The hydraulic conductivity is a key parameter to evaluate for characterizing the road construction materials. Extensive database studies on hydraulic conductivity of different types of road materials have been performed using three databases: FG/KSAT-1358 for fine-grained soil, CG/KSAT/7/1278 for coarse-grained soil, and AC/k-1624 for asphalt concrete mixture. The best fitted probability density function for the key parameters in each database were examined using the ‘Akaike Information Criterion’. It is shown that the ‘loglogistic’ distribution is the best probability density function to describe the variation of most key parameters from all three databases. Hydraulic conductivity predictive parameters for each material have been examined using the established databases. The analysis revealed that the most favourable predictors are air void percentage together grading entropy for asphalt concrete, void ratio together with specific surface for coarse-grained soil, and water content ratio for fine-grained soil. Transformation models have been developed using the key prediction parameters. The influence of other factors (e.g., test type, soil classification, sample condition) were studied in data subsets analysis and revealed generally modest influences on the calibrated transformation models. Laboratory investigation on the freeze-thaw effect on the established transformation model and other pertinent parameters has also been performed on four fine-grained soil sample series. The variation in soil index parameters over an increasing number of freeze-thaw cycles has been examined, the results showed that the liquid limit and the compression coefficient exhibited a systematic gradual decreasing over increasing number cycle for all sample series. The effectiveness of water content ratio as a hydraulic conductivity predictor for soil experienced multiple freeze-thaw cycles has been investigated, the results indicated that the transformation model developed from the database studies remain sufficiently accurate for freeze-thaw conditioned samples, liquid limit measured at the same conditioning state (i.e., number of freeze-thaw cycles) is required for better prediction.
Hydraulic Conductivity of Road Construction Materials: with a focus on freeze-thaw effects
Feng, S. (Author). 12 May 2022
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)