煤样分级加载蠕变破坏试验研究

Study on creep failure of coal specimen subjected to step loading

为深入研究煤样分级加载蠕变的能量演化及损伤破坏特征,采用岛津AX-G250试验机对煤样进行了分级加载蠕变试验。试验结果表明:应力水平对煤样蠕变过程有显著影响,在煤样破坏前的蠕变应力水平,随蠕变应力的提高,初始减速蠕变阶段持续的时间逐渐增大;煤样分级加载蠕变能量演化过程分为能量停滞、能量稳定增加、能量显著增加和能量释放4个阶段;随蠕变应力水平的提高,弹性能耗比呈“U”型演化规律。基于耗散能量法的损伤公式表明:煤样分级加载蠕变损伤过程可分为损伤线性增加和损伤非线性显著增加2个阶段,后一阶段的出现可作为煤样分级加载蠕变破坏的前兆。

In order to further study the energy evolution and damage failure of coal specimen subjected to step creep loading,the Shimadzu AX-G250 test machine was used to carry out the creep test of coal specimen subjected to step loading.Test results show that the stress level has a significant influence on the creep process of the coal specimen,the creep stress level before the coal specimen failure,with the increase of the creep stress,the duration of the initial deceleration creep phase gradually increases.The energy evolution can be divided into four phases,namely:energy stagnation,steady energy increase,significant energy increase,and energy release phases.With the increase of creep stress level,the ratio of elastic energy to dissipated energy presents a“U”-typed evolution law.The damage equation based on the dissipated energy method shows that the creep damage process of coal specimen subjected to step loading can be divided into the linear increase and non-linear significant increase phases;and the appearance of the latter phase can be used as the precursor of coal specimen creep failure subjected to step loading.