Abstract:  During the main tunnel construction at the inclined shaft site Nos. 8, 9, and 10 of the New Wushaoling tunnel in phyllite and slate soft and broken rocks, many challenges were faced, such as the frequent collapse of the tunnel face, primary support cracking, and rock mass deformation and distortion. Accordingly, the data analysis of geological prediction, monitoring measurement, surrounding rock loose circle, construction stage, and support problems in drillandblast construction of the threebench method is studied. The field test method is used to study advance reinforcement using glass fiber anchor rods, advance large pipe shed support, twobench mechanical excavation method for reserving core soil by cantilever excavator, reasonably reserved deformation, foot locking anchorage enhancing the primary support, truss structure strengthening the primary support longitudinal connection, radial grouting, and surrounding rock consolidation. The fieldrelevant results show the following. (1) The reserved core soil twobench largesection mechanical construction using a cantilever excavator is feasible in soft rock tunnels with high ground stress. After using the advance reinforcement and support structure methods, the stabilizing period of support convergence is reduced by over a month.  The support structure′s accumulative deformation is reduced by approximately half compared to the early phase, showing a controllable deformation trend. (2)  The average linear overexcavation using a cantilever excavator can be controlled within 15 cm, reducing the average overexcavation by approximately half of that by drillandblast methods (from 120% to 60%), reducing the construction cycling time by 3 h, and improving the construction efficiency from 25~35 m per month to 50~60 m per month. (3) Large deformation control of soft rock with high ground stress should balance reasonable construction methods, equipment, reserved deformation, and support structures with specific deformation resistance.

Key words: railway tunnel, soft rock large deformation, deformation control, milling method, cantilever excavator