预裂缝减震作用下爆破地震波的频谱特征分析

研究在微风化花岗岩石场地深孔爆破地震波通过一条长26 m,深7 m的预裂缝振动传播规律.试验数据分析表明,预裂缝的减震效果与测点与预裂缝的减震效果有关.通过对试验中5个测点处不同测点间的振动强度与比例距离的数据回归分析,预裂缝的减震效果具有一个有效作用范围,在比例距离范围为0.031～0.051kg1/3/m时,减震效果为15%～30%.试验中预裂缝对爆破地震波的透射率为19%～31%.频谱分析表明,预裂缝对爆破地震波的振动频率具有选择吸收的作用,相当于一个滤波器.经预裂缝作用下的爆破地震波在近测点处具有2个明显主振频带;随着传播距离的增加,地震波的两主振频带信号开始混叠,频带逐渐接近并表现为一个主振动频带.

Study on the Effect of the Pre-split in Propagation of the Blasting Seismic Waves

The propagation law of the blasting seismic waves transmitting through the weakly rotten granite site, where a 26 m in length and 7 m in deep is created by the pre-splitting blasting technique, is studied. The result shows that the damping effect of the pre-split is related with the distance between the pre-split and the point of the seismic wave data collected. By regressing the vibration velocities and the scaled-distance, the formulations show that there exists an effective range that the pre-split weakens the seismic vibration in a large scale. In the range of sealed-distance 0. 031 -0. 051 kg^1/3/m, the damping ratio will be in the range of 15% -30%. To the experiment site, the transmission rate of the pre-split to the blasting seismic waves is about 19% -31%. The frequency spectrums show that the pre-split selectively absorbs the blasting seismic signal of the special frequency part. The wave transmitted through the pre-split is mainly composed of two predominating frequency band parts of the signals. With the increase of the distance, the two frequency bands become closer. To some distanee g the frequency spectrum of the blasting seismic manifests one frequency band.