Interpretation of field tests using geo-statistics and Kriging to assess the deep vibratory compaction of the Dike A21, Diavik Diamond Mine

Abstract

AbstractThis article presents an interpretation and statistical analysis of heavy dynamic probing (DPH) tests carried out on the compacted core of Dike A21, of the Diavik Diamond Mine. Due to the inhomogeneous and inherently random nature of soil and the uncertainties associated with even well controlled field tests such as DPH tests, the evaluation of in situ properties (such as density) should take into consideration the natural variability of the soil. Aided by the large amount of relatively concentrated field data, this paper presents a methodology for not only evaluating the field tests statistically through Kriging, but also for judging the compaction effort, taking into consideration the variability. This paper documents the necessary normalization procedure, analyzing a number of external factors such as the temperature, time since compaction (aging) and the presence of nearby works that may affect the field data. It was shown that the appraisal of soil improvement measures should consider the presence of natural and unavoidable fluctuations of the fill material. The Kriging estimate combined with an averaging procedure and subsequent comparison with the expected variability, quantified by the variogram, was applied which enabled the assessment of areas with insufficient compaction. Additionally, the influence of aging of the fill was demonstrated, where a clear increase in the DPH tests between 0 and 14 days since compaction was observed. It was also found that over-compaction leads typically to a lower relative density. The authors note that this statistical analysis was performed following the control and acceptance of the compaction of the dike and as such had no impact on the acceptance of the dike construction.