Earthquake Risk Management of Underground Lifelines in the Urban Area of Catania

摘要

Lifelines typically include the following five utility networks: potable water, sewage natural gas, electric power, telecommunication and transportation system. The response of lifeline systems, like gas and water networks, during a strong earthquake, can be conveniently evaluated with the estimated average number of ruptures per km of pipe. These ruptures may be caused either by fault ruptures crossing, or by permanent deformations of the soil mass (landslides, liquefaction), or by transient soil deformations caused by seismic wave propagation. The possible consequences of damaging earthquakes on transportation systems may be the reduction or the interruption of traffic flow, as well as the impact on the emergency response and on the recovery assistance. A critical element in the emergency management is the closure of roads due to fallen obstacles and debris of collapsed buildings.The earthquake-induced damage to buried pipes is expressed in terms of repair rate (RR), defined as the number of repairs divided by the pipe length (km) exposed to a particular level of seismic demand; this number is a function of the pipe material (and joint type), of the pipe diameter and of the ground shaking level, measured in terms of peak horizontal ground velocity (PGV) or permanent ground displacement (PGD). The development of damage algorithms for buried pipelines is primarily based on empirical evidence, tempered with engineering judgment and sometimes by analytical formulations.For the city of Catania, in the present work use has been made of the correlation between RR and peak horizontal ground velocity by American Lifelines Alliance (ALA, 2001), for the verifications of main buried pipelines. The performance of the main buried distribution networks has been evaluated for the Level I earthquake scenario (January 11, 1693 event I = XI, M 7.3) and for the Level II earthquake scenario (February 20, 1818 event I = IX, M 6.2).Seismic damage scenario of main gas pipelines and water has been obtained, with PGV values calculated for level I and level II earthquake scenarios.