Failure criteria for soft clay subjected to frequencies under train loads

The heart-shaped stress path can be caused by train loads in the foundation. The train load path has a more complicated influence on foundation soils when the effects of frequencies are considered. A serious of undrained cyclic hollow torsional shear tests are carried out on typical remold soft clay (in Hexi District of Nanjing) with different values of vibration frequency f and dynamic stress ratio η. It is found that the trend of soil deformation influenced by frequencies can be divided into two types. Otherwise, the critical dynamic stress ratio first decreases and then increases with the increase of the frequency. When the frequency f locates in the range of 1.0~2.0 Hz, the developing curves of pore pressure are consistent and the influences of the frequencies are small. However, when the frequency equals to 0.5 Hz, the development of pore pressure significantly increases. Then a new failure evaluating method for remolded soft clay is presented. It is used to investigate the influences of the frequencies caused by train loads. This criterion can distinguish the stable, critical or destructive states of samples mainly by the pore pressure-strain coupling curve. The range of failure strain and vibration cycles can also be given. The results may provide theoretical support for the researches on the bearing capacity of soft clay foundations subjected to traffic loads.