Introduction of a new bio-based grouting material for underground hydraulic conductivity control
Environmental considerations on underground construction practices render high social demand on environmentally-friendly ground excavation methods and materials. For urban underground development in metropolitan cities, many tunneling projects are facing groundwater problems requiring hydraulic controls such as drainage, shielding, and grouting. Generally, cement or sodium silicate based materials are commonly used in grouting practices. However, cement and chemical based materials have several concerns as groundwater pollution (high pH leakage), washout before hardening. Thus, a new grouting material which quickly hardens and is environmentally harmless is introduced in this study. The engineering performance and feasibility of a microbial biopolymer on soil hydraulic conductivity control are evaluated by a laboratory pressurizedpermeability test setup. Experimental results show the promising potential of gellan gum biopolymer to become a new grouting material for quick setting purposes, due to its immediate gelation rheology induced by temperature variation and pH control. Moreover, the stabilized grout material has no impact on the groundwater quality which ensures its potential as an environmentally-friendly underground construction material.