Shotcrete for AfricaApplication of Mechanised Wet Shotcreting

in the Gautrain Tunnels3rd March 2009

Presented byRichard McIntyre & Robert Pettit

Introduction

The Application of Mechanised Wet Shotcreting in the Gautrain Tunnels

• The Gautrain Rapid Rail Project • Design development from a mixture of shotcrete and

insitu concrete lining to shotcrete only.• Shotcrete mix design development and testing• Equipment selection process• Application process for safe and successful tunnel

construction

Gautrain TunnelsBombela Civil Joint Venture - Drill and Blast Tunnel Length 11.4Km

(12.7Km including parallel track, emergency chambers & connections)

Gautrain Tunnel Stations and Shafts Park Station Rosebank Sandton

D&B D&B

TBM (Tunnel Boring Machine)1000m 900m 220m 2800m 800m 2300m 1300m

E1 E5E2 E3 E4 E6 E7

Mushroom

Sandton

Marlboro Portal

500m 1800m 3000m

Lining Design

• Support requirements were established from assessment of the ground conditions and categorised into a rock classes.

• Rock classification was based on the Q System• Each class of rock has its own support pattern for the

different tunnel cross sections.• Support consists of rockbolts, shotcrete, lattice arches or

steel ribs and canopy tubes.• Advance lengths per round were limited for each class.

(between 6m and 1.5m)

Single Tunnel Lining Design

Support Class Q Shotcrete (Grade C25) Plain-PS Fibre Reinforced-FRS Total Lining Thickness (mm)

Maximum AdvancePrimary (minimum) Secondary

Single SC1 >15 Nil Nominal where required (structurally not required)

50mm SS as required

<6m

Single SC2 6 -15 50mm FRS in Crown Nominal where required Min 50mm FRS 6m

Single SC3 2-6 50mm FRS in Crown and Walls Nominal where required Min 50mm FRS 6m

Single SC4a 0.5-2 50mm FRS in Crown and Walls 50mm FRS in Crown and Walls Min 100mm FRS

3m

Single SC4b 0.07-0.5 100mm FRS in Crown and Walls 150mm FRS in Crown and Walls Arch at 1.5m centres

Min 250mm FRS

1.5m

Single SC5 0.007-0.07 100mm FRS in Crown and Walls 250mm FRS in Crown and Walls Arches at 1.25m centres

Min 350mm FRS

1.5m

Single SC6 <0.007 175mm FRS, in Crown and Walls 200m FRS in Crown and Walls Arches at 1.5m centres

Min 375mm FRS in Crown and Walls

1.5m

Twin Tunnel Lining Design Support Class Q Shotcrete (Grade C25) Plain -PS Fibre Reinforced-FRS Total Lining

Thickness (mm)Maximum Advance

Primary (minimum) Secondary

Twin SC0 >22 Nil Nominal where required (structurally not required)

50mm SS as required

6m

Twin SC1 4-22 50mm FRS in Crown and Walls 75mm FRS in Crown and Walls Min125mm FRS 6m

Twin SC2 1-4 50mm FRS in Crown and Walls 75mm FRS in Crown and Walls Min 125mm FRS 6m

Twin SC3 0.1 to 1 50mm FRS in Crown and Walls 150mm FRS in Crown and Walls Min 125mm FRS 3.5m to 6m

Twin SC4 Dry 0.05 to 0.1 175mm FRS in Crown and Walls 50mm FRS in Crown and Walls Min 225mm FRS 1.5m to 4m

Twin SC4 Wet 0.05 to 0.1 175mm FRS in Crown and Walls 50mm FRS in Crown and Walls + 50mm of PS Arches at 1.3m centres

Min 300mm FRS &PS

1.5m to 2.5m

Ground classesSingle Tunnel SC3

Ground classes

Twin Tunnel SC4 Dry

Ground classes

Twin Tunnel Drainage

Tunnel Drainage

Half Round Pipe for Localised Inflows

Tunnel Drainage

Pozidrain Strips with Mesh for Diffuse Seepage

Duration of process:4 monthsKey Issues:

- Definition of the specification:Workability, Compressive & Flexural Strength, Bond strength, Durability, European Standard EN 206-1 adopted - Analysis of the environment (chemistry):Groundwater and the soil quality- Ready-mix industry:Local supplier quantity, reliability and quality related to the specifications- Batching-plants equipment:BCJV supply option to install batch plants on site, space and sizing- Raw materials availabilitySupply of Cement and aggregates, suitability, delivery and storage.

Mix Design Development – Summary

Mix design – Performance results98.3

89.5

79.0

63.7

51.2

37.0

27.6

19.7

12.2 11

22

37

55

73

100

26

50

72

90

100 100

0.15 0.

3

0.6

1.18

2.36

3.35 56.

3 10 14 20

37.5

4

90

12

0

10

20

30

40

50

60

70

80

90

100

0 .1 m m 1 m m 1 0 m m 1 0 0 m m

Particle size (mm)

Perc

enta

ge p

assi

ng

Combined grading

EFNARC Specification

Sieve mm

CEM I 42.5 N 360 kg/m3 64%

Fly Ash 100 kg/m3 18%

GGBS Slag 100 kg/m3 18%

Filler Sand 185 kg/m3

Crusher Sand 816 kg/m3

9.5mm 539 kg/m3

Fibres 4 kg/m3

W/C ratio 0.45

Superplasticizer 5 kg/m3

EFNARC envelop

Slump: 170mm +/- 30mm Slump retention: 6 hoursHard Shotcrete Cubes

Compressive strength Compressive strength Flexural strength8 hours 3 MPa24 hours 3 MPa 8 MPa7 days 45 MPa 20 MPa

28 days 60 MPa 30 MPa 3.5 MPa

Sprayed Shotcrete with 25 kg/m3 of accelerator

Site Batch Plant

Park Station Batch Plant 37m3/hr

Quality Control – Batch plant

• At the start, approved materials were checked and trial mixes were batched to demonstrate the performance of the shotcrete

• Slump test done on every batch, before send to site.• Every 50m³ manufactured, cubes are taken for

compressive strength tests.

Quality Control - Site

• Every truck received: • visual checking

– checking for segregation of mix– fibres agglomeration– aggregate uniformity– mix property

• slump – checked at site prior to discharge from the truck– check after storage in Secatol before filling the Agicar in the

tunnel, slump test done.

Quality Control - Site

• Once a week - panel sprayed for compressive strength testing.

• Once every two weeks - panel sprayed for flexural strength beam testing.

• Every 100 metres of tunnel - in situ bond strength test will be done.

• Every 100 metres of tunnel - in situ compressive strength will be checked by coring.

• Shotcrete thickness is checked;SC1 to SC3 - Visual inspection all bolts covered.SC4a to SC6 - Coring / drilling every 50m.

Shotcrete supply system

• 3 Batch plants;Marlboro portal – 2 by 50m3 / hrRosebank Station – 37m3 / hrPark Station – 37m3 / hr

• Dispatched to sites with 6m3 truck mixers – 12 units.• Discharged into 5 – 7m3 remix hoppers.• When needed discharged into 5.5m3 Agicars and transported to the

face.• Weekly forecast• Daily conformation• 24hrs / day, 7 days per week.

Supply constraints

• Delivery schedules being altered – delays.• Large concrete pours for stations. • Quality of shotcrete supplied with incorrect workability.• Traffic (peak hours).• Availability of trucks / drivers (especially over weekends).

Shotcrete supply

Shotcrete Equipment

Paus ITC 10 000 Agicar with Putzmeister PM 500 Shotcrete Unit Twin Tunnel 8-20m3/hr

Paus ITC 10 000 Agicar with Putzmeister PM 407 Shotcrete Unit Single Tunnel 4-15m3/hr

Shotcrete Equipment

PM 500 at Marlboro

PM 407

PM407 Shotcrete Unit Spray Area Single Tunnel

PM407 Shotcrete Unit Spray Articulation

Shotcrete in tunnels

• Key aspects for successful application of shotcrete;Organisation in the tunnel to arrange delivery on timeCorrect quality of supply and checkingPrior preparation of equipment Maintenance of equipmentSkilled operators

Tunneling cycles

• SC1 to 3 – Shotcrete every 2nd or 3rd round. “Shotcrete not critical.”

• SC4a to 6 – Primary lining to be applied with every excavation cycle. Shotcrete critical.

• The quantity and frequency was typically:monthly shotcrete production: 5110 m³daily shotcrete production: 189 m3 (7.8 m³/hr)average duration for each shotcrete application in tunnel: 3 hours once to twice a day

Training of operators

• Operators – Mixture of experienced foreign and local trained operators.

• All foreman trained as operators – backup and ensure they have the required knowledge to manage the process.

• The ability of the operator will condition:structural qualityvisual quality time spent to spray per cycleminimise reboundminimise accelerator consumption

Application

Quality control before spraying requires the following:• shift foreman to scale and wash down the newly exposed rock

surfaces• the surveyor to check profile clearances• the geotechnical engineer to confirm rock class• the operator to check equipment is clean and ready for operation• quality control while spraying• accelerator dosage to be controlled • air delivery pressure to be controlled• profile controlled build-up in 50mm thick layers • controls in themselves provide direct limitation of rebounds, loss and

wastage

Application

Quality control after spraying requires:• curing of the shotcrete• subsequent layers sprayed onto a clean surface• depth of cover to protruding rockbolts

Shotcrete application

Shotcrete application in arch section

Tunnel after primary shotcrete application

Conclusion

• The approach to providing a drained tunnel solution using a variable selection of methods with proven materials within the shotcrete application has been shown to be a viable design solution.

• The requirement to apply shotcrete as a composite support and final lining was implemented through attention to the shotcrete material design, the selection of suitable equipment to allow high quality work in the tunnels, while the training of operators to ensure controlled spraying was essential to the successful application of the system.

Conclusion

• With the tunnel overbreak typically being 500mm in the places where concrete lining may have been required, the saving in overbreak concrete alone will amount to some 10,500R/m in the single tunnel.

• The most significant saving however is in time which will allow the project to be commissioned more rapidly and bring forward the date at which revenue can be earned.

Thank YouAny Questions ?