HGS RESEARCH HIGHLIGHT – A black-box automated approach to calibrate numerical simulations and optimize cover design: Application to a flow control layer constructed on an experimental waste rock pile
Crouzal, T., & Pabst, T. (2021). A black‐box automated approach to calibrate numerical simulations and optimize cover design: Application to a flow control layer constructed on an experimental waste rock pile. In Vadose Zone Journal (Vol. 20, Issue 3). Wiley. https://doi.org/10.1002/vzj2.20130
“the calculations were faster by using the parallelization option in HGS software”
Fig. 5. Measured (dashed lines) and calibrated (solid lines) water retention curves of the waste rock (blue), flow control layer (FCL) sand (green), and crushed anorthosite (red) in the experimental waste rock pile (Bréard Lanoix et al., 2020; Dubuc, 2018)
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In this study, researchers developed and tested a novel black-box automated approach to calibrate numerical simulations and optimize cover designs for waste rock piles at mining sites. This work was undertaken by a team of scientists focusing on improving waste rock pile stability and minimizing environmental contamination.
The researchers targeted the challenge of water infiltration in waste rock piles, which can compromise stability and lead to contamination. They constructed an experimental waste rock pile at the Tio mine in Canada and integrated a flow control layer (FCL) made of crushed waste rock or sand. Large infiltration tests and rainfall monitoring provided the necessary data for their analysis.
Given the noisy and incomplete nature of the field data, an automated calibration approach was crucial. The team developed an algorithm using a black-box method to solve an optimization problem without relying on an analytical form. This approach allowed for accurate calibration and optimization of the FCL design, considering material properties and layer thickness tailored to local climatic conditions.
The study utilized HydroGeoSphere (HGS), a cutting-edge modelling platform, to simulate water flow and optimize the FCL design. HGS allowed for detailed numerical simulations based on extensive field data, including large-scale infiltration tests and two years of rainfall monitoring. The researchers also utilized HGS’s parallelization capabilities to manage model runtimes.
Abstract:
Mining operations often produce large volumes of waste rock to access economically valuable mineralized zones. Waste rock is usually stored in surface piles, the construction and reclamation of which represent a challenge for the industry. A flow control layer (FCL) made of crushed waste rock or sand and constructed on top of each waste rock bench could contribute to control water infiltration, thus improving waste rock pile stability and limiting contamination. An experimental waste rock pile was built and instrumented at the Tio mine (Rio Tinto Fer et Titane, Canada) to evaluate the performance of an FCL in field conditions. Large infiltration tests and rainfall monitoring were carried out, and measured outflow and water contents were used to calibrate numerical simulations. However, data were noisy and sometimes incomplete, and the models were difficult to calibrate. A new automated calibration approach was therefore proposed. An algorithm was developed to automate the numerical simulation calibration, using a black-box method that involves solving an optimization problem on a function without an analytic form. The approach was applied on measurements obtained from large-scale infiltration tests and validated using 2 yr of field monitoring data. Finally, the automated approach was adapted to optimize the design of the FCL, and an optimal design (material properties and layer thickness) was recommended based on local climate conditions. The proposed automated method could contribute to reduce the bias induced by manual calibration and allows for rapid multivariable calibration and optimization for a broad spectrum of mine waste cover system applications.