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中南大学学报(自然科学版)

Journal of Central South University

第43卷    第5期    总第213期    2012年5月

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文章编号:1672-7207(2012)05-1885-09
不同应力路径下卸围压流变试验分析及模型辨识
杨文东1, 2,张强勇2,陈芳2,李文纲3,王建洪3,贺如平3,曾纪全3

(1. 中国石油大学(华东) 储运与建筑工程学院,山东 青岛,266580;
2. 山东大学 岩土与结构工程研究中心,山东 济南,250061;
3. 中国水电顾问集团 成都勘测设计研究院,四川 成都,610072
)

摘 要: 以大岗山水电站坝基的辉绿岩为研究对象,进行σ1恒定卸围压和σ13恒定卸围压流变试验,分析2种不同应力路径下辉绿岩的流变变形特征。引入屈服接近度指标来评价卸围压流变过程中不同三向应力状态下岩样临近屈服破坏的程度,并以此作为试验曲线中等速蠕变和加速蠕变的区分标准。最后对Burgers模型进行参数变异处理。研究结果表明:在2种方式下和在卸围压过程中,岩样的横向变形都表现为侧向膨胀,但轴向变形规律并不相同:σ1恒定时轴向变形一直轴向压缩,而σ13恒定时先是有微小增大再逐渐转变为轴向压缩。这说明随着围压的不断卸载,岩体变形逐渐由弹性向塑性转变并最终破裂,线弹性理论已不再适用。加速蠕变阶段的串联黏滞系数出现了非线性变化,以此来描述加速蠕变。参数变异的Burgers模型可以描述岩体的减速、等速和加速蠕变阶段,拟合结果与试验结果吻合较好。

 

关键字: 岩石力学;卸围压流变试验;屈服接近度;卸荷应力路径

Analysis of unloading confining pressure rheological tests in different stress paths and model identification
YANG Wen-dong1, 2, ZHANG Qiang-yong2, CHEN Fang2, LI Wen-gang3,
WANG Jian-hong3, HE Ru-ping3, ZENG Ji-quan3

1. College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, China;
2. Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan 250061, China;
3. Chengdu Hydroelectric Investigation & Design Institute,
China Hydropower Engineering Consulting Group Corporation, Chengdu 610072, China

Abstract:The unloading triaxial rheological tests by keeping σ1 and unloading lateral stress or by keeping σ13 and unloading laterals stress by steps were performed in laboratory with diabase samples taken from Dagangshan hydropower station dam foundation. The rheological deformation characters by the two different stress path were analyzed. The yield approach index (YAI) was introduced to evaluate the close degree from the yield surface of sample in triaxial stress state in the unloading confining pressure rheological process and used as the standard in distinguishing the steady-state creep and tertiary creep in test curves. The results show that in the two modes, the lateral deformation shows both lateral dilasions in process of unloading confining pressure, but the axial deformation characters are different. The sample shows compression in axial deformation when tested with constant σ1, while when tested with constant σ13 a tiny elongation and gradual transformation to axial compression. With the unloading of confining pressure, the deformation is transferred from elasticity to plasticity, and thus linear elastic theory is no longer applicable. The Burgers model is improved to have variable parameters which take the nonlinear deterioration of viscous coefficient in the tertiary creep stage into consideration. The improved model with variable parameter performs better in describing the transient creep, steady-state creep and tertiary creep in the fitting test.

 

Key words: rock mechanics; unloading confining pressure rheological tests; yield approach index; unloading stress path

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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