Deformation analyses and plastic zone expansion in the tunnel Isfahan Golab 2 rock mass by convergence-confinement and numerical methods

Document Type : Research Paper

Authors

Abstract

In this study, analytical Duncan-Fama (DFM) and numerical finite difference (FDM) methods based on convergence-confinement (CCM) procedure was used to deformation analyses, stress field and plastic zone expansion estimation for rock mass of tunnel Golab 2 in Isfahan which simulated by RocSupport and FLAC2D softwares. The CCM approach utilizes ground response curves (GRC), longitudinal deformation profile (LDP), and support characteristic curves (SCC) to evaluate tunnel wall displacements and offer the most appropriate maintenance. The simulation is implemented for the most critical tunnel zones (zones 2 and 10 out of 15 zones) which generally consisting of shale with sandstone and siltstone geological units. In term of engineering geology and geomechanical studies, the zones have variable features and highly tectonised. This has a significant effect on the mechanical behavior of the geo-materials and causes squeezing on the support system. The geotechnical investigation results are shown that these zones (especially zone 10) have lowest strength mechanical parameters which main focus of this study is on these zones. Based on the analytical and numerical models were obtained for the 4 classes by CCM (GRC-SCC) curves for these intervals, it is found that these zones are under internal pressure about 7.56 and 4.18 MPa, respectively. Also, produce a plastic zone of about 2.85 and 2.88 meters. As results implementing maintenance structure with a permitted 10 mm displacement can reduce the plastic zone to 2.43 and 2.30 meters in the studied zones as well as provided structural stability in 15 mm. In conditional simulation, although the numerical method rather than analytical method is more falls and followed greater rigidity support system, but the CCM process is better suited to environmental conditions. On the other hand, by studying LDP-based behavioral diagrams, the estimated displacement is approximately the same for the short-term (7 days), mid-term (16 days), and long-term (24 days) intervals. As evaluating the in-situ stress field for zones 2 and 10, it was found that the stress field variations in zone 10 was sudden but zone 2 was followed by continuous deformation changes.

Keywords

References

آقانباتی، ع (1385) زمین­شناسی ایران، انتشارات سازمان زمین­شناسی و اکتشافات معدنی کشور، 807 ص.
شرکت مهندسین مشاور زایندآب (1388-الف)، طرح آبرسانی از اصفهان بزرگ به سد زاینده رود: گزارش زمین­شناسی مهندسی و ژئوتکنیک، 85 ص.
شرکت مهندسین مشاور زایندآب (1388-ب) طرح آبرسانی از اصفهان بزرگ به سد زاینده رود: گزارش زمین­شناسی عمومی، 120 ص.
نیکوبخت، ش (1392) بررسـی پارامـترهای توده­سنگ­های میزبان تونل انتقال آب گلاب 2 به منظور برآورد بار سنگ و طراحی سیستم نگهدارنده، پایان­نامه کارشناسی­­ارشد، دانشگاه یزد، 173 ص.
نیکوبخت، ش.، آذرافزا، م.، معماریان، ح.، مهرنهاد، ح (1393) برآورد میزان سختی و توان سایش­پذیری قطعات تشکیل دهنده کنگلومرایی در مسیر تونل انتقال آب گلاب 2 توسط آزمون سایش سورشار (CAI)، نشریه یافته­های نوین زمین­شنـاسی کاربـردی، جلد 9، شماره 17، ص. 16-24.
Alejano, L. R., Rodríguez-Dono, A., Alonso, E. and Fdez-Manín, G (2009) Ground reaction curves for tunnels excavated in different quality rock masses showing several types of post-failure behavior. Tunnelling and Underground Space Technology, 24(6): 689-705.
Brown, E. T., Bray, J. W., Ladanyi, B. and Hoek, E (1983) Ground response curves for rock tunnels, Journal of Geotechnical Engineering, 109(1): 15-39.
Cai, Y., Jiang, Y., Djamaluddin, I., Iura, T. and Esaki, T (2015) An analytical model considering interaction behavior of grouted rock bolts for convergence– confinement method in tunneling design, International Journal of Rock Mechanics and Mining Sciences, 76: 112-126.
Carranza-Torres, C. and Fairhurst, C (2000) Application of the convergence confinement method of tunnel design to rock masses that satisfy the Hoek Brown failure criterion, Tunnelling and Underground Space Technology, 15(2): 187-213.
Cui, L., Zheng, J., Zhang, R. and Lai, H (2015) A numerical procedure for the fictitious support pressure in the application of the convergence–confinement method for circular tunnel design. Int. International Journal of Rock Mechanics and Mining Sciences, 78: 336-349.
Duncan-Fama, M. E (1993) Numerical Modelling of Yield Zones in Weak Rocks, In: Hudson, J. A (ed.); Comprehensive Rock Engineering, Pergamon, Oxford, 49-75.
Fang, Q., Zhang, D., Zhou, P. and Wong, L. N. Y (2013) Ground reaction curves for deep circular tunnels considering the effect of ground reinforcement, International Journal of Rock Mechanics and Mining Sciences, 60: 401-412.
Fletcher, C. J. N (2016) Geology for Ground Engineering Projects, CRC Press, 309 p.
González-Cao, J., Varas, F., Bastante, F. G. and Alejano, L. R (2013) Ground reaction curves for circular excavations in non-homogeneous, axisymmetric strain-softening rock masses. Journal of Rock Mechanics and Geotechnical Engineering, 5(6): 431-442.
Itasca (2006) FLAC2D–Fast Lagrangian Analysis of Continua, Version 4.00, Itasca Consulting Group, Minneapolis, USA.
Janda, T., Šejnoha, M. and Šejnoha, J (2013) Modeling of soil structure interaction during tunnel excavation: An engineering approach. Advances in Engineering Software, 62(63): 51-60.
Mitchell, G (2014) Rheology: Theory, Properties and Practical Applications, Nova Science Pub Inc, 480 p.
Oke, J., Vlachopoulos, N. and Diederichs, M (2018) Improvement to the Convergence Confinement method: Inclusion of Support Installation Proximity and Stiffness. Rock Mechanics and Rock Engineering, 51(5): 1495-1519.
Oreste, P (2009) The convergence-confinement method: roles and limits in modern geomechanical tunnel design, American Journal of Applied Sciences, 6(4): 757-771.
Paraskevopoulou, C. and Diederichs, M (2018) Analysis of time-dependent deformation in tunnels using the Convergence-Confinement Method, Tunnelling and Underground Space Technology, 71: 62-80.
Rocscience (2010) RocSupport –Rock support interaction and deformation analysis for tunnels in weak rock, Version 3.0, Toronto, Canada.
Singh, B. and Goel, R. K (2011) Engineering Rock Mass Classification: Tunnelling, Foundations and Landslides, Butterworth-Heinemann, 384 p.
Vrakas, A (2017) A finite strain solution for the elastoplastic ground response curve in tunnelling: rocks with non-linear failure envelopes. International journal for numerical and analytical methods in geomechanics, 41(7): 1077-1190.
Vrakas, A. and Anagnostou, G (2014) A finite strain closed-form solution for the elastoplastic ground response curve in tunnelling. International journal for numerical and analytical methods in geomechanics, 38(11): 1131-1148.
Wang, S., Yin, X., Tang, H. and Ge, X (2010) A new approach for analyzing circular tunneling strain-softening rock masses. International Journal of Rock Mechanics and Mining Sciences, 47: 170-178.

Files

History

  • Receive Date: 02 August 2019
  • Revise Date: 11 October 2019
  • Accept Date: 30 October 2019

Share

How to cite

Statistics