大断面隧道新浇二衬混凝土爆破振动控制安全阈值

Safety threshold of blasting vibration control of newly cast secondary lining concrete in large section tunnel

大断面隧道新浇二衬混凝土的强度较低,在爆破施工过程中易受到破坏。为研究新浇二衬混凝土爆破振动控制标准,结合大断面龙南隧道工程,采用现场监测与数值模拟相结合的研究方法,分析不同龄期大断面隧道新浇二衬混凝土在爆破振动作用下的动力响应特征,得出新浇二衬混凝土爆破振动控制安全阈值。研究结果表明:隧道二衬拱顶z方向振动速度和拉应力大于其他部位,峰值振动速度6.66 cm/s和峰值拉应力1.57 MPa出现在拱顶,拱顶是最危险位置;不同龄期下二衬拱顶的爆破振动速度随爆心距的增大呈指数衰减趋势,随着混凝土龄期的增加而衰减,且不同方向衰减趋势有差异;基于数值模拟结果和动态抗拉强度理论,大断面龙南隧道新浇二衬混凝土爆破安全振动速度阈值为2.80 cm/s。

The strength of newly poured secondary lining concrete in large section tunnel is low,which is easy to be damaged during blasting construction.In order to study the blasting vibration control standard of newly poured secondary lining concrete,combing the large section Longnan tunnel project,field monitoring and numerical simulation were adopted to analyze the dynamic response characteristics of newly poured secondary lining concrete under blasting vibration in large section tunnels of different ages,and the safety threshold of blasting vibration control of newly poured secondary lining concrete were obtained.The results show that the vibration velocity and tensile stress in the z direction of the tunnel secondary lining vault are greater than those in other parts.The peak vibration velocity of 6.66 cm/s and the peak tensile stress of 1.57 MPa appear in the vault,and the vault is the most dangerous position;Under different ages,the blasting vibration velocity of the secondary lining vault decreases exponentially with the increase of blasting center distance,and decreases with the increase of concrete age,and the attenuation trend is different in different directions;Based on the numerical simulation results and dynamic tensile strength theory,the safe vibration velocity threshold of blasting vibration of newly cast secondary lining concrete in Longnan tunnel with large section is 2.80 cm/s.