降雨蒸发作用下膨胀土湿热和裂隙特性室内模拟试验

Laboratory model test on moisture-heat and fissure behavior of expansive soil under action of rainfall and evaporation

以广西白色强膨胀土为研究对象,对有、无植被覆盖的膨胀土样进行蒸发、降雨再蒸发试验,研究降雨、蒸发过程对膨胀土湿热和裂隙拓展特性的影响。结果表明,植被覆盖土样表面的反射量比无植被覆盖土样小100W/m2左右,土样表面温差小5～6℃。无植被覆盖土样经历降雨过程后,在相同蒸发条件下,土样表面裂隙率由1.28%增加到3.82%,表层土体累计脱湿量由3.42%增加到11.17%,脱湿速率由0.59%/d增加到1.44%/d,表层土体温度变化平均值由13.1℃增加到14.9℃。可见,降雨、蒸发过程使得土体水量变化加大,水分迁移速率增加,温度变化加剧,土体趋于破碎。植被覆盖土样经历降雨过程后,在相同蒸发条件下,土样表面并未出现明显裂隙,表层土体累计脱湿量由3.16%变为2.36%,脱湿速率由0.58%/d变为0.37%/d,表层土体温度变化平均值由0.58℃变为0.37℃。可见,短期降雨、蒸发过程对植被覆盖下膨胀土的持水能力影响不大。

Taking the white strong expansive soil of Guangxi as the research object. Laboratory model test for evaporation-rainfall-evaporation is respectively carried out for expansive soil with vegetation covered or not, to explore the influence of rainfall and evaporation process on moisture-heat behavior and fissures development. The results show that, the values of radiation and surface temperature of soil sample with vegetation covered are smaller than the ones of soil sample without vegetation covered about 100 W/m2, 5-6 ℃ respectively. After rainfall process and under same evaporation conditions, the surface fissure ratio of soil samples without vegetation covered increases from 1.28%to 3.82%. Moisture content changes of surface soil increase from 3.42%to 11.17%. Drying rate of surface soil increases from 0.59%/d to 1.44%/d. The average temperature changes of surface soil increase from 13.1℃ to 14.9 ℃. Thus it can be seen, rainfall and evaporation process makes the changes of moisture content, temperature, and moisture migration rate increased. Soils tended to be broken. After rainfall process and under same evaporation conditions, obvious fissures in soil sample with vegetation covered don’t appear. Moisture content of surface soil changes from 3.16%to 2.36%. The drying rate of surface soil changes from 0.58%/d to 0.37%/d. The average temperature variation of surface soil changes from 0.58 ℃ to 0.37 ℃. Obviously, short-term rainfall and evaporation process has a low influence on the moisture holding capacity of expansive soil with vegetation covered.