In Situ Observation of Silt Seabed Pore Pressure Response to Waves in the Subaqueous Yellow River Delta

The in situ pore pressure response of silt under wave action is a complex process. However, this process has not been well studied because of limited field observation techniques. The dynamic response process is closely related to engineering geological hazards; thus, this process must be urgently explored. A long-term in situ observational study of the silt sediment pore water pressure response process under wave action was conducted in the subaqueous Yellow River Delta. The response characteristics of pore water pressure are affected by tidal level and wave height. Tidal level affects the overall trend of the pore water pressure response, while wave height influences the amplitude of the pore water pressure response. This study revealed a significant lag effect in the pore pressure response. The transient pore pressure in the seabed did not respond immediately to the wave-induced pressure stress on the seabed surface. This phenomenon may be attributed to the change in soil permeability. The maximum response depth was approximately 0.5 m with a 2 m wave height. A concept model of silt soil pore pressure response under different types of wave action was developed. The accumulation rate of the pore pressure is less than the dissipation rate; thus, the developed model highlights the oscillation pore pressure response mechanism. The highlighted response process is of considerable importance to transient liquefaction and the startup process of pore pressure response.