Volume 5, numéro 1, july 1993

EN :

Coillte Teoranta, the Irish Forestry Board, was established as a forestry company in 1989, with a mandate to operate in forestry and related activities in a commercial manner. The company took over the assets of the state Forest Service and now owns and manages approximately 400,000 ha of forest. Coillte harvests and sells timber to the private wood processing industries in Ireland.

Coillte harvested approximately 1.4 million m3 of timber in 1990. By 2010 this annual harvest volume will increase to 3.5 million m3. In order to manage the harvesting and transportation operations efficiently, a national timber sales allocation procedure was developed by the Forestry Department of University College, Dublin. The procedure uses Coillte's databases on harvest volumes, subdivided into supply categories; on mill demands, specified by demand categories; and on the national transportation network, including road, rail and water transport modes.

The developed operational procedure was used as a decision-making tool during the allocation of the 1991 sales volumes. A comparison of the actual versus the optimized 1990 allocation strategy identified opportunities for large-scale savings. In addition to its main function as a decision-making tool for the annual sales allocation, the model has been used for other strategic and tactical planning analyses, such as the influence of new mill location on transport costs, the impacts of a timber processing industry rationalization programme on the industry as a whole and on individual mills, the feasibility of timber transport by rail, the selection of suitable ports for timber export, and the impact of road construction and improvement programmes on national timber transport strategies. The model has been successfully linked with the company's ARC/ INFO Geographic Information System which extends the post-allocation analysis and interpretation capabilities, and combines the output with existing information systems. A further integration of the procedure in the management decision-making processes in the company will result in increased cost saving opportunities.

EN :

Production rates of cable yarding by fixed skyline in Southern Africa were found to be low, usually between 50 m3 to 60 m3 of timber per day on average. Investigations identified four major sources of lost productivity. Implementation of simple techniques selected to reduce losses resulted in a quadrupling of productivity though only a tripling is expected in the long term.

EN :

Small-sized mini-levers were compared to conventional levers in forwarder grapple loading of timber using a forest machine simulator in clear-cutting and thinning conditions. No effect on time consumption per burden was observed, but muscle constriction in the trapezius muscle measured using EMG was lower when the mini-lever option was used. Control errors were measured by counting the contacts between the remaining trees and the machine elements. These were interpreted to result in damage to the trees. The frequency of this kind of damages was significantly smaller when using the mini-lever option.

EN :

In Japan, the extent of man-made forests has reached 10 million ha. These forests were mainly established after World War II and are now at thinning age. Effective methods for thinning are being developed. In this paper the spacing of skid trails suitable for mini-forwarder with a grapple loading boom and a winch and mobile mini-yarder are discussed, mainly from the economic point of view. Results indicate that the skid trail spacing of about 40 m for the timber extraction with the mini-forwarder and about 140 m for the mobile mini-yarder.

EN :

Production rates and costs of three forest road construction machines (Ford County 1164 tractor, D4D and D6D Caterpillar bulldozers) were analysed and compared. Results showed that differences in production rates were attributed mainly by the type and the size of the machine, driver's working experience and the nature of the terrain side slope.

Compared to other subgrade productivity studies, machine production rates found in this study were considered to be reasonably high. The mean production rates for the D6D, D4D and the County tractor were 129.0 m3/h, 41.0 mVh and 28.1 mVh respectively. High productive time, easily workable soils and few obstacles encountered during earthworks operation were the major factors which contributed to high machine production rates.

Cost analysis showed that the higher the machine production rate the lower the subgrading cost and vice versa. The mean production costs for the D6D, D4D and the County were estimated to be US$ 0.49/m3, US$0.79/m3 and US$0.76 /m3 respectively. The estimated machine production costs were more or less the same as those estimated elsewhere.

Although low machine production cost is usually the criterion used in choosing the machine to be used for road construction works, this paper recommends that other factors be considered.

EN :

This research discusses the possibility of using woody constructions, for example retaining walls, based on the durability of used wood for strip roads under long-term use. Used woods having a reliable record were adopted as samples. Their durability was compared with that of fresh wood (as standard samples) by means of Brinnel hardness, compression strength and bending strength. Visually, three layers were seen from the dug-out round wood cross-section: a decayed sapwood, discoloured sapwood and sound heartwood. From the results of three tests it was confirmed that the heartwood was still sound in spite of 17 years of use.

EN :

Methodologies are developed for optimal road and landing spacing when considering roads and landing with surface dimensions. Example shows that the width of road and the size of landing do affect the solutions to optimal road and landing spacing.