Field tests are conducted on permeation grouting of ultra-microfine cement to examine whether zones of improved soil of a sufficient size can be created economically in sand deposits, which would be expected to contribute to improving ground conditions as a countermeasure against soil liquefaction. Four different tests are carried out under different grouting conditions, where grouting is conducted with and without forcible injection pressures, using cement solutions of different concentrations of (w/c) cs = 8 and 12. After two and a half months, the testing site is excavated and the surface appearances of improved soil are confirmed. The study proves that columns of improved soil of diameter 1·5-2 m and height of about 2·5 m can be built up in sand deposits of depth 3 m. Some discussions are given on the filling ratio α and the ratio of mass of water to cement particles (w/c) is of the overall improved soil, leading to the presumption that, as far as relatively clean sand deposits are concerned, the radius of a column of improved soil can be estimated solely from the volume of cement solutions injected into sand deposits. Field testing of permeation grouting using microfine cement Hashimoto, Nishihara, Oji et al. Notation

The development of ground improvement technology by means of permeation grouting using recently developed ultra microfine cement has been underway by the authors' group, especially for mitigating effects of soil liquefaction on existing structures built on liquefiable soil deposits. From the experiences gained from the field tests carried out at the different two sites, this method works well for relatively clean fine sand deposits, though it may still need some refinement for silty sand deposits. Some supplementary methods assisting permeation of cement solutions through silty sand deposits were pursued based on laboratory permeation tests, and one method was found promising. This method employs the injection of water, following infiltration of relatively dense cement solutions which would be terminated by cement particles trapped within micro-scaled silty sand skeletons. In the present study, a series of laboratory one-dimensional permeation tests are conducted to examine this supplementary method in more detail, especially from the viewpoint of cost-effectiveness and performance.

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