The safety of cable-supported tree harvesting was examined by researchers.
In conventional cable-supported forest operations, trees and their stumps are normally employed as anchoring elements to withstand high lateral forces. These loads, even if applied near the stem base where cross-section is larger, are characterised by higher magnitude and dynamic amplification effects. Consequently, failures of anchors due to overturning or stem breakage are possible. To evaluate the load-carrying capacity of anchors; processes similar to the techniques used for tree stability assessment were used for tree pulling tests, performed up to failure, on sound Norway spruce with medium-large diameter at breast height grown on mineral soil.
High-strength pulling equipment was designed and exploited to reproduce the loading conditions for trees used as anchors, while monitoring their movement. Low-cost sensors were used to monitor root-plate rotation during tree pulling tests. The obtained mechanical response of the tested trees was compared with the predictive statistical and analytical models available in the literature.
The main results confirmed the difficulty of giving a direct, sufficiently accurate and non-site-specific prediction on their load carrying capacity. Therefore, a method of normalisation of some of the easily measurable parameters that can be obtained through a non-destructive pulling test was used. A procedure, aimed at providing a more accurate assessment of the stability of anchors to help to reduce the number of accidents in cable-supported harvesting operations, is proposed in the research publication. The proposed method developed can be potentially applied in cable-supported forest operations. The recent advances in the technology of low-cost structural monitoring sensors make them suitable for monitoring cable-supported forest harvesting operations.
Although the results are still site-dependent, the normalisation procedure supported by on-site non-destructive measurements, allows a much more precise assessment of the safety of anchors than available methods.
The research was published in Biosystems Engineering, Volume 186, 2019. The research was titled “Safety assessment of trees used as anchors in cable-supported tree harvesting based on experimental observations”. The authors were L Marchi, O Mologni, D Trutalli, R Scotta, R Cavalli, L Montecchio and S Grigolato. Source