Evaluating a Model for Seasonal Variation of Silty Sand Subgrade Resilient Modulus with FWD Tests
(English)Manuscript (preprint) (Other academic)
The stiffness of unbound pavement material is one of the main input parameters in mechanisticdesign and analysis of pavement systems. This material property is usually moisture dependentand therefore, most of the unbound pavement layers exhibit seasonal variation in stiffness as thepavement moisture regime changes throughout the year. Therefore, this variation should be takeninto account in any realistic pavement design. In unbound materials with high fine content,change in moisture content can result in change in the stress state due to suction effects. In thisstudy, an enhanced predictive resilient modulus model that accounts for seasonal variation bymeans of suction measurement is presented. A silty sand subgrade was tested using a modifiedRepeated Load Triaxial (RTL) system under different moisture (suction) conditions and a set ofresilient modulus model regression parameters were determined. The capability of the model tocapture seasonal moisture variation effects was further evaluated using field data. A series ofFalling Weight Deflectometer (FWD) tests with multi-level loads were conducted on aninstrumented pavement structure where the moisture content of the subgrade was changed bymanipulating the pavement drainage condition. The resilient moduli obtained from the modelwere compared to the backcalculated stiffness data obtained from FWD tests conducted atdifferent moisture conditions. Overall, a good agreement was observed between thelaboratory-based resilient modulus and the backcalculated stiffness. The resilientmodulus-suction model could efficiently capture the moisture content effects.
Resilient modulus, backcalculation, falling weight deflectometer, seasonal variation, moisture content, silty subgrade
IdentifiersURN: urn:nbn:se:kth:diva-162084OAI: oai:DiVA.org:kth-162084DiVA: diva2:796852
QS 20152015-03-202015-03-202015-03-24Bibliographically approved