卸荷破裂岩体非定常分数阶蠕变模型

Unsteady Fractional Creep Model of Unloading Fractured Rock Mass

针对锦屏一级水电站地下厂房大理岩赋存环境地应力高的特点,通过室内试验将完整大理岩试件制备为卸荷作用下形成的含破裂面试件,并对卸荷破裂岩体试件进行了三轴蠕变试验,揭示了卸荷破裂岩体轴向和横向蠕变特征及围压效应。恒定荷载下,卸荷破裂岩体横向变形较轴向变形具有更显著的蠕变特征,且围压对横向蠕变发展的限制作用更明显。针对卸荷破裂岩体蠕变的非线性特征及横向蠕变特征,采用Koeller分数阶粘弹性体替换了广义开尔文体中的牛顿体,并考虑模型参数在应力与时间影响下的非定常特性,结合扩容比时间关系方程,建立了能全面描述卸荷破裂岩体横向蠕变特征的非定常分数阶模型。试验结果对比模型结果表明该模型能够较好地描述卸荷破裂岩体轴向与横向蠕变的非线性特征,对于研究高应力、强卸荷作用下地下硐室围岩侧向长期变形具有一定参考意义。

Considering the high in-situ stress of the marble in the underground powerhouse of Jinping I Hydropower Station,the intact marble samples were prepared into fractured specimens through unloading triaxial tests in the laboratory,and then triaxial creep tests were conducted on the unloading fractured marble specimens to reveal the axial and lateral creep properties and confining pressure effect.Under the constant axial stress,the lateral deformation of unloading fractured marble exhibits more significant creep characteristics than axial deformation.Besides,the effect of confining pressure on lateral creep deformation is more obvious.In terms of the nonlinear characteristics of creep and the obvious lateral creep of unloading fractured marble,the Newton dashpot in the generalized Kelvin model was replaced by a Koeller fractional dashpot.Meanwhile,considering the unsteady characteristics of model parameters under the influence of stress and time,and combing with the equation of the expansion ratio-time relationship,an unsteady fractional model that can comprehensively describe the lateral creep characteristics of unloaded fractured marble was established.The test results verified that the model can better describe the nonlinear creep characteristics of the axial and lateral deformation,which is critical for studying lateral deformation of surrounding rock under high stress and strong unloading conditions.