Tunnelling At Roads Fact Sheet
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Tunnelling at roads and railways
The Western Corridor Recycled Water (WCRW) Project is a $2.4 billion water supply network designed to diversify South East Queensland's water sources. It involves treating wastewater to the highest standard – resulting in purified recycled water. Purified recycled water will be supplied to power stations, industry and agricultural customers and the Wivenhoe Dam through a 200km network of large diameter underground pipes, three advanced water treatment plants and supporting infrastructure. The WCRW Project is the largest advanced recycled water project of its kind in the southern hemisphere. When complete, it will have the capacity to deliver up to 232 megalitres of purified recycled water a day to end users. The Queensland Government is contributing $2 billion and the Australian Government is contributing $408 million through the Water Smart Australia Program. This fact sheet explains how the project will tunnel under more than 90 roads and railways using trenchless technology (tunnel boring and microtunnelling) techniques.
Why tunnel under road and rail crossings? Tunnel boring and microtunnelling causes minimal disturbance to sensitive areas where open cut trenching is not possible or where roads and railways would need to be shut down during construction. Trenchless technology allows the pipeline to be constructed under these sensitive areas without causing any significant disturbances to the ground and existing underground services.
What preparation work is needed? An excavator digs temporary working pits on each side of the crossing. These pits are the start and finish point for the microtunnelling/tunnel boring machine as it excavates the tunnel. Sheet piling is inserted by a crane or excavator around the internal perimeter of the working pit to provide reinforcement around the pit walls. A concrete base is laid in the pit to provide a solid working surface. In soft ground, the sheet piling forms a steel wall around the internal perimeter to support the soil around the pit. In ground where there is hard rock, no sheet piling is necessary, however rock bolts and other supports may be needed. The depth of the working pit is determined by the required tunnel/pipe alignment and the position of nearby underground services. Each working pit will range from 6 to 14 metres in depth, 12 metres in length and 5 to 12 metres in width.
When will pit construction occur? The construction of pits will occur during normal working hours. Depending on design, the depth of the pit and ground conditions, the construction of the working pit may take between a few days and a few weeks.
Department of Infrastructure and Planning
The location of the pit will ensure the crossing is as short as possible. During construction of the pit the construction team will minimise any work within existing utility easements and work primarily within the pipeline easement, unless additional temporary working space is required and secured. The pit will be fenced off and secured at night to ensure security and to prevent public access.
The operation of the machine and surface equipment will create some noise around the working pit, and some crossings may require nighttime operation of the machinery. Noise mitigation will be implemented at the sites to ensure noise levels are kept at a minimum. Spoil from the tunnelling operation may be kept temporarily on site and removed later.
How is the tunnel built?
What machines will be used?
A crane lowers the tunnelling machine into the pit and machine operators enter the pit. The machine is propelled forward by successfully jacking the machine and casing pipe whilst excavating a tunnel.
A minimum of three modern tunnelling machines, including an American Augers boring machine, a Herrenknecht EPB1500 microtunnelling machine, and an Akkerman WM48C tunnel boring machine, will allow construction of pipelines under sensitive areas (such as roads and railways) where open trenching is not possible.
The tunnels will be approximately 1.5 metres in diameter to allow the 1086mm recycled water pipe to be inserted inside the casing pipe. Where more than one recycled water pipe is required in the one alignment, separate tunnels are constructed for each pipeline.
Tunnelling Operation Schematic
The auger boring machine will be used for short crossings, the Akkerman machine will be used for crossings averaging 100 metres in length and the Herrenknecht machine will be used for longer crossings. The machines will excavate the tunnels using laser guidance systems. This maintains the correct tunnel alignment for the installation of the recycled water pipeline.
What equipment will be used on the surface? Surface equipment includes generators, craneage, equipment storage containers, hydraulic power packs, Bentonite mixing/pumping equipment and site amenities.
For more information Contact the Project Team: Phone: 1800 997 464 (freecall) Email: [email protected] www.westerncorridor.com.au March 2008
Printed on recycled paper
Department of Infrastructure and Planning
The Western Corridor Recycled Water (WCRW) Project is a $2.4 billion water supply network designed to diversify South East Queensland's water sources. It involves treating wastewater to the highest standard – resulting in purified recycled water. Purified recycled water will be supplied to power stations, industry and agricultural customers and the Wivenhoe Dam through a 200km network of large diameter underground pipes, three advanced water treatment plants and supporting infrastructure. The WCRW Project is the largest advanced recycled water project of its kind in the southern hemisphere. When complete, it will have the capacity to deliver up to 232 megalitres of purified recycled water a day to end users. The Queensland Government is contributing $2 billion and the Australian Government is contributing $408 million through the Water Smart Australia Program. This fact sheet explains how the project will tunnel under more than 90 roads and railways using trenchless technology (tunnel boring and microtunnelling) techniques.
Why tunnel under road and rail crossings? Tunnel boring and microtunnelling causes minimal disturbance to sensitive areas where open cut trenching is not possible or where roads and railways would need to be shut down during construction. Trenchless technology allows the pipeline to be constructed under these sensitive areas without causing any significant disturbances to the ground and existing underground services.
What preparation work is needed? An excavator digs temporary working pits on each side of the crossing. These pits are the start and finish point for the microtunnelling/tunnel boring machine as it excavates the tunnel. Sheet piling is inserted by a crane or excavator around the internal perimeter of the working pit to provide reinforcement around the pit walls. A concrete base is laid in the pit to provide a solid working surface. In soft ground, the sheet piling forms a steel wall around the internal perimeter to support the soil around the pit. In ground where there is hard rock, no sheet piling is necessary, however rock bolts and other supports may be needed. The depth of the working pit is determined by the required tunnel/pipe alignment and the position of nearby underground services. Each working pit will range from 6 to 14 metres in depth, 12 metres in length and 5 to 12 metres in width.
When will pit construction occur? The construction of pits will occur during normal working hours. Depending on design, the depth of the pit and ground conditions, the construction of the working pit may take between a few days and a few weeks.
Department of Infrastructure and Planning
The location of the pit will ensure the crossing is as short as possible. During construction of the pit the construction team will minimise any work within existing utility easements and work primarily within the pipeline easement, unless additional temporary working space is required and secured. The pit will be fenced off and secured at night to ensure security and to prevent public access.
The operation of the machine and surface equipment will create some noise around the working pit, and some crossings may require nighttime operation of the machinery. Noise mitigation will be implemented at the sites to ensure noise levels are kept at a minimum. Spoil from the tunnelling operation may be kept temporarily on site and removed later.
How is the tunnel built?
What machines will be used?
A crane lowers the tunnelling machine into the pit and machine operators enter the pit. The machine is propelled forward by successfully jacking the machine and casing pipe whilst excavating a tunnel.
A minimum of three modern tunnelling machines, including an American Augers boring machine, a Herrenknecht EPB1500 microtunnelling machine, and an Akkerman WM48C tunnel boring machine, will allow construction of pipelines under sensitive areas (such as roads and railways) where open trenching is not possible.
The tunnels will be approximately 1.5 metres in diameter to allow the 1086mm recycled water pipe to be inserted inside the casing pipe. Where more than one recycled water pipe is required in the one alignment, separate tunnels are constructed for each pipeline.
Tunnelling Operation Schematic
The auger boring machine will be used for short crossings, the Akkerman machine will be used for crossings averaging 100 metres in length and the Herrenknecht machine will be used for longer crossings. The machines will excavate the tunnels using laser guidance systems. This maintains the correct tunnel alignment for the installation of the recycled water pipeline.
What equipment will be used on the surface? Surface equipment includes generators, craneage, equipment storage containers, hydraulic power packs, Bentonite mixing/pumping equipment and site amenities.
For more information Contact the Project Team: Phone: 1800 997 464 (freecall) Email: [email protected] www.westerncorridor.com.au March 2008
Printed on recycled paper
Department of Infrastructure and Planning
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