Large-Scale Cutoff Wall Model Test Using Ethanol Bentonite Slurry

In the use of cutoff walls, long-term stability, no gaps, and flexibility to the earth deformation are crucial to minimize the permeability $\left(k\right)$ . Soil–bentonite mixtures meet such requirements, if more than $70\mathrm{kg}$ of bentonite per $1{\mathrm{m}}^3$ of soil could be homogeneously mixed with soil in situ. When making cutoff walls by using the mixing in place method instead of the slurry trench method, bentonite should be added to soil in a slurry state for homogeneous mixing; however, $20\mathrm{kg}∕{\mathrm{m}}^3$ of bentonite would be the largest amount by bentonite–water slurry. To achieve increased bentonite content, the utilization of hydrophilic organic solvent such as ethanol is an effective option. This paper tested a large-scale model to investigate the cutoff property of bentonite wall using ethanol, and to clarify the influence of ethanol to groundwater. The wall had sufficient cutoff ability $(k=4.0\times {10}^{-10}\mathrm{m}∕\mathrm{s})$ , and pumping the groundwater properly could minimize the ethanol diffusion in the subsurface.