| The long term performance of a pavement structure is strongly dependent on the subgrade soil conditions. This is particularly true in areas experiencing seasonal freezing and fluctuations in moisture and temperature existing within and around the pavement structure. To account for the adverse effects of such factors on the structural adequacy of pavements, it is necessary to have available realistic and reliable strength measures for the layer component materials. With the resilient modulus as a key parameter in such an evaluation, the current study is aimed at investigating the seasonal variation effects of moisture and temperature on pavement bearing capacity as assessed by non-destructive and other appropriate laboratory test procedures.; The present study consists of two phases: a field investigation phase and a laboratory testing program. Within the scope of the field testing program, a pavement section representative of the primary highway system within the Province of Alberta, was selected and instrumented with thermal conductivity suction sensors. FWD deflection tests were conducted at regular time intervals over a period of two years, and at various locations within the instrumented section. Output from these tests coupled with temperature and suction measurements were used in various forms to establish a procedure for measuring seasonal variations in the structural strength of the subgrade soil.; The laboratory investigation involved extensive repeated load testing on remolded samples of the subgrade material taken from the instrumented site. Representative resilient modulus values, under different loading, temperature and moisture conditions, obtained from these tests were used to develop predictive moduli relationships.; Both field and laboratory phases produced unique and practical approaches for quantifying the influence of seasonal variations on subgrade strength. Although traffic induced stresses were found to be significant in effecting subgrade strength, the soil matric suction was found to be more influential.; In addition to the benefits gained from this current research project, a new and relatively inexpensive resilient modulus test system has been developed and is now operational. This system can be utilized in the future for developing mechanistic-empirical procedures for the design and rehabilitation of flexible pavements. |
