Search

In the lowland part of Croatia, heavy machinery such as forwarders is mainly used for the purpose of extracting wood from even-aged forest stands. According to the forest management plan, forwarders are used intensively in the winter period when the soil is mostly saturated with water and when their activity can cause significant damage to the soil. The aim of this study was to determine changes in soil characteristics as a consequence of the repeated passage of a loaded 8-wheel forwarder on silty clay loam type of soil. The research was conducted in an area where the forwarder usually works and in a way that did not significantly disrupt his normal workflow. The results indicate that during the study period the soil had a good bearing capacity and that the observed changes in soil characteristics (bulk density, total soil porosity, soil moisture, particle density, soil water retention capacity etc.) occurred as a result of breaking structural soil aggregates after soil compaction by multiple passes. Characteristic points (T) of equalized penetration curves indicate the compaction of the soil surface layer. Cone penetration index (CI) values did not show a proportional increase as the number of forwarder passes increased, although significant differences in their values with respect to the number of passes were found. Shear strength (τ) did not significantly increase with increasing the number of passes, but a statistically significant difference in the measured values was detected at the soil surface, which was not observed at a depth of 15 cm. Exceeding the rut depth limit of 10 cm occurred only after the 20th pass. Our results indicate that the soil at the harvesting site had a good bearing capacity during the study period.

Fuel consumption of forest machinery and vehicles depends mainly on terrain conditions, working methods, drivers’ skills, engine load under working conditions, engine speed, type and technical characteristics of the machine. In timber harvesting operations, fuel consumption is significant for both, economic (costs), and environmental issues (80-95% of exhaust emissions and soot particles are associated with fuel consumption). The objective of this study was to compare fuel consumption in two different forwarders and to analyse two different measuring devices for fuel consumption. Fuel consumption was measured on a 6-wheeled Valmet 840.2 forwarder and an 8-wheeled Valmet 860.4 during roundwood and energy wood extraction in winter period. A differential fuel flow meter and a fuel measuring probe were used for measuring fuel consumption as well as a Fleet Management System (FMS) for transmitting measured data. Fuel consumption was expressed in six different ways depending on the stage of the working cycle, time, travelled distance, load volume and load mass. Finally, both the advantages and disadvantages of the used fuel measuring devices were gained. The results indicated higher fuel consumption of the smaller Valmet 840.2 forwarder due to lower soil bearing capacity and longer extraction distances. For both forwarders, higher fuel consumption (expressed in l t-1 km-1) was observed while extracting energy wood due to its lower overall mass.