钻爆法原位扩建隧道的振动监测分析

Vibration monitoring and analysis of tunnel in-situ expansion by drilling and blasting method

为了研究城市环境下钻爆法施工对周边环境的振动影响,以福州市马尾隧道原位扩建工程为背景,在北洞钻爆扩挖过程中,对南洞衬砌结构上的振动效应进行跟踪监测。通过选取单段最大装药量、爆心距为变量,归纳整理峰值振速的规律,并采用萨道夫公式拟合空洞赋存条件下的振速衰减规律。结果表明,既有空洞对爆破振动的衰减有很大影响:以II级围岩段为例,单空洞情况下其衰减指数α为1.476,接近硬岩的上限;而双空洞情况下其衰减指数α达到1.836,已落入软岩的推荐取值范围。拟合公式可应用于赋存空洞条件下的爆破振速估算;同时建议后续南洞扩挖及类似扩建工程中,可以充分发挥既有空洞的减振效应,适当加大进尺、缩短工期、提高施工效率。

In order to study the vibration impact of drilling and blasting construction on the surrounding environment in an urban environment,taking the in-situ extension project of the Mawei Tunnel in Fuzhou as the background,during the drilling and blasting expansion of the north tunnel,the vibration effect on the lining structure of the south tunnel was monitored.By selecting the maximum charge of a single segment and the burst center distance as variables,the law of peak vibration velocity is summarized,and the law of vibration velocity attenuation under the condition of cavity occurrence is fitted by the Sadolph formula.The results show that the existing cavities have a great influence on the attenuation of blasting vibration.Taking the surrounding rock mass of classification II for example,the attenuation indexαis 1.476 under the single cavity condition,which is close to the upper limit of hard rock,while in the case of double cavities,the attenuation indexαreaches 1.836,which has fallen into the recommended value range of soft rock.The fitting formula presented can be used to estimate the blasting vibration velocity under the cavity condition.At the same time,considering the vibration reduction effect of the existing cavity,it is suggested to increase the length of construction footage and shorten the construction period so as to improve the construction efficiency in the subsequent expansion of south tunnel as well as some other similar expansion projects.