岩-煤组合体试样蠕变强度特性研究
Study on Creep Strength Characteristics of Rock-coal Composite Samples
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摘要: 为研究岩-煤组合体试样蠕变强度特性,制备了岩煤高比为1∶1的砂岩-煤组合体试样,分别进行了应力水平加载时长为2 h和6 h的分级加载蠕变试验,探讨了组合体试样蠕变强度与单一煤样蠕变强度的关系。结果表明:随着应力水平加载时长的逐渐增大,岩-煤组合体试样的蠕变强度、蠕变系数整体呈逐渐降低的趋势;A组组合体试样(应力水平加载时长为2 h)的平均蠕变强度为13.01 MPa,平均蠕变系数为92.02%;B组组合体试样(应力水平加载时长为6 h)的平均蠕变强度为11.39 MPa,平均蠕变系数为80.55%;与A组相比,B组组合体试样的蠕变强度、蠕变系数均降低了12.45%;组合体试样的蠕变强度主要是其内部煤样的蠕变强度决定的,但其值大于单一煤样蠕变强度,这主要是因为组合体试样是一个系统体,砂岩的蠕变变形和损伤减小了主要承载体-煤样的蠕变变形和损伤,组合体试样中的煤样则需要更高的分级应力才能发生加速蠕变破坏而导致其整体性破坏失稳;同时,煤样内原生缺陷的发育程度也影响着组合体试样以及单一煤样的蠕变强度。Abstract: In order to study the creep strength characteristics of rock-coal composite samples, the graded loading creep tests with loading time of 2 h and 6 h were conducted on the sandstone-coal composite samples with the height ratio of 1:1, respectively. And the relationship of creep strength between composite samples and single coal samples was discussed. The results show that the creep strength and creep coefficient of rock-coal composite sample decreased gradually with the increase of the loading time. The average creep strength of group A (loading time of 2 h) was 13.01 MPa and the average creep coefficient was 92.02%. While the average creep strength of group B (loading time of 6 h) was 11.39 MPa and the average creep coefficient was 80.55%. Compared with group A, both the creep strength and creep coefficient of group B decreased by 12.45%. The creep strength of the composite sample was mainly determined by the creep strength of the internal coal sample, but its value was larger than that of the single coal sample. This is mainly because the composite sample was a systematic body. The creep deformation and damage of sandstone reduced the creep deformation and damage of coal sample (the main bearing body in the composite sample). Coal samples in composite samples needed a higher graded stress for accelerating creep failure and to lead to overall failure and instability of the composite sample. At the same time, the development of primary defects in coal samples also affected the creep strength of composite samples and single coal samples.