Experimental study of lateral restraint effects on the potential heave of expansive soils

This paper investigates the capability of swell parameters, obtained under oedometer and triaxial loading conditions, to accurately predict the potential heave of expansive soils. The applicability of the oedometer and triaxial swell data was examined using the results of an instrumented field experimental station. The field behaviour was predicted using pressure, suction, and moisture heave prediction methods. When the results of the oedometer tests were used in the calculations, all three techniques markedly overestimated the field heave measurements. Contrarily, using triaxial swell parameters gave a satisfactory agreement between observed and predicted heave values. Comparison of oedometer and triaxial results, corroborated by back calculations of the field data, clearly indicates that the mismatch of observed heaves and predictions based on the oedometer data was primarily attributed to the fully lateral restraint conditions applied in the oedometer swell tests. Applying a correction factor to the heave estimated based on oedometer data, a reasonable agreement was achieved between the estimated heave and field measurements. The value of the correction factor was found to be dependent on the method of prediction. However, an overall average value in the order of one-third is considered not unreasonable for the three heave prediction methods considered in this study. This factor converts the volume change obtained from the oedometer data to a vertical heave, and it also accounts for the discrepancy between field and oedometer soaking conditions.