Nonlinear Elasto-Visco-Plastic Creep Behavior and New Creep Damage Model of Dolomitic Limestone Subjected to Cyclic Incremental Loading and Unloading
Nonlinear Elasto-Visco-Plastic Creep Behavior and New Creep Damage Model of Dolomitic Limestone Subjected to Cyclic Incremental Loading and Unloading
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DOI：
10.3390/su132212376
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发表时间：
2021-11-01
期刊：
影响因子：
3.9
通讯作者：
Zhu, Zheming
中科院分区：
文献类型：
--
作者：
Wang, Xingkai;Song, Leibo;Zhu, Zheming
对于许多岩石工程项目来说，在开挖过程中和长期运营阶段，围岩应力不断增大或减小。本文利用先进的岩石力学测试系统(MTS815.04)，研究了循环增量加卸载作用下白云岩灰岩的三轴蠕变行为。然后，从总应变曲线中分离出瞬时弹性应变、瞬时塑性应变、粘弹性应变和粘塑性应变分量，并分析了这些不同类型的应变随偏应力增量的变化规律。在此基础上，引入了考虑不可恢复塑性应变占总应变比例的损伤变量，并将新提出的损伤粘性体与Hookean物质、St.Venant体和Kelvin单元串联，建立了新的非线性多元蠕变模型。对该新模型的参数进行了分析。研究结果表明：(1)当偏应力不大于抗压强度的75%时，岩石变形主要表现为瞬时变形、瞬时蠕变和稳态蠕变变形，而不可恢复的瞬时塑性应变占总瞬时应变的38.02~60.27%；(2)偏应力越大，蠕变变形越明显。粘弹性应变随偏应力的增加呈线性增长，尤其是不可恢复的粘塑性应变随偏应力的增加呈指数增长，最终导致试件的加速蠕变和延迟破坏；(3)基于实验数据，验证了所提出的非线性蠕变模型能够较好地描述试件的全蠕变阶段，特别是第三蠕变阶段。这些结果加深了对白云质石灰岩弹粘塑性变形行为的认识，对地下岩石工程的安全开挖和长期稳定具有一定的理论和实际意义。
For many rock engineering projects, the stress of surrounding rocks is constantly increasing and decreasing during excavating progress and the long-term operation stage. Herein, the triaxial creep behavior of dolomitic limestone subjected to cyclic incremental loading and unloading was probed using an advanced rock mechanics testing system (i.e., MTS815.04). Then, the instantaneous elastic strain, instantaneous plastic strain, visco-elastic strain, and visco-plastic strain components were separated from the total strain curve, and evolutions of these different types of strain with deviatoric stress increment were analyzed. Furthermore, a damage variable considering the proportion of irrecoverable plastic strain to the total strain was introduced, and a new nonlinear multi-element creep model was established by connecting the newly proposed damage viscous body in series with the Hookean substance, St. Venant body, and Kelvin element. The parameters of this new model were analyzed. The findings are listed as follows: (1) When the deviatoric stress is not more than 75% of the compressive strength, only instantaneous deformation, transient creep, and steady-state creep deformation occur, rock deformation is mainly characterized by the instantaneous strain, whereas the irrecoverable instantaneous plastic strain accounts for 38.02-60.27% of the total instantaneous strain; (2) Greater deviatoric stress corresponds to more obvious creep deformation. The visco-elastic strain increases linearly with the increase of deviatoric stress, especially the irrecoverable visco-plastic strain increases exponentially with deviatoric stress increment, and finally leads to accelerated creep and delayed failure of the sample; (3) Based on the experimental data, the proposed nonlinear creep model is verified to describe the full creep stage perfectly, particularly the tertiary creep stage. These results could deepen our understanding of the elasto-visco-plastic deformation behavior of dolomitic limestone and have theoretical and practical significance for the safe excavation and long-term stability of underground rock engineering.