Response of an embankment dam with internal core in the 2016 earthquake sequence in Central Italy

The paper describes the response of an embankment dam to the 2016 earthquake sequence in Central Italy. The dam was completed in the sixties and since its construction was strongly instrumented with an extensive monitoring system. The intent of the instruments was to provide information within and below the embankment to detect different critical situations that could have occurred during the lifetime of the dam and natural events. In the paper, after a description of the monitoring system and the role of different instruments, the response of the dam to the 2016 earthquake sequence is reported and discussed. Focus will be essentially on the excess pore pressures measured in the foundation which result from the induced deformations above the volumetric threshold strain in fine-grained soils. The susceptibility to high pore-pressure build-up and strength loss of these soils was recognized as a potential failure mode during strong earthquakes. Advanced laboratory testing was critical in assessing the seismic performance of the dam during the 2016 seismic sequence. It was also instrumental for the seismic and post-seismic stability of the dam providing valuable insight into the potential performance for strong ground shaking. The case history shows that the monitoring system proved to be capable of identifying even the minor damages occurred during the shaking and avoided unnecessary drawdown of the reservoir. This is particularly important in situations where dam safety problems are known to exist and the instrumentation system can monitor a particular failure mode, thus providing indications for civil protection activities related to dam safety.