局部静载约束条件下动力扰动对煤岩损伤的影响

Influence of dynamic disturbance on coal-rock damage under local static load constraints

摘要:

为得到局部静载约束条件下循环冲击荷载对煤岩损伤的影响特征,基于自行研制的约束式摆锤冲击动力加载装置研究局部静载约束条件下原煤试样分别受到恒定冲量循环冲击和递增冲量循环冲击过程中损伤因子和表面裂纹的演化规律。结果表明:当约束区处于弹性状态时,约束面积越大的分区抗冲击能力越强,当约束区处于塑性状态时,约束面积越大的分区抗冲击能力越差；递增冲量循环冲击对煤岩的致损效率高于恒定冲量循环冲击,两种冲击方式破岩效率的差异主要体现在静载约束区,并且静载值越大,损伤因子对冲击方式的敏感度越高；煤岩表面的裂纹扩展与损伤因子的分区特征较为一致,当约束区处于弹性状态时,静载约束对裂纹的扩展起到抑制作用,裂纹主要沿着约束面积较小的区域扩展、衍生；当约束区处于塑性状态时,裂纹主要在约束面积较大的区域扩展,并且约束区内主要以竖直方向的拉伸裂纹为主,而非约束区内的裂纹主要沿倾斜方向扩展；随着静载值增加,试样表面裂纹的分形维数先减小后增加。局部静载约束可以提高煤岩抗冲击能力,并且煤岩损伤演化呈明显的分区特征。

Abstract:

To obtain the influence characteristics of cyclic impact loading on coal-rock damage under local static load constraints, we studied the damage factors and crack evolution of coal-rock samples during constant impulse cyclic impact and incremental impulse cyclic impact under local static load constraints by using the self-developed constrained pendulum-impact dynamic loading device. Experimental results show that when the constrained zone was in an elastic state, the partition with larger static load restraint area had stronger impact resistance; when the constrained zone was in a plastic state, the partition with larger static load restraint area had weaker impact resistance. The incremental impulse cyclic impact had higher damage efficiency to coal-rock than the constant impulse cyclic impact. The difference in rock breaking efficiency between the two cyclic impact methods was mainly reflected in the static load constrained zone, and the greater the static load value was, the higher the sensitivity of the damage factor to the impact method was. The crack propagation on the coal-rock surface was consistent with the zoning characteristics of the damage factor. When the static load constrained zone was in an elastic state, the static load had an inhibitory effect on the crack growth, and the cracks mainly expanded and derived along the partitions that were less constrained. When the static load constrained zone was in a plastic state, the cracks mainly propagated in the partitions that were more constrained, and tensile cracks in vertical direction were dominant in the constrained zone, while the cracks in the non-constrained zone mostly grew in an oblique direction. As the static load value increased, the fractal dimension of the surface cracks on the sample decreased first and then increased. The local static load constraints improved the impact resistance of coal-rock, and the damage factor of coal-rock showed obvious zoning characteristics.