The grains of noncohesive soils are classified into three groups: skeleton

movable and clogging based on their movability under seepage. If there are some movable grains in a noncohesive soil

piping is easy to take place. In consideration of the grain-size distribution and the degree of densification of soils

a new method for assessing the piping-typed soil is suggested; and its application to some piping tests illustrates its validity. The calculated results show that the degree of densification has influence on the minimum pore diameter

the fractile diameter

the content of movable grains and that of clogging ones.