In the reconstruction of old factories and in the small scale engineering, it is often taken place that the present methods for predicting liquefaction of clayey silt could be not used for lack of subsoil exploration data. Two simplified formulas which contain the coefficient of αPc considering the effect of clay content Pc and the coefficient of αIp considering the effect of plasticity index Ip are presented for predicting seismic liquefaction of saturated clayey silt. Thus, the prediction of liquefaction of clayey silt could be effectively proceeded under the conditions lacking of analysing data of soil grain composition
