Resilient Modulus Variations with Water Content

This paper carefully examines the resilient modulus variations with water content for three subgrade soils—lean clay, clayey sand, and clayey gravel. For each soil type, four resilient modulus tests were performed at the following water contents: 2 to 3% dry of optimum, at optimum, 2 to 3% wet of optimum; and at full backpressure saturation. The backpressure-saturated samples were modeled at optimum and gained up to 6% moisture during saturation. The resilient modulus testing of the noon-saturated specimens was conducted according to AASHTO T307-99 and specific testing adjustments that were developed for the backpressure-saturated ones. After achieving saturation, the specimens were consolidated at a confining pressure equivalent to the stress level of pavement surcharge and then subjected to five levels of deviator stresses under undrained conditions. The test results were utilized together with in situ stresses in order to develop design curves for resilient modulus versus water content.