基于巴西劈裂法的饱水煤样能量耗散特征研究

为研究饱水煤样拉伸破坏过程中的能量耗散规律,利用RMT-150B岩石力学实验系统对赵固二矿二1煤层煤样在自然和饱水状态下进行巴西圆盘劈裂实验,探讨了自然与饱水状态下煤样的应力、强度及能量变化。结果表明:巴西劈裂实验时,加载过程应力-时间关系与实验控制方式有关。采用载荷控制方式时,峰值前拉应力与时间呈良好线性关系,达到峰值时应力瞬间跌落为零,表现出明显脆性破坏特征;采用变形控制方式时峰值前拉应力与时间呈非线性关系,峰值后出现分次破坏特征;采用两种控制方式在巴西圆盘劈裂实验破坏前没有本质区别;两种状态下不同层位煤样抗拉强度和峰值能率存在差异,自然状态下层位煤样抗拉强度较高(1.80MPa),中层位煤样抗拉强度较低(1.23MPa),上层位煤样抗拉强度介于两者之间(1.52MPa),饱水后上中下层位煤样的抗拉强度和峰值能率均有不同程度降低,抗拉强度平均软化系数分别为0.65,0.61和0.61,平均峰值能率降幅为36.0%,56.1%和40.6%;两种状态下煤样抗拉强度与峰值能率大致呈线性关系,表明抗拉强度越高的煤样,能量耗散越少,煤样抗拉强度越低,能量耗散越多。

Study of Energy Dissipation Characteristics of Saturated Coal Sample Based on Brazil Splitting Method

In order to study the energy dissipation of saturated coal sample during tensile failure process, Brazil disk splitting experiment was carried out for coal sample collected from ZhaoGu No.2-1 mine and in natural and saturated state respectively, based on RMT-150B rock mechanics experimental system, the variation of stress, strength and energy was explored under saturated state. Experimental results indicate that during Brazil splitting experiment, the stress-time relation in loading process is related to experimental control mode. Adopting load control mode, tensile stress and time present good linear relation before peak stress; when peak value is reached, tensile stress immediately dropped to zero, which indicates that coal sample has apparent brittle failure feature. Adopting deformation control mode, tensile stress and time present nonlinear relation before peak stress; and several times failure feature appears after peak value. There is no essential difference of above two kinds of control mode before failure in Brazil disc splitting experiment. In two states, there are differences of tension strength and peak energy rate of coal samples collected from different coal seams. Under natural state condition, sample collected from lower strata has higher tensile strength (1.80MPa); those collected from middle strata has lower tension strength (1.23MPa); and those collected from upper strata has tensile strength between that of lower and middle strata (1.52MPa). After water saturation, both tensile strength and peak energy rate of samples collected from upper, middle and lower strata decrease in different degrees; the average softening coefficients of tension strength are 0.65, 0.61 and 0.61 respectively; and average peak energy rates decrease ranges are 36%, 56.1% and 40.6%, respectively. In two kinds of state, the relation between tensile strength and peak energy rate is approximately linear. The higher the tensile strength of coal sample is, the less energy dissipation, the lower the tensile strength of coal samples is, the more energy dissipation.