Going underground – tunnelling to lead with new BIM and data technology

The UK is developing a lead in tunnelling and the data management technology that will feature prominently in future infrastructure programmes, says Topcon GB & Ireland senior business development manager Jim Woodhams.

Space is at a premium in the UK, especially in the major cities. With the vast majority of space above ground developed, one solution to deliver critical infrastructure projects is to go underground. This has the benefit of enabling delivery right to the heart of a congested city without requiring significant space on the surface. The completion of Crossrail has shown 
that the UK has the skills to overcome the technical challenges of delivering subterranean infrastructure. And with projects such as Crossrail 2, Thames Tideway and sections of HS2 running underground, there is certainly a lot more to come.

The city taking the lead on underground networks is London. Early stations on the London Underground system were constructed using a “cut and cover” method, where a trench 
is dug, infrastructure placed, and the trench covered up again. This method was quickly abandoned by the late 19th century, owing to the considerable disruption, with the boring method taking preference to allow construction without needing to clear the surface.

While technology has moved forward considerably since the London Underground first began operating in 1863, the challenges faced are similar. When a new tunnel is bored, it needs
 to avoid pipework, sewage lines and electricity points, while ensuring it does not affect existing infrastructure, both underground and on the surface. The process is complicated further by a lack of visibility and dependence on a range of asset records – some decades or even centuries old – to show what needs to be avoided in the subterranean realm.

Academy formed to retain skills

To help deliver a project with pinpoint accuracy, developers need confidence in both the information and the skills available to them. The development of Crossrail brought with it the establishment of the UK Tunnelling & Underground Construction Academy (TUCA), enabling a legacy to be built and skills to be retained for future projects. Through Crossrail 2, an extension to the Northern Line to Battersea Power Station and the discussion of a road link beneath the Pennines to connect Manchester and Sheffield, there is plenty of scope to ensure these skills are developed further.

Delivering a tunnel project requires a mass of accurate information. Below ground, the guidance of the tunnel boring machine or roadheader is critical. Typically this will require precision surveying equipment. The constraints of limited sight lines and restricted space call for specialist techniques. Survey data will be collected and transmitted to the tunnelling control systems for real-time guidance and decision making.

On the surface, control surveys are carried out and the ground or structures monitored to ensure that
 any movements due to the tunnelling beneath are within acceptable design limits. Maintaining the safety of the workers and the public is paramount. Use of precision surveying equipment, skilled operatives and robust procedures are vital to ensure the maintenance of data quality to support this vital requirement. Emerging technologies such as laser scanning, fibre optics, computer vision and big data can improve data quality as well as increase efficiency.

BIM will provide valuable insights

The information taken on board will likely be integrated into a building information modelling system. The inclusion of monitoring data within BIM systems could give important and valuable insights into geotechnical and structural behaviours in the built environment, especially once the original designers and engineers have moved on. This will be of significant interest in the future, not just for infrastructure replacement, but also for assessing the viability of extending the life of assets.

There is no doubt that going underground presents a distinct challenge. But through compilation of existing data and greater collaborative handling of new data from ongoing projects, future tunnelling schemes will be delivered with greater efficiency and long-term effectiveness. This will help to establish tunnelling as a core option for delivering the key infrastructure projects needed in future.