Tunnels in the Delta and underground construction

Delta area’s all over the world are the most densely populated areas that exist, and due to urbanisation existing cities in the Delta seem to grow larger and larger.  The attractiveness of Delta’s comes forth from the combination of water, land and transport. Especially transport is an economic driver for the growth of cities around harbour areas.

The combination of diverse forms of transport on the one hand and conflicting interests between transport and the quality of life in habituated areas leads to a demand for tunnels. Tunnels under rivers and canals to entwine diverse forms of transport. Tunnels under the city for public transport to maintain the quality of life in urban areas.

Apart from that due to globalisation there is an economic pressure to reduce barriers between centres of economic activity. Typical examples of the latter are also associated with very long tunnels, such as the Fehmarn Bealt tunnel between Germany and Denmark; an immersed tunnel and the bored rail tunnels under the Alps, such as the Gotthard Base tunnel between Zurich and Milan.  

What we see is that bored tunnels are often used for Underground Metro systems in the larger cities, such as London, Paris and even Amsterdam, whereas immersed tunnels are a relatively cheap alternative for river and canal crossings. Apart from that there is a growing demand for roads to be roofed over for motorways that pass through city areas, which are called land tunnels.

In general two methods of construction are often used to build tunnels:

  • Bored tunnels
  • Immersed tunnels

Bored tunnels are built in situ; in general using a TBM machine that travels underground and that leaves an opening that is clad by a lining that forms the tunnel.

Bored tunnel

Immersed tunnel

Immersed tunnels are built in a dock and afterwards towed to the site and immersed into a pre-dredged trench to form a tunnel. 

For both methods of construction, in addition to the aforementioned building techniques one needs to have a thorough understanding of excavation techniques, construction techniques to build underground for the construction of starting shafts for the tunnel boring and or to construct ramps to connect to for the immersed tunnels.

Research

The research into tunnels is aimed at several stages in the Life Cycle of tunnel and is either aimed at reducing  risks during construction or during operation, or to reduce costs.

The research has diverse fields of research:

o  Other types of tunnels

  • Immersed floating tunnels

o  Construction

  • Industrial fabrication for Immersed tunnels (continuous fabrication of longer elements, slipway methods and floating dry-dock)
  • Logistic effects for lining construction for DOT (Double O Tube) tunnelling method

o  Design an risk control of tunnels

  • Flood control of tunnels in low lying areas
  • Earth Quake resistant tunnels
  • Stresses in tunnel lining due to Jack-forces by the TBM;
  • Stresses and strains due to temperature effects including fire for bored tunnels
  • Creep effect due to braking forces for bored tunnels that are driven only one-ways
  • The applicability of the Delft Grout pressure model in 3D analyses of bored tunnels

o Asset management

  • Long term settlement behaviour of immersed tunnels (for tunnels with a sand underflow foundatiom and for tunnels on gravel bed)
  • Life cyle assessment of tunnels
  • Leakage control for older tunnels
  • Tunnel safety

Design Projects

In order to develop tunnel design skills we encourage student to make a tunnel design as their final project for their MSc thesis; feasible projects are:

  • Long immersed tunnels under the Ijssel-lake connecting Enkhuizen and Stavoren
  • The Blankenburg tunnel
  • The Oranje tunnel
  • Land tunnels in the connection Schiphol, Amsterdam and Almere
  • IJmeer tunnels for public transport between Amsterdam IJburg and Almere
  • Industrial Fabrication for the Fehmarn Baelt tunnel
  • The Messina strait crossing

Immersed tunnel