How heavy compaction influences the durability of cohesive forest roads in Sweden

Forest roads play a critical role in Sweden’s forest transportation network but are increasingly exposed to higher traffic loads and variable environmental conditions. Compaction is widely recognized as an important factor influencing the mechanical behavior of unbound road materials, yet its performance under field conditions on Swedish forest roads remains insufficiently documented. This pilot study evaluates the influence of enhanced compaction on the short-term structural response of a forest road test section in Trosa, Sweden. Two adjacent sections were constructed: one compacted using an 8-ton roller and one left uncompacted. Field measurements included lightweight deflectometer (LWD) testing to determine the dynamic deformation modulus (Evd), road profile measurements using rotating laser leveling, moisture content assessments, and visual inspections. Measurements were conducted during three phases: immediately after construction, after several months of environmental exposure, and after a controlled traffic simulation involving multiple truck passes. The compacted section consistently exhibited higher Evd values than the uncompacted section during all measurement phases, with average differences of approximately 20–24%. Profile measurements and visual observations generally indicated less deformation and more stable surface conditions in the compacted section compared with the uncompacted section. Moisture content measurements showed a negative correlation with Evd values in both sections, highlighting the influence of water content on the measured response. The findings suggest that enhanced compaction may contribute to improved short-term structural behavior of forest road materials under field conditions.