卸压爆破下强冲击危险巷道围岩振动规律试验分析

Experimental analysis on vibration of roadway with strong probability of rockburst subjected to pressure relief blasting

针对目前参数设计不合理的卸压爆破常常导致巷道围岩损伤破坏,降低防冲效率的问题,采用PASAT-M型便携式微震探测系统,在煤矿井下现场原位开展煤层爆破振动试验,并结合预先加窗短时Fourier变换技术,定量研究卸压爆破下强冲击危险巷道围岩的振动规律。研究表明:(1)在距震源20 m范围内,爆破帮的振动主频随距震源距离的增大呈指数关系增大,顶板的振动主频随距震源距离的增大呈线性关系单调递增,而非爆破帮的振动主频随距震源距离的增大呈二次曲线关系先升高再降低;(2)爆破帮的振幅随距震源距离的增大呈指数关系衰减,超过20 m范围卸压爆破对围岩的损伤破坏效应变得十分微弱;(3)由于巷道各个方位的围岩受到面波和体波的影响程度各不相同,导致了不同方位围岩振动特征(类型、主频和振幅)的差异性;(4)卸压爆炸下巷道各方位围岩的振动类型、主频和幅值并不一致,由此爆破震动波下的损伤破坏效应也有较大区别。结合上述现场实测结果和现有理论,从控制卸压爆破振动的幅值、频率和持续时间3个指标以及增加巷道围岩抗震性能方面,提出优化爆破参数,防止卸压爆破对巷道围岩损伤的建议。

Pressure relief blasting often leads to the damage of the surrounding rock and reduces the efficiency of rockburst controlling because of unreasonable design of the parameters of the blasting. The vibration and damage of surrounding rock of roadway with strong probability of rockburst under pressure relief blasting were studied quantitatively through the in-situ measurement with the portable microseismic detection system PASAT-M combined with the short pre-windowed Fourier transform technique. With increase of the distance between the source and sensor,the dominant frequencies in the mining wall and roof increase monotonically. The blasting dominant frequency in non-mining wall reduces firstly and then increases. The amplitude of blasting wall decays exponentially with the increase of the source distance,and the damage of the surrounding rock is very weak over 20 m range. Because of the different influence of surface wave and body wave,the differences of the vibration characteristics（type,dominant frequency and amplitude） of the surrounding rock are different. Vibration types, dominant frequency and amplitude of at different positions of the surrounding rock of the tunnel were not consistent with each other,so damage effect of the blasting vibration wave is very different from place to place. Based on different failure patterns,suggestions were proposed to prevent the roadway from damage by controlling amplitude,dominant frequency band and duration of vibration. In addition,the impact resistance performances of structure should be improved.