What is TBM?

A tunnel boring machine (TBM), commonly referred to as a "mole," is a device that excavates circular tunnels through a range of soil and rock strata. They can be utilized for microtunneling as well. They can be made to pierce sand, wet or dry soil, or even solid rock. To date, tunnel diameters have ranged from 3.3 feet (one meter) (micro-TBMs) to 17.6 meters (58 feet). Instead of TBMs, tunnels with a diameter of less than or equal to one metre are normally built utilizing trenchless construction techniques or horizontal directional drilling. TBMs can be made to dig non-circular tunnels, such as u-shaped, horseshoe-shaped, square-shaped, or rectangular tunnels.

In place of traditional "manual mining" in soil and drilling and blasting (D&B) techniques in rock, tunnel boring machines are utilized. TBMs offer the advantages of minimizing ground disturbance and creating a smooth tunnel wall. This greatly lowers the cost of lining the tunnel and qualifies them for usage in populated areas. The initial expense is the main drawback. TBMs can be challenging to transport and are expensive to build. The relative cost of tunnel boring equipment against drill and blast techniques decreases with tunnel length. This is due to the fact that using the right TBMs makes tunneling significantly more productive and accelerates completion times. However, drilling and blasting continue to be the most effective technique when traversing severely fractured and sheared rock layers.

Advantages of TBMs for Tunneling

Tunnel boring machines are the best choice for use in densely populated regions since they minimize disruption in the excavation area. Additionally, they provide a smooth tunnel wall, which lowers the price of the finished lining. When compared to traditional excavation techniques, TBMs considerably shorten the overall excavation time of longer tunnels.

1. For the purpose of facilitating the work and advancement of the TBM, the injection of foams, polymers, and other additives into the tunnel face can drastically alter the properties of soft ground, including its flexibility, texture, and permeability. The exact geology and the equipment that the TBM can use depend on the optimal kind and amount of material to be used for this ground conditioning.

2. The main bearing is most likely one of the TBM's most crucial and expensive parts. This needs to be properly sealed and greased to maintain it in good shape. Experience has revealed that the majority of TBM main bearing failures are caused by lubrication loss or the intrusion of foreign impurities. Because of this, using dependable items in the system is vitally necessary.

3. Tail seal sealants are injected between the rows of brushes in the gap between the lining segments to prevent water, soil and the backfilling grout from entering the TBM.

4. A wide range of injection products which are used with TBMs for different applications, including soil consolidation, rock stabilization, stopping water ingress, permanent sealing and waterproofing, plus the filling of voids and cavities and more. Water ingress and wash-out with the development of uncontrolled cavities presents a security risk and potentially major costs for hard rock and gripper TBMs.

5. The tunneling and mining industries are amongst the largest industrial sectors in the world where rubber conveyor belt systems are widely used.

6. Excavation with shield TBMs means that precast concrete segments are installed to form the tunnel, and an annular gap remains between these segments and the ground. The filling of this annulus is a very important requirement, as this ensures homogeneous contact with the ground, transfers load from the TBM back-up and also can help to waterproof the tunnel.

7. One of the most important ingredients in high performance, long-lasting, durable and beautiful concrete produced today are concrete admixtures. Concrete admixtures are natural or manufactured chemicals or additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete, such as workability, durability, or early and final strength.