MECHANISED TUNNELLING | TECHNICAL


lubrication system. A project where it was used is in northwest France, on the new 20km-long Landivisiau gas pipeline connection for a new power plant in Brittany. The route runs through gneiss, granite and schist with rock strengths of up to 185MPa, and under the River Élorn and a railway with low overburden. The alignment was varied – a gradient of 17%, a curve radius of 700m, and elevation difference of 26m between the entry and exit points, and 40m between the entry and deepest point. The tunnel is 530m long. Groundwater pressure is up to 4 bar. For such a challenging drive with a 250kW AVN 1800


(OD 2,185mm), bentonite lubrication was important to control friction between the pipe and rocks, and so reduce the required thrust force at the main jacking station and successfully achieve breakthrough (see Figure 7).


Exploration and injection drilling Small diameter systems can also accommodate probe drilling ahead of the face, and in hard rock projects also handle grout injection. While probing/grouting are common in large diameter TBMs, it is now also possible to equip MTBMs (≥ 1,800mm) with such facility to establish geology ahead of the machine. One such small diameter project where probing/


grouting equipment was used is in Chile, for seawater inlet and brine outlet tunnels connected to the Los Pelambres desalination plant that conveys clean water


to a copper mine located in a drought area. The tunnel works constructed a 345m-long intake tunnel and 543m-long outlet tunnel on the Chilean coast. Tunnelling involved use of an AVND 2000 and an AVN 1800 (OD 2,500mm), fitted with an exploration and injection drill. Geology was mostly strong diorite and gabbro (UCS up to 250MPa). At a fault zone, the probe drill was installed and ground injection performed, securing the ground to facilitate safe inspection and change of tools on the cutting wheel (see Figure 8).


CONCLUSION There has been a growing trend toward smaller diameters and longer drives in trenchless tunnelling, which has placed a greater emphasis on the design and selection of efficient MTBM equipment. Hard rock tunnelling in small diameters presents specific challenges in combination with slurry pipejacking machines but important technical progress has been made. Geotechnical investigation need to be as detailed as


possible for MTBM use in hard rock projects. To further increase tunnelling performance, it is


important to gather and analyse relevant performance data which will be the basis for a continuous improvement process. Advancing digitalisation will improve the possibilities of data acquisition and evaluation.


REFERENCES 1


2


Hunt, D., Nash, D., and Rogers, C. (2014). Sustainable utility placement via Multi-Utility Tunnels, Tunnelling and Underground Space Technology, Vol. 39, 15–26, doi: 10.1016/j.tust.2012.02.001.


Ong, D.E.L., Barla, M., Cheng, J.W.-C., Choo, C.S., Sun, M., and Peerun, M.I. (2022). Sustainable Pipe Jacking Technology in the Urban Environment, Springer Singapore, Singapore, doi: 10.1007/978-981-16-9372-4.


3 Kaushal, V., Najafi, M., and Serajiantehrani, R. (2020). Environmental impacts of conventional open-cut pipeline installation and trenchless technology methods: State-of-the-art review, Journal of Pipeline Systems Engineering and Practice, Vol. 11, No. 2, 3120001, doi: 10.1061/ (ASCE)PS.1949-1204.0000459.


4 5 6


Luo, Y., Alaghbandrad, A., Genger, T.K., and Hammad, A. (2020). History and recent development of multi-purpose utility tunnels, Tunnelling and Underground Space Technology, Vol. 103, 103511, doi: 10.1016/j.tust.2020.103511.


Sterling, R.L. (2020). Developments and research directions in pipe jacking and microtunneling, Underground Space, Vol. 5, No. 1, 1–19, doi: 10.1016/j.undsp.2018.09.001.


Lu, H., Matthews, J., and Iseley, T. (2020). How does trenchless technology make pipeline construction greener? A comprehensive carbon footprint and energy consumption analysis, Journal of Cleaner Production, Vol. 261, 121215, doi: 10.1016/j.jclepro.2020.121215.


7 Tavakoli, R., Najafi, M., Tabesh, A., and Ashoori, T. (2017). Comparison of Carbon Footprint of Trenchless and Open-Cut Methods for Underground Freight Transportation, American Society of Civil Engineers, doi: 10.1061/9780784480892.005.


8 Wehrmeyer, G. (2018). Development trends in mechanised tunnelling, Geomechanics and Tunnelling, Vol. 11, No. 6, 730–737, doi: 10.1002/geot.201800051.


9


Lang, G., and Lehmann, G. (2022). Rock tunnelling in small diameters: latest trends and technologies, North American Society for Trenchless Technology (NASTT) No-Dig Show 2022.


10 Lehmann, G., Käsling, H., Cambier, A., Praetorius, S., and Thuro, K. (2022). Performance analysis of utility tunneling data: A case study of pipe jacking in hard rock in Brittany, France, Tunnelling and Underground Space Technology, Vol. 127, No. 104574, 1–10, doi: 10.1016/j. tust.2022.104574.


11 Lehmann, G., Lübbers, M., and Fluck, A. (2023) Slurry pipe jacking in hard rock: Pushing boundaries for sustainable infrastructure. Societa Italiana Gallerie (SIG – Italian Tunnelling Society) Gallerie e Grandi Opere Sotterranee (Journal – Tunnels and Major Underground Works), 2023, N.146


January 2024 | 29


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49