Given the inherent risks associated with tunnel construction, various advanced techniques have emerged to enhance safety and efficiency. Nevertheless, advanced monitoring systems employing sensors and drones enable real-time data collection is essential, allowing for proactive risk management and early detection of potential hazards.
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1. Cut-and-Cover Tunnel Method
This approach involves the precasting or cast-in-place of the tunnel structure within an excavation. Once construction is complete, the structure is backfilled with excavated or newly-deposited soil. When the ground level of the tunnel is shallow, safe digging from the surface is feasible without compromising the integrity of the excavation walls, and it is both cost-effective and acceptable, cut-and-cover construction is implemented. This process is typically applied to the building of underpasses, approach portions of other tunnels, and tunnels with short depths or flat terrain.
2. Down the Hole Hammer
Through trenchless tunneling, down-the-hole hammers are designed to address the challenges posed by hard rock. There are instances when a horizontal directional drilling machine encounters a portion of rock that it is unable to penetrate. As mentioned, construction crews employ a down-the-hole hammer as an alternative to causing harm to drilling heads through excessive force and wear. Like a jackhammer, construction workers frequently observe this device on the side of the road to shatter concrete or road surfaces.
3. Pneumatic Pipe Ramming
Compressed air strength is utilized in pneumatic pipe ramming, which is used to push piping or pipe casings into the earth. In this method, the back of the pipe is struck with a series of blows from a rammer in succession. A sharp-edged soil-cutting shoe is affixed to the uppermost part of the pipe casing to facilitate soil penetration. It is occasionally necessary to apply a lubricant, such as bentonite, to help the pipe casings slide behind the cutting edge and cut through the dirt.
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4. New Austrian Tunnelling Method (NATM)
Rock tunneling is an application that is suitable for the NATM approach. The ground pressure is carried by the flexible lining utilized by this process. It transforms the load-bearing rock into the load-bearing rock. Because of this, the cost of the liner and its requirements have been reduced. NATM denotes the capacity of the lining to experience deformation. In response to the rock's deformation, flexible lining maintains touch with the rock and undergoes distortion. In addition, shotcrete, steel ribs, and wire mesh filled with boulders are a part of the flexible lining.
5. Clay Kicking Tunnel Construction
The clay kicking technique was devised for tunneling in complex clay layers in England. As part of the method, a clay kicker would lie on a plank slanted at 45 degrees and kick the clay they were working with. A digging implement is affixed to the soles of the clay-kicker. A cup-shaped end is attached to the digging instrument, and the clay-kicker inserts his feet into the clay while digging. After some time, the clay-kicker manipulates the cutting instrument by hand to remove the clay from the face. Following that, the remaining individuals are responsible for transporting the extracted clay.
6. Pipe Jacking Tunneling Method
When using the pipe jacking method, a circular shape with a diameter of up to 3.2 meters can be excavated. Hydraulic jacks drive a pipe into the ground, and the pipe's interior diameter equals the tunnel's cross-section. Because of this, the approach provides a convenient way to give lining and casing behind tunneling operations. Moreover, one of the tools for cutting the dirt is located at the front cross-section of the pipe. The cutting instrument makes a minor incision in the soil compared to the cross-section. This results in a decrease in the resistance of the conduit against the ground.
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