Abstract: The granite alteration zone of the Gaoligongshan tunnel on the Dali-Ruili railway presents challenges such as high ground stress, abundant water content, high water pressure, well-developed joint and fissure systems, weak and fragmented surrounding rock, uneven hardness of the strata, softening and disintegration upon encountering water, and severe sandification and mudification. In addition, the zone is prone to large deformations, collapses, and water and mud outbursts, leading to TBM jamming. To address these issues, an additional detour guide tunnel is constructed on both outer sides of the main tunnel and the horizontal guide tunnel. Construction is carried out using the drilling-and-blasting method for lateral passages. First, advance geological prediction is conducted for the main and parallel guide tunnels; second, the high ground stress is released in advance and limited drainage is implemented to reduce the water pressure; and third, the granite alteration zones of the main tunnel and the parallel guide tunnel are pregrouted, creating conditions for the jam-release of TBM. Based on the construction risks associated with the granite alteration zone, the results of the first cycle of grouting on the right side of the detour guide tunnel are summarized, and the main grouting parameters are determined through theoretical calculations and on-site construction data analysis. Finally, various techniques, including two efficient drilling methods (large-torque and large-thrust impact rotary drilling, and high-pressure pneumatic drill for deep-hole construction), short-cycle multisegment high-pressure grouting technology, and combined grouting methods using multiple grouting materials, are developed and applied, successfully grouting and blocking the water in the granite alteration zone.

Key words: tunnel, granite altered zone, water gushing and mud outburst, drilling, grouting