GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.2 661 Cottone, F., Vocca, H., Gammaitoni, L.; 2009. Nonlinear energy harvesting . Physical Review Letters, 102(8), 080601. doi: https://doi.org/10.1103/PhysRevLett.102.080601 Kearey, P., Brooks, M. Hill, I.; 2002. An Introduction to Geophysical Exploration . 3rd ed., Volume 140 Issue 262 pp. ISBN 0 632 04929 4. Oxford: Blackwell Science. Zhu, D., Tudor, M. J., Beeby, S. P.; 2009. Strategies for increasing the operating frequency range of vibration energy harvesters: a review . Measurement Science and Technology, 21(2), 022001. doi:10.1088/0957-0233/21/2/022001 PRELIMINARY RESULTS OF A NOVEL ANALYTICAL APPROACH TO DETECT ROCK MASS DAMAGING FROM MICROSEISMIC EMISSIONS D. D’Angiò 1 , L. Lenti 2,3 , S. Martino 1 1 Department of Earth Sciences and Research Centre for Geological Risks (CERI), “Sapienza” University of Rome, Italy 2 French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR) - Paris East University, France 3 Cerema, Equipe-Projet MOUVGS, Sophia-Antipolis, France Introduction. Rockfalls are a main hazardous source in mountainous areas and along transportation routes (Budetta 2004, Macciotta et al. , 2017). These slope instabilities can be triggered by the jointed contribution of external solicitations, whether sporadic, like earthquakes and rainfalls, and continuous, like daily thermic variations and environmental vibrations. These actions cumulate strain effects over time resulting in rock mass damaging phenomena, intended as the formation of new fractures or as the movement and extension of the pre-existing ones (Amitrano 2006). The microseismic monitoring of unstable portions of rock masses, thanks to the resolution and sensitivity of modern seismic devices, allows to record very weak seismic signals related to the deformational processes taking effect within the rock mass fractures network (Spillmann et al. , 2007). In this study, a novel analytical tool is proposed and applied on a microseismic dataset acquired on a rock mass located in an experimental test site in central Italy. The damping parameters associated with the recorded microseismic emissions were analysed and compared over time, in order to relate potential variations of the long-time trend with rock mass damaging phenomena. Microseismic monitoring at Acuto test site. On Autumn 2015, an abandoned quarry located NE of the village of Acuto (Frosinone district) has been individuated as test site for the installation of a multi-sensor monitoring system, devoted to the investigation of the long-term rock mass deformations due to temperature, wind and rainfalls. The quarry front is 500 meters long and is characterised by a rock wall that reach heights up to 50 meters, and that are made up of Mesozoic wackestone with rudists belonging to the carbonatic succession of the Monti Ernici (Accordi et al. , 1986). The western portion of the quarry is characterised by a protruding and prone to failure rock block of about 12 m 3 , partially separated by a main open fracture from the back quarry wall and chosen as the focus of the experimental activities and for the installation of the multi-sensor monitoring system. This latter consists of: 1 thermometer for the rock mass temperature; 6 strain-gauges installed on fractures of the rock mass; 4 extensimeters installed on open fractures and 2 weather stations, installed at foot and top of the slope wall both equipped with air-thermometer, hygrometer, pluviometer and anemometer for wind speed and direction (Fantini et al. , 2016). Up to now, several experimental activities aimed at analysing the influence of thermal and dynamic stresses acting on the monitored rock block were carried out, aiming at understanding the processes responsible for the accumulation of inelastic strain within the rock matrix and thus of the microfracturing processes (Fantini et al. , 2017, Fiorucci et al. , 2018).