Abstract:

This research is carried out to improve the expansive soil subgrade of the first-class highway from Xiaoxita to Yaqueling in Yichang city. Different amounts of weathered sand were mixed in expansive soil samples to investigate the expansive soil’s free swelling ratio, unloaded swelling ratio, loaded swelling ratio (25kPa and 50kPa) and expansion force. Through heavy compaction test and comparison of swelling rates, it’s found that adding weathered sand changes the water content and compaction of expansive soil, and hence restrains the expansion. The free swelling ratio of expansive soil mixed with weathered sand is less than 35%, which meets the requirement of subgrade construction. Different ratio of mixed sand to soil has different effect on the expansion when the mix ratio is 10%, the free swelling ratio and expansion force decrease most remarkably; when the ratio is 40%-50%, the swelling rate under 25kPa loading changes most evidently; when the ratio is 30%-40%, the swelling rate under 50kPa changes by a biggest margin; when the ratio is 40%, the increase of load can well control the expansion. The amount of weathered sand has slight influence on unloaded swelling ratio. It’s concluded that the expansion of expansive soil mixed with 10% weathered sand could be restrained most rapidly and economically.

Key words: expansive soil , weathered sand , free swelling ratio , non-loaded swelling ratio , loaded swelling ratio , expansion force