Controlled Blasting Technology for Shallow-Buried Large-Section Tunnel below Susceptible Buildings in Coastal Stratum

Abstract

In order to solve the problem of blasting vibrations generated by the drilling and blasting method of the land section of an urban submarine tunnel, which has a great impact on the safety of the surrounding building (structure) structure and the life of the residents, this paper optimizes the blasting technology of the sensitive building (structure) section of an urban shallow-buried tunnel under complex geological conditions through field tests and theoretical calculations. The paper proposes the protection and reinforcement scheme of the building (structure), the auxiliary measures for controlling blasting and the optimization scheme of the control blasting parameters and verifies the design of the trenching of the guide hole, the gun hole, and the hole layout. The analysis of the data from the field test shows that using digital electronic detonators, controlling the maximum charge, reducing the size of the excavation section, and shortening the feed can significantly control the blast vibration of the surrounding buildings, combined with the “hollow hole + hollowing + wedge hollowing” plan and parameter optimization. In addition, when the tunnel crosses the surface buildings in close proximity, the grouting piles, isolation piles, and grouting are installed between the affected area and the building foundation, which can play an obvious role in vibration and settlement control. It can be seen that the blasting scheme adopted can effectively control the tunnel-blasting vibration speed within 0.5 cm/s, basically achieving sensorless blasting at the surface 10 m in front of the palm, and the surface-blasting vibration speed monitor outside the palm 20 m in front of the palm has no trigger, which greatly reduces the impact of tunnel-blasting construction on the surrounding environment and ensures the structural safety of the buildings (structures) around the tunnel.