6. CONCLUSION
In order to ensure the functionality of typical LID facilities and the safety of the surrounding buildings and roads in collapsible loess areas, a full-scale field test on water infiltration in typical stagnant bioretention facilities was carried out. The water content and moistening deformation law of the site during the process of rainwater infiltration were comprehensively analyzed. The conclusions of this work can be summarized as follows.
(1) As rainwater infiltrates the stagnant bioretentions in the loess area, the infiltration effect first increases and then tends toward stability. The influence range of rainwater varies with the type of facility. The retaining wall type affects the site more intensely at the initial stage of infiltration, while the sloping type has a more significant impact on the site at the later stage of infiltration.
(2) Water infiltration mainly affects the bottom of the facilities but has little effect on the subgrade. The subgrade deformation specification was met at the test site. The deformation under the subgrade of the retaining wall type facility was 0.5 mm and exerted a greater impact on the subgrade deformation than the sloping type facility. When the bioretentions are constructed near a municipal road, sloping infiltration facilities should be given priority.
(3) The modified Green-Ampt model accurately reflects infiltration rainwater law in the collapsible loess field under bioretentions. The model’s average infiltration depth error is about 10%.
(4) The adverse effect of water infiltration in the retention type bioretention can be mitigated by adjusting the initial water content and saturated water content in the loess area.