Geomechanics and Engineering

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Numerical analysis and stability assessment of complex secondary toppling failures: A case study for the south pars special zone

  • Azarafza, Mohammad (Department of Civil Engineering, University of Tabriz) ;
  • Bonab, Masoud Hajialilue (Department of Civil Engineering, University of Tabriz) ;
  • Akgun, Haluk (Geotechnology Unit, Department of Geological Engineering, Middle East Technical University (METU))
  • Received : 2021.05.13
  • Accepted : 2021.11.10
  • Published : 2021.12.10
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Abstract

This article assesses and estimates the progressive failure mechanism of complex pit-rest secondary toppling of slopes that are located within the vicinity of the Gas Flare Site of Refinery No. 4 in South Pars Special Zone (SPSZ), southwest Iran. The finite element numerical procedure based on the Shear Strength Reduction (SSR) technique has been employed for the stability analysis. In this regard, several step modelling stages that were conducted to evaluate the slope stability status revealed that the main instability was situated on the left-hand side (western) slope in the Flare Site. The toppling was related to the rock column-overburden system in relation to the overburden pressure on the rock columns which led to the progressive instability of the slope. This load transfer from the overburden has most probably led to the separation of the rock column and to its rotation downstream of the slope in the form of a complex pit-rest secondary toppling. According to the numerical modelling, it was determined that the Strength Reduction Factor (SRF) decreased substantially from 5.68 to less than 0.320 upon progressive failure. The estimated shear and normal stresses in the block columns ranged from 1.74 MPa to 8.46 MPa, and from 1.47 MPa to 16.8 MPa, respectively. In addition, the normal and shear displacements in the block columns ranged from 0.00609 m to 0.173 m and from 0.0109 m to 0.793 m, respectively.

Keywords

Acknowledgement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors wish to thank the Department of Civil Engineering, University of Tabriz for giving permission to conduct the geomechanical laboratory tests.

References

  1. Adhikary, D.P., Dyskin, A.V. and Jewell, R.J. (1997), "A study of the mechanism of flexural toppling failure of rock slopes", Rock Mech. Rock Eng., 30(2), 75-93. https://doi.org/10.1007/BF01020126.
  2. Aghanabati, A. (2007), Geology of Iran, Geological Survey of Iran press, Tehran, Iran.
  3. Alejano, L.R., Carranza-Torres, C., Giani, G.P. and Arzua, J. (2015), "Study of the stability against toppling of rock blocks with rounded edges based on analytical and experimental approaches", Eng. Geol., 195, 172-184. https://doi.org/10.1016/j.enggeo.2015.05.030.
  4. Alejano, L.R., Ferrero, A.M., Ramirez-Oyanguren, P. and Alvarez Fernandez, M.I. (2011), "Comparison of limit-equilibrium, numerical and physical models of wall slope stability", Int. J. Rock Mech. Min. Sci., 48(1), 16-26. https://doi.org/10.1016/j.ijrmms.2010.06.013.
  5. Alejano, L.R., Gomez Marquez, I., Pons, B., Garcia Bastante, F. and Alonso, E. (2006), "Stability analysis of a potentially toppling over-tilted slope in granite", Proceedings of the 4th Asian Rock Mechanics Symposium, Singapore, November.
  6. Alejano, L.R., Gomez-Marquez, I. and Martinez-Alegria, R. (2010), "Analysis of a complex toppling-circular slope failure", Eng. Geol., 114(1-2), 93-104. https://doi.org/10.1016/j.enggeo.2010.03.005.
  7. Alejano, L.R., Sanchez-Alonso, C., Perez-Rey, I., Arzua, J., Alonso, E. and Gonzalez, J. (2018). "Block toppling stability in the case of rock blocks with rounded edges", Eng. Geol., 234, 192-203. https://doi.org/10.1016/j.enggeo.2018.01.010.
  8. Amini, M. and Ardestani, A. (2019). "Stability analysis of the north-eastern slope of Daralou copper open pit mine against a secondary toppling failure", Eng. Geol., 249, 89-101. https://doi.org/10.1016/j.enggeo.2018.12.022.
  9. Amini, M., Ardestani, A. and Khosravi, M.H. (2017), "Stability analysis of slide-toe-toppling failure", Eng. Geol., 228, 82-96. https://doi.org/10.1016/j.enggeo.2017.07.008
  10. Amini, M., Gholamzadeh, M. and Khosravi, M.H. (2015), "Physical and theoretical modeling of rock slopes against block-flexure toppling failure", Int. J. Min. Geo-Eng., 49(2), 155-171. https://doi.org/10.22059/IJMGE.2015.56103.
  11. Amini, M., Majdi, A. and Aydan, O. (2009), "Stability analysis and the stabilisation of flexural toppling failure", Rock Mech. Rock Eng., 42(5), 751-782. https://doi.org/10.1007/s00603-008-0020-2.
  12. Amini, M., Majdi, A. and Veshadi, M.A. (2012), "Stability analysis of rock slopes against block flexure toppling failure", Rock Mech. Rock Eng., 45(4), 519-532. https://doi.org/10.1007/s00603-012-0220-7.
  13. Amini, M., Sarfaraz, H. and Esmaeili, K. (2018), "Stability analysis of slopes with a potential of slide-head toppling failure", Int. J. Rock Mech. Min. Sci., 112, 108-121. https://doi.org/10.1016/j.ijrmms.2018.09.008.
  14. Ardestani, A., Amini, M. and Esmaeili, K. (2021), "A two-dimensional limit equilibrium computer code for analysis of complex toppling slope failures", J. Rock Mech. Geotech. Eng., 13(1), 114-130. https://doi.org/10.1016/j.jrmge.2020.04.006.
  15. Asadi, M. and Ashtiani, R.S. (2018), "Stability analysis of anisotropic granular base layers in flexible pavements". Transport. Geotech., 14, 183-189. https://doi.org/10.1016/j.trgeo.2018.01.001.
  16. Ashby, J. (1971), "Sliding and toppling modes of failure in models and jointed rock slopes" MSc Dissertation, Imperial College, London.
  17. ASTM D5607 (2002), Performing Laboratory Direct Shear Strength Tests of Rock Specimens under Constant Normal Force, ASTM International, West Conshohocken, PA, USA.
  18. ASTM D6473 (2015), Standard Test Method for Specific Gravity and Absorption of Rock for Erosion Control, ASTM International, West Conshohocken, PA, USA.
  19. ASTM D7012 (2014), Standard Test Methods for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures, ASTM International, West Conshohocken, PA, USA.
  20. Aydan, O. and Amini, M. (2009), "An experimental study on rock slopes against flexural toppling failure under dynamic loading and some theoretical consideration for its stability assessment", J. School Marine Sci. Technol. Tokai Univ., 7(2), 25-40.
  21. Aydan, O. and Kawamoto, T. (1992), "The stability of slopes and underground openings against flexural toppling and their stabilisation", Rock Mech. Rock Eng., 25(3), 143-165. https://doi.org/10.1007/BF01019709.
  22. Azarafza, M., Akgun, H., Ghazifard, A. and Asghari-Kaljahi, E. (2020), "Key-block based analytical stability method for discontinuous rock slope subjected to toppling failure", Comput. Geotech., 124, 103620. https://doi.org/10.1016/j.compgeo.2020.103620.
  23. Azarafza, M., Asghari-Kaljahi, E. and Moshrefy-far, M.R. (2014), "Determination of geomechanical parameters of mass structure of gas Flare site in 6, 7 and 8 phases of South Pars Gas Complex", Proceedings of the 2th National & 1st International Geosciences Congress of Iran, Sari, Iran, February.
  24. Azarafza, M., Asghari-Kaljahi, E., Ghazifard, A. and Akgun, H. (2021), "Application of fuzzy expert decision-making system for rock slope block-toppling modeling and assessment: a case study", Model. Earth Syst. Environ., 7, 159-168. https://doi.org/10.1007/s40808-020-00877-9.
  25. Azarafza, M., Ghazifard, A., Akgun, H. and Asghari-Kaljahi, E. (2019), "Geotechnical characteristics and empirical geoengineering relations of the South Pars Zone marls, Iran", Geomech. Eng., 19(5), 393-405. https://doi.org/10.12989/gae.2019.19.5.393.
  26. Azarafza, M., Ghazifard, A., Akgun, H. and Asghari-Kaljahi, E. (2018), "Landslide susceptibility assessment of South Pars Special Zone, southwest Iran", Environ. Earth Sci., 77, 805. https://doi.org/10.1007/s12665-018-7978-1.
  27. Babiker, A.F.A., Smith, C.C., Gilbert, M. and Ashby, J.P. (2014), "Non-associative limit analysis of the toppling-sliding failure of rock slopes", Int. J. Rock Mech. Min. Sci., 71, 1-11. https://doi.org/10.1016/j.ijrmms.2014.06.008.
  28. Basahel, H. and Mitri, H. (2017), "Application of rock mass classification systems to rock slope stability assessment: A case study", J. Rock Mech. Geotech. Eng., 9(6), 993-1009. https://doi.org/10.1016/j.jrmge.2017.07.007.
  29. Bobet, A., Fakhimi, A., Johnson, S., Morris, J., Tonon, F. and Yeung, M.R. (2009), "Numerical models in discontinuous media: Review of advances for rock mechanics applications", J. Geotech. Geoenviron. Eng., 135(11), 1547-1561. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000133.
  30. Brideau, M.A. and Stead, D. (2010), "Controls on block toppling using a three-dimensional distinct element approach", Rock Mech. Rock Eng., 43(3), 241-260. https://doi.org/10.1007/s00603-009-0052-2.
  31. Bukovansky, M., Rodriguez, M.A. and Cedrun, G. (1976), "Three rock slides in stratified and jointed rocks", In: Proceedings of the 3rd Congress International Society for Rock Mechanics, Denver, Colorado, IIB, 854-858.
  32. Chen, X., Zhang, L., Chen, L., Li, X. and Liu, D. (2019), "Slope stability analysis based on the Coupled Eulerian-Lagrangian finite element method", Bull. Eng. Geol. Environ., 78, 4451-4463. https://doi.org/10.1007/s10064-018-1413-4.
  33. Cundall, P. (1971), "A computer model for simulating progressive, large scale movements in blocky rock systems", Proceedings of the International Symposium on Rock Fracture, Nancy, France, October.
  34. Dawson, E.M., Roth, W.H. and Drescher, A. (1999), "Slope stability analysis by strength reduction", Geotechnique, 49(6), 835-840. https://doi.org/10.1680/geot.1999.49.6.835.
  35. de-Freitas, M.H. and Watters, R.J. (1973), "Some field examples of toppling failure", Geotechnique, 23, 495-514. https://doi.org/10.1680/geot.1973.23.4.495.
  36. El-Amrani Paaza, N., Lamas, F., Irigaray, C. and Chacon, J. (1998), "Engineering geological characterization of Neogene marls in the Southeastern Granada Basin (Granada, Spain)", Eng. Geol., 50(1-2), 165-175. https://doi.org/10.1016/S0013-7952(98)00008-8.
  37. Erguvanli, K. and Goodman, R.E. (1972), "Applications of models to engineering geology for rock excavations", Bull. Assoc. Eng. Geol., 9.
  38. Ernst, W.G. (2006), "Preservation/exhumation of ultrahigh-pressure subduction complexes", Lithos., 92(3-4), 321-335. https://doi.org/10.1016/j.lithos.2006.03.049.
  39. Evans, R.S. (1981), "An analysis of secondary toppling rock failures-the stress redistribution method", Q. J. Eng. Geol. Hydrogeol., 14, 77-86. https://doi.org/10.1144/GSL.QJEG.1981.014.02.01.
  40. Geological Survey of Iran, GSI (2009), Geological map of Kangan and Assalouyeh-scale and geological reports, Geological Survey of Iran Press, Tehran [in Persian]
  41. Goodman, R.E. and Bray, J.W. (1976), "Toppling of rock slopes", Proceedings of the ASCE Specialty Conference on Rock Engineering for Foundations and Slopes, 2, 201-234.
  42. Griffiths, D.V. and Lane, P.A. (1999), "Slope stability analysis by finite elements", Geotechnique, 49(3), 387-403. https://doi.org/10.1680/geot.1999.49.3.387.
  43. Haghgouei, H., Kargar, A.R., Amini, M. and Esmaeili, K. (2020), "An analytical solution for analysis of toppling slumping failure in rock slopes", Eng. Geol., 265, 105396. https://doi.org/10.1016/j.enggeo.2019.105396.
  44. Hammah, R.E., Curran, J.H., Yacoub, T. and Corkum, B. (2004), "Stability analysis of rock slopes using the finite element method", Proceedings of the EUROCK 2004 & 53rd Geomechanics Colloquium, Salzburg, October.
  45. Hammah, R.E., Yacoub, T.E., Corkum, B.C. and Curran, J.H. (2005), "The Shear Strength Reduction Method for the Generalized Hoek-Brown Criterion", Proceedings of the 40th U.S. Symposium on Rock Mechanics (USRMS): Rock Mechanics for Energy, Mineral and Infrastructure Development in the Northern Regions, Alaska, June.
  46. Havaej, M., Stead, D., Eberhardt, E. and Fisher, B.R. (2014), "Characterization of bi-planar and ploughing failure mechanisms in footwall slopes using numerical modelling", Eng. Geol., 178(16), 109-120. https://doi.org/10.1016/j.enggeo.2014.06.003.
  47. Hoek, E., Carranza-Torres, C. and Corkum, B. (2002), "Hoek-Brown failure criterion - 2002 edition", Proceedings of the NARMS-TAC Conference, 267-273. Toronto, July.
  48. Hoffmann, H. (1974), "Zum Verformungs und Bruchverhalten regelmaβig geklufteter Felsboschungen", Rock Mech., 3, 31-34.
  49. Hudson, J.A. and Harrison, J.P. (1997), Engineering Rock Mechanics: An Introduction to the Principles, Elsevier Science, Amsterdam, Netherlands.
  50. Jing, L. (2003), "A review of techniques, advances and outstanding issues in numerical modelling for rock mechanics and rock engineering", Int. J. Rock Mech. Min. Sci., 40(3), 283-353. https://doi.org/10.1016/S1365-1609(03)00013-3.
  51. Jing, L. and Hudson, J.A. (2002), "Numerical methods in rock mechanics", Int. J. Rock Mech. Min. Sci., 39(4), 409-427. https://doi.org/10.1016/S1365-1609(02)00065-5.
  52. Jing, L. and Stephansson, O. (2007), Fundamentals of Discrete Element Methods for Rock Engineering: Theory and Applications, Elsevier Science, Amsterdam, Netherlands.
  53. Labuz, J.F. and Zang, A. (2012), "Mohr-Coulomb Failure Criterion", Rock Mech. Rock Eng., 45, 975-979. https://doi.org/10.1007/s00603-012-0281-7.
  54. Lamas, F., Irigaray, C. and Chacon, J. (2002), "Geotechnical characterization of carbonate marls for the construction of impermeable dam cores", Eng. Geol., 66(3-4), 283-294. https://doi.org/10.1016/S0013-7952(02)00048-0.
  55. Ledesma, O., Mendive, I. and Sfriso, A. (2016), "Factor of Safety by the Strength-Reduction Technique Applied to the Hoek - Brown Model", SRK Consulting Press, ENIEF 2016, 1-24.
  56. Lin, S., Su, Z., Li, M. and Shao, L. (2020), "Slope stability analysis using elastic finite element stress fields", Eng. Geol., 273, 105673. https://doi.org/10.1016/j.enggeo.2020.105673.
  57. Liu, F. (2020), "Stability Analysis of Geotechnical Slope Based on Strength Reduction Method", Geotech. Geol. Eng., 38, 3653-3665. https://doi.org/10.1007/s10706-020-01243-3.
  58. Lu, X., Su, Z., Huang, M. and Zhou, Y. "Strength reduction finite element analysis of a stability of large cross-river shield tunnel face with seepage", Europ. J. Environ. Civil Eng., 24(3), 336-353. https://doi.org/10.1080/19648189.2017.1383942.
  59. Majdi, A. and Amini, M. (2011), "Analysis of geo-structural defects in flexural toppling failure", Int. J. Rock Mech. Min. Sci., 48, 175-186. https://doi.org/10.1016/j.ijrmms.2010.11.007.
  60. Maji V.B. (2017), "An insight into slope stability using strength reduction technique", J. Geol. Soc. India, 89, 77-81. https://doi.org/0016-7622/2017-89-1-77. https://doi.org/10.1007/s12594-017-0561-7
  61. Meng, Q.X., Wang, H.L., Xu, W.Y., Cai, M., Xu, J. and Zhang, Q. (2019), "Multiscale strength reduction method for heterogeneous slope using hierarchical FEM/DEM modelling", Comput. Geotech., 115, 103164. https://doi.org/10.1016/j.compgeo.2019.103164.
  62. Mohtarami, E., Jafari, A. and Amini, M. (2014), "Stability analysis of slopes against combined circular-toppling failure", Int. J. Rock Mech. Min. Sci., 67, 43-56. https://doi.org/10.1016/j.ijrmms.2013.12.020.
  63. Muller, L. (1964), "The rock slide in the Vajont valley", Rock Mech. Eng. Geol., 2, 148-212.
  64. Nichol, S.L., Hungr, O. and Evans, S.G. (2002), "Large-scale brittle and ductile toppling of rock slopes", Canad. Geotech. J., 39(4), 773-788. https://doi.org/10.1139/t02-027.
  65. Nikoobakht, S. and Azarafza, M. (2016), "Stability analysis and numerical modelling of toppling failure of discontinuous rock slope (A Case study)", J. Geotech. Geol., 12(2), 169-178.
  66. Nogol-Sadat, M.A. and Almasian, A. (1993), Tectonic Map of Iran 1:1,000,000 Treatise on the Geology Of Iran, Geological Survey of Iran, Tehran, Iran.
  67. Rocscience (2016), DIPS software, (Version 7.0) - Stereographic projection program; Rocscience Inc., Toronto, Canada. https://www.rocscience.com/
  68. Rocscience (2017), RocLab software - A program for determining rock mass strength parameters; Rocscience Inc., Toronto, Canada. https://www.rocscience.com/
  69. Rocscience (2019), Phase2 software, (Version 8.0) - 2D finite element stress analysis program for designing underground or surface excavations and their support systems; Rocscience Inc., Toronto, Canada. https://www.rocscience.com/
  70. Sageseta, C., Sanchez, J.M. and Canizal, J. (2001), "A general analytical solution for the required anchor force in rock slopes with toppling failure", Int. J. Rock Mech. Min. Sci., 38, 421-435. https://doi.org/10.1016/S1365-1609(01)00011-9.
  71. Sahraeyan, M., Bahrami, M. and Hejazi, S.H. (2013), "The Aghajari (Upper Fars) formation in the folded Zagros zone, Iran: insights to identify facies, architectural elements, fluvial systems, petrography and provenance", Acta Geol. Sin., 87(4), 1019-1031. https://doi.org/10.1111/1755-6724.12107.
  72. Sarfaraz, H., Khosravi, M.K. and Amini, M. (2019), "Numerical analysis of slide-head-toppling failure", J. Min. Environ., 10(4), 1001-1011. https://doi.org/10.22044/JME.2019.8521.1731.
  73. Sari, M. (2019), "Stability analysis of cut slopes using empirical, kinematical, numerical and limit equilibrium methods: case of old Jeddah-Mecca road (Saudi Arabia)", Environ. Earth Sci., 78(21), 621. https://doi.org/10.1007/s12665-019-8573-9.
  74. Shen, J. and Karakus, M. (2014), "Three-dimensional numerical analysis for rock slope stability using shear strength reduction method", Canad. Geotech. J., 51(2), 164-172. https://doi.org/10.1139/cgj-2013-0191.
  75. Smith, J.V. (2015), "Self-stabilization of toppling and hillside creep in layered rocks", Eng. Geol., 196, 139-149. https://doi.org/10.1016/j.enggeo.2015.07.008.
  76. Song, S., Cai, D., Feng, X., Chen, X. and Wang, D. (2011), "Safety monitoring and stability analysis of left abutment slope of Jinping I hydropower station", J. Rock Mech. Geotech. Eng., 3(1), 117-130. https://doi.org/10.3724/SP.J.1235.2011.00117.
  77. Spreafico, M.C., Cervi, F., Francioni, M., Stead, D. and Borgatti, L. (2017), "An investigation into the development of toppling at the edge of fractured rock plateaux using a numerical modelling approach", Geomorphology, 288, 83-98. https://doi.org/10.1016/j.geomorph.2017.03.023.
  78. Sun, C., Chen, C., Zheng, Y. and Xia, K. (2020), "A limit equilibrium analysis of the stability of a footwall slope with respect to bi-planar failure", Int. J. Geomech., 20(1), 04019137. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001523.
  79. Sun, C., Chen, C., Zheng, Y., Xia, K. and Zhang, W. (2018), "Topping failure analysis of anti-dip bedding rock slopes subjected to crest loads", Int. J. Geotech. Geol. Eng., 12(11), 685-693.
  80. Sun, G., Lin, S., Zheng, H., Tan, Y. and Sui, T. (2020), "The virtual element method strength reduction technique for the stability analysis of stony soil slopes", Comput. Geotech., 119, 103349. https://doi.org/10.1016/j.compgeo.2019.103349.
  81. Tang, C., Li, L., Xu, N. and Ma, K. (2015), "Microseismic monitoring and numerical simulation on the stability of high-steep rock slopes in hydropower engineering", J. Rock Mech. Geotech. Eng., 7(5), 493-508. https://doi.org/10.1016/j.jrmge.2015.06.010.
  82. Toussaint, G., Burov, E. and Avouac, J.P. (2004), "Tectonic evolution of a continental collision zone: A thermomechanical numerical model", Tectonics, 23(6), TC6003. https://doi.org/10.1029/2003TC001604.
  83. Ukritchon, B., Yoang, S. and Keawsawasvong, S. (2019), "Three-dimensional stability analysis of the collapse pressure on flexible pavements over rectangular trapdoors", Transport. Geotech., 21, 100277. https://doi.org/10.1016/j.trgeo.2019.100277.
  84. Villalobos, S.A. and Villalobos, F.A. (2021), "Effect of nail spacing on the global stability of soil nailed walls using limit equilibrium and finite element methods", Transport. Geotech., 26, 100454. https://doi.org/10.1016/j.trgeo.2020.100454.
  85. Wyllie, D.C. and Mah, C. (2004), Rock Slope Engineering, 4th Edition, Spon Press, London, United Kingdom.
  86. Wyllie, D.C. and Munn, F.J. (1979), "Use of movement monitoring to minimize production losses due to pit slope failure", Proceedings of the 1st International Symposium on Stability in Coal Mining, Miller Freeman Publications, Vancouver, Canada, 75-94.
  87. Yang, Y., Sun, G. and Zheng, H. (2019), "Stability analysis of soil-rock-mixture slopes using the numerical manifold method", Eng. Anal. Bound. Elements, 109, 153-160. https://doi.org/10.1016/j.enganabound.2019.09.020.
  88. Zanbak, C. (1983), "Design charts for rock slopes susceptible to toppling", J. Geotech. Eng., 109(8), 1039-1062. https://doi.org/10.1061/(ASCE)0733-9410(1983)109:8(1039)
  89. Zhang, G.C., Wang, F., Zhang, H., Tang, H.M., Li, X.H. and Zhong, Y. (2018), "New stability calculation method for rock slopes subject to flexural toppling failure", Int. J. Rock Mech. Min. Sci., 106, 319-328. https://doi.org/10.1016/j.ijrmms.2018.04.016.
  90. Zhou, C., Chen, Y., Jiang, Q. and Lu, W. (2011), "A generalized multi-field coupling approach and its application to stability and deformation control of a high slope", J. Rock Mech. Geotech. Eng., 3(3), 193-206. https://doi.org/10.3724/SP.J.1235.2011.00193.