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The maximum moments generally oc-cur at slightly higher elevations on walls constructed by the back-fill method compared to excavation cases (Fig. 12b).4.4. Anchor forcesThe anchor force is one of the critical parameters in the designof anchored sheet pile walls. The anchor forces obtained from theanalysis of all 12 cases for excavation and backfill constructionmethods are shown in Fig. 13. The figure shows that the anchorforces in walls constructed by the backfilling method were eithervery close to or slightly lower than the ones constructed by exca-vation method. All the walls constructed by the backfill methodon relatively denser foundation soils result in lower anchor forces17% less on average, compared to excavation cases.5. Summary and conclusionsA numerical study using finite element analysis was conductedto investigate the effect of excavation and backfilling constructionmethods on the behavior of anchored sheet pile walls in cohesion-less soils. Different backfill and foundation soil conditions and wallheights were considered in the parametric study. Although com-monly used conventional design methods do not differentiate be-tween excavation and backfilling construction methods, the finiteelement modeling and analysis revealed significant differences inanchored sheet pile wall behavior when constructed by differentmethods. The following discussion, conclusion, and recommenda-tions are based on the extensive numerical experiment performedusing finite element analyses. The following conclusions are drawnbased on the results of this study: Although there are some differences in earth pressure distribu-tion, the effect of construction method on total lateral earthloads acting on the wall is minimal. Walls constructed by thebackfill method result in lower lateral earth pressures behindthe wall above the anchor level. While the application locationof the passive earth load resultant is not affected by the con-struction method, the active earth load is at a slightly lower ele-vation in backfill cases compared to excavation cases. Wall deformations are affected significantly by the constructionmethod. The walls constructed by the backfilling method haveapproximately 54% higher wall deformations, on average, com-pared to excavation cases. Effect of construction is more signif-icant when the walls are penetrated into weaker soils.
For thecases studied, the maximum wall deformations of backfill casesare approximately 25% higher, on average, when stronger foun-dation soils are present, while maximum deformations areapproximately 71% higher, on average, when the foundationsoils are loose. The effect of construction method is even moresignificant when the wall tip deformations are considered.Approximately five times more pile tip deflections are encoun-tered for the walls constructed in loose foundation soils. In excavation cases, almost 50% of the final wall deformationsand bending moments occur during the last stage of construc-tion. Because of large deformations and significant increases inbending moments occurring towards the end of construction,the wall failures in excavation cases are expected to be morecatastrophic and without enough warning. In backfill cases, onthe other hand, the wall deformations occur gradually, i.e. morecontrolled deformations, which is good for monitoring purposesduring construction to prevent sudden failures. The method of wall construction also affects the wall bendingmoments significantly. The walls constructed by the backfillmethod have approximately 34%, on average, higher bendingmoments compared to the walls constructed by excavationmethod. Anchor forces are also affected by the wall construction method.The results are more conclusive and consistent for the wallspenetrated in stronger foundation soils. For these cases ana-lyzed, the anchor forces are always lower, approximately 17%on average, in backfill cases. On the other hand, when the foun-dation soils are weak, the backfill cases resulted in slightlyhigher anchor forces for relatively shorter walls. The anchorforces are almost the same in both methods for higher walls.References[1] Clough GW, O’Rourke TD.