Swell and compressibility characteristics of sand--bentonite mixtures inundated with liquids

摘要

The swell behavior of expansive soils may be desirable as in many hydraulic containment applications or unfavourable and may cause major deterioration and distresses in many geotechnical applications such as highways and shallow foundations on expansive formations. In this study, the role of liquid chemistry on the swell and compressibility characteristics is investigated. Two types of bentonites are mixed with pure silica sand. Mixtures of 20/100 bentonite are compacted to l8 kN m~-3 dry density at 8/100 water content. Swell and compressibility are evaluated by oedometer test using various concentrations (0.0, 0.l, 0.5, l.0, 4.0 N) of Ca(NO_3)_2 and NaNO_3. Results indicate that swell potential (SP), swell time, swell pressure, and volume compressibility decreases with increase of chemical concentrations for the two types of mixtures. Therefore, degradation in the efficiency of high quality bentonite (HQB) in containment applications should be considered. Pr-wetting or grouting with NaNO_3 and Ca(NO_3)_2 concentrations (0.5--l N) could be practical alternative to control swell in foundation and highway engineering.