تکنیک‌های ارزیابی ظرفیت باربری پی سطحی زبر با روش خطوط مشخصه‌ی تنش

نوع مقاله : مقاله ترویجی

نویسندگان

1 گروه مهندسی عمران، واحد تهران جنوب، دانشگاه آزاد اسلامی، تهران، ایران

2 پژوهشکده مهندسی ژئوتکنیک، پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله، تهران، ایران

چکیده

برآورد ظرفیت باربری پی­های سطحی همواره مورد نیاز مهندسین بوده است. روش مشخصه­های تنش برای حل مسائل ظرفیت باربری پی­های مستقر بر فضای نیم‌بی­نهایت به دلیل سادگی، سرعت در انجام محاسبات و عدم نیاز به مش­بندی و مدل­های رفتاری پیچیده­ی خاک، تکنیکی کارآمد و مؤثر است. در نوشتار حاضر، ابتدا فرمول­بندی ریاضی روش خطوط مشخصه­ی تنش به‌اختصار تشریح شده است. نحوه­ی به‌کارگیری آن در ارزیابی ظرفیت باربری پی­های زبر و تکنیک­های مختلف حل مسئله‌ی زبری بررسی شده است. سپس، چگونگی در نظر گرفتن یکنواختی یا غیریکنواختی شیب فشار تماس وارد بر کف پی و تأثیر آن بر ضرایب ظرفیت باربری پی­ها مورد بحث و بررسی قرار گرفته است. اثرات ناشی از نحوه­ی ملحوظ نمودن زبری به روش­های مختلف بر این ضرایب سه­گانه با یکدیگر مقایسه شده است. در نهایت، به چالش‌های جدید و مهم پیش رو در استفاده از روش مشخصه‌‌های تنش در بررسی اثرات زبری بر ظرفیت باربری پی پرداخته شده است.

کلیدواژه‌ها


1.    Terzaghi, K. (1943) Theoretical Soil Mechanics. Wiley, New York.
2.    Taylor, D. (1948) Fundamentals of Soil Mechanics. Chapman and Hall, Limited, New York.
3.    Meyerhof, G.G. (1951) The ultimate bearing capacity of foudations. Geotechnique, 2(4), 301-332.
4.    Richards Jr, R., Elms, D.G., and Budhu, M. (1993) Seismic bearing capacity and settlements of foundations. Journal of Geotechnical Engineering, 119(4), 662-674.
5.    Farzaneh, O., Askari, F., and Ganjian, N. (2008) Three-dimensional stability analysis of convex slopes in plan view. Journal of Geotechnical and Geoenvironmental Engineering, 134(8), 1192-1200.
6.    Farzaneh, O., Askari, F. and Yeganeh Khaksar, R. (2010) Bearing Capacity of Foundations Located on Concave Slopes in Plan View Using Upper Bound Theorem. Journal of Civil and Surveying Engineering, 44(2), 215-224 (in Persian).
7.    Hjiaj, M., Lyamin, A.V., and Sloan, S.W. (2005) Numerical Limit Analysis Solutions for the Bearing Capacity Factor Nγ. International Journal of Solids and Structures, 42(5-6), 1681-1704.
8.    Lyamin, A.V. and Sloan, S.W. (2002) lower bound limit analysis using non‐linear programming. International Journal for Numerical Methods in Engineering, 55(5), 573-611.
9.    Lyamin, A.V. and Sloan, S.W. (2002) Upper bound limit analysis using linear finite elements and non‐linear programming. International Journal for Numerical and Analytical Methods in Geomecha-nics, 26(2), 181-216.
10.    Askari, F. and Farzaneh, O. (2003) Upper-bound solution for seismic bearing capacity of shallow foundations near slopes. Geotechnique, 53(8), 697-702.
11.    Kumar, J. and Khatri, V.N. (2008) Effect of footing roughness on lower bound Nγ values. International Journal of Geomechanics, 8(3), 176-187.
12.    Kumar, J. and Khatri, V.N. (2011) Bearing capacity factors of circular foundations for a general c–φ soil using lower bound finite elements limit Analysis. International Journal for Numerical and Analytical Methods in Geomechanics, 35(3), 393-405.
13.    Kumar, J. and Kouzer, K.M. (2007) Effect of footing roughness on bearing capacity factor N.  Journal of Geotechnical and Geoenvironmental Engineering, 133(5), 502-511.
14.    Lyamin, A.V., Salgado, R., Sloan, S.W., and Prezzi, M. (2007) Two-and three-dimensional bearing capacity of footings in sand. Géotechnique, 57(8), 647-662.
15.    Griffiths, D.V. (1982) Computation of bearing capacity factors using finite elements.  Geotechnique, 32(3), 195-202.
16.    Frydman, S. and Burd, H.J. (1997) Numerical studies of bearing-capacity factor Nγ. Journal of Geotechnical and Geoenvironmental Engineering, 123(1), 20-29.
17.    Loukidis, D. and Salgado, R. (2009) Bearing capacity of strip and circular footings in sand using finite elements. Computers and Geotechnics, 36(5), 871-879.
18.    Manoharan, N. and Dasgupta, S.P. (1995) Bearing capacity of surface footings by finite elements. Computers and Structures, 54(4), 563-586.
19.    Erickson, H.L. and Drescher, A. (2002) Bearing capacity of circular footings. Journal of Geotechnical and Geoenvironmental Engineering, 128(1), 38-43.
20.    Sokolovski, V.V. (1960) Statics of soil media (translated from Russian by DH Jones and AN schofield). Butterworth, London, England, 21, 369-395.
21.    Martin, C.M. (2005) Exact Bearing Capacity Calculations Using the Method of Characteristics. In: Proceedings of the IACMAG, Turin, 441-450.
22.    Kumar, J. and Mohan Rao, V.B.K. (2002) Seismic bearing capacity factors for spread foundatins. Geotechnique, 52(2), 79-88.
23.    Kumar, J. and Mohan Rao, V.B.K. (2003) Seismic bearing capacity of foundations on slops. Geotechnique, 53(3), 347-361.
24.    Kumar, J. (2009) The variation of Nγ with footing roughness using the method of characteristics. International Journal for Numerical and Analytical Methods in Geomechanics, 33(2), 275-284.
25.    Kumar, J. (2003) Nγ for rough strip footing using the method of characteristics. Canadian Geotech-nical Journal, 40(3), 669-674.
26.    Smith, C.C. (2005) Complete limiting stress solutions for the bearing capacity of strip footings on a Mohr-Coulomb soil. Géotechnique, 55(8), 607-612.
27.    Kumar, J. and Ghosh, P. (2005) Bearing capacity factor Nγ for ring footings using the method of characteristics. Canadian Geotechnical Journal, 42(5), 1474-1484.
28.    Martin, C.M. (2003) New software for rigorous bearing capacity calculations. Proc. British Geotech. Assoc. Int. Conf. on Found., Dundee, 581-592.
29.    Sun, J.P., Zhao, Z.Y., and Cheng, Y.P. (2013) Bearing capacity analysis using the method of charac-teristics. Acta Mechanica Sinica, 29(2), 179-188.
30.    Bolton, M.D. and Lau, C.K. (1993) Vertical bearing capacity factors for circular and strip footings on Mohr-Coulomb Soil. Canadian Geotechnical Journal, 30(6), 1024-1033.
31.    Martin, C.M. (2004) ABC-analysis of bearing capacity v1.0. Software and documentation. http://www.eng.ox.ac.uk/civil/people/cmm/software/abc. Accessed 14 Dec 2014.
32.    Casablanca, O., Cascone, E., and Biondi, G. (2016). The static and seismic bearing capacity factor Nγ for footings adjacent to slopes. Procedia Engineering, 158, 410-415.
33.    Cascone, E. and Casablanca, O. (2016). Static and seismic bearing capacity of shallow strip footings. Soil Dynamics and Earthquake Engineering, 84, 204-223.
34.    Kamalian, M., Behnia, C., Lotfizadeh, M., and Rastegar, A. (2011) Considerations about load inclination effect on seismic bearing capacity factors of strip foundations. Journal of Civil and Surveying Engineering, 45(4), 495-504 (in Persian).
35.    Kamalian, M., Goldasteh, M., Amoli, R., and Rahmani, I. (2013) Estimation of seismic bearing capacity coefficients of strip foundations adjacent to the top of slops by the stress characteristic method. Sharif Journal of Civil Engineering,        29-2(3), 81-90 (in Persian).
36.    Kamalian, M. (2014) Estimation of Seismic Bearing Capacity of Strip Foundations on Slopes by the Stress Characteristic Method. Research Report, International Institute of Earthquake Engineering and Seismology (IIEES) 6309-p.93-1 (in Persian).
37.    Kamalian, M. (2007) Estimation of Friction Effect on Seismic Bearing Capacity of Strip Foundations by the Characteristic Method. Research Report, International Institute of Earthquake Engineering and Seismology (IIEES) 6118-p.89-4 (in Persian).
38.    Jahanandish, M. and Keshavarz, A. (2005) Seismic bearing capacity of foundations on reinforced soil slopes. Geotextiles and Geomembranes, 23(1), 1-25.
39.    Keshavarz, A., Jahanandish, M., and Ghahramani, A. (2011) Seismic bearing capacity analysis of reinforced soils by the method of stress characteristics. IJST, Transactions of Civil Engineering, 35, 185-197.
40.    Ames, W.F. (1992) Numerical Methods for Partial Differential Equations. Boston: Academic Press.
41.    Booker, J.R. and Davis, E.H. (1977) 'Stability analysis by plasticity theory'. In: Desai CS, Christian JT (Eds), Numerical Methods in Geotechnical Engineering. McGraw Hill, New York, 719-748.
42.    Larkin, L.A. (1968) Theoretical bearing capacity of very shallow footings. Journal of the Soil Mecha-nics and Foundations Division, 94(6), 1347-1360.
43.    James, R.G. and Bransby, P. (1970) Experimental and theoretical investigations of a passive earth pressure problem. Geotechnique, 20(1), 17-37.
44.    Graham, J. (1971) Calculation of passive pressure in sand. Canadian Geotechnical Journal, 8(4), 566-578.
45.    Lee, I.K. and Herington, J.R. (1972) A theoretical study of the pressures acting on a rigid wall by a sloping earth or rockfill. Geotechnique, 22(1), 1-26.
46.    Behnia, C. and Tabatabai, A.M. (1988) 'Plastic Equilibrium'. In: Soil Mechanics, 1, (Ed.) Tehran University Pub. Co., Tehran, 357-408 (in Persian).
47.    Behnia, C. and Tabatabai, A.M. (1989) 'Surface Footings'. In: Soil Mechanics, 2, (Ed.) Tehran University Pub. Co., Tehran, 185-257 (in Persian).
48.    Lundgren, H. and Mortensen, K. (1953) Determination by the theory of plasticity of the bearing capacity of continuous footings on sand. In: Proceedings of the Third International Conference on Soil Mechanics and Foundation Engineering, Zürich, Switzerland, 409-412.
49.    Michalowski, R. (1997) An estimate of the influence of soil weight on bearing capacity using limit analysis. Soils and Foundations, 37(4), 57-64.
50.    Hill, R. (1950) The Mathematical Theory of Plasticity. Clarendon Press: Oxford University, London.
51.    Ahmadi, S., Kamalian, M., and Askari, F. (2020) Evaluation of the static bearing capacity coefficients of rough strip footing using the stress characteristics method. Int. J. Civ. Eng., 19, 155-165.
52.    Ahmadi, S., Kamalian, M. and Askari, F., (2020) Considerations on bearing capacity factors of rough strip footing using the stress characteristics method. Iran J. Sci. Technol. Trans. Civ. Eng., 1-11.