1700 Deposit Type Key Geotechnical Challenges Injection/Consolidation Solutions Stratified deposits (coal, potash) Weak roof and floor prone to collapse; Water and gas inflows along bedding planes; Longwall faces cutting through faults. Polyurethane injection into roof and floor to create thicker, reinforced beams (Molinda, 2004); Grouting of aquifers above coal seams to prevent water inrush; Injection ahead of longwall through faults to consolidate and reduce roof falls (Hildreth et al., 2020). Table 1: Typical underground deposit types, their geotechnical challenges, and injection-based solutions. Each mine presents unique conditions, so solutions are tailored – often a combination of techniques is used for optimum effect. 3. RESULTS Field applications of injection and consolidation technologies in mining have yielded measurable improvements in ground stability, safety, and operational efficiency. In this section, we highlight key results from several projects that illustrate the impact of these techniques: Improved water control and advance rates: in a Scandinavian zinc mine, pre-grouting of a waterrich fault zone ahead of a decline development reduced water ingress by over 90%, from ~500 liters/min down to under 50 liters/min as tunneling proceeded. This drastic reduction allowed uninterrupted advance and eliminated the need for round-the-clock dewatering in that section. The surrounding rock mass quality (measured by Q-value) was observed to increase after grouting, indicating a drier and more competent ground structure (Barton & Quadros, 2019). The ability to “make the geology transparent” by pre-injection – i.e., turning a potential water and ground hazard into a benign zone – is a clear result that underpins more predictable and faster development cycles. Stabilization of fractured ore zones enabling ore recovery: a recent case at a Mexican underground mine demonstrated that a robust injection program can convert a highly unstable area into a minable reserve. The target was a valuable ore block situated between previously collapsed stopes and traversed by multiple faults. Initial evaluations showed that conventional reinforcement could not guarantee stability; unsupported, the block would likely collapse or have to be abandoned. The injection experts, in partnership with the mine’s engineers, designed a systematic pre-consolidation injection plan. Multiple rows of boreholes were drilled around the block from adjacent drifts, and an organo-mineral resin was injected to permeate the surrounding fractured ground (Ferrenbach, 2025). The resin’s high penetration and rapid strength development created a reinforced shell around the block. Result: The consolidated block remained stable during the subsequent long hole blasting and extraction. The mine successfully recovered 100% of the ore in this block in a single continuous stope, with no unplanned dilution or ground falls. In addition to the safety achievement (no collapses or injuries), the economic benefit was significant: an estimated 15–20% increase in recoverable ore from that section, translating to millions in additional revenue that would have been forfeited if the block were lost. This case has become a benchmark within the company for how intelligent injection design can enable safe mining of challenging reserves. Consolidation of backfill for pillar mining: at the Toguraci gold mine in Indonesia, a novel application of grout injection was used to improve the stability of unconsolidated rockfill (URF) in historic stopes, allowing the extraction of underlying sill pillars that were previously deemed risky. The approach involved drilling injection holes into the old backfilled stopes from levels above and pumping a cementitious grout at a controlled water: cement ratio throughout the fill mass (Proudman et al., 2017). Over a series of stages, the fractured rockfill material was turned into a more competent, concrete-like body (with an average uniaxial compressive strength ~8 MPa achieved in the fill). Result: The cemented fill was able to temporarily support itself as the sill pillars beneath were blasted and extracted. No fill collapse occurred during pillar recovery, and only minimal dilution was recorded in the ore, validating the effectiveness of the preconsolidation. This project demonstrated that even loose waste materials can be converted into stable
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