Prediction of resilient modulus of compacted saprolitic soils by CBR approach for road pavement subgrade: a re-examination

摘要

The scope of the study as presented in this paper is to re-examine the prediction of resilient modulus (Mr) by the classical California Bearing Ratio (CBR) approach, specifically for compacted saprolitic subgrade soils. Through the extensive experiments carried out for this research, a more precise model yielded to estimate M_R based on CBR values and the relative degrees of soil compaction. Likewise, comments are also made critically for the suitability of using the well-known models which were developed during the past decades. In addition to the core results, this study has produced a number of other important findings: (1) the influence of soil compaction densities on CBR and M_R is relatively significant when soil is relatively dry, whereas saturation ratio becomes a dominant factor while the soil is in wetter condition; (2) when the saturation ratio becomes dominant, the soil material could rarely reach a CBR of 5% or above, which was often regarded as competent materials by many design standards; (3) the moisture ratio (R_m) of the saprolitic subgrade materials is one of the useful parameters in estimating M_R and (4) the distinctive behaviours of saprolitic subgrade soils under CBR, unconfined compressive strength and repeated load tests are considered to be related to the degree of freedom of volume change for soil samples during the tests.