The effect of bogie track and forwarder design on rut formation in a peatland

ABSTRACT The effect of forest machinery on the rut formation on extraction trails is an important aspect of forest operations. The aim of this study was to compare how track design and vehicle configuration affects rut formation on straight and curved test trails with no slash mats on peatland. Rut depth was observed from five machine-track combinations on several test plots after several passes and two different trail configurations, straight and curve. The observations (N = 760) were modeled using a mixed model approach to include the variation between the combinations. The results show that rut depth decreases exponentially with soil shear modulus, increases linearly with the number of passes and is not affected with the trail section configuration. The overall coefficient of determination is R2 = 0.55. A first generation Ponsse Elk with Fomatec tracks (EFwo) showed the lowest rut formation, followed by a first generation Ponsse Elk with Fomatec tracks equipped with add-on track shoes (EFw), a Ponsse Buffalo with KOPA high flotation tracks (Kopa) and a Ponsse Elk 10 W with Olofsfors mixed tracks (E10W), while a Ponsse Elk with long wheelbase bogie and Olofsfors high-flotation tracks (LWB) showed the deepest rut formation. Vehicle dynamics on peatlands are still far from being fully understood and the paper highlights the complexity of the interactions of the variables studied while providing a valid modeling tool with applications in planning of forest operations and simulation.