Abstract: A novel visualizing constant pressure penetration grouting diffusion and reinforcement simulation test device was designed. The ordinary Portland cement 42.5 (OPC), microfine Portland cement (MC), microfine sulphoaluminate cement (MSAC), and self-developed effective microfine cement-based grout (EMCG) were selected, and the penetration grouting diffusion and reinforcement test has been performed. The variation rules of diffusion distance and volume under different suspension and grouting pressures were studied, as well as the effects of grouting material, pressure and sand gradation on the reinforcement. The ANOVA method was adopted to determine the dominant factor for grouting effectiveness, and the macroscopic failure modes of reinforcement specimens were obtained. The microscopic reinforcement model of rock-slurry interface and mineral characteristic were analyzed through SEM method, and the core reasons of reinforcement differences caused by different grouts were revealed. The results show that the grouting material and particle percent in slurry were the dominant factors for the groutability of fine sandy stratum, the increase of groutability was not evident with the increase of grouting pressure. The groutability of EMCG slurry was the best, followed by MC and MSAC, and the groutability of OPC slurry was the worst. The strength improvement of reinforcement specimen was better when the sand gradation was finer when suspensions penetrated fully. The 7 d and 28 d strengths of EMCG reinforcement specimen are higher than those of MSAC, MC and OPC, the 7 d of strength of EMCG reinforcement specimen is greater than 70% value of its 28 d strength. The grout is the dominant factor for reinforcement effectiveness, and EMCG is the best while OPC is the worst. After grouting, the dense C-S-H gels produced in EMCG rock-slurry interface can enhance its bonding strength effectively. Finally, improvement suggestions for practical penetration grouting design have been put forward based on three aspects, which are grouts selection, grouting dynamic control and drilling holes layout.

Key words: porous media of sandy soil, grouting simulation test, penetration diffusion, grouts, reinforcement effectiveness, rock - slurry reinforcement mechanism