Abstract:

Tailings Dam Breach Analysis (TDBA) serves as an essential tool for the safe management of the Tailings Storage Facility (TSF). The general objectives of the TDBA are to assess the dam consequences classification and emergency preparedness and response plan. During the life cycle of a TSF, the consequences of dam failure could vary due to the changes in dynamic site conditions.

This paper presents a TDBA case study for an operational TSF under current, and future conditions in the next five years based on the tailings deposition and water management planning at an operating mine in Canada.

Based on the review of the site history, geotechnical information, risk registry and previous dam breach and inundation study reports, the combination of operational upset and long-duration extreme storm event triggering overtopping was considered the Flood-induced credible failure mode. In contrast, artesian pore pressures triggered slope failure and were selected as a fair-weather credible failure mode for the TDBA scenarios.

A probabilistic breach modelling approach was taken to estimate the range of peak flows and breach hydrographs by considering the uncertainties of the dam failure characteristics. The ranges of dam breach duration time, breach width and breach side slopes were input in a breach modelling program, and a Monte Carlo simulation was carried out to estimate the breach peak flow distribution and hydrographs. The hydrodynamic model that simulates flow-type transition was utilized to route the breach flow runout processes.

The inundation modelling results were input for the Population at Risk (PAR) and Potential Loss of Life (PLL) assessment. The results indicated that the PAR/PLL decreases with the TSF water management plan in the next five years.

These TDBA results can assist the EOR in refining the risk assessment matrix for the TSF under different operational conditions and help the dam owner allocate appropriate effort for emergency preparedness and response plan.

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Mr. Michael Louws