Optimization of Pile Foundation-Paper

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The study develops a computer program in C to optimize pile-foundation designs for cost while maintaining the required load capacity. Design calculations follow Indian Standards IS 2911 (Part I) for cast-in-situ piles and IS 2911 (Part III) for under-reamed piles. The program varies pile length, shaft and bulb diameters, number of piles and bulbs, and estimates concrete and earthwork volumes.<br /><br />Results indicate that shorter piles can be economical, but the best configuration depends on soil type. In non-cohesive soils with an internal friction angle above 30°, reducing pile length while slightly increasing shaft diameter can maintain capacity and reduce concrete volume. For larger-diameter piles, using multiple shorter, smaller-diameter piles may also be economical. These trends were not consistent in soils with lower friction angles.<br /><br />In cohesive soils, replacing a longer single pile with a shorter, larger-diameter pile generally increased material volume. However, using multiple shorter piles of smaller diameter could preserve or improve capacity while reducing concrete and earthwork volumes. Under-reamed piles could also be shortened economically by reducing stem diameter and increasing bulb diameter; the study found particularly favorable results with multiple piles and bulbs.<br /><br />Overall, the authors conclude that pile length restrictions do not necessarily prevent an economical design. Alternative combinations of pile dimensions and numbers can achieve equivalent or greater load capacity with less material. The findings are based on the study’s tested soil and design parameters, so suitable alternatives should be checked for each project.

Keywords

pile foundation design

cost optimization

Indian Standards IS 2911

cast-in-situ piles

under-reamed piles

load capacity

pile length

shaft diameter

bulb diameter

soil type