Influence of tunnel blasting vibration on secondary lining of new ultra short age concrete

In order to explore the influence of blasting vibration in tunnel construction on newly poured concrete of the second lining of tunnel, taking the blasting of upper bench face of stage IV surrounding rock bench construction as the source of vibration,blasting vibration tests were carried out on four kinds of concrete blocks with different strengths of different newly poured ultra-short ages at different spacings of blasting centers. After 28 d of curing, non-metallic ultrasonic testing instrument was used to test the propagation speed of ultrasonic wave in vibration concrete and ordinary concrete. Through the comparative analysis of the propagation speed, the defect and damage degree of the blasting vibration concrete were judged. The results show that under the condition of step construction in grade IV surrounding rock, the concrete blocks with a distance of 15 m from the blasting core are most affected by blasting vibration, and the concrete blocks with a distance of 30 m have the strongest ability to resist blasting vibration. Beyhond 30 m, the damage of blasting vibration to the concrete blocks is less and tends to be stable. The conclusion provides a reference for shortening the distance between the second lining and the face of tunnel to ensure the safety of tunnel construction. © 2020, Central South University Press. All right reserved.