红层膨胀岩隧洞开挖变形特征及衬砌支护效果研究OA

To solve the structural stability problems caused by the characteristics of softening and swelling when wetted and shrinking when dried during excavation,taking the tunnels in red bed expansive rock of the Sichuan Basin as the research object,this paper systematically analyzed the excavation deformation characteristics of tunnels and the effect of lining support by combining laboratory tests with numerical simulation methods.The results show that excavation unloading causes the plastic zone to expand to 2～3 times the tunnel diameter,forming an annular shear failure zone,with the maximum principal stress around the tunnel reaching 4.26 MPa(without lining).Lining significantly inhibits surrounding rock damage:the range of the plastic zone is reduced by 33%(narrowed to 1～2 times the tunnel diameter),the crown settlement is decreased by 65.1%(from6.90 mm to 2.41 mm),and the invert displacement convergence is reduced by 11.1%(from22.50 mm to 20.00 mm).Lining optimizes the stress-displacement distribution:the maximum principal stress at 1 time the tunnel diameter is re-duced by 56.6%(from7.05 MPa to 3.06 MPa),and the stable value of vertical displacement is decreased by 44.7%(from 5.12 mm to 2.83 mm).The research results can provide theoretical support for the safety design and construction control of similar projects.