Cemented paste backfill strength profiles for continuous pouring and liquefaction resistance

Grabinsky, Murray; Thompson, Benjamin; Veenstra, Ryan

doi:10.36487/acg_repo/2355_19

Cited by 1 publication

(1 citation statement)

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“…The continuous pour strategy typically assumes the paste in the initial plug region has gained strength sufficiently quickly so that barricade pressures peak before the plug pour is completed, or where pressure thresholds at the barricade are not exceeded during subsequent backfilling. Grabinsky et al (2021Grabinsky et al ( , 2023 presented an analysis approach whereby an initial plug strength condition must be met and, subsequently, the strength gain in the plug must increase more rapidly than the incremental loading increase during the continued pour. Barricade pressures during continuous pours should be measured to ensure a safe loading range is maintained.…”

Section: Introductionmentioning

confidence: 99%

Best practices in continuously (or not continuously) pouring paste backfill

Thompson¹,

Veenstra²,

Carmichael³

et al. 2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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Cemented paste is established as a widely used backfill material. Mines using this type of backfill initially use conservative pouring strategies whereby a 'plug' is poured to a height exceeding the (containment) barricade and brow. The plug is allowed to cure to an extent that the remainder of the stope can be poured without inducing significant additional pressure on the barricade. In the last decade, more mines are applying engineering principles including engineered barricade designs, barricade pressure monitoring, specific backfill plug strength designs, and quality assurance/quality control (QA/QC) plant-based protocols to evaluate and verify how the efficiency of backfill placement can be safely optimised.There are several examples within the literature where mines have demonstrated how continuous backfilling can be safely adopted into their respective standard operating procedures. There is, however, an absence of published field data for cases where high or inconsistently low pressures at barricades limit the advisability of continuous pouring. This can create a bias in expectations. We present case study data from mines where a range of barricade pressures leads to, at best, an unproven justification for continuous pouring. Risk profiles are heightened if non-ideal conditions exist (i.e. non-engineered barricades, new operations lacking in site-specific experience). Emphasis on the continual process of safely optimising backfilling efficiency is more helpful than a focus on the potential end result of continuous pouring. Indeed, we cite cases where operations have reverted to more conservative strategies when better appreciation of the risks of continuous pouring evolve with time or changing conditions.We have previously recommended initially collecting 'baseline' data to assess the range of barricade pressures under normal operating conditions, prior to a recommendation for continuous pour trials. This paper emphasises that although collection of baseline data can be time consuming, given the consequences of barricade failure, it is a necessary task to adequately define risks.As technology allows the more widespread use of instrumentation to fulfil previous 'use barricade pressure data to verify safe and efficient backfilling' recommendations, it is important to step back and review best practice approaches and, indeed, the context of when it is feasible and when it is not feasible for continuously backfilling or accelerated backfilling to be adopted. Critically, we emphasise that instrumentation is only part of the solution to ensure safe backfilling. Definition of adequate plug strength, proven by QA/QC in terms of early age strength testing, adequate barricade designs and potentially personnel exclusion zones are also necessary.

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Section: Introductionmentioning

confidence: 99%