Shotcrete for Africa Application of Mechanised Wet Shotcreting in the Gautrain Tunnels 3 rd March 2009 Presented by Richard 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 Tunnels Bombela 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 E1 E6 E5 E7 E2 E3 E4 D&B D&B TBM (Tunnel Boring Machine) 1000m 900m 220m 2800m 800m 2300m 1300m 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 Maximum Thickness (mm) Advance Primary (minimum) Secondary Single SC1 >15 Nil Nominal where required 50mm SS as <6m (structurally not required) required 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 3m FRS Single SC4b 0.07-0.5 100mm FRS in Crown and Walls 150mm FRS in Crown and Walls Min 250mm 1.5m Arch at 1.5m centres FRS Single SC5 0.007-0.07 100mm FRS in Crown and Walls 250mm FRS in Crown and Walls Min 350mm 1.5m Arches at 1.25m centres FRS Single SC6 <0.007 175mm FRS, in Crown and Walls 200m FRS in Crown and Walls Min 375mm 1.5m Arches at 1.5m centres FRS in Crown and Walls
Twin Tunnel Lining Design Support Class Q Shotcrete (Grade C25) Plain -PS Fibre Reinforced-FRS Total Lining Maximum Thickness (mm) Advance Primary (minimum) Secondary Twin SC0 >22 Nil Nominal where required (structurally 50mm SS as 6m not required) required 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 + Min 300mm FRS 1.5m to 2.5m 50mm of PS Arches at 1.3m centres &PS
Ground classes Single 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
Mix Design Development – Summary Duration of process:4 months Key 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 availability Supply of Cement and aggregates, suitability, delivery and storage.
Mix design – Performance results 100 100 100 100 98.3 CEM I 42.5 N 360 kg/m3 64% 90 90 90 89.5 Fly Ash 100 kg/m3 18% 80 79.0 Percentage passing 73 72 70 GGBS Slag 100 kg/m3 18% 63.7 60 Filler Sand 185 kg/m3 55 51.2 50 50 EFNARC Crusher Sand 816 kg/m3 40 envelop 37 37.0 9.5mm 539 kg/m3 30 27.6 26 22 20 19.7 Fibres 4 kg/m3 Combined grading 12.2 11 12 10 EFNARC Specification W/C ratio 0.45 4 0 1 0 . m m 1 m m 1 0 m m 1 m m 0 0 0.15 0.3 0.6 1.18 2.36 3.35 5 6.3 10 14 20 37.5 Superplasticizer 5 kg/m3 Sieve mm Particle size (mm) Slump: Slump retention: 170mm +/- 30mm 6 hours Hard Shotcrete Cubes Sprayed Shotcrete with 25 kg/m3 of accelerator Compressive strength Compressive strength Flexural strength 8 hours 3 MPa 24 hours 3 MPa 8 MPa 7 days 45 MPa 20 MPa 28 days 60 MPa 30 MPa 3.5 MPa
Site Batch Plant Park Station Batch Plant 37m 3 /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 / hr Rosebank Station – 37m3 / hr Park 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 407 Shotcrete Unit Single Tunnel 4-15m3/hr Paus ITC 10 000 Agicar with Putzmeister PM 500 Shotcrete Unit Twin Tunnel 8-20m3/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 time Correct quality of supply and checking Prior preparation of equipment Maintenance of equipment Skilled operators
Tunneling cycles • SC1 to 3 – Shotcrete every 2 nd or 3 rd 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 m³ daily 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 quality visual quality time spent to spray per cycle minimise rebound minimise 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
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