| 抄録（英）： |
In the current routine practice the spring-supported beam model is widely used for designing foundation piles. If the soil is identified to develop liquefaction, the spring constant or coefficient of subgrade reaction is reduced by a factor of 1/6 - 2/3 according to the design code of bridge foundations in Japan. This is applied only to the case of vibratory movements of the ground during the main shaking of an earthquake. If the ground is inclined and starts to deform largely in a horizontal direction immediately after the main shaking, the piles embedded in such ground will undergo a lateral force which would be significantly different from that induced during the main shaking. In an effort to clarify this point several series of back-analyses have been made and the order of magnitude by which the coefficient of subgrade reaction is to be reduced was estimated. The results of the analyses showed that the coefficient of subgrade reaction be of the order of magnitude as small as 2 x 10■■ - 2 x 10■■ for the soil-pile interaction undergoing lateral flow of soils. This paper intends to present a summary of the previous works in the above context.
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