Tierakenteen rasittuminen yli 76 tonnin HCT-yhdistelmien koekuormituksissa vuosina 2015-2018: Yhteenvetoraportti

This summary report presents the main results of the research conducted by Tampere University of Technology in 2015-2018 and the University of Oulu in 2018 on the loading effects of heavy vehicles to road structures. The specially examined issue has been the cumulative deformation and the possible pumping of water into the road structure caused by the loadings of consecutive axles when the road is located on a soft subsoil. The main measurement methods have been MDI-analyses (moisture damage index) from ground penetrating radar data and rut depth from laser scanner done by using RDSV survey van and the monitoring of deflections at the bottom of asphalt concrete layer using displacement transduces installed in the road structure. The loading vehicles keeping on the intended driving line have been monitored for example by using measuring mat with video shooting, laser distance sensors and high-accuracy GPS.

In addition to the main test results, the summary report contains main observations about carrying out the loading tests and selecting the test sites, as the results of all test loadings could not be utilized in the comparisons of the loading vehicles. Reason for that has been for example the too different initial conditions to make reliable comparison between the loading vehicles.

The main purpose of the researches have been to estimate whether the 14-axis loading vehicles cause more rutting than the 7-axis loading vehicles when the loading mass was equivalent in the same time based on the short loading tests carried out in 2017 and 2018. In the researches, the 14-axis loading vehicles did caused more rutting than the 7-axis loading vehicles on gravel and thin-paved roads located on soft, wet soils. On thick-paved roads, the 14-axis loading vehicles did not caused any more rutting than the 7-axis loading vehicles.

The driving lines of the heavy vehicles have a significant influence on the increase rate of rut depth. In spring 2018, rut depth could be reduced by varying of the driving lines at the Kyyjärvi and Simo test sites. Thus, with autonomous driving, part of vehicles could be steered to reduce rut, at least on straight road sections.

In addition, the measurements also showed that there was a clear increase in rut depth at the spots of the road structure where moisture increase has been observed in MDI (Moisture damage index) analyzes.