ABSTRACT

Cable logging is a common harvesting technique for steep slope conditions, despite the safety hazard for the operators, which is mainly related to failure of cables or anchor trees. The multiple factors that determine whether a tree should be considered as an anchor make it difficult to estimate the actual suitability of the anchor tree from a safety perspective during logging. To address this critical question, the mechanical response of natural anchors was monitored in nine cable logging sites using a standing skyline system. Different anchoring methods were observed, namely, tieback anchors, multiple in-line anchors and single tree anchors. Based on previous experience regarding tree stability assessment, an innovative continuous monitoring technique was applied at each research site. The mechanical response of the anchors was analyzed in terms of force-rotation curves, which summarize the effects of loads transmitted by the skyline. An elastic response was observed in nearly all anchors, but the magnitude of the rotation varied depending on the anchoring method and the applied force observed during the survey. Effects due to cyclic loading were analyzed in four of the case studies, and an apparent relaxation phenomenon at the root-plate system was observed. Finally, the research provides an estimation of the anchor’s stability with respect to their maximum theoretical resistance, evaluated from trees showing similar characteristics that have previously been tested. Results from these field measurements provide information that can improve guidance regarding the holding strength of anchors to current empirical methods and help ensure safety anchoring methods.

摘要

尽管对操作员存在安全隐患，电缆测井是陡坡条件下的常见收割技术，这主要与电缆或锚定树的故障有关。确定是否应将一棵树视为锚点的多个因素使从采伐期间从安全角度估计锚点树的实际适用性变得困难。为了解决这个关键问题，使用立式天际线系统在九个电缆测井现场对天然锚的机械响应进行了监测。观察到了不同的锚固方法，即系回锚，多列直列锚和单棵树锚。根据先前有关树木稳定性评估的经验，在每个研究地点均采用了创新的连续监测技术。根据力-旋转曲线分析了锚的机械响应，该曲线总结了天际线传递的载荷的影响。在几乎所有的锚钉中都观察到了弹性响应，但是旋转的幅度根据锚钉方法和勘测期间观察到的作用力而变化。在四个案例研究中分析了由于周期性载荷引起的影响，并且观察到了根板系统的明显松弛现象。最后，该研究提供了锚定物相对于其最大理论抗力的稳定性评估，该评估是通过显示具有类似特性的树木进行评估的，该特性先前已被测试。