Key Parameters and Integrated Techniques for Mechanized Tunnel Construction via Drilling and Blasting Method

As infrastructure development expands into the challenging mountainous regions of western China, tunnel engineering plays a crucial role in transportation infrastructure. This type of construction is characterized by long distances, large cross sections, significant burial depths, and high altitudes. The drilling and blasting method has emerged as the favored option for tunnel engineering projects because of its flexibility and mature technology. The construction machinery has undergone a transformation from manual construction to small-scale mechanical and then to large-scale mechanical construction, and this mechanized approach has been applied in projects such as Dayaoshan Tunnel, Mihualing Tunnel, and Zhengwan Railway. Currently, the parameters for mechanized construction are primarily derived from engineering experience, and there is a paucity of systematized construction methodologies and quantitative analysis of parameters. Therefore, the Qixingping Tunnel was taken as the engineering baseline. By investigating the characteristics and parameters associated with large-scale mechanical operations, the coverage range and key parameter intervals for multimachine construction were analyzed. The influence mechanism of key parameters, such as excavation method and footage, on the mechanical characteristics of the surrounding rock structure was studied. Numerical simulations revealed that increasing the bench length can lead to a reduction in both the extrusion displacement and structural stress at the tunnel face, with reductions of up to 18.6% and 4.5%, respectively. On this basis, the large-scale mechanized construction site tests were conducted and compared with the traditional tunnel construction in terms of construction efficiency, cost-effectiveness, and surrounding rock control. A monthly footage of 110 meters (a 10% increase in efficiency compared to traditional methods) is achieved, and the number of tunnel face workers is reduced by 26. The aim was to furnish theoretical foundations and technical benchmarks for safe and efficient tunnel construction by the drilling and blasting method.