城市岩溶深基坑爆破振动影响研究

Impact of Blasting Induced Vibration in Deep Excavation inKarst in Urban Environment

在岩溶发育地区进行基坑爆破开挖时,产生的振动可能导致岩层裂隙扩张、破碎,进而发生溶洞塌陷,造成严重的工程安全问题。基于爆破振动监测实例,研究城市岩溶地区深基坑爆破开挖产生的振动对周围环境及溶洞的稳定性带来的影响,以及该场地爆破振动的衰减规律,进而确定合理的溶洞处理方案及爆破施工方案。分别采用顶板抗弯、抗剪强度评价硐室稳定法对该场地溶洞进行了爆破振动下的稳定性分析;基于保护对象及支护结构处振动监测数据,获得了相应的峰值振速衰减经验公式,公式中的场地系数K值及衰减指数α值与传播介质的硬度呈负相关;针对该岩溶深基坑周边及基底以下溶(土)洞,确定了相应的岩溶处理范围原则及措施方案。

During the blasting and the deep excavation for foundations in well-developed karst areas,the vibrations by the blasting might cause the cracks of the rock cavities to expand and break,and then lead to the collapse of the karst cavities,it may also cause serious engineering safety hazards.Based on the blasting vibration monitoring,this paper studies the impact of vibrations generated by blasting excavation of the foundations in urban karst areas on the surrounding environment and the stability of karst cavities.And the attenuation pattern of the blasting vibration at the site is studied.This paper also investigates the reasonable cavity treatment plan and blasting construction plan.The results show that the stability analysis of the cavity under the blasting vibration is performed by using the chamber stability method for evaluating the flexural and shear strength of the roof respectively.Based on the vibration monitoring data of the protection object and the supporting structure,the corresponding empirical formula of the peak vibration velocity attenuation is obtained.The site coefficient K and the attenuation index α in the formula are negatively correlated with the hardness of the propagation medium.For the karst(soil)cavities around the deep karst excavation and below bottom of excavation,the corresponding karst treatment scope principles and measures are determined.