Using the Intensity Values from Terrestrial Laser Scanner (TLS) for Determining Lithology of Flysch Rock Mass in Southwest Slovenia

Abstract

Heterogeneous rock mass, such as flysch is represented by individual lithological units with different geomechanical parameters. The heterogeneity of the rock mass affects its geotechnical behaviour, which causes difficulties in slope stability, as well as in underground construction. Development of modern ground-based remote sensing techniques, enables measurement and positioning of distant objects. Terrestrial Laser Scanner (TLS) has been in the past years successfully integrated in acquisition of geological features. In case of pulsed TLS, the scanner emits short pulsed beam of light and measures the time-of-flight from reflected object surface in order to compute the distance from objects. The resulted point cloud is georeferenced in the post-processing phase. Terrestrial Laser Scanner also records the intensity of reflectance, which depends on the properties of the scanned surface. Flysch rock mass can be followed in SW Slovenia, therefore a lithology profile in quarry Elerji was chosen to test the applicability of TLS in characterising the heterogeneous rock mass. The selected quarry wall was lithologically logged and scanned with TLS. Some samples along the profile have been collected for X-ray diffraction analysis of minerals. The analysis of point cloud included the examination of differences between intensity values for individual lithological units and determination of parameters, affecting the value. The resulted intensity intervals for sandstones and marlstones have been empirically tested on the same profile with relatively positive results. Findings and further analysis would help geologists determine the general engineering geological properties of flysch rock mass in the field, as well as geomechanical conditions for faster and more accurate decisions in providing support types in underground construction, defining slope stability and long-term solutions for stabilisation of rock wall.