Characterisation of the internal friction angle of waste rock material from large triaxial tests using the contact dynamics method

ABSTRACT

The Chilean copper mining industry generates large amounts of waste rock materials. These structures must be designed, operated, and closed considering their physical stability. Although these structures generally do not present physical stability problems, superficial failures may occur, where waste rock material is subjected to low confining pressures. The identification of the internal friction angle, necessary for stability calculations, is based on the characterisation of these materials under high confining pressures. This assumption is not representative of the loading conditions in the superficial layers. To address this issue, numerical large-scale triaxial tests, using the contact dynamics method, are performed to identify the internal friction angle of these materials under low confining pressures. To model these material, irregular polyhedrons were generated using statistical data of crushed aggregates, considering the morphology and the particle size distribution from experimental waste rock materials. The proposed numerical approach was validated by comparing it to literature data for confining pressures over 0.5 MPa. Our results indicate that the internal friction angle stabilises at 39° for confining pressures below 0.1 MPa. This study provides important insights into the physical stability of waste rock dumps and contributes to the development of more accurate stability calculations for these structures.

KEYWORDS:

• Waste rock material
• large triaxial test
• contact dynamics
• internal friction angle

Acknowledgments

This work is dedicated to the memory of Dr. Claude Bacconnet, and the authors express their gratitude for his invaluable assistance in facilitating the exchange programme at the Institute Pascal. This collaborative effort between France and Chile would not have been possible without his support and contributions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data used during the study are available in the following repository online: https://doi.org/10.5281/zenodo.3625778.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/17480930.2024.2367977

Additional information

Funding

This research was funded and supported by the Vice-Rectorate for Research, Creation, and Innovation (VINCI) at Pontificia Universidad Católica de Valparaíso (Chile), through the DI Interdisciplinary Associative Research projects for the period 2023–2024.