Volume 7, numéro 1, july 1995

EN :

Time and ergonomie studies were carried out for three excavator-based logging machines. A follow-up study of three excavator-based harvesters was conducted. The studies indicate that productivity was at the same level as that of Nordic specialized forest machines, and with a similar ergonomie level. The ground pressure exerted by the excavator-based harvesters varied from 30 to 52 kPa.

The ability of the machines to operate in the terrain was good, in rough terrain as well as in terrain with soft ground conditions.

These machines can also be used for ditch digging, scarifying, planting, and road building and maintenance. The machines then function more as attachment carriers than custom-built excavators. The relatively low investment cost in comparison with that of custom-built Nordic machines also reduces operating costs.

EN :

Virtually all of the public highway pavements in New Zealand are comprised of usually one or more coats of a sprayed seal over unbound granular layers. The standard New Zealand design and construction techniques are being applied to heavy-duty forest roads. Seal coats are an attractive economic alternative for low-volume roads but existing design procedures are inappropriate for the loadings that are experienced on the arterial forest roads.

The advantages and limitations of seal coat design with respect to forest roads are discussed in this paper. Experimental work which has been instigated to further the development of seal coat design, construction techniques, and specialized materials suited to the special requirements of forest roads sustaining heavy loads of up to 160 kN per single axle is described and discussed. Results of field trials thus far have shown that enhanced quality control during construction, reduced bitumen application rates, and use of polymer-modified bitumens are providing the required performance.

EN :

Wood harvesting operations were controlled in terms of financial expenditure and material flow at three related steps in the wood procurement system — logging, roadside inventorying, and transportation. Wood flow from sawtimber to available sawlogs in the mill yard was evaluated using the technique of dynamic programming. This program was successfully linked with data processing (input) and interactive interpretation procedures (output). The power of the algorithm was increased by implementing separable programming. In this model a nonlinear transportation function was linked to linear logging and inventorying functions.

The dynamic programming procedure was not as effective computationally as the Simplex procedure, but future trends in computer development can be expected to offer increasing computing capacity for dynamic procedures. Small tactical problems were solved more accurately as the model construction was closer to real-life systems. No interest rate effects on sawtimber allocation were observed in the sensitivity analyses conducted, but transportation allocation as a phase of material flow changed when the effect of varying volumes of logging was analyzed.

EN :

A number of people have studied the problem of measuring the multi-attribute influence derived from the presence of road networks in mountainous areas. I have briefly examined this concept within the framework of the analytic hierarchy process (ΑΗΡ). I assumed that this influence is a function of several factors. I considered three such supra-functional factors: (1) promote long-term sustainable forest production and resource protection; (2) improve comprehensive timber production infrastructure; and (3) improve settlement infrastructure in rural areas. I studied a multi-attribute benefit structure of forest road networks in the hierarchy form. By pairwise comparison matrix according to all the criteria of the proposed hierarchy, the final eigenvectors and the composite weights have been arrived at. The AHP-based approach should be repeated to identify the benefit structure of road network systems and to improve the development strategy in mountainous areas.

EN :

Comparative experimental studies offer possibilities for reducing the uncontrolled variation in time studies of forest work. However, the factor "Operator" has often been found to be very difficult to keep constant when working with different machines. Analysis of variance often indicates that an interaction between operator and machine reduces opportunities to make generalizations.

The objective of this study was to develop and test a method for analysing and correcting for operator-machine interaction effects in comparative time studies encompassing few operators.

A new variable "Adaptation" was introduced to describe differences in the operators' degree of adaptation to various machines. In the present study the numeric value of the variable was estimated from (a) previous experience, (b) the subjective feeling of adaptation by the operator, and (c) a standardized time study of loading from a pile.

Analysis of variance showed that differences in adaptation could explain the interaction effects in both loading and unloading. The remaining effects of the interaction between operator and machine were not significant.

The method seems to offer more possibilities to generalize and statistically validate differences, even when the number of operators is limited.

EN :

Logging safety is a continuing problem. Developing solutions to safety problems requires an effective model of how accidents are produced by the design of logging systems. Such a model for engineering improvements must integrate human, equipment, environmental, and social factors over sufficient time to include antecedent events and management decisions which precede accidents. Various industrial safety models are reviewed and their limitations and applications to logging safety discussed.

EN :

Road network design may involve selection of junction points, and a standard economic criterion can guide the initial paper location of these points. The junction point problem, in its elemental form, begins with three horizontal control points. These control points are to be linked at minimum total cost using linear road segments. Each road segment is characterized by a constant cost per unit length which may differ between segments. A mathematical optimization model has been developed for this problem. A decision algorithm for optimal network design is given and an example from the literature illustrates its application.