## 4 Numerical Model of Bedding Slope
### Analysis of seepage Results  
#### 4.3.1 Highway Slope Seepage Analysis  
In order to obtain the initial conditions of flow, geotechnical saturation and pore water pressure inside the slope at the beginning of the calculation, the highway slope is pre-analyzed and processed for 30 days under no-rainfall conditions. The initial state of the slope is shown in Figures 8a and 9a, where there is essentially no flow within the slope, and the phreatic line (the boundary between saturated and unsaturated zones) remains near the initial water level (29.5 m). The distribution of pore water pressure in the slope is relatively  
Figure 6: Water pressure distribution in the slope.  
Figure 7: Slope seepage-deformation calculation process.  
uniform, the pore water pressure in the area above 35 m height is greater than \(-47.88\) kPa, and the pore water pressure in the area below 35 m height increases with the depth in an approximately equal gradient, and the maximum pore water pressure is 311.22 kPa.  
Figure 8: Unit flow and phreatic line in the highway slope: (**a**) Initial state; (**b**) 13 July; (**c**) 15 July; (**d**) 27 July.  
The transient seepage analysis is carried out using a finite element program that divides the calculation into 27 time steps for 27 days for the seepage field at one time  
Figure 9: Pore water pressure contours for the highway slope: (**a**) Initial state; (**b**) 2 July; (**c**) 15 July; (**d**) 27 July.  
step per day. Firstly, as shown in Figure 9b, the change of pore water pressure within the slope is limited on 2 July. The pore water pressure at the slope surface is in the range of \(-47.88\) to \(-23.94\) kPa, and the pore water pressure in the vicinity of the roadbed excavation increases to 0 kPa at the highest. This is because at the beginning of the rainfall period, the initial saturation of the slope is low, and the hydraulic conductivity of the top sub-clay and fill soils is greater than the intensity of the rainfall. Rainwater is mainly recharged by vertical infiltration, which is large and produces little flow. Then, as shown in Figure 8b, rainwater on 13 July pools in the area of the roadbed excavation and infiltrates the exposed beds of weakly weathered silly mudstone. Also, because the soft interlayer in the weakly weathered zone acts as a water barrier, rainwater enters from the rapid infiltration channel in the roadbed area and then travels down the layers. As shown in Figures 8c and 9c, rainfall continued to concentrate on infiltration on 15 July, with the phreatic line extending downward along the layers. Some of the geotechnical bodies are fully saturated, and the pore water pressure rises rapidly, with the maximum pore water pressure reaching 23.94 kPa at the roadbed.  
Finally, the unit flow vectors and pore water pressures in the geotechnical body on 27 July are shown in Figures 8d and 9d, and the phreatic line extends downward along the layers to the deeper part of the slope and connects to the water table line at 30 m. At this time, the infiltrated rainwater is controlled by gravity to flow from the high side of the roadbed to the low side of the foot of the slope, forming a laminar flow movement in the pores and fissures of the rock layer, and lifting the overall groundwater level line of the slope. Phreatic water is exposed at the foot of the slope in the form of a confluence with the Danqing River, and the pore water pressure in a small area near the Danqing River is essentially stable. The geotechnical body in the roadbed-foot of the slope connection area is close to saturation, the pore water pressure rises rapidly, and local high pressure is formed inside the foot of the slope, with the maximum pore water pressure of 383.0 kPa. In summary, under highway slope conditions, the effect of heavy rainfall on the moisture distribution within the slope is significant.