加载角度对层理页岩裂纹扩展影响的实验研究

杨国梁; 毕京九; 郭伟民; 张志飞; 韩子默; 程帅杰

doi:10.11883/bzycj-2021-0097

加载角度对层理页岩裂纹扩展影响的实验研究

doi: 10.11883/bzycj-2021-0097

杨国梁^1,,
毕京九^1, ,,
郭伟民¹,
张志飞¹,
韩子默¹,
程帅杰^{1, 2}

1.
中国矿业大学(北京)力学与建筑工程学院，北京 100083
2.
中信建设有限责任公司，北京 100027

基金项目: 国家自然科学基金重点项目（51934001）

详细信息

作者简介:
杨国梁（1979－　），男，博士，副教授，yanggl531@163.com

通讯作者:
毕京九（1995－　），男，博士研究生，bijingjiu@126.com

中图分类号: O346; TU452
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- 文章访问数: 643
- HTML全文浏览量: 287
- PDF下载量: 89
- 被引次数: 0
出版历程
- 收稿日期: 2021-03-22
- 修回日期: 2021-05-06
- 网络出版日期: 2021-08-16
- 刊出日期: 2021-09-14

Experimental study on the effect of loading angle on crack propagation in bedding shale

1.
School of Mechanics and Architectural Engineering, China University of Mining and Technology, Beijing 100083, China
2.
CITIC Construction Co., Ltd., Beijing 100027, China

摘要

摘要: 采用分离式霍普金森压杆（SHPB）系统对页岩进行冲击实验，研究层理角度对页岩动态断裂过程的影响，在裂尖设置裂纹扩展计，借助高速摄影和数字图像相关（DIC）技术对页岩中心切槽半圆盘弯曲（NSCB）试件断裂的全过程进行研究，得到了不同加载角度下页岩的动态起裂韧度、裂纹扩展速度、断裂过程中应变场和水平位移场的变化规律。实验发现：不同加载角度下，页岩的动态起裂韧度具有显著的各向异性，加载角度与动态起裂韧度呈正相关；加载角度对试样的裂纹扩展速度具有显著影响，与裂纹扩展速度呈负相关；当冲击速度较低时，切槽方向是裂纹扩展的优势方向，而当冲击速度较高时，试样会产生沿层理弱面的次生裂纹，次生裂纹对试样的断裂具有显著影响。
- 页岩 /
- 层理 /
- 中心切槽半圆盘弯曲试件 /
- 动态断裂韧度 /
- 数字图像相关技术 /
- 分离式霍普金森压杆
Abstract: The dynamic fracture of rock materials is a basic problem in the field of rock mechanics, while the dynamic fracture mechanism of shale is more complex due to its anisotropic characteristics. In order to study the effect of bedding angle on dynamic fracture process of shale, a split Hopkinson pressure bar (SHPB) system was used to carry out impact tests on notched semi-circular bend (NSCB) specimens of shale. Additionally, a crack propagation gauge (CPG) was set at the crack tip, and the whole fracture process of the shale NSCB specimen was studied with the help of a high-speed photography system and the digital image correlation (DIC) method. The loading rate and Mode-I dynamic fracture toughness of the shale NSCB samples were obtained by the method recommended by the International Society for Rock Mechanics (ISRM). And the crack initiation time and crack propagation speed of the shale NSCB samples can be accurately obtained by CPG. It is found from the experimental results that the Mode-I dynamic fracture toughness of the shale NSCB samples has significant anisotropy, and the loading angle has a positive correlation with the Mode-I dynamic fracture toughness. Although the crack propagation of the C-0sample is not affected by the bedding, its crack propagation needs to cut through the shale matrix, hence the C-0 and 90° shale specimens have a high Mode-I dynamic fracture toughness. When the impact velocity is low, the bending stress on the dangerous section affects the fracture direction of the shale specimen, but with less effect on the bedding. The crack propagation path finally closes to the notch direction. With the increase of impact velocity, stress concentration and micro cracks may exist along the weak plane of bedding due to its relatively low strength. With the increase of impact velocity, the cracks between the weak planes of bedding begin to extend, and the failure planes along the direction of bedding and notch occurred simultaneously.
- shale /
- bedding /
- notched semi-circular bend (NSCB) specimen /
- dynamic fracture toughness /
- digital image correlation method /
- split Hopkinson pressure bar

HTML全文

图 1 NSCB试件构型

Figure 1. Schematic diagram of NSCB

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图 2 页岩NSCB试件加载角示意图

Figure 2. Loading angle of the shale NSCB specimens

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图 3 实验所用页岩NSCB试件

Figure 3. Shale NSCB specimens

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图 4 SHPB实验布置

Figure 4. Layout of the SHPB experiments

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图 5 力平衡的验证

Figure 5. Verification of the force balance

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图 6 加载率的确定

Figure 6. Determination of the loading rate

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图 7 典型加载波形时程曲线

Figure 7. Time history curve of a typical loading waveform

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图 8 典型裂纹扩展计电压时程曲线

Figure 8. Voltage time history curve of a typical crack growth meter

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图 9 加载率与动态起裂韧度关系曲线

Figure 9. Relationship between the loading rate and the dynamic fracture toughness

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图 10 裂纹扩展位置示意图

Figure 10. Schematic diagram of the crack propagation position

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图 11 不同加载率下C-0试件裂纹扩展速度变化

Figure 11. Crack propagation speed of the C-0 specimens under different loading rates

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图 12 等冲击速度下不同加载角试件的裂纹扩展速度

Figure 12. Crack propagation speed of specimens with different loading angles under constant impact velocity

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图 13 典型页岩NSCB试件动态断裂过程

Figure 13. Dynamic fracture process of a typical shale NSCB specimen

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图 14 DIC数据处理过程中的裂尖坐标轴及目标子区域

Figure 14. Crack tip coordinate axises and target subregion during DIC data processing

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图 15 C-0试件典型位移场和应变场变化规律

Figure 15. Typical displacement field and strain field of the C-0 specimens

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图 16 60°试件典型位移场和应变场变化规律

Figure 16. Typical displacement field and strain field of the specimens with loading angle of 60°

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图 17 不同冲击速度下页岩试样的典型破坏形态

Figure 17. Typical failure modes of shale NSCB specimens under different impact speeds

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图 18 试件沿层理面断裂

Figure 18. Specimen fractures along the bedding plane

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图 19 断裂过程

Figure 19. Fracture process

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表 1 页岩基本力学性质

Table 1. Mechanical properties of shale

层理方向	单轴抗压强度/MPa	密度/（g·cm⁻³）	弹性模量/GPa	泊松比	纵波波速/（m·s⁻¹）
平行层理	97.34	2.43	17.62	0.29	4 217
垂直层理	108.21	2.46	26.34	0.32	4 592

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表 2 页岩动态起裂韧度

Table 2. Dynamic initiation toughness of shale

加载角度	冲击速度/（m·s⁻¹）	起裂时刻/μs	加载力峰值对应时刻/μs	加载率/（GPa·m^1/2·s⁻¹）	动态起裂韧度/（MPa·m^1/2）	裂纹扩展速度/（m·s⁻¹）
C-0	3	551.3	493.8	89.335	3.83	278.49
	4	538.1	527.9	179.391	5.85	296.43
	5	551.5	525.3	348.482	8.28	382.26
0°	3	554.7	524.6	108.322	2.45	335.30
	4	571.8	538.3	309.285	7.14	383.71
	5	524.9	518.4	474.167	9.23	445.16
30°	3	570.3	547.2	119.442	4.23	312.21
	4	519.2	489.6	235.974	6.28	392.52
	5	563.4	523.4	392.154	8.04	415.17
60°	3	554.9	535.2	122.36	4.02	264.50
	4	577.4	521.7	269.242	7.03	350.02
	5	576.1	549.3	430.563	9.07	382.35
90°	3	578.8	554.3	160.947	5.13	225.66
	4	533.2	507.6	323.626	8.62	331.74
	5	569.4	513.8	463.592	10.44	367.53

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表 3 页岩NSCB试样的典型破坏路径

Table 3. Typical failure pathes of shale NSCB samples

冲击速度/（m·s⁻¹）	加载角度
冲击速度/（m·s⁻¹）	C-0	0°	30°	60°	90°
3
4
5

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