2014 Volume 70 Issue 4 Pages 387-394
The improved strength by the permeation grouting is reported to be influenced by soil density, grain-size distribution, grouting concentration, age of improved soil and so on. The strength of improved soil varies in wider ranges compared with that created by the Deep Mixing Method. In this study, the mechanism of strength variation of treated sand was theoretically and experimentally investigated. The advection-dispersion equation was used for analyzing the dilution of injected grout which would reflect the strength variation of improved sand. In addition, model injection tests and field test were carried out to clarify the causes of variety in strength of improved sand. The result reveals that the main cause of strength deviation of sand improved by permeation grouting can not be attributed to dilution of injected grout due to diffusion, but can be attributed to the submergence of grouting material, which is caused by the difference of density between pore water and injected chemical grout, after finishing injection and solidification process.