1697 stabilizing fractured ground and stopping water inflows (Hildreth et al., 2020). Over time, the range of injectable materials has expanded to include ultra-fine cements, water-reactive foams, and fast-curing organo-mineral resins. These innovations have broadened the applicability of injections from civil tunneling projects into the realm of hard rock and soft-rock mining. Today’s underground mines extract a variety of deposit types (from narrow high-grade veins to massive porphyry orebodies and even evaporite or coal seams) each presenting distinct geotechnical challenges. For example, vein-type gold deposits often occur in highly fractured host rock with significant water inflows along faulted contacts. Massive base metal deposits (e.g., lead-zinc or copper) may require large openings or long hole stopes, raising concerns about wall stability and dilution. Block caving operations induce controlled rock mass fracturing on a large scale but must contend with subsidence and potential mud rushes if water and fines mix. Coal seams and other bedded deposits lie in comparatively weak sedimentary strata that can collapse if not adequately supported, especially under aquifers or gas pressures. While these scenarios differ, a common theme is that uncontrolled water and poor ground conditions can cause costly delays, safety incidents, and ore losses if not managed (Barton & Quadros, 2019). In this context, injection-based ground improvement is an increasingly vital component of mine design and operations. By incorporating pre-excavation grouting (ahead of development drives or shaft sinking) and post-excavation injections (to stabilize problematic areas or stop leaks), mines can significantly reduce geotechnical risk. Pre-injection of water-bearing zones can limit water inflow and improve rock quality before mining advances, making development more predictable (Barton & Quadros, 2019). Postinjection allows remediation of unforeseen conditions, such as sealing a sudden burst of water or consolidating a fractured pillar discovered during operations. Crucially, injection programs can be customized to the geological conditions: selecting appropriate materials and techniques to address the specific needs of each deposit and each affected zone within a mine. This paper focuses on the applications and benefits of injection and consolidation technologies across typical underground mining scenarios, highlighting results from field cases and the integrated approach required to tackle these challenges effectively. 2. GEOTECHNICAL CHALLENGES IN UNDERGROUND MINES AND INJECTION SOLUTIONS 2.1 Water ingress control water entering mine workings can degrade rock strength, erode support, and slow production. High inflows may flood stopes or tunnels, require expensive pumping and causing downtime. Traditional drainage methods (like sumps and pumping) often struggle when water inflow is large or under pressure. Here, pregrouting and water-stopping injections are invaluable. Pre-excavation grouting involves drilling boreholes ahead of a tunnel face or around a shaft and injecting cementitious grout to seal permeable fractures and pores. This creates a curtain that controls water inflow and limits groundwater drawdown around the excavation (Barton & Quadros, 2019). For instance, at a deep metal mine with known aquifers along a drift path, microfine cement injections reduced water inflows to a trickle, allowing excavation to continue on schedule (Barton & Quadros, 2019). In cases of emergency water inflows or where immediate action is needed, water-reactive polyurethane resins are often used. These resins expand upon contact with water, rapidly plugging leaks and fissures. Mines have effectively deployed fast-foaming polyurethane to stop sudden inrushes through faults or drillholes, restoring dry conditions within minutes (Hildreth et al., 2020). By moving water out of critical areas and sealing off its pathways, injections enable other support (such as shotcrete liners or rock bolts) to perform as intended without being undermined by erosion or hydrostatic pressure.
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