煤单轴抗压强度特性的加载速率效应研究

为考察加载速率对煤单轴抗压强度特性的影响规律,利用TAW-2000型电液伺服岩石力学试验系统对取自山西省正利煤矿的4~(-1)号煤进行了不同加载速率下的力学性能测试,研究了峰值强度、弹性模量、轴向应变等与加载速率的关系,并探讨了试件可释放弹性应变能与耗散应变能随加载速率的变化规律。研究表明:1)与硬脆岩石不同,煤样的峰值强度随着加载速率的增大呈现先增高后降低的趋势。2)煤样的损伤应力与加载速率呈负相关。3)加载速率越快,试件轴向载荷增加越快,但当加载速率超过1.16×10~(-3) mm/s后载荷增加速度基本稳定。加载速率越快,试件损伤应力出现的越早,试件破坏越快。4)单轴压缩试验第Ⅰ阶段煤样耗散应变能转化速率均处于较低水平,且与加载速率呈负相关,第Ⅱ阶段耗散应变能随加载速率的增加大致呈先增大后减小的趋势,各煤样耗散应变能转化速率的最大值均出现在峰值点或峰后轴向应力陡然跌落点。

Research on loading rate effect of uniaxial compressive strength of coal

In order to investigate how the loading rate affects the uniaxial compressive strength of coal, the mechanical properties testing of 4-1 coal from Zhengli coal mine in Shanxi province has been carried out with the TAW-2000 electro-hydraulic servo rock mechanical experimental system. The correlation between peak strength, elastic modulus, axial strain and loading rate has been studied, and how the re-lease and dissipation of elastic strain energy react with loading rate has also been discussed. The results of the study are as follows: 1) Unlike the brittle rocks, the peak strength of the coal samples will in-crease as the loading speed grows, but there is a critical value when the rate exceeds, the strength will decrease. 2) The damaging stress of the coal samples has negative correlation with the loading rate. 3) The quicker the loading rate becomes, the faster the axial stress grows. But when it exceeds 1.16×10-3 mm/s, the increment of the load would be stable. And the faster the rate is, the earlier damaging stress could be observed, and also the faster the samples could be damaged. 4) Conversion rate of the strain energy dissipation is relatively low in the first phase of the uniaxial compression tests, and has a nega-tive correlation with the loading rate. In the second phase, the dissipation strain energy first increases and then decreases as the loading rate increases. The maximum conversion rate of strain energy dissipa-tion occurs at the peak point or the point where axial the stress falls abruptly after the peak point on stress-strain curve.