Optimization Method for Installation Timing of Secondary Lining in Mechanized Tunnel Construction Using Drilling and Blasting Method

In recent years, China has vigorously advocated the construction of mechanized full-process tunnels using drilling and blasting methods. Although this modern construction mode of integrated mechanical equipment can effectively improve excavation efficiency, the overlong distance of mechanical equipment operation lines will seriously delay the timing of the secondary lining support, posing a threat to the stability of the surrounding rock support structure in weak and fractured rock layers. By investigating the relevant principles and control indicators for determining the timing of secondary lining support in tunnel design and construction specifications and sorting out the layout plan of the entire mechanized construction process, a dynamic optimization method for the timing of secondary lining support under the background of mechanized tunnel construction using the drilling and blasting method is proposed. This method integrates the elastic-plastic constitutive model of the surrounding rock, as well as the constitutive models of sprayed concrete, steel arch, anchor rod, and secondary lining. A complete history of the analytical method for the interaction between the surrounding rock and supporting structure is established to solve the bearing limit ratio and load sharing ratio. Finally, the distribution law of the safety factor of the surrounding rock was calculated and analyzed. The results indicate that the effectiveness of the proposed dynamic optimization method for the timing of secondary lining support in mechanized construction has been verified through case analysis: Different reinforced initial support schemes corresponding to a distance of 80 to 120 m for the deployment of mechanical equipment operation lines (the latest support time for secondary lining), and the secondary lining can share 7% to 13% of the surrounding rock load; the overall safety factors of the surrounding rock under the initial support scheme corresponding to the arrangement distances of 80, 100, and 120 m mechanical equipment operation lines are 1.19, 1.30, and 1.26, respectively, which meet the safety control benchmark. © 2024 Chang'an University. All rights reserved.