Abstract
Previous studies have shown that the rise of the groundwater table has
induced a large number of landslides on the Heifangtai terrace, but it
is not clear how the irrigation water flows into the loess and whether
it affects the groundwater directly when infiltrating the ground below.
In order to understand and analyze the unsaturated seepage in the loess
vadose zone, water infiltration was investigated in this paper using a 6
m high remold loess column and artificial tracers. According to the
analysis of the different infiltration stages, the existence of
unsaturated seepage was indirectly proven. In addition, by comparing the
tracer effects of the chloride and bromide ions, it was concluded that
though the apparent moisture content was unchanged in the deep vadose
zone, the regular downward enrichment of chloride ions demonstrated the
existence of unsaturated seepage. We recommend that chloride ions be
used as the soil tracer, and bromide ions be used as the water tracer
during the in-situ monitoring of unsaturated seepage in Heifangtai. A
numerical simulation was also constructed using COMSOL
Multiphysics
to analyze the solute transport. The results show that
unsaturated
seepage is not affected by the second irrigation, and the effect of the
rising groundwater table is small and is limited to the transition zone
between the saturated and unsaturated zones. Therefore, this study
provides new insight into landslide mechanisms in Heifangtai based on
the analysis of unsaturated seepage.
Key words: Heifangtai, loess, unsaturated seepage, column test, solute
transport, COMSOL Multiphysics