Experimental Study On Vertical Distribution Of The Wave Pressure Within The Liquefied Silty Soil

There have been a lot of research achievements on the dynamic response of theseabed and the seabed instability under wave loadings. silty seabed is prone to beliquefied under the action of waves. When the seabed is liquefied, the liquefied soilcan move like the water and the soil grains can move like the water particles in anorbital of an ellipse. The soil grains with this motion state can act and produce anadditional pressure on the on the buildings, which can lead to a large damage. Seriesof researches are carried through this paper based on these engineering geologicalfacts.Silty soil from the Yellow River Subaqueous Delta is studied through in-labflume experiments by making silty seabed. Through the flume test, pore waterpressures and soil pressures are measured under the condition of different waveheights and depths in liquefied bed and no-liquefied bed. The effective stress, wavepressure, and the relationship between the wavy statement and the wave pressure ofthe liquefied silty soil are studied in this paper. The results are as follows.When the silty seabed is liquefied, the effective stress still exists with a smallervalue in the bed. In this study, the effective stress in the liquefied silty soil is about11%~18%of the overburden stress, which is smaller than that in the no-liquefied bed.The effective stress shows a significantly difference in depth, and the differencedecreases with the increase of wave height. There will be a great value of the effectivestress after a certain period of time at the same depth under the same wave then theeffective stress will decrease.The soil pressure increased with depth generally in a linear manner underliquefied phase. The soil pressure change little in liquefied soil compared with that inthe non-liquefied soil and decays faster with the depth. The liquefied soil can make anincrease of the pressure of the upper water and a decrease of the pressure of the lower non-liquefied soil. However, the soil dynamic pressures increased significantly, oftenseveral to more than10times, especially in the shallower liquefied soil layers, inliquefied soil compared with the non-liquefied soil observed in the same depth. Thedynamic pressure decays faster in the depth under the higher wave height.According to the results of the experiments and further analysis, an empiricalequation between the soil dynamic pressure of the liquefied soil and wave parametersis put forward under the condition of the flume test through regression analysis. Then,the rationality of the empirical equation is demonstrated in the flume test and field.Necessary attention should be pay to the phenomenon of the significant increase ofthe dynamic pressure within the liquefied soil in the design of the coastal engineeringbased on the in-lab research achievement.The wavy statement of the liquefied soil is measured in this study. The amplitudeand the speed of the liquefied soil grains are both decay in exponential form with thedepth in the vertical. The dynamic pressure is correlated with the speed of the soilgrains, and poorly correlated with the square of the speed of the soil grains. Thedynamic pressure is also related to other parametric in addition to the speed of the soilgrains.The results in this paper may be different with the physical truth, because of thelimit of the measurement method and the scale of the flume. The fact of the wavepressure of the liquefied silty soil should be further studied and perfected.