Effective Utilization and Cost Reduction of Temporary Cutoff Walls as Preventive Measures against Liquefaction

In this paper, we discussed the effectiveness and cost reduction of using temporary cutoff walls as preventive measures against liquefaction. The U-type retaining walls studied here are based on the liquefiable soil strata. We carried out a comparative study for the effectiveness and cost of some preventive measures against liquefaction. We concluded that making use of cutoff walls is most effective in terms of preventive effect and cost reduction. Effective stress analyses revealed that the stresses of cutoff walls were almost within the allowable stresses under seismic loading. We found that the rigidity between cutoff walls and underground structure plays an important role for the safety of cutoff walls. A quantitative estimation method was verified to be valid for the principle of this countermeasure that “The liquefiable soil just below the underground structure is made as a closed space”. As the result, it is concluded that the practical design method of cutoff walls against liquefaction is shown here based upon the results calculated by a beam-spring model taking the decrease in rigidity of non-liquefiable layer, liquefied soil-water pressure acting against the wall, and so on, into consideration.