Go Vertical with Confidence®

Helical Mini-piles

& Screw Pipe Piles

Slide 1

Folsom Dam 42" Water Main Bypass in Folsom, CA. HMP - 15' deep to restrain water hammer on the emergency repair of 42" water main for City of Folsom and Folsom prison water supply.

Slide 2

Cavallo Point at Fort Baker in Golden Gate National Park, CA. HMP – 15' to 20' deep to provide seismic retrofit of historic Army post barracks for the newly established Cavallo Point Resort.

Slide 3

American River College parking structure in Sacramento, CA. HMP – 20' deep to provide uplift resistance at shearwalls for seismic overturning forces at new 5 story parking structure.

Slide 4

Railway Express Annex Buildings at Railyards in Sacramento, CA. HMP – 60' to 75' deep to provide seismic retrofit foundation support in 1925 historic railway terminal and post office buildings.

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Overview

Helical mini-pile (HMP) system is a high strength, manufactured steel, component pile with helix plates that are screwed into the ground to develop bearing and tension resistance for the support of light, medium, and heavy foundation loads. The HMP offers a well-defined, component steel pile with reliable support of foundation loads in soft soil. HMP construction produces low noise and no vibrations with virtually no spoil. An HMP is used in the same way as a pin-pile or micro-pile to support a structure load on soft and weak soil at a deeper more competent soil. The HMP obtains capacity at a deeper soil layer in bearing on the helix screw plates. HMP are sometimes used for temporary bracing of historic building walls or new construction tilt panels. The HMP can be installed with low headroom equipment, in tight access areas, and in new construction for foundation bearing and uplift forces. HMP are a versatile, cost effective, foundation pile for supporting foundations, bracing, and retrofit repair projects.

HMP Applications

HMP is commonly applied to new foundations seismic tension anchors, seismic retrofit, foundation underpinning, and wall tiebacks. The ideal applications for HMP occur at:

  1. Tight access areas for bracing and anchors.
  2. Seismic retrofit of existing buildings.
  3. Sensitive project sites near critical structures.
  4. Foundation upgrade and retrofit in contaminated soil.
  5. Groundwater protection regions.

HMP 4-Step Construction Process

Slide 1

STEP 1

Start HMP lead section. Drill into ground at up to 15 RPM.

Slide 2

STEP 2

Add extensions with additional helix or plain for added depth.

Slide 3

Step 3

Cut-off and install HMP top plate or top connection brackets.

Slide 4

Step 4

Finished HMP in a pile cap.

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Testimonial

Testimonial Image

Baker Beach Rehabilitation Project

San Francisco, CA

“Through it all, the Farrell crew were very professional in working with full time onsite inspectors, Presidio Trust Representatives and unknown conditions underground. The entire job went smoothly and finished two days ahead of schedule.”

Deanna Bohler

Project Manager
Tricorp Hearn Construction

Technical Details

Helical mini-pile system (HMP) offers fast, tight access, foundation support with nearly instant force resistance after installation. Each HMP consists of a lead section and one or more extension sections that are screwed into the ground by application of crowd and torsion. The HMP lead looks like a screw with single to multiple 6” to 14” (152 to 356mm) diameter helices. Each helix is formed to a clockwise downward spiral with all radial sections normal to the shaft's central axis ±3° and with a 3” (76mm) nominal pitch. HMP capacity is initially monitored by the installation torque when installed into soil. The torque resistance is a function of the soil type and size of helix components. HMP extension sections are added as the pier is further advanced into the ground. Once the design depth and installation torques are reached the HMP is cut off and a load bearing plate or new construction bracket is attached.

The HMP and bracket are used to support new foundations, upgrade old foundations, arrest settlement of foundations, and help lift a foundation (as the structure will allow) to adjust the level of building walls. Full-scale load tests are performed on most HMP projects to confirm design capacity and torque relationship to HMP bearing and uplift capacity.

Farrell uses excavators and compact track loaders that are equipped with a drill to install HMP. HMP are commonly installed to depths of 15 to 75 feet (4 to 23 m). The rig slowly screws the HMP into the ground at 15 rpm or less. The installation torque is monitored to determine the HMP capacity and to preserve HMP components. Depending on HMP components, installation torque can vary from 5,000 up to 50,000 ft-lbs (6.8 to 67.8 kN-m).

Helical Mini-pile HMP is a fast, versatile, shallow and deep foundation pile that supports your project to Go Vertical with Confidence®!

Helical Mini-piles

Geologic Hazard Application

Soft/Loose Soil

Contaminated Soil

Slope Stability

Depth Limit

100 ft (27 m)

Compatible Soils

  • Sand (SP, SM, SC)
  • Silt (ML, MH)
  • Clay (CL, CH)
  • Contaminated Soil
  • Undocumented Fill

Bearing Capacity Range

20 kips (89 kN) to 200 kips (890 kN)

Key Advantages

  • Small equipment for tight access
  • Ideal for repair/retrofit
  • Minimal site impact
  • No spoils
  • No vibrations

Key Considerations

  • High material cost
  • Steel below water
  • Weld splice for SPP

Comparable To

  • Micro-piles
  • Soil-nails
  • Concrete piers
  • Driven piles

Farrell Design-Build Inc.  |   Sacramento  530.621.4867   |   Irvine  949.428.9596

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