Abstract To enhance the safety and efficiency of mechanized drill-and-blast construction in highway tunnels and address challenges such as difficult mechanized construction and overbreak control in poor rock mass conditions,this paper investigates existing problems and proposes adaptive strategies. Current issues include: limited mechanized construction due to small excavation sections and short safety advance length in poor surrounding rock; inadequate pre-reinforcement at the tunnel face; high safety risks during drilling and manual charging at long exposed unsupported sections; insufficient sprayed concrete compaction, untimely active supporting of anchor bolt, and limited passive bearing capacity of steel arch under the conventional“support first and then bolt”construction process. In response, the paper presents the following countermeasures:(1) A full-process mechanized construction configuration and matching excavation method tailored to different rock grades is proposed, optimizing the safety advance length;(2) For unstable tunnel faces, a combination method of excavation, forepoling, and pre-grouting is proposed;(3) Through theoretical calculations, the minimum section length without steel arch is determined, and based on effective length of pre-support, the traditional“drill-blast-support”process in single-cycle is transformed into the “drill-support-blast”process in two-cycle, improving safety and increasing advance per cycle;(4) A initial support sequence with“bolt first and then support”is proposed, in which active support with bolt and mesh, and primary shotcrete are applied immediately after mucking and scaling, reducing reliance on passive supporting with steel arches. This is supported by resin bolts suitable for active support with bolt and mesh, and early-strength shotcrete process, enabling drilling operations under bolt-and-mesh support, thereby improving safety and operational efficiency.
Abstract：
To enhance the safety and efficiency of mechanized drill-and-blast construction in highway tunnels and address challenges such as difficult mechanized construction and overbreak control in poor rock mass conditions,this paper investigates existing problems and proposes adaptive strategies. Current issues include: limited mechanized construction due to small excavation sections and short safety advance length in poor surrounding rock; inadequate pre-reinforcement at the tunnel face; high safety risks during drilling and manual charging at long exposed unsupported sections; insufficient sprayed concrete compaction, untimely active supporting of anchor bolt, and limited passive bearing capacity of steel arch under the conventional“support first and then bolt”construction process. In response, the paper presents the following countermeasures:(1) A full-process mechanized construction configuration and matching excavation method tailored to different rock grades is proposed, optimizing the safety advance length;(2) For unstable tunnel faces, a combination method of excavation, forepoling, and pre-grouting is proposed;(3) Through theoretical calculations, the minimum section length without steel arch is determined, and based on effective length of pre-support, the traditional“drill-blast-support”process in single-cycle is transformed into the “drill-support-blast”process in two-cycle, improving safety and increasing advance per cycle;(4) A initial support sequence with“bolt first and then support”is proposed, in which active support with bolt and mesh, and primary shotcrete are applied immediately after mucking and scaling, reducing reliance on passive supporting with steel arches. This is supported by resin bolts suitable for active support with bolt and mesh, and early-strength shotcrete process, enabling drilling operations under bolt-and-mesh support, thereby improving safety and operational efficiency.
2025, Vol. 62 