CHARACTERIZATION OF EXPANSIVE SOILS FOR AIRPORT PAVEMENT DESIGN

Characteristics of soil expansion combined with environmental conditions are responsible for differential heaving of airport pavement subgrades. Despite a large technical effort centered on the study of expansive soils, a rapid means of evaluating potential damage is not available. In this study, a reliable rapid method of categorizing expansive soils was sought. Three procedures are recommended: (1) measurement of bulk density change in natural soil clods, (2) determination of clay content or (3) determination of the moisture-suction relationship with particular attention to aggregation. Each of these procedures was developed through correlations with soil compressibility with respect to suction changes, gamma sub h. This is a fundamental characteristic of the soil and the best indicator of potential expansion. Actual activity depends on imposed loads, initial suction, and final suction. The major obstacle to satisfactory development of this system remains the relation between differential heave and airport pavement roughness. While this problem is to be addressed in future research, there is a present need for criteria. The most acceptable criteria found were categories developed for application to residential concrete slabs on expansive soils. The limitations of this system are recognized but accepted as the best presently available. (Author)