BTS | HARDING PRIZE COMPETITION 2023


reason for the different impact of the bolt preload


is that, under negative bending, the three bolts of the joint are engaged concurrently, whereas under positive bending the middle bolt is only engaged once the two outer bolts have failed in tension. In short, the numerical results indicate that tightening the bolts might be an effective measure for stiffening a tunnel ring only when the latter is to be subjected to loading conditions where the joints open under negative bending.


CONCLUSIONS This paper summarises recent developments in the structural assessment of GCI tunnel linings. A new methodology, based on bending stiffness


reduction factors, allowing the influence of longitudinal joints to be incorporated in simple structural assessments was introduced first. Upper and lower bound reduction factors were proposed along with a global factor representative of the average stiffness reduction taking place around the ring. These factors varied with the tunnel ovalisation, tunnel depth and the adopted soil-tunnel interface condition. They were presented in the form of design charts allowing their application in engineering practice. The rotational behaviour of longitudinal tunnel joints was extensively investigated subsequently. The main


outcome of the investigation was the derivation of a set of M-θ curves corresponding to different compression levels for each bending mode. The novel characterisation of the M-θ response informed the development of a new joint model allowing the nonlinear behaviour of segmental GCI linings to be simulated in numerical geotechnical analysis. Additional studies revealed that removing the bolts


from the joint can prevent tensile failure of GCI under positive bending and that a larger bolt preload only increases the joint stiffness significantly under negative bending. These insights can be considered when deciding


about potential protective measures of existing tunnels subjected to new solicitations.


ACKNOWLEDGEMENTS I would like to thank my PhD supervisors Dr. Katerina Tsiampousi and Prof. Jamie Standing for their guidance and support in conducting the research discussed here. I would also like to thank Prof. David Potts for his help with some of the computational aspects of the project. The PhD project was funded by EPSRC through


a Doctoral Training Grant (EP/R512540/1), and their support is greatly acknowledged.


REFERENCES ● Afshan, S., Yu, J., Standing, J., Vollum, R., & Potts, D. (2017). Ultimate


capacity of a segmental grey cast iron tunnel lining ring subjected to large deformations. Tunnelling and Underground Space Technology, 64, 74–84


● Duddeck, H. & Erdmann, J. (1985). Structural design models for tunnels in soft soil. Underground Space; (United States), 9


● Kimmance, J. P., Lawrence, S., Hassan, O., Purchase, N. J. & Tollinger, G. (1996) Observations of deformations created in existing tunnels by adjacent and cross cutting excavations. In: Mair, R. J. & Taylor, R. N. (eds.) Geotechnical Aspects of Underground Construction in Soft Ground: Proceedings of the International Symposium. Taylor Francis Group, Rotterdam, pp. 707-712


● Li, Z., Soga, K., Wang, F., Wright, P., & Tsuno, K. (2014). Behaviour of cast-iron tunnel segmental joint from the 3D FE analyses and development of a new bolt-spring model. Tunnelling and Underground Space Technology, 41, 176–192


● Moss, N. & Bowers, K. (2005). The effect of new tunnel construction under existing metro tunnels. Geotechnical Aspects of Underground Construction in Soft Ground. Amsterdam: Taylor and Francis, (pp. 151–157)


● Muir Wood, A. (1975). The circular tunnel in elastic ground. Géotechnique, 25(1), 115–127


● Potts, D. M. & Zdravkovic, L. (1999). Finite element analysis in geotechnical engineering: theory, volume 1. Thomas Telford


● Ruiz López, A. (2022). Development of advanced numerical models for grey cast iron tunnel linings. PhD thesis, Imperial College London


● Ruiz López, A., Tsiampousi, A., Standing, J. R., & Potts, D. M. (2022). Numerical investigation of a segmental grey cast iron tunnel ring:


validation with laboratory data and application to field conditions. Computers and Geotechnics, 141, 104427


● Ruiz López, A., Tsiampousi, A., Standing, J. R., & Potts, D. M. (2023a). Numerical characterisation of the rotational behaviour of grey cast iron tunnel joints. Computers and Geotechnics, 159, 105460.


● Ruiz López, A., Tsiampousi, A., Standing, J. R., & Potts, D. M. (2023b). A new model for simulating the behaviour of grey cast iron tunnel joints with structural elements. Submitted for publication


● TfL (2017). Civil Engineering - Deep Tube Tunnels and Shafts. Standard S1055 A5. Technical report


● Thomas, H. (1977). Measuring the structural performance of cast iron tunnel linings in the laboratory. Ground Engineering, 10(5)


● Tsiampousi, A., Yu, J., Standing, J., Vollum, R., & Potts, D. (2017). Behaviour of bolted cast iron joints. Tunnelling and Underground Space Technology, 68, 113–129


● Tube Lines (2007). Soil Parameters Report. Deep Tube Tunnel Knowledge and Inspection Programme Annual Works Plan 2. Revision 3 issued on 9/7/2007. Technical report, TLL-L001-N416-DTAAWP2-TUN- RPT-00001


● Wright, P. J. (2013). Validation of soil parameters for deep tube tunnel assessment. Proceedings of the Institution of Civil Engineers- Geotechnical Engineering, 166(1), 18–30


● Yu, J. B. Y. (2014). Assessing ground interaction effects and potential damage on existing tunnels before and after new excavation works. PhD thesis, Imperial College London


● Yu, J., Standing, J., Vollum, R., Potts, D., & Burland, J. (2017). Experimental investigations of bolted segmental grey cast iron lining behaviour. Tunnelling and Underground Space Technology, 61, 161–178


38 | July 2023


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  |  Page 50  |  Page 51  |  Page 52  |  Page 53