Environmental forcings and micro-seismic monitoring in a rock wall prone to fall during the 2018 Buran winter storm

Abstract

This study reports a comparative analysis of the environmental conditions and micro-seismicity recorded on a rock wall resulting from an intense meteorological event. The findings are focused on a quarry wall located in the Acuto Field Laboratory (Central Italy), where multi-parametric environmental monitoring is operating and an Artificial intelligence Camera Prototype has been placed to detect rock falls reaching a railway target. Six accelerometers were installed to detect micro-seismic events caused by the expected strong thermal transient caused by the Buran storm on February 2018. Within a few hours, a steep decrease in the average air and rock mass temperature down to 8 °C was recorded, and −4 °C and −8 °C were reached for the rock and air temperatures, respectively. A total of 103 micro-seismic events were analysed with respect to both rainfall and thermal forcing: while no correlation with rainfall was reported, the steep thermal transient was responsible for the strain effect that occurred during the heating phase of the rock mass following the Buran storm. An elastic deformation event with a maximum daily amplitude of 165 μ strain was recorded by the strain gages installed on the mm-joints due to the rock heating and cooling caused by the variation in temperature. The collected evidences show the relevance of short thermal transients in modifying stress conditions within rock masses and their relationship to a peculiar micro-seismic response. The main outcomes established the key role played by integrated monitoring systems to better understand the relationship between vibrational behaviour and environmental forcings in terms of understanding the precursors to rock failure.

Analysis of Thermally Induced Strain Effects on a Jointed Rock Mass through Microseismic Monitoring at the Acuto Field Laboratory (Italy)

“…The highest peak in the daily distribution of MS events (32), which is also preceded and followed by days of intense MS activity, is located within a time window characterized by a sharp decrease in rock mass temperatures and consistent rainfalls/snowfalls. At the end of February 2018, the entire region of Central Italy experienced an extreme meteorological event due to an incoming perturbation associated with the buran, a cold north-easterly wind that is typical of the steppes of the Siberian region [17]. At the Acuto field laboratory, air and rock mass temperatures reached their minimum values of −7.7 • C and −3.8 • C, respectively, and almost 106 mm of rainfall occurred within a 7-day time interval.…”

“…Ambient seismic noise, microseismic activity, and acoustic emission monitoring techniques showed the greatest potential in providing new insights into rock mass fracturing processes. These techniques proved to be useful in highlighting how daily and annual oscillations of near-surface temperatures can cause evident changes in the stability of jointed rock masses, ultimately impacting the evolution in time of already recognized slope instabilities on various dimensional scales [8][9][10][11][12][13][14][15][16][17]. The exploitation of high-sensitivity seismic sensors for studying rock mass instabilities has well-constrained the existence of cause-and-effect relationships between growing instability conditions and microseismic activity [8,15,18].…”

“…Furthermore, they have shown great potential in providing precursory patterns of failure events [19,20]. In the framework of structural health monitoring of natural and anthropic structures, microseismic (MS) signal analysis nowadays represents one of the most widespread diagnostic tools in several fields of application [12,17,[21][22][23]. MS events are low-energy seismic signals genetically related to the occurrence of plastic deformations within a medium.…”

Temperature Changes Analysis in Jointed Rock Mass to Investigate Effects Driving Slope Instabilities at the Acuto Field Laboratory (Italy)

“…Micro-seismic activity preceded a rockfall event of about 1 m 3 that detached close to the monitored rock block. Such a failure event was automatically detected through a change detection algorithm embedded into an AI optical camera (D'Angiò et al 2021). The long-term monitoring instead (Fig.…”

3D Thermal Monitoring of Jointed Rock Masses through Infrared Thermography and Photogrammetry

“…Furthermore, quantitative studies will be approached via numerical and laboratory analyses in order to understand the time needed by preparatory actions to cause failure in kinematically predisposed sectors. At the same time, the influence of weak triggering forces (posed by induced vibration or self-induced oscillations) in inducing instability will be dealt with by considering several evolutionary stages of constant rate processes such as internal resistance decreases due to rock weathering [50], progressive rock mass damaging, fatigue or creep processes [51,52] and the accumulation of slight and irreversible subcritical plastic deformations [53][54][55], weighting their contribution in the rockfall hazard.…”