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The deformation of variable cross-section at the emergency parking belt in soft rock mass highway tunnel is significant than that of the normal section. The deformation related disasters are prone to occur, which is difficult to maintain normal construction in soft rock mass highway tunnels. By taking the Muzhailing Highway tunnel in the section from Weiyuan to Wudu as the research object, the deformation and failure characteristics of variable cross-section at the emergency parking belt was summarized and analyzed. On this basis, the prestressed anchor cable with small diameter was proposed to reinforce the rock mass. The excavation process of variable cross-section was simulated by using FLAC3D finite difference software. The deformation control effects of different reinforcement schemes were compared, and the support effect of selected scheme was verified by field test. The research results show that the deformation of rock mass on the sudden-change side was obviously larger than that on the other side in the range of 15 m at the variable cross-section, when the tunnel was constructed from the emergency parking belt to the normal section. The maximum deformation occurred at the arch foot of the upper bench and the shotcrete cracking, distortion of steel ribs and local deformation intrusion occurred. The rock mass on the sudden-change side has been disturbed many times by the blasting construction. Meanwhile, the restraint of the support structure on the end of the emergency parking belt was weak and the rock mass was softened by groundwater. These were the reasons for the large deformation of rock mass on the sudden-change side. By adopting longitudinal prestressed anchor cable +circumferential prestressed anchor cable to reinforce rock mass at the end of emergency parking belt, the stability of rock mass was enhanced and the deformation was basically symmetrical. The research results provided an important reference for the deformation control of variable cross-section at the emergency parking belt of soft rock mass highway tunnel. [ABSTRACT FROM AUTHOR]

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