At 7:18 a.m. on April 23, 2019, following the detonation command, our company successfully carried out the blasting demolition of the No. 2 dock cofferdam of the 300,000-ton-class dock at Zhoushan Huafeng Shipbuilding & Repair Co., Ltd.
The No. 2 dock is 380 meters long, 68 meters wide, and 14.8 meters deep. The main structure of the dock is made of concrete, and the blasting area was the rock cofferdam on the north side, with a total blasting volume of 30,000 m³.
The project had a tight construction schedule and extremely complex surrounding conditions. On the east side of the blasting area, the distance to the cofferdam pier was only 1 meter, the distance to the pump house was 16 meters, and the distance to the granite facing was 11.7 meters. On the west side, the blasting area was 16 meters away from the shipyard wharf.
Horizontal gently inclined holes were adopted for drilling. Parallel holes were arranged in the middle section of the cofferdam, while fan-shaped holes were arranged on the east and west sides. Vertical auxiliary holes were installed in the top masonry section, and pre-splitting holes were arranged at the boundary between the two wings of the fan-shaped holes and the rock excavation area. Before blasting, the cofferdam interior was filled with water through natural tidal flow, and detonation was carried out during low tide.
To ensure the safety of the dock piers, granite facing, pump house, and wharf piles, the maximum charge per delay was strictly controlled according to the allowable safety standards of each protected structure. Considering the influence of water-filled blasting and ensuring reliable transmission of detonation, the project ultimately adopted a “central opening, top-down” V-shaped multi-circuit hole-by-hole initiation system.
A total of 464 blast holes were drilled for this operation, with a cumulative drilling length of 8,100 meters. The project used 40 tons of explosives and 2,063 high-precision water-resistant detonators.
According to available information, among blasting demolition projects involving cofferdams of the same scale, this project featured the closest proximity to surrounding buildings and structures, the largest blasting volume, and the highest single-shot explosive charge.
All employees involved in the cofferdam project worked tirelessly day and night and fought together for nearly two months. Their efforts ultimately led to the successful completion of the blasting operation. According to monitoring data from a third-party testing organization, the blasting demolition caused no adverse impact on the surrounding environment, earning unanimous recognition and praise from the project owner and local authorities.
The successful completion of this project marks a new level in the company’s capabilities in refined technical design, construction organization, and project management for highly challenging and complex blasting operations.