Understanding the Numerous Facets of Tunnelling

India is seeing a spate of new tunnel developments since the past few years, led by infra projects such as mass urban transit, railways, roads and highways, hydropower, irrigation, sewerage, water supply etc. Attempts are being made to adopt cutting edge technologies and use the most advanced equipment so that tunnels can be executed and made operational at the earliest. There is also deployment of newer materials and solutions aimed at enhancing the strength, longevity, quality, sustainability, and durability of the tunnels.

In fact, sustainability is on the agenda of many countries, agencies, and every industry, as it is being increasingly recognized as an important part of construction projects. The construction industry not only contributes significantly to greenhouse gas emissions but also, globally, uses 40% of the building materials and resources. The focus so far has been on making buildings sustainable and there has been less attention on infrastructure and civil works.

At the recently held Tunnelling Asia 2023 conference in Mumbai, the focus was on climate resilience and sustainability in the creation and long-term use of underground spaces. Many cities worldwide are now increasing their use of underground spaces as they have begun to consider underground construction a spatial asset that extends beyond transport tunnels and utilities to host many facilities. To make this possible, we must avail the opportunities present and maximize our efforts during the early planning and design stage of new/upcoming tunnel projects in order to avoid the cost of changes in design later on.

Tunnels are constructed to last for typically more than 100 years. Hence, ensuring sustainable construction of all new tunnelling projects needs to be ensured during the planning stage itself so that there is minimum environmental impact. The days are not far when, to get project funding and public acceptability, a project would be required to be justified on grounds of its sustainability, durability, and its minimum environmental impact.

To make tunnels sustainable for the long term, technological advancements in their construction should focus on two specific areas: raw material processing and infrastructure operations. The raw materials used should be sourced primarily through energy-intensive cement and steel production. This is because we need to make judicious use of natural resources in construction and use building materials that help reduce GHG emissions. For instance, the recent development of design solutions that use steel and plastic fibres as primary structural elements for the final lining of underground structures is a critical step towards achieving “tunnel sustainability.”

To ensure efficient operations of the underground structure, it would be a good idea to formulate a framework to identify key action areas, which should include the following:

• Design for flexibility and optimum utilization of underground spaces
• R&D for material innovation and re-utilization
• Standardization and industrialization of processes
• Equipment optimization and re-cycling
• Building resilience against climate change
• Decarbonize tunnelling activities
• Systems and materials that reduce cost of operation, maintenance, reconstruction, and repair.

In this issue, readers will find many articles and case studies on construction and maintenance of tunnels, advanced machines and equipment used in blasting, planning and execution of tunnel projects etc. These informative articles written by experts in the field, will surely help engineers expand their knowledge as they discover on-ground intricacies, technicalities, and complexities involved in tunnelling.

Guest Editor
Dr. Mangu Singh
President, Tunnelling Association of India & Principal Chief Advisor, Delhi Metro Rail Corporation Ltd.