الگوی کشسان - خمیری یکپارچه توأمان خاک، بر اساس نظریه سطح پیرامونی در حالت اشباع و نیمه‌اشباع

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده فنی و مهندسی، دانشگاه تربیت مدرس، تهران، ایران

2 دانشکده مهندسی عمران و محیط زیست، دانشگاه علوم و فناوری نروژ، تروندهایم، نروژ

چکیده

خاک‌ها در طبیعت به طور متغیر می‌توانند در شرایط خشک، اشباع و نیمه‌اشباع باشند. در پروژه‌های ژئوتکنیکی، به دلیل تغییر حالت خاک تحت اثرات محیطی باید هر سه حالت خاک در نظر گرفته شود. اکثر الگوهای کشسان خمیری در مکانیک خاک برای شرایط اشباع توسعه داده شده‌اند. در این مقاله، الگوی یکپارچه در چهارچوب حالت بحرانی برای توصیف رفتار طیف وسیعی از خاک‌ها تحت بارگذاری یکنواخت در شرایط زهکشی‌ شده و زهکشی‌ نشده بر اساس نظریه سطح پیرامونی و قانون جریان ناهمراه ارائه شده است. به منظور شبیه‌سازی یکپارچه هر دو خاک رس و ماسه، از جمله رفتار انتقال حالت، در این الگو از قانون اتساع عمومی اصلاح شده استفاده شده است. در الگوی حاضر از دیدگاه تنش مؤثر استفاده شده که به راحتی هر دو حالت اشباع و نیمه‌اشباع خاک را از طریق فراسنج تنش مؤثر وابسته به مقدار مکش در نظر می‌گیرد. الگوی پیشنهادی اثر توأمان رفتارهای مکانیکی و نگهداشت آب را از طریق منحنی مشخصه خاک آب وابسته به نسبت پوکی در نظر گرفته است. به منظور بهبود دقت و همگرایی الگو، روش انتگرال‌گیری عددی ضمنی جهت پیاده‌سازی الگو به کار گرفته شده است. با استفاده از داده‌های آزمایشگاهی موجود در ادبیات موضوع، نشان داده شده که پیش‌بینی‌های عددی الگو تطابق خوبی با نتایج آزمایشگاهی داشته است. نتایج نشان داد که الگوی پیشنهادی قادر به پیش‌بینی ویژگی‌های شاخص رفتاری طیف وسیعی از خاک‌ها، شامل رفتار انتقال هموار از حالت کشسان به خمیری، نرم ‌شوندگی و سخت ‌شوندگی تنش، اتساع کرنش و همچنین رفتار انتقال حالت است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

A Coupled Unified Elastoplastic Model of Soil, Based on Bounding Surface Theory in Saturated and Unsaturated States

نویسندگان [English]

  • Ramin Ostovari 1
  • Ehsan Taheri 1
  • Ali Ghoreishian Amiri 2
1 Rock Mechanics, Faculty of Engineering, Tarbiat Modarres university, Tehran, Iran
2 Civil and Environmental Engineering, Norwegian University of Science and Technology, Trondheim, Norway
چکیده [English]

Soils in nature can variably be in dry, saturated, or unsaturated conditions. In geotechnical projects, all three soil states must be considered, because soil states can be changed by environmental effects. The most elastoplastic models in soil mechanics were developed for saturated conditions. In this paper, a unified model, in a critical state framework is presented for describing the behavior of a large spectrum of soils under monotonic loading in drained and undrained conditions based on bounding surface theory and the nonassociated flow rule. To unify the simulation of both clayey and sandy soils, among phase transformation behavior, in this model, a modified general dilatancy rule is used. In the current model, an effective stress approach is used that can easily consider both saturated and unsaturated states through effective stress parameter dependent on suction value. The proposed model considered the coupling effect of mechanical and water retention behaviors using soil water characteristic curve dependent on void ratio. To improve model accuracy and convergence, an implicit numerical integration scheme is used to implement the model. Using the experimental data available in the literature, numerical model predictions were shown to be in good agreement with the experimental results. The results showed that the proposed model was able to predict the characteristic features of the behavior of a wide range of soils, including smooth transition behavior from elastic to a plastic state, stress softening and hardening, strain dilatancy, and also phase transformation behavior.  

کلیدواژه‌ها [English]

  • Unified Model
  • Saturated and Unsaturated Soils
  • Bounding Surface
  • Effective Stress
  • Hydromechanical Coupling Effect
[1] C. Zhang, N. Lu, Unified Effective Stress Equation for Soil, Journal of Engineering Mechanics, 146(2) (2020) 04019135.
[2] S.K. Thota, T.D. Cao, F. Vahedifard, E. Ghazanfari, An Effective Stress Model for Unsaturated Soils at Elevated Temperatures, in:  Geo-Congress 2020, 2020, pp. 358-366.
[3] P. Lin, L. Tang, P. Ni, Generalized Plastic Mechanics-Based Constitutive Model for Estimation of Dynamic Stresses in Unsaturated Subgrade Soils, International Journal of Geomechanics, 20(7) (2020) 04020084.
[4] G.M. Rotisciani, A. Desideri, A. Amorosi, Unsaturated structured soils: constitutive modelling and stability analyses, Acta Geotechnica, 16(11) (2021) 3355-3380.
[5] H. Ghasemzadeh, S.A. Ghoreishian Amiri, A hydro-mechanical elastoplastic model for unsaturated soils under isotropic loading conditions, Computers and Geotechnics, 51 (2013) 91-100.
[6] G. Cai, B. Han, M. Li, K. Di, Y. Liu, J. Li, T. Wu, Numerical Implementation of a Hydro-Mechanical Coupling Constitutive Model for Unsaturated Soil Considering the Effect of Micro-Pore Structure, Applied Sciences, 11(12) (2021) 5368.
[7] J. Fang, Y. Feng, Elastoplastic Model and Three-Dimensional Method for Unsaturated Soils, Shock and Vibration, 2020 (2020) 8592628.
[8] E. Gholizadeh, M. Latifi, A coupled hydro-mechanical constitutive model for unsaturated frictional and cohesive soil, Computers and Geotechnics, 98 (2018) 69-81.
[9] E.E. Alonso, A. Gens, A. Josa, A constitutive model for partially saturated soils, Géotechnique, 40(3) (1990) 405-430.
[10] J. Kodikara, New framework for volumetric constitutive behaviour of compacted unsaturated soils, Canadian Geotechnical Journal, 49(11) (2012) 1227-1243.
[11] W. Fuentes, T. Triantafyllidis, Hydro-mechanical hypoplastic models for unsaturated soils under isotropic stress conditions, Computers and Geotechnics, 51 (2013) 72-82.
[12] A. Zhou, D. Sheng, An advanced hydro-mechanical constitutive model for unsaturated soils with different initial densities, Computers and Geotechnics, 63 (2015) 46-66.
[13] J. Li, Z.-Y. Yin, Y.-J. Cui, K. Liu, J.-H. Yin, An elasto-plastic model of unsaturated soil with an explicit degree of saturation-dependent CSL, Engineering Geology, 260 (2019) 105240.
[14] D. Gallipoli, A. Gens, R. Sharma, J. Vaunat, An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour, Géotechnique, 53(1) (2003) 123-135.
[15] E.E. ALONSO, N.M. PINYOL, A. GENS, Compacted soil behaviour: initial state, structure and constitutive modelling, Géotechnique, 63(6) (2013) 463-478.
[16] M. Kadivar, K.N. Manahiloh, V.N. Kaliakin, A Bounding Surface Based Constitutive Model for Unsaturated Granular Soils, in:  Geo-Congress 2019, 2019, pp. 833-843.
[17] S.J. Wheeler, Inclusion of specific water volume within an elasto-plastic model for unsaturated soil, Canadian Geotechnical Journal, 33(1) (1996) 42-57.
[18] P. Dangla, L. Malinsky, O. Coussy, Plasticity and imbibition-drainage curves for unsaturated soils: a unified approach, in:  Numerical models in geomechanics: NUMOG VI, 1997, pp. 141-146.
[19] J. Vaunat, E. Romero, C. Jommi, An elastoplastic hydro-mechanical model for unsaturated soils, in:  Experimental evidence and theoretical approaches in unsaturated soils, CRC Press, 2000, pp. 129-146.
[20] S.J. Wheeler, R.S. Sharma, M.S.R. Buisson, Coupling of hydraulic hysteresis and stress–strain behaviour in unsaturated soils, Géotechnique, 53(1) (2003) 41-54.
[21] K. Terzaghi, T.S. Mechanics, J. Wiley, Sons, New York,  (1943).
[22] A.W. Bishop, The Principle of Effective Stress, Teknisk Ukeblad, 39 (1959) 859-863.
[23] N. Khalili, M.H. Khabbaz, A unique relationship for χ for the determination of the shear strength of unsaturated soils, Géotechnique, 48(5) (1998) 681-687.
[24] N. KHALILI, S. ZARGARBASHI, Influence of hydraulic hysteresis on effective stress in unsaturated soils, Géotechnique, 60(9) (2010) 729-734.
[25] S.J. Wheeler, V. Sivakumar, An elasto-plastic critical state framework for unsaturated soil, Géotechnique, 45(1) (1995) 35-53.
[26] B. Loret, N. Khalili, A three-phase model for unsaturated soils, International Journal for Numerical and Analytical Methods in Geomechanics, 24 (2000) 893-927.
[27] Y.F. Dafalias, E.P. Popov, A model of nonlinearly hardening materials for complex loading, Acta Mechanica, 21(3) (1975) 173-192.
[28] R.D. Krieg, A Practical Two Surface Plasticity Theory, Journal of Applied Mechanics, 42(3) (1975) 641-646.
[29] H.S. Yu, CASM: a unified state parameter model for clay and sand, International Journal for Numerical and Analytical Methods in Geomechanics, 22(8) (1998) 621-653.
[30] A.R. Russell, N. Khalili, A unified bounding surface plasticity model for unsaturated soils, International Journal for Numerical and Analytical Methods in Geomechanics, 30(3) (2006) 181-212.
[31] B. Loret, N. Khalili, An effective stress elastic–plastic model for unsaturated porous media, Mechanics of Materials, 34(2) (2002) 97-116.
[32] K. Hashiguchi, General Description of Elastoplastic Deformation/Sliding Phenomena of Solids in High Accuracy and Numerical Efficiency: Subloading Surface Concept, Archives of Computational Methods in Engineering, 20(4) (2013) 361-417.
[33] X.S. Li, Y.F. Dafalias, Dilatancy for cohesionless soils, Géotechnique, 50(4) (2000) 449-460.
[34] Y.J. Cui, P. Delage, Yielding and plastic behaviour of an unsaturated compacted silt, Géotechnique, 46(2) (1996) 291-311.
[35] K.K. Muraleetharan, C. Liu, C. Wei, T.C.G. Kibbey, L. Chen, An elastoplatic framework for coupling hydraulic and mechanical behavior of unsaturated soils, International Journal of Plasticity, 25(3) (2009) 473-490.
[36] D.M. Pedroso, D.J. Williams, A novel approach for modelling soil–water characteristic curves with hysteresis, Computers and Geotechnics, 37(3) (2010) 374-380.
[37] W.-H. Zhou, K.-V. Yuen, F. Tan, Estimation of soil–water characteristic curve and relative permeability for granular soils with different initial dry densities, Engineering Geology, 179 (2014) 1-9.
[38] F. Tan, W.-H. Zhou, K.-V. Yuen, Modeling the soil water retention properties of same-textured soils with different initial void ratios, Journal of Hydrology, 542 (2016) 731-743.
[39] A. TARANTINO, A water retention model for deformable soils, Géotechnique, 59(9) (2009) 751-762.
[40] A.Y. Pasha, A. Khoshghalb, N. Khalili, Hysteretic Model for the Evolution of Water Retention Curve with Void Ratio, Journal of Engineering Mechanics, 143(7) (2017) 04017030.
[41] R. Brooks, T. Corey, HYDRAU uc properties of porous media, Hydrology Papers, Colorado State University, 24 (1964) 37.
[42] N. Khalili, M.A. Habte, S. Zargarbashi, A fully coupled flow deformation model for cyclic analysis of unsaturated soils including hydraulic and mechanical hystereses, Computers and Geotechnics, 35(6) (2008) 872-889.
[43] D.J. Henkel, The Effect of Overconsolidation on the Behaviour of Clays During Shear, Géotechnique, 6(4) (1956) 139-150.
[44] Y. Zhang, S. Zuo, R.Y.M. Li, Y. Mo, G. Yang, M. Zhang, Experimental study on the mechanical properties of Guiyang red clay considering the meso micro damage mechanism and stress path, Scientific Reports, 10(1) (2020) 17449.
[45] Y.-F. Jin, Z.-Y. Yin, S.-L. Shen, P.-Y. Hicher, Investigation into MOGA for identifying parameters of a critical-state-based sand model and parameters correlation by factor analysis, Acta Geotechnica, 11(5) (2016) 1131-1145.
[46] S. Sasitharan, P.K. Robertson, D.C. Sego, N.R. Morgenstern, State-boundary surface for very loose sand and its practical implications, Canadian Geotechnical Journal, 31(3) (1994) 321-334.
[47] D.a. Sun, D. Sheng, S.W. Sloan, Elastoplastic modelling of hydraulic and stress–strain behaviour of unsaturated soils, Mechanics of Materials, 39(3) (2007) 212-221.
[48] D.A. Sun, D. Sheng, L. Xiang, S.W. Sloan, Elastoplastic prediction of hydro-mechanical behaviour of unsaturated soils under undrained conditions, Computers and Geotechnics, 35(6) (2008) 845-852.