Recently, the shield tunneling task for the right line of the Jinkai Road Station–Jiangnan Park Station section of Nanning Rail Transit Line 5 was successfully completed, achieving a smooth double-line breakthrough for the tunnel in this section.
The right line of the Jinkai Road Station–Jiangnan Park Station section of Line 5 is 1,152.5 m long, and the left line is 1,152.888 m long. The minimum curve radius is 450 m, and the maximum longitudinal slope is 27‰; the elevation difference between the highest and lowest points of the tunnel reaches 27 m. The left line of the section was launched on September 28, 2018, and the double-line breakthrough was completed in 260 days. The project has many long steep-grade sections, making shield tunneling and the horizontal transport system inside the tunnel highly challenging. Tunneling on long downhill grades can easily cause segment flotation and very easily lead to out-of-tolerance segment formation alignment.
The Jinjiang shield tunneling section mainly passes through mudstone. Shield advancement in this stratum is very prone to mud cake formation. By improving muck conditioning and grout mix proportioning technologies, the mucking rate was increased; shield tunneling parameters were adjusted promptly according to geological conditions; management of each process was strengthened; the “six special” system was strictly implemented; and the construction concept of “four modernizations and one green” was adhered to throughout the process, ensuring safety during the entire construction process and achieving a safe and smooth shield breakthrough.
This double-line breakthrough in the section adds momentum to the construction of Line 5 and lays a solid foundation for the breakthrough of the entire line.