# Nonlinear Wave-Induced Uplift Force onto Pipelines Buried in Sloping Seabeds
## 4 Results and Discussions
### The Influences of Wave Parameters on the Uplift Force onto Pipelines Buried in the Sloping Seabeds  
For the purpose of investigating the influences of wave parameters on the uplift force applied by waves to pipelines, some numerical models with different wave parameters were operated. In this section, the value of wave height is taken at 2 m intervals in the range of 2 m to 8 m. The value of wave period is taken at 1 s interval in the range of 9 s to 12 s. The value of water depth is taken at 3 m intervals in the range of 27 m to 36 m.  
Figure 10 illustrates some simulated results of pore pressure distribution next to the pipeline using variable wave parameters. As noted from the distribution in Figure 10a, the pore pressure next to the pipeline increases significantly as the wave height grows; however, at the same time, the increase rate above the pipeline is higher than that below the pipeline. The greater the wave height, the stronger the pore water pressure under the wave trough. As the soil depth increases, the effect of waves on pore pressure decreases  
Figure 8: Comparison of the pore pressure amplitude along seabed depth between cases with and without a pipeline (through the pipeline center): (**a**) under the wave trough, (**b**) under the wave crest.  
Figure 9: Distribution of pore pressure around the pipeline: (**a**) under the wave trough, (**b**) under the wave crest.  
due to the energy absorption effect of the soil, which leads to different variation in pore pressure around the pipeline.  
The reason for the different change rate of pore pressure above and below the pipeline can be attributed to the \"shielding effect\" of the pipeline on the pore water discharge. As Figure 10b shows, with wave period increasing, the pore pressure next to the pipeline gradually increases, but after a certain level, the effect of wave period is negligible. The growth in wave period increases wave length, which increases the range of pressure on the seabed surface. However, the soil response far from the pipeline cannot affect the pipeline, so the effect of increasing the range of pressure on the pore pressure around the pipeline is limited when the rest of the conditions remain unchanged.  
Based on Figure 10c, as the water depth grows, the pore pressure next to the pipeline gradually reduces, while the decrease rate gradually decreases, and the decrease rate above the pipeline is always greater than that below. The phenomenon can be attributed to the fact that the greater the water depth, the less the wave effect the seabed, and this effect also diminishes with the soil depth.  
The variation on the pore pressure around pipelines may result in a change in the uplift force applied to pipelines. Figure 11 illustrates some variations of the uplift force applied to the pipeline with the wave parameters. As noted from the curves in Figure 11, the higher wave height significantly enhances the uplift force applied to the pipeline. Meanwhile, the longer wave period is also able to increase the uplift force applied by wave to the pipeline in a certain range, once beyond this range, this influence becomes very small. In addition, the uplift force decreases as the water depth grows. The variation of the uplift force applied  
Figure 10: Distribution of pore pressure response around the pipeline for variable wave parameters under the wave trough: (a) H, (b) T, (c) d.  
by wave to the pipeline in Figure 11 is explained by the varying distributions of the pore pressure next to the pipeline in Figure 10.