Abstract：In order to improve stabilities of concrete-filled steel tube ( CFST) pile of large diameter drill-hole in bottom corner of the roadway, the influences of admixture superfine fly ash, silica fume and steel fiber on the bearing capacity of concrete-filled steel tubular columns were studied. Orthogonal test combined with range analysis, variance analysis and comprehensive analysis was carried out to determine optimal combination of admixtures. The results showed that three combinations ( i. e. ultra-fine fly ash, silica fume and steel fiber) could improve the strength of core concrete. The strength of core concrete reached maximum value when content of ultra-fine fly ash, silica fume and steel fiber was 20%, 10% and 1% respectively. ANSYS simulation of CFST columns verified that the bearing capacity of concrete-filled steel tubular columns with admixtures was significantly improved.

Keyword：admixture;orthogonal test;concrete-filled steel tube column;bearing capacity;