| Adopting selective solid media, 81 strains among 111 isolated ones werefound to have an effect on improvement of swelling soils, From the 81strains, a strain (named A9 temporarily) which was more effective onswelling-shrinking of soils was selected. Its biological characteristic, solidinoculant culturing and condition of improvement on expansive soils werestudied, the results showed that the colony of strain A9 was dotted, dry,bulged, Its spore was grey, which produced liposoluble yellow pigment; Ithad aerial and substrate mycelium, and Its aerial hyphea weremutilbranched; its conidia were eilipsoidal with spikes on the surface. Theresults of sequence and comparison of 16S rDNA of A9 showed that theconsistency and comparability with streptomyces sp. 3194 was 99.7％. StrainA9 was aerobe, unhalobiont, grew well on gauze No. 1 (GA), with5％(V/V)of inoculum of spore suspension that contained 1010 spores per ml,temperature of 30℃, initiatied pH 7.5, rotating speed of 120r/min, and itsbest biomass was got after cultured 72h. Solid inoculant of A9 with 1010 spores per gram of dry mediums, pH7.0, water content 40％, was inoculatedto the swelling soils specimen. Results of improving test showed the optimalcondition was pH7.5, temperature 30℃, water content of soil specimen 40％,inoculum amount 8％(W/W), culture time 14d, under this condition, thefree expansion rate could be reduced from 70％to 45.2％, reduction ratewas 35.43％. Some of the architectural parameters under the optimalimproving condition were measured, including unload and 50KPa-loadexpansion rate, swelling pressure, ratio of volume shrinkage, linearshrinkage and specific surface area, comparing with CK, effect onimproving different swelling shrinkages of expansive soils by Solidinoculant of A9 was confirmed.
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