Evaluation of modulus for unsaturated compacted soils with post-compaction variation in matric suction

The modulus values with respect to various levels of matric suction and moisture content were evaluated using suction controlled resonant column and torsional shear (RC/TS) testing. In order to evaluate modulus values at predetermined matric suction levels more quickly, a volumetric pressure plate extractor (VPPE) was modified by combining it with the bender element. Field seismic tests on various levels of moisture content were also performed. Results showed that the tendency of in-situ modulus values with changing moisture content matched well with those determined by laboratory tests with the post compaction method using suction controlling. The database of the modulus with varying moisture contents for unsaturated compacted soils is under development and has been applied to the modelling of subgrade soil in the mechanistic and empirical pavement design method.