城区基坑开挖爆破振动预测及控制研究

Study on Prediction and Control of Blasting Vibration in Urban Foundation Pit Excavation

为研究复杂环境下城区基坑开挖爆破振动预测及控制措施,依托现场爆破试验分析了质点峰值振速与主振频率的响应规律,基于以上两个因素提出了爆破振动预测方法。探讨了逐孔起爆与减振沟的降振效果,获得了减振沟的最佳降振范围,制定了爆破振动的控制措施。结果表明:在爆破振动预测方面,通过考虑实际最大单孔药量、实际总药量提出的质点峰值振速及主振频率预测公式实现了对爆破振动的综合预测,其预测值较仅以最大单孔药量的预测值更小,预测精度提高了3.2%。在爆破振动控制方面,现场实施的逐孔起爆与减振沟降振措施效果良好,爆破振动表现为低振速、高频率、短持时的特点。其中,减振沟的降振效果显著,综合考虑质点峰值振速、信号频带能量分布及瞬时输入能量的响应规律,在减振沟背爆侧1~6 m作用半径内降振效果最佳,1 m作用半径内的降振比率最高可达77.5%。对于类似工程,可借鉴爆破振动预测公式进行预先评估,当建筑物距离爆区≤10 m时,建议参考减振沟开挖规模实施降振措施。

In order to study the blasting vibration prediction and control measures of excavation in urban area under complex environment,the response law of peak particle vibration velocity and main vibration frequency is analyzed based on field blasting tests,and the blasting vibration prediction method is proposed based on the above two factors.The vibration reduction effect of hole by hole initiation and vibration reduction ditch is discussed,so that to obtain the optimal vibration reduction range of the ditch.And the control measures of blasting vibration are also formulated.The results show that the prediction formula of the peak particle vibration velocity and main vibration frequency is realized by considering the actual maximum single-hole charge and the actual total charge.The predicted value is smaller than that solely based on the maximum single-hole charge,and the prediction accuracy is increased by 3.2%.In the aspect of blasting vibration control,the blasting vibration is characterized by low vibration velocity,high frequency and short duration.Among all the measures,the effect of the vibration reduction ditch is remarkable.Considering the peak particle velocity,signal frequency band energy distribution and instantaneous input energy response law,the vibration reduction effect is the best within 1~6 m radius on the side of the ditch opposite to the blast source,and the maximum vibration reduction ratio can reach 77.5%within 1 m radius.For similar projects,the proposed blasting vibration prediction formula can be used for pre-assessment.When the distance of the building from the explosion zone is less than 10 m,it is recommended to implement vibration reduction ditch.