Building Hyperscale Underground Data Centre Infrastructure in Ownerless and Derelict Coal Mine Voids of the South African Coalfields
Conquest Designer, trained as the Head of Department — Master of Engineering, Civil & Structural Engineering — PhD (Civil, Structural and Mining Engineering), Faculty of Engineering and the Built Environment. CDU Press, Working Paper — applied engineering and policy, design-science evaluation.
Working paper notice — see Issue 1, Paper 1's footer. Engineering results are this house's own published units, re-run and reproducible. The policy history below is stated with the author's confidence level attached at each claim, per the same rule Paper 2 of this issue applies to legislative citation.
Abstract
South Africa's transition from "old order" to "new order" mineral rights under the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) made the state the custodian of the nation's mineral resources and required holders of old order rights to apply for conversion within a prescribed window or lose them (confidence: high — this is the MPRDA's core transitional mechanism). A documented consequence — reported in Council for Geoscience publications on derelict and ownerless (D&O) mines — is that some holders of already-depleted old order rights did not apply to convert them, instead pursuing fresh exploration rights over ground that could still be worked, leaving the depleted sites to default into the ownerless and derelict category, with the rehabilitation liability falling to the state (confidence: medium-high on the mechanism as a documented pattern in the D&O literature; the author has not verified a specific count of sites attributable to this pattern from this sandbox). This paper treats the resulting inventory of disused, structurally intact coal mine voids in the Mpumalanga Highveld coalfield as a civil and mining engineering opportunity: underground space, already excavated, in a region with existing grid infrastructure, reframed as a candidate site class for hyperscale data centre halls. It derives structural support, dewatering and power-chain design figures from this house's own published engineering units.
1 · The wicked problem, and the engineering reframe
A derelict and ownerless mine is, to the rehabilitation-funding question, a liability with no paying party. To a civil engineer, the same void is pre-excavated volume at depth, with a known geological history, often already connected to a rail or road corridor built for the mine that dug it. The reframe this paper proposes: a party that takes over the D&O liability (the rehabilitation obligation) in exchange for the right to develop the void it rehabilitates converts a pure cost for the state into a pure asset for the developer — the state's incentive problem (§0 of this paper's premise, after the Dean's own framing) is solved not by finding money to rehabilitate for no return, but by finding a return that is conditional on rehabilitating. This paper does not model the legal instrument for that exchange (that is Paper 6 of this issue's proper territory, extended); it models the engineering feasibility the instrument would need to be worth drafting.
2 · The site class
Bounded deliberately to the Mpumalanga Highveld coalfield (Emalahleni/eMalahleni and surrounds) — the country's largest concentration of old bord-and-pillar workings, typically at 30–150 m depth, with remaining coal pillars already sized (by the original mine) to carry the overburden indefinitely at the safety factors mining practice used at the time. This paper's structural task is narrower than "design a data hall": it is to check whether those existing pillars and roof spans, under a different load (data-hall plant and floor load, not overburden alone) and a different design code (structural steel and concrete to current practice, not historical mining practice), still pass.
3 · Method and results
3.1 · Roof span support, re-purposed
A representative 6 m bay, carrying a 45 kN/m line load (plant, raised floor, cable tray, and a maintenance allowance) through a new structural steel beam spanning the void's roof: at a first-pass second moment of area of 12,000 cm⁴, beam_udl (src/faculty/degrees/civil.ts) returns a 31.64 mm deflection against a 24 mm serviceability limit — fails, honestly, 32% over. Raising the section to 16,000 cm⁴ (a 33% increase in I) brings deflection to 23.73 mm — inside the limit, with a 1.1% margin, tight enough that the paper recommends the next standard section up in practice, not this exact figure, and states the margin rather than rounds it away.
3.2 · A remaining pillar, checked as a column
Treating a remaining coal pillar, reinforced for this reuse with a concrete liner of 5,000 cm⁴ equivalent stiffness, 4.2 m tall, under a data-hall-scale applied load of 1,800 kN: column_euler returns a critical buckling load of 5,595 kN and a safe load (at the unit's 2.5 safety factor) of 2,238 kN — the applied 1,800 kN load passes, with 24% margin. This is the paper's central engineering claim: a representative pillar geometry in this coalfield, reinforced rather than replaced, can carry a data-hall load class, which is a statement about order of magnitude, not a certification of any named mine — a site-specific geotechnical survey is non-negotiable before any real pillar is loaded this way (§5).
3.3 · Dewatering
Old coal workings flood; a rehabilitation-and-reuse project dewaters before it builds. At a representative 400 m hydrostatic head, water_pressure returns 3,924 kPa (39.24 bar). A dewatering main of 219 mm OD, 240 MPa yield steel, sized by pipe_wall_barlow against a 4,000 kPa design pressure, needs 3.65 mm wall against an installed 8.2 mm — 8,986 kPa allowable, more than double the design pressure, the conservative margin a dewatering main that cannot be easily replaced once the void is sealed around it should carry.
3.4 · The power chain, underground
Paper 2 of this issue's method applies unchanged at hall scale: a single underground hall at 5 MW (roughly a forty-thousand-GPU-equivalent fraction of Paper 2's facility) draws the same transformer and cable sizing logic; the one material difference underground is ride-through economics — grid access to a rehabilitated coalfield site is typically better, not worse, than a greenfield site, because the original mine's own grid connection frequently still exists in some form, a further argument for the site class's feasibility that this paper flags but does not cost.
4 · Discussion
None of the figures in §3 certifies a specific mine. They establish that the order of magnitude — pillar loads in the low thousands of kN, roof spans in single-digit metres, dewatering heads in the hundreds of metres — sits inside what this house's own published structural and hydraulic units already handle competently, which is the engineering precondition for treating "rehabilitate-and-reuse as a data centre" as a serious proposal rather than a slogan. The state's incentive problem the Dean named — nobody benefited from the mine, nobody wants to pay to close it — is exactly the gap a developer willing to take the rehabilitation liability in exchange for the void's reuse right is positioned to close, if the engineering clears, which §3 is the first-pass evidence that it can.
5 · Limitations and further work
This paper used representative, not site-specific, geometry and loads; no named mine was assessed, and no real pillar should be loaded on the strength of this paper alone — a geotechnical and mine-void stability survey specific to any candidate site is the next, non-optional step, and this paper's figures are a feasibility screen, not a permit application. The legal instrument that would let a developer take on a D&O rehabilitation liability in exchange for development rights is not drafted here; it belongs with Paper 6 of this issue (international economic and regulatory law) or a future Mineral Law paper this faculty does not yet offer.
References
- Mineral and Petroleum Resources Development Act 28 of 2002 — the custodianship and old-order-to-new-order conversion regime (confidence: high).
- Council for Geoscience — publications on the Derelict and Ownerless Mines programme (confidence: medium-high on the mechanism described in §0; specific site counts not verified in this sandbox).
src/faculty/degrees/civil.ts—beam_udl,column_euler,water_pressure,pipe_wall_barlow, version 1.0.0 (Conquest Designer University, 2026).- Issue 1, Paper 2 of this volume — the power-chain method applied at hall scale in §3.4.