Dynamic characteristics of isotropically consolidated intact soft clay and study of pore water pressure based on energy method under wave loading

A series of tests with principal stress rotation were carried out on 5 Hz ZJU-HCA to investigate the dynamic characteristics of isotropically consolidated Hangzhou intact soft clay under wave loading. The dynamic characteristics such as the development of strain and degradation of modulus were studied under different frequencies or cyclic stress ratios. Furthermore, the relationship between pore water pressure and the dissipated energy as well as the collapse energy were analyzed based on energy method. The result show that under principal stress rotation, there exists a threshold cyclic stress ratio in the intact soft clay. When the cyclic stress ratio is smaller than the threshold value, the strains only develop in a small range and the modulus of the soft clay attenuates in a sharp-steady mode; when it is larger than the threshed value, there is an abrupt point in the strain verse cyclic number line due to the structural collapse of soil. Meanwhile the modulus decreases in a sharp-steady-sharp way, and the lower the frequency or the larger the cyclic stress ratio is, the faster the strains develop and the modulus degenerates, the fewer cyclic numbers required to achieve the structural collapse. Frequency and cyclic stress ratio have some influence on the relationship between pore water pressure and dissipated energy as well as the collapse energy, that is, the lower the frequency or the larger the cyclic stress ratio, the faster the pore water pressure develops with dissipated energy, and the less the collapse energy. The frequency and cyclic stress ratio affect the relationship between pore water pressure and dissipation energy as well as the collapse energy through changing the percentage of the two parts energy. ©, 2015, Central South University of Technology. All right reserved.