Examples on some special rock constructions
A. Unlined water tunnels and shafts with moderate to high pressures
A lined tunnel is a tunnel where the surface is covered (by concrete or concrete and steel). Most often used for concrete lined tunnels. Covers also tunnels with steel pipe imbedded in concrete. The expression ‘lined’ was launched before sprayed concrete (shotcrete) had been introduced as support in tunnels. Today, shotcrete also forms lining when shotcrete is applied on the entire roof and walls.
Unlined tunnels are tunnels without support or with rock bolts, mesh, straps, or when shotcrete has been applied only on the parts of the tunnel surface. Unlined tunnels are appropriate in good and fair rockmass conditions. In parts where local poor rockmass zones occur, concrete or shotcrete lining is used. This is described here
For a typical low-head pressure tunnel, the hydraulic head inside the pressure tunnel might be in the range of 40m to 100m, while high-head pressure tunnels have heads of 300m to more than 1000m.
The following papers deal with unlined pressure tunnels or shafts:
Palmström A.: Norwegian design and construction experience of unlined pressure shafts and tunnels. Int. Conf. on Hydropower, Oslo, 1987, 13 p.
Palmström A.: Unlined high pressure tunnels and shafts. In Norwegian Tunnelling Today, 1988. Tapir Publishers, Trondheim, Norway, pp. 73 – 75.
Aasen O., Odegaard H. and Palmstrom A. (2013): Planning of pressurized headrace tunnel in Albania. In Norwegian Hydropower Tunnelling series, Publ. no. 22, 8p.
Palmström A. and Broch E. (2017): The design of unlined tunnels and shafts – 100 years of Norwegian experience. Presented in the journal Hydropower & Dams.
B. Unlined air cushion surge chambers
An air cushion surge chamber is used for damping surges in the headrace pressure tunnel of and underground hydropower plant. It replaces the conventional, open surge chamber or surge shaft.
Data on some air cushion surge chambers are given here
C. Subsea tunnels and lake taps
Subsea tunnels comprise tunnels, which pass below rivers, lakes or sea bottom. Such tunnels can be road or railway tunnels, or water conveying tunnels.
“Lake tap” or submerged tunnel piercing means hole-through from a tunnel to the sea or lake bottom. Lake taps are used in hydropower where the headrace tunnel may have its intake through the piercing. Data on some lake taps are given here
Papers published on subsea tunnels are found in the following links:
Palmström A.: Geo-investigation and advanced tunnel excavation technique important for the Vardø subsea road tunnel. Int. symp. on Low Cost Road Tunnels, Oslo 1984, 15 p.
Lynneberg T.L., Palmström A., Roska S. and Carstens K.J.: Geology, design, construction and maintenance of Vardö sub-sea road tunnel. Int. conf. on Strait Crossings, Stavanger, Norway, 1986, pp. 623 – 641.
Palmström A.: Sub-sea rock tunnels. Invited paper at the Int. conf. on Strait Crossings, Stavanger, Norway, 1986, pp. 111 – 139.
Holestöl K. and Palmström A.: Subsea tunnelling for oil: The Petromine concept. Tunnelling and Underground Space Technology. Vol. 2, No. 4, 1987, 31.1 – 31.31.
Palmström A.: Subsea tunnels. In Norwegian Tunnelling Today, 1988. Tapir Publishers, Trondheim, Norway, pp. 93 – 96.
Palmström A.: Norwegian experience with subsea tunnels. Int. conf. on Tunnels and Water. Madrid, 1988. A.A. Balkema publishers, Rotterdam. 8 p.
Palmström A.: Introduction to Norwegian subsea tunnelling. Publ. No. 8, issued by the Norwegian Soil and Rock Engineering Association, 1992, pp. 8 – 12.
Palmström A. and Naas R.: Norwegian subsea tunnelling – rock excavation and support techniques. Int. Symp. on Technology of bored tunnels under deep waterways, Copenhagen, 1993, pp. 201 – 225.
Palmström A.: The challenge of subsea tunnelling. Tunnelling and Underground Space Technology, Vol. 9, No. 2, 1994, pp. 145 – 150.
Palmström A. and Naas R.: Under the sea in Norway. World Tunnelling, November 1995, pp. 353 – 360.
Palmström A. and Skogheim A.: New Milestones in subsea blasting at water depth of 55 m. Tunnelling and Underground Space Technology, Vol. 15, No. 1, 1999, pp. 65 – 69.
Nilsen B., Palmström A. and Stille H.: Quality control of a sub-sea tunnel project in complex ground conditions. ITA World Tunnel Congress ’99, Oslo, pp. 137 – 145.
Holmöy K., Lien J.E. and Palmström A.: Going sub-sea on the brink of the continental shelf. Tunnels & Tunnelling International, May 1999, pp. 25 – 30.
Palmström A., Stille H. and Nilsen B.: The Fröya tunnel – a sub-sea road tunnel in complex ground conditions. Swedish annual rock Mechanics conference, Svenska Bergmekanikdagen, 2000, pp. 19 – 30.
Nilsen B. and Palmström A.: Stability and water leakage of hard rock subsea tunnels. Conf. on Modern Tunneling Science and Technology, Adachi et al. (eds), 2001, Kyoto, Japan, pp. 497-502.
Palmstrom A. and Huang Z.: Application of Norwegian Subsea Tunnel Experience to Construction of Xiamen Xiang’an Subsea Tunnel. Int. symp. on Construction techniques of subsea tunnels, Nov. 6-8, 2007, Xiamen, China. 12 p.
Nilsen B. and Palmstrom A. (2013): Methodology for predicting and handling challenging rock mass conditions in hard rock subsea tunnels. Intn. conf. on Strait Crossings, Bergen, Norway, 11p.