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CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Phase Patent Application based on International Application Serial No. PCT/EP2013/070839 filed Oct. 7, 2013, the disclosure of which is hereby explicitly incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for conveying excavated material away during tunneling. 
     2. Description of the Related Art 
     Such a method and device are known from DE 197 00 297 C2. The prior device and method for conveying excavated material away during tunneling involve a conveying system comprising a screw conveyor unit disposed in a jacket. The jacket is provided with a first opening, at the working-chamber end, and a second opening, remote from the working chamber. The openings are opened and closed by means of selectively operable seals. A system for airlocking excavated material out is also present, and is adapted to maintain a counterpressure in the jacket. In tunneling using slurry conveyance, the first opening, at the working chamber end, is open, the second opening, remote from the working chamber, is closed and the airlock discharge system is not operating. In earth pressure balance tunneling, the first opening, at the working chamber end, and the second opening, remote from the working chamber, are closed, whereas the airlock discharge system is operating. In open tunneling, the first opening, at the working chamber end, is closed, the second opening, remote from the working chamber, is open and the airlock discharge system is not operating. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and a device for conveying excavated material away during tunneling that are distinguished by failure-resistant and low-wear operation. 
     By virtue of the fact that according to the invention, in the case of the method, in unpressurized open tunneling or in earth pressure balance tunneling excavated material is discharged from a first opening, disposed first in the direction of conveyance, and in the case of the device, in order to deactivate the system fluid-mechanically a second opening located downstream of the first opening in the direction of conveyance is deactivated, a manner of operation is obtained that is relatively failure-resistant and low-wear, since this abrasive excavated material is discharged early. 
     In one form thereof, the present invention provides method for conveying excavated material away during tunneling, wherein, in an open tunneling operation or in an earth pressure balance tunneling operation, a first opening, disposed first in the direction of conveyance, of a conveying system is open and a second opening, downstream of the first opening, is closed, and in a slurry tunneling operation the first opening is closed and the second opening is open. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       Therein: 
         FIG. 1  is a descriptive side view of an exemplary embodiment of a device according to the invention, comprising a tunnel boring machine engaged in earth pressure balance tunneling; 
         FIG. 2  shows the exemplary embodiment according to  FIG. 1  in a sectional view along line II-II; 
         FIG. 3  is a descriptive side view of the exemplary embodiment according to  FIG. 1  engaged in slurry tunneling; 
         FIG. 4  shows the exemplary embodiment according to  FIG. 3  in a sectional view along line IV-IV; 
         FIG. 5  is a descriptive side view of a variant of the exemplary embodiment according to  FIG. 1 ; 
         FIG. 6  shows the exemplary embodiment according to  FIG. 5  in a sectional view along line VI-VI; 
         FIG. 7  is a descriptive side view of the exemplary embodiment according to  FIG. 5  engaged in slurry tunneling; 
         FIG. 8  is a descriptive side view of the exemplary embodiment according to  FIG. 5  in a discontinuous airlock discharge mode in a first operating state; and 
         FIG. 9  is a descriptive side view of the exemplary embodiment according to  FIG. 5  in the discontinuous airlock discharge mode in a second operating state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a descriptive side view of a tunnel boring machine equipped with an exemplary embodiment of a device according to the invention for conveying excavated material away and operated according to the method of the invention. The tunnel boring machine according to  FIG. 1  comprises a cutting wheel  2 , which is fitted with excavation tools  1  and is drivable in rotation by means of a cutting wheel drive  3 . A working chamber  4  located behind the cutting wheel  2  in a tunneling direction, in the case of the earth pressure balance tunneling illustrated in  FIG. 1 , also known as EPB mode, is filled with excavated material to be removed and is also filled with shield flushing liquid that is fed in as needed via a shield flushing liquid feed line  5  when a working chamber slide valve  6  is opened. 
     Also opening into the working chamber  4  is an overflow line  7 , which is in communication with a buffer chamber  8  surrounded by the cutting wheel drive  3 . The communication between the working chamber  4  and the buffer chamber  8  via the overflow line  7  is to be sealed or opened, as needed, by means of an overflow line slide valve  9 , to maintain pressure conditions in the working chamber  4  that are suitable for EPB mode. 
     Located in back of the working chamber  4  in the tunneling direction is an annular gap  10  into which a branch  11  of the shield flushing liquid feed line  5  opens, said branch  11  being sealable by means of an annular gap slide valve  12 . 
     The tunnel boring machine according to  FIG. 1  further comprises thrust cylinders  13 , which move the cutting wheel  2  and a shield  14  along in the tunneling direction by pushing against lining segments  15 . The lining segments  15  can, in turn, be installed by means of a lining segment feed unit  16  and a lining segment positioning unit  17  in order to line a tunnel wall. 
     The tunnel boring machine according to  FIG. 1  is equipped with a conveyor system  18 , as a device for conveying excavated material away, which in the exemplary embodiment depicted in  FIG. 1  has a main screw conveyor  19  that is formed with a core and surrounded by a main screw conveyor cladding tube  20  and that extends away from the cutting wheel  2 , in the opposite direction from the tunneling direction, from an open end projecting into the working chamber  4  and encapsulatedly on through the annular gap  10 . The main screw conveyor  19  is drivable in rotation in two rotational directions by means of a main screw conveyor drive  21 , in one of which directions of rotational conveyance, excavated material present in the working chamber  4 , together with, in particular, shield flushing liquid fed in through the shield flushing liquid feed line  5  and any desired further inputs from the working chamber  4 , can be conveyed away in the opposite direction from the tunneling direction. 
     Located at the end of the main screw conveyor cladding tube  20  remote from the working chamber  4  is a main screw conveyor outlet  22 , which is provided as a first, working-chamber-end opening in the main screw conveyor cladding tube  20  and which can selectively be sealed by means of a main screw conveyor outlet sealing slide valve  23  as a first seal. Disposed in the ejection direction of the main screw conveyor outlet  22  is a transverse conveyor belt  24 , by means of which material containing extracted material emerging from the main screw conveyor outlet  22  and intended for removal can be transported away transversely to the tunneling direction and transferred to a backup conveyor belt  25  which conveys material oppositely to the tunneling direction, but which can also be moved, together with a backup system  26 , in the tunneling direction. 
     It is also apparent from the representation according to  FIG. 1  that the main screw conveyor cladding tube  20  is sealed behind the main screw conveyor outlet  22  by means of a transitional-opening throughpass slide valve  27 , as a second seal, by means of which a transitional-opening throughpass  28  formed by the cross section of the main screw conveyor cladding tube  20  and provided as a second opening can be sealed, thereby fluid-mechanically deactivating a downstream screw conveyor cladding tube  29  adjoining the main screw conveyor cladding tube  20  in the conveying direction and containing a downstream screw conveyor  31 , which is also a component of the conveyor system  18  and which can be rotated by means of a downstream screw conveyor drive  30 . 
     The downstream screw conveyor cladding tube  29  opens, by its end remote from the main screw conveyor cladding tube  20 , via a downstream screw conveyor outlet  32  into a flushing chamber  34  that is enclosed by a flushing box  33  and is part of a removal unit into which flushing-box flushing-liquid feed lines  35  open that can be supplied with flushing liquid. Disposed in the flushing box  33  is a jaw crusher  36 , by means of which, as will be described in more detail below, coarse components conveyed into the flushing box  33  can be made smaller. Opening into a floor region of the flushing box  33  is a delivery line suction pipe  37  that is part of the removal unit and is connected to a feed pump  38  of the removal unit, and by means of which material conveyed into the flushing box  33  and containing components of relatively low viscosity and only relatively small particle size can be sucked out of the flushing box  33 . By means of the feed pump  38 , which can be driven via a feed pump drive  39 , relatively low-viscosity material in the flushing chamber  34  can be transported to a discharge line arrangement  40  of the removal unit. 
       FIG. 2  shows the exemplary embodiment according to  FIG. 1  in a sectional view along line II-II, looking in the tunneling direction. It can be seen from  FIG. 2  that owing to the arrangement of the transverse conveyor belt  24  crosswise to the tunneling direction or removal direction, a clearance is created under the main screw conveyor cladding tube  20 . 
       FIG. 3  is a descriptive side view of the arrangement according to  FIG. 1  engaged in slurry tunneling, in which, on the one hand, the working chamber slide valve  6 , the overflow line slide valve  9  and the annular gap slide valve  12  are open in order to maintain the slurry feed necessary for slurry tunneling and the corresponding pressure conditions in the working chamber  4  and the buffer chamber  8 . On the other hand, in slurry tunneling the main screw conveyor outlet sealing slide valves  23  are closed and the transitional-opening throughpass slide valve  27  is open, and consequently the transitional-opening throughpass  28  located between the main screw conveyor cladding tube  20  and the downstream screw conveyor cladding tube  29  is now open and material containing excavated material destined for removal and conveyed by the main screw conveyor  19  can be conveyed into the downstream screw conveyor cladding tube  29  and, by means of the downstream screw conveyor  31  rotating in a conveying direction, can be carried on through the downstream screw conveyor outlet  32  into the flushing chamber  34  surrounded by the flushing box  33 . In the flushing chamber  34 , in slurry tunneling, as indicated schematically by the arrows in  FIG. 3 , flushing liquid can be introduced into the flushing chamber  34  through the flushing-chamber flushing-liquid feed lines  35  to lend the material for removal a suitable consistency for the operating parameters of the feed pump  38 . 
       FIG. 4  shows the arrangement according to  FIG. 3  in a sectional view along line IV-IV. Particularly apparent in  FIG. 4  is the configuration of the jaw crusher  36 , with crusher jaws  42  that are operable via pressure cylinders  41  and by means of which the material in the flushing chamber  34 , which can include relatively large-size components, can be reduced in size sufficiently to pass through a screen  43  disposed in front of the feed line suction pipe  37 . 
       FIG. 5  is a descriptive side view of a modification of the exemplary embodiment described with reference to  FIGS. 1 to 4 , it being noted that like elements of the exemplary embodiment according to  FIGS. 1 to 4  and the modification according to  FIG. 5  have been given the same reference numerals and that, to avoid repetition, some of them will not be described again in greater detail. In the modification according to  FIG. 5 , for EPB mode, the transverse conveyor belt  24  and the backup conveyor belt  25  are positioned in the region of a downstream screw conveyor outlet sealing slide valve  44  that is disposed at the downstream screw conveyor outlet  32  and is open in this mode of operation; in contrast to the exemplary embodiment according to  FIGS. 1 to 4 , here the flushing box  33  and the feed pump  38  have been removed. In addition, in the modification according to  FIG. 5 , provided in the region of the downstream screw conveyor cladding tube  29  and the downstream screw conveyor  31  is a drip pan  45  that rests on the backup system  26 . 
       FIG. 6  shows the modification according to  FIG. 5  in a sectional view along line VI-VI, looking in the tunneling direction. It can be seen from  FIG. 6  that, as in the exemplary embodiment according to  FIG. 2 , material emerging from the downstream screw conveyor outlet  32  over the drip pan  45  is carried off via the transverse conveyor belt  24  and the backup conveyor belt  25 . 
       FIG. 7  is a descriptive side view of the modification described above with reference to  FIGS. 5 and 6 , but in which, for the slurry tunneling operation depicted in  FIG. 7 , a drum crusher  46  is disposed at the downstream screw conveyor outlet  32  to reduce the size of the material conveyed via the main screw conveyor  19  and the downstream screw conveyor  31  before it enters a removal line  47  and a feed pump  48 . 
       FIG. 8  shows the arrangement according to  FIG. 5  in a discontinuous airlock discharge mode in a first operating state, wherein, starting with earth pressure balance tunneling or open tunneling to get through a relatively short region where, for example, there is a high afflux of water or high pressure during tunneling, the transitional-opening throughpass slide valve  27  is open and the downstream screw conveyor outlet  32  is closed, so the downstream screw conveyor cladding tube  29  is filled during tunneling. 
       FIG. 9  shows the arrangement according to  FIG. 5  in the discontinuous airlock discharge mode in a second operating state, wherein, with no tunneling taking place, the transitional-opening throughpass slide valve  27  is closed and the downstream screw conveyor outlet  32  is open, so that the contents of the downstream screw conveyor cladding tube  29  can be removed via the transverse conveyor belt  24  and the backup conveyor belt  25 . The system then returns to the first operating state of the discontinuous airlock discharge mode illustrated in  FIG. 8 , and the alternation between operating states in discontinuous airlock discharge mode continues until the critical region has been discontinuously traversed. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Summary:
A method and device for transporting overburden away during tunneling includes a seal that separates a first portion and a second portion of a transporting screw arrangement. As a result, in open tunneling or in earth-pressure-assisted tunneling, when the seal is closed, overburden can be transported out of a first opening, arranged ahead of the seal in the direction of removal and, in fluid-assisted tunneling, when the first opening is closed and the seal is open, the overburden can be transported into the second portion.