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Publication Number:  FHWA-HRT-12-051    Date:  August 2012
Publication Number: FHWA-HRT-12-051
Date: August 2012


Sample Guide Specifications for Construction of Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS)




2.1.1. Physical Requirements

  1. Furnish-facing elements consisting of split-face CMU should meet ASTM C90-11b requirements, with a minimum required compressive strength of 4,000 psi and a maximum water absorption rate of 5 percent after 24 h.(3)

  2. In areas where repeated freezing and thawing occur, CMU block units shall be tested for freeze-thaw durability in accordance with ASTM C1262-10.(4)

  3. Specimens used for absorption testing shall not subsequently be used for freeze-thaw testing.

  4. CMU blocks shall be furnished within the following tolerances:

    • The height of each individual block shall be within 1/16 inches of the specified dimension.

    • The length and width of each individual block shall be within 1/8 inches of the
      specified dimension.

    • Hollow CMU units shall have a minimum face shell thickness of 1.25 inches and a web thickness of 3/4 inches.

  5. The CMU units shall be randomly sampled and tested in accordance with ASTM C140-12.(5) Contractor QC testing shall be conducted at a qualified agency or AASHTO accredited laboratory as described in section 4.4 of this guide.

  6.  Agency acceptance testing of the CMU blocks will be performed on a lot basis.


Furnish sound, crushed durable particles, fragments of stone gravel free from organic matter or other deleterious material for the abutment, reinforced soil foundations (RSFs), and integrated approach conform to the following:

2.2.1. Abutment Backfill

Backfill material shall meet the following requirements:

2.2.2. RSF Backfill

The backfill for the RSF shall be well-graded material as described in section 2.2.1 of this guide.

2.2.3. Integrated Approach Backfill

Well-graded backfill material shall be furnished as described in section 2.2.1 of this guide for the integrated approach.


  1. Geosynthetics consisting of geogrid or geotextile for the GRS abutment should be furnished. Furnish geotextile for the RSF and integrated approach.

  2. Geosynthetics material may be manufactured from polypropylene, high-density polyethylene, or polyester.

  3. Geosynthetics can be either uniaxial or biaxial. When a uniaxial type is used, higher-strength axis must be placed perpendicular to the wall face.

  4. Geosynthetics composed of a minimum ultimate tensile strength of 4,800 lb/ft according to ASTM D 4595-11 for geotextile or ASTM D 6637-11 for geogrid should be furnished.(10, 11) The design requirements may call for a geosynthetic with higher strength.

  5. Geosynthetic reinforcement strength at 2 percent strain shall be greater than the unfactored required reinforcement strength.

  6. The geosynthetic shall be evaluated in accordance with XXX Department of Transportation standard procedures (refer to section 3.4 of FHWA-HRT-11-026).(1)



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