Spatial and directional variations in engineering properties of an in situ silicate-grouted sand

In this study, a field sand deposit was grouted with a sodium silicate grout, allowed to cure in situ, excavated, and cut with a water jet into handleable blocks. These blocks were then transported to the laboratory and hand-trimmed or machine-cored to obtain test specimens. The measured permeability, modulus, and strength values for these specimens were used to determine the spatial and directional dependence of these engineering properties in the in situ grouted mass. Then sodium hydroxide was used to dissolve the grout and recover the weight of sand in a given volume, thereby providing an assessment of the grout content and original dry density at particular points in the deposits. Notwithstanding considerable scatter in the data, there were modest indications of anisotropy but no clearly identifiable changes in the engineering properties with distance (up to about 1.6 meters) from the grout injection point. Cored specimens showed little, if any, variations in strength or modulus relative to hand-trimmed specimens, but the strength and modulus of the field-grouted specimens were significantly higher than those of laboratory-prepared specimens using the same grout mix and sands.