钢筋混凝土烟囱爆破拆除的下坐及早期断裂预测

孙金山; 谢先启; 贾永胜; 姚颖康; 刘昌邦; 韩传伟; 王洪刚; 黄小武

doi:10.11883/bzycj-2021-0316

钢筋混凝土烟囱爆破拆除的下坐及早期断裂预测

doi: 10.11883/bzycj-2021-0316

孙金山^{1, 2,},
谢先启^{1, 2},
贾永胜^{1, 2},
姚颖康^{1, 2},
刘昌邦³,
韩传伟³,
王洪刚³,
黄小武³

1.
江汉大学精细爆破国家重点实验室，湖北武汉 430056
2.
江汉大学爆破工程湖北省重点实验室，湖北武汉 430056
3.
武汉爆破有限公司，湖北武汉 430056

基金项目: 湖北省自然科学基金（2020CFA043）；湖北省重点研发计划（2020BCA084）；江汉大学科技创新专项

详细信息

作者简介:
孙金山（1980－　），男，博士，教授，sun99001@126.com

中图分类号: O389; TU746.5
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- 被引次数: 0
出版历程
- 收稿日期: 2021-07-27
- 修回日期: 2022-04-25
- 网络出版日期: 2022-05-12
- 刊出日期: 2022-09-09

Prediction of sinking down and early break in the air of reinforced concrete chimney during blasting demolition

1.
State Key Laboratory of Precision Blasting Engineering, Jianghan University, Wuhan 430056, Hubei, China
2.
Hubei Key Laboratory of Blasting Engineering, Jianghan University, Wuhan 430056, Hubei, China
3.
Wuhan Explosions & Blasting Co. Ltd., Wuhan 430056, Hubei, China

摘要

摘要: 为分析钢筋混凝土烟囱在爆破拆除时发生下坐与空中断裂现象的机制并对其进行预测，对一高180 m烟囱的下坐和空中断裂过程进行了观测和分析。基于混凝土的压缩全应力-应变曲线特征，分析了烟囱支撑区的破坏过程，构建了烟囱失稳下坐的判别模型。通过建立烟囱下坐冲击作用下爆破切口以上烟囱的动力响应模型，分析了下坐冲击附加动应变波在烟囱中的传播特征。研究结果表明，考虑混凝土全应力-应变曲线特征和支撑区横截面应力和应变分布特征时，倾覆力矩与抵抗力矩的比值f可作为失稳下坐的判别条件之一；烟囱发生下坐的必要条件是支撑区最小残余承载力小于烟囱的重量。烟囱在下坐结束阶段，获得一定初速度的烟囱冲击基础时将产生冲击荷载，并在烟囱中部引起大于底端应变的应变，即产生动应变高程放大效应，该效应是导致烟囱发生早期断裂的主要原因。烟囱越高，下坐冲击历时越短，动应变高程放大效应越显著，发生断裂的风险也越大。随着烟囱高度的增加，烟囱最危险截面的位置也越高：由烟囱中下部移至烟囱中上部。
- 钢筋混凝土烟囱 /
- 爆破拆除 /
- 空中断裂 /
- 下坐 /
- 预测模型
Abstract: The collapse of the support part and break in the air of the reinforced concrete chimney during blasting demolition seriously affect engineering safety. Monitoring and analysis of a 180m chimney demolition were carried out to analyze the mechanism of these phenomena and distinguish them. Based on the characteristics of the stress-strain curve of concrete, the progressive failure process of the support part is analyzed. The static equilibrium equation of the cross-section is constructed, and the discrimination model for the instability and support part collapse of the chimney is proposed. By establishing the dynamic response model of the chimney above the blasting notch under the bottom impact, the propagation characteristics of the stress wave in the chimney are analyzed. The results show that the ratio of gravity moment to resisting moment can be used as a criterion of instability determination, considering the distribution characteristics of stress and strain in the cross-section of the support part. The compression failure of the concrete in the support part is almost inevitable under large eccentric compression. The necessary condition to prevent support part collapse of the chimney is that the minimum residual bearing capacity of the support part is not less than the weight of the chimney. When the chimney with a certain initial velocity impacts the foundation at the end of the support part collapse, an impact load will be generated and cause the strain in the middle of the chimney greater than the strain at the bottom. The elevation amplification effect of dynamic strain is an important reason for the chimney breaking in the air. The higher the chimney is, the shorter the impact duration is, and the more significant the dynamic strain elevation amplification effect is. As the height increases, the position of the most dangerous section of the chimney will move from the middle and lower to the middle and upper.
- reinforced concrete chimney /
- blasting demolition /
- breaking in the air /
- sinking down /
- prediction model

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图 1 萧山热电厂180 m高烟囱

Figure 1. The 180-m-high chimneyof Xiaoshan thermal power plant

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图 2 成都热电厂210 m高烟囱

Figure 2. The 210-m-high chimneyof Chengdu thermal power plant

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图 3 爆破方案

Figure 3. Blasting plan of the chimney

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图 4 烟囱支撑区裂纹扩展过程

Figure 4. Crack propagation process in the support part

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图 5 烟囱下坐位移时程曲线

Figure 5. Displacement-time history curve of chimney sinking down

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图 6 烟囱下坐速度时程曲线

Figure 6. Velocity-time history curve of chimney sinking down

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图 7 烟囱下坐加速度时程曲线

Figure 7. Acceleration-time history curve of chimney sinking down

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图 8 烟囱空中折断过程

Figure 8. Breaking in the air of the chimney

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图 9 混凝土典型应力-应变曲线

Figure 9. Typical full strain-stress curve of concrete

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图 10 支撑区不同区域混凝土的应力与应变状态示意图

Figure 10. Schematic of the stress and strain status of the concrete in the support part

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图 11 不受应力集中效应影响的烟道口以上烟囱的微元体模型

Figure 11. Microelement model of the chimney above the flue without stress concentration effect

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图 12 切口圆心角 $\omega$ 与支撑区受压占支撑区比例ζ的关系

Figure 12. Relationship between the blasting notch’s central angle and the compressive region ratio

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图 13 切口圆心角 $\omega$ 与烟囱倾覆失稳系数f的关系

Figure 13. Relationship between the blasting notch’s central angle and the instability coefficient

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图 14 减速过程对轴向应变放大系数ξ的影响

Figure 14. Distribution of amplification factor of longitudinal strain in deceleration process

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表 1 烟囱主要结构尺寸

Table 1. Structure parameters of the chimney

高程/m	筒壁外半径/cm	筒壁内半径/cm	筒壁厚度/cm	隔热层厚度/cm	内衬厚度/cm
0	812	757	55	0	0
7.25	776	721	55	10	23
20.00	712	662	50	10	23
30.00	662	617	45	10	23
45.00	617	575	42	10	12
60.00	572	533	39	10	12
75.00	527	491	36	10	12
90.00	482	449	33	10	12
105.00	460	430	30	10	12
120.00	437	410	27	10	12
135.00	415	391	24	10	12
150.00	392	370	20	10	12
165.00	392	372	20	10	12
180.00	392	372	20	10	12

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表 2 不同高度烟囱的最大动应变放大系数

Table 2. Maximum amplification factor of peak dynamic strain of chimneys with different heights

烟囱	高度/m	烟囱截面面积随高度变化函数	ξ	最大动应变所处高度/m
1	90	A = 7.46e^−0.017x	1.093	30
2	120	A = 10.34e^−0.014x	1.241	50
3	150	A = 20.70e^−0.012x	1.383	80
4^*	180	A = 22.35e^−0.011x	1.522	110
5	210	A = 32.05e^−0.011x	1.728	140
注: 表中180 m烟囱为一般的等截面烟囱，与第2节案例烟囱形状存在一定差异。

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