A new method for producing uniform, loose, initially unsaturated specimens

Abstract

Moist tamping (MT) forms the most common method for the reconstitution of predominately sand tailings, largely owing to its ability to produce loose specimens without segregation. However, MT has been subject to considerable criticism for not producing a fabric like hydraulically placed sands or tailings and owing to non-uniform initial internal density profile. Alternatively, given the increased implementation of filtered tailings stacks, MT is commonly applied to characterise such materials owing to the initial unsaturated and sometimes loose state achievable, while still suffering from potential issues from non-uniformity. To enable the advantages of MT to be realised while also achieving high initial sample uniformity, and therefore tests that can be treated as an element, a new method referred to as moist vibration (MV) is proposed. This method involves preparation of a sample in a tube with vibration used to densify and increase uniformity, prior to extrusion and trimming for testing. Assessments carried out on two soils demonstrated that high uniformity is achieved with the new method. Finally, comparison of MT and MV samples by means of undrained shearing shows no discernible difference in the results for a sand and only subtle differences in a clay-sand mixture.