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On the merits of modified sublevel caving mining method – a case study

Adams Kenneth K., Chen Tuo, Sainoki Atsushi, Mitri Hani S.

Archives of Mining Sciences

2023

Vol. 68, no. 4

543--569

Sublevel caving (SLC) mining method has several features that make it one of the preferred methods for ore extraction due to its high productivity and early access to ore recovery. However, there are some major challenges associated with the SLC method such as ground surface subsidence, high unplanned ore dilution, and the potential for air blast. To remedy these shortcomings, a recent approach has been to modify the SLC method by introducing rockfill into the void atop the production zone to provide continued support for the host rock and prevent it from caving. This paper discusses in detail the merits of the Modified SLC or MSLC. In comparison with other long-hole stoping methods that are predominantly practiced in metal mines, the MSLC method boasts several advantages. Early production achieved from the topmost level helps reduce the payback period. Productivity is enhanced due to multilevel mining without the use of sill pillars. The cost of backfilling is significantly reduced as there is no need for the construction of costly backfill plants. Continuous stoping is achieved without delays as mining and backfilling take place concurrently from separate mining horizons. A significant reduction in underground development costs is achieved as fewer slot raises and crosscuts are required for stope preparation. These merits of the Modified SLC method in steeply dipping orebodies are discussed by way of reference to real-life mine case studies. Dilution issues are addressed, and the benefits of top-down mining are explained. Typical mine design, ventilation, materials handling, and mining schedules are presented. Geomechanics issues associated with different in-situ stress environments are discussed and illustrated with simplified mine-wide 3D numerical modeling study.

Effect of mining and geology on mining-induced seismicity – a case study

Khalil Heba, Chen Tuo, Xu Yu-Hang, Mitri Hani

Journal of Sustainable Mining

2022

Vol. 21, iss. 3

200--215

Mining-induced seismicity is a commonly occurring phenomenon in underground mines. This poses a greater challenge to the safety of the mining operation. This paper presents a case study of the Young-Davidson mine in northern Ontario, Canada, where seismic events of magnitude Mn 2.0+ have been observed at mining depths of 600 to 800 m below the surface. The occurrence of large seismic events at such shallow depths is the key issue of this study. A comprehensive study of the microseismic database has been conducted to discern the root causes for the unusually strong seismic activities recorded at shallow depths. The effects of mining activities in the vicinity of two dykes intersecting the orebody on the seismic response are investigated. Variation of the b-value derived from the magnitude-frequency distribution is examined, and moment tensor inversion for three large seismic events is carried out to determine the source mechanisms. It is shown from this investigation that the influence of the sill pillar is more critical, leading to high mining-induced stress and the occurrence of large events. While the findings from this research are specific to this case study, they could be used to shed light on the causes of induced seismicity at other mines with similar conditions.