Mining or in situ disintegration of hard material – Hard material disintegrating machines – Stepper-type advance-causing means
Reexamination Certificate
2000-02-11
2002-08-13
Bagnell, David (Department: 3673)
Mining or in situ disintegration of hard material
Hard material disintegrating machines
Stepper-type advance-causing means
C299S033000, C405S141000
Reexamination Certificate
active
06431653
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tunnel rock drill of the type for driving a tunnel bore optionally in open or shielded mode, and also relates to a process for driving a tunnel bore, during which process the work varies from open to shielded mode, depending on the rock surrounding the tunnel bore.
When introducing tunnel bores, it is known to apply, for example, alternatingly the two following methods, depending on the nature of the soil.
a) In the so-called open mode there is free space behind the drill head. That is, the bore wall is not covered by any components of the apparatus, such as safety guards and the like. During the boring process support systems, such as steel rings, roof bolters and/or gunite linings, can be installed into this free space. In the region, in which the desired support systems are already installed, there is a bracing device, which can be braced, for example, radially, against the outer tunnel surface in order to divert the reaction forces, which are usually transferred by the drill head over a plurality of advancement cylinders, into the rock adjacent to the tunnel bore.
Since there are no burial structures or standing supports directly behind the drill head in open mode, this process is only appropriate for introducing tunnel bores in stable formations, where there is no risk that the unsupported section of the tunnel bore will collapse.
b) In the so-called shielded mode the drill head shield, which is usually provided behind the rotating part of the drill head, exhibits a so-called shield tail, whose outside diameter—depending on the rock's angle of convergence—is chosen somewhat smaller than the actual outside diameter of the drill head or also tapering conically toward the rear. The shield tail serves to brace the tunnel wall directly adjacent to the drill head room in order to prevent said wall from collapsing.
During the drilling process in the shielded mode a tubbing support is made inside the region covering the shield tail so as to leave space at the inside shell of the shield tail by assembling usually individual prefabricated concrete components with suitable aids into a tubular support that covers the entire tunnel wall. Since the shield tail and the tubbing support always overlap a certain amount over the longitudinal stretch of the tunnel bore, a collapsing of the tunnel wall is ruled out. Thus, the shielded method is suitable especially for introducing tunnel bores into soft rock or less stable formations.
In the shielded mode the tunnel work is done with so-called tubbing cylinders, which are provided between the (non-rotated) drill head shield and the front side of the tubbing support facing the longitudinal stretch of the bore. Hence reaction forces from tunneling and rotation pass into the tubbing support, or at the start of the shielded operation, i.e. when there is still no tubbing support, said forces pass into a steel ring, which is braced radially against the rock.
Especially in the case of longer tunnel bores these holes often extend through different rock formations, with the result that both methods have to be applied alternatingly. In this case it is well-known, as a function of the respective rock formations, to transport to the breast and to set up there different devices that are appropriate for the application of the respective method. This procedure is disadvantageous since the mandatory assembly and disassembly of both devices are time-consuming and thus the production costs of boring are significantly increased.
There exists a tunnel rock drill of this class that is made by the Wirth company in Erkelenz. It is suitable not only for use in hard rock but also in soft rock formations. That is, it works, as desired, according to the open method or according to the shielded method. This device comprises a shield tail, which always covers the tunnel space directly behind the drill head shield and which comprises two shield tail segments that mate telescopically. The telescopic overlapping of the shield tail segments takes place over a length that is greater than the maximum stroke of a plurality of advancement cylinders, provided inside the shield tail so that, irrespective of the operating state, the bore wall is completely covered by the shield tail in this region.
The advancement cylinders extend between the rear wall of the drill head shield and a bracing device, which can be braced—as stated above—radially against the bore wall in order to absorb the drill reaction forces, to the extent that the properties of the rock formation allow this.
In order to apply the device in the shielded mode, the bracing device has tubbing cylinders that are distributed over the circumference of the bore and that face the rear with respect to the direction of boring. Said tubbing cylinders are appropriate for bracing in the aforementioned manner against an already completed tubbing support or an installed steel ring and thus to transfer the boring reaction forces into the tubbing support when the bracing device is released.
If this tunnel rock drill is used in hard rock, the tubbing cylinders are inactive, while the bracing device is braced against the tunnel wall in order to absorb the reaction forces. The drill head advances by extending the advancement cylinders; during this advancing procedure the telescopic shield tail is simultaneously advanced. If the tunnel bore, which is advanced in this manner and by appropriately installing the bracing device afterwards, comes upon soft rock formations, the bracing device is deactivated, and the drill reaction forces are diverted in the manner already described over the tubbing cylinders into the tubbing support.
Of course, this device can also be used to drive the tunnel bore in alternating rock formations without the need of the time-consuming, complete retrofitting of the tunnel rock drill. However, the drawback is that, since the telescopic shield tail is always extended during the boring operation, significant lengths of the tunnel bore area adjacent to the drill head room are covered by the shield tail. Thus, on the one hand, it is not possible to install the desired support systems in the tunnel wall directly next to the drill head room in the case of hard rock; on the other hand, the length of the shield tail prevents any changes in direction. Furthermore, owing to its telescopic design the shield tail exhibits a recess, into which material, collapsing from the tunnel mantle, can penetrate and prevent the shield from being extended and thus prevent or even block the advancement. This is especially problematic when rock formations, which have a tendency to converge, necessitate the use of a shield tail that converges conically toward the rear.
SUMMARY OF THE INVENTION
The invention is based on the problem of improving to such an extent a tunnel rock drill of this class that is appropriate for both the open and the shielded mode and thus for driving the tunnel bore in both hard rock and soft rock formations that these drawbacks are remedied.
The problem is solved by a tunnel rock drill comprising a drill head; a shield tail, which is connected to the drill head and which covers optionally at least in part the bore wall over a defined length; a bracing device, which can be optionally fixed in the tunnel bore and which serves to divert the reaction forces generated by the boring process; at least one optionally activatable advancement device, which, on the one hand, rests on the bracing device, and, on the other hand, acts on the drill head in order to drive the drill head with advancing forces in the open mode; at least one optionally activatable force generator, which has a variable length and which, on the one hand, rests on the tubbing support or an abutment for the tubbing support and, on the other hand, acts on the drill head in order to drive the drill head with advancement forces in shielded mode; and an inner kelly, which can be moved in the direction of boring in relation to the bracing device and whose breast-sided end bears the drill head, and by
Bagnell David
Foley & Lardner
Singh Sunil
Wirth Maschinen- und Bohrgeräte-Fabrik GmbH
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