Completed side-hill retaining wall for the SR 264 Second Mesa project in Arizona. Photo by Bharat Khandel, ADOT by way of NCS Consultants, LLC

Side Hill Retaining Walls – Part 2

Completed side-hill retaining wall for the SR 264 Second Mesa project in Arizona. Photo by Bharat Khandel, ADOT by way of NCS Consultants, LLCIn this part 2 of 2, various types of retaining walls are examined as possible alternatives in a side-hill retaining wall situation. These include conventional wall types such as CIP walls, MSE walls, gravity walls and soldier pile walls and some less conventional approaches such as lighweight concrete fill, hybrid soil-nail and geofoam wall systems, ground improvement and micropile walls.

Part 1 of this Side Hill Retaining Wall article covered the definition, significance, problems and failure modes, investigation techniques, analysis, and construction considerations of side hill walls. A PDF version is now available for download as well. Click through for the article and the download link!


Scrap Tires
Available Resources

Green Retaining Wall Technology

According to information provided by Productive Recycling, there are approximately 300 million used car and truck tires are generated in the U.S. each year. More than 90% end up in landfills. Productive Recycling has a […]

Cover of FHWA NHI Mechanically Stabilized Earth Walls and Reinforced Slopes Design and Construction Guidelines course manual.
Available Resources

FHWA NHI 2009 MSE Wall Manual

Cover of FHWA NHI Mechanically Stabilized Earth Walls and Reinforced Slopes Design and Construction Guidelines course manual.[Disclosure] NCS Consultants is the employer (day job) of Randy Post, the owner of this site. [/Disclosure]

Geotechnical engineers who encounter MSE retaining walls or Mechanically Stabilzed Earth Walls are undoubtedly familiar with the FHWA NHI manual on “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes”. This manual, along with the NCMA manual that is used for non-transportation projects, is virtually the bible for MSE wall design. In late summer/early fall of 2009, a revised version of this manual will hit the streets. Read on for more details.



World Trade Center Slurry Wall to Become Part of Museum

The only portions of the World Trade Center towers that survived the attack on 9/11 were the basement slurry walls, part of the original shoring and foundation system. The National September 11 Memorial and Museum at the World Trade Center that is currently under construction will preserve a portion of that wall making it the largest exhibit the museum will offer. The wall section displayed will be 62-ft by 64-ft.

The existing slurry walls are being incorporated into the foundation system of the new facility but not without some improvements. The are adding some kind of foundations improvements to stabilize the toe of the walls, the New York Times article calls them caissons, but I don’t know if its a tangent or secant wall or something else. They are also lining them with additional concrete and reinforcement in front of the walls along with additional tiebacks to stabilize them. In the portion of the wall that will be displayed, a counterfort wall will be constructed behind it and new tiebacks will be installed on the front. Work for the counterfort wall will be done by hand in order to avoid the existing tieback cables. All of the existing tiebacks will be left intact. Check out the NY Times article for a great graphic showing the system. (Illustration by New York Times)


Project Related

North America’s Tallest MSE Retaining Wall

[Update Jan 28, 2008] It appears as if the Port of Seattle is in some hot water for some alleged shady dealings with one of the contractors on the project.  More at Seattle Times. [/Update]

Erosion Control magazine has an interesting article on MSE Walls. I think the tie-in of MSE Walls with erosion control is a little questionable (they did mention wall drainage a few times), but the article highlights several interesting projects, particularly the Seattle-Tacoma Airport or Sea-Tac Third Runway Project retaining walls. The West wall for that project is the tallest MSE Wall in North America, 130-ft at its highest point. More after the break. (Photo by Sea-Tac Airport)


Geologic Hazards

Devil’s Slide Tunnel Construction Kicks Off

On September 17, CALTRANS and Kiewit Pacific held a "tunnel excavation celebration" to kick off the start of tunnel construction on The Devil’s Slide Tunnels project on California State Route 1 (the Pacific Coast Highway) in San Mateo County between the town of Montara to the south and the city of Pacifica to the north. The project involves the creation of a separated two-lane road, one lane in each direction. This road will pass through twin tunnels, over twin bridges and connect with an existing non-separated two-lane road at each end. The new road will be approximately 6,500 feet long, made up of the roughly 4,000-foot twin tunnels, the 1,500-foot north approach road (which includes the 1000-foot parallel bridges), and the 1,000-foot south approach road. Upon completion, the new road will bypass geologically unstable portions of existing Route 1, sections of roadway subject to lengthy closures, high maintenance costs over the years, and risk of permanent failure. Thanks for the heads up. [Read on for more background, photos, maps, and movies!] (Images by CALTRANS)