CLIMATIC MATERIALS CHARACTERIZATION OF FINE-GRAINED SOILS

Characterization of the performance-related characteristics of fine-grained subgrade soils depends largely on the moisture and temperature regime in which they are found. This paper presents the results of a repeated-load testing program designed to produce some important materials properties for a variety of fine-grained subgrade soils. The materials properties characterized are compatible with a newly developed Federal Higwhay Administration computerized stress and distress analysis system, VESYS II, which represents flexible pavements as linearly viscoelastic layered media. Such characterization has not been done in previous studies. The materials characteristics presented in this study are resilient modulus, residual strain, and permanent deformation characteristics, all of which, as expected, vary with the number of load repetitions. The results, taken from repetitive load tests on three different soils having a range of clay contents of 20 to 70 percent, include the relation of the materials characteristics to mean stress, deviator stress, soil suction, clay content, and temperature. Because the equilibrium suction value of a subgrade soil beneath a pavement is relatied to the climatically controlled Thornthwaite Moisture Index, it is possible to infer under what conditions and in which parts of the United States special design considerations will be required for pavement structures that rest on the tested soils. /Author/