采用TDR水分计研究非饱和黄土入渗及自重湿陷变形规律

STUDY OF INFILTRATION AND COLLAPSIBLE DEFORMATION LAW OF UNSATURATED LOESS UNDER OVER BURDEN PRESSURE BY USING TDR SOIL WATER PROBE

通过在大厚度自重湿陷性黄土场地上进行大规模原位浸水试验,在浸水坑的不同位置和深度埋设TDR水分计,对水在竖向和水平向的入渗运移规律进行实测,研究黄土在地面浸水后的入渗规律与自重湿陷变形规律及其相互关系。研究表明:(1)水在土体中的入渗规律是水沿大孔隙先向下入渗,然后再渗透扩大饱和区的运移过程;(2)在水分的入渗过程中,深度22.5～25.0 m以上土体发生自重湿陷变形,以下土体含水量增加缓慢,达不到湿陷起始含水量,没有发生自重湿陷变形,因此,可考虑22.5～25.0 m作为现场湿陷性评价的临界深度,另外该深度可作为大厚度湿陷性黄土地区进行地基处理时的参考地基处理下限深度;(3)由TDR水分计得出的体积含水率变化曲线不仅可以用来测量体积含水率的时空变化,而且可以用来判定黄土是否发生湿陷变形以及湿陷敏感性和湿陷系数随深度的变化规律,也可粗略计算水在非饱和黄土中的扩散速度。

By large-scale in-situ water immersion test in the field of the collapsible loess under over burden pressure, There are TDR moisture probes embedded in different positions and depths, in order to measure the data about infiltration in vertical and horizontal directions. The law of infiltration and collapsible deformation under over burden pressure and their relationships after soaking are researched, the results show that： （1） The law about water infiltration in the soil is the first big pore, then penetrating down to enlarge saturated~ （2） In water infiltration process, soil which is above depths of 22.5 - 25.0 m is more vulnerable to collapse, and soil below depths of 22.5 - 25.0 m whose soil moisture content increases slowly and reaches hardly collapsible starting moisture contents is not easy to collapse, therefore, the depths not only can be used as critical depth on-site collapsibility evaluation, but also can be considered to be the reference foundation treatment floor depth in large thickness collapsible loess area when the foundation is treated; （3） moisture content change curves which is from TDR soil moisture probe not only can be used to measure volume moisture content changes of time, and can be used to determine whether happen collapsible loess deformation, collapsible sensitivity and variation of collapsible coefficient with depth,and the diffusion speed of the water in the unsaturated loess can also be calculated roughly.