eprintid: 1952 rev_number: 10 eprint_status: archive userid: 9 dir: disk0/00/00/19/52 datestamp: 2017-06-27 10:38:22 lastmod: 2017-06-27 10:38:22 status_changed: 2017-06-27 10:38:22 type: article metadata_visibility: show creators_name: Lebert, F. creators_name: Bernardie, S. creators_name: Mainsant, G. corp_creators: BRGM corp_creators: BRGM corp_creators: BRGM, ISTerre title: Hydroacoustic monitoring of a salt cavity: an analysis of precursory events of the collapse subjects: O subjects: RF4 subjects: SMU divisions: IP15 full_text_status: none abstract: One of the main features of "post mining" research relates to available methods for monitoring mine-degradation processes that could directly threaten surface infrastructures. In this respect, GISOS, a French scientific interest group, is investigating techniques for monitoring the eventual collapse of underground cavities. One of the methods under investigation was monitoring the stability of a salt cavity through recording microseismic-precursor signals that may indicate the onset of rock failure. The data were recorded in a salt mine in Lorraine (France) when monitoring the controlled collapse of 2 000 000 m3 of rocks surrounding a cavity at 130 m depth. The monitoring in the 30 Hz to 3 kHz frequency range highlights the occurrence of events with high energy during periods of macroscopic movement, once the layers had ruptured; they appear to be the consequence of the post-rupture rock movements related to the intense deformation of the cavity roof. Moreover the analysis shows the presence of some interesting precursory signals before the cavity collapsed. They occurred a few hours before the failure phases, when the rocks were being weakened and damaged. They originated from the damaging and breaking process, when micro-cracks appear and then coalesce. From these results we expect that deeper signal analysis and statistical analysis on the complete event time distribution (several millions of files) will allow us to finalize a complete typology of each signal families and their relations with the evolution steps of the cavity over the five years monitoring. date: 2011 date_type: published publication: Natural Hazards and Earth System Science volume: 11 number: 9 publisher: Copernicus Publications pagerange: 2663-2675 id_number: doi:10.5194/nhess-11-2663-2011 issn: 1684-9981 official_url: http://doi.org/10.5194/nhess-11-2663-2011 access_IS-EPOS: limited owner: Publisher citation: Lebert, F. and Bernardie, S. and Mainsant, G. (2011) Hydroacoustic monitoring of a salt cavity: an analysis of precursory events of the collapse. Natural Hazards and Earth System Science, 11 (9). pp. 2663-2675. DOI: https://doi.org/10.5194/nhess-11-2663-2011