Benoit de Rivaz

Innovative FRC Design for Underground Application

Benoit de Rivaz

Bekaert Maccaferri Underground Solution

AGENDA

Introduction

Basic info about Fibre product

Basic info about Testing Method

FRC for Final Lining

Conclusion

Introduction

4

Fibres for concrete , they appear in all colours , shapes, sizes and materials.

Specific technical strenghts and weakness of the different fibres, are often less wellknown, and lead to confusion.

They is no good and bad product but the right product for the right used

So it is also important to specified and test the right performance according the project requirement

Which testing method for which information and why ?

Which type of fibre for which application ?

1. Sufficient exchange surface (number, length, diameter of fibres).

2. The nature of the fibre-matrix interface allows for proper loadtransfer.

3. The intrinsic mechanical properties (Young’s modulus,anchorageand tensile strength) of the fibre allows the forces to be absorbedwithout breaking or excessively elongating the fibre.

Therefore, for efficient load transfer, the following three conditions must be satisfied:

The behaviour of fibre reinforced concrete is more than a simple superposition of thecharacteristics of the concrete matrix and the fibres; to analyse the behaviour of this compositematerial, also the interaction between both has to be taken into account, i.e. the transfer ofloads from the concrete matrix to the fibre system.

Behaviour of Fibre Reinforced Concrete

The quality of steel fibre is due to a combination of factorsA high length-diameter ratio (L/D ratio)

Controlled pull-out (due to deformation of the hook)

High tensile strength steel

Hooked ends

A system of glued fibre bundles enables fibres with a high L/D ratio to be mixed easily and uniformly throughout the concrete

Different type of fibre and dosageDifferent Behaviour Clear Different performance at 5mm (civil works), 10mmSimilar Energy Absoprtion at 40mm

Which testing method for which information and why

The different ways of specifying the ductility of fibre reinforced sprayed concrete in terms of residual strength and energy absorption capacity are not directly comparable.

The residual strength must be specified when the concrete characteristics are used in a structural design model

The energy absorption value measured on a plate with continuous support (Underterminal Panel test) can be specified when, in the case of rock-bolting, emphasis is laid on energy which has to be absorbed during the deformation on the rock”.

9

Three or four

point bending

test

Determinal

crack pattern

Value for

design2

sp

jR,

jR,2bh

3Ff

L fr1 (CMOD=0,5mm) => SLS

fr3 (CMOD=2,5mm => ULS

Continuous support

Underterminal crack pattern

Testing system propeties and behaviour

No design value but Energy absoption criteria

Load redistribution –multicrak pattern

E

N

E

R

G

Y

A

B

S

O

R

P

T

I

O

N

R

E

S

I

D

U

A

L

S

T

R

E

N

G

H

T

ASTM C1550

EN 14 488-5

UNDERDETERMINAL CRACK PATTERNDETERMINAL CRACK PATTERN

12

3 point bending test configuration on notched specimen (EN 14651) is suitable for characterizinga FRC material since it reduce the structural effects on the tests

NB 4 point bending test on un-notched specimen introduced structural effectse.g. the monitored section is not defined these effects can modify the response of the tests when materials properties changee.g. moving from softening to hardening behavior

Reference test EN 14651

The notch will provide a slower cracking process, thereby reducing the risk of a sudden faiureThe notch will allow direct Crack mouth opening displacement messurement or deflectionlThe notch will decrease the variation the result

Hardening post-crack behaiour

2

sp

j

,2

3

hb

lFf jR hsp = 125 mm

b = 150 mm

S.L.S

fR,1 fR,3

U.L.S.fL,k

Reference test EN 14651

Deflection 0.465mm Deflection 2,165mm

The reference design documents

14

Model Code 2010 – 5.6.3 ClassificationThe post-cracking residual strenghts can be classified by using two parameters, namely fR,1k

(representing the strength interval) and a letter a, b, c e d (representing the ratio fR,3k / fR,1k). Thestrength interval is defined by two subsequent numbers in the series:

1,0, 1,5, 2,0, 2,5, 3,0, 4,0, 5,0, 6,0, 7,0, 8,0 (MPa)

while the letter a, b, c, d correspond to the residual strength ratios:

a if 0,5 ≤ fR,3k / fR,1k ≤ 0,7

b if 0,7 ≤ fR,3k / fR,1k ≤ 0,9

c if 0,9 ≤ fR,3k / fR,1k ≤ 1,1

d if 1,1 ≤ fR,3k / fR,1k ≤ 1,3

e if 1,3 ≤ fR,3k / fR,1k

The designer has to specify the class, the residual strength ratio and the material of the fibre.

Fiber reinforcement can substitute (also partially) conventional reinforcement at ultimate limitstate if the following relationships are fullfilled:

fR,1k / fLk > 0,4 fR,3k / fR,1k > 0,5

Understanding SFRC design – Basic principle

15

Constitutive law (Model Code 2010)

Section moment capacity

Bending stresses

Tension stresses

compression zone

tension zone(steel fibers)

Internal moment capacity

Material properties

We use more and more TBM machine

Steel fibre reinforced concrete for segmental lining

Main trend on the precast concrete segmental linings

Design and installation methods are wellknown by the contractor

Some recent innovation in segment assembling

Conventionalreinforcementcage

Stirrups welded to the mats

Top and bottom mats

The reinforcement

cage has to resist to:

- Demoulding forces

- Stacking forces

- Transportation forces

- Spalling forces

- Jacking forces

Heavy reinforcement with rebars: from

60 to 180 kg/m3

Demolding Stacking Transport

& PlacingService

Bending

Tension

Compression

Impact

Shrinkage &

Temperature Effects

Segmental lining design procedure: Acting forces

Main difficulty with precast segment

Bursting in segments occurs from two different types of loads:

In-place forces due

to compression

in the ring

During

installation by

the application

of ram loads to

the edge of the

segments

- Minimal concrete cover requirements

for corrosion

combined with …..

- Particular edge shapes

leads to……

- Vulnerable edges

Spalling at a joint with a

particularly vulnerable profile

Inadequate reinforcement

Repairs must be made that ensure long term durability

How long will

you guarantee

this repair?

VOICE OF DESIGNER

NEW GUIDELINE PUBLISHED IN 2016

New development in the segmental lining design

Ever increasing concrete compressive strenghtfor fast demoulding

Dra

mix

®

4DDra

mix

®

3DDra

mix

®

24

PerformanceSFC

Concrete compressive strenght

• Single hook• 1450 N/mm²• L/D 80

• 4D hook• 1850 N/mm²• L/D 80

• Single hook• 1150 N/mm²• L/D 80

BEAM TEST ACCORDING TO EN 14 651

HARDENING POST CRACK BEHAVIOUR

TEST SCALE 1 : BENDING TEST

HARDENING POST CRACK BEHAVIOUR

TEST SCALE 1 : CONCENTRATED LOAD

The first crack appeared for a load level of 1000 kN (for each steel pad) between the two shoes at the top and extrados surface. It has to remark that the first crack occurred at a load level higher than the design value (785 kN) and the maximum load of the TBM (1100 kN);

The maximum crack width at the end of the test, after the complete unloading, was about 0.05 mm

Comparison Rebar / mesh Dramix®

Concrete

Energy consumption (GJ/m³) 2,89 2,89

Reinforcement

Reinforcement (kg/m³) 100 40

Type mesh DRAMIX

Energy consumption (GJ/ton) 22,5 22,5

Energy consumption (GJ/m³) 5,14 3,79

Reduction of energy consumption 26%

Dramix® minimizes the impact on the environment

Using less steel for the same strength

Durability a key issue : 120 years design life

no loss of bending strength if the crack width is smaller than 0,5mm (Brite Euram) in the mean time the maximum crack width at the end of the test, after the complete unloading, was about 0.05 mm

SFRC presents an overall improved durability to corrosion compared to conventional reinforcement.

From the early 90’s, over 131 projects have been realized with steel fibers, by Bekaert and Maccaferri worldwide:

• 49 hydraulic projects (39 only fibers + 10 combined)• 40 metro lines (23 only fibers + 15 combined + 2 others)• 18 utilities (17 only fibers + 1 combined)• 12 railways (4 only fibers + 8 combined)• 9 roads (3 only fibers + 6 combined)• 3 others (2 only + 1 combined)

• 88 of them are steel fiber’s only reinforced• 43 are reinforced combining steel fibers and rebarsMax Fext for steel fiber’s only solution (Dramix): 12,4 m (North-South Bypass Tunnel (Clem 7), Brisbane & Airport Link / Northern Busway, Brisbane)

FRC segmental lining reference projects

• Excellent durability

• Damage due to handling and installation is minimized;

• Performance in the relevant Ultimate and Service Limit States (ULS and SLS) can be reliably demonstrated;

• Reduced waste;

• Overall manufacturing costs are lower than for conventionally reinforced concrete.

• A lower carbon footprint

• Sustainability advantages

Current state of the art

PERMANENT SPRAY CONCRETE LINING HOW PSCL IS DEVELOPING?

Permanent sprayed concrete

Automated, mechanized construction

Safety culture-limited man access

Spray waterproof membranes

Surveying technology fibres

Higher skilled operatives

Improved design techniques

Architectural solution ?

2. HOW SCL IS DEVELOPING

One mould for two test procedure given the key information

about FRC

Energy Absoption + Residual Strength

ENERGY ABSORPTION RESIDUAL STRENGHT

Specification Restriction Proposal

THE ROLE OF SFRC –DESIGN-METHOD OF CARACTERISATION

Perfromance mini according to MC2010

fR,1k / fLk > 0,4

fR,3k / fR,1k > 0,5

Hardening post crak behaviour

F el-max must be obtained for a deformation less than 2 mmF post fiss min. between 0 and 5mm ≥ 0.8 Fel-max

ENERGY ABSORPTIONMini 100joules

RESIDUAL STRENGHT

Permanent Spray Concrete Lining

Basic Concept of our Newly FRC

The Fibre

+ 5DDra

mix

®

+Ultra High tensile strength(2.200 N/mm²)

Perfect Anchorage High ductility wire ( > 6 %)

Very high pull out force

No performance loss

Steel is elongating

Large scale tests

“During the tests in our laboratory at the TU Kaiserslautern,

I was astonished about the strength of the Dramix® 5D fibre. In comparison with

conventional steel fibres

it has an impressive performance.

This fibre certainly opens up a lot of possibilities

for new applications with steel fibre reinforced concrete.”Prof. Dr.-Ing. Jürgen Schnell

Technische Universität Kaiserslautern

Unseen Level of Performance

Venda Nova III Repowering ProjectFinalist for ITA AWARDS

SFRC Cast-In-Place Final Lining

Riva Tuneli – 3rd Bridge Tunnel -Turkey

Date: 2014-2015

Project name: Riva Tuneli – 3rd Bridge Tunnel

Tunnel type: Highway

Client: Istanbul Municipality

Country: Turkey

Contractor: IC Ictas – Astaldi Consortium

Fiber type: 5D 65/60BG

Dosage rate: 20 kg/mc

Concrete class: C30/37

Max diameter: 22 meters

CAST IN PLACEFAST AND EASY APPLICATION WITH 5D INSIDE

INNER LINING LEE TUNNEL UK

The finished lining

Secondary / Inner Lining

Designed with MC2010 by UnPS)

Traditional reinforcement removed,

about 15000 tons

Design by test approach with BRE

laboratory

Just 2100 tons of 5D6560BG Dramix®

used @40kg/m (67pcy), 60mm long &

0.90mm diameter this dosing rate

provided excellent bending hardening

properties to the concrete section.

Jansen Mine Shafts – Saskatchewan, Canada

Shaft Basics – Construction:

• Shaft walls range from 800mm thick

up to 1.1m thick, Depth = 1km

• Interior Diameter of 8.5 m

• Shaft walls are slip formed with a scheduled

production of up to 3m per day.

• Concrete strength 60Mpa

• Dosage rate 40kg / m³ to 70kg/m3

Conclusion FRS is an important high performance method of ground support

Quality and safety can be achieved using the relevant product

for the right use

Relevant testing method to determine engineering properties

and for quality control

Design standard

The use of the finished material should be considered along with the test

and performance criteria

post crack behavior ,

match crack widths and deformation in the test to expectations in the

project and durability requirement

Right fibre for the right use

Conclusion

Thank you sincerely for your attention