Unbound Material Resilient Behavior due to Post Compaction –A study Comparing FWD and Tri-axial Tests

Abstract

Researchers have investigated deformation properties in unbound road materials for many years. Both laboratory tests and field measurements have been used and models have been developed. In the summer of 2003 a field test were carried out in the vicinity of town Uddevalla 90 km north of Gothenburg, Sweden. At the site, eight test cells were constructed, with different types of unbound layers. Four of the test cells were constructed with different material properties in the base layer and four of them with different base layer design on light fill material. A Heavy Vehicle Simulator test was carried out on all test cells. Other activities like a Falling Weight Deflectometer test were done prior to and after the accelerated loading test Laboratory tests like tri-axial were performed as well. Evaluation of stress sensitivity by using K-㮀 model shows an increase in stress dependent deformation behavior after permanent deformation occurred. These results are confirmed both from Falling Weight Deflectometer and tri-axial results. The relationship between the level of stress sensitivity and post compaction (permanent deformation) is evaluated and the same tendencies can be seen using either laboratory tri-axial tests or field testing. Thus, there is a potential for analyzing Falling Weight Deflectometer data at different load levels for predicting future rutting in unbound materials.