Assessment of the performance of a skid trail on a slope considering the reinforcing effect of a root-saturated soil layer under the interaction of the wheels of a forest machine

In many constituent entities of the Russian Federation, forest fund areas are located not only on flat terrain, but also on slopes of mountains, hills, and hilly ridge landforms. The operation of forest machines in such conditions is considerably more challenging than on flat terrain, and forests on slopes are particularly sensitive to the negative impact of machinery. As in flat forests, logging operations, silvicultural activities, and fire protection arrangements are necessary on slopes, which cannot be accomplished without the use of specialized forest machines. At present, wheeled forest machines based on tractor chassis predominate both in Russia and worldwide. Excessive impact of propellers on forest soils on slopes can lead not only to rut formation (as observed in flat forests), but also to slope collapse, creating an extremely hazardous situation for both personnel and equipment. The article theoretically substantiates the necessity of accounting for the soil reinforcement effect provided by tree roots when analyzing the interaction between a forest machine propeller and the movement surface on a slope. Based on experimental data, it has been established that the degree of saturation of the soil root layer with pine roots mu reaches 0.65% at an average trunk diameter of d = 0.3 m and a trail width of H = 4 m, while the increase in specific cohesion DeltaC reaches up to 70 kPa at mu = 1.0%. It is demonstrated that the presence of a root system (mu > 0.2%) transfers the edge part of the slope massif to a stable state (stability coefficient Ku > 1) and reduces the rut depth from 0.4 m to the standard value of 0.2 m. The rut depth is inversely proportional to the average diameter of trees near the trail: at d = 0.25 m or more, rut formation does not exceed permissible values. The performed research and assessments contribute to enhancing the reliability of predicting the operability of a skidding trail (technological corridor), as well as the reliability of predictive indicators for logging and reforestation operations in complex geotechnical conditions on slopes when using wheeled forest machines or skidding systems based on them.