SAFER · Detecting slow deformation signals preceding dynamic failure: A new strategy for the mitigation of natural hazards
FP7 — People (Marie Curie Actions)
- Duration
- 2014-03-01 → 2018-02-28
- EU contribution
- €100,000
- Participants
- 1
- Scheme
- MC-CIG
Lines connect the coordinator with its partners.
Results in brief
Detecting slow deformation signals preceding dynamic failure: A new strategy for the mitigation of natural hazards
The proposal has aimed to identify ‘in situ’ characteristic slow deformation signals and to carry out rock mechanics/deformation tests to quantitatively determine the thermo hydro-mechanical processes leading to instability. To this purpose the monitoring of unstable rock masses can provide a better knowledge of the active processes and help to forecast their evolution to failure. Passive seismic monitoring can be potentially helpful for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. We have first carried out a cross-hole seismic tomography survey coupled with laboratory ultrasonic velocity measurements and physical properties determination on rock samples to characterize the damaged and potentially unstable granitic cliff of Madonna del Sasso (NW, Italy). Results have allowed to obtain: i) a lithological interpretation of the velocity field obtained at the site, ii) a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granite (weathering and anisotropy) of the cliff. The multi-scale approach adopted within this study revealed to be crucial for the imaging at depth of the main fractures affecting the cliff (site-scale seismic tests) and for the understanding of the variations in the seismic velocity between altered and intact rock (laboratory scale tests); similar approaches can be potentially used in further microseismic monitoring studies. On the basis of these indications a microseismic network has been installed during the summer of 2014 on the Madonna del Sasso cliff. The network consists of four triaxial geophones (4.5 Hz, 1-4KHz) connected to a multichannel acquisition system (Granite - Kinemetrics). During the monitored period, we recorded thousands of events with different waveforms, duration and frequency content. The signals were analysed and classified to extract only the ones with a possible relation with fracture processes. No acceleration in the event rate or significant correlation with variations of external factors (air temperature, rainfalls) was detected in the monitored period. Finally a 3-D numerical modelling of the cliff response was performed using the continuous-medium finite-element software Comsol Multiphysics. The two tested models gave fully comparable results in term of motion orientation, with a slight difference in the obtained first three frequency values. Numerical simulations allowed to semi-quantitatively interpret the observations.
Data: CORDIS, © European Union
Project objective
We propose a new strategy based on an interdisciplinary unitary and integrated approach aimed to monitor and detect small signals of impending failures and mitigate natural hazards, by:1) quantify of critical damage thresholds triggering dynamic failure, throughout the ‘In situ’ identification of characteristic slow deformation signals and accelerating patterns before impending ‘large scale’ failure events;2) set up of early warning models for forecasting the time of rupture with application to natural hazards;3) transfer of knowledge between multiscale signs of slow deformation before dynamic failure from the laboratory to field.In detail, we propose to develop innovative strategies for forecasting dynamic ruptures by monitoring an unstable patch of the Gollone landslide on the Italian Western Alps, prone to the development of rock falls and repeated failure episodes, preceded by neat and long lasting episodes of slow deformation. In order to do so, we aim to identify the characteristic signs of impending failure, by installing a “site specific” microseismic monitoring (1-200kHz) system for acoustic emission/microseismic (AE/MS), integrated with a conventional monitoring for seismic detection (1-10Hz) and ground deformation monitoring (strainmeters, geophones and accelerometers).The installation of the monitoring network will be accompanied by a detailed geophysical characterization of the test site in order to establish the best nodes position and internal characteristics of the monitored landslide. Rock physical and mechanical characterization along with rock deformation laboratory experiments during which the evolution of related physical parameters under simulated conditions of stress and fluid content will be studied and theoretical modelling will allow to come up with a full hazard assessment and test new methodologies for a much wider scale of applications within EU.
Original text from CORDIS.
Participants
- UNIVERSITY OF LEICESTER · LeicesterCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union