为研究深部灰岩蠕应变特性,采用GDS-VIS三轴流变仪对不同深度试样做分级加载单轴蠕变试验。基于试验结果,计算出灰岩长期强度与瞬时强度之比的均值为0.758,且深度越深比值越小;分析不同深度灰岩在各分级应力水平下轴向蠕应变增量与加载级数的变化规律,并将蠕应变增量进行一次累加,得到轴向蠕应变。结果表明:蠕应变增量随级数的增加呈现先减小后剧增的变化规律,且随深度增加,蠕应变增量达到谷底所对应的应力百分比有明显增大趋势;在分级加载过程中,随级数增加,轴向蠕应变先后呈现减速增加、等速增加和加速增加3个发展阶段;当恒载应力百分比为60%~70%时,蠕应变趋于稳定,当超过该范围后,蠕应变加速增加直至发生蠕变破坏。研究得到的这一应力百分比范围可以为识别深部灰岩是否会发生蠕变破坏提供依据。
Abstract
In the aim of exploring the creep characteristics of deep limestone, uniaxial creep tests were conducted with GDS-VIS triaxial rheometer by step loading on specimens from different depths. According to the test results, the mean value (0.758) of the ratio of long-term strength to instantaneous strength decreases as depth increases. Furthermore, the variation law of axial creep strain increment of limestone in different depths under different stress levels was investigated, and then axial creep strains were obtained by accumulating creep strain increment. Results revealed that creep strain increment decreased first and then increased dramatically with the increasing of stress level. As depth increased, the percentage of stress corresponding to the minimum creep strain increment obviously increased. Moreover, with the increase of loading level, the axial creep strain experienced three development stages from decelerated growth, constant growth and accelerated growth. When the stress percentage ratio of constant load was within the range from 60% to 70%, creep strain tended to be stable; whereas beyond the range, the creep strain acceleratedly increased until creep failure. Therefore, the range of stress percentage could be taken as reference for identifying whether creep failure will happen or not for deep limestone.
关键词
采矿工程 /
深部灰岩 /
蠕应变特性 /
单轴蠕变试验 /
分级加载 /
长期强度
Key words
mining engineering /
deep limestone /
creep strain characteristics /
uniaxial creep test /
step loading /
long-term strength
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