Study On The Impact Zoning And Countermeasure Of New Tunnel Across Existing Urban Road

This paper relies on the national key research and development plan “Typical construction project adjacent to existing urban roads/bridges/tunnel structural risk monitoring,key technologies and demonstrations of safety control” to study the mechanical mechanism and safety risk zoning standards of new tunnels under existing urban roads.,mainly completed the following:(1)By referring to the relevant literature,the mechanical mechanism and stress field distribution of these three states during single tunnel excavation,only vehicle load,and tunnel adjacent to existing urban roads are studied.(2)Using the strength reduction method to analyze the stability of tunnels and tunnels under the existing urban roads,analyze the advantages and disadvantages of the three commonly used surrounding rock instability,and introduce the ultimate shear strain penetration as the surrounding rock instability.According to the criterion,the uniaxial compression test of rock and soil is simulated by numerical calculation,and the ultimate shear strain values under different surrounding rock grades are obtained.(3)Considering the increase of burial depth in the actual stratum,the surrounding rock parameters have volatility and heterogeneity.It is proposed that for the same type of surrounding rock,the most ideal and unfavorable situation(upper and lower limits of surrounding rock parameters)is selected as the criterion for the identification of strong,weak and non-affected areas;(4)Based on the strength reduction method,the mechanical mechanism and safety factor distribution law of single tunnel and single road state are obtained.When the tunnel is adjacent to the existing urban road,consider that the tunnel underpasses the existing urban road into two orthogonal positional relationships: the different surrounding rock,the span-to-span ratio(H/D),and the relative scale(B /D)The safety factor and the distribution law of the affected area under the two kinds of positional relations,and the standard partition map of the tunnel orthogonally crossing and crossing the existing urban road is obtained;(5)Using the basic quality index(BQ)of surrounding rock to quantify the surrounding rock grade,the BQ value and five surrounding rock physical and mechanical indexes(gravity density,deformation modulus,Poisson’s ratio,internal friction angle,cohesion)are obtained.Correlation coefficient,and verify its accuracy,based on the multi-factor(considering surrounding rock,vehicle load,tunnel span,relative scale)under the orthogonal tunneling and lateral wear of existing urban roads Generic impact partition expression;(6)The damage form and mechanical mechanism of the tunnel under the existing urban road are counted.At the same time,the corresponding countermeasure grading is given for the strong influence zone,the weak influence zone and the non-affected zone,which provides reference for similar projects in the future.