Abstract: To explore the influence of seepage deformation on the permeability and compressibility of coarse grain soil, the whole process of seepage failure and compression experiment with lateral confinement on coarse grain soils with different gradations were conducted using seepage failure instrument developed by the authors. The critical hydraulic gradient, evolution law of permeability coefficient and damaged characteristics were obtained through analyzing the measured data and observed phenomenon during the test process. The results indicate that the seepage extrusion effect will generate firstly at the location of downstream along seepage path during seepage failure process and induce decrease of the permeability at the location. The permeability of the seepage extrusion part increases gradually with the increment of the experiment water head. The compression modulus of samples decreases after the seepage failure occurred. The degree of damage of the sample due to seepage failure is different on different grading samples. For soil samples after seepage failure, the structure of soil samples is reconstructed under the influence of gravity and seepage force.

Key words: coarse grain soil, seepage failure, damage due to seepage, structure reconstruction