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NCS Consultants, LLC Projects - SR 264: Second Mesa GeoFoam Wall
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This project has been constructed and is in service.

A view of the existing slope showing the extreme temperatures encountered at the site. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT.   Installing additional soil-nails. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT.   Completed

SR 264 Project Location MapThe SR264: Second Mesa project was dubbed a "rockfall containment and safety" project by the Arizona Department of Transportation (ADOT). The previously existing rock slopes were hazardous and ditch widths were deemed insufficient, therefore a widening project was undertaken. The prime consultant on the project was Aztec Engineering, Inc.

The initial project assessment and the design effort up to 60% recommended 4 MSE retaining walls to accomodate the roadway widening needed for the increased cut ditch widths. A geotechnical investigation was performed by Western Technologies, Inc. using Crux Subsurface for the difficult access drilling.

Nearly completed geofoam installation. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Project contraints included the steep existing geometry of the slope, the fact that the site in on the Hopi Reservation, requirement of maintenance of traffic on the existing roadway, no new right of way acquisition, and no upslope cuts. The poor foundation conditions and significant shoring required for MSE walls were anticipated to have a large impact on the cost and constructbility of the project.

Soil-nail installation. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. A value analysis was performed, and NCS was asked to help come up with alternative wall/fill schemes under our On-Call contract with ADOT. During the value analysis process, 2 walls were eliminated, and the other two were redesigned by the team to be an innovative hybrid of soil-nail wall and GeoFoam platform combined with pre-cast concrete facing.

Placing the precast concrete fascia panels. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. The concept was to create no net pressure increase at the base of the "wall" while still allowing the widening of the roadway. The soil nail wall is the true "retaining" portion of the system, taking ALL of the lateral forces imposed by the slope. The purpose of using GeoFoam was to ensure that the net pressure imposed on the slope was no greater than the existing configuration to alleviate concerns of poor bearing capacity and potential global (overall) slope instability. This highly unconventional and innovative design required a number of details to be constructed successfully, including a fascia wall footing, a leveling course, a load distribution slab, and protection of the GeoFoam from termites and gasoline.

A series of photos is presented to the right, and below, that provide an overview of the construction of this remarkable project.

  • First known use of Geofoam in Arizona
  • Innovative side-hill "wall" system comprised of Soil-Nail retaining wall and Geofoam with precast concrete facing panels along with various structural elements.
  • 2006 ACEC Grand Award Winning Project
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SR 264 - Second Mesa site plan after the value analysis stage. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of AZTEC Engineering, Inc.

The first bench for the soil-nail wall. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT.

Applying shotcrete to the first bench for the soil-nail wall. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT.

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Photos
Placing the concrete for the load distribution slab on top of the geofoam blocks on the SR 264 project. Photo courtesy of ADOT Holbrook District. Placing the concrete for the load distribution slab on top of the geofoam blocks on the SR 264 project. Photo courtesy of ADOT Holbrook District. Geofoam blocks used in front of a soil-nail stabilized embankment on the SR 264 project. Photo courtesy of ADOT Holbrook District. Geofoam blocks used in front of a soil-nail stabilized embankment on the SR 264 project. Photo courtesy of ADOT Holbrook District. An overview of the SR 264 project site, which uses geofoam blocks in front of a soil-nail stabilized embankment with a facing wall. Photo courtesy of ADOT Holbrook District. Drilling performed by Crux for Western Technologies, Inc. in the location of a proposed MSE retaining wall that was later value engineered to a different system. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Excavating the first bench for the soil-nail wall. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. The first bench for the soil-nail wall. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Nail head with reinforcement. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Nail installation on the first bench. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Anti-termite treatment prior to shotcreting the first soil-nail bench. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. The first soil nail bench. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. A view of the existing slope during the geotechnical investigation phase. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. A view of the existing slope prior to construction. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Preparing the next soil-nail wall bench. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Shotcrete placement. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Forming the fascia wall footing. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Geofoam blocks waiting to be installed. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. The prepared fascia wall footing. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Preparing the leveling course. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Placing the geofoam blocks. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Placing the geofoam blocks. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. The interface between the geofoam and the soil-nail wall. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Load distribution slab and reinforcement that will be used to structurally connect the precast fascia panels. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Reinforcement for the load distribution slab. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Load distribution slab. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Installing additional soil-nails. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Pouring concrete for the load distribution slab. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Pouring concrete for the load distribution slab. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Anti-termite chemical treatment. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Anti-termite chemical treatment. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Gasoline-resistant geo-membrane to protect the polystyrene geofoam. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Placing the precast concrete fascia panels. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Placing the precast concrete fascia panels. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Partial completion of the Placing the precast concrete fascia panels. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. Finishing the road base and preparing for final paving. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of Bharat Kandel, ADOT. SR 264 - Second Mesa site plan during the Pre-Design phase and up to the 60 percent design phase. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Photo courtesy of AZTEC Engineering, Inc. Completed Completed Completed Completed Project location map for the SR 264 - Second Mesa project. The SR 264 - Second Mesa project involved a hybrid soil-nail retaining wall and geofoam installation with precast concrete facing panels in a side-hill highway widening application. Image courtesy of AZTEC Engineering, Inc. NCS was a member of the AZTEC Engineering Team that received the 2006 ACEC Grand Award for the SR 264 Second Mesa Project.
 
 

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