增湿-减湿作用下黄土裂隙演化规律研究

EVOLUTION OF LOESS CRACK UNDER ACTION OF DEHUMIDIFICATION-HUMIDIFICATION

黄土内部存在各种裂隙,增湿-减湿作用导致原状黄土内部裂隙不断发展演化,因此研究在增湿-减湿作用下黄土裂隙发育演化规律具有非常重要的意义。以陕北延安地区某边坡黄土为研究对象,通过CT扫描技术获得了增湿-减湿作用下土样细观结构变化图,得到了土样CT数ME及SD值随土样增湿-减湿作用的变化曲线。研究结果表明:随着土体湿度的增加,土体内部损伤速率缓慢增加,当含水率超过土样塑限后,土体内部损伤速率加快,含水率超过一定值时,速度又减缓,CT数的均值和方差随含水率变化皆呈反"S"曲线;随着干湿循环次数的增加,土样微裂纹逐渐发育,表现为伸长变宽,呈不规则的分叉、甚至贯通;4次干湿循环后,土样裂隙裂缝基本成了网状,土样较破碎,此时CT数的均值和方差变化不大;干湿循环幅度越大,土样内部损伤程度也越大,土样内部节理裂隙发展也就越快。

It is very important to study the evolution law of fracture development in loess under humidification- dehumidification ,because there are various cracks in the loess. Humidification -dehumidification lead to the development of internal cracks in undisturbed loess. The loess in Ya^an area is used as the research object. The soil microstructure change map of humidification -dehumidification and the soil sample CT number ME and SD values of soil samples with humidifier-dehumidification effect curve are obtained by CT scanning technology. The results show that ： as soil moisture increases, the internal damage rate of soil is increased slowly, when the water content over the plastic limit of the soil sample. Soil internal damage rate increases slowly, when the moisture content exceeds a certain limit. The rate will fall. CT numbers mean and variance with moisture content changes are highly anti-“ s ” curve. With the dry-wet recycle number increases, the microcracks in soil samples, develop gradually and show elongation widened irregular bifurcation. After 4 dry-wet recycles, the ground fissures have been basically formed. The soil sample fracture and the CT number have little change. The more wet-dry recycle, the more damage degree of internal soil samples and development of internal joints and fissures in soil sample.