Limit States and Factor of Safety in Design of an Anchored Sheet Pile Wall

Factors of safety in the traditional design of anchored sheet pile walls have been introduced in a variety of ways. Furthermore, empirical and semiempirical factors are used to modify the calculated depth of embedment, anchor rod force, and maximum bending moment in sheet pile. This leads to a range of designs within the traditional allowable stress design (ASD) approach.

Even in the new ultimate limit states design (LSD) method, two approaches are available. One approach is to use load and resistance factor design (LRFD), and the other is to use partial safety factors on the material properties in combination with load factors. In view of the number of design alternatives available, a calibration study of LSD with ASD for an anchored bulkhead was performed. The practical problem of a sheet pile wall in a layered cohesionless soil and cohesionless soil overlying cohesive soil was analyzed.

The depth of embedment, the anchor rod force, and the maximum bending moment in sheet pile were determined for a range of soil parameters by using LSD and ASD methods. The factors recommended in various codes, manuals, and handbooks were used to perform calibration studies. The results of the parametric study indicate that the load and resistance factors recommended in the LRFD approach must be reevaluated.

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