UPLIFT OF SEWER PIPES CAUSED BY EARTHQUAKE-INDUCED LIQUEFACTION OF SURROUNDING SOIL

抄録

A series of shaking table tests are made to investigate the uplift behavior of sewer pipes caused by liquefaction of surrounding soil. It is shown that uplift displacement of pipes buried in unliquefiable original soil, which does not allow a dissipation of excess pore water pressure from liquefied backfill soil, increases drastically when they are subjected to extensive shaking. Uplift displacement of pipes buried in liquefiable original soil, on the other hand, accumulates rather gradually even at moderate shaking. A different behavior on residual deformation of the backfill and the original soils is also observed. In relation to the effects of soil condition, damage to sewer pipes in Towada City caused by the December 28, 1994 Sanriku-Haruka-Oki earthquake is reported and discussed. It is estimated that upper backfill soil consisting of sandy gravel may have liquefied because it was under loose and saturated condition and was subjected to earthquake motion under nearly undrained condition due partly to its own low permeability and also to the existence of surrounding original soil with low permeability.