance of shield tunnel in soft soil, composite soil and loess tunnel has beendone, but less research on shield construction rules and deformation control method of sandand gravel stratum for lack of mature research achievement based on the particularity of SandCobble Stratum. The features of Sand Cobble Stratum is briqetting binderless, unconsolidated,no single stone high strength, poor stability, permeability coefficient, small cohesion and largeparticles. Therefore, studies on the surface settlement caused by the shield construction inpebble stratum settlement is very necessary.This paper discusses the influence of shield tunnel construction on ground disturbanceand the present research status of shield construction, analyzes the factors of soil deformationin the process of tunneling, simulates the tunnel excavation process by use of finite elementsoftware MIDAS/GTS. With the help of GTS, the deformation rules of different drivingpressure, grouting, the overburden thickness of tunnel and shield tunnel excavation method isstudied, time history and range of influence of ground surface settlement is analyzed and theparallels and differences of different ground layer in same excavation method is compared.Simulation study shows that the greater is the overburden thickness of tunnel, the less is theground settlement in same excavation method in Sand Cobble Stratum; the greater is thefitting pressure, the greater is the ground settlement; the quicker is the fitting speed, thegreater is the ground settlement; the bigger the equivalent elastic modulus and Poisson’s ratioof the gravel, the smaller the ground settlement; and two-hole shield tunneling in Sand CobbleStratum is a better method to excavate. Trends of ground settlement and time effect isbasically the same for different layer in the same way of excavation, but the maximumsettlement is different from each other. Therefore, the effect of shield construction parametersto the ground settlement are obviously different. |
