On July 10, the cutterhead of the "Yongxing No. 1" shield machine began to rotate slowly and set off toward Zaohu Station, marking the official entry of Phase I of Qingdao Metro Line 9 into the mechanical tunneling stage.

The "Yongxing No. 1" shield machine is responsible for the right-line tunneling of the Haixi Village Station–Zaohu Station section (the "Hai-Zao section"), with a total length of nearly 1.7 kilometers.

Construction personnel detected in advance that there is a fault zone in the shield tunneling section after Haixi Village Station. For this reason, this shield machine was specially improved into a "earth pressure + TBM" dual-mode shield machine, which can achieve two functional modes: composite earth pressure mode tunneling and rock tunnel mode tunneling. When "Yongxing No. 1" enters long-distance ultra-hard rock stratum tunneling, it can switch to TBM mode for tunneling. In TBM mode, the boring machine has high rotational speed and fast tunneling efficiency. When the tunneling of the hard rock section is completed, the mode conversion is carried out inside the tunnel, switching from TBM mode to earth pressure mode to continue tunneling. Compared with the traditional mining method, the dual-mode tunneling construction of "soft when encountering soft, hard when encountering hard" will be 3-5 times faster.

It is understood that before being put into the construction of Phase I of Qingdao Metro Line 9, the "Yongxing No. 1" shield machine had already participated in the construction of Beijing Metro Line 12 and Beijing Metro Line 3. The "upgraded" "Yongxing No. 1" not only surpasses some new machines in tunneling performance and other aspects and meets construction requirements, but also costs only two-thirds of a new machine. Compared with purchasing a new machine, the remanufacturing of the entire machine can save more than 12 million yuan, while also saving 209 tons of steel. Calculated in standard coal, it can save 260 tons of coal and reduce carbon dioxide and other harmful gas emissions by nearly more than 700 tons.

The Phase I project of Qingdao Metro Line 9 starts at Haixi Village Station and ends at Qianjin Community Station, with a total length of 16.36 kilometers and 13 stations, running east-west through the core area of Chengyang. After the line is completed and opened to traffic, it will further enhance the status of Qingdao's northern comprehensive transportation hub and is of great significance to accelerating the construction of the Qingdao metropolitan area.