Xenon long-arc lamp is used to simulate solar radiation. Deferent radiation intensities are acquired by adjusting lampshade height. Sunshine state is acquired by controlling the illumination time. Single factor controlling condition is achieved by constant temperature and humidity environment. Then

moisture-heat coupling behavior and rainfall-evaporation effect of undisturbed expansive soil sample in solar radiation are studied. When solar radiation and rainfall occur

the moisture migration and temperature variation present different states. With the to-and-fro moisture migration

the shallow soil tends to the fractured and loosened. In the solar radiation

the amplitude of moisture content variation increases

which aggravates the fissure development. To expansive soil

the characteristics of swelling and fissure are inner being

and atmospheric action is incentive. The behavior of expansive soil is changed gradually in the exchange progress of moisture and energy between atmospheric and soil. The simulating device on solar radiation is used to study the moisture-heat coupling behavior and rainfall-evaporation effect of undisturbed expansive soil. And the experience in research could be applied to the study of other soil types. In view of the engineering properties of expansive soil

the quantitative analysis of moisture migration mechanism of expansive soil could be further developed in the influence of solar radiation.