TUNNELS AND HYDROGEOLOGY IN KARSTICTERRAIN A CASE STUDY

摘要

The construction of one of the high-speed railway tunnels between Malaga and Cordoba beneath the Abdalajísrnmountains occasioned a series of hydrogeological problems with geotechnical and environmental impacts. The double tunnel, 7300 mrnin length, runs south to north across several small calcareous lines of mountains that are highly complex in structure. Beneath thernJurassic limestones lie Triassic clays and evaporites. Overlying the limestones is an essentially marly and limestone-marl Cretaceousrnseries, which culminates with Miocene marls that contains a certain amount of organic matter.rnThese mountain alignments generate springs that are used for urban water supply and irrigation. The initial water level in thernaquifer series varied from 400 m to 650 m above sea level. After drilling approximately 2900 metres, and intercepting a fracture zonernwithin the carbonate rocks, a sudden outpouring of water occurred that reached a peak flow of 800 L/s. After a short while, the springrndischarges dried up, leading to a public protest in response.rnIn this paper, we describe the geological and hydrogeological settings, the development of the aquifer as the drilling operationrnproceeded, the measures adopted and the responses subsequent to completion of the tunnel, including the effect of rainfall on thernrecovery of water levels. Lastly, a generalized estimate is made of how the system functions and a forecast is made for recovery ofrnits equilibrium.