Driven pile foundations field guide for deep-foundation crews

What a driven pile is

A driven pile is a steel, precast-concrete, or timber member hammered into the ground with a pile hammer until it reaches firm soil or a driving resistance that proves it will carry the load. As it goes down it pushes the soil aside, which is why it belongs to the family called displacement piles. The same operation that installs the pile also tests it. The harder the soil fights the hammer near the bottom, the more blows it takes to advance the pile, and that blow count correlates to the capacity the finished pile will hold.

That is the thing that sets driven piles apart from a footing or a cast-in-place shaft. You get a running read on capacity as the pile goes down, and you confirm it with load testing, so the install and the verification happen together instead of waiting on concrete to cure. Driven piles suit heavy loads, deep soft soil sitting over a firm stratum, and marine and heavy civil work where the pile has to be driven through water or weak ground to reach something solid.

The reliability comes from three things, and every section here circles back to them. The engineer sets the driving criteria. The hammer and the cushion are matched to the pile so it is not cracked on the way down. And the capacity is verified by testing, not guessed from the field. For the cast-in-place alternative that drills a hole instead of displacing soil, see the drilled pier and caisson guide. For the lighter, screwed-in alternative, see the helical pier and screw pile guide.

How does a driven pile carry load?

A driven pile carries load two ways at once, and the split between them depends on the soil. End bearing is the tip of the pile pressing on firm soil or rock at the bottom, the same way the base of a footing bears on the ground beneath it. Skin friction, also called shaft resistance, is the load shed into the soil along the sides of the pile through friction and adhesion over its full length. Add the two and you have the pile's capacity.

Which one does the work is a design call. A pile driven through soft soil until the tip lands on dense sand or rock leans on end bearing. A long pile through deep firm clay can carry most of its load in friction before the tip does much at all. Most production piles use both, and the engineer's analysis sets how much each contributes.

The displacement part matters more than people expect. A driven pile does not remove soil, it shoves it aside and down, which densifies the ground around the pile in granular soils and can raise the friction it picks up. That same displacement is what shakes the neighbors and heaves the ground, covered later. The load path runs from the column, into the cap, down the pile, and out into the soil through the sides and the tip. That path only works if the pile is sound and the tip bears on firm material, which is exactly what the blow count and the load test are there to prove.

When are driven piles used?

Driven piles earn their place when the loads are heavy and the good ground is deep or under water. A bridge pier in a river, a building where the bearing stratum sits forty or eighty feet down under soft clay, a wharf or a dock, an industrial structure carrying heavy column or crane loads. In all of these a spread footing near the surface cannot reach strong enough ground, and the pile drives the load down to where the soil or rock can hold it.

They are fast and they prove themselves as they go, which is the real draw. A pile crew can install and verify a lot of capacity in a day, and the driving record is the test. Precast concrete and timber piles come to the site finished, so there is no cure time before the next trade can build on the cap.

Where they lose is vibration and displacement. Driving shakes the ground and pushes soil aside, so on a tight urban site next to existing structures, a drilled shaft or a helical pier that makes no vibration is often the better tool. Whether a driven pile beats a drilled shaft or a helical pier on a given job is the geotechnical and structural engineer's call, set by the boring logs, the loads, and the site, not by what the crew ran last week.

Pile types: steel, concrete, and timber

The material is chosen for the load, the soil, the environment, and how hard the pile has to be driven to reach bearing. Steel takes the hardest driving and reaches the deepest. Precast and prestressed concrete carries high loads economically in less brutal driving. Timber is the light, traditional option with real limits. None of this is the crew's pick. The engineer specifies the pile type and section, and the spec calls the material.

Steel piles: H-piles and pipe piles

Steel piles take the worst the soil can give. They drive through dense layers and obstructions that would crack a concrete pile and they reach rock at depth, which is why they show up on the heaviest and deepest work.

The H-pile is a rolled steel section that drives with low displacement, meaning it slices into the ground without pushing much soil aside, so it shakes the neighbors less and works well driven to end bearing on rock. The flip side is that a long H-pile can wander off line in hard driving or fold over on an obstruction, and the tip sometimes gets a cast steel point where the driving is rough. The pipe pile comes open-end or closed-end. A closed-end pipe, capped with a flat or conical plate, is a full-displacement pile and develops more friction. An open-end pipe drives easier and with less displacement but can plug with a soil core, or need cleaning out and filling with concrete.

Corrosion is the long-term question for steel in the ground, and it is the engineer's to answer. Soil that is wet, low in resistivity, or near salt water eats steel, and the design handles it with a sacrificial thickness allowance, a coating, cathodic protection, or concrete fill, depending on the exposure. The spec sets the corrosion allowance. Do not assume bare steel is fine because the pile looks heavy.

Concrete piles: precast and prestressed

Precast concrete piles are cast and cured at a yard, then trucked in and driven. Most production concrete piles are prestressed, meaning the strands are tensioned before the concrete is cast so the finished pile carries a built-in compression that keeps it from cracking under handling and driving stress. They carry high vertical loads, hold up in marine and corrosive ground far better than bare steel, and arrive finished.

The catch is that concrete is strong in compression and weak in tension, and driving puts both into the pile. Every hammer blow sends a compression wave down, and when the tip is in soft soil with little resistance, a tension wave can reflect back up and crack the pile. That is why the prestress and the cushion matter so much, and why early driving in soft ground is run with reduced energy. Over-drive a concrete pile and you get spalling at the head or transverse cracks down the body, and a cracked pile in the ground is a defect you cannot fix.

Handling is its own hazard. A long precast pile picked at the wrong points cracks before it ever reaches the leads, so the lift and support points are set by the design. Concrete piles are also hard to splice cleanly, so they are usually ordered to length, and the length comes from the boring logs and the engineer, not a guess in the field.

Timber piles

Timber piles are the oldest driven pile there is, and they still work. They are cheap, light, fast to drive, and whole districts of old cities sit on timber piles driven a hundred years ago and still sound, because they stayed below the permanent water table.

The limits are real. Timber carries modest loads, comes in limited lengths, and cannot take hard driving without brooming at the head or splitting, so it is driven with a steel band or cap and sometimes a tip point. Above the water table, or in the tidal zone where it cycles wet and dry, untreated timber rots and marine borers eat it, so piles are pressure-treated with preservative for any permanent exposure. For heavy loads or deep hard driving, timber is the wrong tool, and the engineer will spec steel or concrete instead.

The pile hammers

The hammer is the engine of the whole operation, and matching it to the pile and the soil is the difference between a pile driven to capacity and a pile cracked on the way down. Impact hammers drive with a falling ram. Diesel hammers fire a ram up with a diesel combustion stroke and have powered most production driving for decades, cheap and self-contained but with a stroke that varies with soil resistance. Hydraulic impact hammers are the modern version, driving the ram with a hydraulic power pack, with a controllable and measurable energy that makes them the choice where driving stress and energy have to be held tight.

Energy is the number. A hammer delivers a rated energy per blow, the ram weight times the stroke, and that energy has to be enough to advance the pile against the soil but not so much that it over-stresses the pile. Too small a hammer beats the pile forever without moving it and racks up blows that mean nothing. Too large a hammer cracks the pile. The right hammer is sized by a driveability analysis, the wave equation, before the rig ever shows up, and the engineer signs off on the hammer and the driving system. The hammer on the job is part of the driving criteria, not an interchangeable detail.

Impact hammers vs vibratory hammers

An impact hammer hits the pile; a vibratory hammer shakes it. The difference governs which one you can use to prove capacity, and the two are not interchangeable.

An impact hammer drives with discrete blows, so it produces a blow count, the blows per foot or per inch that correlate to bearing capacity. That blow count is the field measure that proves an end-bearing or friction pile, and it feeds the wave equation and the dynamic test. A vibratory hammer clamps the pile head and shakes it at high frequency, fluidizing granular soil so the pile sinks fast under its own weight and the hammer's. It is the fast tool in sand and the standard tool for sheet piles and for extracting piles and casing.

The trap is bearing. A vibratory hammer gives you no blow count and no reliable measure of capacity, so a bearing pile installed with a vibratory hammer usually has to be finished, or restruck, with an impact hammer to prove it, or verified by a load test. Plenty of trouble traces back to a pile vibrated to grade in granular soil and accepted without anyone confirming the bearing the design needed. The engineer and the spec decide what the vibratory hammer is allowed to install and what has to be proven with an impact hammer.

What are the driving criteria for a pile?

The driving criteria are the rule that tells the crew when a pile is in far enough to stop. The engineer sets them, and they take one of two forms, often both at once: drive to a minimum tip depth, and drive to a blow count that indicates the required capacity. The depth makes sure the pile reaches the bearing stratum and has enough length for friction and lateral support. The blow count makes sure it actually found the resistance the design needs.

This is the heart of the job, so be blunt about it. The blow count that means a pile is done is not a number the crew picks and not a rule of thumb off a chart. It comes from the engineer's analysis of the specific pile, hammer, and soil, usually through a wave equation study, and it is tied to the hammer that is actually on the job. Change the hammer, the cushion, or the stroke and the criterion changes with it. A pile driven to 8 blows per inch with one hammer is not the same capacity as 8 blows per inch with another.

When the field and the criteria disagree, that is information, not a nuisance. A pile that hits the blow count far short of the design depth, or one that drives past the depth without making the count, tells the engineer the soil is not what the borings showed, and that gets a call before the next pile goes in, not after the cap is poured. The driving criteria belong to the engineer, the spec, and the AHJ. The crew drives to them and records every foot.

What is blow count, refusal, and set?

Blow count is the number of hammer blows it takes to advance the pile a set distance, recorded as blows per foot for most of the drive and blows per inch near the end where it counts. As the pile tip reaches firm soil the blow count climbs, and the rate it climbs is the field's read on the capacity building under the tip.

Set is the inverse, the penetration per blow, and it means the same thing from the other direction. A pile that moves a quarter inch per blow has a set of a quarter inch. Refusal is the point where the pile has effectively stopped advancing under the hammer. Practical refusal is often taken around 10 blows per inch, or roughly 120 blows per foot, in firm material, but that figure varies with the pile, the hammer, and the spec, and it is the engineer's call, not a fixed law. Driving past true refusal does not add capacity. It damages the pile and the hammer.

The blow count is the cheapest, most continuous capacity proof you have, but it is a correlation, not a direct measurement. It tells you the soil resistance the hammer is overcoming at that moment, which includes temporary resistance that fades, so a high blow count at the end of driving is confirmed, where it matters, by a restrike after a wait and by dynamic or static testing. Record the blow count for every foot of every pile. That log is the proof the pile was driven to the criteria.

The dynamic formula vs the wave equation

For a century the trade estimated capacity from a dynamic formula, the simplest being the Engineering News-Record, or ENR, formula, which sets capacity from the hammer energy, the ram weight, and the set per blow. It is easy to compute on the spot, and it is also unreliable, because it treats the pile as a rigid body and ignores how the stress wave actually travels down it. Many transportation departments and modern specs no longer accept the ENR or other dynamic formulas for final pile acceptance, and where they appear at all it is as a rough field check.

The wave equation replaced it. A wave equation analysis, run in software the trade calls GRLWEAP, models the hammer, the cushion, the pile, and the soil as a system and simulates the stress wave traveling down the pile with each blow. It produces a bearing graph, a curve of blow count and driving stress against capacity, so once the field blow count is known the engineer reads the capacity and confirms the pile was not over-stressed getting there. The same analysis is what sizes the hammer and sets the driving criteria before the job starts.

The wave equation is the design and acceptance tool; the dynamic test confirms it in the field. None of this is the crew's to compute. The engineer runs the analysis, sets the criteria, and the spec and the AHJ say what method governs acceptance on the job.

Dynamic pile testing (PDA and CAPWAP)

Dynamic testing measures what the pile actually does under the hammer instead of inferring it from the blow count alone. Strain transducers and accelerometers are bolted near the pile head and read the force and velocity of the stress wave from each blow into a Pile Driving Analyzer, the PDA, under ASTM D4945 high-strain dynamic testing. In real time it gives an estimate of capacity, the driving stresses in the pile, the hammer energy actually delivered, and the pile integrity.

The deeper analysis is CAPWAP, a signal-matching program that takes the measured force and velocity and back-calculates a model of the soil resistance, splitting it into shaft friction and end bearing and refining the capacity estimate. That is the number the engineer trusts from a dynamic test. Run during initial driving, it checks stresses and hammer performance. Run on a restrike after a wait, it captures the soil setup or relaxation that the end-of-drive blow count cannot see.

Dynamic testing is fast and cheap enough to run on a sample of production piles, which is why it has become the common verification on real jobs. How many piles get tested, and whether a static test is also required, is set by the engineer, the spec, and the AHJ, not by the crew.

The static load test

The static load test is the benchmark every other method is measured against. A known load is applied to the pile in increments, usually with a hydraulic jack reacting against a beam loaded with weight or anchored to reaction piles, and the settlement is measured at each step. Axial compression testing follows ASTM D1143, with companion methods for tension, ASTM D3689, and lateral load, ASTM D3966.

It is the most direct and reliable measure of capacity there is, and it is also slow and expensive, so it is run on a small number of piles, often a sacrificial test pile driven before production to confirm the design and calibrate the driving criteria. The dynamic test and the wave equation are then used to extend that result across the production piles.

When the engineer lacks confidence in the dynamic data, or the loads and the consequences are high enough, the static test is what settles it. The number of tests, the load schedule, and the acceptance criteria are the engineer's and the spec's, confirmed with the AHJ. A static test is the one result that does not argue with the others.

Controlling driving stress

Every hammer blow sends a stress wave through the pile, and that stress can break the pile as surely as the soil it is fighting. Controlling it protects the investment already in the ground. The compression wave running down can crush or spall the pile head and tip. In a concrete pile, the reflected tension wave, worst when the tip is in soft soil with little resistance, can crack the body, because concrete has little tension capacity beyond its prestress.

The controls are the cushion and the hammer energy. A pile cushion, a stack of plywood or engineered material on top of a concrete pile, plus a hammer cushion in the helmet, softens the blow and spreads it out so the peak stress stays under the pile's limit. Concrete piles run a thicker, softer cushion stack than steel for that reason, and the cushion gets checked and changed as it crushes and burns down through a long drive. Early driving in soft ground is run at reduced stroke and energy to keep the tension wave down until the tip finds resistance. Common practice holds driving stress in concrete below a fraction of its compressive strength and in steel below most of its yield, but the exact allowable stresses are the engineer's, set in the wave equation analysis and confirmed by the dynamic test.

Match the hammer to the pile, watch the cushion, and bring the energy up as resistance builds. Beat a pile with too much hammer or a dead cushion and you crack it, and the crack goes in the ground where no one finds it until the pile fails to test.

The pile cap

The pile cap is the reinforced concrete block that ties a group of piles together and transfers the column load down into them. A single column almost never sits on a single pile, because a lone pile cannot resist the bending and the slight eccentricity that real construction always has, so piles are driven in groups of two, three, four, or more and capped.

The cap spreads the column load across all the piles in the group and ties them so they act together. It is a thick, heavily reinforced element, designed for the shear and the bending of the load fanning out from the column to the piles, with the pile heads embedded into the bottom of the cap and the column dowels lapping the cap steel above. The pile heads are usually trimmed to a clean elevation and the reinforcing exposed and developed into the cap so the connection can carry tension as well as compression.

The cap design is the structural engineer's, and it depends on the as-driven pile locations, not the planned ones. Piles wander during driving, and a pile that ends up out of position changes the load it carries and can force the cap to be redesigned. That is one more reason the as-driven survey of every pile head matters.

The pile group and group effect

Piles in a group do not each carry what a single isolated pile would, and that is the group effect. When piles are driven close together, their stress zones in the soil overlap, so the group can settle more and carry less per pile than the sum of the individuals, especially in clay. The ratio of the group's capacity to the sum of the single-pile capacities is the group efficiency.

Spacing is the lever. Piles are spaced far enough apart that the group effect stays manageable, with a common minimum center-to-center spacing around three pile diameters, though the exact spacing is the engineer's call from the soil and the load. Drive them too close and you lose efficiency, increase the heave and the driving difficulty as each pile densifies the ground for the next, and risk pushing earlier piles out of position.

Group settlement is governed by the block of soil under the whole group, not the single pile, so a group can pass a single-pile load test and still settle more than expected as a group. That is the engineer's analysis, and it is why the spacing, the pile count, and the cap are designed together, not pile by pile.

How much vibration does pile driving cause to neighbors?

Driving piles shakes the ground and it is loud, and on an urban site that is the problem that stops the job, not the engineering. Each blow sends vibration through the soil that can crack plaster, settle a neighbor's foundation, or rattle sensitive equipment, and the noise draws complaints fast. Granular soils are the real settlement risk, because the vibration can densify loose sand and pull down anything sitting on it, including the building next door.

Protect yourself before the first pile. Do a pre-construction survey of the surrounding structures, documenting existing cracks and conditions with photos and notes, commonly out to a few hundred feet, so a pre-existing crack does not become your claim. Set vibration monitors, seismographs reading peak particle velocity, on the at-risk structures, and hold the driving to a vibration limit. Limits vary with the structure and the soil, and the engineer and the AHJ set the threshold.

When the vibration or settlement risk is too high, the answer is often a different foundation. A drilled shaft removes soil instead of displacing it, and a helical pier is screwed in, so both make far less vibration than driving, which is exactly why they win next to fragile existing structures. That trade is the engineer's call, and it runs through the comparison section below.

Ground heave and adjacent structures

A driven pile is a displacement pile, and the soil it pushes aside has to go somewhere. In clays and dense soils that often means the ground surface heaves up and moves laterally as each pile goes in, which can lift piles already driven, shove a nearby retaining wall or utility, or disturb an adjacent foundation. The same displacement that builds friction on the pile is what moves the ground around it.

Heave is worst in saturated clay, where the soil cannot compress fast enough, so it rises. Piles already driven can be lifted off their bearing by later piles nearby, which is why driving order matters and why piles are sometimes re-driven, or the set rechecked, after the surrounding piles are in. In loose granular soil the displacement densifies instead of heaving, which usually helps capacity but still moves the ground.

Where adjacent structures or utilities are close, the monitoring covers movement as well as vibration, with survey points read as driving progresses. How much movement is tolerable, and what the driving sequence has to be, is the engineer's call from the soil and what sits nearby.

Splicing piles

Piles get spliced when the pile has to go deeper than a single length will reach, which on deep sites is most of them. The pile is driven until its head is near grade, a second length is joined on top, and driving continues.

Steel splices fast and well. An H-pile or pipe pile is spliced with a full-penetration weld, often with a manufactured splice sleeve or fitting to align the sections, and a sound splice develops the full strength of the pile so it drives and carries as if it were continuous. The weld is inspected, because a bad splice is a hinge in the pile right where the driving stress runs through it. Concrete piles are harder, joined with mechanical splice connectors cast into the ends or a dowelled and epoxied connection, and they are slower and more particular, which is part of why concrete piles are usually ordered to length instead.

A splice is a structural connection in the load path, so the detail is the engineer's and the inspection is real. The number, the location, and the type of splice get recorded on the pile log with everything else.

Set-check, restrike, soil setup, and relaxation

A pile's capacity is not fixed at the moment driving stops. In many soils it keeps changing for days as the soil around it recovers, and the field has names for both directions. Soil setup, sometimes called freeze, is a gain in capacity over time, common in clays and silts, where the disturbed soil reconsolidates and the friction climbs well above what the end-of-drive blow count showed. Relaxation is the opposite, a loss of capacity after driving, seen in some dense fine sands and weathered shales where driving builds a temporary resistance that bleeds off.

This is why the restrike exists. After a waiting period, often a day or more set by the engineer and the soil, the crew restrikes the pile with a few blows and reads the set or runs a dynamic test. A restrike that takes more blows to move the pile confirms setup, and the design can sometimes credit that gain. A restrike that moves easily warns of relaxation, and that pile may need to go deeper or get help.

The set-check at the end of driving and the restrike after the wait are two different measurements, and both belong in the record. Whether a pile gets credit for setup, or how long the wait has to be, is the engineer's call, confirmed by testing, not a field assumption.

Driven vs drilled vs helical piles

All three are deep foundations that carry load to firm soil by end bearing and friction, and the choice comes down to how the pile gets into the ground and what the site will tolerate.

A driven pile is hammered in, displacing soil. It is fast, it proves capacity through the blow count and load testing, and it takes the heaviest loads to the deepest hard strata, but it shakes the ground, heaves the soil, and is loud, which is the problem on tight urban sites. A drilled shaft, the drilled pier or caisson, is cast in place in a bored hole. It makes no driving vibration and carries enormous single-shaft loads, but it produces spoil to haul and depends on a clean hole and uncontaminated concrete you cannot inspect once it is poured. A helical pier is screwed in with a machine, and the installation torque correlates to capacity. It makes almost no vibration, installs in tight low-headroom spots, and goes on fast, but it carries lighter loads than driven or drilled piles.

The short version: driven for heavy load and fast blow-count proof where vibration is acceptable, drilled for the heaviest single-element loads with no vibration, helical for lighter loads, tight access, and underpinning. The pick is the geotechnical and structural engineer's, from the loads, the soil, and the site. For the cast-in-place option see the drilled pier and caisson guide, and for the screwed-in option see the helical pier and screw pile guide.

The pile log and inspection

The pile log is the proof the pile was driven right, and on a driven-pile job it is the single most important record the crew produces. For every pile the inspector and the crew record the blow count per foot, and per inch near the end, the final set, the tip elevation and total penetration, the hammer and cushion used, the stroke or energy, any splices, and anything unusual like a sudden change in driving or an obstruction. That record is what the engineer reads to confirm the pile met the driving criteria.

Driven piles are deep foundations, so they fall under special inspection, and a qualified inspector typically witnesses the driving and the load testing and signs the record. The inspector is watching the blow count against the criteria, the hammer performance, the pile for damage, and the position and plumb of each pile as it goes in. A pile that drives wrong, too easy, too hard, or off line, gets flagged in the moment, because once it is in the ground and capped, the chance to fix it is gone.

A clean, complete, per-pile log is hard to keep on a paper clipboard in the mud, which is where a field tool earns its place. Logging the blow count, the set, the hammer data, and the as-driven location for each pile in FieldOS as the rig works keeps the record straight, time-stamped, and ready for the engineer's sign-off instead of reconstructed from memory after the fact.

What to document

The driving record, the testing results, and the as-driven survey are what prove the foundation and what the engineer signs off on. Capture them per pile, as the work happens, not after. A driving record reconstructed from memory is worth little, and on a deep-foundation job that record is the difference between a clean closeout and an argument.

Common mistakes

• Driving piles with no engineer-set driving criteria, so nothing proves the capacity.
• Over-driving a concrete pile and cracking it, then burying the defect in the ground.
• Installing a bearing pile with a vibratory hammer and accepting it with no blow count and no load test.
• Ignoring vibration and settlement to the neighbors, with no pre-construction survey and no monitoring.
• Skipping dynamic or static load testing and trusting the blow count alone.
• A poorly made or uninspected splice that becomes a hinge in the load path.
• Designing the cap from the plan pile locations instead of the as-driven survey.
• Treating practical refusal as a target and beating the pile past it for no added capacity.

Field checklist

Standards and references

The geotechnical and structural engineer owns the design and the driving criteria. The geotechnical report and the borings set the soil profile and the bearing stratum, the structural engineer sizes the piles and the caps, and together they set the minimum depth and the blow count a pile has to make. None of those numbers are the crew's to invent.

The verification methods have standards behind them. The wave equation analysis, run in GRLWEAP, sizes the hammer and sets the driving criteria. Dynamic testing follows ASTM D4945 with CAPWAP signal matching for the capacity, and the static load test follows ASTM D1143 for axial compression, with ASTM D3689 for tension and ASTM D3966 for lateral load. The International Building Code carries the deep-foundation provisions in its foundation chapter, and deep foundations fall under special inspection, so a qualified inspector witnesses the driving and the testing. Exact chapter and section numbers and the adopted edition vary, so confirm them against the code the jurisdiction has actually adopted and any local amendments.

Three things carry across all of it. Capacity comes from the engineer's driving criteria and the load testing, not from a number the crew guesses in the field. The driving stress is controlled and the hammer is matched to the pile so it reaches capacity without being cracked. And the vibration and settlement to the neighbors are watched while every pile is logged. Hedge the blow count, the criteria, and the testing to the engineer, the spec, and the AHJ, every time.

Units and terms

Driven piles carry a vocabulary that shows up across the geotechnical report, the structural drawings, and the spec, and the same idea reads a little differently in each.

Driven pile

A steel, concrete, or timber member hammered into the soil to carry load, displacing soil as it goes

End bearing vs friction

Load carried at the pile tip on firm soil versus load shed along the shaft into the soil

Displacement pile

A pile that pushes soil aside as it drives, rather than removing it like a drilled shaft

Impact vs vibratory hammer

A hammer that drives with discrete blows and a blow count, versus one that shakes the pile in with no blow count

Blow count

The number of hammer blows to advance the pile a foot or an inch, the field read on capacity

Refusal and set

The point where the pile stops advancing under the hammer, and the penetration per blow

Wave equation

A model of the hammer, pile, and soil that relates blow count and stress to capacity, run in GRLWEAP

Dynamic load test

High-strain testing, PDA with CAPWAP, that measures capacity and stress from the driving blows under ASTM D4945

Static load test

A direct load applied to the pile with settlement measured, the benchmark capacity test under ASTM D1143

Related tools

Calculators and readiness checks for this work

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FAQ

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