Remote thermal detection of exfoliation sheet deformation

Abstract

A growing body of research indicates that rock slope failures, particularly from exfoliating cliffs, are promoted by rock deformations induced by daily temperature cycles. Although previous research has described how these deformations occur, full three-dimensional monitoring of both the deformations and the associated temperature changes has not yet been performed. Here we use integrated terrestrial laser scanning (TLS) and infrared thermography (IRT) techniques to monitor daily deformations of two granitic exfoliating cliffs in Yosemite National Park (CA, USA). At one cliff, we employed TLS and IRT in conjunction with in situ instrumentation to confirm previously documented behavior of an exfoliated rock sheet, which experiences daily closing and opening of the exfoliation fracture during rock cooling and heating, respectively, with a few hours delay from the minimum and maximum temperatures. The most deformed portion of the sheet coincides with the area where both the fracture aperture and the temperature variations are greatest. With the general deformation and temperature relations established, we then employed IRT at a second cliff, where we remotely detected and identified 11 exfoliation sheets that displayed those general thermal relations. TLS measurements then subsequently confirmed the deformation patterns of these sheets showing that sheets with larger apertures are more likely to display larger thermal-related deformations. Our high-frequency monitoring shows how coupled TLS and IRT allows for remote detection of thermally induced deformations and, importantly, how IRT could potentially be used on its own to identify partially detached exfoliation sheets capable of large-scale deformation. These results offer a new and efficient approach for investigating potential rockfall sources on exfoliating cliffs.

A linked geomorphological and geophysical modelling methodology applied to an active landslide

“…Both techniques are suited to site scale investigation and yield DEMs which can be used to estimate surface changes and generate modelling volumes in ERI. Terrestrial (or ground based) LIDAR is a well-established tool for monitoring rock falls and natural slope movements, be it through permanent monitoring solutions (Lingua et al 2008) or repeated surveys (Delacourt et al 2007;Guerin et al 2021;Palenzuela et al 2016;Rosser et al 2007). Recent advances in structure from motion (SfM) photogrammetry have yielded centimetric resolutions such that they are comparable to terrestrial LiDAR scans and both are suited to the purposes of ERI.…”

Identification of rock and fracture kinematics in high alpine rockwalls under the influence of elevation

“…Daily temperature changes affected the upper 0.21 to 0.42 m assuming a 12 h temperature cycle and a thermal diffusivity of between 1 and 2 mm s −2 typical for metamorphic rocks (Cermák and Rybach, 1982;Vosteen and Schellschmidt, 2003). These rock depths correspond to daily temperature cycles in rockwalls observed in previous studies (Anderson, 1998;Gunzburger and Merrien-Soukatchoff, 2011). On an annual scale, thermal changes affected 4 to 8 m, and, therefore, the entire instru- 4).…”

“…Current research highlights the role of mechanical weathering (Eppes and Keanini, 2017). Diurnal and seasonal ambient meteorological changes causing cyclic heating and cooling (Gunzburger and Merrien-Soukatchoff, 2011;Collins and Stock, 2016), wet-dry cycles (Zhang et al, 2015), freeze-thaw cycles (Matsuoka, 2001(Matsuoka, , 2008 or active-layer thaw (Draebing et al, 2014(Draebing et al, , 2017a) produce critical and subcritical stresses that propagate micro-fractures (Eppes et al, 2018;Draebing and Krautblatter, 2019). Several studies investigated the influence of thermal changes on rockwalls and demonstrated that sudden erosion by thermal shock (Collins et al, 2018(Collins et al, , 2019 and slow thermally induced propagation of fractures in alpine rockwalls (Hasler et al, 2012;Collins and Stock, 2016;Weber et al, 2017) continuously weakens rock and can trigger rockfall (Ishikawa et al, 2004;Collins and Stock, 2016).…”

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

“…The increasing interest in thermally-induced effects on jointed rock masses [17,[35][36][37][38][39][40][41] requires an improvement in the techniques for temperature field analysis to integrate traditional direct contact methods [14,42]. In this sense, IRT surveys support the quantitative study of surface temperature fields over rock slopes, deriving distributed maps at their external interface.…”