TY JOUR TI INVESTIGATION OF THE TRACK FORMATION PROCESS AND ITS STABILITY DURING THE OP-ERATION OF FOREST MACHINES AND SKIDDING SYSTEMS ON THE SLOPES OF THE THAWED SOIL KW permafrost soils KW rutting KW forest machines KW logging KW slope forests JO Forestry Engineering Journal AU Kalyashov, V.A. AU Shapiro, V.Y. AU Grigorev, I.V. AU Kunitskaya, O.A. AU Grigoreva, O.I. AU Storodubtseva, T.N. PY 2021 IS 11 PB FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov