Research On Dynamic Response To Vibratrory Loads Of Silty Soils And The Physical Mechanics In The Yellow River Estuary

Based on resonance column method and dynamic triaxial tests, shear modulus and damping ratio characteristics of saturated silty soil in the delta of Yellow River were studied in detail. The results show that the influence of silt content on dynamic shear modulus is important. Normalized shear modulus and damping ratios vs. shear strain curves are both affected by confining pressure, and the effect of clay content is not apparent. By comparisons of our results with the modulus reduction and damping ratio curves for sand and saturated clay suggested by Seed, It shows that the dynamic characteristics of deformation of the silty soil is more similar to sand, but there is a distinct difference. The trend of the modulus reduction and damping ratio curves from our test is also different with silty soils in other area. Modified Hardin-Dmevich models and logistic models are used to describe the trend of the normalized modulus reduction curves and damping ratios vs. shear strain curves in the paper.Based on dynamic triaxial tests of saturated silty soils in the delta of Yellow River, through analysis of the trend of pore water pressure, dynamic strength of the different silty soils were studied. By taking into account both the trends of development of shear strain and pore water pressure, a new liquefaction standard was used in the paper. The effect of load magnitude and vibration frequency, clay content, consolidation ratio, and micro-structure of soils on the development of shear strain and pore pressure were discussed. The models of pore water pressure and liquefaction resistance were also studied.On the basis of in-situ simulation experiments and close observation, this paper sets out to reveal the physical mechanics underlying the processes by studying the process of absorption of vibration energy by seabed soil and analysing the corresponding dynamic variations in porewater pressure and bulk soil resistivity. Analytical results show that along with the increasing of vibration number, vibration energy absorbed by seabed soil will be redistributed and transferred thereinto, i.e., energy absorbed by surface layer will decrease while energy absorbed by middle and lower layers will increase. Due to the vibration, both the decrement of energy absorption and the bulk resistivity of soil vary like parabolic curves along the depth, and the maximum recruitment and recovery of bulk resistivity appear at the same depth where pore water pressure varies most sharply and local liquefaction probably takes place earliest. Former research show that there is a hard crust at the same depth and it's the major depth of the sea bed strength' loss and recovery under vibratory load happened (Jia Yonggang,et al,2003,2005). In a nutshell, there are homologous relationships between the process of absorption of vibration energy by seabed soil and the variation processes of bulk resistivity, pore water pressure and strength of the soil.By simulating the dynamic response of silt and wave with a compactor vibrating on the seabed, the granularity composition and microstructure characteristics have been studied On the basis of such in-situ pore water pressure measuring, The experiment results revealed that some index of the granularity and microstructure will be change such as small granule will be transferred, microstructure including direction and figure coefficient and ratio of pore will be adjusted too., But the transformation change a lot along depth with some special areas. We discussed the mechanism in combination with the change of pore water pressure and pointed out that the range is mainly concentrated above the maximum value site in the seabed., The silt layer due to this mechanism distinguish from the typical sediment theory. <, At the same time, it is also important to recognize the formation of many geology phenomenon such as duricrust layer that is universe in the seabed <,...