Bearing Capacity of Forest Roads on Poor-Bearing Road Subgrades following Six Years of Use

Abstract

The research was conducted on a forest road on the territory of the State Forests in Poland, in the Brzeziny Forest District, where eight test sections with a total length of 422 m were created with different pavement system on a low-bearing soil substrate (clay, silt loam) as part of the road reconstruction in 2016. The bearing capacity of the pavement was evaluated based on the static strain modulus ME MN·m−2 by measuring with a statistic plate (VSS), the dynamic deformation modulus Evd MN·m−2 obtained from lightweight deflectometer measurements, and the elastic deflection of the pavement Us mm evaluated from Benkelaman beam measurements. It has been shown that pavements made of crushed aggregate and common gravel on timber roller substructure maintain good bearing capacity parameters, where the average values of secondary modulus of strain are above 130 MN·m−2, and in the case of pine rollers, this modulus has increased. Pavements on low-bearing soils reinforced with willow brushwood mattresses have low bearing capacity parameters, with averages of 26.09 ≤ MEII ≤ 53.93 and 22.1 ≤ Evd ≤ 39.1 MN·m−2, but the technical condition of the pavement makes it possible to continue carrying out forestry-related transportation. The research confirms the possibility of reinforcing soils with poor bearing capacity with wooden rollers, and in the case of willow mats for roads with light truck movements.

Keywords

• VSS measurements
• lightweight deflectometer Evd
• pavement of road
• subgrade reinforced with timber logs
• willow brushwood mattresses