Elastic visco-plastic model for soft clay based on isochronous curves
LUO Qing-zi1, CHEN Xiao-ping2, YUAN Bing-xiang1, FENG De-luan1
1. School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, China; 2. College of Science and Engineering, Jinan University, Guangzhou 510632, China
Abstract:The deformation of soft clay is closely related to the time, including both consolidation effect and creep effect, between which the interaction determines the settlement and long-term settlement of soft soils. Based on the Bjerrum's theory of isochronous curves, an elastic visco-plastic constitutive model for soft clay is derived, which is used to replace the linear elastic stress-strain relationship of Terzaghi's consolidation theory. And with further consideration of nonlinear seepage influence, one-dimensional nonlinear governing equations which can couple the effect of creep and consolidation are established. There are 8 model parameters with concise physical meanings in this model, which can be obtained through laboratory tests easily. In addition, the Crank-Nicolson finite difference method can be used to solve the governing equations under certain boundary conditions. In order to verify the validity of the model, the calculated results by this model are contrasted with the results of oedometer tests and Leroueil and Kabbj' s CRS tests. It is shown that the calculated values are in good agreement with the experimental results.
罗庆姿, 陈晓平, 袁炳祥, 冯德銮. 基于等时曲线的软黏土弹黏塑性模型[J]. 岩土工程学报, 2018, 40(S2): 142-146.
LUO Qing-zi, CHEN Xiao-ping, YUAN Bing-xiang, FENG De-luan. Elastic visco-plastic model for soft clay based on isochronous curves. Chinese J. Geot. Eng., 2018, 40(S2): 142-146.
[1] LADD C C, FOOTT R, ISHIHARA K, et al.Stress- deformation and strength characteristic[C]// Proceedings of the 9th International Conference on Soil Mechanics and Foundation Engineering. Tokyo, 1977: 421-494. [2] MESRI G, CHOI Y K.The uniqueness of the end-of- primary (EOP) void ratio-effective stress relationship[C]// Proceedings of the 11th International Conference on Soil Mechanics and Foundation Engineering. San Francisco, 1985: 587-590. [3] MESRI G.Primary compression and secondary compression[J]. Geotechnical Special Publication, 2003, 119: 122-166. [4] BERRE T, IVERSEN K.Oedometer tests which different specimen heights on a clay exhibiting large secondary compression[J]. Géotechnique, 1972, 22(1): 53-70. [5] IMAI G., TANG Y X.A constitutive equation of one dimensional consolidation derived from inter-connected tests[J]. Soils and Foundations,Japanese Geotechnical Society, 1992, 32(2): 83-96. [6] KABBAJ M, TAVENAS F, LEROUEIL S.In situ and laboratory stress-strain relationships[J]. Géotechnique, 1988, 38(1): 83-100. [7] LEONI M, KARSTUNEN M, VERMEER PA.Anisotropic creep model for soft soils[J]. Géotechnique, 2008, 58(3): 215-226. [8] NASH D, BROWN M.Influence of destructuration of soft clay on time-dependent settlements: comparison of some elastic viscoplastic models[J]. International Journal of Geomechanics, 2015, 15: 1-19. [9] KARIM M R, GNANENDRAN C T, et al.Predicting the long-term performance of a wide embankment on soft soil using an elastic-vicoplastic model[J]. Canadian Geotechnical Journal, 2010, 47(2): 244-257. [10] 殷建华, JACK I C.土体与时间相关的一维应力-应变性状、弹黏塑性模型和固结分析[J]. 岩土力学, 1994, 15(3): 65-80. (YIN Jian-hua, JACK I C.One-dimensional time dependent stress-strain behaviour of soils, elastic visco-plastic modelling, and consolidation analysis[J]. Rock and Soil Mechanics, 1994, 15(3): 65-80. (in Chinese)) [11] YIN J H, FENG W Q.A new simplified method and its verification for calculation of consolidation settlement of a clayey soil with creep[J]. Canadian Geotechnical Journal, 2015, 54(3): 1-46. [12] 姚仰平, 孔令明, 胡晶. 考虑时间效应的UH模型[J]. 中国科学, 2013, 43(3): 298-314. (YAO Yang-ping, KONG Ling-ming, HU Jing.UH model considering temperature effects[J]. Science China Press, 2013, 43(3): 298-314. (in Chinese)) [13] STOLLE D F E, VERMEER P A, BONNIER P G. A consolidation model for creeping clay[J]. Canadian Geotechnical Journal, 1999, 36: 754-759. [14] VERMEER P A, NEHER H P.A soft soil model that accounts for creep[C]// Beyond 2000 in Computational Geotechnics-10 Years of PLAXIS. Rotterdam: Balkema, 1999: 249-262. [15] FENG W Q, YIN J H.A new simplified Hypothesis B method for calculating consolidation settlements of double soil layers exhibiting creep[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2017, 41: 899-917. [16] MADASCHI A, GAJO A.A one-dimensional viscoelastic and viscoplastic constitutive approach to modeling the delayed behavior of clay and organic soils[J]. Acta Geotechnica, 2017, 12: 827-847. [17] 尹振宇. 天然软黏土的弹黏塑性本构模型:进展及发展[J]. 岩土工程学报, 2011, 33(9): 1357-1369. (YIN Zhen-yu.Elastic viscoplastic models for natural soft clay: review and development[J]. Chines Journal of Geotechnical Engineering, 2011, 33(9): 1357-1369. (in Chinese)) [18] LEROUEIL S, KABBAJ M, TAVENAS F, et al.Stress-strain-strain rate relation for the compressibility of sensitive natural clays[J]. Géotechnique, 1985, 35(2): 159-180. [19] CRAWFORD C B.Interpretation of the consolidation test[J]. Journal of the Soil Mechanics and Foundation Division, 1964, 90(5): 87-102. [20] BJERRUM L.Embankments on softground: state of the art report[C]// Proceedings of Speciality Conference on Performance of Earth and Earth Supported Structures. Hosier State: Purdue University, 1972: 1-54. [21] BERRY P L, POSKITT T J.The consolidation of peat[J]. Géotechnique, 1972, 22(1): 27-52.