Geophysical and geotechnical studies applied to determine a subsidence problem in Pachuca de Soto, Hidalgo, Mexico

摘要

In 2005, a subsidence event occurred in the 305 Peñuñuri alleys in the neighbourhood of El Arbolito, Pachuca, Mexico. It produced a cavity of 12 m depth and 14 m width. In 2006, a geophysical and geotechnical study was carried out to determine the cause of the subsidence and to detect the probable abandoned tunnels close to it, which might be a hazard. The study was carried out using electrical tomography, which explored at a depth of 20 m (on average). It was concluded that there was no evidence of cavities. However, a layer saturated with water was observed and the layer seemed to flow in the direction of the topography. The water washes the ground away to form a cavity and the soil collapses when the resistance has gone. Recommendations were: (1) to extend the study of the electric tomography towards the north, west and east; (2) to repeat the lines in dry seasons; (3) to complement the research with a geotechnical study of the materials of the subsoil and the houses around to quantify the damage, and (4) to carry out exploratory drilling of holes on the high resistivity anomalies. The local authorities decided to perform recommendations (3) and (4).