Resilient behaviour of unbound granular materials through repeated load triaxial test: influence of the conditioning stress

Abstract

The present paper reports the results of a laboratory investigation aimed to investigate the resilient behaviour of unbound granular materials (UGMs) for pavement unbound layers under repeated triaxial loading. The first part of research was focused on the effects of stress history, in terms of loading conditioning phase and stress paths, on the resilient response of the investigated UGM. The obtained results highlighted that the samples that experienced several stress paths after an initial stress conditioning showed reduced resilient moduli as well as higher stress dependency of the resilient properties as compared with samples not subjected to any specific stress history. The second part of research aimed to evaluate the influence of the conditioning stress level on the resilient modulus. The results showed poorer resilient characteristics along the several stress paths as the selected conditioning stress increases. Whereas, a sort of "loading memory effect", resulting in a similar mechanical behaviour, can be recognised as a similar stress state between conditioning phase and subsequent stress path is considered. The study confirms the high dependency of the resilient response of UGM on the stress condition and in particular, the main role of conditioning confining pressure on the stable mechanical behaviour of these materials is highlighted. Finally, a simplified approach that would allow the intrinsic resilient properties of UGM to be predicted for a specific combination of conditioning stresses and stress paths is proposed.

Influence of Degree of Saturation (DOS) on Dynamic Behavior of Unbound Granular Materials

“…Using the UGM specimens with moisture contents below OMC, Arulrajah et al [47][48][49] and Soliman [50] pointed out that the resilient modulus and the resistance of the plastic strain of UGMs under repeated loads declined with the increase in DOS. Zhalehjoo et al [51] and Cerni et al [52] also illustrated that the resilient modulus of UGMs declined with the increase in DOS under varied bulk stresses. Austroads [53,54] describes that the growth of traffic loading and the prediction of extreme weather should be the main requirement of the quality and strength characteristics of UGMs.…”

Investigation of Resilience Characteristics of Unbound Granular Materials for Sustainable Pavements

“…Another previous finding is that under less load cycle, the resilient modulus dominates the permanent deformation [31]. The results of a recent study suggested that axial load, material type, and the maximum particle size are required to be considered for the investigation of confining stress and resilient modulus [32].…”

Rutting Prediction Model of Asphalt Mixture Based on the Triaxial Repeated Load Test

“…e reports from NCHRP (the National Cooperative Highway Research Program) and SHRP (Strategic Highway Research Program) recommend the dynamic modulus test, triaxial static creep test, and triaxial repeated load test to assess the rutting resistance of asphalt mixture [10,11]. G. Cerni put forward a simplified method based on the triaxial repeated load test, which can accurately predict the material characteristics by adjusting the combination of stress and applied stress direction [12]. Park verified the effect of temperature on asphalt mixture by the triaxial repeated load test and predicted the relationship between temperature and rutting by the temperature conversion factor [13].…”