PURPOSE: To constutute rationally and easily the model of an earth characteristics and to investigate characteristics of multilayer ground liquefaction indoors with high precision by combining an indoor liquefaction testing method, an on- line experimental method, and an effective stress analyzing method organically.

CONSTITUTION: A motion equation of a shear wave to a ground input is solved to obtain the propagation state of shearing stress, etc., in the ground, which is applied to a body whose ground elements for on-line experiment are to be tested to reproduce the earthquake action of ground elements of the multilayer ground in an indoor test. Its test result shows variation in soil property during an earthquake and is fed back to the motion equation to obtain response values of plural test layers of the multilayer ground. Further, variation in gap hydraulic pressure in the multilayer ground with time is evaluated from a water permeation equation as to the perpendicular dissipation of the gap hydraulic pressure and when the gap hydraulic pressure becomes equal to initial effective vertical stress in said process, the occurrence of liquefaction is reproduced and the liquefaction is investigated.