SUBSIDENCES ASSOCIATED WITH MINING ENVIRONMENTS AND UNDERGROUND WORKS. CASE OF THE COLLAPSE WITHIN THE LORD DERBY CONCESSION (LINARES-LA CAROLINA MINING DISTRICT)

In February 2023, a subsidence phenomenon was superficially evident in the “Lord Derby” concession, within the Linares-La Carolina mining district. This exuberant, cone-shaped subsidence reached approximately 30 meters in diameter on the surface and a depth greater than that measurement, being enhanced by the local geological and hydrogeological conditions, as well as by the historical mining activity in the area. The mining work, developed for centuries, together with the recent constructions intended to make the “La Tortilla” mine accessible to visitors, have influenced the instability of the terrain. This case is representative of a phenomenon that can be repeated in similar environments, where intensive mining or the execution of large-scale underground works have modified the subsoil. In order to assess the susceptibility of other areas to this type of subsidence, a methodology is proposed based on defining the risks of subsidence in mining environments and significant underground works, establishing the conditions that determine the collapse of the “La Tortilla” mine (geology, hydrogeology, exploitation of the aquifer, mining work and perimeter fencing of the visitable mine) and establishing the sequencing of this collapse. As a result, possible solutions are proposed for the case of the collapse of “La Tortilla”, a 3D model of the “Arrayanes” Mine, located in a nearby area, and with similar conditions to those existing in the collapse area, is proposed as an example to help detect areas at risk of subsidence. This model will allow identifying high-risk areas and anticipating possible collapses. Finally, in cases where subsidence could not be prevented, solutions are proposed for the stabilization of the land and appropriate mitigation measures to minimize future impacts. Keywords: Hydrogeology, mining work, sinking, subsidence, underground works.