Research on the Construction Step Distance of Mechanized Double-Side Wall Heading Method for Twin-tube Eight-lane Highway Tunnels
Focusing on the requirements of current relevant specifications on construction step distance,the conflict between the demand for large-scale mechanized construction and the construction step distance was analyzed.Based on the equipment operation requirements,the traditional double-side wall heading method was modified,and a mechanized double-side wall heading method suitable for V-grade surrounding rock was proposed for twin-tube eight-lane highway tunnel,as well as corresponding construction step distance requirements.Three-dimensional numerical simulations of the construction process were conducted to demonstrates the feasibility of the new construction step of the mechanized double-sided wall heading method from the perspectives of the surrounding rock deformation and structural stress.Ultimately,relying on the six tunnels of the Shenzhen-Shantou West Expressway reconstrction and expansion project,on-site deformation and stress monitoring were carried out to verify the safety,scientific validity,and feasibility of the new construction step of the mechanized double wall heading method.Research has shown that based on the working space and convenience needs of large mechanical equipment,the mechanized double-sided heading method formed by the traditional double-sided heading method was optimized,with a construction step distance of at least 60m,96m,and 126m from the primary support ring closure,primary support,secondary lining to the palm face,respectively.The three-dimensional numerical simulation and on-site measurement of the mechanized double-sided wall heading method indicated that with the new construction step,the overall stability of the tunnel surrounding rock and the safety of the support structure meet the requirements of the"Technical Specification for Highway Tunnel Construction".
mechanized double-sided wall heading methodconstruction step distancenumerical simulationon site monitoring