Steps to Increase the Reproducibility of Geotechnical Laboratory Test Data

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal

Centrifuge modelling of seepage through tailings embankments

Tailings storage facilities (TSFs) are manmade geotechnical structures usually comprising a perimeter embankment, fill material (the tailings) and a water-level control system. The key issues often raised in TSF operation are uncertainties surrounding likely seepage to the environment and accurate prediction of seepage surfaces for input into stability assessment. Critically, TSFs are much more complex than the current numerical models conventionally assumed. This paper presents techniques for investigating steady-state and drawdown seepage behaviour of TSF embankments using a fixed-beam geotechnical centrifuge. The development of experimental equipment for centrifuge testing is described and novel methods to characterise model materials preliminarily, using a ‘desktop’ centrifuge, is presented. Good agreement is found between experimental results from the fixed-beam centrifuge and those predicted by the GeoStudio SEEP/W software package for steady-state and drawdown conditions at all tested hydraulic gradients. </jats:p

The influences of partial saturation on cone penetration tests in silty gold tailings

Laboratory-controlled cone penetration test results of a silty gold tailings in a variety of saturated and unsaturated states, obtained using two calibration chambers, are presented then interpreted using a state parameter-based approach. The research was conducted as part of the TAILLIQ project (tailliq.com), funded by the Australian Research Council and six mining companies, and involving four Australian universities.Cone penetration resistances, which increase due to the presence of suction when the tailings are unsaturated, can be normalised using the initial mean effective stress to establish a relationship with the initial state parameter. The relationship is applicable to saturated and unsaturated conditions, as long as the presence of suction hardening as well as the influence of suction on the mean effective stress are accounted for, and as long as the cone penetrations occur under pseudo drained conditions. The relationships enable state parameters and void ratios to be back-calculated from normalised cone penetration resistances

Resensies

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A Narrow Wall System to Capture Temperature-Stress-Strain Behavior in Paste Backfill

Placing mine tailings back underground, into mined-out stopes, is becoming increasingly used internationally, providing as it does improve ore recovery, reduced dilution of valuable ore and environmental benefits due to reduced size of surface tailings storage facilities. In recent years a number of stopes backfilled with cemented paste backfill have been instrumented with load cells and piezometers, to improve our understanding of in-situ behavior. Many of these studies have reported results that show increases in measured total stresses when there is no increase in applied load, i.e. even when the backfilling process is long completed. One explanation is that these stress increases result from expansive volume changes of the backfill as it hydrates and generates heat. This paper proposes and describes a novel laboratory apparatus called narrow wall system to investigate this hypothesis, focusing on modeling narrow stopes as these are relatively common in backfill applications. Results from the experiments agree qualitatively with the reported field observations, showing clear increases in measured pressure during periods of temperature increase. The paper concludes that the proposed narrow wall system works effectively and has been able to capture the temperature-stress-strain behavior of paste backfill. Thus, the temperature effect hypothesis has now been supported by evidences. Using the system, further studies related to geometrical or scale effects are suggested. The results are important for academics and engineer to improve backfill design in mining operations