To study the expansibility and mechanical property of expansive soil in natural state

a series of expansion and mechanical property experiments

were carried out on Nanyang weak expansive soil with different humidifying degrees under the same initial condition. Through the experiments

the following conclusions are drawn: with the increase of humidifying moisture content

both natural expansibility and loaded natural expansion rate gradually increased at first

then slightly reduced

and finally became stable step by step. Load-free expansion rate almost increased in linear manner in earlier stage

then gradually became stable. By shearing strength experiments of expansive soil with different humidifying degrees

linear relation curve and relational expression between cohesion

internal friction angle and humidifying moisture content were developed. For completed projects

actual expansion property and shearing strength of expansive soil can be obtained by moisture content monitoring

which can be used to assess safety conditions of projects.