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Abstract The purplish-red mudstone of the Badong group appears in large numbers in the highway from Yichang to Badong. When the weathering mudstone was used as the fillings of highway embankment，lots of engineering problems appeared，such as road bulges，shoulder of road gushing，the uneven settlement and the lower bearing capacity. In order to eliminate the undesirable properties of embankment soil，a modified experiment was conducted with lime，cement，fly ash. The compaction test，California bearing ratio(CBR) test，unconfined compression test，disintegration test by using self-made disintegration instrument and soil-water test were conducted to study the characteristics of improved soil. The microstructure of improved soil was scanned by environmental electron microscope. When the improvement effect was evaluated；the basic indices such as bearing ratio，unconfined compressive strength，expansion index were not only considered but the index of soil-water characteristics and resistance of disintegration were also tried to be analyzed. The results show that the expansion characteristics of purplish-red mudstone is eliminated by modified materials. The bearing capacity of the subgrade soil and unconfined compression strength are vastly improved. The characteristics of water stability and resistance of disintegration are also improved. The improvement effect of the improved soil mixed with cement is the best，the best cement proportioning is 5%. The improvement effect of improved soil mixed with lime is the better and the best mixing ratio of lime is 7%. The improvement effect of fly ash soil is the worst and the best mixing ratio of fly ash content is 11%. To increase the fly ash content may make the improved effect to be better.
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Received: 20 July 2012
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2013, Vol. 32 
