Allan Block Wall System Project Name: Crossfield Street

Allan Block Wall System

Project Name: Crossfield Street, Blackburn

Client: Colinwell

HUESKER Reinforced Soil Wall Suggestion

Reference: 362/1118

Date: 28/11/2018

Name Signature Date

Designer Ian Scotland

28/11/2018

Checker Graham Horgan

28/11/2018

This document contains an outline design suggestion issued by HUESKER Limited. This document has been delivered to you at no charge for information only. The information in this

document, is illustrative and it is not a detailed design. It is specific to the unique characteristics of our geosynthetic products referenced within the calculations. It does not purport to

be comprehensive and has not been independently verified. While this information has been prepared in good faith, no representation or warranty, express or implied, is or will be

made and no responsibility or liability is or will be accepted by us or any of the companies in the same group of companies as us, or by any of their respective officers, employees or

agents in relation to the accuracy or completeness of this document or any other written or oral information made available to you or your advisers and any such liability is expressly

disclaimed. Copyright in this document belongs to us. It may not be reproduced in whole or in part without our prior written permission. It must not be disclosed to any third party other

than for the purpose of evaluating its commercial application for the use of our geosynthetic products.

HUESKER UK Limited 3 Quay Business Centre Winwick Quay Warrington WA2 8LT United Kingdom

Tel: 01925 629393 Fax: 01925 629393 email: [email protected] www.HUESKER.com

mailto:[email protected]

http://www.huesker.com/

HUESKER Design Suggestion Project: Crossfield Street, Blackburn Reference Number: 362/1118

Page 1

CONTENTS

1 INTRODUCTION ...................................................................................................................... 2

2 ALLAN BLOCK WALL ............................................................................................................ 3

3 DESIGN METHODOLOGY ...................................................................................................... 4

3.1 DESIGN STANDARDS ............................................................................................................ 4

3.2 DESIGN PROCESS ................................................................................................................ 4

External and Composite Stability .............................................................................................. 4

Internal Stability ........................................................................................................................ 5

4 DESIGN SUMMARY ................................................................................................................ 6

4.1 PROPERTIES........................................................................................................................ 6

4.2 REINFORCED RETAINING WALL DESIGN SUGGESTION ............................................................ 7

5 DISCLAIMER ........................................................................................................................... 9

6 APPENDIX ............................................................................................................................. 10

6.1 MATHCAD CALCULATIONS .................................................................................................. 10

6.2 DATA SHEETS: ................................................................................................................... 10

6.3 BBA HAPAS CERTIFICATES: .............................................................................................. 10


Page 2

1 INTRODUCTION

HUESKER Ltd. were invited by Colinwell to provide a design suggestion for the reinforced soil walls

required for the Crossfield Street, Blackburn.

Figure 1.1: Proposed Wall at Crossfield Street, Blackburn

This document is a summary report of the HUESKER design suggestion, calculations and

recommendations for the use of reinforced soil walls using Allan Block® segmental blocks and

Fortrac® geogrid. The suggestion is based on the following reinforced wall:

3.5 m Retaining Wall, + 0.5m embedded below ground level.

This report is based on information received from Colinwell including:

F6166-RW1B.pdf


Page 3

2 ALLAN BLOCK WALL

The reinforced soil system is designed to incorporate layers of Fortrac geogrid typically spaced at

400 mm centres, extending horizontally back from the face. The facing consists of Segmental block

wall facing, Allan Block, featuring a frictional Rock-Lock connection between geogrid and

segmental blocks.

See Colinwell’s Allan Block Brochure for more details.

Figure 2.1: Typical Fortrac Reinforced Allan Block System


Page 4

3 DESIGN METHODOLOGY

3.1 Design Standards

It has been compulsory in the UK since 2010 to adopt the Eurocodes for design of infrastructure

works. The Eurocode covering geotechnical design is Eurocode 7 (EN 1997:2004).

According to NA.4 in the UK National Annex to EN 1997-1: ‘EN 1997-1 Geotechnical Design does

not cover the design and execution of reinforced soil structures. In the UK, the design and execution

of reinforced fill structures and soil nailing should be carried out in accordance with BS 8006, BS EN

14475 and prEN 144901). The partial factors set out in BS 8006 should not be replaced by similar

factors from Eurocode 7.’

In common with the Eurocodes, BS8006: Part 1, 2010: Code of Practice for Strengthened/reinforced

soils and other fills published by the British Standards Institution adopts limit state principles. These

principles involve the application of partial material and load factors depending on structure types,

to ensure sufficient safety margins.

Therefore this design suggestion follows the recommendations and guidance of BS 8006, specifically

chapter 6 covering the design of reinforced soil walls.

3.2 Design process

The design of reinforced soil walls can be broken down into a number of limits states, each must be

assessed for the whole structure to be deemed satisfactory.

The design of reinforced soil walls can be considered in two parts:

External and Composite Stability

Internal Stability

External and Composite Stability

External stability checks consider global stability of the reinforced slope and the surrounding soils

such as retained fills and underlying stratum. Typically this is undertaken with Bishop’s slip circles method using partial factors (combinations 1 and 2) from Eurocode 7. As these are not calibrated for

‘reinforced soil’, the slip circles must pass outside the reinforced zone of wall.

This design suggestion has not considered a detailed check on global stability, as this is subject to

the properties of the underlying soils have only been assumed at this stage.

Composite stability has been assessed in this design suggestion. This check considers the stability

of the reinforced wall in combination with its surrounding soils, with slip circles only passing through

some part of the reinforced zone section, as suggested in BS 8006.

This assessment can be carried out using the commercially available GGU Stability software

package from Civil Serve. The software presents the results in terms of a mobilisation factor (µ),

whereby : μ= 1/Factor of safety. When adopting limit state partial factors, a minimum overall factor

safety equivalent to or greater than unity is required to satisfy equilibrium.


Page 5

Internal Stability

This aspect of the design is used to determine the amount of soil reinforcement required to maintain

the integrity of the reinforced soil mass. For polymer geogrid-based reinforced walls the internal

stability of the structure can be designed using either the two part wedge method, circular failure

method, log spiral failure passing partially through the reinforced zone and partially through the

backfill as described in clause 7.4.4 of BS8006:Part 1: 2010.

Sufficient reinforcement is provided to ensure the following internal failure modes do not occur:

Tensile rupture at any point along the length of the reinforcement

Loss of frictional bond (adherence) between the reinforcement and the soil fill

The maximum tensile force, TR, is calculated for each layer of reinforcement in the walls. This is

checked against the capacity of the reinforcement in that layer, which is based on the long-term

design strength of the geogrid, Tltds, and the available frictional force (adherence) that can be

generated between the geogrid and the fill to prevent pull-out.

This assessment can be carried out using a design sheet set up in the software package Mathcad.

The Mathcad sheet checks the internal stability of the system, (including compound and sliding

stability). The design method is in accordance with that described in BS 8006: 2010 Code of Practice

for Strengthened / reinforced soils and other fills.


Page 6

4 DESIGN SUMMARY

4.1 Properties

The design undertaken is based upon design parameters which have either been provided in the

information received from Colinwell or have been assumed by ourselves as being reasonable based

on the available information. A summary of the main properties used for design is given in Table 4.1

and Table 4.2. Further information can be found in the attached calculations in the Appendix.

Table 4.1: Structure Geometry Used for Design

Structure Type: Reinforced Soil Walls

Design Life: 60 Years

Wall Inclination Wall: <87°

Maximum Retained Height Wall: 3.5 m (not incl. 0.50 m Embedded)

Loading 10 kN/m2 (Live Load)

Table 4.2: Soil Properties Assumed for Design

Soil type Angle of Friction

(φ’) Cohesion

(c’) Dry Unit Weight ()

Reinforced Fill

(Class 6I or 6J) 35° 0 kN/m2 20 kN/m3

Free-Backfill Fill

(Class 6I or 6J) 35° 0 kN/m2 20 kN/m3

Granular Foundation 35° 0 kN/m2 20 kN/m3


Page 7

4.2 Reinforced Retaining Wall Design Suggestion

The walls have been considered at an angle of less than 87°. At the maximum height, the suggested

reinforcement layout consists of layers of Fortrac® 55T reinforcement, spaced at 0.4 m as the detail

below. Each reinforcement layer extends in to the reinforced fill by a ‘reinforcement length’ shown in

Table 4.3 below.

These reinforcement lengths have been determined due to the internal and composite stability of the

Wall.

Table 4.3: Reinforcement Requirements

Height Layers Spacing Reinforcement Reinforcement

Length

3.5m + 0.5m 1 – 10 0.4 m Fortrac® 55T 3.00 m

Illustration of typical retaining wall solution


Page 8

AB BLOCKS Colour Options – Pewter, Slate Blend, Limestone Blend, Abbey Blend, Cinder Blend,

Cotswold. Type - AB3 (3º) to form 3 degree batter.

Fortrac 55T is a uniaxial high-strength low-strain geogrids. It is typically provided in rolls of 5.0 x 200

m long.

Data sheets for both products can be found attached in the appendices. It is also important to note

that both reinforcement are truly flexible products. Once the required lengths are cut they can be

readily folded and transported to site.

All products produced by Huesker Synthetic GmbH are manufactured under our ISO 9001 quality

scheme supported by our ISO 14001 management systems.

The primary wall reinforcement (Fortrac® T) and Segmental block system (Allan Block®) are both

BBA certified products. Copies of which are attached in the appendices of this document.

A formal quotation for the supply of these materials can be provided by our UK head office:

E: [email protected]

T: 01925 62 93 93



Page 9

5 DISCLAIMER

Important Notice

This document contains an outline design suggestion issued by HUESKER Limited (“us”) to Colinwell

(“you”) in relation to the Geogrid Reinforced Walls and at Crossfield Street, Blackburn (“the Project”).

The purpose of this document is to assist you in deciding whether you wish to proceed with the

purchase of goods from us in the event that you are awarded the Project.

This document has been delivered to you at no charge for information only and on the express

understanding that you shall use it only for the purpose set out above. We give no undertaking to

provide you with access to any additional information or to update this document or any additional

information, or to correct any inaccuracies in it which may become apparent, and we reserve the

right, without giving reasons, at any time and in any respect, to amend or terminate the procedure

for the sale of goods or to terminate negotiations with any prospective purchaser of goods. The

issue of this document shall not be deemed to be any form of commitment on our part to proceed

with any transaction.

The information in this document, is illustrative and it is not a detailed design. It is specific to the

unique characteristics of our geosynthetic products referenced within the calculations. It does not

purport to be comprehensive and has not been independently verified. While this information has

been prepared in good faith, no representation or warranty, express or implied, is or will be made

and no responsibility or liability is or will be accepted by us or any of the companies in the same

group of companies as us, or by any of their respective officers, employees or agents in relation to

the accuracy or completeness of this document or any other written or oral information made

available to you or your advisers and any such liability is expressly disclaimed. This disclaimer shall

not exclude any liability for, or remedy in respect of, fraudulent misrepresentation.

No information set out or referred to in this document shall form the basis of any contract. Any

prospective purchaser of our goods shall be required to acknowledge in the agreement for the goods

that it has not relied on or been induced to enter into such an agreement by any representation or

warranty, save as expressly set out in such agreement.

No liability in negligence will arise from the construction of any project based on such information

contained in this document. Final determination of the suitability of any information or material for

the use contemplated and the manner of use is the sole responsibility of the user and its professional

advisers, who must assume all risk and liability in connection therewith. We assume no responsibility

to you or any third party for the whole or any part of the content of this document.

Copyright in this document belongs to us. It may not be reproduced in whole or in part without our

prior written permission. It must not be disclosed to any third party other than for the purpose of

evaluating its commercial application for the use of our geosynthetic products.

By accepting this document, you agree to be bound by the foregoing limitations.


Page 10

6 APPENDIX

6.1 Mathcad Calculations

6.2 Data Sheets:

6.3 BBA HAPAS Certificates:


Page 10

6 APPENDIX

6.1 Mathcad Calculations

6.2 Data Sheets:

6.3 BBA HAPAS Certificates:

Design of Reinforced Soil Structures to BS 8006According to BS 8006-1: 2010: Code of Practice for strengthened/ reinforcedsoils and other fills)

Project : Crossfield Street, Blackburn

Project No.: 362/1118

Huesker Engineers: I Scotland

Warrington, UK, November 2018

BS8006 Matchad v2.3 1 10:33: 28/11/2018

Contents

1.0 Characteristic Conditions

2.0 Initial Sizing

3.0 External Stability

4.0 Internal Stability

5.0 Connections

6.0 Design Summary

7.0 References

BS8006 Matchad v2.3 2 10:33: 28/11/2018

1.0 Characteristic Conditions

1.1 General (All caclulations in this sheet are considered in 2D, per m width of wall)

Structure Type: Type "Wall":= (Wall or Abutment)

Structure Category: Category 1:= (1, 2 or 3. See BS 8006, Fig 11, 12 and 13)

Intended Service Life: tserv 60yr:=

1.2 Geometry

Retained Height Hm 3.5m:= (Height above ground level)

Facing Inclination: β 87deg:= (Above 70 degrees, designed as vertical)

Slope of Ground at Toe: βs 0deg:=

Slope of Ground Above: αs 0deg:= (Stability of slope above structure, not checked in

this worksheet)Running Length of GRS: BGRS 20 m⋅:=

BS8006 Matchad v2.3 3 10:33: 28/11/2018

1.3 Loading

Distributed Dead Load: ws0 0kPa:=

Vertical Strip UDL: SL 0kN

m:= UDL

Width:

UDL Centre

from Face:b 5.5 m⋅:= d 7 m⋅:=

Horizontal Strip Load: FL 0kN

m:=

Distributed Live Load: Over Structure: ws1 10kPa:= Behind Structure: ws2 10kPa:=

Considered only for External Stability

1.4 Characteristic Soil Properties

Foundation (f) Reinforced Soil (1) Backfill (2)Soil Name:

Granular Class 6I / 6J Class 6I / 6J

Peak Angle of

Internal Friction:ϕf 35deg:= ϕ1 35deg:= ϕ2 35deg:=

Cohesion: cf 0kN

m2

:= c1 0kN

m2

:= c2 0kN

m2

:=

Unit Weight: γf 20kN

m3

:= γ1 20kN

m3

:= γ2 20kN

m3

:=

Average Particle Size: D50 2 mm⋅:=

pH of Soil: pH 6:=

Friction between Soil and

Back of Structure:δ1

2

3ϕ1⋅:= δ2

2

3ϕ2⋅:=

Active Earth Pressure

Coefficient:Earth Pressure according to EN 1997-1:2004+A1:2013, C.2.

Advanced (1) or Simple (0) methods for earth pressure? KMethod 0:=

Ka.1 Kq.1 KMethod 1=if

Ka.r.1 otherwise

:= Ka.2 Kq.2 KMethod 1=if

Ka.r.2 otherwise

:=

Active Earth Pressure Override:

Ka.1 := Ka.2 :=

Ka.1 0.27= Ka.2 0.27=

BS8006 Matchad v2.3 4 10:33: 28/11/2018

1.5 Partial Factors

1.5.1 Material Partial Factors ULS SLS

Friction Angle: (tanϕ): fms.ϕ 1.0:= fms.ϕ.SLS 1.0:=

Cohesion (c'): fms.c 1.6:= fms.c.SLS 1.0:=

Undrained

Shear Strength

(cu): fms.cu 1.0:= fms.cu.SLS 1.0:=

1.5.2 Loading Partial Factors As defined in Table 12 (walls) or 13 (abutments), in BS 8006(2010).

Combo A Combo B Combo C

Dead Load of Structure: ffs.1 1.5:= ffs.1.B 1.0:= ffs.1.C 1.0:=

Dead Load of Backfill on Structure ffs.2 1.5:= ffs.2.B 1.0:= ffs.2.C 1.0:=

Strip Load (Live) ff 1.5:= ff.B 0:= ff.C 1.0:=

Earth Pressure behind Structure: ffs.P.A 1.5:= ffs.P.B 1.5:= ffs.P.C 1.0:=

Traffic Load on Structure: fq.1 1.5:= fq.1.B 0:= fq.1.C 0:=

Traffic Load behind Structure: fq.2 1.5:= fq.2.B 1.5:= fq.2.C 0:=

1.5.3 Partial Safety Factors ULS SLS

Pull-Out Resistance: fp 1.3:= fp.SLS 1.0:=

Sliding Resistance: fs.r 1.3:= fs.r.SLS 1.0:=

Foundation Bearing Capacity: fms.q 1.35:=

Sliding along base of Structure: fs.s 1.2:=

As Category 1= , factor for ramifications:

(see 1.1)

fn 1.0= fn 1.0=

BS8006 Matchad v2.3 5 10:33: 28/11/2018

2.0 Initial Sizing

2.1 Proposed Facing System

2.1.1 Wrapped Reinforced Soil Wall

Product Name: B0 "Allan Block":=

Dimensions of Individual Unit Hb 0.2m:= , Lb 0.3m:= , Bb 0.46m:=

(Height, Length, Bredth respectively)

Block Angle, from horizontal: β 87 deg⋅= (From Section 1.2)

Mass per Block (incl.. Gravel Infill): Mb 33kg:=

Volume of void per Soil Block: Vv 0.017 m3

⋅:=

Unit weight of Block Infill: γbf 20kN

m3

:=

Total Weight of Block and Infill: Wt Mb g⋅ Vv γbf⋅+:= Wt 0.66 kN⋅=

Weight per m run of block: Wb

Wt

Bb

:= Wb 1.4kN

m⋅=

BS8006 Matchad v2.3 6 10:33: 28/11/2018

h0j

3.30

2.90

2.50

2.10

1.70

1.30

0.90

0.50

0.10

-0.30

m

=j

10

9

8

7

6

5

4

3

2

1

=h

j

0.20

0.60

1.00

1.40

1.80

2.20

2.60

3.00

3.40

3.80

m

=

2.2 Proposed Geometry

As βs 0.00 deg⋅= , Embedment should exceed Dm.frost 0.45m:= and Dm.H 0.18 m= ,

Chosen Embedment Depth : Dm 0.5m:= Embedment "OK"=

Therefore the total height of the structure is:

H Hm Dm+:= H 4.00 m=

Starting Reinforcement Level, from base of wall: hs0 0.2m:= Postive Number Only

(Check height of block iscompatible with Spacing:

Hb 0.20 m= )

Number and Spacing of upper Layers: n1 10:= Sv1 0.4 m⋅:=

Number and Spacing of lower Layers: n2 0:= Sv2 0.2 m⋅:=Spacing "OK"=

The number of layers of reinforcement in the structure is: n 10=

BS 8006 restricts the reinforcement length to at least 0.7 H⋅ 2.80 m= or 3m

Therefore the reinforcement length is chosen to be: L 3m:=

Layer

No.

Height Reinforcement

Spacing

L1j

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

m

= Svj

0.4

0.4

0.4

0.4

0.4

0.4

0.4

0.4

0.4

0.4

m

=

Soil Height

Above

Reinforcement

Length

BS8006 Matchad v2.3 7 10:33: 28/11/2018

2.3 Proposed Geosynthetic Reinforcement

Product Name 1: G0 "Fortrac 55T":= Fortrac T suitable when

4 < pH 6= < 9

Fortrac M suitable when

2 < pH 6= < 12

Product Name 2: G1 "Fortrac 80T":=

Product Name 3: G2 "Fortrac 110T":=

Interaction Coefficient:a 0.8:= (BBA certificate)

2.3.1 Ultimate Limit State (ULS)

In accordance with BS 8006:2010 and EN ISO 10319 (2008) and BBA certificates(2014):

G0 "Fortrac 55T"= G1 "Fortrac 80T"= G2 "Fortrac 110T"=

Characteristic axial tensile strength (EN ISO 10319):

Tchar.G0 55kN

m⋅= Tchar.G1 80

kN

m⋅= Tchar.G2 110

kN

m⋅=

Partial material factor for creep, for: tserv 60 yr⋅= and pH 6= :

RFCR.G0 1.5= RFCR.G1 1.5= RFCR.G2 1.5=

Partial factor for transport, mechanical and installation damage D50 2 mm⋅= :

RFID.G0 1.15= RFID.G1 1.15= RFID.G2 1.15=

Partial factor for weathering, When covered in 24 hours after installation :

RFW.G0 1.00= RFW.G1 1.00= RFW.G2 1.00=

Partial factor for chemical and environmental effects for service life time: tserv 60 yr⋅= :

RFCH.G0 1.03= RFCH.G1 1.03= RFCH.G2 1.03=

Partial factor for extrapolation of test data:

fe.G0 1.07= fe.G1 1.07= fe.G2 1.07=

Combined Material factor for Reinforcement: fm.G0 RFID.G0 RFW.G0⋅ RFCH.G0⋅ fe.G0⋅:=

fm.G0 1.27= fm.G1 1.27= fm.G2 1.27=

The available long-term design strength of the reinforcement:

TD.G0

Tchar.G0

RFCR.G0 fm.G0⋅:=


TD.G0 28.9kN

m⋅= TD.G1 42.1

kN

m⋅= TD.G2 57.9

kN

m⋅=

BS8006 Matchad v2.3 8 10:33: 28/11/2018

2.2.2 Serviceability Limit State (SLS)

Post-construction strain limit for Walls = PCSL 1.00 %⋅=

Characteristic Strain Limited Tensile Strength (using data from BBA Certificate):

TCS.G0 32.6kN

m⋅= TCS.G1 47.44

kN

m⋅= TCS.G2 65.23

kN

m⋅=

Strain Limited Design Strength: TD.SLS.G0

TCS.G0

RFW.G0 RFCH.G0⋅ fe.G0⋅:=


TD.SLS.G0 29.6kN

m⋅= TD.SLS.G1 43

kN

m⋅= TD.SLS.G2 59.2

kN

m⋅=

BS8006 Matchad v2.3 9 10:33: 28/11/2018

3.0 External Stability

3.1 Bearing and Tilt

Bearing not checked as based on Load transfer platform over VCCs

3.1.1 Bearing Pressure:

Max. Height: H 4 m=

Max. Height at Heel: HT H:= HT 4 m=

Slope Running Length: Lα 0 m⋅:=

Max Reinforcement Length: L 3.00 m=

Total Pressure Acting Behind Reinforced Soil Block:

PA Ka.2 ffs.P.A 0.5 HT( )2⋅⋅ γ2⋅

fq.2 ws2⋅ HT⋅( )+ ffs.2 ws0⋅ HT⋅( )+

⋅:=

PA 81.3kN

m⋅= PB 81.3

kN

m⋅=

Vertical Component of Earth Pressure:

Pv.A Ka.2 0.5⋅ HT( )2⋅ γ2⋅

sin δ2( )⋅:=

Pv.A 17.2kN

m⋅= Pv.B 17.2

kN

m⋅=

Horizontal Component of Earth Pressure (Factored):

PH.A PA cos δ2( )⋅:=RH.A PH.A:= RH.B PH.B:=

RH.A 74.6kN

m⋅= RH.B 74.6

kN

m⋅=

Factored Loading Components:

Rγ.A ffs.1 H⋅ L⋅ γ1⋅:=Rγ.A 360

kN

m⋅= Rγ.B 240

kN

m⋅=

Rα.A ffs.2γ2 HT H−( ) L Lα−( )⋅tan αs( ) Lα

2⋅

2+

⋅:=

Rα.A 0kN

m⋅= Rα.B 0

kN

m⋅=

Gd.A ffs.2 ws0⋅ L⋅:=Gd.A 0

kN

m⋅= Gd.B 0

kN

m⋅=

qd.A fq.1 ws1⋅ L⋅:=qd.A 45

kN

m⋅= qd.B 0

kN

m⋅=

Resultant Vertical Load Components:

Rv.A Rγ.A Rα.A+ Gd.A+ qd.A+ Pv.A+:=

Rv.A 422.2kN

m⋅= Rv.B 257.2

kN

m⋅=

BS8006 Matchad v2.3 10 10:33: 28/11/2018

3.1.2 Overturning

Restoring Moment about Toe:

Mv.A Rγ.A

L

2⋅

Rα.A

2Lα

3⋅

+ Gd.A

L

2⋅

+ qd.A

L

2⋅

+ Pv.A L⋅( )+:=

Mv.A 659.0kN m⋅

m⋅= Mv.B 411.5

kN m⋅

m⋅=

Disturbing moment about Toe:

MH.A Ka.2 ffs.P.A

HT

3

1

2⋅ HT( )2⋅⋅ γ2⋅

HT

2fq.1⋅ ws0⋅ HT⋅

+HT

2fq.2⋅ ws2⋅ HT⋅

+

⋅:=

MH.A 119.2kN m⋅

m⋅= MH.B 119.2

kN m⋅

m⋅=

MV must be greater than MH:

FOSOverturning.A

Mv.A

MH.A

:=

FOSOverturning.A 5.53= FOSOverturning.B 3.45=

Overturning "OK"=

(if overturning is not satisfied, try

increasing reinforcement length)3.1.3 Eccentricity Check

Eccentricity of vertical load, as a result of earth pressure:

eA

L

2

Mv.A MH.A−

Rv.A

−:=

eA 0.22 m= eB 0.36 m=

Eccentricity "OK"=e

A and e

B must be in middle third hence smaller than

L

60.5 m⋅= .

(if eccentricity is too high, try

increasing reinforcement length)

Effective Length:

BA L 2.eA−:=BA 2.56 m= BB 2.27 m=

Factored Bearing Pressure

(Meyerhof Distribution):

qr.A

Rv.A

BA

:=qr.A 165.09

kN

m2

⋅= qr.B 113.14kN

m2

⋅=

BS8006 Matchad v2.3 11 10:33: 28/11/2018

3.1.4 Bearing Capacity:

Bearing Capacity Factors of Foundation Soil (after EN 1997, annex D) when ϕf 35 °⋅= .

(Assuming drained conditions, vertical loading and level foundation)

Nq eπ tan ϕf( )⋅( )

tan 45degϕf

2+

2

⋅:= Nq 33.3=

Nc Nq 1−( )cot ϕf( ):= Nc 46.12=

Nγ 1.5 Nq 1−( ) tan ϕf( )⋅:= (after Brinch Hanson 1963) Nγ 33.92=

sq 1L

BGRS

sin ϕf( )⋅+:= sq 1.09=

sc 1 0.3L

BGRS

−:= sc 0.95=

sγ

sq Nq⋅ 1−

Nq 1−:= sγ 1.09=

Design Bearing Resitance of Foundation Soil:

qult.A cf Nc⋅ sc⋅ γf Dm⋅ Nq⋅ sc+1

2γf⋅ BA⋅ Nγ⋅ sγ+:=

qult.A 1262kN

m2

⋅= qult.B 1157kN

m2

⋅=

3.1.5 Bearing Capacity Check

Bearing capacity > Bearing Pressure by fms.q 1.35=

FOSBearing.A

qult.A

fms.q qr.A⋅:=

FOSBearing.A 5.66= FOSBearing.B 7.58=

Therefore Bearing "OK"=

3.2 Forward Sliding

3.2.1 Sliding along the base: ϕf 35 deg⋅=The resistance at the base of the structure:

RB.A Rv.A

tan ϕf( )fms.ϕ

⋅cf

fms.c

+:=

RB.A 295.61kN

m⋅= RB.B 180.07

kN

m⋅=

Is greater than, the pressure from the behind the structure:

Fs.A RH.A:=

Fs.A 74.65kN

m⋅= Fs.B 74.65

kN

m⋅=

FOS for sliding, including fs.s 1.2=

FOSExSlid.A

RB.A

fs.s Fs.A⋅:=

FOSExSlid.A 3.3= FOSExSlid.B 2.01= FOS must be > 1.0,

Sliding "OK"=

BS8006 Matchad v2.3 12 10:33: 28/11/2018

4.0 Internal Stability

4.1 Individual Reinforcement Stress (Tie-Back Wedge Method)

4.1.1 Tie Back Geometry

Active Zone Length: Laj

H hj

−( ) tan 45.degϕ1

2−

⋅:=

Resistant Zone Length: Lej

L Laj

−:=

Strip Load SL distribution through Reinforced Fill: Dj

Strip Load SL distribution acting in Resistant zone: LS.ej

Horizontal FL Load distribution at face: σHj, zs

j

σH.max 0kN

m2

⋅= Acting at the face over: zs 15.93 m=

Resultant Factored Vertical Load acting on jth layer:

Rvj.Aj

ffs.1 hj

⋅ L⋅ γ1⋅( ) fq.1 ws1⋅ L⋅( )+ ffs.2 ws0⋅ L⋅( )+ ffs.2 0.5⋅ tan αs( ) L2

⋅ γ2⋅

+:=

Disturbing moment about jth Layer:

MHj.Aj

Ka.2 ffs.P.A

hj

3⋅

1

2⋅ h

jtan αs( ) L+( )2⋅ γ2⋅

hj

2fq.2⋅ ws2⋅ h

j⋅

+h

j

2ws0⋅ h

j⋅

+

⋅:=

Eccentricity of Resultant Vertical Load at jth layer:

ej.Aj

MHj.Aj

Rvj.Aj

:=

Resultant Factored Vertical Stress acting on jth layer (With Meyerhof Distribution):

σv.Aj

Rvj.Aj

L 2 ej.Aj

−:=

BS8006 Matchad v2.3 13 10:33: 28/11/2018

4.1.2 Local Stability Check:

Maximum Tensile Force in jth Layer:

Tensile Force component according to self-weight and vertical loading:

Tp.Aj

Ka.1 σv.Aj

⋅ Svj

⋅:=

Tensile Force due to Vertical Strip Loading:

Ts.Aj

Ka.1 Svj

⋅ff SL⋅

Dj

⋅:=

Tensile Force due to Horizontal Shear Laoding:

Tf.Aj

0 hj

zs≥if

2 Svj

⋅ ff⋅ σH.max⋅ 1

hj

zs

−

⋅

otherwise

:=

Required Tensile Force:

Tj

fn Tp.Aj

Ts.Aj

+ Tf.Aj

+( ):=

Adherence Capacity:

The total horizontal width of the top and

bottom faces of reinforcement (Perimeter):P 2:=

Interaction Coefficient applied to tan(ϕ)

(Section 2.1):a 0.8=

Coefficient of Friction between

Soil and Geosynthetic:μ

a tan ϕ1( )⋅

fms.ϕ

:= μ 0.56=

Available Adherence Capacity:

Ta.Localj

P μ⋅ Lej

ffs.1 γ1⋅ hj

⋅ ffs.2 ws0⋅+ ffs.2 0.5⋅ tan αs( ) L⋅ γ2⋅+( )fp fn⋅

LS.ej

ff⋅SL

Dj

⋅+

⋅:=

BS8006 Matchad v2.3 14 10:33: 28/11/2018

Local Rupture Check:

Tj

2.3

3.6

5

6.4

7.8

9.4

11.1

12.9

14.8

17

kN

m⋅

= TBj

0.4

1.3

2.3

3.2

4.3

5.4

6.7

8.2

9.8

11.8

kN

m⋅

= TDj

28.9

28.9

28.9

28.9

28.9

28.9

28.9

28.9

28.9

28.9

kN

m⋅

=Geogrid

j

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

= Rupturej

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

Minimum Factor of Safety: Combo A: FOSRupture.A 1.70= in layer: jRupture.A 1=

Combo B: FOSRupture.B 2.45= in layer: jRupture.B 1=

Rupture

Strength

Required

Tension

BS8006 Matchad v2.3 15 10:33: 28/11/2018

Local Adherence Check

Combo B

Tj

2.3

3.6

5.0

6.4

7.8

9.4

11.1

12.9

14.8

17.0

kN

m⋅

= Ta.Localj

5.3

19.1

37.2

59.6

86.3

117.3

152.7

192.3

236.3

284.5

kN

m⋅

= TBj

0.4

1.3

2.3

3.2

4.3

5.4

6.7

8.2

9.8

11.8

kN

m⋅

= Ta.Local.Bj

3.5

12.7

24.8

39.7

57.5

78.2

101.8

128.2

157.5

189.7

kN

m⋅

=Adherence

j

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

Minimum Factor of Safety: Combo A: FOSAdherence.A 2.32= in layer: jAdherence.A 10=

Combo B: FOSAdherence.B 8.08= in layer: jAdherence.B 10=

Combo A

BS8006 Matchad v2.3 16 10:33: 28/11/2018

4.2 Wedge Stability Check

4.2.1 Internal Critical Wedge Analysis:

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 900

20

40

60

80

Tii

kN

m

βii

deg

Worst Case Wedge Angle, β.max: Tmax 81.3kN

m⋅= at βmax 28 deg⋅=

βA βmax:= θA 90.deg βA−:= θA 62 deg⋅=

Number of Reinforcement Layers in Wedge: Nj

n 1+( ) j−:=

Area of Active Wedge: Aaj

0.5 hj( )2⋅ tan βA( )⋅:=

Vertical Disturbing Force

(Weight of Wedge plus Dead and Live Loads):

Wj

ffs.1 Aaj

⋅ γ1⋅( ) ffs.2 ws0 0.5 hj

⋅ tan βA( )⋅ tan αs( )⋅ γ1⋅+( )⋅ fq.1 ws1⋅+ ffs.2 0.5⋅ tan αs( ) hj

⋅ γ2⋅+ hj

⋅ tan βA( )⋅+:=

Vertical Force (not including Live Loading):

WRj

Wj

fq.1 ws1⋅ hj

⋅ tan βA( )⋅− ff SL.Wj

⋅+:=

Area of Resistance:Ar

jh

jL⋅( ) 0.5 h

j( )2⋅ tan βA( )⋅

− θA atan

hj

L

>if

0.5 L( )2

⋅ tan θA( )⋅

otherwise

:=

Total Tension Required to Stabilise Wedge:TT

jW

jff SL.W

j⋅+( ) tan θA

ϕ1

fms.ϕ

−

⋅ ff FL.Wj

⋅+:=

Tensile Resistance Available:TD.Wedge

j

j

n

j

TDj∑

=

fn

:=

Sum of Adherence Provided:

TAd.Wedgej

P μ⋅

Arj

Sv1

γ1 hj

⋅ ffs.2 ws0⋅+( )⋅

fp fn⋅⋅:=

BS8006 Matchad v2.3 17 10:33: 28/11/2018

Wedge Tensile Resistance Check:

Combo A Combo B

TTj

1.0

3.9

8.1

13.7

20.5

28.6

38.0

48.8

60.8

74.1

kN

m⋅

= TT.Bj

0.1

1

2.7

5.3

8.8

13.1

18.3

24.4

31.3

39.1

kN

m⋅

= TD.Wedgej

28.9

57.9

86.8

115.7

144.7

173.6

202.5

231.4

260.4

289.3

kN

m⋅

=WedRup

j

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

Minimum Factor of Safety: Combo A: FOSWed.Rup.A 3.90= in layer: jWed.Rup.A 1=

Combo B: FOSWed.Rup.B 7.4= in layer: jWed.Rup.B 1=

Sum of

Tensile

Resistance

BS8006 Matchad v2.3 18 10:33: 28/11/2018

Wedge Adherence Check:

Combo A

Sum of

Adherence

Sum of

Adherence

TTj

1.0

3.9

8.1

13.7

20.5

28.6

38.0

48.8

60.8

74.1

kN

m⋅

= TAd.Wedgej

5

44

118

222

352

504

673

854

1044

1238

kN

m⋅

= TT.Bj

0.1

1.0

2.7

5.3

8.8

13.1

18.3

24.4

31.3

39.1

kN

m⋅

= TAd.Wedge.Bj

5

44

118

222

352

504

673

854

1044

1238

kN

m⋅

=WedAd

j

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

Minimum Factor of Safety: Combo A: FOSWed.Ad.A 5.21= in layer: jWed.Ad.A 10=

Combo B: FOSWed.Ad.B 31.65= in layer: jWed.Ad.B 1=

Combo B

BS8006 Matchad v2.3 19 10:33: 28/11/2018

4.3 Serviceability Check (Combination C)

4.3.1 Individual Reinforcement Stress (Tie-Back Wedge Method)

Resultant Factored Vertical Load acting on jth layer (Dead Loads Only):

Rvj.SLSj

ffs.1.C hj

⋅ L⋅ γ1⋅( ) ffs.2.C ws0⋅ L⋅( )+ ffs.2.C 0.5⋅ tan αs( ) L2

⋅ γ2⋅

+:=

Disturbing moment about jth Layer:

MHj.SLSj

ffs.P.C Ka.2⋅h

j

3

1

2⋅ h

jtan αs( ) L+( )2⋅ γ2⋅

hj

2ws0⋅ h

j⋅

+

⋅:=

Eccentricity of Resultant Vertical Load at jth layer:

ej.SLSj

MHj.SLSj

Rvj.SLSj

:=

Resultant Factored Vertical Stress acting on jth layer (With Meyerhof Distribution):

σv.SLSj

Rvj.SLSj

L 2 ej.SLSj

−:=

Self-Weight and Uniform Load: Tp.SLSj

Ka.1 σv.SLSj

⋅ Svj

⋅:=

Strip Load: Ts.SLSj

Ka.1 Svj

⋅ff.C SL⋅

Dj

⋅:=

Horizontal Load: Tf.SLSj

0 hj

zs≥if

2 Svj

⋅ ff.C⋅ σH.max⋅ 1

hj

zs

−

⋅

otherwise

:=

Required Tensile Force: TSLSj

Tp.SLSj

Ts.SLSj

+ Tf.SLSj

+:=

4.3.1 Strain Limited Tensile Design Resistance

As defined in Section 2.2.2:

As the Post-Construction Strain Limit = PCSL 1 %⋅=Strain-limtied Reinforcement Strength:

For: G0 "Fortrac 55T"= G1 "Fortrac 80T"= G2 "Fortrac 110T"=

TD.SLS.G0 29.59kN

m⋅= TD.SLS.G1 43.05

kN

m⋅= TD.SLS.G2 59.19

kN

m⋅=

BS8006 Matchad v2.3 20 10:33: 28/11/2018

TSLSj

0.4

1.3

2.2

3.1

4.0

5.0

6.0

7.1

8.3

9.6

kN

m⋅

= TD.SLSj

29.6

29.6

29.6

29.6

29.6

29.6

29.6

29.6

29.6

29.6

kN

m⋅

=

4.3.2 SLS Local Reinforcement Strength and Adherence Check:

Required

Tensile Force

Strain Limited

Tensile Capacity

σv.SLSj

4.0

12.0

20.2

28.6

37.2

46.2

55.8

66.0

76.9

88.9

kN

m2

⋅

=h

j

0.2

0.6

1.0

1.4

1.8

2.2

2.6

3.0

3.4

3.8

m⋅

= SLSj

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

<

Minimum Factor of Safety: FOSSLS 3.07= in layer: jSLS 1=

BS8006 Matchad v2.3 21 10:33: 28/11/2018

5.0 Connections

Facings are designed according to the highest tensile loads resulting from Internal or compo

design.

Facing Type: B0 "Allan Block"=

β 87 deg⋅=Facing Inclination:

5.1 Connection Strength Between Reinforcement and Allan

Block (Frictional)

Weight per m row of blocks: Wb 1.44kN

m⋅= (See section 2.3)

Vertical Pressure of blocks above the jth layer: σbj

Wb

hj

Hb

⋅:=

Use Connection Data from: ConnData "NCMA":=

Positive Connection?: Conn3 "No":= ("Yes" or "No")

Connection Data taken from NCMA Test Data or BBA Certificate 13/H203. BBA is the default.

Design Connection Strength, per layer:: TD.connj

Tconnj

RFWj

RFCHj

⋅ fej

⋅ fn⋅:=

0 6 12 18 24 300

2

4

6

8

Available Connection Strength (kN)

Lay

er N

um

ber

j

TD.connj

kN

m

BS8006 Matchad v2.3 22 10:33: 28/11/2018

Combo A Combo B

Tj

2.3

3.6

5.0

6.4

7.8

9.4

11.1

12.9

14.8

17.0

kN

m⋅

= TBj

0.4

1.3

2.3

3.2

4.3

5.4

6.7

8.2

9.8

11.8

kN

m⋅

= TD.connj

23.4

23.6

23.8

24.1

24.3

24.5

24.8

25

25.2

25.5

kN

m⋅

=Geogrid

j

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

= Connectionj

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

= <

Minimum Factor of Safety: Combo A: FOSconn.A 1.50= in layer: jconn.A 1=

Combo B: FOSconn.B 2.15= in layer: jconn.B 1=

BS8006 Matchad v2.3 23 10:33: 28/11/2018

6.0 Design Summary

External Stability:

Bearing and Tilt (3.1): Bearing "OK"= External Forward Sliding (3.2): Sliding "OK"=

Internal Stability:

Layer Height Length

h0j

3.30

2.90

2.50

2.10

1.70

1.30

0.90

0.50

0.10

-0.30

m

= Geogridj

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

"Fortrac 55T"

= L1j

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

3.00

m

= Localj

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

= Wedgej

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

= SLSj

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

= Connectionj

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

"OK"

=j

10

9

8

7

6

5

4

3

2

1

=

BS8006 Matchad v2.3 24 10:33: 28/11/2018

HUESKER Synthetic GmbH Fabrikstraße 13-15, D -48712 Gescher Tel.: + 49 (0) 25 42 / 701 – 0 Fax: + 49 (0) 25 42 / 701 – 499 E – Mail: [email protected] Internet: www.HUESKER.com Fortrac® is a registered trademark by HUESKER Synthetic GmbH

No responsibility is accepted for any change in product properties due to environmental influences and / or improper application or handling. Rights are reserved to modify the product to effect improvements. Issue: 06/2015 Rev. A

Product Description

1. Product Name Fortrac® 55 T

2. Product Description Flexible and highly resistant geogrid with protective polymer coating

3. Raw Materials used Raw Material: MD / CMD PET

Type of Coating: Polymer

4. Environmental Aspect non-hazardous

Technical data

01. Mass per unit area g/m2 240 (DIN EN ISO 9864)

02. Aperture Size (approx.) mm 25 x 25

03. Nominal Tensile Strength MD kN/m 55 (DIN EN ISO 10319) CMD kN/m ≥ 20

04. Strain at Nominal Tensile Strength MD % 10 (DIN EN ISO 10319) CMD % ≤ 10

05. Standard Roll Dimensions (width x length) m x m 5,00 x 200

06. Durability Predicted to be durable for (acc. to EN 13249: 2015 ff.) Minimum 100 years in natural soils with 4 pH 9 and soil temperatures 25 °C


http://www.huesker.com/

Page 1 of 12

TECHNICAL APPROVALS FOR CONSTRUCTION

APPROVAL

INSPECTION

TESTING

CERTIFICATION

H A P A S

HUESKER Synthetic GmbHFabrikstrasse 13–15 D-48712 Gescher GermanyTel: 00 49 2542 701 -0 Fax: 00 49 2542 701 -499e-mail: [email protected]: www.HUESKER.com

HAPAS Certificate13/H197

Product Sheet 3

British Board of Agrément tel: 01923 665300Bucknalls Lane fax: 01923 665301Watford e-mail: [email protected] WD25 9BA website: www.bbacerts.co.uk©2014

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 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.

FORTRAC GEOSYNTHETICS

FORTRAC T AND R-T GEOGRIDS

This Certificate relates to Fortrac T and R-T Geogrids, polymeric geogrids consisting of polyester fibres coated with a black styrene butadiene polymer for use as reinforcement in embankments with slope angles up to 70°.

CERTIFICATION INCLUDES:• factors relating to compliance with HAPAS

requirements• 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 five-yearly review.

KEY FACTORS ASSESSED

Soil/geogrid interaction — interaction between the soil and geogrids has been considered and coefficients relating to direct sliding and pull-out resistance proposed (see section 6).

Mechanical properties — short- and long-term tensile strength and elongation properties of the geogrids and loss of strength due to installation damage have been assessed and reduction factors established for use in design (see section 7).

Durability — the resistance of the geogrids to the effects of hydrolysis, chemical and biological degredation, UV exposure and temperature conditions normally encountered in civil engineering practice have been assessed and reduction factors established for use in design (see sections 8 and 11).

This HAPAS Certificate Product Sheet(1) is issued by the British Board of Agrément (BBA), supported by the Highways Agency (HA) (acting on behalf of the Overseeing Organisations of the Department for Transport; Transport Scotland; the Welsh Assembly Government and the Department for Regional Development, Northern Ireland), the Association of Directors of Environment, Economy, Planning and Transport (ADEPT), the Local Government Technical Advisers Group and industry bodies. HAPAS Certificates are normally each subject to a review every five years. (1) Hereinafter referred to as ‘Certificate’.

The BBA has awarded this 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 Second issue: 5 September 2014 Brian Chamberlain Claire Curtis-Thomas

Head of Approvals — Engineering Chief Executive

Page 2 of 12

In the opinion of the BBA, Fortrac T and R-T Geogrids when used in accordance with the provisions of this Certificate, will meet the requirements of the Highways Agency and local Highway Authorities for the design and construction of reinforced soil embankments with slope angles up to 70°.

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: 1 Description (1.2), 3 Delivery and site handling (3.1, 3.4 and 3.5) and the Installation part of this Certificate.

Additional Information

CE markingThe Certificate holder has taken the responsibility of CE marking the products in accordance with harmonised European Standard BS EN 13251 : 2001. An asterisk (*) appearing in this Certificate indicates that data shown is given in the manufacturer’s Declaration of Performance.

Technical Specification

1 Description1.1 Fortrac T and R-T Geogrids are planar structures consisting of a regular open network of woven, integrally-connected tensile elements of yarn. The yarn is made from high modulus polyester fibres of polyethylene terephthalate (PET). The woven grid is coated with a protective layer of black styrene butadiene polymer.

1.2 The geogrids are manufactured in sixteen standard grades of various strengths and mesh sizes. A typical geogrid is illustrated in Figure 1 and the range and specification of the geogrids assessed by the BBA are listed in Tables 1 and 2.

1.3 The warp (machine) direction is along the roll length and is indicated by a paper tape (see Figure 1).

Figure 1 Fortrac T and R-T Geogrids

Requirements

Page 3 of 12

Table 1 General specification

Grade(1) Nominal mass(2)

(g·m–2)Average grid size(3)

warp/weft(mm)A x B

Average aperture size(3)

warp/weft(mm)C x D

Colour code(4)

Nominal roll weight for standard

5 m width rolls

Standard roll length

(m)

35T 185 29.0 x 30.0 26.0 x 24.0 Red 190 200

55T 240 29.0 x 30.0 25.0 x 24.0 Green 250 200

65T 280 29.0 x 30.0 25.0 x 23.0 Orange 290 200

80T 320 29.0 x 30.0 25.0 x 23.0 Pink 330 200

110T 350 29.0 x 30.0 24.0 x 23.0 White 360 200

150T 440 29.0 x 30.0 23.0 x 23.0 No colour 450 200

200T 530 30.0 x 30.0 23.0 x 23.0 No colour 540 200

35/20-20T 210 23.1 x 23.0 21.0 x 18.0 Red 230 200

55/30-20T 280 23.0 x 25.5 20.0 x 20.5 Green 300 200

80/30-20T 350 25.0 x 23.0 20.0 x 18.0 Pink 370 200

110/30-20T 420 25.1 x 22.8 20.0 x 18.0 White 480 200

R150/30-30T 520 41.7 x 32.8 33.0 x 27.0 No colour 630 200

R200/30-30T 630 40.0 x 32.5 31.0 x 27.0 No colour 750 200

R400/50-30T 1200 67.0 x 33.5 37.0 x 27.5 No colour 650 100

R600/50-30T 1650 50.0 x 33.0 30.0 x 28.0 No colour 900 100

R800-100-30T 2400 90.0 x 30.0 30.0 x 25.0 No colour 1250 100

(1) R denotes the goegrid is knitted.(2) Mass/unit area measured in accordance with BS EN ISO 9864 : 2005.(3) Reference dimensions (see Figure 1).(4) In accordance with BS EN ISO 10320 : 1999

Table 2 Performance characteristics

Grade Machine Direction (MD) Cross Machine Direction (CMD)

Short term tensile strength(1)

kN·m–1Strain at maximum tensile strength(1)

(%) (*)

Short term tensile strength(1) kN·m–1

Strain at maximum tensile strength(1)

(%) (*)Mean value

(*)Tolerance

(*)Tchar Mean value

(*)Tolerance

(*)Tchar

35T 35 –0 35 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

55T 55 –0 55 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

65T 65 –0 65 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

80T 80 –0 80 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

110T 110 –0 110 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

150T 150 –0 150 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

200T 200 –0 200 9.5 (±1.5) 20 –0 20 9.5 (±1.5)

35/20-20T 35 –0 35 10 (+0/–3) 20 –0 20 10 (+0/–3)

55/30-20T 55 –0 55 10 (+0/–3) 30 –0 30 10 (+0/–3)

80/30-20T 80 –0 80 11 (+0/–3) 30 –0 30 11 (+0/–3)

110/30-20T 110 –0 110 11 (+0/–3) 30 –0 30 10 (+0/–3)

R150/30-30T 150 –0 150 11 (+0/–3) 30 –0 30 11 (+0/–3)

R200/30-30T 200 –0 200 10 (+0/–3) 30 –0 30 10 (+0/–3)

R400/50-30T 400 –0 400 10 (+0/–3) 50 –0 50 10 (+0/–3)

R600/50-30T 600 –0 600 10 (+0/–3) 50 –0 50 10 (+0/–3)

R800-100-30T 800 –0 800 10 (+0/–3) 100 –0 100 10 (+0/–3)

(1) Tests in accordance with BS EN ISO 10319 : 2008, the values given are the mean and tolerance values in accordance with BS EN 13251 : 2001.

2 Manufacture2.1 Fortrac T and R-T Geogrids are manufactured from yarn woven or knitted into grids and coated with a protective layer of black styrene butadiene polymer.

2.2 As part of the assessment and ongoing surveillance of product quality, the BBA has:• agreed with the manufacturer the quality control procedures and product testing to be undertaken• assessed and agreed the quality control operated over batches of incoming materials

Page 4 of 12

• monitored the production process and verified that it is in accordance with the documented process• evaluated the process for management of nonconformities• checked that equipment has been properly tested and calibrated• undertaken to carry out the above measures on a regular basis through a surveillance process, to verify that the

specifications and quality control operated by the manufacturer are being maintained.

2.3 The management system of Huesker Synthetic GmbH has been assessed and registered as meeting the requirements of BS EN ISO 9001 : 2008 by TÜV NORD CERT GmbH, Germany (Certificate 04 100 970084).

3 Delivery and site handling3.1 The rolls of geogrid are delivered to site stacked and strapped to timber pallets. The rolls are 5.0 metres wide and between 0.5 m to 0.9 m diameter dependent on the product grade and roll length (see Table 1).

3.2 Each roll is wrapped for transit and site protection in black polythene film and is labelled with the geogrid grade and identification (see Figure 2).

Figure 2 Label

3.3 The ends of the rolls are sprayed with colour-coded paint to assist identification of a particular grade of geogrid on site (Table 1) in accordance with BS EN ISO 10320 : 1999.

3.4 Rolls should be stored in clean, dry conditions and protected from mechanical or chemical damage, exposure to direct sunlight and extreme temperatures. When laid horizontally, the rolls may be stacked up to five high. No other loads should be stored on top of the stack. The packaging should not be removed until immediately prior to installation.

3.5 Toxic fumes are given off if the geogrids catch fire and therefore the necessary precautions should be taken following the instructions of the material safety data sheet for the product.

Assessment and Technical Investigations

The following is a summary of the assessment and technical investigations carried out on Fortrac T and R-T Geogrids.

Design Considerations

4 General4.1 When designed and installed in accordance with this Certificate, Fortrac T and R-T Geogrids are satisfactory for the reinforcement of soil embankments with maximum slope angles of 70°.

4.2 Structural stability is achieved through the frictional interaction of soil particles and the geogrids and the tensile strength of the geogrids.

4.3 The fill specification and method of placement and compaction, design strength of the reinforcement and length of reinforcement embedded within the compacted fill are the key design factors.

4.4 Prior to the commencement of work, the designer must satisfy the design approval and certification procedures of the relevant Highway Authority.

4.5 Particular attention should be paid in design to the following issues:• site preparation and embankment construction• fill material properties

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• drainage• protection of the product against damage from site traffic and installation equipment• the stability of existing structures in close proximity• design of the embankment facing.

4.6 The working drawings should show the correct orientation of the geogrids. Each layer of reinforcement must be continuous in the direction of load, ie without overlaps.

5 Practicability of installationThe products are designed to be installed by trained contractors in accordance with the specifications and construction drawings (see the Installation part of this Certificate).

Design methodology

6.1 Reinforced soil embankments constructed using Fortrac T and R-T Geogrids should be designed in accordance with BS 8006-1 : 2010 and the Specification for Highway Works.

6.2 The typical service life given in Table 7 of BS 8006-1 : 2010 for reinforced soil embankments is 60 years.

Geogrid reinforcement6.3 In accordance with the methodology set out in BS 8006-1 : 2010, Annex 3, the design strength of the reinforcement (TD) is calculated as:

TD = TCR/fmwhere:TCR is the long-term tensile creep rupture strength of the reinforcement at the specified design life and design

temperature.

fm is the material safety factor to allow for the strength reducing effects of installation damage, weathering (including exposure to sunlight), chemical and other environmental effects and to allow for the extrapolation of data required to establish the above reduction factors.

6.4 The long-term tensile creep rupture strength (TCR ) for each grade of geogrid is calculated using the formula:

TCR = Tchar/RFCR

where:Tchar is the characteristic short-term strength of the geogrid taken from Table 2.

RFCR is the reduction factor for creep (see Section 7).

6.5 The material safety factor (fm) is calculated as:

fm = RFID x RFW x RFCH x fSwhere:RFID is the reduction factor for installation damage.

RFW is the reduction factor for weathering, including exposure to ultra violet light.

RFCH is the reduction factor for chemical/environmental effects.

fS is the factor of safety for the extrapolation of data.

6.6 Recommended values for RFCR, RFID, RFW, RFCH and fS, are given in sections 7, 8 and 9 of this Certificate. Conditions of use outside the scope for which the reduction factors are defined are not covered by this Certificate and advice should be sought from the Certificate holder.

Soil/geogrid interaction6.7 There are two limiting modes of interaction between the soil and the reinforcement that need to be considered and for which the length of reinforcement necessary to maintain equilibrium needs to be determined:• direct sliding — in which the soil slides over the layer of reinforcement• pullout — in which the layer of reinforcement pulls out of the soil after it has mobilised the maximum available

bond stress.

6.8 In CIRIA SP123, 1996, sections 4.5 and 4.6 describe the following methods for determining resistance to direct sliding and maximum available bond, to which the appropriate partial factors should be applied in accordance with BS 8006-1 : 2010.

6.9 The theoretical expression for resistance to direct sliding is:

fds x tan ’where:fds is the direct sliding coefficient.

’ is the effective angle of friction of soil.

Page 6 of 12

6.10 The direct sliding coefficient (fds) is calculated as:

fds = αs x (tan d/tan ’) + (1 – αs)

where:αs is the proportion of plane sliding area that is solid.

d is the angle of skin friction soil on planar reinforcement surface.

tan d/tan ’ is the coefficient of skin friction between the soil and geogrid material.

6.11 For initial design purposes, the coefficient of skin friction (tan d/tan ’) for determining the resistance to direct sliding for the product when buried in compacted frictional fill may be conservatively assumed to be 0.6. Values for the proportion of plane sliding area that is solid (αs) are given in Table 3.

Table 3 Soil geogrid interaction parameters for T and R-T Fortrac Geogrids

Grade as(1) Ratio of bearing(2) surface to plan area αb x B/2S

35T 0.28 0.009

55T 0.31 0.009

65T 0.34 0.009

80T 0.34 0.009

110T 0.37 0.008

150T 0.39 0.008

200T 0.41 0.008

35/20-20T 0.29 0.014

55/30-20T 0.30 0.014

80/30-20T 0.37 0.017

110/30-20T 0.37 0.016

R150/30-30T 0.35 0.014

R200/30-30T 0.36 0.016

R400/50-30T 0.55 0.013

R600/50-30T 0.49 0.015

R800-100-30T 0.72 0.017

(1) αs is the proportion of the plane sliding area that is solid and is required for the calculation of the bond coefficient (fb) and the direct sliding coefficient (fds) (see sections 6.10 and 6.13).

(2) The ratio is required to calculate the bond coefficient in accordance with CIRIA SP123 : 1996 (see section 6.13): αb is the proportion of the grid width available for bearingB is the thickness of a transverse member of a grid taking bearingS is the spacing between transverse members taking bearing.

6.12 For detailed design, the resistance to direct sliding should be determined from soil and geogrid specific shear box testing.

6.13 The theoretical expression for maximum available bond stress is:

fb x tan ’

where:fb is the bond coefficient.


6.14 The bond coefficient may be calculated as:

fb = αs x (tan d/tan ’) + (σ’b/σ’n) x (αb x B/2S) x (1/tan ’)

where:αs is the proportion of plane sliding area that is solid.


tan d/tan ’ is the coefficient of skin friction between the soil and geogrid material.

σ’b/σ’n is the bearing stress ratio.

αb x B/2S is the ratio of bearing surface to plan area.

d is the angle of skin friction, soil on planar reinforcement surfaceσ’b is the effective bearing stress on the reinforcementσ’n is the nominal effective stress

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6.15 For initial design purposes the coefficient of skin friction (tan d/tan ’) for determining the bond coefficient for the product when buried in frictional fill may be conservatively assumed to be 0.6. Values for the ratio of bearing surface to plan area (αb x B /2S) are given in Table 3. Typical values for the bearing stress ratio (σ’b/σ’n) are given in CIRIA SP123, 1996, Table 4.1.

6.16 The BBA recommends that site-specific pull-out tests are carried out to confirm the value of bond coefficient (fb) used in the final design.

Fill material

6.17 The designer should specify the relevant properties of fill material deemed acceptable for the purpose of the design. Acceptable materials should meet the requirements of BS 8006-1 : 2010. and the Highways Agency’s Specification for Highway Works.

Facings

6.18 A typical wrap around facing detail formed using the geogrid is shown in Figure 3. Where the geogrids are used to form the facing, natural or artificial protection must be provided to the grids and fill material to protect the products against damage from ultraviolet light (UV), fire and vandalism, and to protect the fill material from erosion.

Figure 3 Facings

6.19 Other types of facing including preformed panels, gabions/gabion sacks and other proprietary systems may be used, but are outside the scope of this Certificate. Further guidance is given in BS 8006-1 : 2010.

7 Mechanical propertiesTensile strength — short-term

7.1 Characteristic short-term tensile strength (Tchar) and strain at maximum strength for the product range are given in Table 2.

Tensile strength — long-term

7.2 The long-term creep performance of the geogrids has been determined in accordance with the principles of PD ISO/TR 20432 : 2007 using conventional and stepped isothermal method (SIM) creep rupture test data. The resultant creep rupture diagram is shown in Figure 4.

7.3 For a 60-year design life and design temperature of 20°C, the long-term tensile strength (TCR) of Fortrac T and R-T Geogrids is 66.8% of the characteristic short-term tensile strength (Tchar), giving a long-term creep reduction factor (RFCR) of 1.50.

7.4 For a 120-year design life and design temperature of 20°C, the long-term tensile strength (TCR) of Fortrac T and R-T Geogrids is 66.0% of characteristic short-term tensile strength (Tchar) giving a long-term creep reduction factor (RFCR) of 1.52.

Installation damage

7.5 To allow for loss of strength due to mechanical damage that may be sustained during installation, the appropriate value for RFID should be selected from Table 4. These reduction factors have been established from full-scale installation damage tests using a range of materials whose gradings can be seen in Figure 5. For fills not covered by Table 4, appropriate values of RFID may be determined from site-specific trials or the engineer may exercise engineering judgment to interpolate between the values given.

Page 8 of 12

Figure 4 Creep rupture diagram — Regression line for the expectancy at constant stress defined by % of characteristic short-term strength at 20°C

0.001 0.01 0.1 1 10 60years

100 1000time (years)

90.00

85.00

80.00

75.00

70.00

65.00

60.00

55.00

50.00

tens

ile s

treng

th (%

of s

hort-

term

cha

ract

eristic

tens

ile s

treng

th)

Figure 5 Particle size distributions of fills used in installation damage testing

per

cent

age

pass

ing (%

)

100

90

80

70

60

50

40

30

20

10

0100 10 1 0.1 0.01

particle size (mm)

sandy gravel

course gravel

Page 9 of 12

Table 4 Partial safety factor – installation damage (RFID)

Soil type(1) D90 particle size(2)

(mm)Grade RFID

Sandy gravel ≤ 10 35T 1.1555T 1.1565T 1.1580T 1.15

110T 1.10150T 1.10200T 1.10

35/20-20T 1.1555/30-20T 1.1580/30-20T 1.15

110/30-20T 1.10R150/30-30T 1.10R200/30-30T 1.10R400/50-30T 1.10R600/50-30T 1.05R800-100-30T 1.05

Coarse gravel ≤ 35 35T 1.2055T 1.2065T 1.20 80T 1.15110T 1.10150T 1.10200T 1.10

35/20-20T 1.2055/30-20T 1.2080/30-20T 1.15

110/30-20T 1.10R150/30-30T 1.10R200/30-30T 1.10R400/50-30T 1.05R600/50-30T 1.05R800-100-30T 1.05

(1) Compacted soil thickness: 200 mm, weight of vibrating roll: 4550 kg.(2) Detailed particle size distributions are shown in Figure 5

8 Effects of environmental conditions

Weathering (including exposure to sunlight)

8.1 The geogrids have adequate resistance to weathering and exposure to sunlight, when protected from exposure in accordance with recommendations of this Certificate. A reduction factor (RFW) of 1.13 may be used for design provided the periods of exposure are limited to a maximum of one month. A reduction Factor (RFw) of 1.00 may be used where the product is covered within one day.

Chemical/environmental effects

8.2 Within a soil environment where pH ranges from 4.0 to 9.0, the geogrids have adequate resistance to hydrolysis for applications where sustained soil temperatures are not higher than 25°C.

8.3 The geogrids are highly resistant to microbiological attack.

8.4 When designed and installed in accordance with the requirements of BS 8006-1 : 2010, BS EN 14475 : 2006 and this Certificate, the geogrids are suitable for use in soils at temperatures normally encountered in reinforced soil embankments in the UK. Long-term resistance to chemical and microbiological attack at temperatures greater than 25°C or lower than 0°C are outside the scope of this Certificate. Where geogrids may be exposed to temperatures outside this range, the advice of the Certificate holder should be sought.

Page 10 of 12

8.5 To take account of chemical/environmental effects including hydrolysis, resistance to acids and alkaline liquids and biological/microbial attack, the appropriate value for RFCH shown in Table 5 may be used for design temperatures up to 25ºC and pH levels in the range 4.0 to 9.0.

Table 5 Reduction factor RFCH

Design life (years) RFCH

60 1.03

120 1.06

9 Factor of safety for the extrapolation of data (fs)9.1 For Fortrac T and R-T Geogrids, the factor of safety for the extrapolation of data (fS) should be taken as:

Table 6 Factor of safety for extrapolation of data

Design life (years) fs

60 1.07

120 1.11

9.2 The above values has been calculated in accordance with PD ISO/TR 20432 : 2007, using the R1 and R2 values given in Table 7:

Table 7 R1 and R2

Factor Taking account of: Design life (years)

60 120

R1 Extrapolation of creep rupture data 1.05 1.05

R2 Extrapolation of chemical data 1.05 1.10

10 MaintenanceAs the product is confined within the soil and has suitable durability, maintenance is not required.

11 DurabilityThe geogrids will have adequate durability for a design life of up to 120 years when used and installed in accordance with this Certificate.

Installation

12 General12.1 The construction of reinforced soil embankents incorporating the geogrids should be in accordance with the Certificate holder’s Installation instructions, BS EN 14475 : 2006 and the Specification for Highway Works.

12.2 Care should be exercised to ensure Fortrac T and R-T Geogrids are laid with the warp (longitudinal) direction parallel to the direction of principal stress. Design drawings should indicate geogrid orientation (see section 4.6).

13 Procedure13.1 The geogrid is laid by unrolling the grid to the length required and cutting with a sharp knife or scissors. The unrolling of the grid may be carried out manually or mechanically.

13.2 The grids should be laid flat without folds, parallel with widths in contact to each other. 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 prestressing load prior to filling.

13.3 Particular care should be taken to ensure that the grids are adequately covered before compaction or trafficking. Construction traffic will damage unprotected geogrids.

13.4 Fill materials and the thickness and compaction of the fill should be in accordance with Highways Agency’s Specification for Highway Works and in line with those conditions used to determine the installation damage partial safety factors in the design (see section 7.5).

13.5 Facings are positioned as detailed on the engineer’s design drawing. Where the geogrids are used as part of the facing, the geogrid must be wrapped around and anchored back into the fill and must be protected from exposure to ultra violet (UV) light as detailed in Sections 6.18 and 8.1. Formwork is used to assist in maintaining the shape of the facing. Facings, prefabricated or otherwise, are beyond the scope of this Certificate. A typical example is shown in Figure 3.

Page 11 of 12

Technical Investigations

14.1 The manufacturing process of the geogrids was examined, including the methods adopted for quality control, and details were obtained of the quality and composition of the materials used.

14.2 An examination was made of data relating to:• evaluation of long- and short-term tensile properties• chemical degradation• resistance to hydrolysis• resistance to biological attack• resistance to weathering• effects of temperature• site damage trials and resistance to mechanical damage• coefficients of interaction between the geogrids and the soil fill• installation procedures and typical details

14.3 Calculations were made to establish the plane sliding area that is solid and the ratio of bearing surface to plane area.

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

Bibliography

BS 8006-1 : 2010 Code of practice for strengthened/reinforced soils and other fills

BS EN 12224 : 2000 Geotextiles and geotextile-related products. Determination of the resistance to weathering

BS EN 12225 : 2000 Geotextiles and geotextile-related products. Method for determining the microbiological resistance by a soil burial test

BS EN 12447 : 2000

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

BS EN 14475 : 2006 Execution of special geotechnical works — Reinforced fill

BS EN ISO 9001 : 2008 Quality Management systems — Requirements

BS EN ISO 9864 : 2005 Geosynthetics — Test method for the determination of mass per unit area of geotextiles and geotextile-related products

BS EN ISO 10319 : 2008 Geotextiles — Wide-width tensile test

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

CIRIA SP123 : 1996 Soil Reinforcement with Geotextiles : Jewel R A

PD ISO/TR 20432 : 2007 Guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement

Manual of Contract Documents for Highway Works, Volume 1 Specification for Highway Works

Manual of Contract Documents for Highway Works, Volume 2 Notes for Guidance on the Specification for Highway Works

Page 12 of 12

Conditions of Certification

15 Conditions15.1 This Certificate:• relates only to the product/system that is named and described on the front page• is issued only to the company, firm, organisation or person named on the front page — no other company, firm,

organisation or person may hold or claim that this Certificate has been issued to them• 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.

15.2 Publications, documents, specifications, legislation, regulations, standards and the like referenced in this Certificate are those that were current and/or deemed relevant by the BBA at the date of issue or reissue of this Certificate.

15.3 This Certificate will remain valid for an unlimited period provided that the product/system and its manufacture and/or fabrication, including all related and relevant parts and 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.

15.4 The BBA has used due skill, care and diligence in preparing this Certificate, but no warranty is provided.

15.5 In issuing this Certificate, the BBA is not responsible and is excluded from any liability to any company, firm, organisation or person, for any matters arising directly or indirectly from:• 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• actual installations of the product/system, including their nature, design, methods, performance, workmanship and

maintenance• any works and constructions in which the product/system is installed, including their nature, design, methods,

performance, workmanship and maintenance• any loss or damage, including personal injury, howsoever caused by the product/system, including its manufacture,

supply, installation, use, maintenance and removal.• any claims by the manufacturer relating to CE marking.

15.6 Any information relating to the manufacture, supply, installation, use, maintenance and removal 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, maintained and removed. It does not purport in any way to restate the requirements of the Health and Safety at Work etc. Act 1974, or of any other statutory, common law or other duty which may exist at the date of issue or reissue 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.


Page 1 of 12

TECHNICAL APPROVALS FOR CONSTRUCTION

APPROVAL

INSPECTION

TESTING

CERTIFICATION

H A P A S

Allan Block Corporation7424 West 78th StreetBloomingtonMinnesota 55439USATel: 00 1 952 835 5309 Fax: 00 1 952 835 0013e-mail: [email protected]: www.allanblock.com

HAPAS Certificate13/H203

Product Sheet 1


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 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.

ALLAN BLOCK RETAINING WALL SYSTEM

AB MODULAR STACKABLE CONCRETE BLOCK WALL SYSTEM FOR REINFORCED SOIL

RETAINING WALLS AND BRIDGE ABUTMENTS

This Certificate relates to the AB Modular Stackable Concrete Block Wall System for Reinforced Soil Retaining Walls and Bridge Abutments for use up to a maximum height of 10 metres. The system comprises concrete block facing units, Fortrac MP and Fortrac T geogrids and compacted fill.

CERTIFICATION INCLUDES:• factors relating to compliance with HAPAS requirements• 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 five-yearly review.

KEY FACTORS ASSESSEDMechanical properties — the method of connection between the geogrids and concrete block facing units has been assessed and long-term connection strength values determined for various wall heights and concrete block/geogrid combinations (see Table 6). The interface shear capacity between adjacent concrete block facing units in between layers of geogrid reinforcement has been assessed and is satisfactory (see section 7.8).Performance of geogrids — the short- and long-term tensile strength of the geogrids, resistance to installation damage, weathering and environmental effects and soil/geogrid interaction have been assessed(1) (See section 7).Durability — when designed and installed in accordance with the provisions of this Certificate, the system will have adequate durability for its intended use as a retaining wall or bridge abutment (see section 9).(1) Data and reduction factors for use in design are given in BBA Certificate 13/H197.

This HAPAS Certificate Product Sheet (1) is issued by the British Board of Agrément (BBA), supported by the Highways Agency (HA) (acting on behalf of the Overseeing Organisations of the Department for Transport; Transport Scotland; the Welsh Assembly Government and the Department for Regional Development, Northern Ireland), the Association of Directors of Environment, Economy, Planning and Transport (ADEPT), the Local Government Technical Advisers’ Group and industry bodies. HAPAS Certificate Product Sheets are normally each subject to a review every five years.(1) Hereinafter referred to as ‘Certificate’.

The BBA has awarded this Certificate to the company named above for the system described herein. This system has been assessed by the BBA as being fit for its intended use provided it is installed, used and maintained as set out in this Certificate.

On behalf of the British Board of Agrément

Date of First issue: 30 July 2013 Brian Chamberlain Claire Curtis-Thomas

Head of Approvals — Engineering Chief Executive

Page 2 of 12

In the opinion of the BBA, the AB Modular Stackable Concrete Block Wall System for Reinforced Soil Retaining Walls and Bridge Abutments, when designed and installed in accordance with the provisions of this Certificate, will meet the requirements of the Highways Agency and local Highway Authorities for the design and construction of reinforced soil retaining walls and bridge abutments.

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: 1 Description (1.2) 3 Delivery and site handling (3.1, 3.3, 3.7 and 3.8) and the Installation part of this Certificate.

Additional Information

CE markingThe Certificate holder’s nominated supplier for the concrete block facing units has taken the responsibility of CE marking the blocks in accordance with harmonised European Standard BS EN 771-3 : 2011. An asterisk (*) appearing in this Certificate indicates that data shown is given in the manufacturer’s Declaration of Performance.

The manufacturer has taken the responsibility of CE marking the geogrids in accordance with harmonised European Standard BS EN 13251 : 2001. An asterisk (*) appearing in this Certificate indicates that data shown is given in the manufacturer’s Declaration of Performance.

Technical Specification

1 Description1.1 The AB Modular Stackable Concrete Block Wall System for Reinforced Soil Retaining Walls and Bridge Abutments comprise:• AB Classic, AB Stones, AB One Degree and AB Vertical modular dry jointed, hollow, concrete block facing units• AB Capstone• Fortrac MP and Fortrac T geogrids(1)

• fill material.(1) covered under BBA Certificate 13/H197.

Concrete block facing units

1.2 The blocks are manufactured from concrete conforming to the following minimum specification, satisfying the Highways Agency’s requirements for durability of class XF2 exposure to BS 8500-1 : 2006 (see Table 1).

Table 1 Concrete characteristics

Property Value

Minimum concrete cube strength at 28 days (N.mm-2) 40

Minimum cement content (Kg.m-3) 340

Maximum water/cement ratio 0.55

1.3 The concrete block facing units covered by this Certificate are shown in Table 2 and Figure 1.

Table 2 AB facing units and AB Capstone

Unit type Height (*)(mm)

Depth (*)(mm)

Width (*)(mm)

Setback(º)

Weight (kg)

AB Stones 200 300 450 12 35

AB Classic 200 300 450 6 35

AB Vertical 200 300 450 3 35

AB One Degree 200 300 450 1 35

AB Capstone 100 300 450 – 27

Requirements

Page 3 of 12

Figure 1 AB facing units and AB Capstone

AB facing unit AB capstone

1.4 The blocks conform to BS EN 771-3 : 2011. The performance characteristics given in Table 3 have been declared by the manufacturer in accordance with this Standard.

Table 3 Performance values in accordance with BS EN 771-3

Property Test method Manufacturer’sdeclared values (*)

Dimensional tolerancesCompressive strength (mean) (N.mm-2)

Category D2>40

Density (kg.m-3) 2350

Maximum water Absorption (%) BS EN 1338: 2003 Annex E

6

1.5 The concrete block facing units are available in a range of colours, including: Limestone Blend, Cinder Blend, Slate Blend, Abbey Blend, Pewter and Cotswold. All pigments used for the coloration of the concrete units comply with BS EN 12878 : 2005.

Geogrids

1.6 Fortrac MP and T Geogrids are planar structures consisting of a regular open network of woven or knitted, integrally-connected tensile elements of yarn coated with a protective layer of black polymer. The MP Geogrid yarn is manufactured from high modulus polyvinyl alcohol (PVA) multifilament fibres in the warp direction and high tenacity polyamide (PA) fibres in the cross machine direction. The Fortrac T Geogrid yarn is manufactured from polyester fibres. The grades(1) covered by this Certificate are:

• Fortrac 20/13-20/30 MP• Fortrac 35/20-20/30 MP• Fortrac 55/25-20/30 MP• Fortrac 80/25-20/30 MP• Fortrac 35/20-20T• Fortrac 55/30-20T• Fortrac 80/30-20T• Fortrac 110/30-20T(1) Full product details are given in BBA Certificate 13/H197

Wall Rock Fill Material

1.7 Crushed coarse aggregate is used to infill the hollow cores of the AB facing units and a 300 mm wide layer immediately behind the wall. The aggregate must be well-graded granular fill ranging in diameter from 6 mm to 38 mm and containing less than 10% passing the 0.075 mm sieve size.

Fill material

1.8 Fill materials must comply with the requirements set out in BS 8006-1 : 2010 and the MCHW, Volume 1.

2 Manufacture2.1 The concrete block facing units are manufactured to an agreed specification by the Certificate holder’s nominated supplier. Ingredients for the concrete are weighed by a computer-controlled weigh-batcher system and the blocks cast in block machines.

2.2 The geogrids are manufactured from yarn woven or knitted into grids and coated with a protective layer of black polymer.

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2.3 As part of the assessment and ongoing surveillance of product quality, the BBA has:• agreed with the respective manufacturers the quality control procedures and product testing to be undertaken• assessed and agreed the quality control operated over batches of incoming materials• monitored the production process and verified that it is in accordance with the documented process• evaluated the process for management of nonconformities• checked that equipment has been properly tested and calibrated• undertaken to carry out the above measures on a regular basis through a surveillance process, to verify that the

specifications and quality control operated by the manufacturer are being maintained.

2.4 The manufacturer’s management system for the concrete block facing units has been assessed and registered as meeting the requirements of BS EN ISO 9001 : 2008 by BM TRADA (Certificate No 6593).

2.5 The manufacturer’s management system for the geogrids has been assessed and registered as meeting the requirements of BS EN ISO 9001 : 2008 by TÜV NORD CERT GmbH (Certificate No 04 100 970084).

3 Delivery and site handling3.1 The concrete block facing units and capstones are tied together with steel straps and delivered to site on shrink-wrapped pallets. The pallets carry a manufacturer’s label bearing the product type and batch code. Pallets should not be stacked more than two high.

3.2 To avoid damage, care should be taken in transit and handling. Damaged materials must not be used. During prolonged periods of storage on site, the blocks should remain covered on pallets.

3.3 The geogrids are delivered to site in 5.0 metre wide rolls between 0.5 m to 0.9 m (Fortrac T) or 0.5 m to 0.6 m (Fortrac MP) diameter, giving approximately 100 m or 200 m of length.

3.4 Each roll is wrapped for transit and site protection in black polythene film and stacked/strapped in timber pallets for distribution.

3.5 Each bag is labelled with the geogrid grade and identification

3.6 The ends of the rolls are sprayed with colour-coded paint to assist identification of a particular grade of geogrid on site in accordance with BS EN ISO 10320 : 1999.

3.7 The geogrids should be stored in clean, dry conditions and protected from mechanical or chemical damage, exposure to direct sunlight and extreme temperatures. When laid horizontally, the rolls may be stacked up to five high. No other loads should be stored on top of the stack. The packaging should not be removed until immediately prior to installation.

3.8 Toxic fumes are given off if the geogrids catch fire and therefore, the necessary precautions should be taken, following the instructions of the material safety data sheet for the product.

Assessment and Technical Investigations

The following is a summary of the assessment and technical investigations carried out on AB Modular Stackable Concrete Block Wall System for Reinforced Retaining Walls and Bridge Abutments.

Design Considerations

4 General4.1 When designed and installed in accordance with this Certificate, the AB Modular Stackable Concrete Block Wall System is satisfactory for the construction of reinforced soil retaining walls and bridge abutments up to a maximum height of 10 metres. Walls above this height require special consideration and are outside this scope of the Certificate.

4.2 Structural stability of the wall system is achieved through:• interface shear capacity between adjacent rows of blocks• the connection strength between the blocks and geogrid layers (see Figure 2) at each layer of geogrid• the tensile strength of the geogrids, and• the embedment and resistance to sliding and pull out of the geogrids from the fill material.

4.3 The connection between the geogrids and concrete block facing units is formed by the interaction between the geogrids and the Wall Rock Fill material placed and compacted into the hollows of the concrete blocks (see Figure 2). It is critical that construction of the connection is carried out carefully and is closely supervised (see the Installation part of this Certificate).

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Figure 2 Connection of geogrids to facing units

Geogrid

concrete block facing unit

compacted Wall Rock Fill(see section 1.7 of this Certificate)

4.4 Prior to the commencement of work, the designer must satisfy the design approval and certification procedures of the relevant Highway Authority.

4.5 The BBA has not assessed the structures for supporting parapet loading caused by vehicle collision at the top of the facing units.

4.6 Reinforced soil structures constructed using the AB Modular Stackable Concrete Block Wall System should be protected with suitable barriers, to protect the structure against potential damage from vehicle impact and vehicle fires.

4.7 In addition to those factors covered in section 6 of this Certificate, attention must also be paid in design to:• site preparation• fill material properties• the specification for placing and compaction of the fill material• drainage behind the wall• protection of the geogrid against damage during installation.

4.8 It is considered that with correct design and workmanship and by following the recommendations of this Certificate, normally accepted tolerances of line and level for the construction of retaining walls as defined in BS 8006-1 : 2010, Table 18, can be achieved. However, where the alignment of the vertical face is critical, consideration may be given to providing a brickwork skin, or similar, to the wall units.

4.9. Particular attention should be paid to changes in direction of walls where overlapping of the geogrids may occur. Detailed guidance is given in the Certificate holder’s technical literature. BS 8006-1 : 2010 also gives guidance on typical layout plans for the geogrids (reinforcing elements) in bridge abutments.

5 Practicability of installationThe system is designed to be installed by trained contractors in accordance with the specifications and construction drawings (see the Installation part of this Certificate). Close supervision is required to ensure the integrity of the connection between the geogrids and concrete block facing units.

6 DesignDesign methodology

6.1 Reinforced soil retaining walls and bridge abutments constructed using the AB Modular Stackable Concrete Block Wall System must be designed in accordance with BS 8006-1 : 2010 and the Specification for Highway Works.

6.2 In accordance with BS 8006-1 : 2010 Annex B, the required design life for permanent walls and bridge abutments is 120 years.

6.3 To evaluate the overall stability of the wall system, it is necessary to consider:• the design strength and length of embedment of the geogrid,• the connection strength between the geogrid and concrete block facing units• the interface shear capacity of the blocks between layers of geogrid reinforcement.

Design strength of geogrids (ultimate limit state)

6.4 The design methodology for determination of the ultimate limit state (ULS) design strength of the geogrids is given in BS 8006-1 : 2010 and in the design sections of BBA HAPAS Certificate 13/H197 Product Sheets 2 and 3 (see also section 7.1 of this Certificate).

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6.5 The ultimate limit state design strength of the geogrid (TD (ULS)), should be taken as:

TCR/fm x fn, where:

TCR = the long-term tensile creep strength of the geogrid, at the appropriate design life and design temperature

fm = the partial material factor

fn = the partial factor for ramification of failure in accordance with BS 8006-1 : 2010, Table 9.

6.6 For the ultimate limit state, the design load (Tj) at each level that the geogrid must resist is calculated using prescribed load factors in accordance with BS 8006-1 : 2010. In all cases, Tj must be � TD (ULS).

Design strength of geogrids (serviceability limit state)

6.7 The serviceability limit state design strength of the geogrid (TD (SLS)), should be taken as:

TCS/fm,

where:

TCS is the tensile load in the reinforcement which induces the prescribed limit value of post-construction strain in the geogrid

fm = the partial material factor

6.8 The definitions of prescribed post-construction strain limit and TCS, the tensile load that would create the prescribed post-construction strain, are explained in Figure 3.

Figure 3 Definition of TCS

prescribed post-constructionstrain limit(0.5% or 1.0%)

strain (%)

isochrone for endof construction(1 month or 2 months)

isochrone forend of designlife (120 years)

load

(kN

)

TCS

6.9 The prescribed maximum allowable post-construction creep strains allowed by BS 8006-1 : 2010 for the serviceability limit state of reinforced soil retaining walls and bridge abutments are shown in Table 4.

Table 4 Serviceability limits on post-construction internal strains for bridge abutments and retaining walls

Structure Strain(%)

Design period for the purposes of determining limiting strain

Bridge abutments and retaining walls with permanent structural loading 0.5 2 months – 120 years

Retaining walls, with no applied structural loading i.e. transient live loadings only

1.0 1 month – 120 years

6.10 Post-construction strain can be related to the average load in the reinforcement. The average serviceability limit state design loads (Tavj) that the geogrid must resist is to be calculated in accordance with BS 8006-1 : 2010. The average load in the jth level (Tavj), is related to the maximum load in the reinforcement (Tj) by a factor k such that Tavj = Tj/k. The factor k has a minimum value of unity and generally falls in the range of 1.0 to 2.0. Where the distribution of tensile load along the loaded length of the reinforcement is not proven by field measurements, the factor k should be taken as unity. In all cases, Tavj � TD(SLS).

6.11 Isochronous curves, design values for Tcs and reduction factors for determination of TD(SLS) are given in Sections 7.2 to 7.5 of this Certificate.

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Design of geogrids (determination of resistance to direct sliding and pull out)

6.12 The design methodology for determination of resistance to pull out and direct sliding, and therefore, the required length of embedment of the geogrids is given in BS 8006-1 : 2010 and in the design sections of BBA HAPAS Certificates 13/H197 Product Sheets 2 and 3.

Connection strength between the geogrids and concrete block facing units

6.13 The design connection strength between the geogrids and concrete block facing units (TDconn) should be determined for the ULS and checks should be made to ensure that it is not exceeded by the design load (Tj ) at each level i.e. Tj � TDconn. Particular care should be taken during the design of bridge abutments to ensure that adequate reinforcement is provided and adequate connection strengths are achieved at the top of the wall and in front of bank seats.

6.14 The design connection strength (TDconn) is determined using the following formula:TDconn = Tconn/fm fnWhere:

Tconn = the long-term connection strength derived from testing (See Section 7.6)

fm = the material safety factor for the geogrid (see Section 7.7)

fn = the partial factor for ramification of failure in accordance with BS 8006-1 : 2010 Table 9.

Interface shear capacity between concrete block facing units

6.15 The interface shear capacity between the concrete block facing units should be checked for the ultimate limit state and checks should be made to ensure that it is not exceeded by the design load (Tj) at each level (see section 7.8).

Specification of fill material

6.16 The designer should specify the relevant properties of the fill material for the reinforced soil structure deemed acceptable for the purposes of the design. Acceptable materials should meet the requirements of BS 8006-1 : 2010 and the MCHW, Volume 1, Series 600.

6.17 Where concrete wall units are to be embedded in potentially aggressive soils, the guidance given in BRE Special Digest 1 : 2005 Concrete in aggressive ground should be followed.

6.18 Fill materials classified as 6I, 6J, 7B, 7C and 7D should comply with the limits of the MCHW1 (600 series), Table 6/3, regarding maximum water soluble sulfate content and maximum oxidisable sulfides content.

7 Mechanical propertiesUltimate Limit State (ULS) design strength of geogrids (TD(ULS))

7.1 The characteristic short-term tensile strength (Tchar) and the associated reduction factors for creep (RFCR), installation damage (RFID), weathering (RFW), environmental degradation (RFCH) and extrapolation of data (fs) required for determination of the ultimate limit state (ULS) design strength of the geogrids (TD(ULS)) are given in HAPAS Certificate 13/H197 Product Sheets 2 and 3.

Serviceability Limit State (SLS) design strength of geogrids (TCS)

7.2 Isochronous curves for the Fortrac MP and Fortrac T geogrids have been derived from long-term creep strain tests and are shown in Figure 4 and Figure 5.

Figure 4 Isochronous curves for Fortrac MP geogrids

1 day

1 month

2 months

1 year

10 years

120 years

strain (%)

0 1 2 3 4 5 6

90

80

70

60

50

40

30

20

10

0

char

acte

ristic

sho

rt-te

rm te

nsile

stre

ngth

(%)

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Figure 5 Isochronous curves for Fortrac T geogrids

1 day

1 month

1 year

10 years

120 years

90

80

70

60

70

50

char

acte

ristic

sho

rt-te

rm te

nsile

stre

ngth

(%)

40

30

20

10

00 1 2 3 4

strain (%)

5 6 7 8 9 10

7.3 For the Fortrac MP geogrids, creep rupture governs the long-term performance of the geogrid, as opposed to creep strain. TCS should therefore be taken as the corresponding TCR value for Fortrac MP geogrids, (see section 7.1).

7.4 For Fortrac T geogrids design values for TCS are given in Table 5.

Table 5 Maximum tensile load inducing prescribed post-construction strain limits for Fotrac T geogrids

Geogrid grade TCS (kN·m-1)

Prescribed post-construction strain limits

0.5% 1.0%

Fortrac 35/20-20T 17.7 20.8

Fortrac 55/30-20T 27.8 32.7

Fortrac 80/30-20T 40.5 47.5

Fortrac 110/30-20T 55.7 65.3

7.5 Reductions factors for installation damage, weathering and environmental degradation (RFID , RFW and RFCH) and factors of safety for the extrapolation of data (fs) required for determination of the serviceability design strength of the geogrids (TD(SLS)) are given in HAPAS Certificate 13/H197 Product Sheets 2 and 3.

Design connection strength between the geogrids and concrete blocks facing units (TDconn)

7.6 Long-term connection strength values (Tconn) for the wall system, for use in determining the design connection strength (TDconn), have been derived from short-term tests in line with the National Concrete Masonry Association Design Manual for Segmental Retaining Walls 1997) and ASTM D6638 Connection efficiencies determined from these tests have been applied to the long-term creep rupture strength (TCR) values for the geogrids, to determine the relevant long-term connection strengths (Tconn). The results are shown in Table 6.

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Table 6 Long-term connection strength values (Tconn) for use in determining design connection strength (TDconn)

Concrete block facing unit type

Geogrid grade TCR(1)

(kN·m–1)Wall height – H(2)

(m)Tconn (3)

(kN·m–1)

AB Classic andAB Stones

Fortrac 20 MP 14.08 0.8 � H � 10.0 2.8

Fortrac 35 MP 24.64 0.9 � H � 10.0 8.1

Fortrac 55 MP 38.72 2.5 � H < 4.94.9 � H < 5.85.8 � H < 7.4

7.4 � H �10.0

9.710.912.313.1

Fortrac 80 MP 56.32 2.5 � H < 5.85.8 � H < 7.47.4 � H < 8.2

8.2 � H � 10.0

13.314.314.916.0

Fortrac 35/20-20T 23.10 1.5 � H < 3.53.5 � H < 9.3

9.3 � H �10.0

8.9 9.910.6

Fortrac 55/30-20T 36.30 1.5 � H < 3.53.5 � H < 9.3

9.3 � H �10.0

9.214.615.7

Fortrac 80/30-20T 52.80 1.5 � H < 3.53.5 � H < 5.25.2 � H < 7.37.3 � H < 9.3

9.3 � H �10.0

9.817.818.320.626.3

Fortrac 110/30-20T 72.60 1.5 � H < 3.53.5 � H < 7.37.3 � H < 9.3

9.3 � H �10.0

9.919.625.427.2

AB One Degree andAB Vertical

Fortrac 35/20-20T 23.10 1.5 � H < 3.5 3.5 � H �10.0

10.311.2

Fortrac 55/30-20T 36.30 1.5 � H < 3.53.5 � H < 9.3

9.3 � H �10.0

14.117.318.0

Fortrac 80/30-20T 52.80 1.5 � H < 3.53.5 � H < 7.37.3 � H < 9.3

9.3 � H �10.0

12.717.219.321.0

Fortrac 110/30-20T 72.60 1.5 � H < 3.53.5 � H < 7.37.3 � H < 9.3

9.3 � H �10.0

13.519.222.022.3

(1) Assumes a design life of 120 years and a design temperature of 20°C.(2) Assumes a density of 1900 kg·m–3 of the fill in the hollow core of AB units and the weight of the whole wall height above the connection(3) In situations where fire can occur adjacent to a structure, connection strength values should be reduced by:• a factor of 1.25 for Fortrac 20 MP, 35 MP and 55 MP and Fortrac 35/20-20T and Fortrac 55/30-20T grades, and• a factor of 1.11 for Fortrac 80 MP and Fortrac 80/30-20T and 110/30-20T grades.

7.7 The reduction factors given in Table 7 should be applied to the long-term connection strength values given in Table 6, in order to determine the design connection strength (TDconn) (see section 6.13).

Table 7 Reduction factors for determination of fm

Material factor Reduction factor and conditions of use/limitations

RFID A value of 1.00 can be used for all grades of geogrid as short-term installation damage at the point of connection is already taken into account during the connection strength tests.

RFW, RFCH , fs As set out in BBA HAPAS Certificate 13/H197 Product Sheet 2 and 3 respectively, according to geogrid specification selected and conditions of use (1).

(1) pH levels within and immediately behind the wall assumed to be the same as those in the main fill material.

Interface shear capacity between concrete block facing units

7.8 Interface shear capacity between the concrete block facing units is provided by the upper concrete lip of the blocks, the friction between the concrete surfaces and the interlock between the particles of fill material. For the AB Modular Stackable Concrete Block Wall System, the interface shear capacity of the blocks is higher than the corresponding connection strength values, due to the concrete lip. Therefore, the connection strength values govern the design.

8 MaintenanceThe exposed faces of the concrete block facing units may require periodic maintenance, to remove dirt build up, mould and moss growth. All other components of the system are confined within the wall and/or fill and do not require maintenance.

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9 Durability9.1 When designed and installed in accordance with this Certificate, the system will have adequate durability for the required 120 year design life of a retaining wall and bridge abutment in conditions encountered in the UK.

9.2 Where the blocks are to be embedded in potentially aggressive soils, the guidance given in BS 8005-1 : 2006 and BRE Special Digest 1 : 2005 should be followed.

10 Reuse and recyclabilityThe concrete facing units can be crushed and re-used as aggregate. The fill material can also be re-used.

Installation

11 General11.1 Detailed information on installation of the AB Modular Stackable Concrete Block Wall System for Reinforced Soil Retaining Walls and Bridge Abutments can be found in the Certificate holder’s Installation Guide.

11.2 A typical cross-section of a reinforced soil retaining wall constructed using the AB Modular Stackable Concrete Block Wall System is shown in Figure 6.

Figure 6 Typical cross-section of reinforced soil wall

compaction zone consolidation zone

impermeable fill

Wall Rock Fill (see section 1.7 of this Certificate)

geogrid

drain pipe

concrete block facing units

fill material

11.3. Installation should also comply with the requirements of BS 8006-1 : 2010 and BS EN 14475 : 2006.

11.4 Close supervision is required particularly during construction of the geogrid to concrete block facing unit connection.

11.5 Detailed guidance on forming curves and corners, including the placement of geogrids, can be found in the Certificate holder’s Installation Guide.

11.6 Where accurate cutting of facing units is required on site, disc-cutting techniques may be used, for which appropriate precautions must be taken to mitigate against hazards associated with dust.

11.7 During construction it is particularly important to ensure that:• fill is properly compacted, especially close to facing units• at each construction stage, the level of the compacted fill coincides with the level of the facing unit connection to

prevent the risk of voids occurring below the geogrid• the geogrid is tensioned at right angles to the plane of the facing, within a tolerance of ± 50 mm in a five-metre

length, and the geogrid is pulled tight to ensure that all slack is removed• regular checks are made to confirm the alignment of the face and to ensure that any disturbance from compaction

process is promptly corrected.

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12 Procedure12.1 The first row of blocks is laid on a levelling pad comprising either well-graded, good compactable material ranging in diameter from 6 mm to 38 mm, or a suitable concrete foundation laid to the correct level. It is important that the first course of concrete block units is laid accurately to the correct line and level, to avoid compounding errors in alignment as the wall is built.

12.2 Selected crushed coarse granular Wall Rock Fill aggregate (see section 1.7) is placed and compacted in the hollow cores of the concrete block facing units up to the top of the blocks and to a thickness of 300 mm width behind the blocks. Suitable fill soil is then placed and compacted behind the granular fill.

12.3 A drain pipe is installed at the back of the wall and should be vented to a daylight or a stormwater system.

12.4 The compaction requirements for the main fill material depend on the fill type selected and can be found in the MCHW, Volume 1, Clause 612. Heavy plant exceeding one tonne should not be allowed within two metres of the face of the wall (MCHW, Volume 1, Clause 622.7). A vibrating plate compactor of less than one tonne must carry out compaction within this zone.

12.5 The next course of concrete blocks facing units is laid, ensuring that the vertical seams are offset by at least 75 mm. The filling and compaction process is repeated as detailed in sections 12.2 and 12.4.

12.6 Geogrids are placed at the levels shown on the project construction drawings. A suitable length of geogrid is cut from the roll and laid with the cut edge tight against the back edge of the raised front lip of the concrete block facing units. The geogrid is placed with the machine direction perpendicular to the wall face and pulled back over the compacted area.

12.7 The next row of concrete block facing units is placed carefully into position on top of the geogrid, checking regularly that the geogrid remains in its correct position as each block is laid. Once the blocks are in place, the geogrid is pulled back, hand tight, to remove any slack and the corners staked in position. Further checks must be made at this stage, by observation through the hollows in the concrete blocks to ensure that the geogrid is still correctly embedded within the blockwork wall.

12.8 Wall Rock Fill is then placed into the hollow cores of the concrete blocks up to the top of the blocks and to 300 mm width behind the blocks. Suitable fill soil is also placed behind the granular Wall Rock Fill. The fill should be placed by mechanical plant with an opening bucket, avoiding trafficking of unprotected grids, and should cover the grid reasonably uniformly.

12.9 The fill materials are compacted as detailed in section 12.4, starting with the Wall Rock Fill placed in the hollow cores of the concrete block facing units, so forming the geogrid/block connection and then behind the wall, working away from the wall.

12.10 The general construction procedure described is repeated until the required coping is reached.

12.11 The coping units include a concrete lip to prevent them sliding forward over the wall and can be additionally secured using a high grade, flexible, waterproof masonry adhesive (outside the scope of this Certificate).

Technical Investigations

13 Investigations13.1 The manufacturing process for the concrete facing units was examined, including the methods adopted for quality control, and details were obtained of the quality and composition of the materials used.

13.2 An examination was made of test data relating to:• strength of concrete block facing units• durability• performance of the retaining wall system under fire test conditions• the connection strength between the geogrids and facing units.

13.3 An assessment was made of the method of installation to assess the practicability and ease of construction of the system.

13.4 Research papers and test reports regarding the performance of the System during seismic activity were examined.

13.5 Case studies relating to use of the the AB Modular Stackable Concrete Block Wall System for Reinforced Soil Retaining Walls and Bridge Abutments in projects around the world were examined.

13.6 Dimensional check tests were carried out on the concrete block facing units and capstone units.

Bibliography

BBA HAPAS Certificate 13/H197 Product Sheet 2 Fortrac Geosynthetics — Fortrac MP Geogrids

BBA HAPAS Certificate 13/H197 Product Sheet 3 Fortrac Geosynthetics — Fortrac T and R-T Geogrids

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BRE Special Digest 1 : 2005 Concrete in aggressive ground

BS 8006-1 : 2010 Code of practice for strengthened/reinforced soils and other fills

BS 8500-1 : 2006 Concrete — Complementary British Standard to BS EN 206-1 — Method of specifying and guidance for the specifier

BS EN 12878 : 2005 Pigments for the colouring of building materials based on cement and/or lime — Specifications and methods of test

BS EN 14475 : 2006 Execution of special geotechnical works — Reinforced fill

BS EN ISO 9001 : 2008 Quality Management systems — Requirements

ASTM D6638 Standard Test Method for Determining Connection Strength Between Geosynthetic Reinforcement and Segmental Concrete Units

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)

Conditions of Certification

14 Conditions 14.1 This Certificate:• relates only to the product/system that is named and described on the front page• is issued only to the company, firm, organisation or person named on the front page — no other company, firm,

organisation or person may hold or claim that this Certificate has been issued to them• 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.

14.2 Publications, documents, specifications, legislation, regulations, standards and the like referenced in this Certificate are those that were current and/or deemed relevant by the BBA at the date of issue or reissue of this Certificate.

14.3 This Certificate will remain valid for an unlimited period provided that the product/system and its manufacture and/or fabrication, including all related and relevant parts and 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.

14.4 The BBA has used due skill, care and diligence in preparing this Certificate, but no warranty is provided.

14.5 In issuing this Certificate, the BBA is not responsible and is excluded from any liability to any company, firm, organisation or person, for any matters arising directly or indirectly from:• 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• actual installations of the product/system, including their nature, design, methods, performance, workmanship and

maintenance• any works and constructions in which the product/system is installed, including their nature, design, methods,

performance, workmanship and maintenance• any loss or damage, including personal injury, howsoever caused by the product/system, including its manufacture,

supply, installation, use, maintenance and removal• any claims by the manufacturer relating to CE marking.

14.6 Any information relating to the manufacture, supply, installation, use, maintenance and removal 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, maintained and removed. It does not purport in any way to restate the requirements of the Health and Safety at Work etc. Act 1974, or of any other statutory, common law or other duty which may exist at the date of issue or reissue 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.
