Laboratory study of the pressurized grouting in sand

Pressurized grouting technology has been widely adopted in ground improvement. In this study, a series small-scale laboratory pressurized grouting tests were conducted on loose sand under confined conditions, the effects of injection pressure, grout water/cement ratio and degree of saturation of soil (water content) were considered. By comparison of the injected grout quantity and the characteristics (shape and size) of grouted bulbs obtained two main different processes are found to be involved during pressure grouting process, i.e. densification by compaction grouting or fracturing by the injected grout. At a lower water/cement ratio of 0.5, spherical grout bulbs are generally obtained in the tested grouting pressure range and the compaction effect is prevalent; while, at a higher water/cement ratio of 1, the fracture starts to occur at a low grouting pressure, inducing a relative thin grout structure. It is also observed that more grout is injected at higher water/cement ratio due to the appearance of fractures. Regarding to the soil property, the degree of saturation (Sr) plays a significant role in the grout bulbs generation and development in relation to the soil water characteristics. With the Srincrease from 5 %, the mass of injected grout decreases followed by an increase after a threshold value of about 40%; on the other hand, compaction grouting seems to be dominant at the threshold Srvalue, while factures tend to appear at both lower and higher degree of saturation.