Investigating Rock Mass Failure Precursors Using a Multi-sensor Monitoring System: Preliminary Results From a Test-Site (Acuto, Italy)

Abstract

In the last few years, several approaches and methods have been proposed to improve early warning systems for managing risks due to rapid slope failures where important infrastructures are the main exposed elements. To this aim, a multi-sensor monitoring system has been installed in an abandoned quarry at Acuto (central Italy) to realise a natural-scale test site for detecting rock-falls from a cliff slope. The installed multi-sensor monitoring system consists of: i) two weather stations; ii) optical cam (Smart Camera) connected to an Artificial Intelligence (AI) system; iii) stress- strain geotechnical system; iv) seismic monitoring device and nano-seismic array for detecting microseismic events on the cliff slope. The main objective of the experiment at this test site is to investigate precursors of rock mass failures by coupling remote and local sensors. The integrated monitoring system is devoted to record strain rates of rock mass joints, capturing their variations as an effect of forcing actions, which are the temperature, the rainfalls and the wind velocity and direction. The preliminary tests demonstrate that the data analysis methods allowed the identification of external destabilizing actions responsible for strain effects on rock joints. More in particular, it was observed that the temperature variations play a significant role for detectable strains of rock mass joints. The preliminary results obtained so far encourage further experiments

Thermal Response of Jointed Rock Masses Inferred from Infrared Thermographic Surveying (Acuto Test-Site, Italy)

“…Moreover, the quarry rock wall is characterised by heights ranging from few meters up to 50 m and a length of hundreds of meters. The rock mass is also intensely jointed: geomechanical scanlines and remote surveys using total station have been performed on the quarry wall and five joint sets were distinguished [ 55 ], a S0 (93/4; dip direction, dip) system, corresponding to the limestone strata, S1 (131/82), S2 (91/64), S3 (4/80) and S4 (198/86).…”

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

“…To study the long-term rheological behaviour of rock masses exposed to environmental forcings (such as rainfalls, wind, daily and seasonal thermal cycles) and evaluate their role in inducing instability, a multi-sensor monitoring system has been installed since autumn 2015 in the abandoned quarry that was selected as a Field Laboratory (Fantini et al 2017b). The quarry is located in the Acuto municipality 100 km SE of Rome and is characterised by a 500 m long and sub-vertical quarry front made up of Cretaceous limestone that reaches a height up to 50 m and was intensively pitted until the late 70 s. The monitored area is located in the NW sector of the quarry, where a 20 m 3 rock block jutting out from the quarry wall is separated from the quarry wall itself by a decimetric-wide sub-vertical joint.…”

“…The rock block has been instrumented with: (1) one thermometer for measuring the rock mass temperature installed at a depth of 8 cm from the free surface exposed eastward (sensitivity: 0.1 °C); (2) six strain gages (sensitivity: 1 μstrain) installed over the rock block on micro-joints; and (3) four extensometers (sensitivity: 0.01 mm) installed on the steeply dipping open joints that separate the rock block from the wall behind it (Fiorucci et al 2020). Additionally, the monitoring system is completed by a fully equipped weather station placed at the top of the quarry wall that is composed of an air thermometer (measurement range −40 °C/ + 60 °C), a hygrometer, a rain gage (sensitivity: 0.2 mm H 2 O, WMO standard) and an anemometer for determination of wind speed and wind direction (Fantini et al 2017b). Meteorological, thermal, and strain data are sampled each minute and collected by a digital data logger set up to acquire data every minute.…”

Comparison of Approaches for Data Analysis of Multi-Parametric Monitoring Systems: Insights from the Acuto Test-Site (Central Italy)

“…Five main joint sets (S0 to S4) were recognized: S0 (93/4; dip direction/dip), S1 (131/82), S2 (91/64), S3 (4/80), S4 (198/86) that predispose the rock mass to failure with rock planar and wedge slide, rock fall and rock topple mechanisms with respect to the quarry wall attitude (100/88) [66,67]. The joint roughness coefficient (JRC) and the joint compressive strength (JCS) of the main joint sets were also estimated using a standard Barton profilometer and a Schmidt sclerometer, respectively [68] and the values of the intact rock friction angle (φ b ) were attributed based on the tilt test [69] (Table 1).…”