烟囱定向爆破触地冲击力估算

以烟囱定向爆破的机理为基础，结合工程实践，研究了烟囱爆破触地的过程，建立了烟囱定向爆破拆除的物理模型。确定了烟囱倾倒过程中断面的内力分析、折断位置和烟囱倾倒触地时的速度，提出了均布质量体系构成的烟囱在定向倒塌过程中的触地冲击力估算方法。结果表明，烟囱在定向爆破倾倒时在距其底部约1/3处发生折断．然后各个部分相继触地、产生振动；利用烟囱触地冲击动量来估算其冲击力所得的结果较实际偏于安全保守；触地冲击力计算与地面土层介质的力学参数、切口尺寸、烟囱的断面尺寸和材料的密度有关。该估算方法可以为实际工程中冲击力的计算和冲击防护以及定向爆破安全性评价提供理论依据。

Estimation of Impulsive Force for Chimney Toppling down to the Ground in Directed Blasting

Combining with the practical experience in engineering, the process that chimney is toppled down to the ground during directed blasting was studied based on the directed blasting theory, so a model for chimney removed by directed blasting has been established. After analyzing the internal force on the section and calculating the location of break, as well as the speed of the chimney toppling down to the ground, an evaluation method has been proposed for the impulsive force of chimney which is composed of uniform mass system, while it toppling down to the ground during the directed blasting. Results show that chimney will be broken at about 1/3 part away from its root in the directed blasting, and then each part of chimney will fall down in succession, resulting in a wave of vibration. The impulsive force estimated based on the impulsive momentum while chimney toppling down to the ground is safer and more conservative than the practical figures. It is found that the calculation value of impulsive force is related with the mechanics parameter of above layer of ground soil medium, the section size of the chimney and the density of the material. Such estimation method can be regarded as a theoretical basis for the calculation and protection of the impulsive force in practical engineering and also for the safety assessment in blasting.