Why build tunnels? Why are tunnels built on highways?

Since ancient times, building roads and bridges has been seen as a measure for the benefit of the people. In modern society, roads and bridges are also considered to be the foundation of economic development, and they are as important as the blood vessels in a person. However, when people build roads or railways, they will inevitably encounter obstacles from mountains and rivers.

In the case that the traditional "opening roads in the mountains and building bridges in the water" are difficult to implement, the construction of tunnels may be the most practical and effective method. A railway or road tunnel through a mountain is much simpler than a winding railway or road; And when the sea blocks the way and it is inconvenient to build a bridge, the undersea tunnel is like the magic of Sun Wukong to go to the sky and the earth, so that we can reach the other side smoothly.

In addition, the tunnel has many functions, such as tunnels for underground drainage or water supply in cities, tunnels for laying gas pipelines or large power transmission lines, subway tunnels, water diversion tunnels for agricultural irrigation, and special tunnels for national defense and military purposes. The opening of the undersea tunnel was once a fantasy, but today it has become a reality and is working day and night to serve humanity. For example, the 50-kilometre-long undersea tunnel through the English Channel passes through chalk rocks at a depth of 40 metres under the seabed.

The diameter of the tunnel is 73 meters, built with two railways.

Construction of the Channel Tunnel began in July 1987 and was completed in 1993, making it one of the largest civil engineering projects in Europe. The opening of this tunnel shortened the time from Paris to London by train to three hours, and played an important role in the economic development of Europe, especially Britain and France. The longest submarine tunnel in the world has been built is the Seikan Tunnel in Japan.

It crosses the Tsugaru Strait in Japan and connects the main island of Japan with Hokkaido. It has a total length of 5385 kilometers, the deepest point is 240 meters above the sea surface, and the inner diameter of the tunnel is 9

6 meters, it can open one high-speed train and one ordinary train. The entire project cost $4.5 billion and was built by more than 10 million people. At the same time, the project has also won 19 patented technology awards and set a number of world engineering records.

The construction of tunnels can reduce the distance traveled by vehicles and the cost of road construction, and shorten the distance of roads and railways. Reducing travel time, thereby increasing passenger traffic and developing the transport network. The highway has high requirements for plane alignment and longitudinal slope.

If tunnels are not used in mountainous areas, the amount of earthwork is often large and the ecological environment is damaged. Therefore, roads often require tunnels in mountainous areas. A tunnel is an engineering building buried in the ground and is a form of human use of underground space.

Tunnels can be divided into traffic tunnels, hydraulic tunnels, municipal tunnels, and mine tunnels. International Organization for Economic Cooperation and Development, 1970.

The tunnel conference was held to combine various factors and define a tunnel as "a cavern with a cross-sectional area greater than 2 of the prescribed shape and size for any purpose and by any method of acting under the ground." ”<

Not only highways, but also high-grade roads, such as first-class roads, are often built with tunnels.

Highways are for transportation, and the high speed of the design will be the high efficiency of transportation. When the vehicle is driving at high speed, it has high requirements for the shape of the route, such as no sharp bends, steep slopes, etc., and in order to keep such a line smooth, when encountering a mountain range, choose to pass through, rather than bypassing, and it is necessary to build a tunnel through it. If you choose to bypass, then the route needs to avoid all the mountains, which is almost impossible to achieve in the mountains, even in areas with fewer mountains, in order to bypass the mountains, the route will be very long, the construction cost is very high, the mileage is also very long, the transportation cost is very high, and it is not economical.

The cost of tunnels is very high, and the construction of tunnels on highways increases the cost of highways, and the corresponding tolls will be very high.

But there are some of them, reducing winding roads, reducing road mileage, and saving fuel.

Highway tunnels use shield as the construction method of construction tools, and are often used in tunnel construction with circular sections in soft soil. The shell of the shield is a cylindrical metal structure, the front part is the incision ring of the device excavation equipment, the middle part is the supporting ring of the device propulsion equipment (jack), and the tail part is the shield tail covering the assembly lining work. The shield method excavates the stratum in the front, assembles the lining at the tail at the same time, and then uses a jack to resist the assembled lining to advance the shield, and so on alternately and step forward.

There are many types of shields, "bentonite mud shield" is in a leading position, the use of mud wall protection and as a medium to carry waste ballast, no need to use compressed air that damages the health of workers during work, only need to use water or "mud milk" as the supporting agent of the face of the tunnel.

1. What is a tunnel?

Tunnels are artificially excavated underground passages, which are often used in construction fields such as roads, railways, subways, and mines. The advantage of the tunnel is that it can directly pass through obstacles, shorten the distance, reduce the difficulty of construction, and improve traffic efficiency.

2. Why build tunnels?

There are many reasons for the construction of tunnels, mainly the following:

1) Complex terrain: the terrain conditions such as steep mountains, turbulent water flows, and staggered rivers make it very difficult to build road surfaces, while tunnels can directly pass through mountains and water flows, making the route more convenient;

2) Environmental protection requirements: The traditional construction of roads and railways not only needs to level the land, but also usually needs to cut down large areas of forest, causing environmental damage. Tunnels can protect the environment to the greatest extent and do not damage natural resources;

3) Safety requirements: The tunnel can strengthen the mountains on both sides of the tunnel, so as to reduce the risk of natural disasters such as landslides, landslides, and debris flows to the building;

3. The technology and difficulty of tunnel construction.

The construction of tunnels requires the use of certain technical means, and the general steps are as follows:

1) Planning and design: scientific and reasonable planning and design according to the actual terrain and environmental conditions;

2) Land acquisition: purchase the required land to ensure the effectiveness and safety of construction;

3) Selection of drilling equipment: tunnel construction needs to strictly control the direction and depth, so it is necessary to purchase suitable drilling equipment;

4) Master the geological characteristics: the geological conditions of tunnel construction are very important, and different geological conditions need to adopt different construction methods;

5) Construction management: The tunnel construction should achieve the stability, timely management and smooth coordination of the construction management team, and carry out construction quality control in strict accordance with the inspection and acceptance of the VCR project and the construction progress.

4. Influencing factors of tunnel construction.

There are many influencing factors for the construction of tunnels, including topography, mining area, hydrology, permeability, freeze-thaw, physical mechanics and other factors.

In the process of tunnel construction, if there is no scientific and reasonable consideration and planning, it will cause a series of adverse consequences, such as poor excavation quality, tunnel erosion, etc.

5. Prospects for tunnel construction.

With the acceleration of the country's economic development, the demand for transportation is also growing, and the much-anticipated "Belt and Road" will build new land-sea roads, which highlights the importance of building tunnels. In the future, the direction of tunnel construction will be more extensive and diversified, and it is necessary to realize the high-quality realization of various constructions such as subway network and intercity highway in the process of urbanization, and at the same time, the protection and environmental protection function of the tunnel and the reduction of the impact on the original ecological life are also more and more important.

1.Tunnels are generally divided into excavation, support, lining and other processes, which are described in detail according to the following processes.

2.Excavation: The common excavation method of the tunnel is the blasting method.

Tunnel excavation is a project to break up soil or rock, excavate and transport ballast. The cross partition method is suitable for the long-span tunnel with weak surrounding rock, first excavate one or two parts of one side of the tunnel, apply part of the partition wall and the diaphragm, and then excavate the part of one or two on the other side of the tunnel to complete the transverse partition construction.

3.Support: The big tremor support is used as a temporary protection project for excavation, and the part of the poor geology or has a certain risk is supported, and the support is generally in the form of I-beam arch or reinforced concrete.

4.Lining: Lining is to pour concrete for the tunnel that has been excavated, including arch ring and bottom plate, etc., according to geological conditions, do not use, roll Chang and fail at the same time using backfill and consolidation grouting.

Legal basis

Nine Regulations on the Safety of Tunnel Construction

1. The licenses must be complete, and it is strictly forbidden to construct without qualifications, subcontract, illegal subcontracting, and personnel to work without education and training.

Second, the special construction plan must be prepared in accordance with the standard specifications and design requirements to ensure that the organization and implementation are carried out according to the plan, and it is strictly forbidden to change the construction method without authorization.

Third, the construction process and on-site management must be strengthened to ensure that the support (prevention) is in place, and it is strictly forbidden to lag behind the support and exceed the safety step distance.

Fourth, it is necessary to implement the provisions of advanced hydrogeological exploration and forecasting, and the monitoring (exploration) data exceeds the standard and immediately stop work and withdraw personnel, and it is strictly forbidden to take risks in construction operations.

5. Toxic and harmful gases must be monitored and monitored, ventilation management must be strengthened, and construction operations with excessive concentrations are strictly prohibited.

Sixth, the number of on-site workers must be strictly controlled, the excavation face should be mechanized, and it is strictly forbidden to organize construction operations with overcrowding.

7. Escape channels must be set up in accordance with regulations, and construction operations are strictly prohibited in the case of insufficient safety facilities.

8. It is necessary to strictly manage civil items in accordance with the regulations, and it is strictly forbidden to transport, store and use civil items in violation of regulations at the construction site.

9. Emergency plans must be formulated and rescue equipment must be equipped in accordance with regulations, and it is strictly forbidden to command and rescue in violation of regulations after an accident occurs.

01 The construction of tunnels is actually very complicated. First of all, before building the tunnel, we need to find the corresponding construction point, and the first step is to find the tunnel entrance to guide the construction wall.

02 After the construction of the guide wall, we need to seal the mold immediately, and then pour the concrete after the rough song, this step is very important, and it is also one of the most basic and important links in the construction of the tunnel.

03 Then we can further construction, you can choose manual or excavator for further construction, but if you want to quickly achieve the construction effect, you can also choose explosives, but you must survey the site in advance.

04 Moreover, during the construction of the tunnel, it is also necessary to pay attention to the construction of the cable trough and the ditch, because the tunnel will still be used in the later stage, so it is necessary to have both cable power supply and ditch drainage.