Tomi Kaakkurivaara, Nuutti Vuorimies, Pauli Kolisoja, Jori Uusitalo. (2015). Applicability of portable tools in assessing the bearing capacity of forest roads. Silva Fennica vol. 49 no. 2 article id 1239. https://doi.org/10.14214/sf.1239

Keywords: stiffness; light weight deflectometer; dynamic cone penetrometer; falling weight deflectometer; elastic modulus

Highlights: The dynamic cone penetrometer (DCP) and light falling weight deflectometer (LFWD) are useful tools for measuring bearing capacity; The measurement results are not same as with the falling weight deflectometer (FWD), but comparable.

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Forest roads provide access to logging sites and enable transportation of timber from forest to mills. Efficient forest management and forest industry are impossible without a proper forest road network. The bearing capacity of forest roads varies significantly by weather conditions and seasons since they are generally made of poor materials and the constructed layers may be mixed with subgrade. A bearing capacity assessment is valuable information when trafficability is uncertain and rutting is obvious. In this study, bearing capacity measurements were carried out using the light falling weight deflectometer (LFWD), the dynamic cone penetrometer (DCP) and the conventional falling weight deflectometer (FWD). The aim was to compare their measurement results in relation to road characteristics and moisture conditions. Data were collected from 35 test road sections in four consecutive springs and during one summer. The test road sections had measurement points both on the wheel path and the centre line. The data show logical correlations between measured quantities, and the study presents reliable regression models between measuring devices. The results indicate that light portable tools, the DCP and the LFWD, can in most cases be used instead of the expensive falling weight deflectometer on forest roads.

Kaakkurivaara, Natural Resources Institute Finland, Green technology, Kaironiementie 15, FI-39700 Parkano, Finland E-mail: tomi.kaakkurivaara@gmail.com
Vuorimies, Tampere University of Technology, P.O.Box 600, FI-33101 Tampere, Finland E-mail: nuutti.vuorimies@tut.fi
Kolisoja, Tampere University of Technology, P.O.Box 600, FI-33101 Tampere, Finland E-mail: pauli.kolisoja@tut.fi
Uusitalo, Natural Resources Institute Finland, Green technology, Kaironiementie 15, FI-39700 Parkano, Finland E-mail: jori.uusitalo@luke.fi

article id 366, category Research article

Lars Eliasson. (2005). Effects of forwarder tyre pressure on rut formation and soil compaction. Silva Fennica vol. 39 no. 4 article id 366. https://doi.org/10.14214/sf.366

Keywords: soil density; cone penetrometer; final felling; till soil

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In Swedish forestry, final felling is usually done by a harvester and a forwarder. These machines are heavy and the risk for rutting and soil compaction can be considerable under unfavourable soil conditions. The aim of this study was to evaluate effects of forwarder tyre inflation pressure on rutting and soil compaction after final felling. Three levels of forwarder tyre pressure were studied, 300, 450 and 600 kPa, after 2 and 5 machine passages. The first passage was driven with a 19.7 Mg harvester, and the second to fifth passages with a fully loaded forwarder totalling 37.8 Mg. Rut depths were not significant affected by tyre pressures but increased significantly with the number of machine passages. Soil density was significantly increased by 0.075 Mg m–3 by the harvester passage. Soil density increased significantly with increasing number of forwarder passages, and tyre pressure did not significantly influence this increase but the interaction between number of forwarder passages and tyre pressure was almost significant. Data suggest that density increases occur earlier in the 600 kPa treatment than in the other treatments. Only parts of an area harvested are trafficked in a normal harvesting operation. Outside the research area approximately 12.5 per cent of the area harvested was covered with ruts. On primary strip roads, which are heavily trafficked, soil compaction cannot be avoided by reducing the tyre pressure. On secondary strip roads, not passed more than once by the forwarder, a low forwarder tyre pressure may reduce soil compaction.

Eliasson, Swedish University of Agricultural Sciences, Department of Silviculture, SE-901 83 Umeå, Sweden E-mail: lars.eliasson@norraskogsagarna.se

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