The effect of longitudinal slope, skid trail plan and passes of skidder Tof E655 on forest soil compaction (Case study: Bahramnia forestry plan)

The objective of this study was to investigate the effect of longitudinal slope, skid trail plan and passes of skidder Tof E655 on forest soil compaction in Bahramnia forestry plan. Initially, skid trails with upward and downward directions were selected and then classified into sections with moderate and severe traffic. Using polar and Nivelmen methods, the plan of route and longitudinal profile of route were drawn, respectively and fed into the AutoCAD software. The skid trails were divided into straight routes and horizontal curves in terms of plan and classified into 5-15, 15-25 and >25% for upward direction and 0-5, 5-15 and >15% for downward direction in terms of longitudinal slope were c. 228 samples was taken using metal cylinder for measuring soil compaction, porosity and moisture in the mentioned classes and control (forest). Findings showed that the soil bulk density increased with the increase of skidder passes and longitudinal slopes. The maximum soil bulk density was recorded for curves, severe traffic classes, and longitudinal slopes >25% (1.27 g cm-3 in upward skidding) and >15 (1.18 g cm-3 in downward skidding). The minimum soil porosity and moisture was also observed in this condition. In this study, the Civil3D 3D display was used for the first time to analyze the technical properties of skid trails and to determine the sampling locations. According to the results, to reduce the damage to the soil of skid trails it is necessary to avoid constructing spiral and steep routes and sever passes through them.