SOIL LIQUEFACTION POTENTIAL EVALUATION WITH USE OF THE SPECTRUM AT DEPTH

A method to evaluate soil liquefaction susceptibility is presented. In this method the response spectrum of the ground was introduced to take into account the significant influence of soft surface layers on the maximum acceleration at the ground surface. Resonant period of a site is estimated from the configuration of horizontal surface layers, which is expressed by shear wave velocities evaluated from the N-value distribution of the standard pentration test. The maximum acceleration at the surface was calculated by multiplying the maximum input acceleration at the bed rock by dynamic amplification factor proposed by Kanai. A conventional mehtod of liquefaction analysis was adopted to determine the liquefaction susceptibility of sand layers of different N value distribution. Critical N values of SPT and the maximum epicentral distance of liquefaction were derived from the theoretical considerations.