The tunnel construction is an essential discipline in civil engineering, especially when subway works are required without altering the surface environment. Trenchless tunnels have revolutionized the way these projects are executed, allowing subway boreholes to be drilled without the need for open excavation. In this article, we will delve into what these tunnels are, how they are executed, their applications and benefits, and how they are integrated into large-scale projects.
What is a trenchless tunnel?
A trenchless tunnel is a type of subway construction in which the ground is bored without the need to open large trenches on the surface. Unlike traditional methods, in which the ground is excavated to install pipes or cables, trenchless tunnels allow these interventions to be carried out cleaner, faster and without generating major disruptions to the surrounding areas.
These tunnels are constructed using advanced equipment such as tunnel boring machines y horizontal directional drills. These machines are capable of excavating the ground without significant surface disturbance, making them an ideal choice for urban areas and other areas where trenching would be complex and costly.
How is a trenchless tunnel executed?
The execution of a trenchless tunnel requires a meticulous approach and the use of state-of-the-art machinery. The following are the main methods used in trenchless tunnel construction:
Horizontal Directional Drilling (PHD)
The horizontal directional drilling (PHD) is one of the most popular methods for trenchless tunneling. This process uses a boring machine that excavates through the ground in a controlled and directed manner. The machine can be guided along a specific trajectory to traverse the ground and perform the necessary interventions.
The main advantage of this method is its precision, which allows the installation of subway infrastructure such as pipelines or cables without affecting overhead surfaces. PHD is ideal for crossing roads, rivers or any other existing infrastructure without interrupting the normal flow of traffic or activities.
Microtunnels
The microtunnels are a smaller, more specialized technique used for smaller scale projects. These tunnels are ideal for jobs that require smaller diameter boring, such as the installation of sewer systems, telecommunications networks or small drainage infrastructure. The main difference with other tunneling methods is the size of the machine and the accuracy of the cut, which allows more detailed control over the progress of the excavation.
The use of microtunnels is expanding due to its ability to operate in densely urbanized areas without causing major inconvenience to the daily lives of residents or traffic in the area.
3. Tunnel Lining
Once the tunnel has been excavated, it is necessary to install a lining to ensure the stability and durability of the structure. The materials used may vary according to the type of terrain and the nature of the project, but the following are commonly used voussoirs (precast concrete blocks) to form the tunnel walls.
The lining ensures that the tunnel does not collapse during or after boring. In some larger projects, such as the sewer tunnels or those intended for submarine emissariesadditional reinforcement system can be used, such as the use of steel rings or special concrete coatings.
4. Real Time Monitoring
One of the most important features in trenchless tunnel construction is the continuous monitoring. Throughout the process, advanced monitoring systems are used to ensure that the tunnel follows the planned path and that no deviations or geotechnical problems occur. These monitoring systems may include pressure sensors, inspection chambers y geotechnical control systems to ensure the stability of the project.
Benefits of trenchless tunnels
The trenchless tunnels offer a wide range of benefits that make them especially attractive for urban and large-scale projects. Some of the key benefits include:
Reduced impact on the environment
By avoiding the need to excavate large trenches, trenchless tunnels have much less impact on the environment. Not only is the surface preserved, but the amount of debris and waste generated during construction is also reduced. In addition, by not disrupting traffic or the daily lives of residents, inconvenience to the community is minimized.
2. Faster execution
The projects of trenchless tunnels are often faster than traditional ones due to the precision and efficiency of the machines used. This time saving is crucial in projects where construction time must be reduced to avoid problems such as traffic congestion or increased operating costs.
3. Reduction of operating costs
Since open excavation is not required, the infrastructure replacement costs The cost of construction of roads, sidewalks, and other utilities is significantly lower. In addition, the shorter working time means savings in labor and in the use of construction materials.
4. Better adaptability to urban areas
The possibility of drilling these boreholes without affecting the surface areas makes them the ideal choice for projects of infrastructure in densely populated urban areas. This is especially important when services are to be installed under floors already occupied by other infrastructures, such as drinking water, gas, electricity, etc.
Trenchless tunnel applications
The trenchless tunnels are ideal for a variety of applications including:
- Sewage and subway drainage networks. Drainage projects in urban areas can greatly benefit from this method to avoid disturbing existing infrastructure.
- Installation of telecommunication cables. The trenchless tunnel allows cables to be installed without having to cut streets or interrupt access.
- Water supply projects. Pipelines for potable water supply can be installed without affecting traffic or public areas.
- Subsea outfalls. These types of projects also benefit from the horizontal directional drillingThe pipelines or conduits can be brought to the seabed without complicated excavations.
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