Road and Bridge Construction and Municipal Construction Projects Become the Two Demands for Shield Machines

At present, our country is in a period of rapid development, and the construction of infrastructure such as railways, highways, hydropower, municipalities, and related pipelines is vigorous, and the construction of tunnels and underground works has been greatly improved in both scale and number compared with the past. A considerable portion of these tunnels will be constructed using advanced shield methods.

In terms of railway construction, it is conservatively estimated that the length of the new railway tunnel will reach 300-400 km in the next 10 years. In terms of highway construction, the density of highways in China is now more than 10 times that of the developed countries in the world. It requires a lot of construction to meet the economic needs of China's rapid development. With regard to the construction of urban rail transit, China has only just begun its development and the length of its completed line is only 100 kilometers. According to the relevant research, it is predicted that in the early 21st century, there will be about 20 to 30 cities in China that can own rail transit.

The construction of hard tunnel boring machines is mainly used in railway tunnels, and shield tunnelling machines are mainly used in urban subways and municipal water transmission pipelines. Roads and hydropower tunnels are constructed using hard rock boring machine or shield machine according to geological conditions.

Especially in the construction of urban subways, the application ratio will continue to increase as shield machine construction can solve problems such as environmental pollution, land subsidence, ground transportation, groundwater, and deeper tunnel depth. For example, the subway lines that have been built in Shanghai and several cross-river tunnels through the Huangpu River are all constructed with shield machines. The tunnels of Guangzhou, Shenzhen, Nanjing, and Beijing Metro Line 5 have also been used or are planned to be constructed using shield machines. The number of Shield machines used in the above subway projects has reached about 15 at present, most of which are earth pressure balanced shields, and individual lines adopt hybrid shields or mud shields. In order to estimate the scale and quantity of subway construction in each city in China in the coming period, if 30% is constructed by using the shield method, about 40 to 50 shield machines will be needed.

Urban municipal engineering has gradually begun to adopt technology constructions such as non-excavation and tunnel excavation that have less impact on the environment. In particular, for some tunnels with relatively large sections, undercutting techniques have been widely used. According to conservative estimates, the number of city tunnels constructed by underground excavation in China will be no less than 100 kilometers per year and the number of shield machines will exceed 10.

Hydro-electric tunnels have been more widely used in construction of tunnel boring machines. Most of the projects that have been built use hard rock boring machines, such as the Qin Dao Qin and the Yellow River Jinjin tunnel projects. A part of the diversion tunnel at the Zhangdu River in Kunming will also be constructed using a roadheader. The South Yellow Water Diversion Project will use a large-scale slurry shield construction.

At present, hard rock boring machine or shield machine for soft ground used in tunnel construction in various industries in China is basically dependent on foreign imports, and a small part is manufactured by domestic cooperation. Considering that the tunnel boring machine is expensive and the demand in China is very large, it is recommended that domestic enterprises with basic strengths and strength be able to manufacture localized tunnel boring machines as early as possible through the combination of independent development and introduction of technology under the unified coordination of the country.