The access road to the powerhouse's hydraulic system's facilities in Guarumales (Azuay, Ecuador) presents a medium-sized landslide. Geophysical tests were conducted in the initial research stage, combining electrical and seismic methods. A SEV and HVSR surveys campaign have been taken as a reference for the analysis of the landslide area. The distribution of these test points has been at three different levels along the landslide where the access road crosses it and trying to cover the area's most extensive possible length and width. In the area, we find the geology dominated by the presence of schists, altered to different degrees and presenting blocks of material with a lower degree of alteration within colluvium formed by a clayey matrix and coarse material of the exact nature. There is also evidence of surface and groundwater in the area. The results obtained through SEV tests have allowed for defining the separation zone of the mobilized or sliding materials compared to the fixed or immobile ones (potentially, the sliding surface was marked). Using the HVSR technique, the natural vibration frequencies of the ground associated with the sliding mass (separation of seismic impedances between a two-layer model: mobile and fixed) have been determined. Previous authors proposed an empirical relationship establishing the exponential relationship, already proposed by previous authors, between sediment thickness and natural frequencies. It has been possible to determine the depth of the position of the loosely compacted sediment zone (and probably moving or mobilized) compared to that of compact materials (immobile) and thereby define the potential rupture surface.

As in many points in this middle section of the Ebro Valley (Spain), the risks of sinkholes are be-coming particularly severe, affecting urban areas and roads, where land subsidence due to karst-ic processes is frequent. However, knowledge of the area, its geological-geotechnical configura-tion and the carrying out of specific research studies are allowing solutions to be tested in an at-tempt to resolve these situations. The present analysis of the seating problems recorded on a sec-tion of the access road to the town of Gallur from the east (Camino Real) in the province of Zara-goza (Spain), is a good example. Numerous surface manifestations of the recent activity of sub-sidence and/or collapse processes have been reproduced throughout the surrounding area. The latter, appearing in the form of craters, undercuts in the ground, sometimes several metres in di-ameter. The presence of highly karstifiable materials in the area, as indicated by the existence of several pockets of subsidence and collapse dolines, constitutes a serious problem for safety, in this case for traffic and access to the town. For this reason, the road has been closed for several years. The local and provincial administrations have been undertaking studies to try to recognise this type of situation. The detailed definition of the karstification processes, the geomechanical analy-sis of subsidence and cavity collapse, and the justified technical proposal of the measures to be adopted to control and mitigate the risk, were the objectives of several reports in which possible technical solutions were proposed. Finally, a consolidation solution was proposed based on the injection at depth of columns of mortar with special characteristics, combined with the replace-ment and reinforcement of the most superficial soil by means of high tensile strength geotextile meshes.