Static pile load test

How bridges get built · Site investigation and testing · Static pile load test

Also called: maintained load test, kentledge test, reaction pile test

Concept diagram (TheBridgeEng)

How it is done

Install a test pile identical to the production piles, ideally before production starts so the design can still change.
Provide reaction: kentledge (dead weight) or reaction piles with a crossbeam.
Load in maintained steps, holding each until settlement stabilises, to a proof load or to failure.
Instrument with strain gauges down the shaft to separate shaft and base resistance; interpret with Davisson, Chin or the local code method.

Where it fits

Any project with more than a few dozen piles or with uncertain ground; contractual acceptance testing.
New pile types or ground the contractor has not worked in.

Where it does not

Testing a pile that is not representative (different length, different installation method).

Plant, pace and money

PlantKentledge of 500-3,000 t or reaction piles, hydraulic jacks, load cell, dial gauges or LVDTs on a reference beam.

ProductivityTwo to five days per test including setup; reaction systems for large piles take a week.

CostUSD 60,000-250,000 per test on land; double or more over water. The game charges this in the load-test step and in return converts ground surprises into quiet adjustments.

Risks and controls

What goes wrong

Kentledge instability, jack misalignment, testing too early after installation (setup effects in clay, relaxation in dense sand).

Quality assurance

Calibrated jacks and load cells, reference beams shaded from sun, test reports with load-settlement and strain distributions.

Examples

Sea bridge projects commonly run two or three static tests per foundation type; O-cell tests replace kentledge for very large shafts.