Investigation of Unbound Granular Material Behavior Using Precision Unbound Material Analyzer and Repeated Load Triaxial Test

This study aims to investigate the mechanical behavior of unbound granular materials (UGM) the using precision unbound material analyzer (PUMA) and repeated load triaxial test (RLTT). Both single-size and mixed-size aggregate and two graded materials were used for multi-stage loading tests in this study. The confining stress, resilient modulus, and permanent strains of six granular materials were analyzed considering the effect of particle size on the performance of UGM. The results of PUMA tests showed that the confining stress became smaller with more large-size particles and denser structure. Resilient modulus was found to be sensitive to particle size when the axial load stress was greater than 40 kPa. The resilient modulus of high-density materials calculated from the variable confining pressure (VCP) model was greater than that from the constant confining pressure (CCP) model. The results suggested that axial load, material type, and the largest particle size needed to be considered for analysis of confining stress and resilient modulus. Without considering confining stress, resilient modulus might be underestimated for high-density materials but overestimated for low-density materials using the CCP model. The resilient modulus and permanent strains measured using the PUMA were similar to those measured using the RLTT in the range of 10 kPa to 20 kPa confining stress. The predicted permanent strains from the CCP model and RLTT had greater error than the predictions from the VCP model and PUMA tests compared to experimental measurements. The dynamic confining stress in PUMA tests was found effectively to simulate the actual loading condition of UGM in a pavement. Although RLTT and PUMA tests present consistent results for characterizing the behavior of UGM, the PUMA can provide more reasonable results for simulating confining stress and measuring resilient modulus.


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  • Accession Number: 01686446
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 7 2018 3:02PM