50t科学爆破振动的衰减特征及地形效应

Attenuation characteristics and topographic effect of a scientific explosion with 50 t explosive

对药量达50t的科学爆破开展了流动强震观测,包括爆破振动的衰减观测和地形效应观测。在分析此次爆破强震记录的基础上,利用萨道夫斯基公式分析了垂直向峰值速度和加速度的衰减规律,爆破地区为中等强度的层状岩石且当地地形沟壑纵横是此次振动能量衰减较快的原因。通过离散小波变换分析(db8小波基函数)得到了此次爆破振动能量的时频分布规律,随着爆心距的增大,爆破振动能量集中的频率减小而振动的持续时间则相对增加。根据中国地震烈度表,在近爆心区振动烈度可以达到Ⅶ度,然而相对于天然地震的烈度衰减,爆破振动烈度的衰减较快。通过比较一个高14m山包的不同位置的强震记录,分析了此次爆破振动的地形效应。由于山包的聚焦效应,山顶的加速度峰值是山脚的2.4倍,且地形效应对某频率段内的振动有选择的放大,该频率段与山包的大小和高度有关。振动轨迹图显示,随着高度的增加,山体的侧向摆动和转动逐渐增强。

Vibration attenuation and topographic effect were monitored near the explosion place of 50 t explosive. Based on the recorded vibration signals, the attenuations of vertical velocity and acceleration were analyzed with the Sadauskas formula. The rapid attenuation of vibration was related with the layered moderate-hardness rocks and the local terrain and gully. The time-frequency distribution of the vibration was obtained by the discrete ~vavelet transform （db8 wavelet）. The frequency of vibration energy concentration was reduced and the duration of the vibration was prolonged with the increase of the distance from the explosion center. According to the Chinese Seismic Intensity Scale, the vibration intensity close to the explosion center is up to Ⅶ, however, the blasting vibration intensity decay faster than the attenuation of earthquake intensity. The topographic effect was discussed by comparing the vibration records at different locations of a 14-m-high hill. Due to the focusing vibration energy of the hill, the peak acceleration on the top of the hill is 2.4 times larger than that at the foot of the hill, and the special frequency bands with the enlarged amplitude is related with the size and the height of the hill. The figure of particle motions indicates that the lateral swing and rotational motion gradually increase from the foot to the top of the hill.