大型溶洞群深基坑爆破对邻近京广铁路的影响

Influence of Deep Foundation Pit Blasting of Large Karst Cave Group on Adjacent Beijing-Guangzhou Railway

为了研究城市大型覆盖型溶洞群基坑爆破对施工安全的影响,以广州一邻近京广铁路的深基坑爆破工程为例,结合特殊岩溶地质条件,采用现场爆破振动测试和监测方法,分析爆破对邻近京广铁路和支护结构的影响。结果表明:建立了同一场地不同区域的峰值振速衰减经验公式,其中场地系数K、衰减指数α会随传播介质硬度的降低而增大;爆心距及传播介质的软硬程度对竖向主振频率的衰减有所影响,因松软岩土体较少传递高频脉冲,故随爆心距的增加,主振频率逐渐降低,且主频的分布趋向集中;通过理论计算,得到爆破最大单段药量及飞石飞散距离;提出了相对应的岩溶处理方案及减振设计方案,并通过现场监测及理论计算印证其可行性,为岩溶场地类似基坑爆破开挖工程提供参考。

In order to study the impact of the blasting of large-scale covered caverns on construction safety,this paper takes a deep foundation pit blasting project adjacent to the Beijing-Guangzhou Railway in Guangzhou as an example.Combined with the special karst geological conditions,the impact of blasting on the neighboring Beijing-Guangzhou Railway and supporting structures was analyzed by the method of on-site blasting vibration testing and monitoring.The results show that this paper establishes an empirical formula for the attenuation of peak velocity of particle vibration in different areas of the same site,in which the site coefficient K and attenuation indexαwill increase with the decrease of the hardness of the propagation medium.The burst center distance and the hardness of the propagation medium have an effect on the attenuation of the vertical main vibration frequency.Because soft rock and soil rarely transmit high-frequency pulses,with the increase of distance from explosion source,the main vibration frequency gradually decreases,and the distribution of the main vibration frequency tends to be concentrated.Through theoretical calculations,the maximum single-stage charge of blasting and the flying distance of flying rocks are obtained.The corresponding karst treatment plan and vibration reduction design plan were put forward,and the feasibility was confirmed through on-site monitoring and theoretical calculations,which provided a reference for similar foundation pit blasting and excavation projects in karst sites.