We studied bearing capacity of forest thoroughfares, constructed in Slovenia between 2000 and 2010. Skid trails were unpaved while roads were paved with bearing and wearing courses that together consist pavement structure. We mastered civil engineering procedure for spot field investigation of bearing capacity on gravel roads. Carriageway bearing capacity has been analysed in 2009 on 18 thoroughfares with dynamic loading plate procedure and dynamic deforming module (Evd). With dynamic plate ZGF02 we measured bearing capacity of relevant categories of forest thoroughfares in Slovenia in all construction phases and road uses except during winter frost. The lowest values have been measured in spring on new skid trails at embankment rut (15 MN/m2) and the highest on old primary roads during dry period in summer (172 MN/m2). Bearing capacity of the embankment rut has been significantly lower from the rut on excavation side of the carriageway but only on secondary roads on mixed base. The aggregate sizes for wearing course have been found adequate, and inadequate for bearing courses. On secondary roads the bearing capacity was higher on lime base than on mixed base. There the average bearing capacity was in spring 42 MN/m2, in summer 88 MN/m2 and in autumn 54 MN/m2. On primary roads the average bearing capacity was in spring 54 MN/m2 in summer 125 MN/m2 and in autumn 78 MN/m2. One year traffic monitoring on two primary forest roads with radar traffic detector found 18000 vehicles, mainly personal cars. The calculated traffic annual loading for primary forest road ʺRavnikʺ is 88606 NAL. This is light traffic loading according civil engineering standards. All year bearing capacity measurements have not proven detrimental short term impacts of the traffic on road bearing capacity and transverse evenness. Bearing capacity of the skid trails on lime base in dry season have been lower that on secondary roads on mixed base in spring time.
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