Fundamentals of Liquefaction under Cyclic Loading

The mechanism of progressive pore pressure increase during undrained cyclic simple shear tests on saturated sands has been examined in detail. The concepts developed provide a better understanding of the physical processes leading to liquefaction of horizontal sand deposits during earthquakes. A quantitative relationship between volume changes occurring during drained cyclic tests and the progressive increase of pore water pressure during undrained cyclic tests has been developed. The use of this relationship enables the build-up of pore water pressure during cyclic loading to be computed theoretically using basic effective stress parameters of the sand. The application of the theory to the case of undrained cyclic simple shear tests with uniform stress controlled loading is illustrated. Values of progressive pore water pressure increases predicted theoretically agree reasonably well with the nature of pore water pressure increases observed experimentally.