Injection and distribution of silicate grout in sand

A laboratory model study to relate the effects of grout composition, silicate concentration, dilution, viscosity, temperature, and mechanical agitation to the actual pumping of the grout into the soil mass is described. Three experimental models, each with a different geometry, were studied: the basic difference between these models is the rate at which the grout front advances as the grout is injected at a constant flow rate. The magnitude and distribution of the pore fluid pressures developed during the grout injection process were measured, and the results indicate a very rapid decrease in pore fluid pressure with distance from the injection point. The strength and modulus of the grouted soil mass showed a tendency to decrease with distance from the injection point. Upon injection, the grout appears to flow progressively into the soil, with the fresher grout displacing the older grout toward the exterior of the grounded mass. There was no conclusive evidence of soil fracturing due to grout gelation in any of the tests.