Stability Assessment of a Deadman Anchor Pile Close to the Bulkhead Wall-Paper

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The paper assesses whether existing steel pipe piles can safely anchor a nearby bulkhead wall when the piles’ passive soil resistance is constrained by the wall. Because the piles are close to the bulkhead, their passive soil wedges are truncated, reducing the resistance available to counter the tie-back load.<br /><br />Finite element analyses found that the unanchored bulkhead did not meet the required safety factor of 1.5. A horizontal tie-back force of approximately 5.5 kips per foot of wall was needed to achieve the target stability. Conventional retaining-wall calculations produced similar results.<br /><br />To estimate the piles’ reduced lateral resistance, the study applies the Coulomb wedge method to the truncated soil wedge. The resulting resistance reduction is then used in two pile assessments: conventional soldier-pile equilibrium analyses and Winkler p-y spring analyses in LPILE. The analyses consider pile-to-wall distances of 16 and 40 feet.<br /><br />At 40 feet, the pile met the target geotechnical safety factor in the soldier-pile analysis, and its calculated bending demand remained below the assumed allowable capacity in both analysis methods. At 16 feet, the soldier-pile safety factor was only 1.03, and the LPILE bending demand slightly exceeded the assumed allowable capacity. Thus, piles close to the bulkhead may lack adequate geotechnical or structural capacity to carry the required tie-back force.<br /><br />The study concludes that truncated-wedge analysis is appropriate when conventional methods assume soil wedges can fully develop. It also provides a basis for reducing pile resistance in soil–pile interaction analyses. The findings indicate that piles less than about 40 feet from the wall require careful evaluation and may not be suitable without design changes.

Keywords

steel pipe piles

bulkhead wall

passive soil resistance

truncated soil wedge

tie-back force

finite element analysis

Coulomb wedge method

soldier-pile analysis

LPILE p-y springs

geotechnical safety factor