Design Considerations for Laterally Loaded Free-Head Rigid Piles in Engineering Practice-Paper

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The paper evaluates practical methods for estimating the ultimate lateral capacity of free-head rigid piles in cohesive and cohesionless soils. It compares conventional limiting-equilibrium approaches—Brinch Hansen, Broms, Matlock and Reese—with three-dimensional PLAXIS analyses, then checks a proposed simplified method against full-scale field tests.<br /><br />The comparison shows that conventional methods can produce substantially different capacity estimates. In cohesive soil, the methods generally underestimate capacity relative to PLAXIS 3D. In cohesionless soil, Brinch Hansen and Reese tend to underestimate capacity, while Broms tends to overestimate it. The finite-element analyses also indicate that actual soil-pressure distributions differ from conventional assumptions, particularly around the pile’s pivot point.<br /><br />The authors propose a simple pressure distribution for routine design. In cohesive soil, resistance increases linearly from 4.5 to 9 times the undrained shear strength over the upper 1.5 pile diameters, then remains at 9 times the shear strength below that depth. In cohesionless soil, resistance increases linearly from zero to 3 times the passive earth-pressure coefficient over the same depth, then remains constant below it.<br /><br />The proposed approach gives bending moments, shear forces and capacities that agree well with PLAXIS 3D results. It also predicts field-test capacities closely: 45 kN for a cohesive-soil test and approximately 441 kN for a cohesionless-soil test, compared with measured capacities of 45 kN and 440 kN, respectively. The authors recommend the method for routine design while noting that broader validation is needed.

Keywords

lateral capacity

free-head rigid piles

cohesive soil

cohesionless soil

Brinch Hansen

Broms method

Matlock and Reese

PLAXIS 3D

soil-pressure distribution

field test validation