Coupled consolidation model for negative skin friction on piles in clay layers

Abstract

Expansive soils swell on absorbing water and shrink on evaporation thereof. Because of this alternate swelling and shrinkage, civil engineering structures founded in them are severely damaged. For counteracting the problems of expansive soils, different innovative techniques were suggested. Stabilization of expansive clays with various additives has also met with considerable success. This paper presents, by comparison, the effect of lime and fly ash on free swell index (FSI), swell potential, swelling pressure, coefficient of consolidation, compression index, secondary consolidation characteristics and shear strength. Lime content was varied as 0%, 2%, 4% and 6% and fly ash content as 0%, 10% and 20%. A fly ash content of 20% showed significant reduction in swell potential, swelling pressure, compression index and secondary consolidation characteristics and resulted in increase in maximum dry density and shear strength. Swell potential and swelling pressure decreased with increase in lime content also. Further, consolidation characteristics improved. Compaction characteristics and unconfined compression strength improved at 4% lime and reduced at 6% lime.

Keywords:

• expansive soils
• swelling
• shrinkage
• lime
• fly ash
• secondary consolidation

Acknowledgment

The financial support received from the Natural Science and Engineering Research Council of Canada (NSERC) and Concordia University is acknowledged.