Which Pile is right for the Job?

At Foundation Piledriving, we have a unique perspective on specialty piles. Specialty piles are generally considered "problem solver" deep foundation systems, and Tubex, Fundex, and Vibrex Piles have unique advantages in certain site conditions. Because we drive all type of conventional piles, we can easily compare the costs and advantages of using alternate methods.

Whether your project is in the design development stage or is already fully designed, our engineers and consultants can work with you to select the appropriate pile for your project. We only need site conditions, the column load and pile capacity required, the geotechnical investigation and a foundation plan to determine the correct pile for the project. We work to understand your project’s particular constraints to find the right system for the job.

Many project are faced with extensive construction constraints. In urban environments, vibration or noise may be an issue. Piledriving hours may be strictly limited. Construction is often planned adjacent to sensitive unreinforced masonry buildings, high tech equipment buildings, hospitals, or entertainment studios, where vibration is an issue. The site may be low overhead. The site may be found to be contaminated, making offhaul and spoil disposal costly. When you factor in the indirect cost of these outside factors, a specialty pile often proves to be the most economical solution on a total project cost basis.

How Do I Incorporate Specialty Pile Design?

On nearly half of our Tubex and Fundex pile work, the engineering and design has been already completed for some type of conventional driven pile or drilled shaft system. Once preconstruction begins, latent problems to the planned foundation may arise: city noise ordinances may strictly limit piledriving hours; a contaminated plume is discovered, creating excess offhaul and spoil disposal costs; neighboring property owners have vibration and disturbance concerns.

With a geotechnical report and foundation plan, we can often work within the planned pile cap layout and minimize or completely avoid changes to structure. Using L-PILE and GROUP analysis programs, we can model the lateral capacity and deflection of the specialty pile to match that afforded by the planned pile or pier system, thereby avoiding reanalysis of the structure. Our engineers routinely interact with the engineer-of -record to ensure a quick and effective redesign.

When the engineer knows upfront that problems or constraints will occur on the project, we can work with the geotechnical and structural engineers starting in the initial design development. From providing initial budgetary analysis through final plan check, we work with the project team to make sure the pile’s capacity-versus-cost is optimized. Our consultants offer complete design, or design assistance, depending on the requirements of the project team.

We have combined the engineer’s foundation designs with the contractor’s shoring requirements to reorient pile caps, for instance, so that shoring rakers may be founded on the pile, and the same pile is later used for the final building foundation once the shoring is removed. Since we are contractors, we recognize the efforts that go into bringing a project in under the owner’s budget.

Public Work

Public work often presents slightly different design-bid build criteria. Often, bidding must be "plans-and-specs," so the use of specialty piles must be accommodated by the engineer. The stiffness and capacity of the foundation must be coordinated with the superstructure.

On several large projects, Tubex piles have been sole-sourced so that the capacity of the pile can be optimized. To ensure the agency that pricing would not change, we provide a budget price for the project, and then work with the design team to develop pile design information required for the engineer's use and incorporation into the structure. Documents such as a Memorandum of Understanding are used, assuring the agency the price will hold until bidding some time into the future, and that all bidding general contractors will be quoted and given comparable pricing, to avoid impropriate ties in bidding.

Other projects have approached the foundation with two alternate foundation designs, using a smaller quantity of Tubex piles against a larger quantity of conventional piles.

Download Tubex spec
Download Fundex Spec

TUBEX PILES

Our most commonly installed specialty pile is known as the Tubex piles. Tubex piles are steel and concrete pipe composite piles that are screwed into the ground under very high torque and down-pressure. As the piles are installed, a high pressure grouting system is used to pump grout through the pile tip to create a soil-cement grouted zone around the outside of the pipe. Tubex piles are true soil displacement piles. Unlike conventional drilling methods Tubex piles do not produce drill spoil, which creates offhaul costs, and reduces skin friction capacity. Tubex are soil displacement, and the grouting actually increases the pile’s effective diameter. Tubex piles are ideal for contaminated sites to avoid spoils, in low overhead conditions, in restricted site conditions, and on sites where noise and vibration aren’t tolerated.

Fundex Piles

Fundex piles are true cast-in-place soil displacement concrete piles. Sometime referred to as Full Section Soil Displacement concrete piles, Fundex piles differ from augercast piles in that structural concrete and full length reinforcing of any configuration are used to construct the pile. A high torque Fundex drill table forces a mandrel into the ground to the bearing layer. A sacrificial boring tip fitted to the mandrel base prevents soil and water from entering the mandrel. Upon reaching the required depth, a reinforcing cage is placed up to full length of the pile, and structural 1" aggregate concrete—not grout-- is placed in the pile. The mandrel is then extracted leaving the tip, cage and concrete in place. There is no possibility of soil intrusion into the structural concrete, and the cage is fully inspectable for placement and code-required concrete coverage prior to placing the concrete. Installation produces no vibration, no spoils, and no piledriving noise.

Vibrex Piles

While the pile is similar in end result to Fundex piles, with the Vibrex pile, the mandrel is driven conventionally into the ground by an impact hammer. Upon reaching tip elevation and sufficient blow count, the cage and concrete are placed, and the mandrel is then extracted by center-hole vibrator, which simultaneously vibrates the concrete and extracts the mandrel, leaving a driven, cast in place pile in place. The pile is suitable for site on which very erratic bearing layers exist or on sites too restrictive to get precast piles onsite.

Soil Improvement Techniques

Stone Columns

Using the Vibrex method, Fundex piling equipment is used to drive stone columns in grid patterns to both densify and dewater sites using the soil displacement "pipe pile method" of constructing stone columns. Stone columns of up to 70 ft deep can readily be performed, and deeper columns can also be constructed.

Dynamic Compaction

The Fundex PLT (Pile load tester) can be reconfigured with a 4’ diameter striker plate to perform shallow dynamic compaction to influence soil depths of up to about 12’. Ideal for the recompaction of service station tank abandonment sites where loose sands have been placed, the method avoids any handling of onsite soils, while compacting the soil sufficiently for spread footing construction. The rig requires minimal setup time and several hundred square feet of area can be dynamically compacted in a single day. We work with the geotechnical engineer on the grid pattern and compactive effort to ensure the bearing capacity requirements of your project are met.

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