ACALA

Geological Expertise, Mining Excellence

Featured topic · Open pit mining

An open pit is a long-term plan meeting a short-term reality, every single day.

Surface mines run on two connected plans: a strategic plan that covers the life of mine, and a tactical plan that turns it into this month’s schedule. This page collects what ACALA has learned about keeping the two honest with each other, and the GEOVIA tools, services and articles that help.

Start with the reading
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Grade-tonnage curve: tonnes above cut-off fall and mean grade rises as the cut-off grade increases tonnes above cut-off (Mt) mean grade above cut-off (% Ni) 0.6cut-off grade (% Ni)2.0 cut-off 1.10 % Ni · 42.0 Mt at 1.48 % Ni
Grade-tonnage curve for a laterite nickel resource. Drag the cut-off to see how much ore you keep, and at what grade.
Strategic planLife-of-mine pit shapes, pushbacks, plant, stockpiles, dumps.
Tactical planWeekly to yearly schedules that meet blend and ratio targets.
Cut-off gradeThe grade below which a block is waste; the most powerful lever a planner has.
PushbackA practical phase of the pit, mined in sequence to bring value forward.
Strip ratioWaste moved per tonne of ore; the cost the schedule has to carry.
ReclamationReturning the pit and dumps to a usable landform after mining.
Panorama of a benched open pit
An open pit is a long-term plan meeting a short-term reality, every day. Image from the GEOVIA brochure distributed by ACALA.

The idea

Two plans, one orebody, and the forces that pull them apart.

A widening band of simulated outcomes over the life of mine, with the traditional single fixed value drawn as a dashed line inside it, and orebody findings, technical advances and the market arriving as arrows from abovePLANNED AS A RANGE, NOT A LINEorebody findingstechnical advancesmarketfixed valuesimulated rangeyear 1life of minea range the plan can absorb, not a single value it breaks on

Strategic mine plan

Long-term, and exposed to everything

Covers the whole life of mine: pit shapes, pushback sequence, plant configuration, stockpile and dumping requirements. Because it is long-term, it is affected by new findings about the orebody, technical advances, and changes in the economy or the market.

GEOVIA’s strategic tools let planners simulate geo-mechanical rock behaviour and build risk assessment into each step, by adding uncontrolled variables such as noise around a traditionally fixed value. That is how a plan absorbs surprises instead of breaking on them.

Strategic mine planning solution
A dashed long-term path with the short-term schedule drawn as steps beneath it, dipping in red where conditions change and corrected back onto the pathKEEPING THE MINE ON THE PATHlong-term planconditions changeone repository: topography, pit design, scheduling parametersthe short-term answer that keeps the long-term plan true

Tactical mine plan

Short-term, and the only one operations see

Turns the strategic decisions into a schedule that governs day-to-day operations. It is the calculated, short-term response that keeps the mine on the path of the long-term plan when conditions change.

A central repository for topography, pit design and scheduling parameters, plus blending algorithms that choose which blocks are mined and when, produce as many short and long-term schedule iterations as the situation demands.

Tactical mine planning solution

Where value is decided

Three decisions that move the number more than any other.

Cut-off and the ultimate pit

Optimise the pit for value, not for size. The largest shell is rarely the best one; the curve above shows why the cut-off changes both tonnes and grade at once.

Optimize vs maximize

Pushback sequence

Bringing higher-value material forward is worth more than any single design change, as long as the practical phases can actually be mined in that order.

Mine design solution

Blend and strip ratio

The schedule that meets the plant’s quality targets while keeping waste movement flat is the one operations can keep to. Blending algorithms make that a calculation, not a hope.

MineSched

How ACALA helps

Tools, hands, or training. The topic page shows all three.

Every featured topic maps to the GEOVIA products that address it, the ACALA service that does the work, and the course that teaches it.

Reading on this topic

What our planners have written about open pits.

Other topics

Five more topics, and the four disciplines behind them.

Questions people ask

Open pit mining FAQ

What is an open pit, open-cast or open-cut mine?
Three names for the same surface mining method: excavating a pit from the surface to reach minerals or ore in shallow deposits, bench by bench, rather than tunnelling underground. Gold, nickel laterite, coal and phosphate are common examples in Indonesia.
What are the steps of surface mining?
Exploration and evaluation through geological surveys and drilling; removal of overburden to expose the deposit; extraction with heavy equipment; and reclamation, recontouring the land and replanting after mining.
Is open pit mining safer than underground?
Generally yes: work is at the surface, air quality and evacuation are simpler, and there are no confined spaces or cave-in risks. It has its own hazards, slope stability above all, which is why geotechnical limits belong inside the design.
What are the advantages compared with other methods?
Lower operating cost per tonne, higher recovery from large shallow deposits, and simpler logistics. The trade-off is a larger footprint and more waste to move, which is what strip ratio and reclamation planning manage.
Do open pits get filled back in?
Often, yes. Backfilling and reshaping dumps into a final landform is part of reclamation after mining ends, returning the land to agriculture, forestry or recreation. Planning the landform with the schedule keeps that cost real from the start.

Next step

Bring your block model. We will show you the cut-off that pays.

A working session in Whittle on your own data answers the strategic questions faster than another spreadsheet.

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