Is an auger cast pile the same as a CFA pile?

Largely, yes. FHWA covers augered cast-in-place piles under continuous flight auger (CFA) piles, and in US practice the terms are often used interchangeably.

When does the steel go into an auger cast pile?

Last. The auger drills to depth, grout is pumped through its hollow stem as it is withdrawn, and the reinforcing cage or bar is then pushed down into the wet grout.

Do drilled shafts always need casing?

No. In stable ground above the water table a shaft can often be drilled without support. Casing or drilling slurry is used when the hole could cave or fill with water.

Can the contractor swap one foundation type for the other?

Not on their own. The foundation type is part of the engineered design, so any change goes through the geotechnical engineer and the structural engineer of record.

What does an N-value mean?

It is the number of hammer blows needed to drive the SPT sampler over the second and third 6-inch increments. Higher values generally mean denser or stiffer soil, and engineers often correct them for hammer energy before design.

How many borings does a site need?

There is no single number. The geotechnical engineer sets the number, spacing and depth of borings based on the size of the structure, its loads and how variable the ground is.

Does a boring show the groundwater level?

It records where groundwater was encountered during and after drilling. Groundwater can rise and fall with the seasons, rainfall and tides, so the engineer interprets the reading.

Is a soil boring the same as a percolation test?

No. A percolation test measures how fast water soaks into the ground, usually for drainage design. A soil boring samples and tests the ground with depth for foundation design.

Is Miami built on coral rock?

The local rock is often called coral rock, but much of the Miami Limestone near the surface is oolitic limestone, made of small rounded grains called ooids rather than coral reef.

Can auger cast piles be used below the water table?

Often, yes. The grout is pumped through the hollow stem and fills the hole from the bottom up as the auger is withdrawn. Whether they suit a particular site is the engineer’s decision.

Why does grout volume matter in limestone?

Grout that flows into voids does not stay in the pile. Comparing the grout pumped with the theoretical pile volume shows where the ground took extra, and the engineer reviews it.

Who decides how a foundation is built in this ground?

The geotechnical engineer and the structural engineer of record, based on the site investigation. The drilling contractor follows the plans and specifications.

Get a quote 305.910.7737

Certified General Contractor · CGC1539001

Deep foundations, drilled.

Auger holes, drilled shafts, auger cast piles and helical piles for contractors and builders. Based in Miami, licensed statewide in Florida.

Get a quote Call 305.910.7737

Free quote · Reply within 24 hours · Licensed statewide (CGC1539001)

5 years in business Insured and certified

Auger holes
Drilled shafts
Auger cast piles
Helical piles

Florida contractor license

CGC1539001

Current, ActiveStatewide (CGC)Exp. 08/31/2028

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Certified General Contractor · Listed on the Procore network

Based in Miami, FL

@mtrdrillinginc

Services

Four ways
into the ground.

Every job starts with the plans and the soil report. We drill what the engineer designed.

Auger holes

Open holes drilled with an auger to the diameter and depth on your plans, with the spoil brought up and out of the hole.

Drilled shafts

A larger-diameter bored hole. The steel cage is set, then concrete is placed to finish the shaft.

Auger cast piles

Grout is pumped through the hollow auger as it comes back up, so the pile forms on the way out. Then the steel goes in.

Helical piles

Steel shafts with helix plates are turned into the ground like a screw, ready to load.

Not sure which one your plans call for? Send them over.

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Process · auger cast pile

How a pile gets made.

Drilled shafts go the other way round: the cage is set first, then the concrete is placed.

Ready to drill?

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Work · real clips and photos from @mtrdrillinginc

On the ground.

01 / 15

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Working with MTR

Plans in.
Piles in.

01
Send your plans
Foundation plans and the geotech report, or just call and tell us about the job.
02
We bid it
We go through the pile schedule and site access and send you a price.
03
We mobilize
Rig and crew roll in, scheduled around your job.
04
Piles in, site left clean
Piles drilled to plan, spoil handled, site left ready for the next trade.

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Field notes

Deep foundations, drilled.