بررسی نقش دانه‌های ریز و درشت در مخلوط‌های خاکی با استفاده از روش اجزای مجزا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد، ایران

2 گروه مهندسی عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد

چکیده

در مهندسی ژئوتکنیک، قبلا تصور می شد که با افزایش سهم فاز ریزدانه غیرخمیری به فاز درشت دانه باعث افزایش مقاومت برشی خاک و کاهش نسبت تخلخل کلی خاک می‌گردد، درصورتی که طبق نتایج آزمایشگاهی چنین نیست. در این مقاله با استفاده از روش اجزای مجزا، چندین نمونه خاک با مخلوط کردن دو نوع خاک مختلف با فاز درشت دانه و ریزدانه تهیه شده و بصورت دوبعدی تحت بارگذاری دومحوری قرار گرفتند. دانه‌های مورد استفاده بصورت دایروی در نظر گرفته شدند. بارگذاری نمونه ها تا رسیدن به حالت حد بحرانی ادامه یافت. بر طبق نتایج بدست آمده، پارامترهای مربوط به مشارکت سهم بخش های درشت دانه و ریزدانه بدست آمدند. بدین منظور، از شاخص‌های تماسی جایگزینی به نام نسبت تخلخل معادل محتوای درشت دانه و معادل محتوای ریزدانه استفاده شدند. بررسی نتایج شبیه سازی ها نشان از انطباق خوب با نتایج آزمایشگاهی موجود در ادبیات فنی دارد. محتوای ریزدانه آستانه برای مجموعه نمونه ها، که بیانگر نقش غالب یکی از دو فاز درشت دانه و ریزدانه است، بدست آمد. شبیه سازی ها در فضای دوبعدی نشان داد که می توان برای خاک‌های با درصدهای وزنی مختلف فاز درشت و ریز، به حالت حد بحرانی منحصر به خود رسید. اگر از تعریف نسبت تخلخل های معادل فاز درشت و ریز استفاده شود، می‌توان به یک خط بحرانی واحد برای مجموعه ای از خاک ها با درصدهای وزنی مختلف فاز درشت و ریز رسید. همچنین، در این مقاله، روند تغییرات پارامترهای سهم مشارکت دو فاز درشت و ریز بر حسب درصد ریزدانه بدست آمد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

An Investigation of Fines and Coarse Contents in Granular Mixtures by Using Discrete Element Method

نویسندگان [English]

  • Sajjad Zoghi 1
  • Ehsan Seyedi Hosseininia 2
1 Civil Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Iran
2 Civil Eng. Department, Faculty of engineering, Ferdowsi University of Mashhad
چکیده [English]

It is believed that the addition of fine-grained soil to a base coarse-grained soil would result in shear strength increment due to filling up the voids among coarse-grained content and reducing global void ratio. However, this belief was against the following experiments. Instead of the definition of classical void ratio, two variables referred to as equivalent inter-granular and inter-fine void ratios, have been proposed to resolve this problem. Using these variables can help how a binary soil behaves. In this paper, by using the discrete element method, several binary soil samples were created by mixing two coarse and fine-grained soils. The two fine and coarse-grained soils have different gradations. The soil samples were prepared by considering zero, 10, 30, 40, 70, 100 percent fines content. Simulations were performed in two-dimension in which, the particles were circular. After each soil sample preparation, it was consolidated under isotropic confining pressure followed by biaxial compression loading. Each sample was tested under three different confining pressures. The biaxial loading condition was continued until the samples reached the critical state. This is the case where there is no variation in the deviatoric stress as well as the volume change along with the increase in the axial strain. Based on the simulated results, the required parameters to estimate the portion of the role of coarse and fine-grained parts in the global soil behavior were obtained. Comparison of the results of this study with those of experiments showed good agreements. The threshold fines content after which, the mechanical behavior of the binary soils is governed by fine grains, was assessed. It was shown that for the two-dimensional samples, the critical state can be obtained and the critical state line (CSL) can be constituted in the q-p’-e space. It was also seen that for the two groups of samples where either of coarse or fine-grained content are dominant, a unique critical state line can be obtained if the inter-granular and inter-fine void ratios are used instead of the global void ratio. The influence factors were back-calculated and the values were justified in comparison with the experiments.

کلیدواژه‌ها [English]

  • Discrete element method (DEM)
  • Fines content
  • Coarse content
  • Influence factors
  • Critical State

مراجع

[1]  S. Thevanayagam, T. Shenthan, S. Mohan, J. Liang, Undrained fragility of clean sands, silty sands, and sandy silts, Journal of Geotechnical and Geoenvironmental Engineering, 128(10) (2002) 849-859.
[2]  H.B. Seed, I.M. Idriss, I. Arango, Evaluation of liquefaction potential using field performance data, Journal of Geotechnical Engineering, 109(3) (1983) 458-482.
[3]  M. Yoshimine, K. Ishihara, W. Vargas, Effects of principal stress direction and intermediate principal stress on drained shear behavior of sand, Soils and Foundations, 38(3) (1998) 197-188.
[4]  P.K. Robertson, C.E. Wride, Evaluating cyclic liquefaction potential using the cone penetration test, Canadian Geotechnical Journal, 35(3) (1998) 442-459.
[5]  R.B. Seed, L.F.J. Harder, SPT-based analysis of cyclic pore pressure generation and undrained residual strength, in:Seed Symposium berkeley, 1990, pp. 351-376.
[6]  R.D. Andrus, K.H. Stokoe, Liquefaction resistance of soils from shearwave velocity, GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING, 126(11) (2000) 1015-1025.
[7]  J.A. Yamamuro, P.V. Lade, Experiments and modeling of silty sands susceptible to static liquefaction, Mechanics of Cohesive-frictional Materials, 4(6) (1999) 545-564.
[8]  M.D. Evans, S. Zhou, Liquefaction behavior of sand-gravel composites, journal of Geotechnical Engineering, 121(3) (1995) 278-298.
[9]  W.-J. Chang, T. Phantachang, Effects of gravel content on shear resistance of gravelly soils, Engineering Geology, 207 (2016) 78-90.
[10]  S. Altun, A.B. Goktepe, C. Akgunar, Cyclic Shear Strength of Silts and Sands under Cyclic Loading, Earthquake Engineering and Soil Dynamics, 158(33) (2005) 1-11.
[11] V.C. Xenaki, G.A. Athanasopoulos, Liquefaction resistance of sand–silt mixtures: an experimental investigation of the effect of fines, soil Dynamics and Earthquake Engineering, 23(3) (2003) 1-12.
[12] S. Thevanayagam, Effect of Fines and Confining Stress on Undrained Shear Strength of Silty Sands, Geotechnical and Geoenvironmental Engineering, 124(6) (1998) 479-491.
[13] A.I. Papadopouloua, T.M. Tika, The effect of fines plasticity on monotonic undrained shear strength and liquefaction resistance of sands, Soil Dynamics and Earthquake Engineering, 88 (2016) 191-206.
[14]  M. Meidani, C.S. Chang, Y. Deng, On active and inactive voids and a compression model for granular soils, Engineering Geology, 222 (2017) 156-167.
[15]  C.S. Chang, M. Meidani, Y. Deng, A Compression model for sand–silt mixtures based on the concept of active and inactive voids, Acta Geotechnica, 12(6) (2017) 1301-1317.
[16]  J.K. Mitchell, K. Soga, Fundamentals of soil behavior, wiley, New York, 1976.
[17]  T.C. Kenny, Residual strengths of mineral mixtures, in: 9th international conference on soil mechanics, Tokyo, 1977, pp. 155-160.
[18]  R. Kuerbis, D. Nagussey, Y.P. Vaid, Effect of gradation and fines content on the undrained response of sand, in:  Hydraulc Fill Structure, Geothechnical Special Publication, New York, 1989, pp. 330-345.
[19]  V.N. Georgiannou, D.W. Hight, J.B. Burland, The undrained behaviour of clayey sands in triaxial compression and extension, Géotechnique, 40(3) (1990) 431-449.
[20]  V.N. Georgiannou, D.W. Hight, J.B. Burland, Undrained behaviour of natural and model clayey sands, Soils and Foundations, 31(3) (1991) 17-29.
[21]  V.N. Georgiannou, D.W. Hight, J.B. Burland, Behaviour of clayey sands under undrained cyclic triaxial loading, Géotechnique, 41(3) (1991) 383-393.
[22]  T.D. Pitman, P.K. Robertson, D.C. Sego, Influence of fines on the collapse of loose sands, Canadian Geotechnical Journal, 31(5) (1994) 728-739.
[23]  Y.P. Vaid, Liquefaction of silty soils, in:  Ground failures under seismic conditions, Geotechnical Special Publisher, New York, 1994, pp. 1-16.
[24] S. Thevanayagam, Effect of Fines and Confining Stress on Undrained Shear Strength of Silty Sands - Clousure, Journal of Geotechnical and Geoenvironmental Engineering, 125(11) (1999) 1024-1027.
[25] S. Thevanayagam, G.R. Martin, Liquefaction in silty soils—screening and remediation issues, Soil Dynamics and Earthquake Engineering, 22 (2002) 1035-1042.
[26] S. Thevanayagam, Intergrain contact density indices for granular mixs—I, Earthquake Engineering and Engineering Vibration, 6(2) (2007) 123-134.
[27] R.d.F. Lopez, J. Ekblad, J. Silfwerbrand, Resilient properties of binary granular mixtures: A numerical investigation, Computers and Geotechnics, 76 (2016) 222233.
[28] J. Gong, J. Liu, Mechanical transitional behavior of binary mixtures via DEM: Effect of differences in contacttype friction coefficients, Computers and Geotechnics, 85 (2017) 1-14.
[29]  C.S. Chang, Y. Deng, A particle packing model for sand–silt mixtures with the effect of dual-skeleton, Granular Matter, 2017(19:80) (2017).
[30]  A. Lashkari, M. Karimi, DEM Study of Critical State in Binary Granular Soils and a Unified Constitutive Model for Clean and Silty Sands, Bulletin of Earthquake Science and Engineering, 2(4) (2016) 27-45.
[31] D.W. Hight, V.N. Georgiannou, Effects of sampling on the undrained behavior of clayey sands Géotechnique, 45(2) (1995) 237-247.
[32] M.H. Baziar, R. Dobry, Residual strength and large deformation potential of loose silty sands, journal of Geotechnical Engineering, 121(12) (1995) 896-906.
[33] E. Ovando-Shelley, B.E. Pérez, Undrained behavior of clayey sand in load controlled triaxial tests, Géotechnique, 47(1) (1997) 97-111.
[34]  J. Chu, W.K. Leong, Effect of fines on instability behaviour of loose sand, Géotechnique, 52(10) (2002) 751-755.
[35]  S.L. Yang, S. Lacasse, R. Sandven, Determination of the transitional fines contents of mixtures of sand and nonplastic fines, Geotechnical Testing Journal, 29(2) (2006) .701-201
[36]  M.M. Rahman, S.R. Lo, The prediction of equivalent granular steady state line of loose sand with fines, Geomechanics and Geoengineering, 3(3) (2008) 179-191.
[37]  P.A. Cundall, O.D. Strack, discrete numerical model for granular assemblies, Géotechnique, 29(1) (1979) 47–65.
[38]  A.A. Mirghasemi, L. Rothenburg, E.L. Matyas, Numerical simulations of assemblies of two-dimensional polygonshaped particles and effects of confining pressure on shear strength, Soils and Foundations, 37(3) (1997) 43-52.
[39]  E. Seyedi Hosseininia, A micromechanical study on the stress rotation in granular materials due to fabric evolution, Powder Technology, 283(6) (2015) 462-474.
[40]  P. C.P., The Effects Of Non-Plastic and Plastic Fines On The Liquefaction Of Sandy Soils, PhD Thesis, Virginia Tech University, 1999.
[41]  Y.-T. Huang, A.-B. Huang, Y.-C. Kuo, M.-D. Tsai, A laboratory study on the undrained strength of a silty sand from Central Western Taiwan, Soil Dynamics and Earthquake Engineering, 24 (2004) 733-743.
[42]  C.P. Polito, J. Martin II, R., Effects of nonplastic fines on the liquefaction resistance of sands, Journal of Geotechnical and Geoenvironmental Engineering, 127(5) (2001) 408-415.
[43]  K.S. Prakasha, V.S. Chandrasekaran, Behavior of marine sand-clay mixtures under static and cyclic triaxial shear, Journal of Geotechnical and Geoenvironmental Engineering, 131(2) (2005) 213-222.
[44] M.M. Rahman, S.R. Lo, M.A.L. Baki, Equivalent granular state parameter and undrained behaviour of sand–fines mixtures, Acta Geotechnica, 6 (2011) 183-194.
[45] S. Zlatović, K. Ishihara, On the influence of nonplastic fines on residual strength, in:  Frst International Conference On Earthquake Geotechnical Engineering, 1995, pp. 239-244.
[46] M.C. Powers, A new roundness scale for sedimentary particles, Sediment Petrol, 23(2) (1953) 117-119.
[47]  F. Vahidi-Nia, A. Lashkari, S.M. Binesh, An insight into the mechanical behavior of binary granular soils, Particuology, 21 (2015) 82-29.
[48]  A. Lashkari, Recommendations for extension and recalibration of an existing sand constitutive model taking into account varying non-plastic fines content, Soil Dynamics and Earthquake Engineering, 61-62 (2014) 212-238.
 
نشریه مهندسی عمران امیرکبیر
دوره 52، شماره 1
فروردین 1399
صفحه 37-52

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