Results of a critical state line testing round robin programme

A critical state testing round robin programme was carried out on sandy silt gold tailings. This involved 15 laboratories around the world testing a sandy silt tailings to infer its critical state line (CSL). Methods to be used were intentionally not supplied to participants, to enable the current methods being employed in industry and academia to be obtained in an unbiased manner. All but one of the laboratories involved in the study used the moist tamping sample preparation technique, generally to produce loose, contractive specimens. Void ratio was measured using a variety of means, including cell calibration, end-of-test water content and end-of-test soil freezing (EOTSF) to assist in measuring the final water content. Of the 15 entries, four were excluded from the primary comparison owing to various issues that appear to have led to their divergence from most of the entries received. Of the remaining entries, the best reproducibility was produced by laboratories that used EOTSF to measure void ratio. Most other test procedure variations appeared to have a negligible effect, with the exception of fixing of the top platen and possibly sample size. A CSL elevation range of 0.04 void ratio for laboratories using EOTSF was observed.

Automated summary

A critical state testing round robin programme was conducted on sandy silt gold tailings by 15 laboratories globally. The study found that laboratories using EOTSF to measure void ratio showed the best reproducibility, while most other test procedure variations had little effect on the results. The elevation range of CSL was observed to be 0.04 void ratio for laboratories using EOTSF.