Abstract: The numerical simulation test is performed for validation vibration isolation function of liquefaction. A gravel drainage layer is applied around underground structure; the anti-liquefaction numerical simulation tests of gravel drainage layer were performed using FLAC3D. Anti-liquefaction effect of the different gravel drainage layer programmes is analyzed; and dynamic characteristic change of underground structures after imposition a gravel drainage layer in liquefaction field is also analyzed. Calculations indicate that when the sandy soil is in the liquefied condition in the model liquefaction field, its acceleration, the speed, the displacement oscillation amplitude weaken immediately. The sandy soil becomes the fluid in the liquefied condition. The liquefaction process is the process which the sandy soil volume pressure strain accumulates unceasingly. The volume pressure strain accumulation no longer increases after the sandy soil is liquefied. The effective stress of liquefied soil is zero. The shearing strength is zero. The liquefied soil cannot transmit the shearing force and isolates outside force. The acceleration of structure in liquefied field is also smaller than the non-liquefied field or the elastic field. The structure, which is in the liquefied field, reduced the hydrodynamic pressure around structure. The structure interrupted the liquefaction around structure. The gravel drainage layer around underground structure will not be liquefied. The ultra hydrostatic pressure in distant place liquefied field reduces obviously. The structure is not floating, the structure subsided. The horizontal drift reduced. The internal force increased. Research results will provide a theoretical and experimental basis for the design of underground structures through the liquefied soil layer.

Key words: excess static pore-water pressure ratio, volumetric strain increment, effective stress, Biot equation, gravel drainage layer