Research On The Change Law Of Ground Surface Settlement Caused By Shield Tunneling In Hard-soft Heterogeneous Strata

When the shield machine is digging in the soft and hard uneven formation,due to the complex and changeable geological conditions and the fluctuation of the thickness of the soft and hard formation,it is easy to cause a large degree of disturbance to the surrounding soil,causing large-scale and large-scale subsidence.In order to ensure that the shield construction can proceed smoothly in uneven hard and soft strata,reasonable construction methods and construction techniques need to be adopted to ensure the safety of the surface and surrounding buildings.According to a tunnel project in Xuzhou Metro Line 3,the law of surface settlement deformation caused by various influencing factors during shield construction in soft and hard uneven strata was studied,and corresponding settlement control measures were formulated.The main work and conclusions are as follows:(1)From the perspective of the mechanism of surface subsidence caused by shield construction,the main influencing factors of surface subsidence caused by the shield passing through uneven hard and soft strata are analyzed.Combined with the actual engineering geological characteristics of the interval,the main influencing factors affecting the ground settlement were determined,which can be summarized as the combination of soft and hard rock in the excavation section,the supporting force of the excavation face,the effect of simultaneous grouting,and the double-track tunnel The spacing of the axes.(2)The finite element numerical software MIDAS GTS NX is used to establish a three-dimensional numerical model for the construction of shield tunnels with soft and hard uneven strata.Through single factor analysis and orthogonal scheme analysis,the main influencing factors affecting surface settlement are simulated and calculated the study.The results of the study show that the greater the proportion of soft rock in the tunnel excavation surface and the stratum in which the tunnel is located,the greater the surface settlement induced;in this project,the ratio of the elastic modulus of the slurry material to the diameter of the tunnel is the surface settlement The main influencing factor,while the pressure of the earth bunker is a secondary influencing.factor,which has no significant effect on the final settlement of the surface.(3)Comprehensively analyze the ground subsidence law of the measured data and numerical simulation results,and put forward the settlement control measures of the adjacent buildings under shield and soft uneven geological conditions.According to the actual background project,the active control measures were adopted to optimize the driving parameters and construction technology,and the numerical simulation method was used to compare and verify the effect before and after the control measures were taken.The results show that the control measures can effectively reduce the formation disturbance And the amount of ground settlement to reduce the impact of construction on buildings.