饱和岩石循环冻融蠕变力学特性及损伤分析

Mechanical Properties and Damage Analysis of Cyclic Freeze-thaw Creep of Saturated Rock

为研究饱和岩石循环冻融条件下的蠕变力学特性,开展了不同饱和冻融次数三轴蠕变力学试验。根据试样变形特征建立了弹黏塑性蠕变模型,计算了蠕变模型相关参数,研究了饱和循环冻融相关参数变化特征。分析了随冻融次数增加裂隙扩展发育规律,提出了循环冻融蠕变损伤模型,基于试验数据对损伤模型进行了验证。研究表明:饱和循环冻融蠕变过程分为过渡蠕变阶段,稳定蠕变阶段和加速蠕变阶段3个阶段,冻融次数增加蠕变各个阶段均呈缩短趋势。建立弹黏塑性蠕变模型基础上,总结相关蠕变参数随加载应力增加均呈现增大趋势,随冻融次数增加,相同应力条件下蠕变参数逐渐减小。冻融过程中裂隙发育主要分为两种:沿原有裂隙扩展和独立发育的裂隙。原有裂隙扩展速度大于独立发育裂隙产生速度。试样循环冻融过程中裂隙发育速度逐渐增大。考虑冻融次数对蠕变参数的影响,同时引入损伤系数对其影响结果修正,建立蠕变损伤模型解释了循环冻融蠕变损伤过程,模型理论曲线与试验数据对比显示具有较好的相关性,验证了蠕变损伤模型的正确性。

In order to study the creep mechanical properties of saturated rock under cyclic freeze-thaw conditions,triaxial creep tests were carried out with different times of freeze-thaw cycles.An elastic-viscoplastic creep model was established based on the deformation characteristics of the specimen,and the parameters of the creep model were calculated.The creep damage model of cyclic freezing-thawing process was proposed,and the damage model was verified based on the experimental data.The results show that the freeze-thaw creep process is divided into three stages:transition creep stage,stable creep stage and accelerated creep stage.Based on the elastoviscoplastic creep model,it is concluded that the creep parameters increase with the increase of loading stress,and decrease with the increase of freezing and thawing times.There are two kinds of fissures during freezing and thawing:the fissures extending along the original fissures and the fissures developing independently.The growth velocity of the original fracture is higher than that of the independently developed fracture.The growth rate of cracks increases gradually in the process of cyclic freezing-thawing.Considering the effect of freezing-thawing times on creep parameters and the effect of damage coefficient on creep parameters,a creep damage model is established to explain the creep damage process of cyclic freezing-thawing,the theoretical curve of the model shows good correlation with the test data,which verifies the correctness of the creep damage model.