An Alternative To Traditional Phase-Based Optimisation Tools

For decades, strategic mine planning has been influenced by the limitations of traditional pit optimisation methods. The Lerchs–Grossmann (LG) and Pseudoflow algorithms have long been the primary tools for defining ultimate pit limits. These methods have formed the backbone of downstream planning, guiding phase design, scheduling, and ultimately how project value is realised.

The initial step in this process is crucial. Well-defined phases can significantly enhance Net Present Value (NPV), while poorly defined phases can result in years of inefficiency. However, LG and Pseudoflow address only two of the three key strategic questions: which blocks to mine and where to send them. They do not address when to mine these blocks.

These algorithms were designed to identify economically viable shells at a fixed price, aiming to maximise cash flow rather than discounted value. By not considering timing or operational constraints, they tend to favour high-grade, low-strip material, prioritising short-term gains over long-term value. Transforming these shells into actionable schedules requires manual interpretation by engineers, which introduces subjectivity and can lead to deviations from the optimal plan.

In summary, traditional pit optimisation defines the shape of value but not its timing. It produces a static, price-driven geometry that must later be adapted to real-world conditions. Deswik GO, powered by Direct Block Scheduling (DBS), redefines this process. It simultaneously addresses space, destination, and time, delivering a single, time-aware optimisation that directly maximises NPV and aligns with operational realities.

The limitation of nested shells

Traditional mine schedule optimisation tools typically rely on pre-designed pit phases as their primary input. These phases are often derived from nested revenue shells that serve as the structural foundation for scheduling. The optimisation process then seeks to determine the best sequence for extracting these phases, subject to constraints such as mining rates, processing capacities, and blending requirements.

While this approach can be effective for scheduling, it is inherently constrained by the initial phase designs. The spatial evolution of the pit and the direction of mining are largely predetermined before optimisation begins. As a result, the software can only optimise within the boundaries imposed by those phase designs, it cannot fundamentally redefine the mining sequence to unlock additional value.

This limitation becomes particularly evident when the phase designs are misaligned with operational constraints or economic priorities. For example, if a high-grade zone is included in an early phase but cannot be processed due to timing or capacity constraints, the material may be wasted or stockpiled inefficiently. The optimisation tool, bound by the phase geometry, lacks the flexibility to adjust the sequence in response to such challenges.

This is a preview of an article that was originally published in the Jan/Feb 2026 issue of Global Mining Review. Subscribe to Global Mining Review for free to read this article in full and many more here.

Read the article online at: https://www.globalminingreview.com/special-reports/18022026/an-alternative-to-traditional-phase-based-optimisation-tools/