Dynamic pore pressure model for saturated loess based on dissipative energy

A series of undrained dynamic triaxial tests is carried out to investigate the evolution patterns of pore water and accumulative dissipated energy during the vibration-induced liquefaction of saturated loess, and the effects of confining pressure, dynamic stress amplitude and consolidation stress ratio on them are discussed. The results show that the pore water pressure and dissipated energy of saturated loess gradually build-up with the increase of cyclic loading times during vibration-induced liquefaction. The consolidation confining pressure inhibits the increase of pore water pressure and consumes more energy. Larger dynamic stress amplitude leads to faster increase in pore water pressure and less energy consumption. Under the isotropic consolidation, the increase of pore water pressure causes the effective stress to be 0, thus triggering the initial liquefaction. However, under anisotropic consolidation, the specimen usually reaches the strain criterion for liquefaction first, while the pore water pressure does not increase to the confining pressure level, and the larger consolidation stress ratio leads to the lower pore water pressure and less cumulative dissipated energy during liquefaction. The pore water pressure is closely related to the cumulative dissipated energy, and normalized pore water pressure u/sigma(0)' and the cumulative dissipated energy W/W-f are less influenced by the confining pressure, dynamic stress amplitude and consolidation stress ratio and can be expressed uniformly in a hyperbolic model.