Abstract
Moisture content and stress state, which includes the effects of matric suction for unsaturated soil, exert a significant effect on the resilient modulus (MR) values of fine-grained subgrade soils. The moisture content and, consequently, matric suction vary periodically in subgrades in response to seasonal variation. The relationship between MR and matric suction is investigated through repeated load triaxial testing on fine-grained soils to obtain MR values and evaluation of the soil–water characteristic curves (SWCCs). The SWCCs, which represent the relationship between suction and degree of saturation, were evaluated with a combination of axis-translation and chilled-mirror hygrometer techniques to allow SWCC representation across the entire range of saturation. The plasticity index (PI) had a significant impact on the matric suction–water content relationship such that the SWCC shifted to the left as the soil PI decreased. The test results indicated a significant relationship between MR and matric suction. The results also were used to analyze the relationship between MR and moisture, which showed that the degree of saturation was superior to gravimetric water content in its ability to capture the effect of moisture variation on MR values. A modified constitutive MR-matric suction model was proposed to capture the effect of moisture variation on MR while accounting for the stress state of unsaturated soils. The proposed model performed better than existing models in reducing the number of regression constants and providing a better fit to the measured MR data.
Get full access to this article
View all access options for this article.