Study on deformation and structural mechanics characteristics of intersection sections in high stress ground squeezing surrounding rock tunnels
In order to investigate the asymmetric deformation characteristics and structural damage patterns in tunnel intersections,and to propose the reasonable type and suitable support system for the intersection under the extrusion deformation,the Yulong Snow Mountain Tunnel of Lijiang-Shangri-La Railway is selected as the engineering background in this paper,and based on the field monitoring,the investigation on the structural deformation and biased-pressure characteristics of the intersections sections is performed.On this foundation,the influence range of the intersection is analyzed through numerical simulation to investigate the influence of reasonable intersection type on the tunnel support effect.According to the results of the study,the intersection support structure,under the action of extruded surrounding rock,shows significant asymmetric deformation and biased-pressure characteristics.The support damage mostly occurs at the arch shoulder and arch waist.When a parallel guide tunnel intersects the main tunnel at 45° and is subsequently further excavated,stress concentration is observed on both the acute and obtuse sides of the main tunnel's support,with the acute side experiencing higher stress levels and less deformation,indicating a severe structural biased pressure.The direction of structural biased pressure on the acute side of the main tunnel is related to the distance from the intersection,with a reversal in biased-pressure direction occurring between distances of 0.98D and 1.26D.Compared to 45° skewed intersections,h-shaped intersections prove more effective in distributing the main tunnel's axial stress,circumferential stress,and deformation.
tunnelling engineeringrailway tunnelhigh ground stressextrusion-type large deformationintersection sectionon-site monitoring
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