# Study on Seepage Effect of Roadway Based on Polyformaldehyde(POM) Fiber Concrete
## 4 Numerical Simulation Analysis Based on FLAC3D
### Analysis of Seepage Influence of Roadway Under Ordinary Support Conditions  
Figure 11 shows a pore-water pressure diagram of the roadway. With the completion of the excavation and support work of the roadway, the groundwater began to penetrate into the roadway due to the water pressure difference around the roadway and gradually formed a seepage field centered around the roadway. In this funnel-shaped seepage field, groundwater flows along the movement track of cracks and rock layers to the center, forming an obvious seepage area around the roadway, with the pore water pressure reaching 1.7 MPa.  
As can be seen in Figures 12 and 13, due to the influence of groundwater seepage, the stress in the rock mass formed a stress concentration at the roof position of the roadway, resulting in the deformation of the roof. The maximum principal stress was 0.49 MPa, and the displacement was 43 mm. Under the action of stress, the stability of the roadway's surrounding rock decreased significantly. The existence of pore pressure has an adverse effect on the stability of a roadway, and it changes the stress distribution around the roadway, resulting in a more serious stress concentration around the roadway, which affects the stability of the roadway [54; 55]. This stress concentration may aggravate the deformation and failure of the surrounding rock, thus affecting the overall stability of the roadway. The roadway needs to be reinforced. The roadway should be strengthened to prevent and drain the water in time.  
Figure 10: Numerical model of roadway.  
Figure 11: Pore water pressure of the surrounding rock of the roadway, with pressure values in Pascal (Pa) as indicated by the color scale on the left.  
Figure 12: Minimum principal stress of the roadway’s surrounding rock, with stress values in Pascal (Pa) as indicated by the color scale on the left.  
Analysis of Seepage Effect of the Roadway Under the Condition of a Polyformaldehyde Fiber Concrete Support  
From Figures 14-16, it can be clearly seen that for the polyformaldehyde fiber concrete support, the pore water pressure in the road was enhanced to 2.52 MPa, compared to the normal support. This shows a significant increase in the road's capacity to resist the seepage of water. The deformation of the roof was minimized under this support, which was a displacement of 12.5 mm, a reduction of 30.5 mm compared to the normal support.  
Furthermore, the maximum principal stress formed a stress concentration on the roadbed's rooftop, which was a maximum of 0.91 MPa, 0.42 MPa higher compared to the normal support. These results illustrate that polyformaldehyde fiber concrete support can increase a roadbed's permeability resistance and a roadbed's stability, which can lower underground roadbed safety risks due to the seepage of groundwater. This can play a critical part in maintaining a tunnel's stability and safety in groundwater-affected areas for a lengthy period.  
Figure 13: Displacement of the roadway’s surrounding rock under ordinary support conditions, with displacement values in meters (m) as indicated by the color scale on the left.  
Figure 14: Pore water pressure under polyformaldehyde fiber concrete supporting conditions, with pressure values in Pascal (Pa) or MegaPascal (MPa) as indicated by the color scale on the left.  
Figure 15: Minimum principal stress under polyformaldehyde fiber concrete supporting conditions, with stress values in Pascal (Pa) as indicated by the color scale on the left.