Curing Behaviour of Lightly Solidified Clays Monitored with Bender Element and Electrical Conductivity Measurements

Abstract

Soft, weak soils are usually subjected to pre-treatment prior to application in load-bearing to avoid long term stability problems. A similar approach can be adopted for reclaimed land backfilled with dredged marine sediments recovered from the surrounding waters. Pre-treatment like solidification is a time-dependent process, where the improved stiffness over curing or rest period determines how soon the reclaimed land can be utilized. In the present study, a sample of dredged marine sediment was lightly solidified with cement and examined in a large oedometer incorporated with bender element (BE) and electrical conductivity (EC) measuring devices. Comparisons were made with an artificial clay, kaolin. Simultaneous acquisition of BE and EC data enabled real-time monitoring of the improved compressibility of the treated sediment during the 7-day curing period, providing insights to the cementation mechanisms taking place. The measurements revealed the physical and chemical transformation underwent by the treated soil with time, though the results are found to be very much dependent on the soil type. Reported in changes of moisture content (MC), shear wave velocity (Vs) by the BE tests and EC measurements throughout the 7-day curing time lapse, reduction in MC was in general accompanied by a rise in Vs and initial rise followed by decline of EC. The recorded patterns of the parameters with time was mainly attributed to the different soil properties, mineralogy and pore water chemistry inherent in the soil samples examined.