Influence of two types of flotation bogie tracks on the distribution of static vertical soil stress

Flotation bogie tracks are widely used to mitigate soil deformation when operating wheeled forest machines on soils with low bearing capacity. While all of these tracks have flat and wide cross members in common, there is considerable variety in cross-member shape. For two common types of flotation bogie tracks with similar basic dimensions but different geometry of the cross members, the distribution of static vertical soil stress was measured using foil sensors installed under a homogenous sand layer. Vertical stress distributions were captured for both track types and for bare tires as a reference, with three levels of static wheel loads tested in combination with three levels of tire inflation pressure. Both track types significantly reduced mean vertical stress by significantly increasing the stress-transferring area. The track type with completely flat cross members had a greater effect than the type having cross members with recessed lateral ends, and it was also more effective in reducing peak stress. While these observations under standardized and static conditions cannot be directly transferred to the conditions of real forest operations, they suggest that the efficacy of bogie tracks to reduce soil deformation largely depends on the proper choice of track type with regard to cross-member design.