自由边界影响下定向断裂爆破裂纹尖端应力分布与扩展机理

邱鹏; 岳中文

doi:10.11858/gywlxb.20240799

自由边界影响下定向断裂爆破裂纹尖端应力分布与扩展机理

doi: 10.11858/gywlxb.20240799

邱鹏^1,,
岳中文^2,*, ,

1.
太原理工大学原位改性采矿教育部重点实验室, 山西太原　030024
2.
中国矿业大学（北京）力学与土木工程学院, 北京　100083

基金项目: 国家自然科学基金（52204106，52174094）；国家重点研发计划（2021YFC2902103）；山西省基础研究面上项目（202203021211133）

详细信息

作者简介:
邱　鹏（1991－），男，博士，助理研究员，主要从事煤岩爆破断裂研究. E-mail：qiupeng@tyut.edu.cn

通讯作者:
岳中文（1975－），男，博士，教授，主要从事岩土工程、爆破工程、采矿工程研究. E-mail：zwyue75@163.com

中图分类号: O389; O521.9
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出版历程
- 收稿日期: 2024-04-22
- 修回日期: 2024-05-15
- 网络出版日期: 2024-08-29
- 刊出日期: 2024-09-29

Stress Distribution and Propagation Mechanism of Crack Tip in Directional Fracturing Blasting under the Influence of Free Boundary

QIU Peng^1
,,
YUE Zhongwen^{2,*
, ,}

1.
Key Laboratory of In-Situ Property-Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China
2.
School of Mechanics and Civil Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China

摘要

摘要: 天然岩体常含自由边界，对定向断裂爆破产生干扰。为探究自由边界对定向断裂爆破的影响，采用爆炸焦散线方法和高速摄影技术，研究了含自由边界时定向爆炸裂纹尖端的应力分布和扩展机理。自由边界的反射P/S波作用于定向爆炸裂纹，改变了裂尖应力分布，产生了“弧线形”裂纹扩展路径。定向爆炸裂纹扩展可分为3个阶段。(1) 反射波作用前：裂尖受爆生气体“气楔”作用，产生Ⅰ型断裂，并沿直线扩展。(2) 反射波作用时：反射P/S波均使裂尖受张拉-剪切作用，产生Ⅰ-Ⅱ复合型断裂，裂纹偏转趋向自由边界；在反射P波的作用下裂尖产生畸变焦散斑，裂尖应力由K场主导变为非K场主导，而在反射S波的作用下裂尖应力恢复为K场主导。(3) 反射波作用后：裂尖在惯性作用下恢复为Ⅰ型断裂，沿直线扩展。在明确反射P/S波对定向爆炸裂纹作用的基础上，推导了自由边界影响下定向断裂爆破炮孔间距的计算公式，可为精细化定向断裂爆破提供理论参考。
- 自由边界 /
- 定向断裂爆破 /
- 反射P/S波 /
- 裂尖应力分布 /
- 裂纹扩展
Abstract: Natural rock masses often contain free boundaries, which can interfere with directional fracturing blasting. To investigate effects of free boundary on directional fracturing blasting, the caustics method and high-speed photography were used to study the crack-tip stress distribution and propagation of directional blast-induced cracks. The reflected P/S waves from the free boundary act on a directional blast-induced crack, and change the crack-tip stress distribution and generate an “arc shaped” crack path. Directional blast-induced crack propagation can be divided into three stages. Stage one: before the action of reflected waves, the crack tip is subjected to the action of a blast-induced gas wedge, resulting in a mode Ⅰ crack that propagates along a straight line. Stage two: under the action of reflected waves, both reflected P and S waves cause the crack tip to be subjected to tension and shear action, resulting in a mixed mode Ⅰ-Ⅱ crack which deflects towards the free boundary. Under reflected P waves, the crack tip produces distorted caustics, and crack-tip stress changes from K-dominated field to non-K-dominated field, while under reflected S waves, crack-tip stress returns to K-dominated field. Stage three: after the action of reflected waves, the crack tip is subjected to inertial action and then returns to a mode Ⅰ crack which propagates along a straight line. On the basis of clarifying effects of reflected P/S waves on the tip of directional blast-induced cracks, a calculation formula for the distance between two directional fracturing blasting holes under the influence of free boundary is derived, providing a theoretical basis for refined directional fracturing blasting.
- free boundary /
- directional fracturing blasting /
- reflected P/S waves /
- crack-tip stress distribution /
- crack propagation

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图 1 试件的示意图：(a) 试件尺寸，(b) 切缝药包

Figure 1. Schematic diagram of the specimen: (a) size of the specimen; (b) slotted cartridge

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图 2 爆炸焦散线实验系统

Figure 2. Blasting caustics experimental setup

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图 3 经典的焦散斑方法测量应力强度因子：(a) Ⅰ型焦散斑，(b) Ⅰ-Ⅱ复合型焦散斑，(c) 焦散斑尺寸比例，(d) δ_T和δ_Lmax

Figure 3. Classical stress intensity factor measurement by caustics patterns: (a) mode Ⅰ caustics pattern; (b) mixed Ⅰ-Ⅱ mode caustics pattern; (c) ratio of caustics pattern size; (d) δ_T and δ_Lmax

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图 4 爆炸后裂纹路径：(a) 爆后试件S1，(b) 爆后试件S2，(c) 4条定向爆炸裂纹路径

Figure 4. Crack path after blasting: (a) specimen S1 after blasting; (a) specimen S2 after blasting;(c) paths of four directional blast-induced cracks

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图 5 反射波作用前：(a) 爆炸焦散斑图像，(b) t=30 μs时C1裂纹尖端“圆形”焦散斑，(c) t=40 μs时C1裂纹尖端“椭圆形”焦散斑

Figure 5. Before action of reflected waves: (a) blast-induced caustics patterns; (b) circle caustics pattern at the tip of crack C1 at 30 μs; (c) ellipse caustics pattern at the tip of crack C1 at 40 μs

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图 6 反射P波作用时：(a) 爆炸焦散斑图像，(b) t=50 μs时C1裂纹尖端的“椭圆形”焦散斑，(c) t=60 μs时C2裂纹尖端的Ⅰ-Ⅱ复合型焦散斑

Figure 6. Under action of reflected P wave: (a) blast-induced caustics patterns; (b) ellipse caustics pattern at the tip of crack C1 at 50 μs; (c) mixed Ⅰ-Ⅱ mode caustics pattern at the tip of crack C2 at 60 μs

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图 7 反射S波作用时：(a) 爆炸焦散斑图像，(b) t=70 μs 时C1裂纹尖端的Ⅰ-Ⅱ复合型焦散斑，(c) t=70 μs时C2裂纹尖端的Ⅰ-Ⅱ复合型焦散斑

Figure 7. Under action of reflected S wave: (a) blast-induced caustics patterns; (b) mixed Ⅰ-Ⅱ mode caustics pattern at the tip of crack C1 at 70 μs; (c) mixed Ⅰ-Ⅱ mode caustics pattern at the tip of crack C2 at 70 μs

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图 8 反射波作用后：(a) 爆炸焦散斑图像，(b) t=110 μs 时C1裂纹尖端Ⅰ型焦散斑，(c) t=120 μs 时C1裂纹尖端的Ⅰ型焦散斑

Figure 8. After action of reflected waves: (a) blast-induced caustics patterns; (b) mode Ⅰ caustics pattern at the tip of crack C1 at 110 μs; (c) mode Ⅰ caustics pattern at the tip of crack C1 at 120 μs

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图 9 定向爆炸裂纹尖端应力强度因子：(a) Ⅰ型应力强度因子K_Ⅰ，(b) Ⅱ型应力强度因子K_Ⅱ（RP和RS分别代表反射P波和反射S波）

Figure 9. Stress intensity factors of directional blast-induced cracks: (a) mode Ⅰ stress intensity factor K_Ⅰ; (b) mode Ⅱ stress intensity factor K_Ⅱ (RP and RS represent reflected P and S waves, respectively.)

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图 10 定向爆炸裂纹扩展结果：(a) 裂纹扩展速度，(b) 裂纹扩展速度与K_Ⅰ的正相关性

Figure 10. Results of directional blast-induced crack propagation : (a) crack propagation velocity; (b) positive correlation between crack propagation velocity and K_Ⅰ

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图 11 定向断裂爆破炮孔间距计算示意图

Figure 11. Schematic diagram of borehole spacing calculation for directional fracturing blasting

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