Identification and Investigation of Subsidence Areas to Mitigate Karstic Risks in Urbanized Areas of Madrid, Spain: A Case Study

A multidisciplinary investigation was carried out in a karstic depression housing development under construction Madrid to assess its stability. It found that it is small basin within larger as result of subsidence accumulated during the Quaternary. Subsidence has built up progressively Miocene clay cap and bedrock due underlying dissolution gypsum rich intercalations. The preferential circulation dissolving subsurface flow along fault conditioned by subsidence, formation an elongated syncline fracture, alluvial basin. During Pleistocene, former lagoon zone formed this subsiding area; also groundwater discharge zone. decrease recent times very could be evaluated about 0.4 mm/year, affects furrow zone, where maximum average rate would 1.4 mm/year. This led relatively strong alluvium. seems deposits, slow diffuse taking place shallower clayey gypsiferous levels, free hypersoluble mineral species; somewhat more intense which active hydrodynamically, velocity higher. Microgravimetry surveys indicate only 5% area hidden alluvium shows anomalies, interpreted residual soft masses, or anomalous fillings old voids. These pockets (“bolsones”), have dimensions no than 20 × m depths below m. measurements been confirmed boreholes are points require special attention future urbanization. urbanization work, full development, implementing solutions aimed at stability road strips studied.