Stope layout, which is the specific shape, size, and orientation of an excavation (stope) to extract ore, is influenced by a complex interplay of geological, engineering, and economic factors [1]. The primary goal is to design a stope that allows for the safe, profitable, and efficient removal of the orebody [2]. These factors can be grouped into four main categories.
Geotechnical and rock mechanics factors
This category relates to the physical properties of the rock mass itself and is arguably the most critical for safety and stability.
Rock mass quality: this is a measure of the rock’s overall strength and stability, often quantified using systems like the Rock Mass Rating (RMR) or the Q-system.
- Strong rock: competent, strong rock with few discontinuities allows for large, open stopes with minimal support (e.g., open stoping).
- Weak rock: poor-quality, fractured rock cannot support itself over large spans and requires significant support or a mining method where the stope is progressively backfilled (e.g., cut-and-fill).
Geological structures: the presence, orientation, and characteristics of faults, joints, shear zones, and bedding planes are crucial [3]. These structures act as planes of weakness that can control stope failure. A layout may be oriented specifically to minimize the risk of a wedge or block falling from the stope’s roof (back) or walls.
In-Situ stress: at greater depths, the natural stress in the rock is high [1]. Excavating a stope redistributes these stresses, which can become concentrated on the stope walls and pillars. High-stress conditions can lead to rock bursts or spalling (slabbing off) of the stope walls, requiring specific stope shapes, sequencing, and support to manage.
Orebody characteristics (Geology)
The geometry and nature of the ore deposit itself dictate the fundamental shape of the excavation.
Dip (Inclination): this is a primary determinant of the mining method and, therefore, the stope layout.
- Flat-lying/shallow dip (0-30°): typically mined with room-and-pillar methods, where stopes are wide, flat “rooms” separated by pillars of ore left for support.
- Inclined dip (30-55°): may use methods like shrinkage stoping or cut-and-fill, where the layout is adapted to the incline.
- Steep dip (55-90°): ideal for highly vertical methods like sublevel open stoping or Vertical Crater Retreat (VCR), resulting in tall, narrow stopes.
Thickness and Shape: the orebody’s dimensions directly influence the stope’s dimensions [4].
- Narrow Vein: it requires a narrow stope, which can be challenging for large equipment.
- Massive/Wide Orebody: it allows for large-scale, bulk mining methods with very large stope dimensions (e.g., block caving, sublevel stoping).
- Irregular Shape: a complex or discontinuous orebody may require a more flexible method with smaller, irregular stopes that can selectively follow the ore.
Grade Distribution: the concentration of the valuable mineral within the orebody determines the stope’s economic boundaries [5]. The layout is designed to maximize the extraction of high-grade ore (pay-ore) and minimize the mining of low-grade or barren waste rock. This is defined by the cut-off grade which is the minimum grade that is profitable to mine [3].
Economic factors
Ultimately, the mine must be profitable. The stope layout is a financial optimization problem.
Ore Recovery vs. dilution: this is the most important economic trade-off.
- Recovery: the percentage of the total ore that is successfully mined and sent to the mill. Leaving pillars for support reduces recovery.
- Dilution: the amount of waste rock that is unintentionally mined along with the ore. Wall instability (overbreak) or mining waste rock at the orebody margins increases dilution, which raises processing costs [6].
- The stope layout seeks to find the “sweet spot” of high recovery and low dilution.
Ore Value: high-value ore (e.g., gold, platinum) can justify more expensive, selective mining methods with smaller stopes and higher support costs to maximize recovery. Low-value ore (e.g., some types of copper or iron) requires very cheap, bulk-mining methods with large stopes, even if it means sacrificing some recovery or accepting higher dilution.
Operational and equipment factors
The practical “how-to” of mining constrains the theoretical design.
- Mining method: while selected based on the factors above, the chosen method (e.g., cut-and-fill, open stoping) fundamentally is the stope layout.
- Equipment size: the dimensions of the mine’s equipment (like jumbos for drilling and LHDs for mucking) dictate the minimum and maximum practical width and height of tunnels (drifts) and stopes. You cannot design a 3-meter-wide stope if your equipment is 4 meters wide.
- Backfill: if backfill (using waste rock or cemented paste) is required for stability or to allow mining of adjacent stopes, the layout must incorporate fill raises and allow for the fill to be placed effectively.
- Ventilation: the layout must be designed to allow a continuous flow of fresh air to all working areas.
- Mining sequence: the order in which stopes are extracted is critical. Mining one stope changes the stress on its neighbors. The overall layout must account for this sequence to prevent widespread instability.
Reference
[1] X. Zhou, X. Zhao, Q. Qu, and J. Shi, “Stope Structural Parameters Design towards Green and Deep Mining: A Review,” Processes, vol. 11, no. 11, p. 3125, Nov. 2023, doi: 10.3390/pr11113125.
[2] D. S. S. Sandanayake, E. Topal, and M. W. A. Asad, “Designing an optimal stope layout for underground mining based on a heuristic algorithm,” International Journal of Mining Science and Technology, vol. 25, no. 5, pp. 767–772, Sept. 2015, doi: 10.1016/j.ijmst.2015.07.011.
[3] “The Art of Stope Optimization: Efficiency and Profitability in Underground Mining – K-MINE.” Accessed: Oct. 24, 2025. [Online]. Available: https://k-mine.com/technical-articles/the-art-of-stope-optimization-efficiency-and-profitability-in-underground-mining/
[4] M. Sun, F. Ren, and H. Ding, “Optimization of Stope Structure Parameters Based on the Mined Orebody at the Meishan Iron Mine,” Advances in Civil Engineering, vol. 2021, no. 1, p. 8052827, Jan. 2021, doi: 10.1155/2021/8052827.
[5] M. Furtado e Faria, R. Dimitrakopoulos, and C. Pinto, “Stochastic stope design optimisation under grade uncertainty and dynamic development costs,” International Journal of Mining, Reclamation and Environment, vol. 36, no. 2, pp. 81–103, Feb. 2022, doi: 10.1080/17480930.2021.1968707.
[6] W. Abdellah, M. Hefni, and H. M. Ahmed, “Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part 1,” Geotechnical and Geological Engineering, 2019, Accessed: Oct. 24, 2025. [Online]. Available: https://www.semanticscholar.org/paper/Factors-Influencing-Stope-Hanging-Wall-Stability-in-Abdellah-Hefni/6a370f7a46f238848c0a301951c1ea64e0ad92e0
