Analysis Of Influence Of Shield Construction On Stratum Displacement And Surrounding Rock-liner Effect

The ground subsidence and the damage of lining deformation induced by shield tunnel construction are key issues in the safety control of subway construction.This thesis focuses on the tunnel stratum displacement change trend under the disturbance of shield tunnel excavation and the mechanical effects of surrounding rock-lining interaction.The change law of ground settlement caused by tunnel excavation and the response mechanism of surrounding rock-lining provide a more reliable theoretical basis and practical reference for ensuring the safe construction of tunnels.The main research contents and research results are presented as follows:（1）Based on the refined simulation method,analyze the influence of lining shield tunnel excavation on ground displacement and surrounding rock-lining interaction.With the Yellow Crane Tower Tunnel as the background,using the three-dimensional finite difference software FLAC^3D,the tunnel excavation model is established to analyze the change law of the ground displacement and the surrounding rock-lining mechanism.Results show that the settlement curve is consistent with the distribution curve of Peck’s formula.The shield driving leads to the surface settlement value is slowly increasing,and then sharply increasing and tend to a stable value,finally.The phenomenon of stress concentration has occurred in the front of the tunnel construction.The lining design is up to the specification requirements.（2）Exploring the influence of the stratum displacement which is caused by the parameter of tunnel construction and stratum.Results show that the supporting force of the excavation face has little effect on the surface settlement,and has a significant impact on the stability of the excavation face.The surface settlement can be reduced by increasing the grouting pressure with a reasonable range design value.When the elastic modulus of the grouting body is large enough,the stratum displacement is not changing again.The diameter of the tunnel has a significant effect on the ground displacement,and the effectiveness of the support structure of the large-diameter tunnel should be fully considered in the construction.The ground settlement caused by the construction of the deep tunnel is greater than that of the shallow tunnel.（3）Researching the influence of the force and deformation about the lining which is affected by the parameter of tunnel construction and stratum.Results show that the effect of increasing the supporting force to reduce the deformation of the lining is not obvious.The grouting pressure is proportional to the lining axial force and inversely proportional to the bending moment.Increasing the grouting pressure will bring the hidden safety hazards of the lining arch bottom.The force and deformation of the lining have little relationship with the change of the jack reaction force.The lining of small diameter tunnels has better mechanical performance,and further increasing the diameter of the tunnel based on large diameter will accelerate the damage of the lining.The deep-buried tunnel overestimates the mechanical performance of the lining,and the reasonable burial depth can avoid the excavation of the tunnel in uneven rock formations.（4）According to the results of refined three-dimensional numerical calculations,the stratum convergent deformation mode is obtained and applied in two-dimensional simulation to explore the surrounding rock-lining interaction mechanism under the gap parameters,rock mechanical properties,and tunnel stratum parameters.The results show that the axial force of the lining of large-diameter shield tunnels is often very large,and the elliptical effect of the lining is obvious during construction,indicating that large-diameter shields are more likely to cause failure and destruction of the supporting structure.Rock severity has the most significant impact on surrounding rock stress.The buried depth of the shield is the second,and the elastic modulus of the rock formation is the smallest.