Characterization of Rutting (Permanent Strain) Development of A-2-4 and A-4 Subgrade Soils under the HVS Loading

As part of a national pool funded study 208 on pavement subgrade performance, 12 full-scale test sections (four soil types and three moisture contents) were constructed and tested under the heavy vehicle simulator (HVS) loading. This paper presents the HVS results on two of the four soils tested: AASHTO Class A-2-4 and A-4 soils, respectively. From the results, it was found that the pavement subgrade performance is a function of soil type, moisture content, and applied stress condition. Additionally, this paper also evaluated the current mechanistic-empirical pavement design guide (MEPDG) subgrade rutting (permanent strain) model through comparing with the actual measurements under the HVS loading. It was found that the MEPDG subgrade permanent strain model needs further improvement, and that a single performance model may not be universally applicable to different subgrade soil types. Consequently, a new permanent strain model for each soil type was developed in this paper, based on the HVS results, and that yielded better predictions. With further validation and field calibration, the proposed models offer promising potential to accurately predict rutting behavior of these two soils.