The El Teniente Mine of Codelco is one of the largest underground mine operations in the world. The mine employs massive mechanised panel caving methods with pre-undercut variants to extract copper-molybdenum ore, producing 140,000 t/d, mainly of primary copper ore. In the context of a study of rehabilitation measures for collapsed zones at the Esmeralda mine, which is one of Tenientés most important operations, a preliminary assessment of the post-collapse pillar's rock mass condition was carried out, allowing the characterization of the damage zone surrounding the drifts and some insights into the likely pillar's rock mass damage development. The paper outlines these findings and discusses some underlying factors that may also have influenced the process.