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Rock Mass Classification of Chalk Marl in the UK Channel Tunnels Using Q

  • Nick Barton
  • Colin Warren
Chapter

Abstract

The Q-system for rockmass, core and tunnel logging was used extensively in the TransManche Link TBM tunnelling, and also in a consortium claim against owner Eurotunnel in the early 1990s. In this connection, the Q-system was also used by the first author for logging precedent conditions in local tunnels in chalk marl, and by the construction consortium on a continuous basis in the TBM service and running tunnels. Although chalk marl is nearly at the weakest end of the strength spectrum for rock (mean UCS ≈ 6 MPa), its distinctly bedded and jointed nature makes it quite amenable to classification by rock mass quality descriptors, such as the Q-system. The steeply dipping jointing and sub-horizontal bedding was Q-logged and photographed in the partly flooded Beaumont (Abbots Cliff) TBM tunnel, and in the Terlingham water tunnel, prior to Q-analysis of core logs and core box photographs from the PB series of eight marine core drillings. Mean Q-values were 3.4, 10.6 and 12.6 respectively. The Grey Chalk seen in the cliff exposures at Shakespeare indicated Q-values in the range 4–33. Jointing appears to have been similar in the significantly weaker underlying chalk marl, where permeabilities of about 1–20 Lugeons in an otherwise very impermeable matrix also indicated the presence of extensive jointing. The jointed and bedded nature of chalk marl, as experienced in the Beaumont, Terlingham and Channel Tunnels, resulted in a lot of distinctly discontinuous as opposed to continuum behaviour. Overbreak was marked where joint sets, bedding joints and an unfavourable tunnel direction combined to give the necessary degrees of freedom for block release. The inevitability of block release problems was increased by the relatively smooth and planar character of the joints and by the destabilising effect of high pore pressures in the case of the sub-sea sections of the Channel Tunnel having low rock cover and higher connectivity.

Keywords

Q-value Chalk marl Jointing, overbreak TBM Permeability P-wave velocity 

Notes

Acknowledgements

The work described in this chapter was performed for Geo-Engineering who were under contract for Eurotunnel. The permission of Eurotunnel and of Dr John Sharp of Geo-Engineering to publish this comprehensive analysis is gratefully acknowledged.

References

  1. Barton N (1993) Physical and discrete element models of excavation and failure in jointed rock. Keynote lecture. ISRM Int. Symp. on Assessment and Prevention of Failure Phenomena in Rock Engineering, Istanbul, TurkeyGoogle Scholar
  2. Barton N (1995) The influence of joint properties in modelling jointed rock masses. Keynote lecture. 8th ISRM Congress, Tokyo, vol 3. Balkema, Rotterdam, pp 1023–1032Google Scholar
  3. Barton N (2002) Some new Q-value correlations to assist in site characterization and tunnel design. Int J Rock Mech Min Sci 39(2):185–216CrossRefGoogle Scholar
  4. Barton N (2006) Rock quality, seismic velocity, attenuation and anisotropy. Taylor & Francis, Abingdon, p 729CrossRefGoogle Scholar
  5. Barton N (2007) Future directions for rock mass classification and characterization – towards a cross-disciplinary approach. Invited lecture. Proc. of 1st US-Canada Rock Mech. Symp., Vancouver, pp 179–188Google Scholar
  6. Barton N, Choubey V (1977) The shear strength of rock joints in theory and practice. In: Rock mechanics, vol 1/2. Springer, Vienna, pp 1–54Google Scholar
  7. Barton N, Grimstad E (1994) Rock mass conditions dictate choice between NMT and NATM. Tunnels & Tunnelling, October 1994, pp 39–42Google Scholar
  8. Barton N, Shen B (2017) Extension failure mechanisms explain failure initiation in deep tunnels and critical heights of cliff faces and near-vertical mountain walls. US Rock Mech. Symp. San Fransisco, ARMA17-686, 20pGoogle Scholar
  9. Barton N, Lien R, Lunde J (1974) Engineering classification of rock masses for the design of tunnel support. Rock Mech 6(4):189–236CrossRefGoogle Scholar
  10. Barton N, Grimstad E, Aas G, Opsahl ОA, Bakken A, Pedersen L, Johansen ED (1992a) Norwegian method of tunnelling. WT focus on Norway. World tunnelling. June/August 1992Google Scholar
  11. Barton N, Loset F, Smallwood A, Vik G, Rawlings C, Chryssanthakis P, Hansteen H, Ireland T (1992b) Geotechnical core characterization for the UK radioactive waste repository design. Proc. of ISRM Symp. EUROCK, Chester, UKGoogle Scholar
  12. Birch GP, Rankin WJ (1992) Geotechnical aspects of the UK undersee Crossover. Ch. 22. Proceedings of the Institution of Civil Engineers. The Channel TunnelGoogle Scholar
  13. Cundall P (1980) A generalized distinct element program for modelling jointed rock. Report PCAR-1-80. Contract DAJA37-79-C-0548, European Research Office, US Army. Peter Cundall AssociatesGoogle Scholar
  14. Eves RCW, Curtis DJ (1992) Tunnel lining design and procurement. Proceedings of the Institution of Civil Engineers. The Channel Tunnel. Part 1: Tunnels, pp 127–143Google Scholar
  15. Fugeman ICD, Hawley J, Meyers AG (1992) Major underground structures. Proceedings of the Institution of Civil Engineers. The Channel Tunnel, Part 1: Tunnels, pp 87–102Google Scholar
  16. Grimstad E, Barton N (1993) Updating of the Q-system for NMT. In: Kompen R, Opsahl OA, Berg K (eds) Proceedings of the International Symposium on Sprayed Concrete – Modern Use of Wet Mix Sprayed Concrete for Underground Support, Fagernes. Norwegian Concrete Association, OsloGoogle Scholar
  17. Makurat A, Barton N, Vik G, Chryssanthakis P, Monsen K (1990) Jointed rock mass modelling. International Symposium on Rock Joints. Loen 1990. Proceedings, pp 647–656Google Scholar
  18. Sharp JC, Warren CD, Barton NR, Mairwood R (1996) In: Harris CS, Hart MB, Varley PM, Warren CD (eds) Fundamental evaluations of the chalk marl for the prediction of UK marine tunnel stability and water inflows. Ch. 32 in Engineering Geology of the Channel Tunnel, pp 472–507Google Scholar
  19. Varley PM, Warren CD (1995) The channel tunnel project. Keynote lecture. GDF bulletin 11. Proc. XIth European Conf. of Soil Mech. and Found. Eng., CopenhagenGoogle Scholar
  20. Varley PM, Darby A, Radcliffe E (1992) Geology, alignment and survey. Proceedings of the Institution of Civil Engineers. The Channel Tunnel. Part 1: Tunnels, pp 43–54Google Scholar
  21. Warren CD, Varley PM, Parkin R (1992) UK tunnels: geotechnical monitoring and encountered conditions. Ch. 14. Proceedings of the Institution of Civil Engineers. The Channel TunnelGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2020

Authors and Affiliations

  • Nick Barton
    • 1
  • Colin Warren
    • 2
  1. 1.Nick Barton & Associates – Formerly Norwegian Geotechnical InstituteOsloNorway
  2. 2.Warren Geotechnical Associates, Surrey, UK – formerly Sir William Halcrow and PartnersLondonUK

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