### Laser Scanner: Mechanical Characterisation of Rock Mass Discontinuities  
The mechanical properties of discontinuities are of primary importance, as they largely influence the mechanical behavior of the rock mass. Fast and reliable field measurements of the strength properties of rock hold significant practical importance in rock engineering [10; 11]. Many authors have proposed new techniques to predict the strength parameters of rock mass [12; 13; 14]. The superficial portion of any rocky material exhibits lower strength characteristics compared to those measured within the intact rock due to physical and chemical weathering processes that propagate internally with progression [15]. These processes depend on the porosity of the material and the presence of micro-cracks or micro-fractures of varying extent. Even minor weathering can lead to a decline in rock strength, specifically joint compressive strength (_JCS_), which primarily occurs along discontinuity surfaces in outcrops. This characteristic can be measured in the laboratory through direct shear tests on samples taken from the joints. However, the difficulty in its determination is often influenced by textural anisotropy and the inability to obtain representative samples, especially in the presence of large-scale variations. Indirect tests, such as estimation using the Schmidt hammer and point load tests, are commonly employed to estimate the _JCS_. The Schmidt hammer rebound hardness test, developed in 1948, is a straightforward and non-destructive method initially designed for a rapid assessment of Uniaxial Compressive Strength (_UCS_) [16]. Over time, it has been further adapted to gauge the hardness and strength of rock [17; 18]. The recorded rebound height of the mass (\(r\)) on a linear scale provides insight into the strength characteristics of the tested material. The most recent research suggests that a new technique based on the use of laser scanning may allow assessment of characteristics such as the status of surface discontinuities, which is known to affect the shear strength of discontinuities. Assessing the ratio between the energy of the reflected ray and the one emitted by the instrument, called \"reflectivity (\(l\)),\" makes it possible to obtain information on rock surface characteristics. The property of any surface to reflect electromagnetic radiation depending on its nature has suggested using this characteristic for assessments of the physical and mechanical parameters of materials. For example, through the digital processing of images and reflectivity values obtained from laser scans, it has been possible to correlate reflectivity with the content of clay minerals in rocks [19; 20]. The reflectivity depends on the characteristics of the material constituting the surface under survey and the wavelength of the light signal. The reflectivity recorded during the scan could, therefore, provide information about the textural characteristics (micro-fractures, micro-roughness, porosity, alteration) of the rock and the decay of lithtic materials. Each element of the terrain reflects, absorbs, or transmits incident energy at different wavelengths, depending on its chemical-physical and structural characteristics (spectral signature). These considerations form the basis of techniques developed for recognizingsurfaces using methods typical of remote sensing. If it is possible to explore, at various wavelengths, the light reflected from a surface and there is a sufficiently extensive statistical record of spectral behavior, it is then possible to identify the nature of the investigated object [21]. The spectral reflectance of terrains is primarily controlled by water content, organic matter content, grain size, iron oxide content, mineralogy, and structure [22; 23]. The comparison between the spectral signatures of known soils and/or reference minerals allows for qualitative assessments of the properties of soils that have not been investigated yet [24; 25].