Controlled Blasting Technology for Connection Passage between Metro Shield Sections in Hard Rock Stratum

Objective At present, a relatively systematic, mature and rapid excavation construction method for the connection passage construction in hard rock stratum has not been formed yet. Due to the small cross-section and limited operating space in the connection passage, construction with the conventional construction method is less efficient with significant construction risks. Therefore, it is necessary to conduct in-depth study on the technology of controlled blasting in the connection passage of metro shield section in hard rock stratum. Method Taking the connection passage in a shield section of Fuzhou Metro Line 4 as a case study, the controlled blasting technology suitable for this project is proposed. According to the engineering characteristics of the project, the calculating parameters required by the maximum single blast charge for a single-section are set up. In addition, based on the distance between the designed connection passage and the objects to be protected, three levels of maximum single-section charges are calculated, and the schemes for blasting hole design, charge structure design and charge blockage are proposed. Six ground settlement measuring points are selected on the ground above the connection passage, and the settlement curves of the six points during construction are obtained to analyze the influence of blasting on ground settlement. Result & Conclusion The measures of reserving protection layers, treating rock masses as rock walls, shallow hole differential blasting, and digital micro-difference initiation being taken in the process of construction, effectively reduce the explosion impact and blasting vibration, achieving the preset goal of safe blasting and rapid excavation.