Talking the strong expansive soil of Guangxi as research object. 30 days evaporation experiment was respectively carried out for expansive soil with on without vegetation cover and under plastic sheeting cover

to explore the influence of continuous evaporation process on moisture-heat behavior and fissures development. The results show that without vegetation cover

the surface soil amount and rate of volumetric water content changes respectively are 7.38% and 0.17%/d; with vegetation cover

which are respectively 5.29% and 0.07%/d; apparently under vegetation cover

whose dehydration content and drying rate were less than that of without vegetation cover. For plastic sheeting cover

expansive soil evaporation is curbed and no water loss. Without no vegetation and plastic sheeting cover

the average temperature changes of expansive soil are 7.36 ℃，9.72 ℃ respectively

which is 5-8 ℃ higher than that with vegetation cover 2.03℃; obviously

the vegetation cover reduces expansive soil temperature variation. Without vegetation cover

expansive soil fissure depth is up to 32 cm

which is closer to 28 cm influence depth of moisture-heat. Under vegetation and plastic sheeting cover

no apparent fissure carried out in the plane and vertical; vegetation cover and the state of evaporation curbed can prevent expansive soil fissure developing.