Geotextiles

Acceptance

    1. Check geotextile for proper identification and packaging including:
      • Identification label.
    2. Review the Certificate of Compliance and manufacturers data for geotextiles properties. Review Specification 3733 to ascertain whether the product meet specifications.  Check Geotextile small quantity acceptance list (located on the Grading and Base Website to see if product meets the required specifications.  Contact Grading and Base if you have questions.
    3. Verify that the geotextile is wrapped in UV protective plastic (usually black).  Do not allow unprotected geotextile to be left exposed to the elements for more than 7 days.
    4. Visually inspect the geotextile for uniformity in thickness, texture, and appearance.
    5. See the Schedule of Materials Control for testing rates.
    6. For geotextiles and geogrids used for Modular Block Walls (MBW) or Reinforced Soil Slopes (RSS), see approved products list on the Foundations Unit website.
    7. Reject the product if any of the above criteria is not met.

Sampling and testing

    1. Per specification, the geotextile must be available for testing at least 21 days prior to use.
    2. Take samples from stock material in warehouse or from the project.  Don’t take more than one sample from an individual roll.
    3. Take samples at rates given in MnDOT’s Schedule of Materials Control.
      • For roll products, cut 3-foot wide strip across the width of the roll, do not sample first full turn (3 feet) of rolled geotextile since it me have degraded in storage. For pipe wrap, take samples at least 3 meters (10 feet) long.
      • When glued or sewn seams are used, a seam sample should be glued/stitched at least 10 feet long and glued/sewn with same or similar machine, and seam/stitch type, as used during construction. Include at least 3 feet of geotextile on each side of seam, i.e., entire sample size should be 10 feet x 6 feet.
      • For sample quantities of 1,000 lin. Feet for pipe wrap or 500 sq. yds. for roll products judged non-critical by the Project Engineer, the inspector has the option of approval without testing.
      • Small quantities may be approved on Form 2403, provided that:
        • A current Certificate of Compliance has been received and the minimum values listed equal or exceeded the specification requirements, and
        • The geotextile product is properly identified to match the Certificate, either on the roll wrapping or inside the roll core.
    4. Submit a pink sample ID card with the geotextile sample. Include:
      • Specification Number, type, and planned use (e.g., 3733 Type 4 for use under riprap).
      • For Type 6 applications, send pages of special provisions that list required properties. (Type 6 requirements are job specific).
      • For MBW and RSS applications, send shop drawings that reference geotextile/geogrid to be used (product name and/or required properties). Central Materials Laboratory (Maplewood) needs this information to complete material testing.
      • Name and phone number of project personnel to contact if questions arise.
      • Manufacturer and model/style (e.g., Amoco 2002)
    5. Include the Certificate of Compliance (see 1.b. above) for the sample you are submitting. Central Materials Laboratory (Maplewood) reserves the right to not test samples that are submitted without a valid Certificate of Compliance that has MARV values that meet all required specifications.

Gluing, Sewing, and Overlaps

    1. Ensure that:
      • Seams are sewn only with a machine using two spools of thread (Fed. 401 stitch)
      • Glued seams are only allowed on types 1-5 geotextiles and must be overlapped a minimum of 6” with glue applied to both sides.
      • Thread tensile strength is (typically) a minimum of 25 lbs. The thread size labeled on the spool will most often be the commercial size. In general, a minimum thread size of 207 should be used.
      • 4 to 7 stitches per inch are used with rows 1 centimeter apart (approximately one-half inch).
      • All seams are pointing upward for inspection purposes.
      • If sewn seams have not been approved by testing prior to installation, minimum seams are either two rows of sewing with a flat seam, or one row of sewing with a J-seam. Inform the contractor that placement will be considered as “Unauthorized Work” until testing is completed.
      • Ensure overlaps are a minimum of 36 inches.  Contact the Grading and Base unit if shorter overlaps are requested.

References: Specifications 2108 and 3733. MnDOT Sampling and Testing Program: Schedule of Material Control. Grading and Base Inspector Training Manual, Text from class presented by Lake Superior College and MnDOT.