10-81 Section 1056
1056 -1 DESCRIPTION Provide geosynthetics f or subsurface drainage, separation, stabilization, reinforcement, erosion control, filtration and other applications in accordance with the contract. Use geotextiles, geocomposite drains and geocells that are on the NCDOT APL . Products must be current wi th the applicable AASHTO Product Evaluation & Audit Solutions workplan to remain on the NCDOT APL. Prefabricated geocomposite drains include sheet, strip and vertical drains (PVDs), i.e., “wick drains” consisting of a geotextile attached to and/or encapsulating a plastic drainage core. Geocells are comprised of ultrasonically welded polymer strips that when expanded form a 3D honeycomb grid that is typically filled with material to support vegetation. Define geotextiles, geogrids, geocomposite drains and geocells as geosynthetics. If necessary or required, hold geotextiles , geogrids and sheet drains in place with new wire staples, i.e., “sod staples” that meet Subarticle 1060- 8(D) or new anchor pins. Steel anchor pins shall have a diameter of at least 3/ 16 inch , a length of at least 18 inches , a point at one end and a head at the other end that will retain a steel washer with an outside diameter of at least 1.5 inches. 1056 -2 HANDLING AND STORING Load, transport, unload and store geosynthetics so geosynthetics are kept clean and free of damage. Label, ship and store geosynthetics in accordance with Section 7 of AASHTO M 288. Geosynthetics with defects, flaws, deterioration o r damage will be rejected by the Engineer . Do not unwrap geosynthetics until just before installation. D o not leave geosynthetics exposed for more than 7 days before covering except for geotextiles for temporary wall faces and erosion control. 1056 -3 CERTIFICATIONS AND IDENTIFICATION Provide Type 1, Type 2 or Type 4 material certifications in accordance with Article 106 -3 for geosynthetics except certifications are not required for Type 1 through Type 3 geotextiles and Type 5a geotextiles . Type 1, Type 2 or Type 4 material certifications in accordance with Article 28
106-3 are required for Type 4a geotextiles. Define “mach ine direction” (MD), “cross -machine
direction” (CD) and “minimum average roll value” (MARV) in accordance with ASTM D4439. Provide certifications with MARV for geosynthetic properties as required. Test geosynthetics using laboratories accredited by the G eosynthetic Accreditation Institute (GAI) to perform the required test methods. Sample geosynthetics in accordance with ASTM D4354. Allow the Engineer to visually identify geosynthetic products before installation. Open packaged geosynthetics just before use in the presence of the Engineer to verify the correct product. Geosynthetics that are missing original packaging or product labels or that have been unwrapped or previ ously opened will be rejected unless otherwise approved by the Engineer . 1056 -4 GEOTEXTILES Provide geotextile types and classes in accordance with the contract. Use woven or nonwoven geotextiles with properties that meet Table 1056- 1.
10-82 Table 1056 -1
GEOTEXTILE REQUIREMENTS PropertyA Requirement (MARVA) Test Method Type 1 Type 2 Type 3B Type 4 a Type 5 aC Typical Application Shoulder Drains Under Rip Rap Silt Fence Fabric Soil Stabilization Subgrade Stabilization Elongation (MD & CD)A ≥ 50% ≥ 50% ≤ 25% < 50% < 50% ASTM D4632 Grab Strength (MD & CD)A Table 1D, Class 3 Table 1D, Class 1 100 lb - - ASTM D4632 Tear Strength (MD & CD)A - ASTM D4533 Puncture Strength - ASTM D6241 Ultimate Tensile Strength (MD & CD)A - - - 2,400 lb/ft Table 12D, Class 4A ASTM D4595 Permittivity Table 2D, 15% to 50% in Situ Soil Passing 0.075 mm Table 6D, 15% to 50% in Situ Soil Passing 0.075 mm Table 7 D Table 12D, Class 4A Table 12D, Class 4A ASTM D4491 Apparent Opening Size ASTM D4751 UV Stability (Retained Strength) ASTM D4355
A.MD, CD and MARV per Article 1056 -3.
B.Minimum roll width of 36 inches required.
C.Minimum roll width of 13 feet required unless otherwise approved by the Engineer for the application .
D.Per AASHTO M 288 . 1056 -5 GEOCOMPOSITE DRAINS Provide geocomposite drain types in accordance with the contract and with properties that meet Table 1056- 2. TABLE 1056 -2 GEOCOMPOSITE DRAIN REQUIREMENTS Property Requirement Sheet Drain Strip Drain Wick Drain Test Method Width ≥ 12" 12" ±1/4" 4" ±1/4" N/A In-Plane Flow RateA (with gradient of 1.0 and 24- hour seating period) 6 gpm/ft @ applied normal compressive stress of 10 psi 15 gpm/ft @ applied normal compressive stress of 7.26 psi 1.5 gpmB @ applied normal compressive stress of 1.45 psi ASTM D4716
A.MARV per Article 1056- 3.
B.Per foot of width tested . For sheet and strip drains, use accessories (e.g., pipe outlets, connectors, fittings, etc.)
10-83 recommended by the Drain Manufacturer. Provide sheet and strip drains with Type 1
geotextiles heat bonded or glued to HDPE, polypropylene or high impact polystyrene drainage cores that meet Table 1056 -3. TABLE 1056 -3 DRAINAGE CORE REQUIREMENTS Property Requirement Test Method Sheet Drain Strip Drain Thickness 1/4" 1" ASTM D1777 or D5199 Compressive StrengthA 40 psi 30 psi ASTM D6364
A.MARV per Article 1056- 3. For wick drains with a geotextile wrapped around a corrugated drainage core and seamed to itself, use drainage cores with an ultimate tensile strength of at least 225 lbs. per 4 inch width in accordance with ASTM D4595 and geotextiles with properties that meet Table 1056 -4. TABLE 1056 -4 WICK DRAIN GEOTEXTILE REQUIREMENTS Property Requirement Test Method Elongation ≥ 50% ASTM D4632 Grab Strength Table 1A, Class 3 ASTM D4632 Tear Strength ASTM D4533 Puncture Strength ASTM D6241 PermittivityB 0.7 sec-1 ASTM D4491 Apparent Opening Size (AOS) Table 2A, > 50% in Situ Soil Passing 0.075 mm ASTM D4751 UV Stability (Retained Strength) ASTM D4355
A.Per AASHTO M 288.
B.MARV per Article 1056 -3. For wick drains with a geotextile fused to both faces of a corrugated drainage core along the peaks of the corrugations, use wick drains with an ultimate tensile strength of at least 1,650 lbs. per 4 inch width in accordance with ASTM D4595 and geotextiles with a permittivity, AOS and UV stability that meet Table 1056 -4. 1056 -6 GEOCELLS Manufacture geocells from virgin polyethylene resin with no more than 10% rework, also called “regrind”, materials. Use geocells made from textured and perforated HDPE strips with an open area of 10% to 20% and properties that meet Table 1056- 5.
Source: North Carolina Standard Specifications for Roads and Structures, 2024 Edition. Pages 497–499 of 857.