基于能耗理论的岩石三维蠕变本构模型及临界分段

目前对岩石加速蠕变阶段的启动判定仍是一个难点。为了反映岩石蠕变全过程,基于能量耗散理论,结合蠕变速率特征,以耗散率值作为蠕变三阶段的控制阈值,对蠕变阶段进行临界分段。引入Perzyna黏弹塑性理论,应用到Cvisc元件模型中,建立一种新的加速蠕变启动判定方式的蠕变本构模型,并将其拓展为三维情形。开展砂岩三轴压缩蠕变试验,分析蠕变速率变化特征,研究等时应力-应变关系,提取模型临界分段参数。引用相关文献中泥岩和冻结软岩蠕变试验数据,通过所建模型对3种岩石蠕变试验数据进行辨识,对比试验曲线和预测曲线,验证所建模型描述岩石加速蠕变阶段的优越性,充分显示出所建模型表征蠕变力学行为的合理性和适用性。研究成果为岩石蠕变阶段的划分及力学行为的模拟提供一种新思路。

Three-dimensional Creep Constitutive Model and Critical Segment of Rock Based on Energy Consumption Theory

Determining the incipience of accelerated creep stage of rock is still a difficulty at present. With energy dissipation rate as a control threshold, we divided the creep of rock into critical segments in consideration of creep rate to reflect the whole process of creep. By applying the Perzyna viscoelastic-plastic theory to the Cvisc element model, we established a creep constitutive model to determine the incipience of accelerated creep stage and expanded into three-dimensional scale. Furthermore, we conducted triaxial compressive creep test on sandstone to analyze creep rate change, isochronous stress-strain relation, and extract critical segment parameters. In the meantime, we collected creep test data of mudstone and frozen soft rock in previous studies. We applied the proposed model to identify the aforementioned creep test data of sandstone, mudstone, and frozen soft rock. By comparing the test data with the modelled data, we verified the rationality and applicability of the model in characterizing creep behavior. The research findings offer a novel idea for creep staging and mechanics modelling.