DEM analysis of evolution law of bond degradation for structured soils
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摘要: 结构性土体通常指粒间含有胶结的土体,可看成一种特殊的胶结颗粒材料,探明结构性土体的胶结破损演化规律是加深结构性土体宏微观力学性质认识及建立结构性土本构模型的关键。由于试验手段难以定量获取胶结破损信息,通过离散单元法分析了结构性土体的胶结破损演化规律。首先采用相对完备的胶结接触模型建立了结构性土体离散元试样,接触模型考虑了颗粒及胶结物质的抗转动和抗扭转作用以及胶结尺寸对刚度和强度的影响；然后开展了结构性土侧限压缩、等向压缩、等应力比压缩以及常规三轴和真三轴试验的离散元数值分析,再现了结构性土的主要宏观力学特征；在此基础上的胶结破损演化分析表明胶结破损参量B0演化具有明显的应力路径相关性,而新提出的破损参量Bσ应力路径相关性低,通过Bσ与等效塑性应变的指数函数关系,可以描述结构性土体的胶结破损演化情况。
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关键词:
- 结构性土 /
- 胶结颗粒材料（理想结构性土） /
- 离散单元法 /
- 胶结破损演化 /
- 本构模型
Abstract: The evolution of bond degradation is essential for analyzing the macro-and micro-scopic behaviors and establishing constitutive models for structured soils with cementation bond which is a kind of bonded granular material. The discrete element method is employed to analyze the evolution of bond degradation on account of the disadvantage of laboratory tests in bond breakage quantitative analysis. First, the discrete numerical sample is generated by installing a relatively completed bond contact model incorporating the interparticle rolling and twisting resistances and the influences of bond size on the contact stiffness and strength. The DEM simulation reproduces the key mechanical behaviors of one-dimensional compression, isotropic and anisotropic compressions, conventional triaxial and true triaxial tests on the DEM sample. The results show that the evolution of the degradation variable B0 is stress-path-dependent, while a new degradation variable Bσ is roughly stress-path-independent. An exponential function is recommended for Bσto describe the degradation of soil structure. -
土工测试专业委员会自成立以来，开展了一系列的学术研讨活动，迄今已举办30届全国土工测试学术研讨会。进入21世纪以来，因气候变化和全球变暖导致极端气候事件增多，暴雨、滑坡、泥石流等自然灾害频发，给岩土工程建设和土工测试技术带来了前所未有的挑战，在对环境保护、可持续发展和数字经济越来越重视的趋势下，工程建设需要更加精准地评估岩土参数，对土工测试技术的发展提出了更高要求。
土工测试技术的发展不仅能够促进岩土工程设计的优化，也能够推动岩土工程理论的创新。为促进相互交流学习，第30届全国土工测试学术研讨会围绕土的基本性质测试、土工物理模型测试、土工原位测试、现场土工监测、环境土工测试、特殊土测试等方面进行了广泛的学术交流。
第30届全国土工测试学术研讨会于2023年8月18—20日在北京召开，会议由中国土木工程学会土力学及岩土工程分会和中国水利学会岩土力学专业委员会共同主办，中国水利水电科学研究院、南京水利科学研究院、长江科学院等14家单位承办。会议筹办期间共收到110篇学术论文，经审稿委员会审议向《岩土工程学报》（增刊）荐论文56篇。同时，本届研讨会举办了细粒土三轴压缩平行试验，共收到19家单位的试验成果。本次会议以“探索•创新”为主题，会议设主会场1个，分会场4个，参会报名约60家单位，共组织特邀报告24个、主题报告64个。论文和报告涉及内容丰富，既有对学科基础理论的深入探讨，又有针对工程实践的案例分析和经验总结，这种跨学科的研讨有力地推动了土工测试领域的发展。
感谢对本届会议的召开鼎力相助的中国水利水电科学研究院及各有关单位，感谢向本届会议投稿并对因疫情而延期表示理解的各位专家和同行，感谢审稿专家对本次会议审稿工作的辛勤付出。尤其是《岩土工程学报》编辑部，为使本届会议的论文集面世，做了大量工作，专门编辑出版了本期增刊，特此表示感谢。
第30届全国土工测试学术研讨会组委会 -
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图 6 不同应力路径下破损参量B0随塑性体应变和塑性偏应变的演化规律
Figure 6. Evolution of degradation variable B0 versus plastic volumetric and deviator strain for DEM sample under different stress paths
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图 7 不同应力路径下破损参量B0随等效塑性应变的演化规律
Figure 7. Evolution of degradation variable B0 versus equivalent plastic strain for DEM sample under different stress paths
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