卸围压下弱胶结软岩分数阶蠕变损伤本构模型

为研究地下硐室开挖卸荷诱发的软岩蠕变损伤特征,以西部矿区弱胶结软岩为研究对象,利用GDS HPTAS开展了分级卸围压蠕变试验,研究了不同含水条件下弱胶结软岩卸围压下蠕变特征和蠕变速率特征。基于稳态蠕变速率倒数的方法,确定了弱胶结软岩长期强度和含水率的数学指数函数关系。基于蠕变速率曲线特征提出了一种确定衰减蠕变与等速蠕变分界点t_1和等速蠕变与加速蠕变分界点t_2的新方法。引入Riemann-Liouville分数阶积分算子和负时间指数损伤演化变量,定义了非线性损伤Abel黏壶,建立了一个包括弹性元件、黏弹性损伤元件、黏性元件和非线性黏塑性损伤元件的六元件分数阶蠕变损伤本构模型。基于试验结果,采用Trust-Region算法进行了模型参数识别和敏感性分析。结果表明,所建立的模型具有物理意义明确、与试验值吻合度较高等特点,可较为准确地反映开挖卸荷条件下弱胶结软岩蠕变损伤特性,对保障地下工程长期稳定性具有重要的意义。

This study investigates the creep damage characteristics of weakly cemented soft rock induced by excavation and unloading in an underground chamber,focusing on samples from the western mining area.A series of multi-stage unloading confining pressure creep tests on weakly cemented soft rock was conducted using GDS HPTAS.Under different water conditions,the creep characteristics and creep rate characteristics of weakly cemented soft rock were studied under confining pressure unloading.Based on the reciprocal steady creep rate method,the mathematical exponential function relationship between long-term strength and water content of weakly cemented soft rock was determined.By introducing the Riemann-Liouville fractional order integral operator and the negative time exponential damage evolution variable,nonlinear damage Abel clay pot was defined,and a six-element fractional order creep damage constitutive model,including elastic elements,viscoelastic damage elements,viscous damage elements and nonlinear viscoplastic damage elements,was established.Based on the experimental results,the Trust-Region algorithm in Matlab was used to identify the model parameters and analyze the sensitivity.The results show that the established model has clear physical significance and high agreement with the test values.It can accurately reflect the creep damage characteristics of weakly cemented soft rock under excavation and unloading confining pressure in underground engineering,which is significant for ensuring the long-term stability of underground engineering.