Resilient modulus variations with water content

Resilient modulus (M-R) variations with water content were carefully examined for three subgrade soils-lean clay, clayey sand, and clayey gravel. For each soil type, four MR 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 molded at optimum and gained up to 6% moisture during saturation. The MR testing of the non-saturated specimens was conducted according to ASSHTO T307-99 and specific testing adjustments 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 to develop design curves for resilient modulus versus water content.