KEYWORDS In-Situ Stress Estimation, Acoustic Emission (AE), Kaiser Effect, Underground Mining, Rock Mechanics 1. INTRODUCTION Accurate knowledge of the magnitude and orientation of the in-situ stress field is fundamental for underground mining, because stress governs excavation response, brittle damage development, support demand, and the probability of dynamic instability as depth and extraction intensity increase. In many operations, including the Polish copper mines of KGHM, comprehensive determination of the full principal stress state is not routinely available at the mine scale; instead, engineering decisions and model calibrations often rely on simplified assumptions or sparse historical measurements. This creates a practical gap: without site-specific stress tensors, it is difficult to reliably reproduce stress-driven damage mechanisms in numerical analyses or to interpret monitoring signals in terms of evolving stability. This limitation is especially important for numerical simulations, where the initial stress field strongly influences predicted convergence, yielded zones, and local failure around excavations. Core-based laboratory techniques exploiting acoustic emission (AE) offer an attractive complementary pathway, because they transfer the measurement effort from the underground environment to controlled laboratory conditions using material that is routinely recovered during exploration drilling. The conceptual basis is the Kaiser effect, i.e., the tendency for AE activity during reloading to remain low until the specimen exceeds the maximum previously experienced stress level, at which point AE increases markedly (Lavrov, 2003; Friedel & Thill, 1990). Building on this stress-memory principle, AE methods have been developed to estimate stress components—and, with oriented core and multi-directional subcoring, to reconstruct the full stress tensor (Villaescusa, Seto & Baird, 2002; Villaescusa, Windsor, Li, Baird, & Seto, 2003; Seto & Villaescusa, 1999). The feasibility and limitations of AE–Kaiser approaches have also been discussed in broader methodological syntheses (Blanksma, 2011; Dinmohammadpour, Nikkhah, Goshtasbi, & Ahangari, 2022). At the same time, recent studies highlight that AE-derived stress estimates are sensitive to lithology and protocol choices, which is particularly relevant when comparing carbonates and sandstones. Loading rate can shift the identified Kaiser point and affect accuracy across different rock types (Zhang, Okere, & Su, 2021), while anisotropy and specimen orientation can modify the clarity and repeatability of the stress-memory signature (Kharghani, Goshtasbi, Nikkhah, & Ahangari, 2021). Additional evidence suggests that stress-memory behaviour may be more complex than a single threshold under certain loading paths (Ma et al., 2025), motivating careful interpretation frameworks and objective criteria, including approaches that combine theory with experimental validation (Bai et al., 2018) and demonstrations in deep applications (Qin, 2019). Against this background, the present pilot study evaluates AE monitoring and Kaiser-effect interpretation during cyclic loading of carbonate and sandstone specimens to test the
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