Specification: Geogrid Reinforcement BaseGrid 22

SECTION

Specification for Geogrid Base Reinforcement

1.0 GENERAL

1.1 Section Includes

A. Geogrid for use as reinforcement of base or sub base layers.

1.2 Related Sections

A. Section 02050 - Basic Site Materials and Methods
B. Section 02100 - Site Remediation
C. Section 02200 - Site Preparation
D. Section 02300 - Earthwork
E. Section 02700 - Bases, Ballasts, Pavements and Appurtenances

1.3 Unit Prices

A. Method of Measurement: By the square yard or as indicated in contract documents including seams, overlaps and wastage.

B. Basis of Payment: By the square yard or as indicated in contract documents, installed.

1.4 References

A. AASHTO Standards

  1. T88 - Particle Size Analysis of Soils
  2. T90 - Determining the Plastic Limit and Plasticity Index of Soils
  3. T99 - The Moisture-Density Relations of Soils Using a 5.5 lb (2.5 kg) Rammer and a 12in (305 mm) Drop
  4. M288-06 - Geotextile Specification for Highway Applications
  5. AASHTO Guide for Design of Pavement Structures, 1993 and Supplement 1998.

B. American Society for Testing and Materials (ASTM):

  1. D 123 - Standard Terminology Relating to Textiles
  2. D 276 - Test Method for Identification of Fibers in Textiles
  3. D 4354 - Practice Method Sampling of Geosynthetics for Testing
  4. D 4355 - Test Method for Deterioration of Geotextiles from Exposure to Ultraviolet Light and Water (Zenon-Arc Type Apparatus)
  5. D 4439 - Terminology for Geotextiles
  6. D 4759 - Practice for Determining the Specification Conformance of Geosynthetics
  7. D 4873 - Guide for Identification, Storage and Handling of Geotextiles
  8. D 5321 - Test Method for Determining the Coefficient of Soil and Geosynthetic, or Geosynthetic and Geosynthetic Friction, by the Direct Shear Method.
  9. D 6637 - Standard Test Method for Determining the Tensile Properties of Geogrids by the Single Rib or Multi-Rib Tensile Method

C. Geosynthetic Research Institute (GRI) - GRI-GG5 - Test Method for Geogrid Pullout.
D. Federal Highway Administration (FHWA) - Geosynthetic Design and Constriction Guideline, Publication No. FHWA HI-95-038, May 1995.
E. American Association for Laboratory Accreditation (A2LA).
F. Geosynthetic Accreditation Institute (GAI) - Laboratory Accreditation Program (LAP).

1.5 Definitions

A. Minimum Average Roll Value (MARV): Property value calculated as typical, minus two standard deviations. Statistically it yields a 97.7 percent degree of confidence that any sample taken during quality assurance testing will exceed value reported.

1.6 Submittals

A. Submit the following:

Certification: The contractor shall provide to the Engineer a certificate stating the name of the manufacturer, product name, style number, chemical composition and other pertinent product information to fully describe the geosynthetic. The Certification shall state that the furnished geosynthetic meets MARV requirements of the specification as evaluated under the Manufacturer's quality control program. The certification shall be attested to by a person having legal authority to bind the Manufacturer.

1.7 Quality Assurance

A. Geogrid labeling, shipment and storage shall follow ASTM D-4873. Product labels shall clearly show the manufacturer or supplier name, style and roll number.

B. Each geogrid roll shall be wrapped with a material that will protect the geosynthetic from damage due to shipment, water, sunlight and contaminants.

C. During storage, geogrid rolls shall be elevated off the ground and adequately covered to protect them from the following: site construction damage, precipitation, extended ultraviolet radiation including sunlight, chemicals that are strong acids or strong bases, flames including welding sparks, excess temperatures and any other environmental conditions that may damage the physical property values of the geogrid.

2.0 PRODUCTS

2.1 Manufacturers

A. US Fabrics Inc
3904 Virginia Ave
Cincinnati, OH 45227
1-513-271-6000
1-513-271-4420 (fax)
www.usfabrics.com

2.2 Materials

A. Reinforcement Geogrid:

  1. Polymers used in the manufacture of geogrids shall consist of multiple layers of high-strength, extruded, biaxially oriented, polypropylene geogrids. The layers shall be rolled and stitched or welded together without superimposing the grids, creating a geogrid with random sized apertures designed to accommodate a variety of fill materials.
  2. The random aperture geometry, many tensile elements and multiple layers of the geogrid will enhance soil/geogrid interactions. "Punched and drawn" products shall not be acceptable.
  3. Approved geogrid is as follows: BaseGrid 22 by US Fabrics Inc.
  4. The geogrid shall meet the requirements of Table 1. All numeric values in Table 1 represent MARV in the specified direction.
TECHNICAL CHARACTERISTICS TEST METHOD UNIT BaseGrid 22 NOTES
MD TD
Strengths and Load Capacity:
Peak Tensile Strength		 ASTM D 6637 lb/ft (kN/m) 925 (13.5) 1,400 (20.5) a,c,d
True Tensile Strength in Use:@ 2% Strain @ 5% Strain ASTM D 6637 lb/ft (kN/m) 301 (4.4)616 (9.0) 450 (6.57)920 (13.42) a,c,d a,c,d
True Initial Modulus in Use ASTM D 6637 lb/ft (kN/m) 17,140 (250) 27,420 (400) a,c,d
Tensile Modulus: @ 2% Strain ASTM D 6637 lb/ft (kN/m) 15,050 (220) 22,500 (328) a,c,d
@ 5% Strain     12,320 (180) 18,400 (269) a,c,d
Structural Integrity:
Junction Tensile Strength:@ 1% Strain @ 2% Strain		 GRI-GG2 lb/ft (kN/m) 170 (2.48)235 (3.44) 200 (2.92)300 (4.38) b,db,d
Junction Tensile Modulus: @ 1% Strain @ 2% Strain GRI-GG2 lb/ft (kN/m) 17,000 (248)11,780 (172) 20,000 (292)15,000 (219) b,db,d
Junction: Strength Efficiency GRI-GG2 lb/ft (kN/m)% 860 (12.55)90 1,315 (19.2)90 a,da,d
Flexural Rigidity ASTM D 1388 mg-cm 250,000 250,000 b
Pullout Coefficient of Interaction ASTM D 6707   > 1.0 > 1.0 e
Durability:
Resistance to Installation Damage		 ASTM D 5818 %SC/%SW/%GP >90/>90/90 >90/>90/90 f

1MD - Machine, or roll, direction; CD - Cross machine direction.

2.3 Quality Control

A. Manufacturing Quality Control: Testing shall be performed at a laboratory accredited by GAI-LAP and A2LA for test required for the geosynthetic at a frequency meeting or exceeding ASTM D-4354.

3.0 EXECUTION

3.1 Preparation

A. The installation site shall be prepared by clearing, grubbing and excavating or filling the area to the design grade. This includes removal of topsoil and vegetation.

3.2 Installation

A. The geogrid shall be laid smooth without wrinkles or folds on the prepared subgrade in the direction of construction traffic. Adjacent geogrid rolls shall be overlapped as required in the plans. Overlaps shall be in the direction as shown on the plans. See table below for overlap requirements.

 

Soil CBR Method of Joining
Greater than 3 300 - 450 mm (12 - 18 in) overlap
1 - 3 600 - 1000 mm (24 - 40 in) overlap
0.5 - 1 1000 mm (40 in) overlap or sewn
Less than 0.5 Sewn
All roll ends 1000 mm (40 in) overlap or sewn

B. The base reinforcement geogrid shall be laid directly on the subgrade. The reinforcement geogrid shall be laid beneath or within the base course as directed by the engineer.

C. On curves, the geogrid may be folded or cut to conform to the curves. The fold or overlap shall be in the direction of construction and held in place by pins, staples or piles of fill rock.

D. Prior to covering, the geogrid shall be inspected by a certified inspector of the engineer to ensure that the geogrid has not been damaged during installation. Damaged geogrid, as identified by the Engineer, shall be repaired immediately. Cover the damaged area with a geogrid patch which extends an amount equal to the required overlap beyond the damaged area.

E. The sub-base or base shall be placed by end dumping onto the geogrid from the edge of the geosynthetic, or over previously placed sub-base or base aggregate. On soils with CBR>3, most rubber-tired vehicles can be driven at slow speeds: less than 16 km/h (10 mph) and in straight paths over the exposed geosynthetic without causing damage to the geogrid. Sudden braking and sharp turning should be avoided. Tracked construction equipment should not be operated directly upon the geogrid. A minimum fill soil thickness of 15 cm (6 in) is required prior to operation of tracked vehicles over the geogrid. Turning of tracked vehicles should be kept to a minimum to prevent tracks from displacing the fill and damaging the geogrid.

F. On subgrades having a CBR value of less than 1, the sub-base or base aggregate should be spread in its full thickness as soon as possible after dumping to minimize the potential of localized failure due to overloading of the subgrade.

G. Any ruts occurring during construction shall be filled with additional sub-base or base material and compacted to the specified density.

H. If placement of the backfill material causes damage to the geogrid, the damaged area shall be repaired as previously described above. The placement procedure shall then be modified to eliminate further damage from taking place.