Experimental study on the effect of water-cement ratios on the diffusion behavior of sand soil grouting

The grouting technique has been widely applied in geotechnical engineering. However, due to the concealed nature of underground engineering, there is relatively limited research on the diffusion characteristics of grout in sandy soil. This study utilized a self-developed three-dimensional grouting model test system. Experiments tests were conducted using standard sand and different water-cement (w/c) ratios of grout under limited boundary conditions, diffusion mechanism of sand soil grouting revealed. It was found that lower w/c ratios require higher grouting pressure when injecting grout into the sandy soil. The grouting pressure exhibited a pulsating pattern over time and a grouting pressure up to 323.9 kPa at w/c = 0.6. The grouting diffusion pattern under all w/c ratio conditions displayed typical columnar diffusion, and there was a good linear relationship between the average diffusion radius of the grout and the w/c ratio; the average diffusion radius was between 121 and 208 mm. The volume of the grout bulbs varied significantly at different w/c ratios, decreasing as the w/c ratio increased. With increased grouting pressure and w/c ratio, the dewatering effect during the grouting process became more pronounced, and the bleeding rate of the slurry with w/c = 1.4 (67.1%) is more than six times that of the w/c = 0.6 (10.5%). The results show that the uplift displacement on the soil surface exhibited certain hysteresis, and the grouting lifting process in sandy soil was divided into three stages: initial deformation, accelerated uplift, and stable uplift.