Remote analysis of an open-pit slope failure: Las Cruces case study, Spain
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Juan López-Vinielles I Pablo Ezquerro I José A. Fernández-Merodo I Marta Béjar-Pizarro I Oriol Monserrat I Anna Barra I Pablo Blanco I Javier García-Robles I Antón Filatov I Juan C. García-Davalillo I Roberto Sarro I Joaquín Mulas I Rosa M. Mateos I José M. Azañón I Jorge P. Galve I Gerardo Herrera
Remote analysis of an open-pit slope failure: Las Cruces case study, Spain
Abstract Slope failures occur in open-pit mining areas worldwide, producing considerable damage in addition to economic loss. Identifying the triggering factors and detecting unstable slopes and precursory displacements —which can be achieved by exploiting remote sensing data— are critical for reducing their impact. Here we present a methodology that combines digital photogrammetry, satellite radar interferometry, and geomechanical modeling, to perform remote analyses of slope instabilities in open-pit mining areas. We illustrate this approach through the back analysis of a massive landslide that occurred in an active open-pit mine in southwest Spain in January 2019. Based on pre- and post-event high-resolution digital elevation models derived from digital photogrammetry, we estimate an entire sliding mass volume of around 14 million m3. Radar interferometry reveals that during the year preceding the landslide, the line of sight accumulated displacement in the slope reached − 5.7 and 4.6 cm in ascending and descending geometry, respectively, showing two acceleration events clearly correlated with rainfall in descending geometry. By means of 3D and 2D stability analyses we located the slope instability, and remote sensing monitoring led us to identify the likely triggers of failure. Las Cruces event can be attributed to delayed and progressive failure mechanisms triggered by two factors: (i) the loss of historical suction due to a pore-water pressure increase driven by rainfall and (ii) the strainsoftening behavior of the sliding material. Finally, we discuss the potential of this methodological approach either to remotely perform post-event analyses of mining-related landslides and evaluate potential triggering factors or to remotely identify critical slopes in mining areas and provide pre-alert warning. Keywords Open-pit mine . Structure from motion (SfM) . Satellite radar interferometry (InSAR) . Stability analysis . Finite element method (FEM) . Shear strength reduction (SSR) Introduction Mass movements and surface deformations, caused by ground subsidence or slope instability processes, are very frequent phenomena in both abandoned and active mining areas (Bell and Donnelly 2006). In open-pit mining, ground movements potentially lead to slope failures entailing risks for personnel, equipment, and infrastructures, in addition to disrupting mine scheduling and increasing production costs (Paradella et al. 2015). Yet the absence of failure in an open-pit mine could be a sign of overconservative slope design (Hoek et al. 2000). Conducting comprehensive slope monitoring and modeling programs is essential for the open-pit mining industry to ensure
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