Analysis of Pore Pressure Difference Between Fine- and Coarse-grained Soils During Dynamic Fluidization

Liquefaction of foundation soils under the action of dynamicforces can have disastrous effects on the engineering. Pore water pressure is an important parameter for saturated soil transforming into fluid. The exsiting studies have found that during the process of liquefaction, fine-grained soil can enter the liquefaction state even if the pore pressure ratio (pore pressure/ enclosure pressure) does not reach to 1. A theoretical model for generating dynamical fluidization in the cases where a flow can occur is established for saturated soils composed of sand, silt and clay particles. In the model, the soil particles are assumed to be spheroids and the influences of particles adsorbing water film are taken into account. In addition, the changes of pore pressure in dynamic triaxial and shaking table experiments are also analyzed. Based on the characteristics of soil microstructures, it is proposed that when fine-grained soil is in a fluidized state, the pressure of pore water can cause the pore pressure to decrease due to the influence of bound water film. Mesnwhile, the pore pressure can also be reduced due to the framework support of particle shapes (e.g. the plate shape). This theoretical analysis conducted according to the physical properties of the soil microscopic compositions can help to clarify the reasons for the difference in dynamic fluidization criteria between the fine-grained soil and the coarse-grained soil based on pore water pressure and to understand further the intrinsic mechanism of the soil liquefaction.