Cutting deep and covering well for minimum-impact tunnels
The construction of cut-and-cover tunnels are vital for new transport infrastructures, which in turn have much to offer in the development of the Trans-European Transport Network (TEN-T). Although already widely employed, this method must now fulfil a new set of requirements, including safer and more cost-effective techniques, and reduced environmental impact. The approach eliminates or greatly reduces many nuisances associated with construction projects in urban areas. Dust, noise, large construction equipment and even traffic disruption are just some examples of such nuisances. In efforts to fulfil these requirements, an industrial consortium established the 'Sustainable construction of underground transport infrastructures' (SCOUT) project. Seeking to optimise the safety and life-cycle cost of such construction, team members took a holistic approach to introduce a novel and sustainable concept to a method already promising a cost-effective alternative to tunnels. Focusing on design, materials and construction equipment, project objectives looked to implement the observational method for full control of construction and delays, optimise design for savings in materials, and introduce a radical new construction concept for equipment. SCOUT partners also aimed to develop and test new applications of composites materials for optimising structure efficiency, and open the way towards recycling excavated materials. Extensive project work resulted in numerous successes and new knowledge. Assessments regarding design optimisation highlighted the potential for significant savings when combining components of certain design approaches. Savings related to material costs could surpass 15 % when using conventional reinforced concrete. This is due to the fact that the development of fibre-reinforced concrete is still under way. A new construction concept using modular architecture was developed on the strength of individual partner contributions. The building and validation of a new equipment prototype indicated that production objectives envisioned at the onset of the project could be realised. Along with other project successes, SCOUT managed to show that the conceptualisation of proposed equipment was indeed valid. The knowledge advanced also offers insight into how to achieve many of the new requirements for better construction of tunnels, across the board.
