THEORETICAL EVALUATION OF RUT DEPTH COMPONENTS CAUSED BY FOREST SOIL SHEAR AND COMPACTION.

The study aims to estimate rut depths components caused by soil compaction and its' shearing caused by forestry vehicles' impact. The study bases on theoretical methods of terramechanics. As a result of the calculations, the study estimates three components of the rut depth caused by wheeled and bogie-tracked forestry vehicles impact. In the case when wheeled forestry vehicles operate on a weak forest soil which bearing capacity is up to 0.04 MPa, the estimate of the rut depth component caused by the soil shear caused by the vehicle normal load is up to 59%; the estimate of the soil compaction component caused by the normal load is between 26-37%; the estimate of the component caused by tangential stress when the vehicle slips is between 4-15%. In the case when a wheeled forestry vehicle operates on a forest soil of a medium bearing capacity up to 0.1 MPa, the estimate of soil shear component caused by the normal load is between 42-59%, the compaction component estimate is between 23-36%, and the estimate of the tangential stress component is 18-22%. In the case when bogie-tracked forestry vehicles operate on a weak forest soil, the estimate of the rut depth component caused by the soil shear caused by the vehicle normal load is between 43-49%; the estimate of the soil compaction component caused by the normal load is between 38-45%; the estimate of the component caused by tangential stress when the vehicle slips is between 6-18%. In the case when a bogie-tracked forestry vehicle operates on a forest soil of a medium bearing capacity, the estimate of soil shear component caused by the normal load is between 20-42%, the compaction component estimate is between 36-56%, and the estimate of the tangential stress component is 22-24% of the total rut depth. The estimations are proposed to be used in modelling the ecological impact of timber harvesting and skidding. [ABSTRACT FROM AUTHOR]