Centrifuge Dynamic Model Test Research On Liquefaction Of Saturated Sand Layer Under The Condition Of Different Coating Thickness

Saturated sandy soil liquefaction is a common form of earthquake disasters, and the consequence is serious once it occurs, so the study of sand liquefaction is always an important research subject in the field of geotechnical engineering. For the sand layer whose buried depth is more than 20m, the problem of liquefaction is not considered in current seismic codes. However, due to the phenomena of deep soil liquefaction that occurred in the earthquake of WenChuan in China and Christchurch in New Zealand and the situation that the buried-depth for the foundation of super high-rise buildings and the hydraulic structure layer thickness gradually increase, judging the liquefaction of the deep soil layer and determining the influence mechanism of liquefaction resistance for the conditions of the sand layer depth have become a scientific problem that must be considered and solved.According to the above issues, dynamic centrifuge model tests were conducted, which simulated the vibration process with different coating thickness of saturated sand layer in order to study the influence of different coating thickness on the liquefaction of saturated sandy soil and explore the influence mechanism of the buried-depth on the liquefaction resistance of saturated sand layer. The main research contents are as follows:(1) The dynamic centrifugal model tests were conducted which simulated the vibration process with different coating thickness of the saturated sand layer, such as 0.0m,10.4m,22.9m. The phenomenon of sand liquefaction was reconstructed, and the accelerations and pore pressure at different locations in the model were monitored;(2) Based on the monitoring results of pore water pressure sensors in different position of the models, the development pattern of the super static pore water pressure under different cover layer thickness in the process of liquefaction was studied, and it was clear about the mechanism of the effect of the saturated sand layer liquefaction resistance with the increasing of coating thickness;(3) Based on the results of the acceleration time history at different locations in the model and the calculation results of the pore pressure ratio, the variation characteristics of the acceleration time history curves and the stiffness variation of sand layer in the process of liquefaction were obtained. The rationality of the method was verified based on the measured results of the acceleration time history, and the relationship between the stiffness degradation amplitude and the pore pressure ratio of the soil was simply proposed.