Experimental Study On Dynamic Characteristics Of Various Clay Content Silty Soil Of The Yellow River Delta

In the Yellow River delta, the silty seabed is prone to geological hazards including landslides, collapses, silt flow, etc. As the production areas of oil and gas resources, more and more marine structures are built in these areas, such as submarine cable and oil pipelines. However, the silty seabed is usually caused failure because of bad marine dynamic actions, so researches on silty soil of dynamic characteristics under cyclic loadings are very important.In this study, through prepare various clay content silty soils as the research objects, several methods are carried out to study the dynamic properties, such as laboratory dynamic triaxial experiments, theoretical analysis and calculation method and summarized previous researchers'results.Through dynamic triaxial experiments to simulate wave actions, the dynamic characteristics of various clay content silty soils are study. Based on the experimental results, the dynamic strength weakening rule of various clay content silty soils is analyzed; the development characteristics of dynamic pore water pressure are study, also the effect of clay content to the dynamic pore water pressure is studied; the critical cyclic stress ratio of Yellow River Delta silty soil is given out.The research results on the dynamic characteristics of various clay content silty characteristics show that the dynamic shear strength, cohesive force, and internal friction angle attenuate in a curve of power function with the increasing cycle numbers. Clay content has a significant influence on the dynamic strength of silty soils and the dynamic strengths of various clay content silty soils show great difference under different confining pressure. Clay content also has a significant influence on the development of dynamic pore water pressure and the influence mainly presented as both the development rate and the maximum value of pore water pressure decrease with the increase of the clay content. However, the pore water pressure development of various clay content silty soils can be expressed by a unified pore pressure development mode and the difference is that the coefficients in the pore pressure development mode are different with each other. Based on the experimental results and previous researchers'results, using the critical cyclic stress ratio formula Kcr=((sd+sl)/s3)cr for conversion calculations, the critical cyclic stress ratio of remolded silty soils of Yellow River Delta is determined as 1.30 and that of the undisturbed silty soils is determined as 1.40.Through wave flume experiments, the formation reasons of the formation of the hard layer of subaqueous Yellow River Delta are discussed. The results show that the wave action may lead to the oscillation sliding of superficial local weak seabed; the fine particles of the soil gradually moves up and into the water in the process of wave action, and then the clay particles content of the soil decreases and the soil particle size coarsens; meantime the water in the sliding soil discharges out in the process of soil oscillating, causing the decrease of water content and the increase of soil density, then the soil strength gradually increases and high-value strength layer forms; when the wave action was over and after a period of resting, the soil strength significantly increases because of the continuance of water discharging.