Influence of wind load acted on tall chimney in directional blasting
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摘要: 从高烟囱余留支撑体截面的中性轴方程出发，推导顺风荷载与横风共振共同作用下，高烟囱定向爆破倾倒偏转角的修正公式，研究不同风级（4~6级）、不同切口角（190°~220°）、不同风向角（0°~180°）对爆破倾倒偏转角的影响规律，并对最大偏转角的绝对值和产生条件进行讨论，最后以南昌电厂210m高烟囱的爆破参数设计和触地防护过程为例进行验证。计算表明，对于高耸烟囱，考虑横风共振后倾倒偏转角显著增大，是顺风引起偏转角的4~5倍；风级一定的条件下，存在最不利风向角，致使烟囱产生最大偏转角；最大倾倒偏转角随着风力等级的增大而增大，随着切口角的增大而减小。Abstract: The deflection angle formula was derived based on the neutral axis equation with the tall chimney blasting cut section under the action of both along-wind load and across-wind resonance.Then a series of wind load cases were considered as follows:different wind Beaufort scales (grade 4-grade 6), different blasting incision angles (190°-220°) and different wind load directions (0°-180°).Their influences were achieved on the directional blasting demolition.In addition, the maximum deflection angle of the tall chimney and its existence condition were discussed.The corresponding conclusion was verified by taking the 210 mhigh chimney in Nanchang power plant as an example.The results showed that the deflection angle considering the across-wind resonance was 4-6 times as big as that considering the along-wind load.Furthermore, there existed the most unfavorable wind direction angle which would cause the maximum deflection angle under certain conditions.The maximum deflection angle would increase with the increasing wind Beaufort scale and would decrease with the decreasing blasting incision angle.
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Key words:
- mechanics of explosion /
- across-wind resonance /
- deflection angle /
- directional blasting /
- wind load /
- tall chimney
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图 2 不同切口角条件下偏转角变化曲线
Figure 2. Variation of the deflection angle with different blasting incision angles
图 3 最大偏转角随风向角的变化曲线
Figure 3. Variation of the maximum deflection angle with wind direction angle
表 1 不同切口角条件下对应的偏转角和位移偏差
Table 1. Variation of the deflection angle and displacement with different blasting incision angles
风级 θ1/(°) θ2/(°) (θ2-θ1)/(°) Δ/m 最小值 最大值 最小值 最大值 最小值 最大值 最小值 最大值 4 0.45 0.64 2.65 3.80 2.20 3.16 8.06 11.58 5 0.94 1.35 4.94 7.08 4.00 5.73 14.65 20.99 6 1.59 2.30 9.93 14.08 8.34 11.78 30.55 43.15 
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表 2 不同切口角条件下最大偏转角和风向角变化规律
Table 2. Variation of maximum deflection angle and wind direction angle with different blasting incision angles
α/(°) θ2, max/(°) β2/(°) θ2, max/(°) β2/(°) θ2, max/(°) β2/(°) 4级 5级 6级 190 3.91 16.69 7.27 16.90 15.12 7.77 195 3.64 16.75 6.77 17.00 14.12 7.99 200 3.40 16.80 6.34 17.10 13.22 8.19 205 3.19 16.85 5.95 17.19 12.43 8.39 210 3.01 16.89 5.60 17.27 11.73 8.56 215 2.85 16.93 5.31 17.35 11.12 8.73 220 2.72 16.97 5.06 17.42 10.60 8.89
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