Research on the Dynamic Shear Deformation due to Earthquakes Contributingto Uplift of Underground Structures

摘要

For checking of uplifting of underground structures due to liquefactionrnduring the design of such structures in Japan, a formula based on thernbalance between the buoyancy acting on the structure from thernliquefied soil and the dead load of the structure is used. The authorsrnconsider that (1) the liquefied soil applies considerably large dynamicrnloads on underground structures during an earthquake and the verticalrncomponent induces the uplifting of structures, and that (2) a verticalrnforce larger than the statically acting buoyancy is highly likely to act onrnstructures resulting in structures being uplifted only by the verticalrnforce. In this study, to understand the action of the soil pressure on thernpipe in liquefied soil during earthquake, shaking table tests werernconducted. As result of the test, the following has been understood. Therngreater the shear strain of soil around the structure became, the largerrnvertical force induced by incremental earth pressure acted on the pipe.rnIt was thus suggested that if the structure is subjected to shearingrndeformation together with the surrounding soil, upward vertical forcernacts on the structure. If it was a pipe of 1.25t/m3 in the appearancerndensity, it was shown to surface by this action. In order to prove thesernhypotheses, shaking table tests are performed in this study.