Optimization and application study of rapid tunneling process using a combined excavation and bolting machine

Based on the geological conditions of the auxiliary transportation roadway 42307 in Wanli No. 1 Mine and the rapid tunneling technology using a combined excavation and bolting machine, it was found that the short parallel working time of excavation and support, as well as the low level of intelligence in the integrated excavation-bolting equipment, are the bottle necks limiting further improvement of the tunneling speed. Through theoretical analysis, engineering analogy, and numerical simulation, a mechanical model for roof stability analysis was established, yielding a limit unsupported span of 1.8 m at the tunnel face. A strong support strategy with reduced bolt density was proposed. The tunnel bolt support system was optimized by adopting high-performance bolts, high pre-tension force, and high system stiffness. Furthermore, countermeasures to improve tunneling speed were provided from aspects including the addition of an intelligent navigation system for the combined excavation-bolting machine, upgrading auxiliary equipment, and equipment modification. Field measurements showed that the optimized support system increased the parallel working time of excavation and support, improving the monthly tunneling advance from 840 m to 1142 m, a 36%increase. Meanwhile, the roof subsidence and convergence of the two ribs were 87 mm and 55 mm respectively, indicating good surrounding rock control.