Application of biopolymer hydrogel for ground hydraulic conductivity control under pressurized conditions

Abstract

The use of hydraulic barriers to control the water leakage and flow into underground structures such as tunnels has become a common method in geotechnical engineering practice. There are different types of materials used for hydraulic conductivity control purposes such as soil-bentonite and cementbentonite mixtures, and chemical admixtures including asphalt, sodium silicate and so on. Underground hydraulic barrier materials are required to well-resist against the in-situ earth pressure and hydrostatic water pressure. In this study, a gel–type polysaccharide biopolymer gellan gum–has been used to reduce the hydraulic conductivity of sand. It results from the fact that gellan gum biopolymer forms high viscous hydrogel once thermo-gelated, which is expected to have a high structural resistance even at high external pressure conditions. Therefore, the hydraulic conductivity of gellan gum-treated sand is assessed with vertical confinement and water pressure increase. It is interesting to observe that the hydraulic conductivity of sand exponentially decreases with gellan gum content.