The BBA has awarded this Agrément Certificate for Tensar RE Geogrids for Reinforced Soil Embankments toTensar International Limited as fit for their intended use provided they are installed, used and maintained asset out in this Agrément Certificate.

On behalf of the British Board of Agrément

Date of First issue: 4 August 1999 Head of Approvals Chief Executive

Date of Second issue: 28 March 2008 — Engineering

Tensar International LimitedCunningham CourtShadsworth Business ParkBlackburnLancashire BB1 2QXTel: 01254 262431 Fax: 01254 266868e-mail: info@tensar-international.comwebsite: www.tensar-international.com

Roads and BridgesAgrément Certificate

No 99/R113

PRODUCT SHEET 1 — TENSAR RE GEOGRIDS FOR REINFORCED SOIL EMBANKMENTS

This Certificate relates to Tensar RE Geogrids ForReinforced Soil Embankments.

AGRÉMENT CERTIFICATION INCLUDES:• factors relating to compliance with Building

Regulations where applicable• factors relating to additional non-regulatory

information where applicable• independently verified technical specification• assessment criteria and technical investigations• design considerations• installation guidance• regular surveillance of production• formal three-yearly review.

British Board of Agrément tel: 01923 665300Bucknalls Lane fax: 01923 665301Garston, Watford e-mail: mail@bba.star.co.ukHerts WD25 9BA website: www.bbacerts.co.uk©2008

PRODUCT SCOPE AND SUMMARY OF CERTIFICATE

Page 1 of 12

KEY FACTORS ASSESSEDMechanical properties — the following key areas have been evaluated:• short-term tensile strength and elongation and long-term tensile strength properties of geogrids (see sections 6.1

to 6.4)

• safety factors for manufacture and extrapolation of data (fm), installation damage (fd) and environmental effects (fe)(see sections 6.6 to 6.8)

• soil/geogrid interaction (bond strength and direct sliding) (see sections 6.15 to 6.18).

Durability — geogrids have good resistance to oxidation, chemical corrosion, biodegradation, temperature and UVexposure used in fills normally encountered in civil engineering practice (see section 7).

The BBA is a UKAS accredited certification body — Number 113. The schedule of the current scope of accreditation for product certification isavailable in pdf format via the UKAS link on the BBA website at www.bbacerts.co.uk

Readers are advised to check the validity and latest issue number of this Agrément Certificate by either referring to the BBA website or contacting the BBA direct.

The Highways Agency requirements to which this Certificate is subject are detailed on page 2

Approval procedures shall be in accordance with HA Standard HD 22/02 (DMRB 4.1.2) (Design Manual for Roadsand Bridges).

The products are for use in the following situations:• embankments with an effective slope of up to 70°.The design, materials specification and construction methods adopted shall be in accordance with HA Advice NoteHA 68/94 (DMRB 4.1.4) and the Manual of Contract Documents for Highway Works (MCHW)(1), Volumes 1 and 2.(1) The MCHW is operated by the Overseeing Organisations: The Highways Agency (HA), Transport Scotland, the Welsh Assembly Government

and The Department for Regional Development (Northern Ireland).

Regulations

Construction (Design and Management) Regulations 2007

Construction (Design and Management) Regulations (Northern Ireland) 2007

Information in this Certificate may assist the client, CDM co-ordinator, designer and contractors to address theirobligations under these Regulations.See sections: 2 Delivery and site handling (2.1) and 8 General.

GeneralThis Certificate relates to Tensar RE Geogrids For Reinforced Soil Embankments for use as reinforcement inembankments with slope angles up to 70°.

The products provide lateral restraint to suitable cohesive or frictional soils in embankments, with stability achieved bythe interaction and interlocking of the soil particles with the Tensar RE Geogrids.

The design and construction of embankments must be in accordance with the requirements of the Highways Agency(HA); acting on behalf of the Department for Transport, the Scottish Executive, the Welsh Assembly Government, andthe Department for Regional Development, Northern Ireland and the conditions set out in the Design Considerationsand Installation parts of this Certificate.

The products are manufactured by the Certificate holder. Tensar is a registered trademark of the Certificate holder inthe UK and other countries.

Technical Specification

1 Description1.1 Tensar RE Geogrids For Reinforced Soil Embankments (40RE, 55RE, 80RE, 120RE and 160RE) are manufacturedfrom sheet polyethylene. The sheet is punched and stretched under temperature-controlled conditions (see Figure 1) tothe dimensions shown in Figure 2. The products are cut to length and rolled.

Page 2 of 12

Highways Agency Requirements

Figure 1 Manufacturing process

polymer sheet

punched sheetuniaxial grid

Page 3 of 12

1.2 The mechanical range and dimensional specification for the geogrids assessed by the BBA are given in Figure 2and Table 1.

1.3 Factory production and control is exercised through all stages of manufacture and includes checks on incomingmaterials, manufacturing rates and temperatures, weights of rolls and properties of the final product.

1.4 Tensar RE bodkins are high-density polyethylene bars bought in to Tensar International’s specifications and areshown in Figure 2. They are used to join lengths of Tensar RE geogrids when a full strength connection is necessary.

Table 1 Tensar RE geogrid properties

Dimension(1) Geogrid grade40RE 55RE 80RE 120RE 160RE

Bar pitch RL 235 235 235 235 230Rib width RW 6.0 6.0 6.0 6.0 6.0Rib thickness Rt 0.7 0.9 1.3 2.0 2.6Clear space between ribs Rs 16 16 16 16 16Bar width BW 16 16 16 16 16Bar thickness Bt 1.8 to 2.0 2.5 to 2.7 3.4 to 3.7 5.5 to 5.9 7.1 to 7.7Grid mass (kgm–2) 0.34 0.42 0.60 0.94 1.26Mean grid size 22 x 235 22 x 235 22 x 235 22 x 235 22 x 230Mean aperture size 16 x 219 16 x 219 16 x 219 16 x 219 16 x 214Roll length (m) 50 50 50 50 30Roll width (m) 1.0 or 1.3 1.0 or 1.3 1.0 or 1.3 1.0 or 1.3 1.0 or 1.3Weight of roll (kg) 18.5 or 23.0 22.0 or 28.0 31.0 or 41.0 48.0 or 62.0 39.0 or 51.0Colour coding Blue Yellow Orange Dark Green Red

(1) Dimensions in mm unless shown otherwise.

Figure 2 Tensar uniaxial grids

80 mm

8 mm

55RE, 80RE,120RE, 160RE

40 mm

6 mm

40RE

for dimensions see Table 1

geogrid

bodkin

ribs

roll

wid

th

roll length

(longitudinal)

bars

RL

RSBW(tran

sver

se)

Rt Bt

RW

1050 or 1350 mm

Page 4 of 12

2 Delivery, storage and site handling2.1 The geogrids and bodkins should be handled and stored generally in accordance with HA requirements.

2.2 The geogrids are delivered to site in rolls, bound with self-adhesive tape bearing the product grade and batchidentification references (see Figure 3). The ends of the rolls are sprayed with colour-coded paint to ease identificationof a particular grade of geogrid on site (see Table 1), in accordance with BS EN ISO 10320 : 1999.

2.3 Prior to installation, it is recommended that geogrids and bodkins are stored under cover in clean, dry conditions.The rolls must be protected from any form of mechanical damage, which will impair their load carrying capacity, andfrom exposure to extreme temperatures.

Assessment and Technical Investigations

The following is a summary of the assessment and technical investigations carried out on Tensar RE Geogrids ForReinforced Soil Embankments.

Design Considerations

3 General3.1 Tensar 40RE, 55RE, 80RE, 120RE and 160RE geogrids are satisfactory for use as polymeric reinforcement toembankments, with maximum slope angles of 70°, with stability achieved through the interaction and interlocking of thesoil particles and the geogrids.

3.2 Prior to the commencement of the work, the designer shall satisfy the HA geotechnical certification requirements.

3.3 The geogrids may be used:• in combination with soil types having an effective angle of shearing resistance in the range of 15° to 50°, and• where the design is in accordance with the procedures given in HA 68/94 (DMBR 4.1.4).

3.4 Prior to, during and after installation, particular care should be taken to ensure:• site preparation and embankment construction is as detailed in section 8• fill properties satisfy the design specification• drainage is adequate at all stages of construction, as required by the contract documents• the geogrids are protected against damage from site traffic and installation equipment, and• the stability of existing structures is not affected.

4 Practicability of installationThe products are easily installed by trained ground engineering contractors in accordance with the specifications andconstruction drawings (see the Installation part of this Certificate).

5 DesignReinforced soil structure5.1 For reinforced embankment projects in the UK, when designs are carried out by, or on behalf of, the manufacturer,these are in accordance with the procedures given in HA 68/94 (DMRB 4.1.4).

5.2 Working drawings should show the correct orientation of the geogrids.

Facings5.3 Where the products are used to form the facing, natural or artificial protection should be provided for thegeogrids and the fill material, to provide protection against damage from ultraviolet light (UV), fire and vandalism, andto protect the fill material from erosion. Other facing covers or panels may be used but these are beyond the scope ofthis Certificate. Typical examples are shown in the Figure in section 10.

Fill properties5.4 The designer should specify the relevant properties of a fill material deemed ‘acceptable’ for the purpose of thedesign. ‘Acceptable’ materials should meet the requirements of MCHW1 and HA 68/94 (DMRB 4.1.4).

Figure 3 Label

6 Mechanical propertiesTensile strength — short-term6.1 The geogrids have the tensile short-term properties as shown in Table 2.

Table 2 Performance characteristics

Grade Short-term tensile strength(1) �s(2) Ratio of bearing(3) Strain at

Machine Direction (MD) surface to plan area maximumPult �b x B/2S tensile

kNm–1 strength(4) (%)

40RE 57.4 (–4.6) 0.41 0.003 9.3 ± 0.955RE 67.4 (–2.9) 0.41 0.004 8.9 ± 1.180RE 93.5 (–4.8) 0.41 0.005 9.1 ± 0.9120RE 143.7 (–6.4) 0.41 0.008 10.0 ± 1.0160RE 189.2 (–11.5) 0.41 0.010 10.8 ± 1.0

(1) Short-term tests in accordance with BS EN ISO 10319 : 1996, the values given are mean values of strength and tolerance (–) values correspond to the95% confidence level in accordance with BS EN 13251 : 2001.

(2) �s is the proportion of the plane sliding area that is solid and �s is required for the calculation of the bond coefficient fb and the direct slidingcoefficient fds.

(3) The ratio is required to calculate bearing resistance in accordance with CIRIA SP123 : 1996 Soil Reinforcement with Geotextiles, Jewell R.A, and is theproduct of the bar thickness (BW) and the clear space between ribs (Rs) divided by twice the plan area (see section 6.16).

(4) Tests in accordance with BS EN ISO 10319 : 1996, the values given are the mean and tolerance values (±) of strain in accordance withBS EN 13251 : 2000.

Tensile strength — long-term6.2 Long-term creep strain and rupture testing, generally in accordance with the principles of BS EN ISO 13431 :1999, has been carried out for periods in excess of 100 000 hours and at varying test temperatures, to cover therange of geogrids detailed in this Certificate.

6.3 Using principles of time/temperature superposition, predicted long-term strengths for a design life of 120 years ata design temperature of 10°C or 20°C have been obtained from the measured data without the need for directextrapolation.

6.4 For the ultimate limit state, values have been determined for the tensile creep rupture strength, PC at 60 years and120 years as given in Table 3.

Material safety factors6.5 In establishing the design strength of the geogrids and ensuring that during the life of the embankment the geogridwill not fail in tension, the BBA recommends that, in line with the method of HA 68/94, a set of partial material safetyfactors should be applied to the value for long-term strength (PC). Conditions of use outside the scope for which partialsafety factors are defined (see also sections 6.6 to 6.8) are not covered by this Certificate and advice should besought from the manufacturer.

Manufacture and extrapolation of data — partial safety factor (fm)6.6 To allow for variation in manufacture and product dimensions and to account for extrapolation of data, anappropriate value for fm should be selected from Table 4.

Page 5 of 12

Table 3 Tensile creep rupture strength, PC

Grade Tensile creep rupture strength, PC (kNm�1)60 years 120 years

10°C 20°C 10°C 20°C

40RE 24.5 21.8 24.0 21.455RE 30.1 26.8 29.5 26.380RE 39.9 35.5 39.0 34.8120RE 64.4 57.4 63.1 56.2160RE 74.6 66.5 73.1 65.1

Table 4 Partial material safety factor — manufactureand extrapolation of data

Design life Safety factor(years) (fm)

60 1.00

120 1.00

Page 6 of 12

Installation damage and environmental effects — partial safety factors (fd and fe)6.7 To allow for loss of strength due to mechanical damage that may be sustained during installation, theappropriate value for fd may be selected from Table 5. The partial safety factors given for site damage assume thatwell-graded material is used (coefficient of uniformity >5) and with a minimum compacted depth of 150 mm andwere established from fill with the grading shown in Figure 4. For soils not covered by Table 5, appropriate valuesof fd may be determined from site specific trials.

6.8 To account for environmental conditions the appropriate value for fe should be selected from Table 6. For soilswith pH values outside the range quoted, consideration should be given to an increased value for fe.

Chemical resistance6.9 The geogrids have a high resistance to degradation from the types of chemicals typically found in soils used forcivil engineering purposes.

Microbial attack6.10 The geogrids are highly resistant to microbial attack.

Effects of temperature6.11 Where the geogrids may be exposed to temperatures higher than 30°C or lower than 0°C for significantperiods of time, consideration should be given to the temperature levels, the range of temperatures, period of exposureand stress levels at the location in question.

Resistance to oxidation6.12 The geogrids are effectively stabilised against long-term oxidative effects.

Resistance to UV light6.13 The geogrids have a high resistance to UV light. The BBA recommend that natural or artificial protection shouldbe provided to protect exposed geogrids and fill materials within 12 months of initial exposure to natural daylight.

Table 5 Short-term effects of installation damage

Crushed gritstone of maximum particle size (mm) fd(1)

40RE 55RE 80RE 120RE 160RE

<6 1.00 1.00 1.00 1.00 1.00<37.5 1.07 1.07 1.07 1.00 1.00<75(2) 1.25 1.20 1.15 1.06 1.01<125 1.48 1.36 1.25 1.12 1.02(1) Determined via full-scale installation test following the method of annex D of BS 8006 : 1995.(2) Values for 75 mm particle size have been interpolated.

Figure 4 Particle size distribution of fill used in installation damage testing

0.01 0.1 1 10 100 10000

20

40

60

80

100

particle size (mm)

pere

cent

age

pass

ing

(%)

Fine fill <6 mm

Medium fill <37.5 mm

Coarse fill <125 mm

Table 6 Partial safety factor — environmental effects (fe)

Soil pH level Safety factor (fe)2.0 to 4.0 1.054.0 to 12.5 1.00

Page 7 of 12

Design load (Pdes)6.14 The maximum design load (Pdes) that the reinforcement can be relied upon to deliver at the end of the design lifeand at the design temperature, (Pdes) can be calculated from the equation:

PcPdes =fd fe fm

Fill/Tensar RE geogrid interaction

Bond strength6.15 The bond strength for geogrid reinforcement may be expressed as:fbtan�’ where fb is the bond coefficient.

6.16 The use of laboratory pull-out testing to determine the value of the bond coefficient (fb) is not recommended atpresent. For routine design purposes, values may be estimated using the method of Jewell (section 4.6 of CIRIASP123, 1996). The BBA recommend that site specific pull-out testing is carried out to confirm the value of bondcoefficient (fb) used in the final design. Values of fb �1.0 have been reported based on site and soil specific testing.

Direct sliding6.17 The direct sliding resistance of geogrid reinforcement may be expressed as:fdstan�’ where fds is a direct sliding coefficient.

( tan� )fds = �s + (1–�s)tan�’

( tan� )where is the coefficient of skin friction (fsf), and �s is the proportion of plane sliding area that is solid.tan�’

6.18 For the geogrids the coefficient of skin friction (fsf) may be assumed, for routine design purposes, to be 0.6 forcompacted frictional fill. This is a conservative value. Where a more precise value is required, for use in design,suitable soil and geogrid specific shear box testing may be carried out. Soil specific testing has shown that values of fdsapproaching 1.0 can be achieved.

Formulae notation� = angle of friction between soil and plane reinforcement surface

�’ = effective angle of friction of soil.

7 DurabilityIn the opinion of the BBA, when used and installed in accordance with this Certificate, the geogrids can be used toachieve a design life of 120 years (see sections 6.8 to 6.13).

Installation

8 GeneralCare should be exercised to ensure Tensar RE Geogrids For Reinforced Soil Embankments are laid with the longitudinaldirection parallel to the direction of principal stress. Design drawings should indicate such features as geogrid orientation.

9 PreparationThe formation is prepared by levelling and compacting the subgrade in accordance with MCHW1. The surface mustbe free of root growth, logs, frozen matter and any other obstacles that may damage the geogrids.

10 Procedure10.1 The geogrid is laid by unrolling it to the length required and cutting with a suitable device. The unrolling of thegrid may be carried out manually or mechanically.

10.2 The grids should be laid flat without folds, parallel to each other and with widths in contact. Each reinforcinglayer must be continuous in the direction of loading and there should be no overlapping of the grids. Stripmisalignment must not exceed 50 mm over a distance of 5 m. Pins or a stretching device may be used to controlalignment and also to induce a small pre-stressing load prior to filling.

10.3 Fill is placed to a minimum depth of 150 mm, with particular care being taken to ensure that grids areadequately covered before compaction or trafficking. Construction traffic will damage unprotected geogrids.

10.4 Maximum thickness of compaction layers depends on the design, type of fill and compaction equipmentemployed, but depths should not exceed 500 mm.

10.5 Facings are positioned as detailed on the engineer’s design drawing. Where geogrids are used as facings,they must be wrapped around and anchored back into the fill. Formwork is used to assist in maintaining the shape ofthe facing. Facings, prefabricated or otherwise, are beyond the scope of this Certificate. Typical examples are shownin Figure 5.

10.6 Tensar bodkins (see Figure 6) are used to join lengths of geogrid when a full strength connection is necessary.

Figure 5 Installation and typical examples of facings

angled steelfacing units

(1)

establishmentof vegetation

durable steelmesh face

(1)

establishmentof vegetation

positiveconnectionto face

bagwork face supportbags filled withsuitable material

(1)

primary reinforcementwrapped aroundto form facing

temporary formwork(1)

primary reinforcementwrapped aroundto form facing

Liner(1)

Tensar REgeogrids

Tensar REgeogrids

positiveconnection to face

top layeranchored into fill

wrap-around facingconnection

Tensar primaryreinforcement(uniaxial geogrid)

optional Tensarsecondary reinforcement(biaxial geogrid)

(1)

top layeranchored into fill

wrap-around facing connection

Tensar primary reinforcement(uniaxial geogrid)

optional Tensarsecondary(biaxial geogrid)

reinforcement(1)

(1) Items are beyond the scope of this Certificate

Page 8 of 12

Page 9 of 12

Technical Investigations11 Investigations11.1 The manufacturing process of the Tensar RE Geogrids For Reinforced Soil Embankments was examined, includingthe methods adopted for quality control, and details were obtained of the quality and composition of the materials used.

11.2 An examination was made of data relating to:• evaluation of long- and short-term tensile properties• an assessment of the test method for determining tensile creep rupture and creep strain results in comparison with the

method given in BS EN ISO 13431 : 1999• synergy of mechanical damage and chemical degradation on long-term creep performance• chemical resistance• UV and environmental degradation• effects of temperature• site damage trials and resistance to mechanical damage assessed to the method of annex D of BS 8006 : 1995• coefficient of friction between the products and the soil fill.

11.3 The practicability and ease of handling and installation were assessed.

11.4 An assessment of the design strength of the geogrid was made, assuming a design life of 60 years and120 years and a design temperature of 10°C or 20°C in accordance with HA 68/94.

Additional Information

The management systems of Tensar International have been assessed and registered as meeting therequirements of BS EN ISO 9001 : 2000 and BS EN ISO 14001 : 1996 by the British Standards InstituteQuality Assurance (Certificate No Q 05288 and EMS 86463 respectively).

Figure 6 Joint detail

Tensar geogrids

Tensar bodkin

Bibliography

BS 8006 : 1995 Code of practice for strengthened/reinforced soils and other fills

BS EN 13251 : 2001 Geotextiles and geotextile-related products — Characteristics required for use in earthworks,foundations and retaining structures

BS EN ISO 9001 : 2000 Quality management systems — Requirements

BS EN ISO 10319 : 1996 Geotextile — Wide width tensile test

BS EN ISO 10320 : 1999 Geotextiles and geotextile related products. Identification on site

BS EN ISO 13431 : 1999 Geotextiles and geotextile-related products. Determination of tensile creep and creeprupture behaviour

BS EN ISO 14001 : 1996 Environmental Management systems — Requirements

HA 68/94 Design Manual for Roads and Bridges : Volume 4, Geotechnics and Drainage, Section 1, Earthworks :Part 4, Design Methods for the Reinforcement of Highway Slopes by Reinforced Soil and Soil Nailing Techniques

HD 22/02 Design Manual for Roads and Bridges : Volume 4, Geotechnics and Drainage, Section 1, Earthworks :Part 2, Managing Geotechnical Risk

Manual of Contract Documents for Highway Works, Volume 1 Specification for Highway Works, August 1998 (asamended)

Manual of Contract Documents for Highway Works, Volume 2 Notes for Guidance on the Specification for HighwayWorks, August 1998 (as amended)

Page 10 of 12

Page 11 of 12

Conditions of Certification

12 Conditions12.1 This Certificate:• relates only to the product/system that is named and described on the front page• is granted only to the company, firm or person named on the front page — no other company, firm or person may

hold or claim any entitlement to this Certificate• is valid only within the UK• has to be read, considered and used as a whole document — it may be misleading and will be incomplete to be

selective• is copyright of the BBA• is subject to English law.

12.2 References in this Certificate to any Act of Parliament, Statutory Instrument, Directive or Regulation of theEuropean Union, British, European or International Standard, Code of Practice, manufacturers’ instructions or similarpublication, are references to such publication in the form in which it was current at the date of this Certificate.

12.3 This Certificate will remain valid for an unlimited period provided that the product/system and the manufactureand/or fabrication including all related and relevant processes thereof:• are maintained at or above the levels which have been assessed and found to be satisfactory by the BBA• continue to be checked as and when deemed appropriate by the BBA under arrangements that it will determine• are reviewed by the BBA as and when it considers appropriate

• remain in accordance with the requirements of the Highways Agency.

12.4 In granting this Certificate, the BBA is not responsible for:• the presence or absence of any patent, intellectual property or similar rights subsisting in the product/system or any

other product/system• the right of the Certificate holder to manufacture, supply, install, maintain or market the product/system• individual installations of the product/system, including the nature, design, methods and workmanship of or related

to the installation• the actual works in which the product/system is installed, used and maintained, including the nature, design,

methods and workmanship of such works.

12.5 Any information relating to the manufacture, supply, installation, use and maintenance of this product/systemwhich is contained or referred to in this Certificate is the minimum required to be met when the product/system ismanufactured, supplied, installed, used and maintained. It does not purport in any way to restate the requirements ofthe Health & Safety at Work etc Act 1974, or of any other statutory, common law or other duty which may exist at thedate of this Certificate; nor is conformity with such information to be taken as satisfying the requirements of the 1974Act or of any statutory, common law or other duty of care. In granting this Certificate, the BBA does not acceptresponsibility to any person or body for any loss or damage, including personal injury, arising as a direct or indirectresult of the manufacture, supply, installation, use and maintenance of this product/system.

British Board of Agrément tel: 01923 665300Bucknalls Lane fax: 01923 665301Garston, Watford e-mail: mail@bba.star.co.ukHerts WD25 9BA website: www.bbacerts.co.uk©2008

Page 12 of 12