Spatial Variability of Particles in Waste Rock Piles

• Author / Creator

  Barsi, David

• Mine waste rock material has the potential to generate acid rock drainage (ARD) through the oxidation of sulphide minerals. Waste rock is one of the most abundant materials at mine sites that must be managed appropriately to limit the generation of ARD and other harmful by-products; therefore, they need to be well characterized. In order to study the spatial variability in material properties of waste rock, a small scale experimental waste rock pile was deconstructed in 2014. The pile was part of the Test Piles Research Program located at the Diavik Diamond Mine in NWT, Canada. During the deconstruction process bulk samples were collected following a three dimensional grid. These samples were used to measure the particle size distribution (PSD) of the material at discrete locations within the pile. Measurement of the PSD showed that the material was segregated during placement, generally becoming coarser with depth. Further analysis of the PSD showed that the material varied in three dimensional space, creating coarser and finer zones. Therefore spatial distribution of PSD was not just related to elevation. The PSD data represented particles between 0.075 mm and 75 mm, with larger particles not physically measured. Hydraulic properties were also estimated, using a variety of techniques, to predict saturated and unsaturated behaviour in different material types. The measured and estimated data was used to show how the material properties differed throughout the pile. The waste rock material was also classified into six different groupings based on the amount of material finer than 4.75 mm. This classification system divides materials based on their ability to retain water under suction. Approximately 12% of the sampled materials represented rock like material with no capillarity, and 36% represented soil like material with strong capillarity. Over half of the sampled materials showed characteristics that represented the transition between soil like and rock like materials, displaying weak capillarity. Estimation of the hydraulic properties produced reasonable results in most cases. Estimated soil water characteristic curves displayed a reasonable trend in the air entry value as the material changed from fine to coarse. However, this method generated residual saturation values that were larger than expected. Hydraulic conductivity and unsaturated permeability values were also predicted satisfactorily. Saturated hydraulic conductivity values were in a similar range to earlier studies at this site. The classifications allowed for the definition of data ranges for the different material groups. These data sets may be used to improve the understanding of the hydraulic and geochemical behaviour of the material, in previous and ongoing studies at this site. The overall sample and classification methodology may be useful in studying waste rock at other sites as well. Finally, study of the representative elemental volume identified that field sample spacing would need to be much denser in order to recreate a representative model of the pile. Such a sampling program is impractical, and reinforces the need for new data collection techniques that may include remote imaging or geostatistical methods.

• Subjects / Keywords

  • Spatial variablity
  • Waste rock
  • Material classification

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3QJ7896S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.