TENSAR RE AND RE500 GEOGRIDS FOR REINFORCED SOIL EMBANKMENTS

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1 Tensar International Limited Cunningham Court Shadsworth Business Park Blackburn BB1 2QX Tel: Fax: website: APPROVAL INSPECTION TESTING CERTIFICATION TECHNICAL APPROVALS FOR CONSTRUCTION Roads and Bridges Agrément Certificate 99/R113 Product Sheet 1 TENSAR RE AND RE500 GEOGRIDS FOR REINFORCED SOIL EMBANKMENTS The Highways Agency requirements to which this Certificate is subject are detailed on page 2 PRODUCT SCOPE AND SUMMARY OF CERTIFICATE This Certificate relates to Tensar RE and RE500 Geogrids for Reinforced Soil Embankments. AGRÉMENT CERTIFICATION INCLUDES: factors relating to compliance with Highways Agency requirements where applicable factors relating to compliance with Regulations where applicable independently verified technical specification assessment criteria and technical investigations design considerations installation guidance regular surveillance of production formal three-yearly review. KEY FACTORS ASSESSED Mechanical properties the following key areas have been evaluated: short- and long-term tensile strength and elongation properties of geogrids (see sections 6.1 to 6.4) safety factors for manufacture and extrapolation of data (f m ), installation damage (f d ) and environmental effects (f e ) (see sections 6.6 to 6.8) soil/geogrid interaction (bond strength and direct sliding) (see section 6.15 to 6.18) Durability Tensar geogrids have good resistance to oxidation, chemical corrosion, biodegradation, temperature and UV exposure normally encountered in fills in civil engineering practice (see section 7). The BBA has awarded this Agrément Certificate to the company named above for the products described herein. These products have been assessed by the BBA as being fit for their intended use provided they are installed, used and maintained as set out in this Certificate. On behalf of the British Board of Agrément Date of Third issue: 4 February 2010 Brian Chamberlain Greg Cooper Originally certificated on 4 August 1999 Head of Approvals Engineering Chief Executive The BBA is a UKAS accredited certification body Number 113. The schedule of the current scope of accreditation for product certification is available in pdf format via the UKAS link on the BBA website at 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. British Board of Agrément tel: Bucknalls Lane fax: Garston, Watford mail@bba.star.co.uk Herts WD25 9BA 2010 website: Page 1 of 12

2 Highways Agency Requirements Approval procedures shall be in accordance with HA Standard HD 22/08 (DMRB 4.1.2) (Design Manual for Roads and Bridges). The products are for use in embankments with an effective slope of up to 70. The design, materials specification and construction methods adopted shall be in accordance with HA Advice Note HA 68/94 (DMRB 4.1.4) and the Manual of Contract Documents for Highway Works (MCHW), Volumes 1 and 2. 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 their obligations under these Regulations. See sections: 2 Delivery and site handling (2.1) and 8 General. General This Certificate relates to Tensar RE and RE500 Geogrids for Reinforced Soil Embankments, for use as reinforcement in embankments with slope angles up to 70. The products provide lateral restraint to suitable cohesive or frictional soils in embankments, with stability achieved by the interaction and interlocking of the soil particles with the Tensar RE and RE500 geogrids. The design and construction of embankments must be in accordance with the Design Considerations and Installation parts of this Certificate and the requirements of the HA (acting on behalf of the Department for Transport), the Scottish Executive Development Department, the Welsh Assembly Government, and the Department for Regional Development (Northern Ireland). Tensar is a registered trademark of the Certificate holder in the UK and other countries. Technical Specification 1 Description 1.1 Tensar RE and RE500 Geogrids for Reinforced Soil Embankments (40RE, 55RE, 80RE, 120RE, RE510, RE520, RE540, RE560, RE570 and RE580) are manufactured from sheet polyethylene. The sheet is punched and stretched under temperature-controlled conditions (see Figure 1) to the dimensions shown in Figure 2. The products are cut to length and rolled. 1.2 The range and dimensional specification of the RE and RE500 geogrids assessed by the BBA are given in Figure 2 and Tables 1 and 2 respectively. Figure 1 Manufacturing process punched sheet uniaxial grid polymer sheet Page 2 of 12

3 Figure 2 Uniaxial grids and bodkins Table 1 Tensar RE geogrid properties Dimension Geogrid grade 40RE 55RE 80RE 120RE Bar pitch R L Rib width R W Rib thickness R t Clear space between ribs R s Bar width B W Bar thickness B t 2.0 to to to to 6.0 Grid mass (kg m 2 ) Mean grid size 22 x x x x 235 Mean aperture size 16 x x x x 219 Roll length (m) Roll width (m) 1.0 or or or or 1.3 Weight of roll (kg) 19.0 or or or or 67.0 Colour coding Blue Yellow Orange Dark Green Dimensions in mm unless shown otherwise Page 3 of 12

4 Table 2 Tensar RE500 geogrid properties Dimension Geogrid grade RE510 RE520 RE540 RE560 RE570 RE580 Bar pitch R L Rib width R W Rib thickness R t Clear space between ribs R s Bar width B W Bar thickness B t 1.8 to to to to to to 6.0 Grid mass (kg m 2 ) Mean grid size 22 x x x x x x 235 Mean aperture size 16 x x x x x x 219 Roll length (m) Roll width (m) 1.0 or or or or or or 1.3 Weight of roll (kg) 23.0 or or or or or or 67.0 Colour coding Brown Blue Yellow Orange White Green Dimensions in mm unless shown otherwise 1.3 Factory production control is exercised through all stages of manufacture and includes checks on incoming materials, manufacturing rates and temperatures, weights of rolls and properties of the final product. 1.4 Tensar bodkins are high-density polyethylene bars bought in to Tensar International s specifications and are shown in Figure 2. They are used to join lengths of Tensar RE and RE500 geogrids when a full strength connection is necessary. 2 Delivery and site handling 2.1 Tensar RE and RE500 geogrids and bodkins should be handled and stored generally in accordance with HA requirements. 2.2 Tensar RE and RE500 geogrids are delivered to site in rolls, bound with self-adhesive tape bearing the product grade and batch identification references (see Figure 3). The ends of the rolls are sprayed with colour-coded paint to ease identification of a particular grade of geogrid on site (see Tables 1 and 2), in accordance with BS EN ISO : Figure 3 Label 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, and from exposure to extreme temperatures. Assessment and Technical Investigations The following is a summary of the assessment and technical investigations carried out on Tensar RE and RE500 Geogrids for Reinforced Soil Embankments. Design Considerations 3 General 3.1 Tensar RE and RE500 geogrids are satisfactory for use as polymeric reinforcement to embankments, with maximum slope angles of 70, with stability achieved through the interaction and interlocking of the soil particles and the geogrids. Page 4 of 12

5 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 (DMRB 4.1.4). 3.4 Prior to, during and after installation, particular care should be taken to ensure that: site preparation and embankment construction is as detailed in section 8 the 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 the stability of existing structures is not affected. 4 Practicability of installation The products are easily installed by trained ground engineering contractors in accordance with the specifications and construction drawings (see the Installation part of this Certificate). 5 Design Reinforced soil structure 5.1 For reinforced embankment projects in the UK, designs carried out by, or on behalf of, the manufacturer should be 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. Facings 5.3 Where the products are used to form the facing, natural or artificial protection should be provided for the geogrids and the fill material, to provide protection against damage from ultraviolet light (UV), fire and vandalism, and to protect the fill material from erosion. Other facing covers or panels may be used but these are beyond the scope of this Certificate. Typical examples are shown in Figure 5. Fill properties 5.4 The designer should specify the relevant properties of a fill material deemed acceptable for the purpose of the design. Acceptable materials should meet the requirements of MCHW1 and HA 68/94 (DMRB 4.1.4). 6 Mechanical properties Tensile strength short-term 6.1 The short-term tensile properties of Tensar RE and RE500 geogrids are shown in Table 3. Table 3 Performance characteristics Grade Short-term tensile strength Machine Direction (MD) P ult (kn m 1 ) α s (2) Ratio of bearing (3) surface to plan area α b B/2S Strain at maximum tensile strength (4) (%) 40RE 57.0 ( 4.2) ± RE 68.0 ( 3.5) ± RE 93.0 ( 4.3) ± RE ( 4.7) ± 3.0 RE ( 4.0) ± 3.0 RE ( 4.2) ± 3.0 RE ( 3.5) ± 3.0 RE ( 4.3) ± 3.0 RE ( 4.6) ± 3.0 RE ( 4.7) ± 3.0 Short-term tests are in accordance with BS EN ISO : The values given are mean values of strength and tolerance ( ). Values correspond to the 95% confidence level in accordance with BS EN : (2) α s is the proportion of the plane sliding area that is solid and is required for the calculation of the bond coefficient f b and the direct sliding coefficient f ds. (3) The ratio is required to calculate bearing resistance in accordance with CIRIA SP123 : 1996 Soil Reinforcement with Geotextiles, Jewell R.A (see section 6.16), where α b is the proportion of the grid width available for bearing, B is the thickness of a transverse member of a grid taking bearing, equivalent to B t in Figure 1, S is the spacing between transverse members taking bearing, equivalent to R L in Figure 1. (4) Tests are in accordance with BS EN ISO : The values given are the mean and tolerance values (±) of strain in accordance with BS EN : Tensile strength long-term 6.2 Long-term creep strain and rupture testing, generally in accordance with the principles of EN ISO : 1999, has been carried out at varying test temperatures, to cover the range of Tensar RE and RE500 geogrids detailed in this Certificate. Page 5 of 12

6 6.3 Using principles of time/temperature superposition, predicted long-term strengths for a design life of 120 years and a design temperature of 10 C or 20 C have been obtained from the measured data without the need for direct extrapolation. 6.4 For the ultimate limit state, values have been determined for the tensile creep rupture strength, (P c ) at 60 years and 120 years as given in Table 4. Table 4 Tensile creep rupture strength (P c ) Grade Tensile creep rupture strength P c (kn m 1 ) 60 years 120 years 40RE 55RE 80RE 120RE RE510 RE520 RE540 RE560 RE570 RE C 20 C 10 C 20 C Material safety factors 6.5 In establishing the design strength of the geogrids and ensuring that, during the life of the embankment, the geogrid will not fail in tension, the BBA recommends that, in line with the method of HA 68/94, a set of partial material safety factors should be applied to the value for long-term strength (P C ). Conditions of use outside the scope for which partial safety factors are defined (see also sections 6.6 to 6.8) are not covered by this Certificate and advice should be sought from the manufacturer. Manufacture and extrapolation of data partial safety factor (f m ) 6.6 To allow for variations in manufacture and product dimensions and to account for extrapolation of data, an appropriate value for f m for design lives of both 60 and 120 years may be taken as Installation damage and environmental effects partial safety factors (f d and f e ) 6.7 To allow for any loss of strength due to mechanical damage that may be sustained during installation, the appropriate value for f d may be selected from Table 5. The partial safety factors given for site damage assume that well-graded material (coefficient of uniformity >5) with a minimum compacted depth of 150 mm is used, and were established from fill with the grading shown in Figure 4. For soils not covered by Table 5, appropriate values of f d may be determined from site specific trials. Figure 4 Particle size distribution of fill used in installation damage testing Fill <2 mm Fill <37.5 mm Fill <125 mm 70 percentage passing (%) particle size (mm) Page 6 of 12

7 Table 5 Short-term effects of installation damage Crushed gritstone of f d maximum particle size (mm) 40RE 55RE 80RE 120RE RE510 RE520 RE540 RE560 RE570 RE580 < < <75 (2) < 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 6.8 To account for environmental conditions the appropriate value for f e should be taken as 1.05 for soils with ph levels between 2.0 and 4.0, and 1.00 for soils with ph levels between 4.0 and For soils with ph values outside the range quoted, consideration should be given to an increased value for f e. Chemical resistance 6.9 The geogrids have a high resistance to degradation from the types of chemicals normally experienced in soils found in civil engineering applications. Microbial attack 6.10 The geogrids are highly resistant to microbial attack. Effects of temperature 6.11 Where the geogrids may be exposed to temperatures higher than 30 C or lower than 0 C for significant periods of time, consideration should be given to the temperature levels, the range of temperatures, the period of exposure and potential stress levels at the location in question. Resistance to oxidation 6.12 The geogrids are effectively stabilised against long-term oxidative effects. Resistance to UV light 6.13 The geogrids have a high resistance to UV light. The BBA recommends that natural or artificial protection for the geogrids and fill materials be in place within 12 months of initial exposure to natural daylight. Design load (P des ) 6.14 The maximum design load (P des ) that can be relied upon to be delivered at the end of the design life and at the design temperature can be calculated from the equation: P des = P c f d f e f m Fill/geogrid interaction Bond strength 6.15 The bond strength for geogrid reinforcement may be expressed as: f b tanϕ where f b is the bond coefficient The use of laboratory pull-out testing to determine the value of the bond coefficient (f b ) is not recommended at present. For routine design purposes, values may be estimated using the method of Jewell (CIRIA SP123, 1996, section 4.6). The BBA recommends that site specific pull-out testing is carried out to confirm the value of bond coefficient (f b ) used in the final design. Values of f b 1.0 have been reported based on site and soil specific testing. Direct sliding 6.17 The direct sliding resistance of geogrid reinforcement may be expressed as: f ds tanϕ where f ds is a direct sliding coefficient. f ds = α s ( tanδ ) + (1 α s) tanϕ where ( tanδ ) is the coefficient of skin friction (f sf), and α s is the proportion of plane sliding area that is solid. tanϕ 6.18 For the geogrids the coefficient of skin friction (f sf ) may be assumed, for routine design purposes, to be 0.6 for compacted 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 f ds approaching 1.0 can be achieved. Page 7 of 12

8 Formulae notation δ = angle of friction between soil and plane reinforcement surface ϕ = effective angle of friction of soil. 7 Durability In the opinion of the BBA, when used and installed in accordance with this Certificate, the geogrids can be used to achieve a design life of 120 years (see sections 6.8 to 6.13). Installation 8 General 8.1 In general, the execution of reinforced soil embankments should be carried out in accordance with MCHW1 and BS EN : Care should be taken to ensure that Tensar RE and RE500 Geogrids for Reinforced Soil Embankments are laid with the longitudinal direction parallel to the direction of principal stress. Design drawings should indicate such features as geogrid orientation. 9 Preparation The formation is prepared by levelling and compacting the subgrade in accordance with MCHW1. The surface must be free of root growth, logs, frozen matter and any other obstacles that may damage the geogrids. 10 Procedure 10.1 The geogrid is laid by unrolling it, either manually or mechanically, to the length required and cutting with a suitable device The grids should be laid flat without folds, parallel to each other and with widths in contact. Each reinforcing layer must be continuous in the direction of loading and there should be no overlapping of the grids. Strip misalignment must not exceed 50 mm over a distance of 5 m. Pins or a stretching device may be used to control alignment and also to induce a small pre-stressing load prior to filling Fill is placed to a minimum depth of 150 mm, with particular care being taken to ensure that grids are adequately covered before compaction or use by site traffic. Construction plant will damage unprotected geogrids The maximum thickness of compaction layers depends on the design, type of fill and compaction equipment employed, but depths should not exceed 500 mm 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 of the facing. Facings, prefabricated or otherwise, are beyond the scope of this Certificate. Typical examples are shown in Figure Tensar bodkins (see Figure 6) are used to join lengths of geogrid when a full strength connection is necessary. Page 8 of 12

9 Figure 5 Installation and typical examples of facings angled steel facing units establishment of vegetation positive connection to face Tensar uniaxial geogrids establishment of vegetation positive connection to face durable steel mesh face Tensar uniaxial geogrids bagwork face support bags filled with suitable material top layer anchored into fill temporary formwork top layer anchored into fill primary reinforcement wrapped around to form facing wrap-around facing connection Tensar primary reinforcement (uniaxial geogrid) optional Tensar secondary reinforcement (biaxial geogrid) primary reinforcement wrapped around to form facing liner wrap-around facing connection Tensar primary reinforcement (uniaxial geogrid) optional Tensar secondary reinforcement (biaxial geogrid) Items are beyond the scope of this Certificate Figure 6 Joint Detail Tensar RE geogrids Tensar RE500 geogrids Tensar bodkin Tensar bodkin Technical Investigations 11 Investigations 11.1 The manufacturing process of the Tensar RE and RE500 Geogrids for Reinforced Soil Embankments was examined, including the methods adopted for quality control, and details were obtained of the quality and composition of the materials used. Page 9 of 12

10 11.2 An examination was made of data relating to: evaluation of long- and short-term tensile properties assessment of the test method used for determining tensile creep rupture and creep strain results in comparison with the method given in EN ISO : 1999 synergy of mechanical damage and chemical degradation on long-term creep performance chemical resistance UV and environmental degradation the effects of temperature site damage trials and resistance to mechanical damage, assessed according to annex D of BS 8006 : 1995 the friction coefficient between the products and the soil fill The practicability and ease of handling and installation were assessed An assessment of the design strength of the geogrid was made, assuming a design life of 120 years and a design temperature of 10 C, in accordance with BD 70/03. Additional Information The management systems of Tensar International Limited have been assessed and registered as meeting the requirements of BS EN ISO 9001 : 2008 and BS EN ISO : 2004 by the British Standards Institute Quality Assurance (Certificate No Q05288 and EMS86463 respectively). Page 10 of 12

11 Bibliography BS 8006 : 1995 Code of practice for strengthened/reinforced soils and other fills BS EN : 2001 Geotextiles and geotextile-related products Characteristics required for use in earthworks, foundations and retaining structures BS EN ISO 9001 : 2008 Quality management systems Requirements BS EN ISO : 2008 Geotextiles Wide-width tensile test BS EN ISO : 1999 Geotextiles and geotextile-related products Identification on site BS EN ISO : 1999 Geotextiles and geotextile-related products Determination of tensile creep and creep rupture behaviour BS EN ISO : 2004 Environmental Management systems Requirements with guidance for use BS EN : 2006 Execution of special geotechnical works Reinforced fill BD 70/03 Strengthened/Reinforced Soils and other Fills for Retaining Walls and Bridge Abutments CIRIA SP123 : 1996 Soil Reinforcement with Geotextiles, Jewell R.A 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 22/08 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 (as amended) Manual of Contract Documents for Highway Works, Volume 2 Notes for Guidance on the Specification for Highway Works, August 1998 (as amended) Page 11 of 12

12 Conditions of Certification 12 Conditions 12.1 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 Publications and documents referred to in this Certificate are those that the BBA deems to be relevant at the date of issue or re-issue of this Certificate and include any: Act of Parliament; Statutory Instrument; Directive; Regulation; British, European or International Standard; Code of Practice; manufacturers instructions; or any other publication or document similar or related to the aforementioned This Certificate will remain valid for an unlimited period provided that the product/system and the manufacture and/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 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 Any information relating to the manufacture, supply, installation, use and maintenance of this product/system which is contained or referred to in this Certificate is the minimum required to be met when the product/system is manufactured, supplied, installed, used and maintained. It does not purport in any way to restate the requirements of the Health & Safety at Work etc Act 1974, or of any other statutory, common law or other duty which may exist at the date of this Certificate; nor is conformity with such information to be taken as satisfying the requirements of the 1974 Act or of any statutory, common law or other duty of care. In granting this Certificate, the BBA does not accept responsibility to any person or body for any loss or damage, including personal injury, arising as a direct or indirect result of the manufacture, supply, installation, use and maintenance of this product/system. British Board of Agrément tel: Bucknalls Lane fax: Garston, Watford mail@bba.star.co.uk Herts WD25 9BA 2010 website: Page 12 of 12