Evaluation on the Stability of Tree Used as Anchors in Cable Yarding Operations: A Preliminary Test Based on Low-Cost MEMS Sensors

Most of the fatal injuries that occur in cable yarding operations are related to both breakage of the skyline or failure of its anchoring system. The high forces, necessary to provide a cable path that consent an efficient transportation of the logs, are dynamically amplified by the oscillation of the moving mass (in case of fully suspended loads) and by the sudden accelerations applied to the carriage when ground obstacles are encountered (in case of semi-suspended loads). Due to the lack of effective methods that predict the actual load carrying capacity of such anchoring solution, there is the need to verify the possibility to define a system that assesses the failure of the tree used as anchors due to overturning. As a consequence, the present work aims to apply the knowledge of tree stability assessment to the case of anchors in cable yarding operations. Comparison between data on tree assessment of experimental pulling tests that simulated failure of the tree used as anchors due to uprooting and data collected from direct field measurements by MEMS sensors on tree used as anchors during real cable operation are made. The correlation between the two sets of data is made in order to develop an assessment technique, based on continuous monitoring, that guarantee a better level of safety of the anchors than actual empirical methods.