Failure mechanisms and stability analyses of granitic boulders focusing a case study in Galicia (Spain)

Granitic boulders are widespread geomorphological elements, particularly found in humid granitic areas. Although they seldom represent a hazard for people or infrastructures, sometimes their location in steep or natural slopes may jeopardise their stability and potentially affect people or infrastructures. In addition, their complex geometry makes the instability mechanisms difficult to identify, so it is even more difficult to compute factors of safety regarding their stability. In this paper, the authors analyse potential failure mechanisms of granite boulders based on analytical mechanic calculations and physical tilt tests, permitting understanding the phenomena under scrutiny. Then, they study the stability of one of these boulders: the Pena do Equilibrio or equilibrium rock. To do that they resort to standard geotechnical characterization and advanced geometrical characterization derived from UAV photogrammetric and 3D Laser Scanning of the boulder. The presented results exemplify how the application of these recently available topographic technologies, in combination with rock mechanics approaches, enable a rigorous analysis of the stability of granite boulders

Validation of Solid-State LiDAR Measurement System for Ballast Geometry Monitoring in Rail Tracks

The inspection and maintenance of track ballast are fundamental tasks for the preservation of the condition of railway networks. This work presents an application based on a low-cost solid-state LiDAR system, which allows the user to accurately measure the ballast geometry from a mobile inspection trolley or draisine. The solid-state LiDAR system, the LiVOX Avia, was validated on a test track through comparison with a traditional static LiDAR system, the Faro Focus 3D. The results show a standard deviation of around 6 mm for the solid-state LiDAR system. The LiVOX system also provides the capability to measure the ballast digital elevation model and profiles. The LiVOX results are in agreement with those obtained from the Faro Focus. The results demonstrate that the LiVOX system can sufficiently measure even the displacement of a single layer of ballast stones typically between 2.5 cm and 5 cm. The data provided can be easily digitalized using image processing tools and integrated into geographic information systems for infrastructure management

A multi-approach rockfall hazard assessment on a weathered granite natural rock slope

After a recent forest fire, a weathered granite rock slope located in the northwest of Spain may become increasingly susceptible to rockfalls. This study presents a multi-approach assessment of rockfall hazard, with some features deserving particular attention. First, the geomorphological context represented by a weathered rock mass with multiple dispersed blocks presenting various potential instability mechanisms. Secondly, the presence of a hillfort behind the slope and a small village at its toe, limiting the available solutions for rockfall protection. Finally, the combination of different remote sensing techniques (unmanned aircraft system topography and light detection and ranging) with a semi-automatic geostructural analysis has been successfully applied to obtain both a 3D point cloud of the wide area under study in addition to an estimation of mean block volume for rockfall simulations. Additionally, the design and implementation of a protective measure (rock dynamic barrier) have been addressed