动静组合加载含水煤样的力学特征及细观力学分析

为分析含水煤样在动静组合加载下的力学性质，利用改进SHPB和RMT-150试验系统对义马矿区二1煤样进行动静组合加载、静载对比试验。结果表明:静载加载，煤样的应力-应变关系形态与动静组合加载应力-应变关系形态明显不同，煤样的峰值强度、弹性模量随饱水时间增加而降低，饱水3 d和7 d煤样抗压强度软化系数分别为0.66和0.52;动静组合加载，煤样动态峰值强度随饱水时间增加而降低，饱水3 d和7 d抗压强度软化系数分别为0.65和0.60，动态弹性模量却逐渐升高，提高系数分别为1.15和1.37，与饱水砂岩试验结果相比不同;动静组合加载煤样随饱水时间增加煤样破坏颗粒度逐渐减小，水对煤样动态破坏影响较显著;基于翼形裂纹受压扩展原理，推导出动静组合加载下饱水煤样动态强度计算公式;煤样动态强度比静态强度试验结果提高10%~30%，表明动静组合加载下煤样的变形、强度特征与煤样自身结构、含水状态和加载方式多重因素有关。

Micromechanics analysis and mechanical characteristics of water-saturated coal samples under coupled static-dynamic loads

Contrast experiments between static and dynamic loadings on water-saturated coal samples from Yima mining area was conducted by using the improved SHPB and the RMT-150 test systems.The effect of mechanical properties of coal samples under different loading conditions was obtained.Results show that the stress-strain relationship under static and dynamic loadings is obviously different.The peak strength and elastic modulus reduce gradually with the increase of saturation time under static loading,and the softening coefficient of compressive strength is 0.66 and 0.52 respectively for three days and seven days saturation.Meanwhile,the peak strength of coal samples under dynamic loading similarly reduces with saturation dynamic loading.And the softening coefficient of three days and seven days becomes 0.65 and 0.60,but the elastic modulus increases with the coefficients of 1.15 and 1.37 respectively,which is different from the common results of sandstone test.Water has a significant effect on the dynamic failure of coal samples,and the particle size of failure coal samples decreases with water saturation time under static and dynamic loading combination.Based on the compressive wing crack propagation mechanism,the calculation formula of water-saturated coal samples'' dynamic compressive strength was obtained in coupled static-dynamic loads.The strength of coal samples under combined dynamic loading condition was improved 10-30 percents comparing to static loading,and the increase of elastic modulus was obvious,which indicates that the deformation and strength characteristics of coal samples under middle strain rate are related to structure,water content and loading mode.