结构异性煤体单轴/三轴冲击动力学性能研究

doi:10.12034/j.issn.1009-606X.220178

摘要/Abstract

摘要：

井下深孔爆破致裂是提高低渗煤层渗透率的重要措施之一，但由于煤层层理因素影响，在不同方向上的爆破致裂效果存在显著差异。采用分离式霍布金森压杆实验装置，对从垂直于层理方向和平行于层理方向进行取芯的煤样，分别进行冲击荷载为0.1, 0.15, 0.2, 0.3, 0.5 MPa的单/三轴SHPB冲击实验，分析结构异性煤体的冲击动力学性能。结果表明，煤样在不同冲击作用下，其单、三轴应力-应变曲线趋势相同，且其峰值应力、平均应变率随冲击荷载增大而增长趋势相同，其中峰值应力与冲击荷载符合指数关系，平均应变率与冲击荷载呈线性关系，相同冲击荷载下垂直于层理方向煤样的峰值应力、平均应变率相较于平行于层理方向煤样有所提升；进行三轴SHPB冲击时，在轴、围压对煤样约束作用下，其峰值应力、平均应变率相较于单轴情况下均有所提高，且在冲击荷载为0.15~0.2 MPa时峰值应力增幅最大，增大约50%，垂直于层理方向的动力学性能改变相较于平行于层理方向更明显。

关键词: 动力学性能, 分离式霍布金森压杆, 煤样, 层理方向, 应变率

Abstract:

As a heterogeneous, anisotropic and porous porous brittle material, the coal body has a large number of micro-scales such as bedding, joints, cracks, etc. so that the blasting and cracking effects in different directions will be significantly different. Based on this, a split Hopkinson pressure bar (SHPB) experimental device was used to perform impact loads of 0.1, 0.15, 0.2, 0.3, 0.5 MPa on the coal samples taken from the vertical and parallel bedding directions. The uniaxial/triaxial SHPB impact test was used to compare the uniaxial/triaxial impact dynamics performance of the anisotropic coal body stress-strain, peak stress, average strain rate, etc. after the impact. The results showed that under the action, the uniaxial and triaxial stress-strain curves had the same trend, and the peak stress and average strain rate increased with the impact load, and the growth trend was also the same. When the uniaxial impact, the stress of the coal sample followed the strain which can reach the peak stress quickly and dropped down quickly to complete the unloading. During triaxial impact, this stage was relatively smooth and had a longer elastoplastic deformation, so its dynamic mechanical properties were also improved well. Due to the relatively weak bonding surface between coal layers, the dynamic compressive strength was relatively smaller than the dynamic compressive strength in the vertical bedding direction; the triaxial SHPB impact had the peak stress and average strain rate under the constraint of the axial and confining pressures on the coal sample compared to the uniaxial improved, and the peak stress increased the most when the impact load was 0.15~0.2 MPa, increasing by about 50%. The dynamic performance improvement in the vertical bedding direction was slightly better than that in the parallel bedding direction. The effect of pressure had certain limitations, that was a certain confining pressure had a certain limit to improve the mechanical properties of coal samples.

Key words: dynamic performance, split Hopkinson pressure bar, coal sample, bedding direction, strain rate

中图分类号:

TD315

梁为民, 刘恒, 李敏敏, 岳高伟. 结构异性煤体单轴/三轴冲击动力学性能研究[J]. 过程工程学报, 2021, 21(7): 817-826.

Weimin LIANG, Heng LIU, Minmin LI, Gaowei YUE. Study on uniaxial/triaxial impact dynamic properties of structurally heterogeneous coal[J]. The Chinese Journal of Process Engineering, 2021, 21(7): 817-826.

图/表 12

表1 煤样基本力学参数

Table 1 Basic mechanical parameters of coal samples

Direction

Compressive strength

/MPa

Tensile strength

/MPa

Density

/(g/cm³)

Internal friction angle/^o

Stiffness coefficient

Elastic modulus

/GPa

图1 实验煤样

Fig.1 Test coal samples

表2 煤样基本成分参数

Table 2 Basic composition parameters of coal samples

Industrial analysis			Maceral			Vitrinite reflectance/%
Ash/%	Volatile/%	Fixed carbon/%	Brightness group/%	Vitrinite/%	Inertinite/%	2.759
10.21	8.71	78.12	2.8	95	2.2	2.759

图2 SHPB实验装置图

Fig.2 SHPB experimental device

表3 实验煤样的测量数据

Table 3 Experimental data of coal samples

Impact pressure/MPa	Uniaxial impact				Triaxial impact
	Vertical direction		Parallel direction		Vertical direction		Parallel direction
	Coal number	Velocity/(m/s)	Coal number	Velocity/(m/s)	Coal number	Velocity/(m/s)	Coal number	Velocity/(m/s)
0.1	DC1-1	2.341	DP1-1	2.452	SC1-1	2.417	SP1-1	2.451
	DC1-2	2.367	DP1-2	2.433	SC1-2	2.254	SP1-2	2.354
	DC1-3	2.412	DP1-3	2.328	SC1-3	2.440	SP1-3	2.481
0.15	DC2-1	3.497	DP2-1	3.542	SC2-1	3.422	SP2-1	3.685
	DC2-2	3.307	DP2-2	3.478	SC2-2	3.697	SP2-2	3.338
	DC2-3	3.685	DP2-3	3.438	SC2-3	3.542	SP2-3	3.478
0.2	DC3-1	4.068	DP3-1	4.083	SC3-1	4.112	SP3-1	4.072
	DC3-2	4.023	DP3-2	4.103	SC3-2	3.878	SP3-2	3.984
	DC3-3	4.047	DP3-3	3.988	SC3-3	3.957	SP3-3	3.994
0.3	DC4-1	5.376	DP4-1	5.457	SC4-1	5.411	SP4-1	5.389
	DC4-2	5.379	DP4-2	5.398	SC4-2	5.389	SP4-2	5.428
	DC4-3	5.465	DP4-3	5.273	SC4-3	5.411	SP4-3	5.394
0.5	DC5-1	7.156	DP5-1	7.297	SC5-1	7.438	SP5-1	7.378
	DC5-2	7.556	DP5-2	7.334	SC5-2	7.274	SP5-2	7.298
	DC5-3	7.268	DP5-3	7.356	SC5-3	7.178	SP5-3	7.401

图3 空杆标定波形曲线

Fig.3 Calibration waveform curves of empty pole

图4 单/三轴冲击煤样应力-应变曲线

Fig.4 Stress-strain curves of uniaxial/triaxial impact coal samples

表4 各组均值峰值应力数据

Table 4 Mean peak stress data of each group

Impact air pressure/MPa		0.1		0.15		0.2		0.3		0.5
Direction		C	P	C	P	C	P	C	P	C	P
$σ ¯ m a x$ /MPa	Uniaxial	12.273	7.893	13.500	9.685	15.532	12.896	22.036	18.407	29.624	24.339
$σ ¯ m a x$ /MPa	Triaxial	14.462	11.206	17.426	14.649	23.668	18.514	29.569	23.782	37.840	27.518

表4 各组均值峰值应力数据

Table 4 Mean peak stress data of each group

Impact air pressure/MPa		0.1		0.15		0.2		0.3		0.5
Direction		C	P	C	P	C	P	C	P	C	P
$σ ¯ m a x$ /MPa	Uniaxial	12.273	7.893	13.500	9.685	15.532	12.896	22.036	18.407	29.624	24.339
$σ ¯ m a x$ /MPa	Triaxial	14.462	11.206	17.426	14.649	23.668	18.514	29.569	23.782	37.840	27.518

图5 单/三轴煤样冲击荷载-峰值应力关系

Fig.5 Relationship between uniaxial/triaxial coal sample impact pressure and peak stress

表5 各组均值应变率数据

Table 5 Mean strain rate data of each group

Impact air pressure/MPa		0.1		0.15		0.2		0.3		0.5
Direction		C	P	C	P	C	P	C	P	C	P
$ε ˙$ /s^-1	Uniaxial	27.024	23.671	37.874	34.311	48.550	43.797	73.483	68.522	105.706	98.274
$ε ˙$ /s^-1	Triaxial	31.832	26.869	42.634	38.427	57.198	50.387	84.306	75.973	112.466	104.716

表5 各组均值应变率数据

Table 5 Mean strain rate data of each group

Impact air pressure/MPa		0.1		0.15		0.2		0.3		0.5
Direction		C	P	C	P	C	P	C	P	C	P
$ε ˙$ /s^-1	Uniaxial	27.024	23.671	37.874	34.311	48.550	43.797	73.483	68.522	105.706	98.274
$ε ˙$ /s^-1	Triaxial	31.832	26.869	42.634	38.427	57.198	50.387	84.306	75.973	112.466	104.716

图6 单/三轴煤样冲击荷载-平均应变率关系

Fig.6 Relationship between uniaxial/triaxial coal sample impact pressure and average strain rate

图7 煤样冲击荷载与DIF的关系

Fig.7 Relationship between coal sample impact pressure and DIF

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