geo grid foundation stabilization installation instructions

March 2004 of 7 Specification for Mechanically Stabilized

Earth Foundation Improvement System

SECTION 0XX00

SPECIFICATION FOR MECHANICALLY STABILIZED

EARTH FOUNDATION IMPROVEMENT SYSTEM

## THIS SECTION IS WRITTEN IN CSI 3-PART FORMAT AND IN CSI PAGE FORMAT.

NOTES TO THE SPECIFIER, SUCH AS THIS, ARE INDICATED WITH A ## SYMBOL

AND MUST BE DELETED FROM THE FINAL SPECIFICATION.

IT IS ASSUMED THAT THE GENERAL CONDITIONS BEING USED ARE AIA A201-87.

SECTION NUMBERS ARE FROM THE 1995 EDITION OF MASTERFORMAT.

PART 1 GENERAL

1.01 SUMMARY

A. Section Includes - Mechanically Stabilized Earth (MSE) foundation improvement system having

structural geogrids that interact with cohesionless soil to create a stiffened, high modulus raft

foundation. Work consists of:

1. Providing supplier representative for pre-construction meeting with Contractor and Engineer.

2. Furnishing structural geogrid reinforcement as specified herein and shown on the construction

drawings.

3. Storing, cutting and placing structural geogrid reinforcement as specified herein and as shown on

the construction drawings.

4. Placement and compaction of reinforced fill within the MSE foundation improvement system as

specified herein and as shown on the construction drawings.

5. Incidental earthwork as necessary to complete the MSE foundation improvement system

specified herein and as shown on the construction drawings.

**Note that this section does not include site preparation, dewatering, shoring, establishing a working

platform or earthwork other than incidental earthwork.**

## EDIT LIST BELOW TO CONFORM TO PROJECT REQUIREMENTS. VERIFY SECTION

NUMBERS AND TITLES.

B. Related Sections

1. Section 02200 - Site Preparation

2. Section 02300 - Earthwork

C. Alternates

1. Geotextile materials will not be considered as an alternate to geogrid materials for the MSE

foundation improvement system. A geotextile may be used in the cross-section to provide

separation, filtration or drainage; however, no structural contribution will be attributed to the

geotextile.

2. Alternate geogrid materials shall not be used unless submitted to the Engineer and approved in

writing by the Engineer at least 7 days before the bid letting. Polyester geogrids, whether coated

or uncoated, will not be approved for use in calcareous, alkaline, or highly acidic environments

including lime-treated or cement-treated soils, crushed limerock, or soils potentially exposed to

leachate from cement, lime, or de-icing salts. In no case shall polyester geogrids be used in soils

with a pH > 9.

3. In order to be considered, submittal packages for alternate geogrid materials must include:

a. A list of 10 comparable projects that are similar in terms of size and application, are

located in the United States, and where the results of using the specific alternate geogrid

material can be verified a minimum of 1 year after installation.

b. A sample of the alternate geogrid material and certified specification sheets.

c. Recommended installation instructions.



d. An explanation of engineering techniques used, and sample design drawings and

calculations prepared and sealed by a Professional Engineer licensed in the State.

e. Additional information as required by the Engineer.

4. Engineer approval of alternative systems and suppliers will be based upon the following

considerations:

a. The reinforcement for the system has been reviewed and pre-approved for use.

b. The supplier has a large enough operation, adequate financial resources, and necessary

experience to supply and support the construction on a reliable and timely basis.

c. The material supplier/manufacturer has adequate Professional Engineers’ Errors and

Omissions insurance to cover the potential liability incurred as designer of record for the

system.

## DELETE REFERENCES NOT USED IN PART 2 OR PART 3.

1.02 REFERENCES

A. Geosynthetic Research Institute (GRI)

1. GG1-87 - Standard Test Method for Geogrid Rib Tensile Strength

2. GG2-87 - Standard Test Method for Geogrid Junction Strength

3. GG5-91 - Standard Test Method for “Geogrid Pullout”

4. GG7 - Standard Test Method for Carboxyl End Group Content of Poly(Ethylene Terephthalate)

(PET) Yarns

5. GG8 - Determination of the Number Average Molecular Weight of Poly(Ethylene

Terephthalate) (PET) Yarns Based on a Relative Viscosity Value

B. American Society for Testing and Materials (ASTM)

1. D698-98 - Standard Test Method for Laboratory Compaction Characteristics of Soil Using

Standard Effort

2. D1388-96 - Standard Test Method for Stiffness of Fabrics, Option A

3. D4603-96 - Test Method for Determining Inherent Viscosity of Poly(Ethylene Terephthalate)

(PET) by Glass Capillary Viscometer

4. D4759-92 - Practice for Determining the Specification Conformance of Geosynthetics

5. D4972-95a - Test Method for pH of Soils

C. U.S. Environmental Protection Agency (U.S. EPA)

1. EPA 9090 - Compatibility Test for Wastes and Membrane Liners

D. American Association of State Highway and Transportation Officials (AASHTO)

1. Standard Specification for Highway Bridges (1997 Interim)

E. U.S. Army Corps of Engineers (U.S. COE)

1. Draft specification for Grid Aperture Stability by In-Plane Rotation

F. Tensar Earth Technologies, Inc. (TET)

1. Dimension™ Solution Software

1.03 DEFINITIONS

A. Geogrid - A biaxial polymeric grid formed by a regular network of integrally connected tensile

elements with apertures of sufficient size to allow interlocking with surrounding soil, rock, or earth and

function primarily as reinforcement.

B. Multi-Layer Geogrid - A geogrid product consisting of multiple layers of grid which are not integrally

connected throughout.

C. Minimum Average Roll Value - Value based on testing and determined in accordance with ASTM

D4759-92.

D. True Junction Tensile Strength - True tensile strength of junctions at indicated strain levels when tested

in accordance with GRI-GG2 as modified by AASHTO Standard Specification for Highway Bridges,

1997 Interim, using a single rib having the greater of 3 junctions or 8 inches and tested at a strain rate

of 10 percent per minute based on this gauge length. Values shown are minimum average roll values.

For multi-layer geogrid products, junction tensile strength testing shall be performed across junctions



from each layer of grid individually, and results shall not be assumed as additive from single layers to

multiple layers.

E. True Junction Tensile Modulus - The ratio of junction tensile strength to corresponding strain (e.g. 1%,

2%). The junction tensile strength is measured via GRI-GG2 as modified by AASHTO Standard

Specification for Highway Bridges, 1997 Interim, using a single rib having the greater of 3 junctions or

8 inches and tested at a strain rate of 10 percent per minute based on this gauge length. Values shown

are minimum average roll values. For multi-layer geogrid products, junction tensile modulus testing

shall be performed across junctions from each layer of grid individually, and results shall not be

assumed as additive from single layers to multiple layers.

F. Flexural Stiffness - Resistance to bending force measured via ASTM D1388-96, Option A, using

specimen dimensions of 864 millimeters in length by 1 aperture in width. Values shown are minimum

average roll values. For multi-layer geogrid products, flexural stiffness testing shall be performed

directly on the multi-layer configuration without using any connecting elements other than those used

continuously throughout the actual product, and results shall not be assumed as additive from testing

performed on a single layer of the multi-layer product.

G. Torsional Stiffness - Resistance to in-plane rotational movement measured by applying a 20 kg-cm

moment to the central junction of a 9-inch by 9-inch specimen restrained at its perimeter (U.S. Army

Corps of Engineers Draft Specification for Grid Aperture Stability by In-Plane Rotation). Values

shown are minimum average roll values. For multi-layer geogrid products, torsional stiffness testing

shall be performed on each layer of grid individually, and results shall not be assumed as additive from

single layers to multiple layers.

H. Soil Interaction Coefficient - Ci value shall be determined from long-term effective stress pullout tests

per GRI-GG5, unless through the junction creep testing of the geogrid is used to determine Ta. The Ci

value is determined as follows:

Ci = F

2 L N tan

Where: F = Pullout force (lb/ft), per GRI-GG5

L = Geogrid Embedment Length in Test (ft)

N = Effective Normal Stress (psf)

= Effective Soil Friction Angle, Degrees

I. Resistance to Long-Term Degradation - Resistance to loss of load capacity or structural integrity when

subjected to chemically aggressive environments measured via EPA 9090 immersion testing. Values

shown are typical values.

J. Reinforced Fill - Compacted structural fill placed above and below the layers of geogrid, the reinforced

fill boundaries shall be defined as the limits of the MSE foundation system as indicated on the

construction drawings.

1.04 SYSTEM DESCRIPTION

## DIMENSION SOLUTION SOFTWARE IS AVAILABLE TO THE DESIGNER FROM TENSAR

EARTH TECHNOLOGIES.

A. Design Requirements - The MSE foundation improvement system shall have been designed using the

Dimension Solution Software or other approved methodology.

B. Performance Requirements for the MSE Foundation Improvement System - Design calculations should

substantiate that the proposed MSE foundation improvement system satisfies the allowable total and

differential settlement and bearing capacity factor of safety design parameters as shown in the

construction drawings or as required by the Engineer.

1.05 SUBMITTALS



A. Submit geogrid product data sheet and certification from the manufacturer that the geogrid product

supplied meets the requirements of sub-part 2.02 of this Section.

B. Submit manufacturer’s installation instructions and general recommendations.

C. Working Drawings for Alternative Foundation Support Systems or Materials.

1. Complete details, including working drawings and supporting design calculations, for any

alternative approved foundation support systems or materials shall be submitted by the

Contractor to the Engineer for review at least 4 weeks before construction. The Contractor shall

submit 6 sets of detailed design calculations, construction drawings, and shop drawings for

approval. The calculations and drawings shall be prepared and sealed by a Professional Engineer

licensed in the State. The design submittal provided by the Contractor shall indicate the

procedures by which the geogrid soil reinforcement will be installed. Working drawings and

calculations shall include the following:

a. Existing ground elevations that have been verified by the Contractor for each location

involving construction of a foundation system.

b. Complete design calculations substantiating that the proposed design satisfies the design

parameters shown in the construction drawings or as required by the Engineer.

c. Complete details of all elements required for the proper construction of the system,

including complete material specifications.

d. Earthwork requirements including specifications for material and compaction of backfill.

e. Other information requirements shown in the construction drawings or called out by the

Engineer.

2. The Contractor shall not start work on any alternative foundation improvement system or

material until such drawings have been approved by the Engineer. Approval of the working

drawings shall not relieve the Contractor of any of his/her responsibility under the contract for

the successful completion of the work.

1.06 QUALITY ASSURANCE

A. Designer - The design of the MSE foundation improvement system shall be performed by a

Professional Engineer who is registered in the State where the project is located and who is familiar

with geotechnical engineering.

B. Pre-Construction Conference - Before construction of the MSE foundation improvement system, hold a

meeting at the site with the geogrid supplier, Contractor, and the Designer to review the construction

procedure. Notify the Owner, the Engineer, and/or Architect at least 3 days in advance of the time of

the meeting. The representative of the geogrid supplier shall be available on an “as needed” basis

during construction.

1.07 DELIVERY, STORAGE, AND HANDLING

A. Storage and Protection

1. Prevent excessive mud, wet concrete, epoxy, or other deleterious materials from coming in

contact with and affixing to the geogrid materials.

2. Store at temperatures above –20 degrees F (-29 degrees C).

3. Rolled materials may be laid flat or stood on end.

PART 2 PRODUCTS

2.01 MANUFACTURERS

## VERIFY SECTION NUMBERS AND TITLES.

A. An approved source of geogrid is The Tensar Corporation, Morrow, GA, or their designated

representative.

B. Substitutions: See Section 01600 and sub-part 1.01C of this Section.



2.02 MATERIALS

## THE PLANS SHOULD INDICATE WHERE TYPE 1 GEOGRID IS TO BE USED AND

WHERE TYPE 2 GEOGRID IS TO BE USED.

A. Structural Geogrid

1. The structural geogrid shall accept applied force in use by positive mechanical interlock (i.e. by

direct mechanical keying) with compacted soil. The structural geogrid shall possess complete

continuity of all properties throughout its structure and shall be suitable for internal

reinforcement of compacted soil or particulate construction fill materials to improve their load

bearing capacity in structural load bearing applications.

2. Polyolefin geosynthetic materials can be used in fill material with pH levels between 2 and 12.

Polyester geosynthetic materials, whether coated or uncoated, shall not be used in calcareous,

alkaline, or highly acidic environments, including the following: lime-treated or cement-treated

soils, crushed limerock, or soils potentially exposed to leachate from concrete, lime or de-icing

salts.

3. Structural geogrid shall otherwise have the following characteristics:

PROPERTY UNITS TYPE 1 TYPE 2

True 1% Junction Tensile

Modulus in Use

• MD

• XMD

kN/m

(lb/ft)

250 (17,000)

290 (20,000)

320 (22,000)

440 (30,000)

True 2% Junction Tensile

Modulus in Use

• MD

• XMD

kN/m

(lb/ft)

170 (11,750)

220 (15,000)

270 (18,200)

370 (25,000)

True Junction Tensile

Strength in Use @ 1% Strain

• MD

• XMD

kN/m

(lb/ft)

2.5 (170)

2.9 (200)

3.2 (220)

4.3 (300)

True Junction Tensile

Strength in Use @ 2% Strain

• MD

• XMD

kN/m

(lb/ft)

3.4 (240)

4.4 (300)

5.3 (370)

7.3 (500)

Flexural Stiffness mg-cm 250,000 750,000

Torsional Stiffness kg-cm/deg 2.8 4.7

Interaction Coefficient

(Granular Soil)

1.0 1.0

Resistance to Long-Term

Degradation

% 100 100

2.03 BACKFILL MATERIALS

A. Reinforced Backfill - The fill material in the reinforced fill zone shall be cohesionless material with a

maximum particle size of 2 inches, have less than 15 percent passing the No. 200 Sieve, and an internal

friction angle of at least 30 degrees. In addition, if gravel is used as the fill material, it shall be well

graded.

2.04 CONSTRUCTION DOCUMENTATION



A. The Contractor shall establish and maintain quality control for foundation construction operations to

assure compliance with contract requirements and maintain detailed records of their quality control for

all construction operations. Three copies of all records of inspections and tests, and all of the records of

corrective action taken, shall be furnished to the Engineer on a monthly basis when work under this

section is being performed.

PART 3 EXECUTION

3.01 EXAMINATION

A. The Contractor shall check the geogrid upon delivery to verify that the proper material has been

received. The geogrid shall be inspected by the Contractor to be free of flaws or damage occurring

during manufacturing, shipping, or handling.

3.02 FOUNDATION PREPARATION

A. Brush, trees, logs, topsoil, and other debris shall be removed as specified in the contract documents.

No fill shall be placed on frozen ground. After clearing, grade smooth, compact, and establish the

proper elevations as shown on the construction drawings or as directed by the Engineer.

3.03 STRUCTURAL GEOGRID INSTALLATION

A. Structural geogrid shall be laid at the proper elevation and alignment as shown on the construction

drawings.

B. For square or rectangular footings, the structural geogrid shall be oriented such that the roll direction

runs perpendicular to the roll direction of the previous layer of geogrid. For strip footings, the

structural geogrid shall be oriented such that the roll length runs parallel to the footing direction. A

minimum of 2 layers of structural geogrid are required for the MSE foundation improvement system.

C. Geogrid may be temporarily secured in place with staples, pins, sand bags or backfill as required by fill

properties, fill placement procedures or weather conditions, or as directed by the Engineer.

D. Overlap

1. Structural geogrid sections shall be overlapped as indicated on the construction drawings or as

directed by the Engineer.

2. Minimum overlap is 1 foot (300 millimeters).

3. Care shall be taken to ensure that structural geogrid sections do not separate at overlaps during

construction. To prevent separation, simple joining methods may be utilized, such as wire tires,

plastic ties, hog rings, staples or hooks. Joint spacings of 20 to 30 feet are normally adequate to

prevent grid separation at overlaps.

3.04 GRANULAR FILL PLACEMENT OVER STRUCTURAL GEOGRID

## VERIFY SECTION NUMBERS AND TITLES.

A. The fill in the reinforced zone shall be placed in lift thickness as directed in the construction drawings

or as directed by the Engineer. The fill in the reinforced zone shall be compacted to a density of at least

95 percent maximum density as determined by Standard Proctor Test (ASTM D698-98), or an

equivalent fill density measured by other methods. Otherwise, the fill in the reinforced zone shall be

placed in lifts and compacted as directed under Section 02300 and Section 02700. Granular fill

material shall be placed, spread and compacted in such a manner that minimizes the development of

wrinkles in the geogrid and/or movement of the geogrid.

B. A minimum loose fill thickness of 6 inches 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. When integrally-formed geogrids are used, rubber-tired equipment may

pass over the geogrid reinforcement at slow speeds (less than 10 mph). When coated geogrids or



geogrids composed of small-diameter fibers are used, rubber-tired equipment shall not be allowed

directly on the geogrid. Sudden braking and sharp turning movements shall be avoided.

3.05 REPAIR

A. Any geogrid damaged during installation shall be replaced by the Contractor at no additional cost to the

Owner.

B. Coated geogrids shall not be used if the coating is torn, shedding, cracked, punctured, flawed or cut,

unless a repair procedure is carried out as approved by the Engineer. The repair procedure shall include

placing a suitable patch over the defective area or applying a coating solution identical to the original

coating.

3.06 PROTECTION

A. Follow the Manufacturer’s recommendations regarding protection from exposure to sunlight.

END OF SECTION

geo grid foundation stabilization installation instructions

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