不同加载速率下砂岩弯曲破坏的细观机理

李柯萱; 李铁

doi:10.11883/bzycj-2018-0178

不同加载速率下砂岩弯曲破坏的细观机理

doi: 10.11883/bzycj-2018-0178

李柯萱^{1, 2,},
李铁^{1, 2, ,}

1.
北京科技大学金属矿山高效开采与安全教育部重点实验室，北京 100083
2.
北京科技大学土木与资源工程学院，北京 100083

基金项目: 国家自然科学基金（51674016，51274025，51534002）

详细信息

作者简介:
李柯萱（1987－　），女，博士研究生, likexuan_456@163.com

通讯作者:
李　铁（1956－　），男，博士，教授，litie@ustb.edu.cn

中图分类号: O348.3; TU454
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- 被引次数: 0
出版历程
- 收稿日期: 2018-05-25
- 修回日期: 2018-08-27
- 刊出日期: 2019-04-01

Micro-mechanism of bending failure of sandstone under different loading rates

LI Kexuan^{1, 2
,},
LI Tie^{1, 2
, ,}

1.
State Key Laboratory of High-efficiency Mining and Safety of Metal Mines, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China
2.
School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China

摘要

摘要: 岩石细观破裂形貌是岩石破坏机制的重要反映，为研究不同加载速率对砂岩弯曲破坏的影响，通过三点弯曲实验和扫描电镜方法，对某煤矿关键层砂岩弯曲破断裂纹细观形态以及裂纹的自相似性进行了研究。选取6个不同加载速率对岩样进行三点弯曲实验，观察其宏观断裂情况，并利用扫描电镜对弯曲断裂面表面裂纹细观结构进行观察，并拍摄不同倍数下的扫描电镜图片。对图片进行图像处理后得到砂岩弯曲断裂破坏细观裂纹信息，并计算得到微裂纹的分形盒维数值。结果显示：随着加载速率的提高，砂岩穿晶断裂的比例也随之升高，裂纹分形维数亦随着加载速率的增大而增加，同时，分形维数还与弯曲断裂破坏荷载和抗弯强度成正比。可见，加载速率对断裂方式有一定的影响，且加载速率越大断裂所需的破坏能越大，裂纹分布越广，表明开采速度与岩爆等岩体动力灾变有密切关系。
- 三点弯曲 /
- 加载速率 /
- 岩石断口 /
- 细观形貌 /
- 分形维数
Abstract: The micro morphology of rock rupture is an important reflection of rock failure mechanism, in order to study the effect of different loading rates on the bending failure of sandstone, the microscopic morphology of the bending breaking cracks and the self-similarity of the cracks are analysed by scanning electron microscope combined with three point bending test. Selecting six different loading rates to test the rock samples to observe the macroscopic fracture condition and then the microstructure of surface cracks on bend fracture surfaces is observed by scanning electron microscope, and take SEM pictures at different multiplier. After the image is processed, getting the micro crack information of bending fracture of sandstone, and the fractal box dimension value of the micro crack is calculated. The results show that the proportion of transgranular fracture increases with the increase of loading rate; the crack fractal dimension also increases with the increase of loading rate, and at the same time, the fractal dimension is proportional to the bending fracture load and bending strength. It can be seen that the loading rate has a certain effect on the fracture mode, and the greater the loading rate is, the greater the failure energy requires, and the wider the crack distribution is, indicating that mining speed is closely related to rock burst and other dynamic catastrophe of rock mass.
- three point bending /
- loading rate /
- rock fracture /
- micromorphology /
- fractal dimension

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图 1 破坏荷载的加载速率效应

Figure 1. Loading rate effect of failure load

下载: 全尺寸图片幻灯片

图 2 0.1、10和60 N/s加载速率下样品破坏照片

Figure 2. Specimen destruction under loading rates of 0.1, 10 and 60 N/s

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图 3 不同加载速率下样品的SEM图像

Figure 3. SEM images of samples at different loading rates

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图 4 SEM图像裂纹图像提取过程

Figure 4. Crack image extraction process of SEM photos

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图 5 分形盒维数法计算

Figure 5. Fractal dimension calculation in box counting

下载: 全尺寸图片幻灯片

图 6 加载速率和分形维数之间的关系

Figure 6. Relationship between fractal dimension and loading rate

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图 7 破坏荷载(P_t)、抗弯强度(R_t)与分形维数(D_s)的关系

Figure 7. Variation of failure load (P_t) and bending strength (R_t) with fractal dimension (D_s)

下载: 全尺寸图片幻灯片

表 1 岩石三点弯曲实验力学参数

Table 1. Mechanical parameters of rock three-point bending testing

加载速率/(N·s⁻¹)	编号	破坏荷载/kN	抗弯强度/MPa	加载速率/(N·s⁻¹)	编号	破坏荷载/kN	抗弯强度/MPa
0.1	A1	2.5		10	D1	2.86
	A2	2.61			D2	2.51
	A3	2.57			D3	2.94
	平均	2.56	6.144		D4	3.00
0.4	B1	2.58			平均	2.93	7.032
	B2	2.72		30	E1	3.34
	B3	2.68			E2	3.25
	平均	2.66	6.384		E3	3.47
1	C1	2.8			平均	3.35	8.040
	C2	2.99		60	F1	3.64
	C3	2.83			F2	3.48
	C4	2.71			F3	3.63
	平均	2.78	6.648		平均	3.56	8.544

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表 2 砂岩试件裂纹分形维数

Table 2. Fractal dimension of cracks of sandstone

加载速率/(N·s⁻¹)	拟合公式	分形维数	加载速率/(N·s⁻¹)	拟合公式	分形维数
0.1	log₂N=−1.670 1 log₂a+2.696 6	1.670 1	10	log₂N=−1.717 7 log₂a+3.177 6	1.717 7
	log₂N=−1.665 3 log₂a+3.002 6	1.665 3		log₂N=−1.699 9 log₂a+2.316 7	1.699 9
	log₂N=−1.699 2 log₂a+2.737 6	1.699 2		log₂N=−1.705 5 log₂a+2.981 5	1.705 5
平均		1.678 2	平均		1.707 7
0.4	log₂N=−1.671 6 log₂a+3.257 5	1.671 6	30	log₂N=−1.736 6 log₂a+3.097 9	1.736 6
	log₂N=−1.683 5 log₂a+2.798 7	1.683 5		log₂N=−1.725 8 log₂a+3.011 8	1.725 8
	log₂N=−1.692 7 log₂a+3.127 6	1.692 7		log₂N=−1.742 6 log₂a+3.328 6	1. 742 6
平均		1.682 6	平均		1.735
1	log₂N=−1.698 7 log₂a+3.315 7	1.698 7	60	log₂N=−1.762 9 log₂a+2.923 0	1.762 9
	log₂N=−1.696 8 log₂a+3.255 3	1.696 8		log₂N=−1.749 8 log₂a+3.257 4	1.749 8
	log₂N=−1.703 6 log₂a+2.446 0	1. 703 6		log₂N=−1.764 6 log₂a+2.986 6	1.764 6
平均		1.699 7	平均		1.759 1

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