Comparison Of Equivalent Circle Zone Method And Displacement Convergence Method In Analyzing Construction Effects Of Shield Tunneling

Shield tunnel construction will inevitably lead to ground disturbance and loss,and cause strata deformation and ground subsidence.If the soil deformation exceeds a certain degree,a series of geotechnical environmental problems will occur.Hence,research on shield construction effects has great significance.Numerical method has the adaptability for specific problems,and the ability to consider geometric nonlinearity and material nonlinearity,thus it is widely used.In this paper,two simple and practical methods,the equivalent circle zone method and displacement convergence method,were used to simulate the construction effects of shield tunneling.Comparison was made for the similarities and differences of the two methods in the analyses.The main research includes:(1)The existing theoretical research on the disturbance of shield tunneling to the soil was introduced.Then the two simple and practical numerical methods,the equivalent circle zone method and the displacement convergence method,were addressed.The new constitutive model used in the thesis was briefly introduced.The plane strain problem of tunneling was analyzed using the equivalent circle zone method and the displacement convergence method through Mohr coulomb model,Modified Cam-clay model and the new model.The results were compared to the Peck’s curve.Comparison was made for the similarities and differences of the two methods in the analyses.In addition,sensitivity analyses of the new model parameters were made on the construction effects of shield tunneling.(2)With the background of the undercrossing project in Suzhou,that the Line No.1 undercrossed Line No.3,a three-dimensional tunneling model was built and analyzed.Comparison of the equivalent circle zone method and the displacement convergence method was made by using Mohr coulomb model and the new model in the analyses.The influence of tunneling on the existing tunnel was predicted and discussed.(3)With the background of the undercrossing project in Guangzhou,that the Line No.3 undercrossed Line No.7,a three-dimensional tunneling model was built using the Mohr coulomb model.Comparison was made between the numerical simulation and measured results.Comparison was made on the performance of the equivalent circle zone method and the displacement convergence method in the three-dimensional tunneling.It was shown that both the equivalent circle zone method and the displacement convergence method were able to simulate the construction effects of shield tunneling in a great degree.As the parameters of the equivalent circle zone can be adjusted,the equivalent circle zone method is more flexible to the ground settlement.Hence,it has a better performance in the simulating the maximum settlement.The displacement convergence method can assign the ground loss ratio directly with clear physical meaning.Hence,the modeling process by this method is more direct,and the simulated shape of the ground settlement curve is closer to the measured data.