Modelling aids tunnel project

Building Information Modelling (BIM) has led to vast improvements in preliminary works at the Beckton wastewater treatment facility in east London. Chris Abdee, a technical director in AECOM’s transportation business, reports.

Building Information Modelling (BIM) has yet to become standard practice across the construction industry, and in water projects in particular, despite the benefits it offers to designers and engineers. Used appropriately, this innovative process of modelling structures and managing data can save time and money, boost accuracy and ensure the efficient flow of project data.

The powerful role BIM can play in the water industry was recently demonstrated during enabling works for Thames Water’s Lee Tunnel, east London. This project will create a cleaner, healthier and more pleasant city, by constructing a seven kilometre tunnel under the River Lee to intercept 16 million tonnes of sewage mixed with rainwater from discharging into the River Lee on an annual basis.

Project summary

The £635M Lee Tunnel project is the first of two major tunnel projects (The Lee and Thames tunnels) planned to deal with the discharge of untreated effluent into the Thames Tideway and is the largest infrastructure project ever awarded in the UK water industry.

Since 2002, AECOM has been instrumental in various capacities on both the Thames Tunnel and Lee Tunnel projects, as adviser, designer, engineer and consultant. The works at Beckton include constructing a new drive and overflow shaft to drive the Lee Tunnel and act as an emergency discharge point. This shaft construction required the demolition of decommissioned buildings and infilling of underground Victorian structures with lightweight foam concrete.

To ensure the accurate planning of the Beckton upgrade and aid engagement with English Heritage and the London Borough of Newham, Thames Water commissioned AECOM to provide a physical model of these historic structures.

Dating from the days of Sir Joseph Bazalgette, this complex series of buildings posed a unique challenge to the CAD team.

To visualise the configuration of buildings and establish how best to access the underground structures, Rapid Model Prototyping (RMP) was used to translate a CAD model into a physical one. This involved the use of a 3D printer to combine machine-cut layers of epoxy resin.

Having this physical model, built in segments, meant sections could be taken apart to reveal vital information about the nature of the underground voids without the need for time-consuming and potentially hazardous underground investigations. This tactile environment allowed stakeholders to collaborate and explore design iterations. AECOM’s application of BIM, which is often used by architects in the design and construction of new buildings, proved equally effective in modelling existing structures. Its engineers are now benefitting from the use of this process, having already commissioned a number of models successfully, with expanded use expected.

Following the completion of the physical model, permission was gained to infill the underground structures and demolish most surface buildings. The existing Victorian chimney has been dismantled and preserved and will be re-erected on completion of the Lee Tunnel project in its original location as a marker post to the end of the Bazalgette network of sewers.

Thames Water’s Nick Butler, project manager for the Lee Tunnel, says: “We found the physical model invaluable in aiding the planning and execution of the sludge removal and concrete infilling works to this complex Victorian structure.”

The Lee Tunnel shaft is under construction and work on the Lee Tunnel drive, which will be 8m in diameter and 80m in depth, will also commence this year.

BIM has yet to be rigorously defined across the construction industry, which may be one reason why it has not been taken up more fully. One way AECOM defines it is as an integrated process; a method of controlling, sharing and managing data across project teams using highly accurate digital models.

Although it uses CAD modelling, BIM involves many more processes than 3D design alone. It is an overall strategy for making the managing of information more efficient and can be applied throughout all stages of the project. While traditional methods result in a series of separate drawings for each discipline involved in a project, BIM ensures synergy between teams by enabling them to work on the same CAD model. This improves coordination, ensures that all parties are working from the most recent revisions and allows final drawings to be issued direct to fabricators and contractors.

The expenditure of water companies is increasingly dominated by capital maintenance with the requirement to improve existing assets becoming greater than the need to replace them. BIM and RMP are fantastic for understanding upgrade requirements, from generation of point cloud data and 360° laser surveys, to the capture, downstream management and reuse of data. When combined with RMP physical models, the accurate visualisation these provide is invaluable in comprehending the complex configurations of the water industry’s existing structures and heavily serviced buildings.

AECOM is making a commitment to harnessing the power of BIM across as wide a range of projects as possible. The process is so flexible that it can conceivably be applied to anything in the built environment, including complex water systems such as the Tideway Tunnels. BIM presents a huge opportunity for improving design and construction and the sooner it is taken up across the industry, the sooner, clients, designers and contractors can reap its benefits. n

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