Abstract：Experimental researches are comprised of inside experiments and field tests on improved expansive soil with lime(IESL) in test section of the new Hankou airfield. Inside experiments consist of general physical properties，impaction and swelling characteristics of natural，impacted and improved expansive soils. Some results are drawn，such as the impacted expansive soils are more expansible than natural expansive soils，not expansive soils but IESLs are filled in superstratum of roadbed；it is effective that expansive soils are improved with lime，optimal lime contents are 6% to 8%，different filling cannot be mixed because there are much difference in maximal dry density and optimal water content of IESL. Field tests include roller compacting of IESL，general physical properties and swelling characteristics of compacting IESL，load test with pouring water，resilient module and deflection of roadbed. Some conclusions are drawn，for example，if compactness of IESL can arrive at 95 percent or settlement of IESL can arrive gradually at stabilization on condition that lime and water content are controlled effectively；roller compacting number must be over eight times to loose filling thickness of 50 cm，and six times to 30 cm，when exciting force of roller is 450 kN；though swelling capacity of in-site impacted IESLs is very low，impacted IESLs still have shrinkage characteristic because of water reducing；and measures which prevent water from falling would be taken；the impacted IESLs have larger bearing capacity，intensity and water stability.
