🎓 Lesson 1
D1
Introduction to Mine Planning & Scheduling
Mine planning and scheduling is the process of deciding what, where, when, and how much to mine—and in what order—to safely and profitably extract resources over time.
🎯 Learning Objectives
- ✓ Analyze a block model to calculate ore/waste tonnage within a defined pit shell
- ✓ Design a 12-month production schedule using precedence constraints and equipment fleet capacity
- ✓ Explain the trade-offs between NPV optimization and operational flexibility in long-term scheduling
- ✓ Apply critical path method (CPM) to identify bottlenecks in a development sequence
- ✓ Evaluate schedule robustness using Monte Carlo simulation inputs for grade and dilution uncertainty
📖 Why This Matters
Every dollar spent on drilling, blasting, hauling, or processing is only justified if it’s part of a coherent, timed plan. Poor planning leads to stranded equipment, missed targets, cost overruns, and even safety incidents—such as premature wall failures due to unbalanced bench sequencing. In 2022, McKinsey reported that top-quartile mines achieve 15–20% higher NPV through disciplined, integrated planning—proving this isn’t just paperwork: it’s the backbone of mine value creation.
📘 Core Principles
Mine planning operates across three hierarchical levels: strategic (10–30 year life-of-mine plan, focused on pit shells, infrastructure, and capital allocation), tactical (1–3 years, defining annual production targets, waste stripping rates, and fleet sizing), and operational (days to weeks, assigning drill patterns, blast timing, and haul truck cycles). Critical dependencies include geological uncertainty (modelled via conditional simulation), geotechnical constraints (slope angles, rock mass rating), equipment productivity (availability, cycle times), and market-driven constraints (ore grade targets, smelter penalties). Modern practice relies on optimization engines (e.g., Lerchs-Grossmann algorithm for pit limits) coupled with constraint programming for scheduling—moving beyond manual 'cut-and-try' methods.
📐 Lerchs-Grossmann Pit Limit Optimization
The Lerchs-Grossmann (LG) algorithm determines the ultimate economic pit limit by maximizing total undiscounted value (revenue minus costs) across all blocks, respecting slope stability constraints. It transforms the 3D block model into a network flow problem where each block is a node, and arcs enforce feasible slope angles.
💡 Worked Example
Problem: A 10×10×5 block model (500 blocks) has average ore value = $12.50/tonne, waste cost = $1.80/tonne, and density = 2.4 t/m³. Block size = 10m × 10m × 5m. Slope angle constraint = 45° (1:1 horizontal:vertical). Using LG optimization, the algorithm identifies 217 economic blocks.
1.
Step 1: Compute block value = (ore grade × metal price × recovery − mining & processing cost) × block volume × density
2.
Step 2: Assign positive values to ore blocks, negative to waste; apply slope constraint arcs (e.g., block B can only be mined if supporting blocks at shallower elevation are included)
3.
Step 3: Run max-flow/min-cut solver to find maximum-value subset satisfying slope constraints
Answer:
The optimized pit shell contains 217 blocks totaling 2.58 Mt ore and 1.94 Mt waste, yielding a net value of $18.6M. This exceeds the manual pit design (192 blocks, $15.2M) by 18.4% in value.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Western Australia), integration of stochastic geology modelling with LG pit optimization and mixed-integer programming (MIP) scheduling increased gold recovery by 3.2% and reduced average unit cost by $42/oz over three years. The schedule dynamically adjusted quarterly based on updated grade control data and crusher throughput constraints—demonstrating how real-time feedback loops transform static plans into adaptive operating systems.
🔧 Interactive Calculator
🔧 Open Mine Planning & Scheduling Calculator📋 Case Connection
📋 Mine Planning & Scheduling Case Study 1
Inconsistent production scheduling due to inaccurate grade estimation and inflexible short-term plans, leading to 18% mo...
📋 Mine Planning & Scheduling Case Study 2
Inconsistent haul truck utilization due to static, annual mine plans that failed to account for real-time geotechnical v...