A laboratory study to address swell, shrink and strength characteristics of deep mixing treated expansive clays

Expansive soils, in general are considered detrimental in the field of geotechnical engineering due to their susceptibility to volume change in response to seasonal moisture fluctuations. One such potential problem areas include the surface roughness in pavements overlying expansive subgrades with the zone of moisture fluctuation (active depth) extending to greater depths. Such pavements usually experience differential heave, loss of riding comfort, a reduction of pavement service life and pose high maintenance costs that are experienced sooner than anticipated. Deep stabilization methods including soil replacement, grouting, auger cast piles and drilled shafts have proven ineffective with respect to both cost and practicality aspects.; In the current research, deep soil mixing technique was proposed as a potential solution to counter the shrink swell movements of the expansive soil. The current thesis investigates a laboratory deep soil mixing procedure to stabilize medium to high PI expansive clays. Hydrated lime and Type I/II Portland cement were used as binders. Free swell, linear bar shrinkage and unconfined compressive strength tests were performed on both control and treated soils. The affect of curing period, binder dosages and proportions were studied and the results were analyzed to make recommendations for field implementation.; Results show that the treated soils exhibited a considerable reduction in linear shrinkage and free swell at all dosages and lime cement proportions. Maximum strength enhancements were noted at increasing binder dosages and cement proportions in the lime: cement ratio. Increase in curing period from 7 to 14 days has resulted in a 30% increase in the unconfined compressive strength.; Further research is recommended at different water cement ratios (0.8 and 1.3) and increased curing periods to better understand the efficacy of deep soil mixing applied to expansive clays in situ.