Abstract:

To solve the problem of large deformation of tunnel support and high risk of blasting excavation in loose accumulation, based on the entrance section of a tunnel on plateau railway, the twobench method using cantilever roadheader is adopted to excavate the weak surrounding rock of loose accumulation. Based on an excavation test section of about 60 m long on the left and right lines, the excavation plan, construction progress, quality control, safety and environmental protection, and other construction capabilities of cantilever roadheader are summarized, and the applicability of cantilever roadheader is analyzed by comparing with local blasting, excavator and breaker methods in deformation control and technical and economic indicators. The results show that： （1）The accumulative settlement using the cantilever tunnel method is 20 mm, the peripheral convergence is 15 mm, and the linear overexcavation value is ranged from 10 to 15 cm, which are significantly lower than the results of blasting and excavator with breaker. （2）2.5 hours can be saved for each 1.2 m footage of circulation, and the progress of Grade Ⅵ surrounding rock can reach 30 m/month；the noise in the cave is low, and the content of particulate matter is also low. （3）The cantilever roadheader has good adaptability in the accumulation body at the portal section and soft surrounding rocks of Grade Ⅴ, Ⅵ, and Ⅳ, and is most suitable for the section excavation construction with the height range of 4.0 to 7.5 m and width range of 5.5 to 8.5 m by bench method.

Key words: cantilever roadheader, plateau railway tunnel, tunnel portal, loose accumulation, application of cantilever roadheader