Mechanical Properties, Damage Evolution, and Field Performance of Energy‐Dissipating Shaft Lining Concrete for an Ultradeep Shaft

Ultradeep shaft linings are exposed to complex deep‐engineering environments characterized by high in situ stress, groundwater pressure, and repeated construction and mining disturbances, which increase the risk of brittle damage and structural instability. To improve the deformation adaptability and energy‐dissipation capacity of shaft lining concrete, this study investigated fiber‐reinforced energy‐dissipating concrete based on an ultradeep shaft project in the Sanshandao gold mine. Steel‐like synthetic fibers, galvanized steel fibers, and stainless steel fibers were incorporated at dosages of 1.5% and 2.0%. Mechanical tests, impact energy index tests, acoustic emission (AE) monitoring, and microstructural characterization were conducted to evaluate the effects of fiber type and dosage on mechanical performance, energy dissipation, and damage evolution. The results showed that steel‐like synthetic fibers provided limited strength enhancement, whereas galvanized steel fibers and stainless steel fibers markedly improved the mechanical performance. In particular, 2.0% galvanized steel fibers increased the compressive and splitting tensile strengths by 25.7% and 68%, respectively. The three fiber types reduced the impact energy index by 44%–48%, 51%–54%, and 54%–58%, respectively, indicating reduced brittleness and improved resistance to impact‐induced instability. AE monitoring further revealed that galvanized steel fibers delayed crack localization and rapid damage development, whereas fiber bridging, interfacial friction, and progressive pull‐out contributed to sustained post‐peak load‐bearing and energy dissipation. SEM/EDS observations provided microstructural evidence for the improved fiber–matrix interaction and crack‐bridging mechanisms. Based on the comprehensive experimental results, concrete containing 2.0% galvanized steel fibers was selected for field application in the ultradeep shaft. Approximately 40 days of in situ strain monitoring showed gradually stabilized deformation without abrupt changes or sustained divergence. These results provide preliminary field evidence that the proposed energy‐dissipating concrete can mitigate brittle instability and improve the service stability of shaft linings in deep engineering environments.