Soil-pile interaction in liquefied deposits undergoing lateral spreading.
For the design of foundation piles subjected to lateral spreading of the ground, it is necessary to specify the lateral force acting on the pile body from the surrounding soil deposit which is moving as a result of liquefaction. In view of many design codes incorporating spring-supported beam system to model the soil-pile interaction, it may be reckoned reasonable to investigate the effects of the lateral flow in terms of how much the spring constant should be degraded as a result of softening of the soil due to liquefaction. In an attempt to clarify this aspect, back-analyses were made for cases of damage to foundations for which field data such as soil conditions and damage features are made available. As a result, it was found that the degree of degradation in the spring constants is dependent on the relative movement of the piles and surrounding soils. Analysis results showed that, for example, if the pile displacement is about 50% of the surrounding soil, the stiffness in the spring constant should be reduced to 1/1000 - 1/100 of the value which is generally assumed in the design practice considering non-liquefied conditions.