采用分级加卸载方式,利用五联流变实验系统对陕煤集团神木柠条塔矿业有限公司砂岩进行单轴蠕变试验。针对岩石蠕变的衰减、稳定和加速三阶段特征,将Burgers模型中串联的牛顿体的黏滞系数修正为与应力、时间相关的函数,考虑损伤在蠕变过程中的影响,基于损伤理论和Lemaitre应变等价性假说,建立损伤体模型。将Hooke体、Kelvin模型、修正牛顿体和损伤体四者串联组成一个新的非线性损伤蠕变模型,推导新模型的本构方程和蠕变方程,该模型以一个统一的函数描述岩石在不同应力水平下的蠕变曲线。基于单轴蠕变试验结果,对模型参数进行辨识和敏感性分析,将新模型与试验蠕变曲线对比。结果表明:模型能很好地拟合岩石蠕变,模型无须采用分段函数即可描述砂岩蠕变的全过程,弥补了Burgers模型无法描述加速蠕变的不足,从而验证新模型的合理性。
Abstract
Uniaxial creep experiments were conducted on sandstone samples obtained from Ningtiaota coal mine in Shaanxi using a five-connected rheological test system by which step loading and unloading were applied. In view of decaying, stable and accelerating stages within total creep, the Newton body in the Burgers constitutive model was modified by creating a new function with stress and time. In consideration of the effect of damage in the process of creep, a damage body was proposed based on the damage theory and Lemaitre's hypothesis. The Hooke body, Kelvin body, the modified Newton body, and the proposed damage body were combined to build a new nonlinear damage creep model and the constitutive model and creep function were also derived. The creep curves under various stress levels were described by the established nonlinear damage creep model. Moreover, parameters of the established damage model were fitted and the sensitivity of fitting parameters was analyzed according to the creep experimental data. Results suggest that the proposed damage model could well fit and describe the whole process of the creep of sandstone with no need of segmented functions, and hence overcoming the shortcoming of Burgers model in reflecting the accelerating creep stage.
关键词
砂岩 /
分级加卸载 /
修正牛顿体 /
损伤蠕变模型 /
全过程蠕变
Key words
sandstone /
step loading and unloading /
modified Newton body /
damage creep model /
total creep
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基金
国家自然科学基金项目(41572334,11572344);国家重点研发计划资助项目(2016YFC0600901);中央高校基本科研业务费专项(2010YL14)
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