Tunnelling Projects in the Host City Shenzhen

In Shenzhen, 385km long subway lines (including 267 stations) have been built recently and some major projects are under construction, such as Shenzhen-Zhongshan Immersed Tube Tunnel and Wanghai Road Tunnel etc. Besides, there is a wide variety of tunnel projects available for visits in the vicinity.

The 24km Shenzhen-Zhongshan Immersed Tube Tunnel is a complex underwater project consisting of bridges(17,129m), immersed tube tunnels(6,845m) eastern and western artificial islands, and an airport interchange (underground ramp section). The design speed is 100km/h and the service life is 100 years.

The immersed tube tunnel is a dual-carriageway, eight-lane steel shell concrete structure. Weighing about 80,000 tonnes, each standard element is 165m in length, 46m in width and 10.6m in height. With a floating distance of approximately 50km, the element will cross a number of busy waterways during floating and installation. The underwater connection accuracy is required to be controlled within ±5cm. The new structure of "steel shell+concrete" is used for the immersed tube, which has a large load-bearing capacity, good waterproof performance and significant social, economic and ecological value. The project started in April 2018 and is expected to be open for traffic in June 2024.

The total length of the Wanghai Road Tunnel is about 8.25 km, including a 5,295 m TBM tunnel section bored by two slurry TBMs with a diameter of 16.28 m. The TMB tunnel section has a minimum curve radius of R=520 m and encounters complex geological conditions and sensitive surrounding environment. The main strata are fully weathered, medium weathered, and slightly weathered granite, clayey soil and rockfill, with a uniaxial compressive strength of up to 138.9 Mpa. The tunnel segmental ring has an external diameter of 15.7 m, an internal diameter of 14.4 m, and a ring width of 1.8 m. With a design speed of 60km/h, the tunnel is designed as a double-deck, dual-carriageway, six-lane road tunnel. The construction duration is to be determined.

With a design speed of 200km/h, the13.69km long single-tube double-line tunnel involves the combined construction methods of TBM, NATM and cut and cover. The project consists of 1.65km cut and cover section, 5.52km NATM section and 6.52km TBM section. There are two TBMs (diameter: 13.32m) tunnelling from two ends and the tunnelling distance for each TBM is 3.59km and 2.93km respectively. The main project features include complex geological conditions, great depth, high water pressure and long distance TBM tunneling. The deepest part of the tunnel is 115m below water and the maximum water pressure reaches 1.06MPa. The construction work commenced in July 2020 and is expected to be completed in December 2025.

The main line of the Mingzhu Bay Underwater Immersed Tube Tunnel is a dual-carriageway, six-lane trunk road with a design speed of 50km/h. The total length of the main tunnel line is 5.667km, consisting of a 4.262km cut and cover section on land and a 1.405km immersed tube underwater section. The phase I of the project involves 4.915km tunnel including 3.935km cut and cover section and 0.98km immersed tube section. The construction work started in November 2022 and is expected to be finished in September 2026.

The Guangzhou-Guangzhou-Shenzhen Intercity Rail is located in the central part of the Pearl River Delta, and is the main line of the Pearl River Delta intercity network on the east bank of the Pearl River. With a design speed of 160km/h, the 21.142km Qianhai to Huanggang Port section is a further extension of the Intercity Rail, constructed by cut and cover and TBM methods. The 3.511km TBM section is a single-tune, double-line tunnel. The external diameter of the tunnel is 12.8m, and the TBM diameter is 13.27m. With an overburden of 10.7m-32.9m, the tunnel has a minimum plane curve radius of 1300m, and a maximum longitudinal slope of 29.6‰. Located in the central area of Shenzhen, the tunnel has the largest diameter among tunnels under construction in Shenzhen rail transit. It encounters complex geological conditions and sensitive environment. The proportion of composite strata exceeds 50%, and there is great risk arising from tunnelling along a very long section of existing expressway and metro lines. It is one of the most challenging and difficult TBM tunnels both at home and abroad. The construction started in 2021 and is expected to be completed in 2026.

Qianhai Integrated Transport Hub in Shenzhen (Large-scale Underground Integrated Transport Hub)

Qianhai Integrated Transport Hub is one of the very rare large transport hub TOD projects totally located underground in China. The transport hub involves three metro lines (Line No.1, 5 and 11), and two intercity railways (the Guangzhou-Dongguan- Shenzhen Intercity Rail and the Hong Kong-Shenzhen Western Rail). Occupying an area of 20 hectares, the project consists of two parts: the underground hub and the surface properties and has a floor area of approximately 2.159 million square metres. The project makes a full use of the underground space within the site. From east to west, there are the underground stations of Metro Lines No. 1, 5 and 11 and additional space; the underground hub interchange hall and the underground space for property development; the underground station of the Guangzhou-Dongguan-Shenzhen Intercity Rail; and the underground station and port space of the Hong Kong-Shenzhen Western Rail, containing a variety of composite functions such as traffic distribution and underground commerce, and maximising the intensive use of land resources.

The underground space of the project is a deep foundation pit project in near the sea, in which the hub interchange hall and underground space for property development is a 6-storey basement with a total length of 830m. The depth of the standard section of the basement is about 30m, and the deepest part of the tower and core tube is about 37m. To ensure the safe operation of the metro, the project is divided into 8 pits for interval excavation. The 32m deep adjacent foundation pit of the Guangzhou-Dongguan-Shenzhen Intercity Rail is constructed simultaneously. The construction of a super large scale deep foundation pit near the sea and metro is very complex and challenging in terms of safety protection and intersecting construction. The construction work started in 2011 and is expected to be completed in 2027.