考虑先期卸荷静偏应力的花岗岩残积土动力特性研究

舒荣军1,2,孔令伟1,2,黎澄生3,刘炳恒1,2,简涛1,2

振动与冲击 ›› 2022, Vol. 41 ›› Issue (17) : 93-100.

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振动与冲击 ›› 2022, Vol. 41 ›› Issue (17) : 93-100.
论文

考虑先期卸荷静偏应力的花岗岩残积土动力特性研究

  • 舒荣军1,2,孔令伟1,2,黎澄生3,刘炳恒1,2,简涛1,2
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Dynamic characteristics of granite residual soil considering pre-unloading static deviatoric stress

  • SHU Rongjun1,2, KONG Lingwei1,2, LI Chengsheng3, LIU Bingheng1,2, JIAN Tao1,2
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文章历史 +

摘要

先期静偏应力对土体的动力特性具有重要影响,以往的研究多侧重于加载引起的静偏应力,考虑先期卸荷作用影响的土体动力性质试验研究还很少见。围绕先期卸荷条件下原状花岗岩残积土的动力响应特征,开展了一系列包含先期卸荷阶段的动态三轴试验;基于土体强度包络线、试样固结及卸荷后应力状态三者之间的位置关系定义了卸荷度,用于表征实践中受诸多因素影响的土体应力释放程度,卸荷度反映了卸荷土体距离破坏状态的相对远近;根据试验结果分析了动应力幅值和卸荷度对土体累积塑性变形和动强度的影响规律。结果表明:随着动应力幅值的增大,轴向塑性变形累积模式加速向“破坏型”发展;先期卸荷作用助长了花岗岩残积土的轴向累积塑性变形,间接表现为临界动应力幅值随卸荷度的增大而减小,且此种助长效应随卸荷度的增大呈非线性(加速)增强趋势;相同循环周次下,花岗岩残积土的动强度随卸荷度的增大而减小。在此基础上,以临界动应力幅值为归一化因子,发现不同卸荷度下土体的动强度曲线可归一化为唯一的曲线,据此建立了可考虑先期卸荷程度影响的花岗岩残积土动强度表达式。
关键词:花岗岩残积土;卸荷;静偏应力;累积变形;动强度

Abstract

Static deviator stress prior to cyclic loading imposes great influences on the dynamic behaviour of soil. So far most of pertinent studies focused on static deviator stress caused by loading, whereas very few considered the influences of preceding unloading on the dynamic behaviour of soil. To understand the effects of static deviator stress caused by preceding unloading on the dynamic behaviour of undisturbed granite residual soil, a series of cyclic triaxial tests after unloading were performed. According to the positional relationship among soil strength envelope, consolidation stress state and the stress state just after unloading, the degree of unloading of a specimen was quantified, which can be affected by many factors in practice and reflects how far soil stress state is from failure. The influences of amplitude of cyclic stress and degree of unloading on accumulated axial plastic strain and dynamic strength characteristics were investigated. The experiment results show that the increase of amplitude of cyclic stress accelerates the transition of the accumulating mode of axial plastic strain from “stabilization” to “failure” type. The preceding unloading promotes the accumulated axial plastic deformation of the granite residual soil, as a result of which critical amplitude of cyclic stress decreases with the increase of degree of unloading. As the degree of unloading increases, the promoting effect of preceding unloading on soil deformation grows nonlinearly (faster and faster). At the same number of cycles, dynamic strength of the soil decreases with the increase of degree of unloading. In addition, dynamic strength curves under different degrees of unloading can be normalized by the corresponding critical amplitude of cyclic stress, and a unique normalized strength curve can be obtained, based on which an empirical formula was proposed for the prediction of dynamic strength of the granite residual soil, considering the effects of degree of unloading.
Key words: granite residual soil; unloading; deviator stress; accumulated deformation; dynamic strength

关键词

花岗岩残积土 / 卸荷 / 静偏应力 / 累积变形 / 动强度

Key words

granite residual soil / unloading / deviator stress / accumulated deformation / dynamic strength

引用本文

导出引用
舒荣军1,2,孔令伟1,2,黎澄生3,刘炳恒1,2,简涛1,2. 考虑先期卸荷静偏应力的花岗岩残积土动力特性研究[J]. 振动与冲击, 2022, 41(17): 93-100
SHU Rongjun1,2, KONG Lingwei1,2, LI Chengsheng3, LIU Bingheng1,2, JIAN Tao1,2. Dynamic characteristics of granite residual soil considering pre-unloading static deviatoric stress[J]. Journal of Vibration and Shock, 2022, 41(17): 93-100

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