STUDY ON THE EFFECT OF CHEMICAL GROUTING EMERGENCY REPAIR FOR TUNNEL COLLAPSE IN SOFT AND FRAGMENTED SURROUNDING ROCK

Polyurethane/water glass (PU/WG) composite grouting material shows significant promise for use in tunnel emergency repairs due to its excellent mechanical properties and favorable rheological behavior. In response to the engineering problem of tunnel collapse with weak and fractured surrounding rock, this study proposes a rapid rescue plan utilizing PU/WG material for grouting reinforcement. Firstly, to investigate the influence of static mixing layers and aggregate gradation parameters on the grouting reinforcement effect by conducting a systematic indoor experiment. Then, using the results obtained from indoor experiments, a numerical model of local collapse grouting excavation in the tunnel was established. This model facilitated a comprehensive analysis of the mechanisms governing key factors, including the type of grouting material, the range of grouting reinforcement, the range of the collapse-affected area, and the grout solidification time. The indoor experiment results indicate that as the number of static mixing layers increases, the mechanical properties of the pure grout consolidation body are significantly improved, enabling it to achieve a maximum uniaxial compressive strength (UCS) of 60 MPa. The UCS of the pure grout consolidation body rapidly increases within 2 h and can reach 90% of the peak strength. As the non-uniformity coefficient of the aggregate decreases and the particle size increases, the UCS of the grout consolidation specimens containing crushed stones increases, with a maximum uniaxial compressive strength of about 25 MPa. The numerical simulation results show that the type of grouting material plays a dominant role in the grouting reinforcement effect. The order of their impact effects from high to low is PU/WG, Portland cement/water glass (PC/WG), and ordinary Portland cement (PC). The results of this study not only demonstrate the significant performance advantages of PU/WG in tunnel emergency engineering. At the same time, it also provides the theoretical basis and technical reference for related engineering practices.