Hydraulic and earth engineering – Underground passageway – e.g. – tunnel – Boring
Reexamination Certificate
1997-05-28
2001-09-11
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Underground passageway, e.g., tunnel
Boring
C299S055000
Reexamination Certificate
active
06287052
ABSTRACT:
The present invention concerns the technical field of machines used to bore tunnels, commonly called “tunnel boring machines.”
It is known that these machines are capable of boring into subterranean formations, a tunnel whose diameter corresponds directly to the final diameter of the work to be performed, or essentially so. It naturally involves extremely powerful and complex machines whose operating constraints and requirements are in proportion to their design.
Among the constraints, we shall consider here in particular the problems associated with the attack of the underground formation by the boring tools. This naturally causes substantial wear on these tools, and it is understood that this is related to the hardness of the rock. Another related problem resides in the evacuation of the cuttings and the debris.
There is also a substantial wearing of the components used for evacuation of the debris, especially if it involves an endless screw or Archimedes screw, either on the screw or on its metal envelope, and often also on the tunnel machine skirt.
It will be recalled that there are two main types of tunnel boring machines: “bedrock” tunnel boring machines designed to attack terrains with a good deal of rock and the like, and “confinement” tunnel boring machines designed to operate on soil of ordinary content (alluvial soil, sand, clays) or wetlands.
By the nature of the soil tunneled, the latter boring machines are less severely confronted with wear problems. On the other hand, they can operate in an easily worked or liquid (water bearing) environment, and they contain a system which ensures imperviousness behind the boring machine head.
The acuteness of the wear problems will also be recalled. The boring machines are actually machines whose wearing parts are by definition very hard to access, whether it involves the screw, the tools and cutting wheels for boring, the front surface of the tunnel boring machine, or its lateral skirt. Moreover, when a wearing phenomenon makes it necessary to replace a part, it is necessary to stop the machine, and sometimes to move it back and partially dismantle it. These downtimes translate into enormous financial losses and any gain in matters of prolonging the service life of a part is immediately and very keenly felt.
prior art discloses injecting water or a watery fluid into the head of the tunnel boring machine. By known appropriate devices, this fluid is brought to the cutting tools and at this level is brought into contact with the formation to be bored.
This fluid fulfills a most classical dual function, which is to lubricate the contact zone between the cutting tool and the rock, on the one hand, and on the other hand to permit an easier evacuation of the cuttings in the form of a slurry loaded with debris, and to reduce the formation of dust.
However, this is only a palliative measure and the industry in question for many years has been confronted more frequently with increasingly more acute problems connected with the performance of the machines and the requirements of the users.
Foams have likewise been used comprised only of water and surface-active agent(s) (and a gas such as air) in the case of confinement boring machines. The purpose of the water foam is this case to fluidize the excavated material, to improve the permeability of the soil (which is possible precisely by virtue of the nature of the terrain encountered by this type of boring machine) and thus to reduce the torque applied to the machine.
This technique has been tried in rock tunneling machines and is ineffective, i.e., it does not provide substantial progress.
The use of lubricating systems has likewise been tried, also without significant results.
According to the invention, the problems described above are improved to a surprising degree.
According to the invention, into the head of the tunnel boring machine, not a water fluid or a water foam or lubricant, but a watery foam composition heavily loaded with clay(s) is injected.
This composition is injected in the form of a foam formed either upstream of the head of the boring machine, or in situ.
This results in an altogether unexpected reduction in wear as well as significantly easier extraction of the cuttings.
The clay foam composition also makes it possible to reduce greatly the volume of water necessary, which bears on the enormous volumes and thus has great impact on respecting the environment and, moreover, the processing of the excavated material in view of respecting the environment is easier, some excavated material not even needing to be treated.
Without wanting to be limited by any theory, it has been noted that the reduction of wear seems to derive essentially from the occurrence of coating of the rock fragments by a layer of composition according to the invention.
Thus, wear is reduced not only by lubrication or fluidization of the surrounding medium, but essentially by a new function which reduces the abrasive nature of the rock itself providing a radical solution to the wear problems.
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Basset Jean Marc
Hofmann Paul
Mansoux Jean Louis
Roman Philippe
Bagnell David
Bierman, Muserlian and Lucas
Condat S.A.
Kreck John
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