Experimental Study on Capillary Water-Holding Characteristics of Loess Backfill in Ecological Ditches
The municipal ecological ditches have the basic functions of accumulating water for infiltration in the rainy season and conserving moisture in the dry season.However,the design of loess backfill in ecological ditches is based on no evidence,which often leads to landscape vegetation drowning in the rainy season or dying in the dry season.For this reason,a study was carried out by remoulding loess with a small-size capillary water rise height test,a large-size water-holding characteristic model test,and an unsaturated numerical analysis.The results show that the final capillary water rise height of the soil column can reach 100 cm when the dry density is 1.3 g/cm3 and 1.4 g/cm3,respectively,and the water content of the soil column is basically stable after the height of the soil column exceeds 20 cm,with the stable water content of 30.0%and 28.0%,respectively.In the process of capillary water rise of remoulded loess,a transient saturation zone exists,in which smaller dry density indicates larger pore ratio,increased large pores,and weakened capillary suction,resulting in a slower rate of water migration.At the same time,the number of large bubbles closed by the wet bridge is also larger,so the duration of the transient saturation zone is longer.For a soil column of 1.3 g/cm3,the simulated value of the wetting front time curve is basically consistent with the measured value.By considering the stable natural average dry density of loess stratum,the height of capillary water rise,and its water-holding characteristics,as well as the fact that the backfill in ecological ditches will undergo repeated infiltration,consolidation,and capillary action in the later stage,1.2 g/cm3 is adopted as the dry density for backfill control,so as to ensure that the planting soil in the municipal ecological ditches can still maintain the soil humidity necessary for the growth of the vegetation in the dry season.
ecological ditchesloess backfillcapillary water risemodel testnumerical simulation
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