In order to study the effect of silt particle content

a series of dynamic cyclic tests of saturated and disturbed silt were conducted in a new universal triaxial torsional shear apparatus of Hohai University.The tests didn′t stop until the pore water pressure developed to a smooth way.It can simulate the whole process for pore pressure development from initial liquefaction to the serious liquefaction degree.Based on the tests results

a special regulation called expression（1） was proposed.The expression（1） consists of two parameters

a and b.One of the two parameters b in expression（1） reflects the silt particle effect on pore water pressure development.Coefficient b increases with silt particle content while another coefficient a keeps constant.The results indicate that the theoretical value by the expression agrees well with the test data.