As the Shenzhen-Zhongshan Link opens to traffic, Ma Dingqiang, the project manager of the Bridge at China Communications Construction Company Guangzhou Dredging Co., Ltd. (CCCC Guangzhou Dredging Co.), shared an untold detail with Yangcheng Evening News. During the excavation of the trench and the dredging of the channel for the immersed tunnel of the Shenzhen-Zhongshan Link, the project team abandoned the traditional, more economical, and faster blasting method. Instead, they adopted a rock drilling construction method that is more environmentally friendly, costing an additional 30 million yuan to protect the habitat of the Chinese white dolphins.
The Shenzhen-Zhongshan Link is a world-class cross-sea passage integrating bridges, islands, tunnels, and underwater interchanges. It has set records such as the world's longest dual eight-lane underwater immersed tunnel and the world's widest underwater steel-shell-concrete immersed tunnel. Its underwater tunnel is approximately 6.8 kilometers long, with the immersed tube section about 5 kilometers.
Ma Dingqiang's team at CCCC Guangzhou Dredging Co. was mainly responsible for the excavation of the trench and the dredging of the channel for the immersed tunnel. He explained, "Previously, we also handled the excavation of the trench and the dredging of the channel for the immersed tunnel of the Hong Kong-Zhuhai-Macao Bridge. However, there is a major difference underwater between the two bridges. The tunnel area of the Hong Kong-Zhuhai-Macao Bridge was mostly covered with silt, clay, and sand, which are conventional soil types. In contrast, the Shenzhen-Zhongshan Bridge's immersed tube area contains nearly 300,000 cubic meters of weathered granite."
"Our task in the construction of the immersed tube tunnel is to excavate the bed for the placement of the immersed tubes. The most challenging thing is the excavation of the weathered rock in the immersed tube trench, with the deepest excavation point reaching approximately -38 meters, and even deeper with the tide," said Ma. "Among the nearly 300,000 cubic meters of granite, there are 20,000 cubic meters of moderately weathered granite, which is the hardest to deal with during dredging and considered a hard nut to crack."
Ma informed the reporter that the most efficient, economical, and conventional method to handle such rock using traditional dredging methods is blasting. However, the construction site is located at the Pearl River Estuary, which is a migratory route and an important habitat for the Chinese white dolphins. Blasting would undoubtedly destroy the living environment of the Chinese white dolphins. Using an uncommon rock drilling method instead of blasting would increase costs and potentially delay the construction schedule. "We compared the costs of the two methods and found that using the rock drilling method would increase costs by over 30 million yuan."
Should they use blasting or switch to rock drilling? After comparison and discussion, the project team ultimately decided to discontinue the blasting plan and adopt the more environmentally friendly rock drilling method, using a 35-ton rock drilling rod for deep-water rock drilling.
Ma is glad that the project team chose this method. During the construction, he sometimes saw Chinese white dolphins leaping out of the water while on the ship and would take out his phone to record small videos. He has already done so several times.
According to public reports, the Shenzhen-Zhongshan Link also adopted other measures during its construction to protect the marine ecological environment. The construction team even set a record for fast island formation to reduce the impact on the Chinese white dolphins and manufacture various large components in factories before transporting them for offshore installation to minimize waste emissions.
Source | Yangcheng Evening News
