2016 年 65 巻 1 号 p. 2-5
For in-situ containment, the conventional techniques such as soil-cement walls or steel sheet pile walls are utilized to vertical cut-off wall installed around contaminated sites or illegal waste dumping sites, to prevent contaminants transport to aquifer. However, when subsurface waste or special stratum exists at the place of soil-cement walls constructing, the quality of soil-cement for hydraulic barrier may not be provided. In such a case, the construction process of soil-cement wall is thought that the ground is excavated with casing tube (by all-casing method) in order to take out wastes and wrong soils, and after that, soil-cement placement and casing tube removal is carried out. Vertical cut-off wall with continuous overlapped soil-cement columns can be built by repeating this cycle. We investigated mixture proportion of soil-cement with high density, high liquidity and high quality for hydraulic barrier material of vertical cut-off wall. As a result, applying the high liquefied soil-cement technique which we developed in the past, high liquefied and no separation soil-cement based on sand and bentonite was realized, and high compressive strength excess 1N/mm2 and low hydraulic conductivity range from 10-8 to 10-9 cm/s were obtained.