Abstract: Large mud and water gushing and soft rock deformation often occur in-tunnel sections with poor geology. Therefore, an L-shaped ground directional drilling and grouting with an entire hole length of over 500 m assisted by in-tunnel advance grouting is proposed for the construction of the Xianglushan tunnel of the Central Yunnan water-conveyance project. The specific design scheme of the proposed method is determined. First, the on-site geological survey results reveal the technical difficulties of the unfavorable geological sections of the Xianglushan tunnel. The construction process and grouting technology of the L-shaped directional drilling grouting are explained. Second, a ground reinforcement scheme for L-shaped ground advance grouting is designed to improve the stratum stability. Finally, the on-site grouting effect is illustrated by tunnel face revelation, grouting results, and magnetotelluric analysis. The results show that the Z1 + Z2 + Z4 drilling field design is the optimal ground advance grouting scheme, and the L-shaped directional drilling grouting assisted with advance in-tunnel grouting technology can cover the grouting area in the blind area, realizing advance reinforcement.

Key words: deep-buried tunnel, water-conveyance tunnel, bad geology section, mud and water gushing, soft rock large deformation, L-shaped ground directional drilling and grouting