Company:
Irvine Company Office Properties (The Irvine Company)
Status:
Awarded
Awarded:
Structural Engineering Project of the Year
Additional Files
400 SCD Soil Nail Wall Site Plan
Additional Information

The attached pdf document details the design features of the soil nail wall.

400 Spectrum Center Drive Soil Nail Wall

Project Location:

Irvine Spectrum, Irvine, CA

Project Description:

The Irvine Company’s Office Properties group, in need of creating a developable area next to two sloped street abutments along Alton Parkway and Enterprise Drive for a 6-Level Parking Structure adjacent to its planned 21-Story Class “A” office tower located at 400 Spectrum Center Drive in the Irvine Spectrum Center, challenged its design team to come up with a solution to support the up to 35 foot-high adjacent street descending slopes.  The limited encroachment on the project site inside the property limits further restricted the ability to “tie-back” the sides of the excavated slopes.  Tight property line limits along with restrictive utility right-of-way limits along Alton Parkway presented additional challenges for the structural design of the soil nail lengths and spacing.  As geotechnical engineer-of-record to The Irvine Company (TIC) for the project, GMU Geotechnical, Inc. (GMU) was able to add structural engineering services to our scope in order to assist TIC to find an innovative and cost-effective geo-structural solution to not only address the site shoring but also serve as the final walls of the parking structure by designing the City of Irvine’s first soil nail wall.  This soil nail wall, with top-down construction, consists of soil reinforcement elements, a temporary facing, and a final structural wall.  The soil nail wall is 671 feet long by as high as 36½ feet, with 3 to 7 vertical rows of a total of 844 nails.  All structural elements of the soil nail wall were thoroughly tested including the nails to support a minimum of 1.5 times of the design loads without excessive creep per FHWA requirements.

Project Justification:

1-  PROJECT BENEFITS
The benefits derived from the soil nail wall were made possible due to innovative engineering design including:

• Permanent soil nails instead of temporary tie-backs
• Efficient reinforced shotcrete wall construction instead of expensive two-step shored/tied backs with a conventional cast-in-place concrete wall
• Adjustable soil nail spacing to accommodate extensive landscaping of slopes
• Soil nail elements are tested during construction confirming the design assumptions
• Less rigorous permitting through grading department only – no building department permit was required
• Cost/construction savings

2-  SUSTAINABILITY
Innovative design engineering and construction of the soil nail wall reduced the use of both concrete and steel by eliminating expensive tie-back shoring, lagging, soldier piles, and a permanent conventional cast-in-place concrete wall to support the excavated sides of the parking structure, resulting in a lesser carbon footprint.

3- UNIQUE AND INNOVATIVE WALL SOLUTION
A geo-structural system that was flexible during the design process to accommodate the site restrictions, realize budget savings, and provide a sustainable solution during construction.  The soil nail wall was able to be constructed in phases allowing the other trades, including grading, to work in sequence with the progress of soil nail wall construction. 

4- PROJECT IS A MODEL THAT CAN BE REPLICATED IN IRVINE AND OTHER CITIES FOR ALTERNATE WALL CONSTRUCTION: 
This soil nail wall is scalable to almost any size and produces significant budget savings, sustainability, and flexibility of project site development. The project can serve as a model for other areas.

Special Circumstances:

COLLABORATION BETWEEN SOIL NAIL WALL DESIGNER AND CITY OF IRVINE COMMUNITY DEVELOPMENT DEPARTMENT ALLOWED FOR STREAMLINING A SINGLE INNOVATIVE SHORED WALL SYSTEM:  Geo-structural design of the soil nail wall, with support and review from the project civil engineer and landscape architect, allowed the soil nail wall system to provide a unique opportunity to reduce capital costs by sharing space and similar function to a conventional shoring and tie-back system for a conventional cast-in-place concrete wall, which generated a net benefit, rather than cost.  The City of Irvine community development department/grading division stepped up to review the soil nail wall as a part of the precise grading plan submittal, thus providing time and cost savings during the permitting process by avoiding a building department submittal and review.

Project Attachments:

The attached pdf document details the design features of the soil nail wall.

Award Citation::

As a part of the on-going expansion of the Irvine Spectrum Center, Irvine Company (utilizing GMU’s geotechnical and structural engineering services) was able to construct the 400/450 SCD 21-Story Class “A” office tower with its 6-story, with 2-subterrean level, Parking Structure next to two existing slopes along Alton Parkway and Enterprise Drive by utilizing a cost-effective and an efficient geo-structural solution by GMU designing the first soil nail wall permitted by the City of Irvine.

Suggested Award Summary:

The Irvine Company’s Office Properties group, in need of creating a developable area next to two sloped street abutments along Alton Parkway and Enterprise Drive for a 6-Level Parking Structure adjacent to its planned 21-Story Class “A” office tower located at 400 Spectrum Center Drive in the Irvine Spectrum Center, challenged its design team to come up with a solution to support the up to 35 foot-high adjacent street descending slopes.  The limited encroachment on the project site inside the property limits further restricted the ability to “tie-back” the sides of the excavated slopes.  Tight property line limits along with restrictive utility right-of-way limits along Alton Parkway presented additional challenges for the structural design of the soil nail lengths and spacing.  As geotechnical engineer-of-record to The Irvine Company (TIC) for the project, GMU Geotechnical, Inc. (GMU) was able to add structural engineering services to our scope in order to assist TIC to find an innovative and cost-effective geo-structural solution to not only address the site shoring but also serve as the final walls of the parking structure by designing the City of Irvine’s first soil nail wall.  This soil nail wall, with top-down construction, consists of soil reinforcement elements, a temporary facing, and a final structural wall.  The soil nail wall is 671 feet long by as high as 36½ feet, with 3 to 7 vertical rows of a total of 844 nails.  All structural elements of the soil nail wall were thoroughly tested including the nails to support a minimum of 1.5 times of the design loads without excessive creep per FHWA requirements.

CEC

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