Assessment of Sample Disturbance in Mine Tailings

Abstract

Obtaining high-quality samples from tailings storage facilities remains a key challenge in tailings engineering. Although samplers such as Dames & Moore and Gel Push have been evaluated for natural soils, their performance in mine tailings remains less documented. This study evaluates the quality of tailings samples recovered using DM, Gel Push, and Shelby samplers at three TSFs, with direct DM-Gel Push comparisons available at one site. The evaluation combines CPTu data, field shear-wave velocity measurements, laboratory index testing, CRS oedometer tests, bender element tests, controlled disturbance tests on reconstituted specimens, and a qualitative scoring scheme based on tube-level condition, extruded specimen condition, X-ray specimen condition, and prepared specimen condition. Commonly used strain-based consolidation criteria, including reconsolidation volumetric strain and normalized void-ratio change, did not separate the imposed disturbance levels in the tested tailings and showed limited agreement with qualitative scores from retrieved samples. In contrast, recompression-based metrics from consolidation tests provided clearer trends and were more consistent with qualitative scores. Thresholds from previous studies did not transfer directly to the tested tailings, indicating that material-specific properties can influence sample-quality criteria. Laboratory-to-field V_s,1 ratios provided an independent assessment that was generally consistent with the consolidation-based and qualitative scores, although material variability within a sample could affect interpretation. For the materials tested, DM and Gel Push samplers generally recovered higher-quality specimens than Shelby tubes, with the DM sampler showing slightly better performance than Gel Push in the available comparisons, although the dataset for such comparisons is limited. Overall, the results support using multiple complementary indicators to evaluate sample quality in mine tailings and emphasize that criteria developed for natural soils should be applied carefully and only as reference values.