On the morning of April 25, the Tangkeng Tunnel, the first tunnel of the Shanmei Expressway reconstruction and expansion project under Guangdong Communications Group, was successfully holed through, two months ahead of the established schedule, laying a solid foundation for the project's first major traffic diversion at the end of this year.

The Shanmei Expressway reconstruction and expansion project has a total of 10 tunnels along its entire route, including 4 newly built tunnels and 6 reconstructed tunnels. The newly built Tangkeng Tunnel is located in Fengshun County, Meizhou City, Guangdong Province, and is a single-tube four-lane tunnel. The tunnel has a total length of 724 meters, a maximum buried depth of 117 meters, a maximum excavation width of 21 meters, and a maximum excavation cross-section of 239 square meters.

The Tangkeng Tunnel is a key route of the Shanmei Expressway reconstruction and expansion project and also an important controlling works. Since construction began in June 2023, the project has conducted comprehensive pre-assessment of the tunnel's geological conditions, adopted targeted construction methods, and after 300 days and nights of intensive work, finally reached the victorious moment of tunnel holing-through.

Construction using the sequential excavation method

Although the Tangkeng Tunnel is not long in mileage, it involves large cross-section excavation and is relatively difficult. The tunnel portal section has shallow cover and poor surrounding rock; the rock mass at the portal section is mainly composed of completely and strongly weathered granite, which softens easily when exposed to water and has a certain bias pressure, with poor self-stability and high construction safety risks. In addition, the newly built tunnel is close to the existing tunnel, imposing high requirements on blasting control; a pedestrian cross passage needs to be opened between the new and old tunnels, and construction near the operating existing Tangkeng Tunnel involves high technical requirements.

"Due to objective constraints, we adopted a single-direction heading method for the Tangkeng Tunnel. During construction, based on the engineering geological and hydrological conditions, we formulated corresponding construction plans and support parameters, adopted reasonable construction techniques, strictly controlled settlement, and ensured the structural stability of the large cross-section tunnel," introduced Lu Zhitao, head of the TJ2 bid project department of the China Railway 15th Bureau's Shanmei Expressway reconstruction and expansion project.

To solve the construction difficulties, the project organized multiple expert review meetings and conducted targeted research on key tunnel construction technologies and control methods. According to different surrounding rock conditions, the project adopted sequential excavation methods such as the double-side drift method, single-side drift method, and bench method, dividing the large cross-section into multiple parts and working faces for sequential excavation, while strictly controlling excavation advance and safety step distance to ensure construction safety.

Because the tunnel portal section has shallow cover, to ensure construction safety and structural safety, the tunnel adopted a small pilot heading to break through first, followed by reverse excavation after partial holing-through, ultimately achieving full cross-section holing-through.

Technology empowers safe construction

To ensure safe tunnel construction, the project adopted safety management systems including a tunnel network video monitoring system, tunnel emergency voice communication system, AI recognition technology, engineering vehicle speeding and positioning monitoring system, and tunnel emergency escape system, reducing safety accident risks through refined technological management measures.

"During tunnel construction, we continuously improved construction techniques based on actual conditions, innovated technological management measures, reduced construction risks, minimized environmental impact, and further improved engineering efficiency. At the same time, we made technical adjustments to the portal section and entered the tunnel ahead of schedule, ultimately achieving holing-through two months early," introduced Sun Keqiang, head of the Shanmei Expressway reconstruction and expansion project.

At present, the Shanmei Expressway reconstruction and expansion project has completed 75% of subgrade excavation and filling, 72% of bridge pile foundations, 40% of bridge substructures, and 65% of tunnel excavation. It is expected that this year the subgrade, bridges and culverts, and pavement on the traffic-maintaining side will be completed, realizing the first major traffic diversion.

The Shanmei Expressway reconstruction and expansion project is part of the "Longitudinal Line 2" of Guangdong Province's expressway network, with a total length of about 88 kilometers. It starts at the Jieyang interchange connecting with the S17 Jiepuhui Expressway, passes through Jiedong District of Jieyang City and Fengshun County, Xingning City, and Meixian District of Meizhou City, and ends at the Chengjiang interchange connecting with the G25 Changshen Expressway and S12 Meilong Expressway. The project is expected to be completed and open to traffic in mid-2026, when it will achieve two-way eight-lane traffic.

After completion, the project will play an important role in building Guangdong Province's new development pattern of "one core, one belt, one region," promoting infrastructure connectivity in the northeastern Guangdong region, supporting the implementation of the "Hundreds, Thousands, and Tens of Thousands Project," and advancing the revitalization and development of old revolutionary base areas and former Soviet areas.