Numerical analysis of the cliff failure occurred at St. Eutizio Abbey during the 2016 Central Italy seismic sequence

Among the religious monuments that were severely damaged by the 2016-17 Central Italy seismic sequence, one of the most important is the St. Eutizio Abbey (Preci, Umbria Region). The Abbey rises at the foot of a 25-m-high sub-vertical cliff delimiting a wedge-shaped travertine spur, on top of which a cemetery and the bell tower of the Abbey are located. The October 30th main shock caused the failure of the cliff and the successive collapse of the bell tower. The aim of this study is to investigate the structural and geotechnical factors controlling these failures. A geotechnical slope model was developed using LiDAR, borehole data, and laboratory tests. Bi-dimensional stress-strain dynamic analyses (linear and non-linear elasto-plastic) were conducted to evaluate how stratigraphy and topography modified the seismic motion, analyse the state of stress induced by the seismic events in the travertine spur, and hence the triggering of failure phenomena both in the rock and in the rock-interacting structures. Additionally, a three-dimensional analysis to get preliminary information on the potential effects of soilstructure interaction on the dynamic behaviour of the tower was performed.