Ultrasonic interrogation of a clayey tailings during sedimentation–consolidation

Ultrasonic methods are used for non-destructive detection of changes of low-strain properties in concrete, soils, and other materials. This paper presents the use of ultrasonics to detect density and structure changes in a soft clayey tailings. Such tailings undergo sedimentation and consolidation following their deposition, which may occur simultaneously with flocculation and other fabric-altering processes, resulting in time-dependent consolidation characteristics. Here we attempt to measure structural changes in the clayey tailings using ultrasonics, which presents several challenges due to the material’s relative softness. Ultrasonics testing was attempted using a special 3D printed column with height and diameter of 540 and 110 mm, respectively. Specially fabricated sample holders were designed to repeatedly ensure proper connections of compression (P-wave) and shear (S-wave) wave transducers. The arrival time corresponding to the largest P-wave amplitude showed a strong correlation with density of the tailings, while a specific frequency bandwidth of the P-wave spectra indicates an increase in wave amplitude (signal energy) occurring subsequent to most of the volume change. Ultrasonic measurements appear to be a promising technique to monitor density and stiffness in soft clays, tailings, and similar soft sediments.