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Performance of short anchors inside the failure wedge

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2019
Demir, Berk
The most widely accepted rule of thumb for anchor design is that bonded length of the ground anchors should be placed outside the failure wedge in order to increase resistance against overall stability. Moreover, failure wedge is defined as “no load zone.” This study investigates the performance of anchors inside and outside of the failure wedge by parametric studies performed through finite element analyses using Plaxis 2D and 3D. An anchored retaining wall with short and long anchors is compared with only long anchors in different arrangements. Seven long anchors (base model) are compared with additional seven short and long anchors to investigate the effect of anchor length on the retaining wall behavior. Also, different cases such as equal anchor quantity, equal addition to seven long anchors model and constant horizontal spacing are investigated. An efficiency term is defined to effectively compare these cases. Analyses have shown that anchors inside the failure wedge do not reduce factor of safety against overall stability, but decrease the lateral deformation of the retaining system. In fact, short anchors’ performance on decreasing lateral deformations is found to be better than long anchors for practical comparisons. Results are compared with 3D analyses, different finite element packages and soil models. Also, importance of modelling anchors using elasto-plastic models are emphasized. Lastly, anchor model and associativity analyses have been performed to reflect the effect of various elements on the failure surface.