Development of a novel base liner material for offshore final disposal sites and the assessment of its hydraulic conductivity.

In the process of landfilling, leachates resulting from the waste landfill are likely to cause secondary environmental pollution, and installation of a basal liner is essential under a landfill site to block and reduce permeation of leachate flowing into the subsurface environment. The research aims to develop a salt-resistant bentonite and a novel base liner material for offshore waste disposal. The liner materials consist of core materials and coating materials in which mixtures of bentonite, sepiolite, and guar gum were used to overcome the shortcomings in bentonite to realise a high water-resistance and a permeability coefficient of below 1.0 × 10-7 cm/s under saline water conditions. The optimal mixing ratio of bentonite, sepiolite, and guar gum was confirmed as 76:19:5 by conducting drying shrinkage cracking tests, free swelling tests, and hydraulic conductivity tests. The hydraulic conductivities of spherical particles, as measured in a rigid-wall permeameter and a flexible-wall permeameter, were less than 1.0 × 10-7 cm/s under saline water conditions. The compressive properties of spherical particles were evaluated through triaxial compression testing. The engineering characteristics of the liner material were studied in the present research, but the long-term biodegradation characteristics of polymer additives were also important, yet remained unclear. The long-term biostability of the additives, and its effect on basal liner performance should be evaluated in future research.