变加载方式灰岩蠕变试验研究

打破单轴压缩蠕变试验传统的加载方式,改变加载速率和荷载增量法进行单试件逐级增量加载。瞬时加载阶段的轴向应变有如下特征:第一阶段各级的轴向应变速率随荷载级别的增加而降低,且大于第二阶段和过渡阶段所有级别的轴向应变速率。岩石在整个蠕变试验过程中,瞬时应变以硬化机制占主导地位,蠕变应变时颗粒进行受力调整,且加载速率与受力调整时间呈负相关。基于经典的Nishihara模型,参考前人研究成果,建立了能同时体现瞬时蠕变、稳态蠕变和与损伤演化过程有关的加速蠕变三阶段的蠕变本构模型。

Experimental Research of Varied Loading Method on Creep of Limestone

Traditional loading method of uniaxial compressive creep test was broken to conduct stepwise incremental loading on one sample by changing loading rate and load increment. Axial strain features during instantaneous loading stage were as follows:Axial strain rate of each level of the first stage showed reduction with the increase of load level, and was higher than that of both the second stage and the transition stage. During the whole creep test, strain harding mechanism was dominant in instantaneous loading strain stage. Mineral grain was deduced undergoing force adjustment tends to be inversely related to loading rate during creep strain stage. According to classical Nishihara model together with previous research results, creep constitutive model was established, which can reflect instantaneous loading strain, steady creep and accelerated creep incorporating damage evolution process.