Fluidised fly-ash cement-bentonite cut-off walls in flood protection

Vertical barrier walls are widely used in environmental control systems to restrict the lateral spreading of liquid or gaseous contaminants and for seepage control through and beneath levees. The barrier walls are constructed in single or two phases using slurry composed mainly of bentonite, cementitious materials and water to maintain the trench stability and finally low hydraulic conductivity of barrier. A turning point in the development of slurry technology arose from research demonstrating the positive effects of blast furnace slag or fly-ashes on slurry properties in terms of reduced hydraulic conductivity. This paper presents the implementation of an experimental section of cut-off wall in the subsoil of a modernised flood embankment along the Vistula River and the results of controlling analyses of applied hardening slurry with an admixture of activated fluidal ashes from hard coal. The results of tests confirm the possibility of practical application of fluidal ashes as active components to hardening slurry and obtaining - depending on the suspension composition - of favourable technological and exploitation properties of this material.