Secant Piles

Michigan State University -FRIB

City: East Lansing

State: Michigan

Owner: Michigan State University

General Contractor: Barton Malow

Schnabel provided design build services to construct an excavation support system that was up to 57 feet deep for the new Facility for Rare Isotope Beams on the campus of Michigan State University in Lansing Michigan. Schnabel used a combination of secant piles and soldier piles with timber lagging.

The secant piles were used to cut off the ground water and served as a rigid system to allow excavation adjacent to an existing facility being used for intricate cyclotron experiments that could not withstand any vibration or movements of the facility while construction was in progress. Soldier piles and lagging were installed to support the excavation that was not adjacent to structures. Lateral support for both systems was provided by tiebacks.

Rondout West Branch Bypass Tunnel Shaft
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Rondout West Branch Bypass Tunnel Shaft

City: Wappinger Falls

State: New York

Owner: New York City of Environmental Protection

General Contractor: Schiavone Construction Co, LLC

One of the main sources of water for New York City are reservoirs in the Catskill Region of upstate New York. This water flows to New York City through a system of tunnels. One of these tunnels that runs under the Hudson River has begun to leak as a result of it’s age. A new tunnel was proposed to allow the existing leaky tunnel to be bypassed. To construct the bypass tunnel, shafts were constructed on both sides of the Hudson to launch and receive the tunnel equipment. Schnabel constructed the secant piles for the shaft on the east bank of the Hudson to support the earth above the rock, and prevent water infiltration.

A series of overlapping, reinforced secant piles were installed in a self-supporting circular ring pattern to allow excavation through the overburden soils and upper portion of the bedrock. The secant piles were installed to a depth of around 87 feet through fill, dense sands and gravel, and toed into 15’ to 20’ of shale bedrock. A Sonic Caliper, as well as Schnabel’s designed laser device, were used to confirm the verticality of each shaft.

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Brigham Green Patient Parking Garage

City: Boston

State: Massachusetts

Owner: Partners Health Care/Brigham & Womens Hospital

General Contractor: Walsh Brothers

Secant piles were used as a permanent water cutoff wall and foundation wall for the proposed underground parking garage at the Brigham Green Hospital in Boston, Massachusetts. Temporary tiebacks were installed for lateral support during construction. Once the garage slabs were placed the temporary tiebacks were detensioned and the slabs served as the permanent lateral support.

Secant piles were used as a permanent water cutoff wall and foundation wall for the proposed underground parking garage at the Brigham Green Hospital in Boston, Massachusetts. Temporary tiebacks were installed for lateral support during construction. Once the garage slabs were placed the temporary tiebacks were detensioned and the slabs served as the permanent lateral support.

Excavation Support

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Reno ReTRAC

City: Reno

State: Nevada

Owner: City of Reno

General Contractor: Granite Construction

Traffic in downtown Reno had become increasingly congested due to numerous at grade railroad crossings. To reduce this congestion, the City of Reno contracted with Granite Construction to put a portion of the railroad in a depressed trench so that rail traffic could pass through the city unimpeded. The depressed portion was around 2.2 miles long, 54-foot wide and up to 35 feet deep.

Granite selected Schnabel to design and build the complex system of excavation support and underpinning to complete this project. Schnabel selected soil nailing to provide excavation support where there were no structures and a combination of hand-dug piers and micropiles to support the adjacent structures. This innovative project was awarded the 2006 Outstanding project award by the Deep Foundations Institute (DFI).

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I-495 Hot Lanes

City: Washington, D.C. (suburbs)

State: Virginia

Owner: Virginia Department of Transportation

General Contractor: Flour Lane Construction

Schnabel was hired to design and install permanent walls along a fourteen mile stretch of the I-495 as part of a public/private partnership (P3) to widen the highway and reduce congestion. Schnabel constructed seven tieback walls, twenty two cantilever walls, and one secant pile wall. Seventeen of the walls also had sound barriers above the retaining walls.

The walls were constructed by installing galvanized piles into pre-drilled holes and back-filling the holes with concrete. Timber lagging was then placed between the piles to retain the earth as the walls were excavated. Precast panels were placed in front of the lagging as a permanent facing. Placement of the precast panels was done by both Schnabel and other Contractors.

Soil Mixing

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Boston Museum of Fine Arts

City: Boston

State: Massachusetts

Owner: Museum of Fine Artso

General Contractor: John Moriaty & Associatesn

To increase exhibit and storage space, an addition was constructed at the Museum of Fine Arts located on Boylston Street in Boston, Massachusetts. The addition was located along the east side of the existing museum within an existing courtyard in the area of a recently demolished structure. The basement for the new addition extended up to 30 feet below the floor slabs of the adjacent buildings which were supported on a variety of foundations including; shallow spread footing in alluvial sand deposits, low capacity piles bearing in the alluvial sands and clay below, and caissons bearing on the alluvial sands and desiccated Boston Blue Clay crust. Groundwater was less 5 foot below existing slab grade.

To provide excavation support and limit the lowering the groundwater table outside the excavation, Schnabel installed a 66,000 square foot cement deep soil mixed (CDSM). The CDSM wall was selected to control deep seated ground movements, limit movements of adjacent structures, and inhibit groundwater flow into the excavation. Braces and a continuous wale were used to support the CDSM wall where it was located adjacent to structures. Tiebacks were used where there were no structures.

Other geotechnical construction at the site included:
Jet grouting (JG) was used to improve the ground and provide an impervious subgrade layer at the west end of the addition. Concrete pier underpinning was used to support an existing structure on the west end of the site. A secant pile wall using alternating drilled concrete piles and JG columns was used for earth support and a barrier to groundwater for the installation of a storage tank at the south end of the site.

Inclinometers, total station surveying, vibrating wire strain gauges and tieback load cells were used to monitor performance of the excavation support system. Movement of the the shoring were all kept well below tolerable limits.

Granite selected Schnabel to design and build the complex system of excavation support and underpinning to complete this project. Schnabel selected soil nailing to provide excavation support where there were no structures and a combination of hand-dug piers and micropiles to support the adjacent structures. This innovative project was awarded the 2006 Outstanding project award by the Deep Foundations Institute (DFI).

Micropiles

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Museum of Science & Industry-U505 Sub Relo

City: Chicago

State: Illinois

Owner: Museum of Science and Industry

General Contractor: W.E. O’Neil Construction Company

The Museum of Science and Industry U-505 Submarine Relocation project required the construction of an underground reinforced concrete vault shoring (37 ft deep) and underpinning of the existing museum footings for construction of a new elevator and stairwell area.

Schnabel designed and installed the shoring and 21 micropiles approximately 65 ft long to support the existing structure. The micropiles consisted of a 9-5/8” diameter by 0.545-inch thick permanent casing extending into the stiff clay with a #20 bar extending the full length into the Chicago hardpan. To minimize interference with future building walls, the micropiles were drilled at a slight batter underneath the existing footing. Reinforced concrete micropile caps were placed under the existing footings to permanently support the building load.

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American Trucking Association

City: Washington

State: District of Columbia

Owner: American Trucking Associationn

General Contractor: Forrester Construction

The renovation of historical protected structures usually presents the architect with an array of unusual problems. Complicate a project with height limitations, footprint limitations and the need for additional parking, and the solution will usually require that the site be fully developed below grade. Add to this the need to undermine and support buildings constructed in 1893, 1910 and 1972 and you now have an outline of challenges RTKL faced in adding 25,000 sf of office and parking space to the American Trucking Association building in Washington, DC.

Forrester Construction Company selected Schnabel to design and build a system to extend the foundations of the existing structures to a deeper elevation, prior to excavating the site below the existing buildings and from property line to property line. The approach was a design that focused primarily on traditional pit underpinning to pick up the axial loads from the shear walls that were supposed to be supporting the structures. As the architect supplied plan revisions for the new construction, it became clear that the original concept would impede the construction of new shear walls that would provide the permanent foundations for the renovated buildings.

Schnabel designed a micropile support system that penetrated the footings and transferred the loads to the columns and walls above the footings. This enabled the construction of future foundation structure under the existing footers.

To minimize movement of the structures and to control risk, Schnabel designed a sequence of construction that would allow the new shear walls to sequentially pick up loads, as each building was undermined. The site was continuously monitored with real-time readings that would alert movement in minutes of any settlement. The system is so sensitive that Schnabel would get alerts when an excavator’s bucket would scrape a structure’s foundation. Even with this level of sensitivity and precision, measurements of the movements to date have been within the system’s accuracy; no measurable movement.

Underpinning

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IVY Tower

City: Minneapolis

State: Minnesota

Owner: Ivy Tower Minneapolis, LLC

General Contractor: BOR-SON Construction, Inc.

The historic Ivy Tower is the narrowest tower in Minneapolis, MN at just 50 ft x 55 ft in plan and 140 ft tall. Construction on the Hotel Ivy + Residence, which wraps around and incorporates the historic Ivy Tower, required a unique combination of earth retention and underpinning systems to allow a 51 ft deep excavation for five levels of underground parking directly adjacent to the historic Ivy Tower. The Ivy Tower was closely monitored for building movements throughout construction with satisfactory results.

Soil Nailing

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Glendale Arena

City: Glendale

State: Arizona

Owner: Arena Development, LLC

General Contractor: Perini Building Company

The Glendale Hockey Arena had one of the tightest schedules for a sports stadium constructed in the United States, and critical to the fast track schedule was the installation of the design-build permanent soil nail wall. Using permanent soil nailing around the entire perimeter of the site to resist earth loads simplified the stadium’s design. This allowed for larger open spans within the arena. Schnabel designed and built the permanent wall, with over 73,000 square feet of shotcrete wall face and 60,000 lineal feet of soil nails. The soil nailing was completed in just eight weeks.

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Centerpoint Condominiums

City: Tempe

State: Arizona

Owner: Avenue Communities, LLC

General Contractor: Avenue Communities, LLC

To provide additional parking in an already congested location, Centerpoint Condominiums, a high-end condo project in busy downtown Tempe, AZ, required an excavation exceeding 50 feet in depth. Schnabel installed a mixture of battered and vertical temporary soil nail walls, as well as tieback soldier pile walls in order to protect existing structures and roads and utilities around the site perimeter.

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