Foundation Underpinning San Francisco

Foundation Underpinning San Francisco Project

Helical piles installation for foundation underpinning San Francisco project

EagleLIFT provided the Fair Oaks West Apartments building with a helical piles for the foundation underpinning San Francisco project. This rennovation project was designed to rehabilitate and increase the load bearing capacity of the building.

Foundation Underpinning San Francisco

Project Summary

Client:   Fair Oaks West Apartments
Location:   San Francisco, CA
Project Summary: Building Foundation Underpinning San Francisco for upgrading an older building

When the decision was made to upgrade and expand the old structure, the structural engineer determined that underpinning the entire building was required in order to provide the necessary structural support before excavating could begin. Also, additional load bearing capacity was required to support the planned addition.

As with all new construction in San Francisco, seismic retrofitting is also a requirement.

Foundation Underpinning San Francisco Design

Before excavation could begin, EagleLIFT crews installed (61) 1.75” RCS helical piles with 8”,10”12” bearing plates to depths ranging from 20 to 60 feet. (55) of the helical piles were installed on the outside perimeter and (6) piles were installed on the interior. The ultimate load requirement for the piles was 83 kips, and the working load was 55 kips.

The helical pile installation project was successfully completed in 20 working days for this foundation underpinning san francisco project.

An interesting bit of anecdotal information – the helical piles were all installed just a couple of days prior to the Napa seismic event. The structure was examined closely, and the engineer determined there was no sign of movement or a change of any kind.

Our Foundation Underpinning San Francisco Projects

Apartment Building Foundation Repair – Sunnyvale, CA

Fair Oaks West 6

Project Challenges

Client:   GE Construction
Location:   Sunnyvale, CA
Project Summary: Apartment foundation repair due to Minor settlement of partially submerged parking garages built in 1970s

The Fair Oak West Apartments are located within the Santa Clara Valley, which is a broad alluvial plane between the Santa Cruz Mountains to the southwest and west, and the Diablo Range to the northeast.  The San Andreas Fault system, including the Monte Vista-Shannon Fault, exists within the Santa Cruz Mountains and the Hayward and Calaveras Fault systems exist within the Diablo Range.

The property owners decided to have seismic upgrades added to all sixteen structures in the complex, and helical piles were selected as the best choice for the upgrades with both vertical and battered piles being included in the upgrade design. Each apartment building was constructed over a partial subterranean parking level and consist of three levels of wood-framed structures.  Some relatively minor settlement had occurred in three of the buildings since they were originally constructed in the 1970’s.

Soil borings were conducted in several locations across the site, and boring depths ranged from 6.5 to 40 feet.  Variable amounts of sand and medium dense clayey sand was found along with some areas of silt and gravel.

Solutions and Results

All piles were installed inside the garage level, and the maximum head clearance was 6.6 feet, which necessitated the use of small footprint installation equipment and shorter helical pile section lengths.

Fourteen of the buildings had (4) bays each, and (48) piles were installed in each of those buildings.  Two of the buildings had (2) bays each, and (24) piles were installed in each of those buildings.  Each bay had (8) vertical piles installed along with (4) battered piles.

The helical piles manufactured by MacLean Power Systems – Civil Products Group were all 1.75” Round Corner Square Bar.  The leads used for the vertical piles had 8”,10”,12” helix bearing plates, and the required load was (40) kips.  The leads used for the battered piles had two configurations – 10”,12”,14” and 14”,14”, and the required load was (70) kips.  One tension load test on a battered pile was required and completed successfully.  New construction pile caps were connected to each pile.

EagleLIFT crews completed work for each building in one week, and the entire project was successfully completed in sixteen weeks.

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