Characterizing the Soil Resilient Modulus for Typical Manitoba Soils

Resilient modulus of unbound materials is a fundamental property that is required for pavement design and estimation of its remaining service life. This paper highlights efforts to quantify the resilient modulus of subgrade soils in Manitoba. The research has two main objectives. The first objective is to model the relationship between the resilient modulus and cyclic stress, confining pressure, moisture content and dry density for typical Manitoba subgrade soils. The second objective is to evaluate the effect of basic soil improvement techniques. The resilient modulus test is performed on three types of soils: silty sand (from central & southern Manitoba), sandy clay (from western Manitoba), and high plastic clay (from Red River Valley). Soil samples are prepared at four moisture contents and dry densities. The moisture contents were selected such that two moisture contents are on the dry side (below the optimum moisture content) and the other two are on the wet side (above the optimum moisture content), according to the Standard Proctor Compaction Curve. Each sample is subjected to sixteen loading combinations that constitute a range of cyclic loads and confining pressures. The values of resilient modulus obtained from these tests will be incorporated in the structural design of new pavements. These values will also be used as base values to evaluate the adequacy of basic soil improvement techniques.