## 5 High-Embankment Settlement Preloading Test
### Preloading Design  
1. Load design  
Based on the previous numerical simulation results, this plan proposes the use of water from a nearby reservoir for preloading the embankment. Calculations are made based on a maximum fill height of 20 m, and the compacted soil-rock mixed-fill material is assumed to have a maximum density of 2.0 g/cm\({}^{3}\). If the preloading head is controlled at 5-10% of the total mass of the high embankment, then the preloading height using reservoir water would be approximately 2.0 to 4.0 m for a maximum fill height of 20 m. Similarly, if the maximum fill height is 10 m, and the material density is 2.0 g/cm\({}^{3}\), the preloading height using reservoir water can be set at 1.0 to 2.0 m.  
2. Preloading design parameters  
The thickness of the on-site water-stabilized layer is 38 cm, and the width is 11.25 m. For the preloading design, an 11 m width is used, and the density is calculated at 2.0 g/cm\({}^{3}\), equivalent to an actual head of 0.76 m. After comparison, PVC water bags are chosen for the preloading. The dimensions of the water bags are 11 m in length, 5 m in width, and 1.3 m in height. The maximum water filling capacity is 66 tons, requiring a total of 10 water bags. Calculations for the preloading water head, based on an average embankment height of 20 m, set a lower limit of 2.0 m. In addition to the embankment's bearing capacity, a water filling height of 1.2 m is also set, and it can be adjusted in three load levels: 0.8 m, 1.0 m, and 1.2 m.  
The placement of water bags and drilling is shown in Figure 13. The preloading section covers milepost K68+480 to K68+530. After placing two water bags from the starting point, a deep borehole is positioned at K68+490, with its center 1 m away from the hard shoulder. Calculations based on the embankment depth reveal that the filling depth at K68+490 is 36 m, the drilling depth is 46 m, and the installation of settlement rings requires 41 rings. Similarly, after placing two more water bags, a second deep borehole is located at K68+511, with its center 1 m away from the hard shoulder. The filling depth at K68+511 is calculated to be 30 m, the drilling depth is 40 m, and 35 settlement rings are required for installation. The total drilling depth is 86 m, and a total of 76 settlement rings are installed.  
Figure 12: Post-construction maximum settlement variation curve for Section 1.  
is injected to three different load levels: 0.8 m, 1.0 m, and 1.2 m. The injection ports are placed on one side of the central median.
5. Leave a gap of more than 50 cm on both sides of the deep borehole locations for pedestrian access and deep hole monitoring.
6. Lay non-woven fabric and water bags one by one and inflate and fill them with water using the blower.
7. Conduct a water injection test with a height of 0.8 m for the first 10 water bags while simultaneously monitoring deep borehole and slope displacements. Adjust the water head height to 1.0 m or 1.2 m based on the monitoring results as needed.
8. The preloading period is determined comprehensively based on different fill thicknesses and preload loads, combining theoretical calculations with monitoring results, and is expected to be between 30 and 120 days.
9. After preloading is completed, recover the water from the water bags and observe the rebound of the fill.  
The real-time image of the preloading process is shown in Figure 14, and deformation monitoring of the roadbed is conducted during the loading process.