Bentonite-loess slurry for construction of diaphragm walls and bored piles

Abstract

Bentonite fluids are used in narrow excavations in technologies of slurry walls and bored piles. If bentonite is characterised by high liquid limit, production of support fluid with sufficiently high density and accompanying low viscosity is impossible. The aim of the presented research was to verify the usefulness of loess for modification of bentonite slurries. Various bentonite-loess mixtures and suspensions activated with sodium carbonate were tested. It was noted that an addition of loess results in a decrease in liquid limit of the bentonite-loess mixture. Testing of suspensions produced from different bentonite-loess mixtures enabled determination of the optimum sodium carbonate content as well as the minimum bentonite-loess mixture content in the suspension ensuring the required density. The influence of loess content on viscosity and water bleed was then investigated, which enabled determination of loess content range at which suspensions with the required density fulfil also the requirements regarding viscosity and bleed. It was ascertained that an addition of loess enables production of bentonite-loess slurries with adequate properties. Based on the presented results, a patent was obtained and production of bentonite-loess mixture for use in technology of slurry walls was initiated.