Toward Workable and Cost-Efficient Monitoring of Unstable Rock Compartments with Ambient Noise

Abstract

Ambient Vibration-Based Structural Health Monitoring (AVB–SHM) studies on prone-to-fall rock compartments have recently succeeded in detecting both pre-failure damaging processes and reinforcement provided by bolting. The current AVB–SHM instrumentation layout is yet generally an overkill, creating cost and power issues and sometimes requiring advanced signal processing techniques. In this article, we paved the way toward an innovative edge-computing approach tested on ambient vibration records made during the bolting of a ~760 m3 limestone rock column (Vercors, France). First, we established some guidelines for prone-to-fall rock column AVB–SHM by comparing several basic, computing-efficient, seismic parameters (i.e., Fast Fourier Transform, Horizontal to Vertical and Horizontal to Horizontal Spectral Ratios). All three parameters performed well in revealing the unstable compartment’s fundamental resonance frequency. HHSR appeared as the most consistent spectral estimator, succeeding in revealing both the fundamental and higher modes. Only the fundamental mode should be trustfully monitored with HVSR since higher peaks may be artifacts. Then, the first application of a novelty detection algorithm on an unstable rock column AVB–SHM case study showed the following: the feasibility of automatic removing the adverse thermomechanical fluctuations in column’s dynamic parameters based on machine learning, as well as the systematic detection of clear, permanent change in column’s dynamic behavior after grout injection and hardening around the bolts (i1 and i2). This implementation represents a significant workload reduction, compared to physical-based algorithms or numerical twin modeling, and shows better robustness with regard to instrumentation gaps. We believe that edge-computing monitoring systems combining basic seismic signal processing techniques and automatic detection algorithms could help facilitate AVB–SHM of remote natural structures such as prone-to-fall rock compartments.

Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems

“…Seismological monitoring methods are thus useful to investigate and keep track of the mechanical state of potentially unstable sites. Several studies have shown the applicability of these methods to track the failure of rock columns (Levy et al 2011, Chiara Colombero et al 2021, Pierre Bottelin et al 2021, jointed rock masses , slope instabilities (Iannucci et al 2018, Dietze et al 2020, and the acceleration of clayey landslides (Mainsant et al 2012, Bièvre et al 2018, Fiolleau et al 2020.…”

Structural Characterization of a Toppling Rock Slab From Array‐Based Ambient Vibration Measurements and Numerical Modal Analysis

“…Advantages of this technique include non‐invasive, surface‐based sensor deployment, short‐term data acquisition, and rapid analysis of spectral attributes. Meanwhile, advancements in seismometer technology and the increasing availability of low‐cost instruments (Anthony et al., 2019; Ward & Lin, 2017) have improved the viability of ambient vibration measurements for rock slope instability characterization and monitoring across a range of settings (Bottelin et al., 2021; Colombero et al., 2021; Jongmans et al., 2015).…”

“…in seismometer technology and the increasing availability of low-cost instruments (Anthony et al, 2019;Ward & Lin, 2017) have improved the viability of ambient vibration measurements for rock slope instability characterization and monitoring across a range of settings (Bottelin et al, 2021;Colombero et al, 2021;Jongmans et al, 2015).…”

A Comparative Analysis for Defining the Sliding Surface and Internal Structure in an Active Landslide Using the HVSR Passive Geophysical Technique in Pujilí (Cotopaxi), Ecuador

“…The geological materials must exhibit a high-level elastic parameter contrast to establish f o in a two-layer model (sediment-rock or a soft-soil layer over a compact or cemented half-space), meaning a marked difference in seismic impedance must characterize them. Currently, the HVSR technique is recognized for setting f o and fundamental periods of the ground [41][42][43][44][45], defining sediment thickness [18,19,46], and studying soil-structure interactions [15,47].…”