Abstract: To simulate the sea bed strength’s loss and recovery due to the wave load, we chose typical study areas on the tidal flat of the Yellow River Mouth, and carried out in-situ impactive vibration test. We got the silt’s penetration value before and just after the vibration, also the silt’s penetration value after several periods of time. Using these penetration values,we have done some research on the procedure and influential factors of silt strength’s loss and recovery. From the reseach, we found that the strength loss caused by vibration occurs at certain depth under the sea bed, and the variation of silt strength’s loss and recovery appears like a parabola along the depth. After the vibration, water and fine object appear at the surface layer of the silt, and a series of minimal mud volcanoes come into being around the vibration site. The silt’s maximum strength recovery appears at the same depth as the maximum loss. After three-hour recovery, the silt strength surpassed the silt strength before the vibration. The following factors remarkably affect the silt strength’s loss and recovery, the hydrodynamic action that the silt had experienced, the silt’s original strength, circular times of vibration load, the vibration energy, the silt depth and the time of recovery, etc. The mechanism of silt’s strength variation due to vibration and recovery is very special and further study of the mechanism is required.

Key words: silt in Yellow River mouth, strength loss and recovery, in-situ vibration test