消能棚洞冲击信号动力特征

考虑落石下落高度、质量、形状和垫层厚度等参数, 采用室内模型试验研究了消能棚洞冲击信号的动力特征, 获得了冲击信号的频谱和自相关曲线, 分析了冲击信号的时频特征和最大频谱对应的振动频率及其变化规律, 并基于小波分析方法提取了各个频段的冲击信号, 获得了冲击信号能量的主要分布范围。研究结果表明: 随着落石下落高度的增加, 棚洞顶板中心处冲击信号的频谱幅值增大, 且该冲击信号的频谱有4个峰值, 呈对称分布; 不同形状落石冲击棚洞时冲击信号频谱幅值由大到小的顺序依次为球形、长方体、立方体和圆柱体; 普通棚洞顶部垫层越厚、落石质量越小时, 棚洞顶板中心处冲击信号的频谱幅值越小; 当5 kg球形落石从0.5 m高处下落冲击顶部未铺设垫层的棚洞时, 消能棚洞冲击信号的最大频谱和自相关曲线峰值较普通棚洞分别降低了60.98%和82.57%;当5 kg球形落石从2 m高处下落冲击顶部未铺设垫层的棚洞时, 消能棚洞的落石冲击能量主要分布在冲击信号频率15.625~62.500 Hz处, 占总能量的63.73%, 普通棚洞的落石冲击能量主要分布在冲击信号频率0~15.625 Hz处, 占总能量的74.30%。可见, 消能棚洞设计时应主要考虑中频冲击, 而普通棚洞设计时应主要考虑低频冲击。 

Impact signal dynamic characteristics of energy dissipation shed tunnel

Considering the rockfall falling height, mass, shape and cushion thickness, the impact signal dynamic characteristics of energy dissipation shed tunnel were studied by the indoor model test. The spectrums and autocorrelation curves of impact signal were obtained. The time-frequency characteristics of impact signal and the vibration frequency and its change law corresponding to the maximum spectrum were analyzed, and the impact signal of each frequency band was extracted based on the wavelet analysis method. The main energy distribution range of impact signal was obtained. Research result shows that the spectrum magnitude of impact signal at the center of shed tunnel roof increases as the rockfall falling height increases, and this spectrum of impact signal has four peaks with a symmetric distribution. When rockfalls with different shapes impact the shed tunnel, the order of spectrum magnitudes of impact signals from big to small is spherical, cuboid, cube and cylindrical. The thicker the ordinary shed tunnel roof cushion and the smaller the rockfall mass, the smaller the spectrum magnitude of impact signal at the center of shed tunnel roof. When a 5 kg spherical rockfall falls from the height of 0.5 m to impact the shed tunnel without cushion at the top, the maximum spectrum of impact signal of energy dissipation shed tunnel and the peak of autocorrelation curves are 60.98% and 82.57% lower than those of ordinary shed tunnel, respectively. When a 5 kg spherical rockfall falls from the height of 2.0 m to impact the shed tunnel without cushion at the top, the rockfall impact energy of energy dissipation shed tunnel mainly distributes in the frequency range of impact signal from 15.625 to 62.500 Hz, accounting for 63.73% of total energy. The rockfall impact energy of ordinary shed tunnel mainly distributes in the frequency range of impact signal from 0 to 15.625 Hz, accounting for 74.30% of total energy. Thus, the medium-frequency impact should be considered priorly when designing an energy dissipation shed tunnel, and the low-frequency impact should be considered priorly when designing an ordinary shed tunnel.