Engineering Geology

Engineering Geology

Roof Tunnel Stability by Wedge Analysis

Authors
mehdi zamani
ali nikjoo
Department of Civil Engineering, Yasouj University
10.52547/jeg.14.5.163
Abstract
A jointed rock mass presents a more complex design problem than the other rock masses. The complexity arises from the number (greater than two) of joint sets which define the degree of discontinuity of medium. The condition that arises in these types of rock masses is the generation of discrete rock blocks, of various geometries. They defined by the natural fracture surfaces and the excavation surface. Stability problems in blocky jointed rock are generally associated with gravity falls of blocks from the roof and sidewalls. Whereas for block defined in the crown of tunnel,the requirement is to examine the potential for displacement of each block under the influence of the surface tractions arising from the local stress field and the gravitational load, in this paper various types of wedge formation in the crown of tunnel due to intersection of joint sets with various dip were examined. The state of stability of the wedge was then assessed through the factor of safety against roof failure. Following that the formed wedges in New York city and Washington D.C tunnels crown were investigated with limiting equilibrium analytical method and by use of Hoek and Brown failure criterion. The obtained results from analytical method corresponded with field observation.
Keywords
Limiting equilibrium
Stability analysis
Joint set
Rock mass
Wedge
 1. Bray J. W., "Unpublished note", Imperial College,London (1979). ## 2. John K. W.," Graphical stability analysis of slopes in jointed rock", J. Soil Mech. Found Div (ASCE). 94(2) (1968) 497-526. ## 3. Londe P., Vigier G., Vormeringer R.,"Stability of rock slopes, a three-dimensional study", J. Soil Mech. Found. Div. (ASCE) 95 (1) (1969) 235-62. ## 4. Hendron A. J, Cording E. J., Aiyer A. K.,"Analytical and graphical methods for the analysis of slopes in rock masses", Technical Report GL-80-2, US Army Engineers Nuclear Cratering Group, Livermore, CA, (1980) 1-55. ## 5. Hoek, E. T., Bray J. W., "Rock slope engineering", 3rd ed. London,England: Institute of Min and Metallurgy (1981) 275-342. ## 6. Warburton P. M., "Vector stability analysis of an arbitrary polyhedral rock block with any number of free faces", Int. J. Rock Mech. Min. Sci. Geomech. Abstr;18(5) (1981) 415–27. ## 7. Priest S. D., "Hemispherical projection methods in rock mechanics" ,London: George Allan & Unwin (1985) 75-84. ## 8. Goodman R. E, Shi GH., "Block theory and its application to rock engineering, London: Prentice-Hall (1985) 147-162. ## 9. Chan H. C., Einstein H. H., "Approach to complete limit equilibrium analysis for rock wedges-the method of artificial supports", Rock Mech;14(2) (1981) 59-86. ## 10. Mauldon M., Goodman R. E., "Vector analysis of keyblock rotation", J. Geotech Geoenviron Eng (ASCE);122(12) (1996) 976-87. ## 11. Tonon F., "Generalization of Mauldon’s and Goodman’s analysis of keyblock rotations", J Geotech Geoenviron Eng (ASCE) 124 (10) (1998) 913-22. ## 12. Sofianos A. I., "Stability of wedges in tunnel roofs", Int J Rock Mech Min Sci Geomech Abstr, 23 (2) (1986) 119-30. ## 13. Sofianos A. I., Nomikos P, Tsoutrelis C. E., "Stability of symmetric wedge formed in the roof of a circular tunnel: nonhydrostatic natural stress field. Int J Rock Mech Min Sci., 36 (1999) 687-91. ## 14. Nomikos P., Sofianos A. I., Tsoutrelis C. E., "Symmetric wedge in the roof of a tunnel excavated in an inclined stress field", Int J Rock Mech Min Sci., 39 (2002) 59-67. ## 15. Hudson J. A., Harrison J. P., "Engineering rock mechanics: an introduction to the principles", 4th ed.. Amsterdam: Elsevier (2005). ## 16. Rocscience, Unwedge Theory Manual-Factor of Safety Calculations /http://www .rocscience.com /downloads/unwedge/unwedge_theory.pdf. (2009). ## 17. Asadollahi P., "Stability analysis of a single three dimensional rock block: effect of dilatancy and high-velocity water jet impact", PhDdissertation, University of Texas: Austin (2009). ## 18. Tonon F., "Analysis of single rock blocks for general failure mode sunder conservative and non-conservative forces", IntJ Numer An al Methods Geomech;31(14) (2007) 1567-608. ## 19. Tonon F., Asadollahi P., "Validation of single rock block stability analysis (BS3D) for wedge failure", IntJ Rock MechMin. Sci., 45, (2008) 627-37. ## 20. Asadollahi P., Tonon F., "Definition of factor of safety for rock blocks", International Journal of Rock Mechanics & Mining Sciences 47 (2010) 1384-1390. ## 21. Wang Y. J., Yin J. H., "Wedge stability analysis considering dilatancy of disconti-nuities", Rock Mech., Rock Eng., 35 (2) (2002) 127-37. ## 22. Chen Z. Y., "A generalized solution for tetrahedral rock wedge stability analysis", Int J Rock Mech., Min Sci., 41, (2004) 613-28. ## 23. Yeung M. R., Jiang Q. H., Sun N., "Validation of block theory and threedimensional discontinuous deformation analysis as wedge stability analysis methods", Int J Rock Mech., Min Sci., 40, (2003) 265-75. ## 24. Low B. K., "Reliability analysis of rock wedges", J Geotech Geoenviron Eng., 123 (6) (1997) 498-505. ## 25. Park H., West T. R., "Development of a probabilistic approach for rock wedge failure", Eng Geol., 59 (2001) 233-51. ## 25. Park H. J., West T. R., Woo I., "Probabilistic analysis of rock slope stability and random properties of discontinuity parameters", parameters, Interstate High-way 40, Western North Carolina, USA. Eng., Geol., 79 (2005) 230–50. ## 26. Jimenez-Rodriguez R., Sitar N., "Rock wedge stability analysis using system reliability methods", Rock Mech., Rock Eng., 40 (4) (2007)419-27. ## 27. Low B. K., "Reliability analysis of rock slopes involving correlated non-normals. Int J Rock Mech Min Sci;44(6):922–35(2007). ## 28. Li DQ, Zhou CB, Lu WB, Jiang QH. A system reliability approach for evaluating stability of rock wedges with correlated failure modes. Comp Geotech;36(8):1298–307(2009). ## 29. Duncan CW, Christophere WM. Rock slope engineering: civil and mining. 4rd ed. New York: Spon Press; (2004). ## 30. Jiang Q, Liu X, Wei W, Zhou Ch . A new method for analyzing the stability of rock wedges. International Journal of Rock Mechanics & Mining Sciences 60 , 413–422(2013). ## 31. Mirzaeian, F., K.Shahriar .,M.Sharifzadeh,"Tunnel Probabilistic Structure Analysis Using the FORM",Journal of Geological Research,Hindawi Publishing Corporation, Article ID 3947,PP. 1-10(2015). ## 32. Curran, J.H., B.Corkum ., R.E.Hammah,"Three-dimensional Analysis of Underground Wedges under the Influence of Stresses",http:/www.rocscience.com/documents/pdfs/uploads/, 7776.pdf,PP.1-7(2015). ## 33. Budiman, R.C., R.Pratama ., D.Muslim and I.Sophian,"Design Analysis of Tunnel Portal in Pasi Jawa L250 Pongkor’s GMBU Underground Mine PT. Aneka Tabbang Tbk.,10th Asian Regional Conference of IAEG,PP.1-6(2015) ## 34. Brady, B.H.G, Brown, E.T., " Rock Mechanics for Underground mining", George Allen &Unwin (publishers) Ltd,PP. 352-364(1992). ## 35. Hoek, E., Brown, E.T, "Underground excavations in rock", The Institution of Mining and Metallurgy,PP. 115-127(1980). ## 36. Cording, Edward.J., Mahar, James W., Brierley, G. S., "Observation for shallow chambers in rock",Proceedings of the International Symposium,Zurich,April 4-6,PP. 485-508 (1977). ##