Series of triaxial and shaking table tests were carried out to compare repeated liquefaction behavior. / 再液状化挙動を比較するため一連の三軸試験および振動台モデル実験を実施した．
Triaxial Test / 三軸試験
In triaxial testing, it was found that the liquefaction resistance increased with liquefaction stages. This increase was later discovered that it depended on the strain amplitude. The specimens subjected to low strain amplitude showed larger increase in resistance although an increase in relative density was smaller. It was even larger when the specimen was subjected to small strain.
三軸条件下では，液状化強度は液状化回数とともに増加し，その強度増加はひずみ振幅に依存することが分かった．小さなひずみ振幅を与えられた供試体では，液状化履歴毎の相対密度の増加は小さいにも関わらず，大きな液状化強度の増加が確認された．
Shaking Table Test / 振動台実験
For shaking table tests, series of repeated liquefaction tests were conducted with different starting input accelerations on flat ground models. The results showed that liquefaction resistance in the first shake event was always larger than the following event in every repeated liquefaction series. In addition, under the same input acceleration, the results revealed that future liquefaction resistance can be briefly predicted using current and previous maximum strain amplitude.
振動台実験では，模型成層地盤モデルに対して段階的（断続的）に加振を行い，加振毎の液状化特性を確認する．実験結果から，初期加振時における液状化強度が最も大きかった．加えて，同じ最大加速度の連続加振では，当該加振時およびそれまでの最大ひずみ振幅を用いることで，液状化強度が簡易的に予測できることが示唆された．
Comparison / 結果の比較
As stress and strain response cannot be controlled in shaking table, cumulative damage concept was employed to convert irregular cyclic stress response into equivalent uniform cyclic stress before comparing with triaxial results. Higher liquefaction and reliquefaction resistance was observed in shaking table test. Further investigation was also conducted using energy approach. It was found that relationship between dissipated energy during the previous liquefaction stage and the next liquefaction resistance was well defined for each test apparatus results.
振動台実験では，三軸試験のように応力ひずみ関係をコントロールすることができないため，累積損傷理論によって不規則な加振時地盤応答を等価な繰返し一定応力履歴に変換する．この変換を用いて，三軸試験と振動台実験を比較すると，振動台実験の方が液状化程度ならびに強度が大きくなることが確認された．さらに，応力ひずみエネルギーの概念を用いることで，直前の液状化時における消散エネルギーとその後の液状化強度に相関があることが，三軸試験ならびに振動台実験の両実験から示された．
More Details...
1)Teparaksa, J. and Koseki, J. “Behaviour of silica sand under repeated liquefaction using triaxial apparatus.” Proc. of the 18th International Summer Symposium, Japanese Society of Civil Engineers, 2016, pp.37-38
2)Teparaksa, J. and Koseki, J. “Comparison of silica sand behaviour under repeated liquefaction using shake table and triaxial test.” To be published in Proc. of the 18th International Summer Symposium, Japanese Society of Civil Engineers, 2017
3)Teparaksa, J. and Koseki, J. “Silica sand behavior under repeated liquefaction in cyclic triaxial test.” To be published in Proc. of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, September, 2017
