Deep Foundations / Piles
Deep Foundation / Piles Techniques
Ductile Iron Piles
Ductile Iron Piles are a simple, fast and highly effective low-vibration driven pile system utilizing high-strength ductile cast iron. Modular pile sections are connected by a proprietary Plug & Drive system, eliminating the need for welding and splicing while providing a high degree of stiffness. With the use of an excavator fitted with a high frequency hydraulic hammer, piles are installed by driving the pile sections in quick succession leading to fast and easy installation with minimal vibrations. Ductile Iron Piles (DIPs) are installed to transfer foundation loads through compressible soils or fill to more competent soil or bedrock.
DIPs develop moderate to high working capacities through either end-bearing on dense soil or bedrock, or by developing frictional capacity along a grouted bond zone within competent soils. End-bearing DIPs are driven through the unsuitable soils to refusal or achieve the driving criteria or “set” in the underlying dense soil, glacial till or bedrock. Friction DIPs are installed with an oversized conical grout point at the pile base. As the pile is driven, sand-cement grout is pumped through the grouting shank. The grout fills the hollow pile and exits through grout ports within the conical grouting point to fill the annular space created by driving the oversized cap. This process encapsulate the pile in grout and forms the basis for the grouted bond zone within the surrounding competent soil to achieve the design capacity.
Ductile Iron Piles are often a cost-effective and rapid alternative to traditional deep foundations like Drilled Micropiles, augercast piles, driven steel H-piles piles or steel pipe piles. The system excels with foundation support in constrained sites or urban settings where tight access and low vibration requirements influence foundation selection. The system can successfully penetrate challenging soil and fill conditions. LEARN MORE
Helical piles are deep foundation elements that are used to support new foundations or underpin existing foundations. They generate no vibrations and can be installed with only 6 feet of overhead space and in other limited-access situations. The pile shafts are made of galvanized steel and are installed in short sections, each about 5- to 7-feet-long. Each pile consists of a lead helical section with welded screw-like bearing plates; subsequent straight-shaft sections are mechanically-fastened to the lead section as it is advanced into the ground. The piles are installed with a skid-steer or an excavator equipped with a high-power torque head, which is calibrated to directly correlate torque resistance with pile capacity. Helical piles can also be installed with hand-held torque motors for locations that are not accessible with a skid-steer or small excavator.
Helical piles can function as end-bearing or side-friction elements. For an end-bearing pile, the lead section is advanced through the unsuitable soil layers and into an underlying bearing stratum until a predetermined design torque value is achieved. For a side-friction pile, “digger plates” are added between each pile section in order to create annular space around the steel shaft, and the annulus is filled with grout as the pile is advanced into the ground. This process creates a grouted bond with the surrounding soil, resulting in a helical micropile. Similar to a Drilled Micropile, a side friction helical micropile is installed to a predetermined design depth.
Helical piles are ideally suited for foundation support or underpinning requiring low to moderate pile capacity. Alternative foundation options including Ductile Iron Piles or Drilled Micropiles may provide greater design efficiency and cost-savings by affording higher pile working capacity.
Helical piles can also be used as anchors or Tiebacks.
Drilled micropiles (DMPs or mini-piles) are high-capacity, small diameter, drilled deep foundation elements that are used to support new foundations or underpin existing foundations. They generate only minimal vibrations and can be installed with only 8 feet of overhead space and in other limited-access situations. DMPs generally consist of a combination of steel casing, threaded bar, and grout. They derive their geotechnical capacity through side friction between the grout and surrounding soil or bedrock. DMP construction methods vary depending on project-specific conditions, but are generally installed by: 1) advancing the steel casing to a predetermined design depth using rotary-wash or compressed-air drilling methods, 2) filling the casing with grout, 3) inserting a central threaded bar through the grout, and 4) withdrawing the casing to create a bond zone between the grout and surrounding soil or bedrock. Some casing is typically left in the ground permanently to facilitate structural connections, for seismic design considerations, or for other design considerations.
DMPs are particularly useful in limited access situations, adjacent to vibration-sensitive structures, and when penetration through relatively dense and/or obstruction-laden fill is required. In cases where the fill is not particularly dense, but limited access and vibrations are still a concern, Ductile Iron Piles or Helical Piles can often be cost-effective alternatives to DMPs.
Displacement piles are a type of deep foundation element that are used to support new foundations. The piles consist of cast-in-place grout or concrete with a central threaded bar and are constructed with a hollow steel displacement tool. The displacement construction process generates little to no excess spoils and is particularly advantageous on sites with contaminated soils. Displacement piles can function as end-bearing or side-friction elements. They can even be constructed with an expanded base to achieve higher geotechnical capacities, similar to pressure injected footings (PIFs).
STELCOR Drilled-In Displacement Micropiles are high-capacity deep foundation elements that can be rapidly installed with no vibration and no spoils. STELCOR micropiles are installed using hydraulic powered rotary equipment and are spun into the ground while crowd or downward pressure is exerted on the high strength steel core. Grout ports in the steel core provide a mechanism for continuous flow of grout. The reverse flighting creates a continuous unique grout column “interweaved” into the surrounding soil to provide high axial capacities.
STELCOR Drilled-In Displacement Micropiles are the optimal solution when trying to achieve high axial load capacities in extremely poor soils at comparatively shallow depths particularly in limited access and overhead clearance applications. In addition, STELCOR piles can often times offer a lower cost per kip of support compared to other types of piles.