4.2 Moistening Deformation Law
The water content values of different facilities at different times in the immersion process were substituted into Eqs. (3) and (4). The moistening deformation of each position was calculated at different time points and a contour map of humidifying deformation of the loess site was obtained accordingly, as shown in Fig. 11.
[Insert Figure 11]
As shown in Fig. 11(a), in the initial stage of water infiltration, the maximum deformation was 3.5 mm away from the bottom of the facility at 0.35 m. By 6 h, the maximum deformation of the bottom of the facility increased to about 10.5 mm due to the rapid increase in water content, which was three times larger than that at 2 h. By 24 h, the water content and deformation of the bottom of the facility had both stabilized. There was deformation under the subgrade at that time but only by about 0.5 mm, which is far less than the specification for subgrade deformation. The water infiltration in Bioretention I, to this effect, did not impact the road safety around the facilities.
As shown in Fig. 11 (b), after 2 h of infiltration, the settlement at the bottom of the facility was about 1.5 mm. After 6 h, the deformation at the bottom of the facility reached 10.5 mm, which is seven times larger than that at 2 h. Once the water content was stable, the maximum deformation at the bottom of the facility reached 15 mm, which is 1.4 times larger than that at 6 h. The settlement of the site increased slowly with the gradual stabilization of the water content. After 24 h, the settlement of the subgrade was less than 1.5 mm, which is below the relevant specification. Again, it appears that water infiltration had little influence on the subgrade.
Water infiltration through biorentention facilities appears to have influence on the subgrade. The influence range of Bioretention II on the subgrade was smaller than that of Bioretention I in this experiment. This phenomenon is possibly attributable to the structural form of the facilities and the disturbance degree to the site during their construction processes.