In order to ensure the execution of forestry works in deep peat conditions and particularly difficult, JSC “State Forests of Latvia” (LVM) applies an innovative technical solution not previously used in LVM practice for the construction of a section forest road – support of the road surface on logs.
In Limbaži forest district of Rietumvidzeme region, in the territory of the rural territories of Brīvzemnieki and Braslava in the municipality of Limbaži, construction of the “Tēvgāršas ceļa turpinājums” forest road is currently underway. The total length of the road is 1.6 km, and a section of 550 meters long is expected to be built in deep peat conditions with an intermediate layer of sapropel.
“In the construction design developed in 2018, technical solutions to improve the durability of the road using a log deck have been incorporated. The construction works started in 2019 have shown that such solutions cannot be implemented in the particular conditions of unstable soils. Therefore, the construction design was revised, incorporating a technical solution not previously used in LVM practice but used in other countries – the use of round wooden piles to overcome unstable soils. The construction design provides for supporting the roadway over a 500-meter-long section on round wooden piles, which have been driven into the ground according to a precise pattern. In this case, it is a triangular pile placement scheme, where the distance between the axes of the piles is 1 meter, ”explains Jānis Upens, forestry infrastructure manager of the LVM Vidzeme region.
The piles for the construction of the road section are made of conifer saw logs 5.4 meters long and 4.2 meters long with a thin end diameter of 20-24 cm. With an excavator and a special threshing head, the piles are driven into the location provided in the construction design.
To ensure the bearing capacity of driven piles, the piles are loaded at random. The loading results are convincing – the load capacity of the piles is 6-10 tons, which exceeds the load capacity of the designed piles provided in the construction design.
Work on the site is relatively fluid. The stakes had already been driven over a 320-meter-long section of the road until the ditch was crossed. The contractor begins to build a sand cushion in a particularly resistant geotextile.
In addition to the construction work, a research project led by the LVM Development Unit is being carried out on monitoring the use of the pile solution in forest road construction work. The research is carried out by a project group of the Forestry and Wood Products Research and Development Institute. As part of the research project, measuring equipment and instruments will be installed near the forest road “Tēvgāršas ceļa turpinājums”, which will collect information on possible horizontal and vertical deformations of the structure, groundwater levels, road structure and truck. pressure on wooden piles, as well as other measures. The results of the development project and the experience of the upcoming construction works will be used by LVM to select technical solutions for the construction of forest roads under particularly difficult conditions, thus surpassing the locals with very low carrying capacity.