Recently, the longest single-line shield tunnel on the Guangzhou-Foshan East Ring Intercity Railway's Guangzhou South Station to Baiyun Airport section (hereinafter referred to as the "Guangfo East Ring Intercity") — the upward line of the "Dayuan Station-Taihe Station" section (hereinafter referred to as the "Datai Section") — was successfully holed through, marking the completion of tunnel boring across the entire Guangfo East Ring Intercity line ("hole-through").

According to reports, the Datai Section of the Guangfo East Ring Intercity is a controlling project for the entire line. Its upward line is 6,144 meters long, with a tunnel outer diameter of 8.8 meters, an inner diameter of 8 meters, and a ring width of 1.8 meters. The geological conditions along this tunnel section are quite complex, passing through typical composite strata of the Pearl River Delta region, including not only Quaternary alluvial-proluvial and residual slope deposits, but also Carboniferous siltstone, quartz sandstone, conglomerate, limestone, carbonaceous limestone, and carbonaceous slate, as well as Sinian gneiss and Yanshanian granite.

According to reports, the tunnel depth ranges from 12 to 158 meters, with abundant groundwater and extremely high water pressure. It crosses long distances through hard rock sections such as gneiss and granite, where the hard rock strength is high — especially in the moderately weathered gneiss section, where the maximum saturated compressive strength is about 155 MPa. This section contains numerous hard rock protrusions and soft-over-hard ground areas, crosses 8 fault fracture zones, multiple weathering-induced perched-water troughs, and boulders, and passes beneath (or alongside) numerous structures such as expressways and operating railways, making construction extremely difficult.

Because no intermediate shaft could be added in the middle of the 6,144-meter tunnel, the shield machine had to bore in a single heading, making equipment selection extremely stringent. After multiple rounds of demonstration and study, the construction contractor, together with the design unit, the shield machine manufacturer, and renowned domestic tunnel industry experts, proposed and successfully applied the construction method of "single-shield and earth pressure balance dual-mode boring machine construction and in-process mode conversion," solving the problem of no space for an intermediate shaft in a long and large tunnel.

The successful hole-through of the tunnel verifies the feasibility of a dual-mode large-diameter shield machine and TBM, and marks the first successful single-head boring of a large-diameter railway tunnel exceeding 6,000 meters using a "single-shield and earth pressure balance dual-mode" machine in China, providing valuable reference experience for existing dual-mode shield construction technology and similar projects.