Slope-Scale Remote Mapping of Rock Mass Fracturing by Modeling Cooling Trends Derived from Infrared Thermography

Abstract

The reliable in situ quantification of rock mass fracturing and engineering quality is critical for slope stability, surface mining and rock engineering applications, yet it remains difficult due to the heterogeneous nature of fracture networks. We propose a method to quantify and map the slope-scale geomechanical quality of fractured rock masses using infrared thermography (IRT). We use the Mt. Gorsa quarry (Trentino, Italy) as a field laboratory to upscale a physics-based approach, which was developed in the laboratory, to in situ conditions, including the effects of fracture heterogeneity, environmental conditions and IRT limitations. We reconstructed the slope in 3D using UAV photogrammetry, characterized the rock mass quality in the field at selected outcrops in terms of the Geological Strength Index (GSI) and measured their cooling behavior through 18h time-lapse IRT surveys. With ad hoc field experiments, we developed a novel procedure to correct IRT data in outdoor environments with complex topography. This allowed for a spatially distributed quantification of the rock mass surface cooling behavior in terms of a Curve Shape Parameter (CSP). Using non-linear regression, we established a quantitative CSP-GSI relationship, which allowed for the CSP to be translated into GSI maps. Our results demonstrate the possibility of applying infrared thermography to the slope-scale mapping of rock mass fracturing based on a physics-based experimental methodology.

Infrared thermography reveals weathering hotspots at the Požáry field laboratory

“…Indeed, LST has been identified as a proxy for properties such as porosity and parameters such as the compressive strength 12 , 15 – 17 . Therefore, landslide mapping through IRT campaigns has been attempted by interpreting thermal anomalies 4 , 18 , 19 , and assessments of cooling stages were found indicative of the presence of loosened material and open fractures. Advancements in sensor technology have enabled the installation of InfraRed Thermal cameras on Unmanned Aerial Vehicles, transitioning from static platform-based surveys to more dynamic assessments 11 , 20 .…”

Characterization of the Fels Landslide (Alaska) Using Combined Terrestrial, Aerial, and Satellite Remote Sensing Data

“…Recently, 3D and 2D datasets have been integrated, enhancing the amount and quality of geological, geomechanical, and hydrogeological data when analyzing rock slopes. In particular, infrared thermography (IRT) datasets, gathered in tandem with TLS datasets, have been used to investigate the degree of fracturing [16] and rock mass quality [17] within rock slopes. To a lesser extent, hyperspectral imagery has also been incorporated with 3D datasets to map lithological changes within quarry walls, exploiting the varied different spectral responses of minerals [18].…”

“…SAR and laser scanning techniques, although useful for characterizing rock slope deformation, are seldom used in combination. The limited number of applications described in the literature mostly employ ground-based sensors [17,29,30]. Donati et al [31] describe an innovative approach that combines SAR ST and ALS to characterize the components and magnitudes of the displacement vectors across the slowly moving Fels landslide in Alaska and to show how the displacement trend and plunge can be computed and used in the interpretation of the failure mechanism of the landslide.…”