Abstract
In general, underground structures significantly lose a stability when the supporting soil liquefies due to a seismic motion. In particular, a decrease in the bearing capacity of the backfill due to liquefaction leads to the serious damages of pressure pipelines subjected to thrust force. Nevertheless, the specific liquefaction-countermeasures for the backfill material of pipelines has not been described sufficiently in the present design criteria for irrigation pipelines. It is crucial to clarify the interaction between the lateral resistance force of the liquefied soil and the displacement of the pipeline. In the present study, we conducted lateral loading experiments to examine the influence of the loading rate of the pipe on the lateral resistance force of the sandy soil under different hydraulic gradient. The experimental results showed different types of velocity dependence of the lateral resistance force depending on the excess pore water pressure. In the saturated sand, the lateral resistance force decreased with the increase of the loading rate because the excess pore water pressure on the passive side of the pipe increased rapidly. On the other hand, in the perfectly liquefied sand, the lateral resistance force increased linearly with the loading rate of the pipe.
