Izvorni znanstveni članak
Designing Mobile Anchors to Yield: A Tension Relief System for Tail Anchoring
Ben Leshchinsky
; Oregon State University Department of Forest Engineering Resources and Management
John Sessions
; Oregon State University Department of Forest Engineering Resources and Management
Jeffrey Wimer
; Oregon State University Department of Forest Engineering Resources and Management
Milo Clauson
; Oregon State University Department of Wood Science and Engineering OR-97330 Corvallis USA
Sažetak
Cable yarding systems are a common method for transporting materials in mountainous terrain where environmental, safety or economic considerations do not permit ground-based methods such as skidding, forwarding or shovel-logging. Although effective in steep terrain, cable yarding requires anchored support for skyline and operating line operation. Furthermore, mechanized steep slope harvesting, which often uses cable assistance, also necessitates sufficient anchoring for large cable loads. These systems rely on a fixed anchor, or tailhold, to provide adequate line restraint for operation. Anchored guylines and skylines usually depend on available stumps or trees (Peters and Biller 1985). Where these are not available, mobile anchors such as bulldozers or excavators can be used. Mobile equipment anchors have an advantage of predictable resisting capacity, as opposed to trees and stumps, and may present a means of relieving excessive cable tensions in skyline systems without a catastrophic failure.
We present a design approach for skyline tension relief with a comparison to actual field data. The analysis demonstrates that exceedance of a mobile anchor sliding resistance results in movement, limiting maximum skyline tensions and subsequently reducing them after the anchor shifts forward. Other anchor types, like stumps, anchored deadmen and engineered anchors, do not have the tendency for gradual movement to relieve skyline tensions as failure is often catastrophic, resulting in higher and potentially dangerous cable tensions, and complete loss of cable tension at failure. For mobile anchors, a relationship between cable tension and length presents an efficient means of predicting the anchor movement to facilitate design of appropriate equipment setback. A comparison of an analytical approach based on cable tensions, cable lengths, and anchor capacity with instrumented field tests demonstrates that the use of equipment, as a primary or auxiliary anchoring system, can be effective and potentially safer when adhering to design constraints based on equipment, equipment placement and in-situ soil properties.
Ključne riječi
cable logging; artificial anchors; failure capacity; movement; design; skylines; mobile anchors; dynamic loading
Hrčak ID:
173827
URI
Datum izdavanja:
1.6.2016.
Posjeta: 834 *