Empirical Models for Permanent Deformation of Subgrade Soils from the Data Collected at the Pavement Subgrade Performance Study

A national pooled-fund study supported by 19 states, the Federal Highway Administration, and the U.S. Army Corps of Engineers was conducted at the Cold Regions Research and Engineering Laboratory (CRREL) of the U.S. Army Corps of Engineers in Hanover, New Hampshire. The study, titled the Pavement Subgrade Performance Study (PSPS), aimed to develop failure criteria and prediction models for permanent deformation in the subgrade soil that incorporate the effects of soil type and moisture content. Full-scale pavement structures were built with the same crushed stone base and asphalt concrete surface layers on top of five subgrade soils. The soils were placed and compacted at three in situ moisture contents: the optimum and two other contents above the optimum. The pavements were subjected to full-scale accelerated pavement testing. An extensive volume of response and performance data was collected in the study. This paper presents the development of empirical models for permanent deformation of subgrade soils from the data obtained in the PSPS study. It describes the data collected by CRREL for the PSPS project and the statistical analysis used to derive the models for predicting permanent deformation in subgrade soils. For each soil type and moisture content, the analysis estimated constants for three models existing in the literature, including the model incorporated in the mechanistic-empirical pavement design guide pavement design model. A new model for predicting permanent deformation in subgrade soils is also proposed.