严寒条件下岩体开挖爆破振动安全控制特性研究

Investigation of safety control for rock blasting excavation under cold condition

复杂条件下的岩体爆破振动安全控制是开挖关注的焦点问题。严寒条件下地表一定深度被冰冻,岩体的物理力学性质与波阻抗特性发生改变,导致爆破振动衰减特性发生明显变化。首先针对不同岩性的岩体,开展了冰冻条件下的岩体物理力学性能的对比试验,结果表明岩体被冰冻后弹性模量的增量百分比达30%;然后基于丰满水电站重建工程爆破开挖的振动测试,比较了冬夏季岩体爆破振动衰减规律的变化特征,结果表明冬季爆破振动的衰减速度明显低于夏季,二者存在一个明显的比例距离分界点,在该处冬夏季的爆破振动速度大小发生转变;进而基于数值模拟方法,研究了不同冰冻深度对爆破衰减参数的影响,提出了冬季与冰冻深度相关的爆破最大单段药量的数学表达;最后从地震波的频谱特性以及结构的强度极限等角度探讨了严寒条件对爆破振动安全控制标准的影响,结果表明,严寒条件下建筑物的爆破振动安全控制标准相比夏季可略有提高。研究成果可对广大严寒地区爆破施工的安全控制提供参考。

The safety control of blasting vibration under complex condition is the key problem of excavation.The rock mass is frozen under the cold condition,which induces the change of mechanical performance and wave impedance properties,and affects the blasting vibration attenuation characteristics.Firstly,the comparitive experiments are implemented to study the mechanical performance under different conditions.The results reveal that the increase of the elasticity modulus can reach as much as 30%.Based on the test results of the reconstruction project of Fengman Hydropower Station,the characteristics of blasting vibration attenuation for summer and winter are compared.The results reveal that a cut-off point about scaled distance exists,and the magnitude of the relationship changes at the cut-off point.The effect of cold depth is investigated,and a mathematical description for the maximum charge weight versus frozen depth is proposed.Finally,the effect of blasting vibration control standard is studied under cold condition from the angle of spectral characteristics of stress wave and the ultimate strength of the structure.The research results may provide the reference for the blasting safety control in the north cold excavation regions.