Recently, the shield machine of the left-line shield tunnel in the Xiancun to Guangzhou East section (hereinafter referred to as the Xian-Guang section) of the post-opening section of Guangzhou Metro Line 18 successfully broke through, marking that all shield tunnels in the post-opening section of the line have been completed.

It is understood that the left and right lines of the Xian-Guang section shield tunnel, which achieved dual-line breakthrough, are 1,981 meters and 1,997 meters long respectively. A shield shaft is set in the middle of the section. The section from Xiancun to the shield shaft adopts an earth pressure balance shield machine, driving from the shield shaft toward Xiancun Station, while the section from the shield shaft to Guangzhou East Station adopts the mined method.

Since the section tunnels are all located in the city center, they need to pass beneath urban trunk road tunnels, existing operating metro lines, commercial buildings, etc., and the geological conditions are complex, making construction difficult and the risk level high. Among these, crossing major risk sources is a major challenge faced during shield tunneling. The shield section has developed fissure water and abundant groundwater; tunneling in water-rich hard rock strata makes it difficult to control shield tunneling parameters, and the tunnel needs to pass beneath the existing operating Line 1 and Line 3, with a vertical clear distance of only 3.3 meters from the Line 3 tunnel, posing considerable construction risk.

To successfully complete the shield tunneling task and ensure the shield machine safely crosses adverse geology, Guangzhou Metro, together with metro builders from the General Contracting Department for Lines 18 and 22 of China Railway Construction South China Construction and China Railway 12th Bureau, conducted detailed surveys of the stratum structure around the intersection of the existing Line 1 and Line 3 with the Xian-Guang section, established a trial tunneling section, and analyzed tunneling parameters, providing strong data support for the shield machine to safely cross major risk sources. At the same time, experienced shield machine operators were arranged to ensure the shield machine safely and smoothly crosses major risk sources.

Because the shield launching shaft is short in length, metro builders adopted the split launching method and optimized the cable retraction and extension method, reducing the difficulty of manually extending cables and decreasing cable usage. In addition, a device for reusing wastewater in the tunnel for soil conditioning was installed. By connecting the shield machine's sewage pipe in series with the slag-soil separator, the soil chamber water tank, and other devices, remote control of the water added to the soil chamber was achieved from the shield machine trolley operation room, successfully saving construction costs, improving construction efficiency, and increasing the wastewater utilization rate.

Previously, the first opening section of Line 18 from Wanqingsha to Xiancun was successfully opened in September 2021. As of now, the civil engineering works of the post-opening section of the line (Xiancun–Guangzhou East Station) have cumulatively completed 36%, and the section is advancing mined tunneling and other civil engineering construction.