The construction of a tunnel using EPB TBM generally induces short-term and long-term ground surface settlement. The short-term settlement is mainly caused by the relief of the in situ ground stress. Long-term settlement can be induced by the equilibration of the stresses and pore pressures in the clayey layer around the tunnel, which is associated with a new drainage condition imposed by the tunnel. It can also be caused by the creep behavior of the soft soil around the tunnel or in the soil layers. In this study, a series of FE analysis were conducted using PLAXIS 3D 2017 to investigate the long-term settlement induced in EPB shield tunneling cases in Taipei Mass Rapid Transit System (Taipei MRT). Various simulation were executed assessing the impact of consolidation on long-term settlement using Soft Soil (SS) and Hardening Soil Small-strain (HSS) Model. Simulation to assess the impact of the creep behavior of the soil on the long-term settlement was also executed using the Soft Soil Creep (SSC) Model. The constructions of the 2nd tunnel was simulated to investigate the increment of the ground surface settlement after the passage of the 2nd tunnel (Uptrack). In accordance with excavation sequence, the 2nd tunnel passes the monitoring section around the 300th day after the beginning of the tunnel construction. The volume loss is calculated via back analysis from the measured field data. The computed surface settlements were compared to the field measurement. From this study, it was found that the creep behavior of clay plays a vital role in quantifying the long-term surface settlement

The construction of a tunnel using EPB TBM generally induces short-term and long-term ground surface settlement. The short-term settlement is mainly caused by the relief of the in situ ground stress. Long-term settlement can be induced by the equilibration of the stresses and pore pressures in the clayey layer around the tunnel, which is associated with a new drainage condition imposed by the tunnel. It can also be caused by the creep behavior of the soft soil around the tunnel or in the soil layers. In this study, a series of FE analysis were conducted using PLAXIS 3D 2017 to investigate the long-term settlement induced in EPB shield tunneling cases in Taipei Mass Rapid Transit System (Taipei MRT). Various simulation were executed assessing the impact of consolidation on long-term settlement using Soft Soil (SS) and Hardening Soil Small-strain (HSS) Model. Simulation to assess the impact of the creep behavior of the soil on the long-term settlement was also executed using the Soft Soil Creep (SSC) Model. The constructions of the 2nd tunnel was simulated to investigate the increment of the ground surface settlement after the passage of the 2nd tunnel (Uptrack). In accordance with excavation sequence, the 2nd tunnel passes the monitoring section around the 300th day after the beginning of the tunnel construction. The volume loss is calculated via back analysis from the measured field data. The computed surface settlements were compared to the field measurement. From this study, it was found that the creep behavior of clay plays a vital role in quantifying the long-term surface settlement

REFERENCES
Addenbrooke, T.I., (1996). Numerical analysis of tunnels in stiff clay. PhD thesis,
Imperial College, University of London, UK.
Atkinson, J., & Cairncross, A. (1973). “Collapse of a shallow tunnel in a Mohr-Coulomb
material.” Paper presented at the proceedings of the Symposium of the Role of
Plasticity in Soil Mechanics, Cambridge, UK.
Atkinson, J.H. and Mair, R.J., (1981). Soil mechanics aspects of soft ground tunneling.
Ground Engineering, 14(5).
Attewell, P.B. and Woodman, J.P., (1982). Predicting the dynamics of ground settlement
and its derivatives caused by tunneling in soil. Ground engineering, 15(8).
Attewell, P.B., Yeates, J. and Selby, A.R., (1986). Soil movement induced by tunneling
and their effect on pipelines and structures. Blackie, Glasgow.
Bartlett, J.V and Bubbers, B.L., (1970). Surface movements caused by bored tunneling.
In Conference on Subway Construction (Vol. 539). sI]: Budapest-Balatofured.
Bowers, K. H., Hiller, M. D. & New, B. M. (1996). Ground movement over three years
at Heathrow Express trial tunnel. Proceedings of the International Symposium on
Geotechnical Aspects of Underground Construction in Soft Ground, London, pp.
557–562.
Broms, B. B., & Bennermark, H. (1967). “Stability of clay at vertical openings”. Journal
of Soil Mechanics & Foundations Div., ASCE, 193, SM1, 71-94.
Brinkgreve, R. et al. (Eds.), 2010. Plaxis 2D 2010 – User’s Manual. Plaxis BV,
Netherlands.
Brinkgreve, R., Engin E, Swolfs WM (2017) Plaxis 3D 2013 – User’s Manual. Delft,
Netherlands, PLAXIS.
Buismann, K., 1936. Results of long duration settlement test. In Proceedings 1st
International Conference on Soil Mechanics and Foundation Engineering, Volume
1, Cambridge, Massachusetts, pp. 103-107.
Butterfield, R., 1979. A natural compression law for soil (an advance on e-log p’)
(technical note). Geotechnique 29(4), 469-480.
Calvello, M., Finno, R., 2004. Selecting parameters to optimize in model calibration by
inverse analysis. Comp. Geotech. 31, 410–424.
Chi, S.Y., Chern, J.C., Lin C.C., 2001. Optimized back-analysis for tunneling-induced
ground movement using equivalent ground loss model. Tunn. Undergr. Sp.
Technol. 16, 159-165.
116
Clough, G. W., & Schmidt, B. (1981). “Design and performance of excavations and
tunnels in soft clay”. In Soft Clay Engineeing, Elsevier, 569-643.
Cording, E.J., Hansmire, W.H., 1975. Displacement around soft ground tunnels. General
Report: Session IV, Tunnels in soil, Proceedings of the 5th Pan American
Conference on Soil Mechanics and Foundation Engineering, pp. 571-632.
Craig, R.N. and Muir Wood, A. M., (1978). A review of tunnel lining practice in the
United Kingdom. Supplm. 335, Transport and road Research Laboratory.
Davis, E., Gunn, M., Mair, R., & Seneviratine, H. (1980). “The stability of shallow
tunnels and underground opening in cohesive material”. Geotechnique, 30(4), 397-
416.
Fattah, M.Y., Shlash, K.T. and Salim, N.M., (2013). Prediction of settlement trough
induced by tunneling in cohesive ground. Acta Geotechnica, 8(2), pp. 167-179.
Guglielmetti, V., Grasso, P., Mahtab, A., & Xu, S. (Eds.). (2008). “Mechanized tunneling
in urban areas: design methodology and construction control”. Taylor and Francis.
Ch. 5.
Janbu, N. (1985). 25th rankine lecture: Soil models in offshore engineering. Geotechnique
35(3), 239-281.
Khoiri, M., Ou, C.Y. (2013). Evaluation of deformation parameter for deep excavation in
sand through case histories. Computer and Geotechnics, 47(1), 57 – 67.
Leca, E., Leblais, Y. and Kuhnhenn, K., (2000). Underground works in the soils and soft
rocks tunneling. In ISRM International Symposium. International Society for Rock
Mechanics.
Lee, S.H.H., 1990. Regression models of shear wave velocity. J. Chinese Eng., 13 (5),
519-532.
Lee, K.M., Rowe, R.K., 1991. An analysis of three-dimensional ground movement: the
Thunder Bay tunnel. Can. Geotech. J. 28 (1), 25-41.
Lee, K.M., Rowe, R.K., Lo, KY., 1992. Subsidence owing to tunneling. I: Estimating the
gap parameter. Can. Geotech. J. 29, 929-940.
Lim, A., Ou, C.Y., Hsieh, P.G., 2010. Evaluation of clay constitutive models for analysis
of deep excavation under undrained conditions. J. GeoEng. 5, 9-20.
Lim, A., Ou, C.Y., 2017. Stress paths in deep excavation under undrained conditions and
its influence on deformation analysis. Tunn. Undergr. Sp. Technol. 63, 118-132.
Lin, H. D., Wang, C. C. (1998). Stress-strain-time function of clay. J. Geotech.
Geoenviron. Eng, ASCE, 124(4): 289-296.
117
Kuesel, T.R., King, E.H, & Bickel, J. O. (2012). Tunnel engineering handbook. Springer
Science & Business Media.
Mair, R.J. (1979). “Centrifugal modelling of tunnel construction in soft clay”. PhD thesis.
University of Cambridge, Cambridge, UK.
Mair, R.J., 2008. Tunnelling and geotechnics: new horizons. Geotechnique 58 (9), 695-
736.
Mair, R.J., Taylor, R.N., 1997. Bored tunneling in urban environment: state-of-the-art
report and theme lecture. Proc. 14th Int. Conf. Soil Mech. Found. Engng, Hamburg
4, 2353-2385.
Martos, F. (1958). “Concerning an approximate equation of the subsidence trough and its
time factors”. In Internation strata control congress, Leipzig, 191-205.
Ng, C.W., Simons, N.E. and Menzies, B.K., (2004). A short course in soil-structure
engineering of deep foundations, excavations and tunnels. Thomas Telford.
O’Reilly, M.P., New, B.M., 1982. Settlements above tunnels in the United Kingdom:
their magnitude and prediction. In: Tunnelling ’82: 3rd International Symposium,
Brighton, East Sussex, United Kingdom, pp. 225-289.
Ou, C.Y., Chin, C.K., Liu, C.C., 2009. Development of time dependent stress-strain
simulation of clay. Journal of Mechanics. 25 (1), pp. 27-40.
Ou, C.Y. (2006) Deep Excavation: Theory and Practice. Taylor and Francis: London
Ou, C.Y., Chin, C.K., Liu, C.C., 2011. Anisotropic viscoplastic modeling of ratedependent
behavior of clay. Int. J. Numer. Anal. Meth. Geomech. 35 (11), pp. 1189
-1206.
Peck, R.B., 1969. Deep excavation and tunneling in soft ground. Proceedings of 7th
International Conference Soil Mechanics and Foundation Engineering. Mexico,
State of the Art Volume, pp. 225-290.
Romo, M.P. and Diaz, M., (1981). Face stability and ground settlement in shield
tunneling. In Proceedings of the 10th International conference on Soil Mechanics
and Foundation Engineering, Stockholm.
Rowe, R.K., Lo, K.Y., Kack, G.J., 1983. A method of estimating surface settlement above
tunnels construction in soft ground. Can. Geotech. J. 20 (8), 11-22.
Sagaseta, C., 1987. Analysis of undrained soil deformation due to ground loss.
Geotechnique 37 (3), 301-320.
Sagaseta, C., 1988. Discussion on: Segeseta, C.: Analysis of undrained soil deformation
due to ground loss. Author’s replay to B. Schmidt. Geotechnique 38 (4), 647-649.
Schanz, T., Vermeer, P.A., Bonnier, P.G., 1999. The hardening soil model: formulation
and verification. In: Beyond 2000 in Computational Geotechnics – 10 Years Plaxis.
Rotterdam, pp. 281–296.Senevirtne, H. (1979). “Deformation and pore-pressures
118
around model tunnels in soft clay”. Ph.D. thesis, University of Cambridge,
Cambridge, UK.
Shin, J.H., Potts, D.M., 2003. Time-base two-dimensional modelling of NATM
tunneling. Can. Geotech. J. 39 (3), 710-724.
Shin, J.H., Addenbrooke, T.I., Potts, D.M., 2002. A numerical study of the effect of
groundwater movement on the long-term tunnel behavior. Geotechnique 58 (6),
391-403.
Surarak C., Likitlersuang S., Wanatowski D., Balasubramaniam A., Oh, E., Guan H.
(2012). Stiffness and strength parameter for hardening soil model of soft and stiff
Bangkok Clays. Soils and Foundations, 52(4), 682-697.
Stallebrass, S.E., Jovicic, V., Taylor, R.N. (1994). Short-term and long-term settlements
around tunnel in stiff clay. In Numerical Methods in Geotechnical Engineering (ed.
I. M. Smith), pp. 235-240. Rotterdam, the Netherland: Balkema.
Teng, F.C., 2010. Prediction of Ground Movement Induced by Excavation Using the
Numerical Method with Consideration of Inherent Stiffness Anisotropy
(Dissertation). National Taiwan University of Science and Technology.
Uriel, A.O., Segeseta, C., 1989. Selection for design parameters for underground
construction. In Proceedings of the 2nd Conference on Ground Movement and
Structures. Cardiff, Wales. Pp. 331-344.
Vorster, T. E. B., Klar, A., Soga, K. & Mair, R. J. (2005). Estimating the effect of
tunneling on existing pipelines. J. Geotech. Geoenviron. Engng ASCE 131, No. 11,
1399–1410.
Wang, Z., Wong, R.C.K., Li, S., Qiao, L., 2012. Finite element analysis of long-term
surface settlement above a shallow tunnel in soft ground. Tunn. Undergr. Sp. Technol.
30, 85-92.
Ward, W., & Pender, M. (1981). “Tunneling in soft ground: general report”. Paper
presented at the Proceeding of the 10th International Conference of Soil Mechanics
and Foundation Engineering, Stockholm.
Wong, R.C.K., Kaiser, P.K., 1991. Performance assessment of tunnels in cohensionless
soils. J. Geotech. Eng. 117(2), 1880-1901.