Assessment of Leach Ore Dry Unit Weight and Hydraulic Performance

Assessment of Leach Ore Dry Unit Weight and Hydraulic Performance

Author: Peter D. Duryea
Conference: Tailings and Mine Waste 2019
Date: November 17-20, 2019

Proper design of a heap leach facility requires the development of a leach ore loading plan that can accommodate its ultimate capacity. The loading plan and associated capacity assessments will be more representative of actual field performance if they consider the variation in leach ore dry unit weight over time as the heap is loaded and the leach ore compresses under self-weight. That can be accomplished by careful evaluation of results from laboratory testing of representative samples of the leach ore.

Rigid wall permeability testing provides data about dry unit weight (and hence void ratio), saturated hydraulic conductivity, and vertical effective confining stress. These data can be fitted to relationships for compressibility (void ratio as a function of effective confining stress) and conductivity (saturated hydraulic conductivity as a function of void ratio) that were originally developed for self-weight consolidation of soft, fine-grained soils, e.g., tailings. The forms of those equations also typically fit laboratory test data from coarse-grained leach ore.

Once the compressibility and conductivity relationships are defined, incremental stress calculations with a spreadsheet allow for the development of: (1) profiles of dry unit weight and saturated hydraulic conductivity with depth in a unit area column of leach ore; and (2) the variation in depth-weighted average dry unit weight with average heap height. The average dry unit weight relationship may then be incorporated into heap loading plans and capacity assessments. Comparison of the planned leach application rate to the anticipated saturated hydraulic conductivity of the leach ore under the maximum heap height, assuming vertical percolation under unit hydraulic gradient, also provides a preliminary assessment of hydraulic performance.

Results for two case studies, including both a crushed and agglomerated copper heap and a run-of-mine gold heap, are presented. Actual results from mine production records compare well with predictions, although assessment of the run-of-mine gold heap required additional refinement to adjust for the effects of oversize material that could not be incorporated into the laboratory-scale testing.

 

Download the full technical paper.

Download

Recent Insights

April 2024
Risk Mitigation through Design Optimization Utilizing Seasonal Effects under Arctic Conditions at the Amaruq Mine
April 2024
Synthetic Rock Mass Modeling of Progressive Unravelling and Overall Slope Stability Using the Discrete Element Method
April 2024
Operational Slope Stability Risk Management for Large Open Pits at the Mount Milligan Mine – A Case Study
April 2024
Risk and Informed Approach to TSF Design and Operation
February 2024
Empowerment and Resilience
January 2024
Balancing Act: Water Usage Management Vital for a Sustainable Future
January 2024
A Difficult Balance Between Engineering, Environmental, Social and Economic Aspects
November 2023
Knight Piésold Commences with the ESIA for Haib Copper
November 2023
Insights from the Compilation and Critical Assessment of Breach and Runout Characteristics from Historical Tailings Dam Failures: Implications for Numerical Modelling
November 2023
Earthquake-induced Deformation Analysis of a TSF Undergoing Tailings Reprocessing
November 2023
Case Study: Approach to Determining the Risk Mitigation Priority of a Historic TSF in North America
October 2023
Data Management and Insights for Effective Tailings Storage Facility Management
October 2023
The Role of Sensitivity Analysis in Selecting Dam Breach Parameters
October 2023
Influence of Increased Confining Stress on Undrained Behavior of Tailings: A Case History at the Candelaria Mine
October 2023
The Re-use of Existing Bituminous Stabilised Materials for the Rehabilitation of National Route 7 - Case Study
September 2023
Transición energética para gerentes de mina
August 2023
Interview: Guillermo Barreda, Gerente General, Knight Piésold Perú
July 2023
Selection of Soil Shear Strength Parameters Based on Integrated In Situ Tests, Lab Tests and Numerical Calibration Approach
June 2023
Leveraging Knowledge and Experience of a Well-Formed Independent Tailings Review Board to Enhance Tailings Facility Safety
May 2023
Is the Implementation of Dry Stacking for Tailings Storage Increasing? A Southern African Perspective