Constitutive model of structured loess incorporating the breakage law obtained by discrete element method
HU Haijun1，2，JIANG Mingjing2
(1. College of Water Resources and Architectural Engineering，Northwest Agricultural and Forestry University，Yangling，Shaanxi 712100，China；2. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China)
Abstract：The strength and deformation character of structured loess are closely related to the breakage of internal microstructure and the breakage law of microstructure has not been measured by experiment due to the limitation of microstructure test technology. Hence the evolution law of the breakage parameter for ideal structured loess under loading and wetting，which is obtained by discrete element method(DEM)，is incorporated in the binary medium model with the form of strain sharing and the mechanical responses of the model are obtained to verify the reasonability of the breakage evolution law. Firstly，the constitutive equations are given，in which the model of bonding element adopts elastic model，frictional element adopts modified cam clay model and the formula form of breakage parameter are obtained from the numerical test on the ideal structured loess under loading and wetting. Secondly，the numerical program is compiled to verify the behavior of the model in one dimensional compression test，one dimensional wetting test，conventional triaxial compression test and the triaxial wetting test. The results indicate the model can reflect the deformation behavior of loess in one dimensional compression test and the relation between collapsibility coefficient and vertical pressure in one dimensional wetting test. It can simulate the variation of volumetric strain during shearing under different consolidation pressure，the variation of initial elastic modulus with confining pressure in conventional triaxial compression test and the wetting induced deformation law in triaxial wetting test. The effect of bonding element parameter on mechanical character is apparent. The breakage law obtained by DEM experiments is more reasonable than the existing law for triaxial compression test with strain-hardening behavior.
胡海军1，2，蒋明镜2. 引入离散元所得破损规律的结构性黄土本构模型[J]. 岩石力学与工程学报, 2016, 35(S1): 3241-3248.
HU Haijun1，2，JIANG Mingjing2. Constitutive model of structured loess incorporating the breakage law obtained by discrete element method. , 2016, 35(S1): 3241-3248.
沈珠江，章为民. 损伤力学在土力学中的应用[C]// 第三届全国岩土力学数值分析与解析方法讨论会论文集. 珠海：[s.n.]，1988：47-51.(SHEN Zhujiang，ZHANG Weimin. Application of damage mechanics in soilmechanics[C]// The 3th Chinese Conference of Numerical Simulation and Analysis of Geomaterial. Zhuhai：[s.n.]，1988：47-51.(in Chinese))
[2]
沈珠江. 土体变形特性的损伤力学模型[C]// 第五届全国岩土力学数值分析与解析方法讨论会. 武汉：武汉测绘科技大学出版社，1994：1-8.(SHEN Zhujiang. Deformation characteristics of damage mechanics model[C]// The 5th Symposium of Numerical Analysis and Analytical Method in Rock andSoil Mechanics. Wuhan：Wuhan University of Science and Technology of Surveying and Mapping Publishing House，1994：1-8.(in Chinese))
[3]
沈珠江. 黄土的损伤力学模型探索[C]// 第七届土力学及基础工程学术会议论文集. 北京：中国建筑工业出版社，1994：145-149. (SHEN Zhujiang. Approach to damage mechanic model of loess[C]// Proceedings of the 7th Soil Mechanics and Engineering Conference. Beijing：China Architecture and Building Press，1994：145-149.(in
Chinese))
[4]
沈珠江. 广义吸力和非饱和土的统一变形理论[J]. 岩土工程学报，1996，18(2)：1-9.(SHEN Zhujiang. Generalized suction and unified deformation theory for unsaturated soils[J]. Chinese Journal of Geotechnical Engineering，1996，18(2)：1-9.(in Chinese))
[5]
胡再强，沈珠江，谢定义. 结构性黄土的本构模型[J]. 岩石力学与工程学报，2005，24(4)：565-569.(HU Zaiqiang，SHEN Zhujiang，XIE Dingyi. Constitutive model of structural loess[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(4)：565-569.(in Chinese))
[6]
沈珠江，胡再强. 黄土的二元介质模型[J]. 水利学报，2003，(7)：1-6.(SHEN Zhujiang，HU Zaiqiang. Binary medium model for loess[J]. Journal of Hydraulic Engineering，2003，(7)：1-6.(in Chinese))
[7]
胡海军. 结构性黄土的宏微观特性及本构模型研究[博士学位论文][D]. 上海：同济大学，2013.(HU Haijun. Constitutive model and macro-micro behavior of structured loess[Ph. D. Thesis][D]. Shanghai：Tongji University，2013.(in Chinese))
[8]
蒋明镜，胡海军. 荷载和水作用下结构性黄土破损规律的离散元分析[J]. 岩土工程学报，2014，36(6)：989-997.(JIANG Mingjing，HU Haijun. Numerical analysis of degradation evolution of structured loess under loading，unloading and wetting by discrete element method[J]. Chinese Journal of Geotechnical Engineering，2014，36(6)：989-997.(in Chinese))
[9]
沈珠江. 结构性粘土的堆砌体模型[J]. 岩土力学，2000，21(1)：1-4.(SHEN Zhujiang. A masonry model for structured clays[J].Rock and Soil Mechanics，2000，21(1)：1-4.(in Chinese))
[10]
JIANG M J，HU H J，LIU F. A summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests[J]. Canadian Geotechnical Journal，2012，49(10)：1147-1157.
[11]
周晓艳.非饱和黄土的应力路径试验研究[硕士学位论文][D]. 杨陵：西北农林科技大学，2008.(ZHOUXiaoyan. Study on stress path tests of unsaturated loess[M. S. Thesis][D]. Yangling：Northwest Agriculture and Forestry University，2008.(in Chinese))
[12]
何军芳.原状黄土的应力路径本构关系研究[硕士学位论文][D].西安：西安理工大学，2008.(HE Junfang. Research on constitutive relation of intact loess considering complex stress path[M. S. Thesis][D]. Xi¢an：Xi¢an University of Technology，2008.(in Chinese))
[13]
邵生俊，周飞飞，龙吉勇.原状黄土结构性及其定量化参数研究[J].岩土工程学报，2004，26(4)：531-536.(SHAO Shengjun，ZHOU Feifei，LONG Jiyong.Structural properties of loess and its quantitativeparameter[J]. Chinese Journal of GeotechnicalEngineering，2004，26(4)：531-536.(in Chinese))
2016, Vol. 35 
