Abstract: Taking two shallow-buried, water-rich sections of a tunnel with similar geological conditions as the engineering background, a recyclable positioning grouting anchor pipe was developed and applied to the second section after conventional pipe-shed reinforcement used in the first section proved ineffective in terms of both reinforcement and water sealing. During construction, advanced geological prediction radar images were used to assess the degree of rock-mass fragmentation after reinforcement, while construction difficulty was evaluated based on process duration and excavation conditions. The consolidation effect on fractured surrounding rock was examined through visual observations of the tunnel face and changes in the BQ value before and after reinforcement. Water-sealing performance was evaluated according to the water-outflow condition at the tunnel face and variations in seepage volume, and the overall stability of the surrounding rock was assessed through monitoring of displacements inside and outside the tunnel. A comprehensive comparison was conducted in terms of advanced geological prediction, construction process, rock-mass consolidation, seepage variation, and settlement monitoring. The results show that, compared with pipe-shed reinforcement, the positioning grouting anchor pipe can significantly reduce rock-mass fragmentation, improve the surrounding-rock grade, decrease internal and external tunnel displacements, shorten deformation convergence time, enhance water-sealing performance, and markedly accelerate construction progress.

Key words: shallow burial and rich water, pipe shed, positioning grouting anchor pipe, monitor, reinforcement effect