红层软岩无中导洞连拱隧道爆破振动控制技术研究

无中导洞连拱隧道是一种新型的连拱隧道施工工法,而后行洞的爆破开挖将对先行洞衬砌结构产生振动影响。文章以云南楚姚高速陈家冲隧道为工程实例,开展红层软岩无中导洞连拱隧道的爆破振动控制技术研究。首先通过现场对比试验分析了连拱隧道爆破的三个主要影响因素:爆心距、装药量和应力释放。随后针对后行洞的三台阶开挖和两台阶开挖方式分别在先行洞对应区域进行自动化振动监测,并对监测数据进行回归分析,得到红层软岩V级围岩的爆破振动规律,通过反分析得出控制爆破振动的掏槽眼药量、导爆管雷管段数、经济合理的卸能孔个数及孔眼间距等,再结合现场工程状况,制定出符合现场需求的炮眼布置图和爆破方案。现场监测数据表明,修订后的振速临界值及优化的爆破方案符合安全要求,保证了无中导洞连拱隧道后行洞的顺利掘进以及先行洞的二次衬砌混凝土不被震裂。

Monitoring and Control Technology for Blasting Vibration of the Double-arch Tunnel without Middle Drift in Red-bed Soft Rock

Construction without middle drift is a novel method for the double-arch tunnel,and the blasting excava?tion of the subsequent tunnel will have a vibration impact on the lining structure of the antecedent tunnel.Taking the Chenjiachong tunnel of Chuxiong-Dayao expressway in Yunnan province as an example,it studies the blasting vibration control technology of double-arch tunnel without middle drift in red-bed soft rock.Firstly,the three main influence factors of the double-arch tunnel blasting are analysed:the distance between blasting sources,the explo?sive charge and stress release.Then automatic vibration monitoring is carried out in the corresponding area of the an?tecedent tunnel aiming at the three-bench、excavation and two-bench excavation of the subsequent tunnel,and the blasting vibration law of the V-level surrounding rock of the red-bed soft rock is obtained by regression analysis of the monitoring data,the explosive dosage of cutting hole,the numbers of nonel detonator segment and economic en?ergy unloading holes as well as the hole spacing are obtained by back analysis,a layout of the blast holes and blast?ing scheme are established to meet the needs of the site.The field monitoring data show that the revised critical val?ue of vibration velocity and the optimized blasting scheme meet the safety requirements and guarantee the smooth excavation of the subsequent tunnel and no vibration induced cracking in the concrete secondary lining.