7.2 Stability Analysis of Excavation Face and Calc...
The key to the success of slurry shield construction is to ensure the stability of the excavation face.When large slurry shield is used in the bottom of the water，due to the slope control of the line selection and the influence of the riverbed topography，it is difficult to avoid the shallow overburden in some mileages，which increases the construction risk and technical difficulty.When the shield passes through the ultrashallow overburden section，due to the thin overburden，on the one hand，in order to prevent collapse and roof fall，it is necessary to accurately control the amplitude of support pressure，resulting in a small variation range between the minimum limit and the maximum water pressure，which makes the support pressure of the excavation face difficult to control.On the other hand，the lining segment is affected by the buoyancy of surrounding groundwater and shield tail grouting slurry.When the upper soil pressure and the weight of the segment cannot resist the buoyancy of the segment，it will cause the segment floating，the longitudinal bolt of the segment brittle rupture，and cause engineering accidents.Therefore，how to ensure the stability of the excavation face，reasonably set the tunneling parameters and construction measures is an important topic in the construction of underwater shield crossing shallow soil section.