Tunnel boring machine

 Tunnel Boring Machine

A "mole" is known as a tunnel boring machine (TBM), through a variety of soil and rock strata with a circular cross-section is a machine used for digging tunnels. Through some hard rock to the sand can produce. 19.25 meter diameter tunnel to date (done with micro-TBMs) can reach one meter. Tunnels of less than one meter in diameter or trenchless construction methods generally horizontal directional drilling or instead is using TBMs.
Tunnel boring machines, drilling and blasting (D & B) in rocks and soil traditional "hand mining" as an alternative to the methods used. TBMs to limit disturbance to the surrounding ground and producing a smooth tunnel wall advantages. This significantly reduces the cost of lining the tunnel, and it makes it suitable for use in large urban areas. The main disadvantage is the cost. TBMs are expensive to build, and can be difficult to transport. However, as modern tunnels longer than drill and blast tunnel boring machines cost is actually lower. Tunneling with TBMs is much more efficient and shorten completion times because of the results.
19.25 meters in diameter, the largest TBM, (63 feet), Orlovski tunnel Herrenknecht AG, in St. Petersburg was built by a project. Machine to bore through soft ground including sand and clay was built for. Herrenknecht AG also built the world's largest diameter hard rock TBM excavation area :; 192 square meters, the thrust 39.485 T, a total weight of 4,500 tons, total installed capacity of 18 MW "Martina" (excavation diameter of 15.62 meters, total length 130 m, the annual energy consumption of 62,000,000 kWh) near Florence) Pass owned and Italian motorway A1 ("Variante di Valico A1" for the gallery Sparvo Costruzioni SpA in the Italian construction company Generali (the Group) is operated by.
The largest diameter hard rock TBM, 14.4 meters, Robbins Company for Canada's Niagara Tunnel Project was developed by. Niagara Falls hydroelectric tunnel boring machine was used below. The tunneling machine which is providing an additional hydropower tunnel Sir Adam Beck hydroelectric dams of the "Big Becky" was declared.
In 2013, Hitachi Zosen Corporation Highway 99 tunnel in Seattle for the project, an earth pressure balance TBM delivered to the United States. Bore 57.5 feet (17.45 meters).

Hard Rock TBMs

Hard rock, either shielded or open type TBMs can be used. Hard Rock TBMs cutter head installed in all types of rock excavation using the disc cutter. Disc cutter in front of the machine to chip away at the stone, which in turn, creates fractures in the rock compressive stress, called the tunnel face. Rock tunnel excavation known as muck, muck cars or conveyors for removal machine moves through a system where a belt conveyor, is transmitted through the hole in the head.
Rock TBMs type open rear area, leaving the field open for support, there is no shield. To further machine that pushes against the walls of the tunnel by a gripper system uses. Ungripped the only one who will drive the gripper shoes Wirth as in the case of the machine, while the machine continues to push the side walls can be diverted. Then the machine will push hard to get hold off. At the end of a stroke, the machine behind the legs are lowered and hold propel cylinders are retracted. Boring cycle to propel the cylinder retraction of the gripper assembly repositions. Hold the rear legs lifted, are extended, and begins boring again. When other machines as open type, or main beam, TBM do not install it behind the concrete segments. Instead, the ring beam like rock, rock bolts, shotcrete, and steel straps, color steel (2011 Pakistan Awami Tehreek) and wire mesh (Stack, 1995) as the support is held using methods .
In fractured rock, hard rock TBMs shielded behind the machine unstable tunnel segments erect concrete walls to support, which can be used. Double Shield TBMs are two modes; strengthening the grip against the tunnel walls can advance. Unstable, fractured ground, pressed against the back of the machine tunnel segments push the thrust cylinder is moved. The impact from the fragile walls of the tunnel is the main thrust forces. Single Shield TBMs work in the same way, but the only concrete classes (Stack, 1995), as can push off against, is only used in fractured ground.

Soft ground TBMs

Earth pressure balance machines (EPB), slurry shield (s) and open-face type soft ground, TBMs are three main types. Both types of machines shut off the concrete segments for further pushing forward thrust by using cylinders, Single Shield TBMs work. Earth pressure balance machines with 7 times less than the pressure used in soft ground. Not only does the disc cutter cutter head, but instead of tungsten carbide cutting bits, carbide cutters, disk, drag the picks and / or a combination of hard rock disc cutters. The face of the tunnel excavation material is used to balance the pressure gets its name because the EPB. Archimedes screw spoil pressure through the extraction rate and the advance rate is maintained by controlling the cutterhead. Such as bentonite, polymers and additives such as foam to increase the stability of the ground ahead of the face can be injected.
Archimedes screw too much water pressure or a plug-in can not be set so high so that granular soil conditions (sand and gravels) are, with slurry shield TBMs need soft ground. cutterhead hydrostatic pressure which applies pressure on the excavation face is filled with slurry. Usually the slurry out of the tunnel, a slurry separation plant before being pumped back to the cutterhead out of material excavated by mixing as a means of transport works. Slurry separation plants that can be reused in the construction process so that the slurry particles away from the spoil of a multi-stage filtration system,. Slurry 'cleared' the excavated materials which can be used depending on the particle size. Spoil slurry particle size was less than that of the bentonite clay as the reason, slurry TBMs silts and clays are suitable for. In this case, the slurry can be recycled water, and water is pressed from the mud pie, divided into.
Open face being dug into the soft ground TBMs face of the earth for a short period of time will stand with any support rely on the fact that - so with a strength of up to 10MPa or for use in rock types makes them suitable, and with low water flows. In the face of more than 10 meters in size, it can be excavated. 150MM face shield to the inside edge using a backactor arm or head is excavated. The shield on the front slope forwards and rigid circular shape is jacked off the ground. Sometimes the support of precast concrete, or SGI (spheroidal graphite iron) is provided by the use of, or close support has been built until a complete ring segments that are supported. A final segment, called key, wedge-shaped, and the TBM shield circular cut by the cutter against left until the ring expands. Many variations of this type of TBM exist.
TBMs use high pressure relieves the need for large numbers of workers, while sometimes slurry shield TBMs a caisson system is set up on the cutting head. [9] [10] inspection, maintenance and repair to the place of medical workers entering the "Dive" fit as approved and to be trained in the operation of the locks.

Backup Systems

Behind all types of tunnel boring machines, the completion of the tunnel in part, known as system backup support are trailing the deck. Located on backup support mechanisms may include: pre-cast segments of the transport conveyors or other systems to remove manure, slurry pipelines if applicable, control room, electrical systems, construction, ventilation and mechanisms.Urban tunneling and near-surface tunnel
The undisturbed ground level urban tunnel that particular need. This means it is necessary to avoid ground subsidence. Soft ground in the normal course of procedure and tunnel construction is to maintain the soil pressure. Especially in different segments, something difficult to do so (for example, the upper part of the tunnel face and wet sand bottom in a region where the boring through hard rock) is.
And millionaires such as the EPB control with positive face TBMs ,, used in such circumstances. Both types (EPB and SS) properly operated and if the ground conditions are well documented, so reducing the risk of surface subsidence and voids are capable of.
Tunnel in urban environments, the other tunnels, existing utility lines and deep foundations need to be addressed in the initial planning stages. Infrastructure projects for other measures to reduce any harmful effects must adjust.