Tunnelling machine

Details Tunnelling machine Tunnelling machine

1993-08-08

1995-08-22

Bagnell, David J.

Mining or in situ disintegration of hard material

Hard material disintegrating machines

With mine roof-supporting means

299 58, 405141, E21D 908

Patent

active

054433053

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a tunnel driving or digging machine with a shield having a cylindrical case.
With machines of this type the shield is driven into the ground (rock, loose stone), the ground being excavated protected by the shield case in the front area thereof, on the so-called tunnel or working face. The rear extension of the shield case, also known as a shield tail, overlaps the already made tunnel lining, so that its construction can continue corresponding to the advance protected by the shield case.
The main problem occurring with this type of tunnel driving, particularly in a material only having a limited internal cohesion (such as e.g. loose rock), is that at the working face not only is material excavated, but at the same time the working face, so as to prevent settlement or even collapse against which the earth pressure must be supported. If there is also ground water in the soil, then the working face must simultaneously be protected against the ground water pressure. This is particularly critical in those cases in which a tunnel is being driven at a very limited depth, which can be smaller than its diameter, through material having virtually no cohesion, with or without ground water and under built-over ground.


PRIOR ART

For supporting the working face and simultaneously holding back the ground water use has hitherto been mainly made of the compressed air method, the hydroshield advance method or the membrane shield method (cf. "Tunnelbau", 1986 edition, pp 319 to 362 and 1987 edition, pp 103 to 139, published by the Deutsche Gesellschaft fur Erd- und Grundbau e.V., H. Eckard and P.M. Schnelzle: "Entwicklung des Membranschildverfahrens fur den hydraulischen Rohrvortrieb", TIS 19/88, pp 580-588).
In the compressed air method a working or excavation zone subject to the action of the compressed air is installed at the working face. The compressed air prevents the penetration of the ground water at the working face into said excavating zone. The compressed air method can only be used to a limited extent, i.e. only with certain building site conditions. For the support of the working face it is often necessary to have additional means, such as support plates pressed hydraulically against the working face. In the so-called bath system use is made of a drill head which simultaneously excavates and supports the working face. In the shield case only moving in the driving or advance direction the drill head performs a swinging rotary movement and is subdivided into movable, planar support plates and reversible, planar scraping plates covered with scraping blades or knives. Excavation takes place at the slots, which are obtained between the plates through the inclining thereof. It is generally disadvantageous in the compressed air method that working costs are high, work delays occur and there is a considerable risk of a collapse under heterogeneous building site conditions, whilst there is also a blow-out risk.
In the case of hydroshield driving the working face is supported by a supporting fluid, which is generally constituted by a bentonite suspension. The excavation zone is divided off upstream of the working face by a pressure wall from the rear shield and the already made tunnel, the excavation zone being subdivided by a breast wall into two communicating areas. The area upstream of the breast wall is completely filled with the supporting fluid, whereas the area behind it is only partly filled. Above the supporting fluid a plenum space, which is subject to pressure action is provided in the last-mentioned area. By regulating the air pressure, it is possible to regulate the pressure exerted by the supporting fluid on the working face. Excavation generally takes place by means of an opening cutting head in the supporting fluid. The excavated material is transported away with the supporting fluid by means of pump lines. The "consumed" bentonite leads to considerable costs. Due to the high cost of bentonite it is well worth separating it for reuse from the excavated ma

REFERENCES:
patent: 4456305 (1984-06-01), Yoshikawa
Tunnelbau, 1986 edition, pp. 319 to 362 and 1987 edition, pp. 103 to 139, published by the Deutsche Gesellschaft fur Erd-und Grunbau e.V.

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