Geosynthetically Confined Soil® (GCS®) Walls

GCS® Walls

Inside Our Geosynthetically Confined Soil® (GCS®) Walls

A Mechanically Stabilized Earth (MSE) retaining wall is a composite structure consisting of alternating layers of compacted backfill and soil reinforcement tie-back elements fixed to a wall facing. The stability of the wall system is derived from the interaction between the backfill and soil reinforcements, involving friction and tension. The result is a coherent gravity assembly that is flexible and can carry a variety of heavy loads. These engineered structures’ stability can be influenced by required large foundations, properties of the backfill used, and construction quality. On average, 5% of installed MSE walls experience failures.

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A Deeper Look into GCS®

Although the components of MSE and Geosynthetically Confined Soil® (GCS®) are identical (reinforcement, facing, and earth backfill), the similarities end there. The grids used in MSE are designed – and perform as – tie-backs. The load in the MSE system is carried by the reinforcement material, with only negligible composite behavior. In contrast, GCS® using close spacing performs as a unique composite system. The function of the reinforcement material in GCS® is not to carry the load but to confine the granular soil particles so they cannot dilate. If the individual particles are prevented from dilating, they will fail through shear. Shearing bedrock particles is difficult and explains why GCS® pillars require nearly 22,000 lbs/sf to fail. Closely spaced inclusions, 8 to 12-inches, provide significantly better confinement, causing the failure mode to divert to shear through the particles. 8-inch spacing with woven geosynthetics with wide strip tensile capacities of 100 to 400 pounds per foot is a standard solution. Compaction is critical for GCS® particle confinement. Uncompacted backfill will not self-compact with loading; rather, it will fail.

Roadway Solution

In February 2020, GeoStabilization was notified of the slope failure in the shoulder of a road in Madison County, North Carolina. Our Geohazard Experts stabilized the slope and installed a landslide repair system that included a micropile-supported Geosynthetically Confined Soil® Wall, which improved the roadside geometry. The wall also allowed NC DOT to install guardrail on this curved section.

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Self-drilling Soil Nails

When retaining structures adjacent to the existing road platform in Sullivan County, Tennessee failed, GeoStabilization International® provided an engineered solution. Four rows of self-drilling soil nails were installed into the excavated surface and covered with a 6-inch layer of reinforced shotcrete to create a shoring back wall. This wall provided a safe working bench for our equipment and allowed construction of the retaining structure at the stream elevation while preserving the traveled way.

Working from the created bench, our team members then installed self-drilling soil nails vertically to form micropiles and left the nail ends protruding through the soil along a creek. The extended nail ends connect to reinforced shotcrete and micropile-reinforced grade-beam. Our crews then constructed an engineered, Geosynthetically Confined Soil® (GCS®) backfill to build out to the existing retaining wall that is still standing vertical on each side. For additional stabilization of the road platform, soil nails and galvanized plates were installed through fifty-foot sections of the existing retaining walls on each side of the primary failure area.

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Our Solutions

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If you are interested in a no-obligation site visit to determine if our services fit your needs, call us at 855.579.0536 or fill out our contact form.

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    How Can We Help?

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    How Can We Help?

    • Personal Info

    • Contact Info

    • Project Info