A large earthquake such as Nankai Trough Earthquake is concerned to occur in the near future and there is fear that coastal levees will sink by liquefaction. Authors proposed installing double sheet-piles into the levee and additionally combining another sheet-pile as a partition wall perpendicular to the extension direction to the levee. It has been confirmed by model tests that this countermeasure is very effective for the deformation/settlement reduction of levees during an earthquake. However, since the partition wall was modelled by the steel plate in the model tests, the effect of the joints between sheet-piles could not be taken into consideration. Authors also reproduced the model test results by using a two-dimensional effective stress analyses (code:LIQCA2D12) with high accuracy. In the numerical study, the slippage effect of joints between sheet-piles for the partition wall was taken into account. As a result, it was confirmed that the shear distortion generated between the joints weakens the constraint of the ground inside double sheet-piles, but in spite of this negative effect, the settlement of levee was reduced down to 15% compared to the case without countermeasure.