Structural Safety Calculation And Analysis Of Shield Tunnel In Yellow River Crossing Project

The Yellow River crossing project is the key control project of the second phase of the east line of the South-to-North Water Transfer Project.The shield tunnel crossing the Yellow River is planned to adopt the double-layer lining structure of outer segment and inner lining.In the design and construction process of the whole shield tunnel project,the primary task is to obtain the internal force and displacement of the lining under different external loads in each stage,which can be used as the basis for segment section design,material selection and safety checking calculation.Therefore,reasonable design theory and scientific calculation method have important guiding significance for shield tunnel construction.This report adopts the method of three-dimensional numerical fine simulation to analyze the lining structure stress,segment joint deformation,connecting bolt stress and lining structure reinforcement of the lining design scheme in the construction period,operation period and maintenance period.For the construction period,operation period and maintenance period,under different working conditions,first determine the initial calculation conditions,and then select the maximum buried depth of river beach section and the minimum buried depth of river beach section for calculation and analysis.By analyzing the calculation results under different working conditions,the main conclusions are as follows:(1)The maximum compressive stress of the segment during the construction period does not exceed the design value of the compressive strength of C60 concrete,and the local tensile stress exceeds the design value of the tensile strength of C60 concrete,but the distribution range and depth are limited to the local area of the lining surface,which has limited impact on the stress state of the lining,and the segment structure meets the safety requirements.(2)The tensile stress of the segment during the operation period is significantly higher than that during the construction period,but the area where the tensile stress value exceeds the design value of concrete tensile strength is only limited to the local surface area of the segment,which has little impact on the overall stress state of the segment.After water filling during operation,the stress of segment connecting bolts does not exceed the design strength value of materials.When the partial separation of the inner and outer lining within 90° of the upper half of the tunnel is considered during the operation period,the maximum reinforcement rate is obtained,which is the control condition of calculation and analysis.(3)The stress state of the tunnel structure in the maintenance period is generally better than that in the operation period.Therefore,on the basis of ensuring the safety of the lining structure in the operation period,the safety of the lining structure in the maintenance period is also guaranteed.