During the construction of tunnels in salt rock strata for the China-Laos Railway,issues such as base collapse and lining cracks have emerged.To ensure the safe construction and healthy operation of these tunnels,a comprehensive study on tunnel section types was conducted using methods including field exploration,numerical calculations,theoretical analysis,and monitoring measurements.The results indicate:(1)The deformation of surrounding rock in the egg-shaped section is slightly less than that in the original horseshoe-shaped section,but the plastic zone area increases significantly.Elliptical and circular sections are more conducive to the stability of surrounding rock.(2)Stress concentration occurs at the vault of the horseshoe-shaped section,while the wall feet of the egg-shaped section experience higher stresses.Elliptical and circular sections exhibit uniform stress distribution,with the elliptical section having a higher safety factor than the circular one.(3)Considering the section area,lining perimeter,deformation rate around the tunnel perimeter,ratio of plastic zone area in surrounding rock,and minimum safety factor as evaluation indicators,along with construction factors,the circular section type is determined to be the optimal choice.(4)After adopting the circular section for tunnel construction,the deformation and stress of surrounding rock are significantly reduced,no cracks are observed in the lining,and the uplift of the invert is improved.
railway tunnelsalt rock stratasection typenumerical calculationanalytic hierarchy processfield measurement
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