Recently, the Guanghua Intercity Railway added another shield tunneling machine, the "Tiebing Guanghua No. 10" shield machine, which officially launched at the shield shaft in the Baibai section (the "Baiyun Dongping Station to Baiyun City Center Station section").

In parts of the section, the cavity encounter rate exceeds 90%.

"Tiebing Guanghua No. 10" is an earth pressure and slurry dual-mode shield machine, responsible for the left-line shield tunneling work from the shield shaft in the Baibai section to Baiyun Dongping Station.

The Baibai section has a total length of about 4.4 kilometers. The route needs to pass beneath the existing Metro Line 3 and Line 14, the under-construction Fangcun to Baiyun Airport Intercity Line, and the Guangcong Fault Zone, with high settlement control requirements. The geological conditions in the section crossed by the shield machine are complex, with strong karst development and a cavity encounter rate of 70.2%, of which the local cavity encounter rate exceeds 90%, with a maximum cavity height of about 28 meters, posing high safety risks and great technical difficulty.

To cope with the complex and variable geological conditions, Guangzhou Metro, the Guanghua Intercity General Contracting Department of China Railway Construction South China Construction, together with the builders of China Railway 12th Bureau, drew on construction experience in similar strata and selected a shield machine with earth pressure and slurry dual-mode functions. This shield machine can switch between different tunneling modes in soft strata such as silty clay and strongly weathered argillaceous siltstone, and in composite strata such as moderately to slightly weathered limestone with developed karst cavities and fault sections, better adapting to tunneling work under special and complex geological conditions and better ensuring construction safety.

In response to the technical challenges of shield construction in karst-developed areas, the builders, on the one hand, installed multiple advanced grouting holes and configured a zero-position detection system, enabling advance grouting reinforcement at any time and real-time monitoring of the cutterhead rotation status, ensuring the effectiveness of face grouting reinforcement and center coring, and achieving safe passage through soft rock, mucky clay strata, and collapse-prone sections. On the other hand, reserved radial injection holes were set on the outer periphery of the shield body to enable timely injection of high-concentration bentonite and parameter correction, thereby suppressing surface settlement. In addition, by installing freezing circulation pipelines on the cutterhead and circulating brine at minus 30°C to freeze the moisture in the soil in front of and around the cutterhead to form a frozen soil curtain, cutter replacement under atmospheric pressure was achieved, laying a solid foundation for the safe breakthrough of the shield section.

To ensure the shield machine safely and smoothly passes through karst areas and building clusters, the project construction team surveyed the strata through various methods such as cross-hole CT, thoroughly identifying the development of karst strata along the route, and identified risk sources such as pipelines, surrounding buildings, and rivers, predicting risks in advance and formulating special treatment plans such as pre-reinforcement. At the same time, experts were invited to assess and analyze various risks and provide feasibility recommendations. In addition, the construction project department strengthened communication and collaboration with relevant government departments, property rights units, and other parties, formulated emergency plans according to local conditions and carried out emergency drills, and established a rapid emergency response mechanism to provide guarantees for safe construction.

Project Progress

As of now, the civil engineering works of the Guanghua Intercity Railway (Guangzhou East–Huadu Tiangui) have been completed cumulatively at 28%. Civil construction is underway at 7 stations along the entire line; of the 7 sections, 5 are under civil construction and 2 are in preliminary preparation; a total of 8 shield machines are tunneling. Civil construction is underway at the Airport Depot.