Abstract:
Disclosed is a tunnel excavating apparatus for excavating tunnels in earth. This tunnel excavating apparatus comprises shell bodies, an excavating mechanism disposed on front of the excavating portion shell body, and a propelling mechanism disposed within the shell body. The shell bodies include an excavating portion shell body, a front shell body, and a rear shell body disposed in order from the leading end side in the advancing direction of excavation. The propelling mechanism comprises a projection mechanism and an extension mechanism. The projection mechanism includes front circumferential jacks in the front shell body and rear circumferential jacks in the rear shell body, both of which are capable of extension and contraction in the outer circumferential direction. The extension mechanism includes front axial jacks interposed between the excavating portion shell body and the front shell body, and rear axial jacks interposed between the front shell body and the rear shell body, both of which are capable of extension and contraction in the direction of advancing excavation.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT/JP2011/061642 filed on May 20, 2011, which claims priority to Japanese Application Nos. 2010-120071 filed on May 26, 2010 and 2010-256476 filed on Nov. 17, 2010. The entire contents of these applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention pertains to a tunnel excavation apparatus and tunnel excavation method for construction of tunnels in ground. 
       BACKGROUND ART 
       [0003]    The ring shield method has been a well-known method in recent years for efficiently constructing shield tunnels with large cross-sections. In the ring shield method, a tunnel is constructed by excavating earth in an annular cross sectional shape by repetitions of a stage for forward excavation of an annular sectional shape in a position corresponding to the outer shell portion of the tunnel, a stage for constructing a cylindrical lining body in the excavated part, and a stage for propelling the excavating apparatus using reaction force taken from the lining body, and, in parallel to this, excavating column-shaped dirt left behind on the inside of the lining body from behind (see Patent Citation 1). 
         [0004]    When using an excavating apparatus for thus forward excavating earth in an annular sectional shape, excavated dirt resulting from excavation of the earth must be transported to the rear of the cylindrical apparatus. For this purpose, in above patent reference 1, a discharge pipe is disposed inside the apparatus and excavated dirt is transported rearward through this discharge pipe. In addition to this discharge pipe, a screw conveyer can also be erected inside the apparatus and excavated dirt transported rearward by this screw conveyor. 
         [0005]    However, when excavated dirt discharge mechanisms, such as discharge pipes or screw conveyors, are erected inside the apparatus, the diameter of the discharge pipe or screw conveyor must be reduced in order to assure that they do not interfere with the excavating mechanism or the propelling mechanism, etc., resulting in the problem that large volumes of excavated dirt cannot be transported. 
         [0006]    In addition, a small discharge pipe or screw conveyor diameter leads to frequent dirt clogging. When such dirt clogging has occurred, the problem has been that clogged dirt could not be removed without reversing the excavating apparatus and removing the inner shell of the excavating apparatus. 
       PRIOR ART REFERENCES 
     Patent References 
       [0000]    
       
         Patent Reference: Published Patent No. 2840732 
       
     
       SUMMARY OF THE INVENTION 
       [0008]    The present invention was undertaken in light of the above-described problems, and has the object of providing a cylindrical excavating apparatus having a rotationally driven annular cutter portion capable of high volume transport of excavated dirt and of easy removal when clogging occurs. 
         [0009]    The tunnel excavating apparatus of the present invention is a tunnel excavating apparatus for excavating tunnels in earth, comprising: a cylindrical excavating mechanism, disposed on the leading end in the advancing excavation direction and furnished with an annular cutter portion having on its surface bits for excavating ground, capable of rotationally driving the cutter portion; a shell body, connected to the rear of the excavating mechanism and formed of a cylindrical outer cylinder body and a cylindrical inner cylinder body having an inner diameter larger than the inner diameter of the cutter portion; a propelling mechanism for propelling the excavating mechanism in the direction of advancing excavation; and a spiral blade, attached to the inner circumferential surface of the excavating mechanism inner cylinder body, of a height less than or equal to the difference between the cutter portion inner diameter and the inner cylinder body inner diameter, rotationally driven together with the cutter portion. 
         [0010]    Using the present invention, by attaching a spiral blade along the inner circumferential surface of the inside cylindrical body of the excavating mechanism, a large space can be secured without being affected by the space required for the excavating mechanism, the propelling mechanism, or the like, thus enabling the transport of large volumes of excavated soil. When soil clogging occurs, removal of earth remaining inside the excavating apparatus exposes the blade, thereby facilitating the work of removing the clogged soil. 
         [0011]    In the present invention, in the excavating mechanism, preferably has a gap is formed to communicate from the surface of the cutter portion through to the inner circumferential surface of the inside cylindrical body excavating mechanism for feeding excavated dirt excavated by the bits to the inner circumference side of the excavating mechanism. 
         [0012]    Soil excavated by the cutter portion is thus fed to the inside of the excavating mechanism via the gap. 
         [0013]    In the present invention, the propelling mechanism preferably having a projecting mechanism, disposed inside the shell body and capable of projecting a projection portion in the radial outward direction from the outer cylindrical surface of the shell body, and an extension mechanism, disposed inside the shell body, for pushing out the excavating mechanism in the advancing excavation direction by extension using reactive force against the ground in the annularly excavated surrounding area by projecting the protruding portion radially outward. 
         [0014]    In the excavating mechanism thus constituted, the work of propelling can be accomplished by projecting protruding portions radially outward using the projection mechanism and applying reactive force against the surrounding ground, therefore excavation of hard ground can be accomplished by receiving a large reaction force even if installation of segments or lining bodies is not complete. 
         [0015]    In the present invention, the shell body preferably includes an excavating portion shell body, a front shell body, and a rear shell body sequentially disposed starting from the leading end side in the direction of advancing excavation, and the excavating portion shell body is connected to the rear of the excavating mechanism; the extending mechanism includes front axial jacks, disposed to connect the excavating portion shell body and the front shell body and capable of extending and contracting in the direction of advancing excavation; and rear axial jacks, disposed to connect between the front shell body and the rear shell body, and capable of extending and contracting in the direction of advancing excavation; and the projection mechanism includes front circumferential jacks disposed within the front shell body and capable of extending and contracting radially outward, and rear circumferential jacks disposed within the rear shell body and capable of extending and contracting radially outward. 
         [0016]    Using an excavating mechanism thus constituted, a larger reaction force can be received from the ground using front and rear circumferential jacks when propelling the cutter portion forward. 
         [0017]    In the present invention, the propelling mechanism preferably comprises: an extension mechanism disposed within the shell body for pushing the excavating mechanism in the direction of advancing excavation by extension in a state whereby reaction force is obtained against segments attached to the inner circumferential surface of a tunnel in which excavation has been completed. 
         [0018]    Using an excavating mechanism thus constituted, the length of the excavating mechanism can be shortened. 
         [0019]    The excavation method of the present invention is a method for excavating tunnels in ground using a tunnel excavating apparatus, wherein the tunnel excavating apparatus comprises: a cylindrical excavating mechanism, disposed on the leading end in the advancing excavation direction and furnished with an annular cutter portion having on its surface bits for excavating ground, capable of rotationally driving the cutter portion; a shell body, connected to the rear of the excavating mechanism and formed of a cylindrical outer cylinder body and a cylindrical inner cylinder body having an inner diameter larger than the inner diameter of the cutter portion; a propelling mechanism for propelling the excavating mechanism in the direction of advancing excavation; and a spiral blade, attached to the inner circumferential surface of the excavating mechanism inner cylinder body, of a height less than or equal to the difference between the cutter portion inner diameter and the inner cylinder body inner diameter, rotationally driven together with the cutter portion; and including a forward excavation step for excavating earth in an annular shape by pushing said excavating mechanism with the propelling mechanism while rotationally driving the excavating mechanism, and while feeding excavated dirt along the inner circumferential surface of the inner shell using the blade rotating together with the excavating mechanism; and a following excavation step for excavating ground on the inside of an annularly excavated part. 
         [0020]    The present invention enables transport of large volumes of excavated dirt, and when dirt clogging does occur, that dirt can be easily removed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective view showing an excavating apparatus according to a first embodiment of the present invention. 
           [0022]      FIG. 2  is a vertical section in the direction of advancing excavation by the excavating apparatus shown in  FIG. 1 . 
           [0023]      FIG. 3  is a side elevation seen along A-A in  FIG. 2 . 
           [0024]      FIG. 4  is a cross section seen along B-B in  FIG. 2 . 
           [0025]      FIG. 5  is an expanded diagram of the C portion in  FIG. 2 . 
           [0026]      FIGS. 6(   a ) through ( m ) respectively show the disposition of multiple roller bits in the excavating apparatus shown in  FIG. 1 ; (A) shows the roller bits in (a) through (m) in superimposition. 
           [0027]      FIG. 7  is a vertical section in the direction of advancing excavation, for the purpose of explaining a tunnel excavation method using the excavating apparatus shown in  FIG. 1 . 
           [0028]      FIG. 8  is a vertical section (No.  1 ) of an excavating apparatus, for the purpose of explaining a method for propelling the excavating apparatus shown in  FIG. 1 . 
           [0029]      FIG. 9  is a vertical section (No.  2 ) of the excavating apparatus, for the purpose of explaining a method for propelling the excavating apparatus shown in  FIG. 1 . 
           [0030]      FIG. 10  is a vertical section (No.  3 ) of the excavating apparatus, for the purpose of explaining a method for propelling the excavating apparatus shown in  FIG. 1 . 
           [0031]      FIG. 11  is a vertical section along the direction of advancing excavation of an excavating apparatus according to a second embodiment of the present invention. 
           [0032]      FIG. 12  is a vertical section along the direction of advancing excavation of an excavating apparatus according to a third embodiment of the present invention. 
           [0033]      FIG. 13  is a side elevation seen along A-A in  FIG. 12 . 
           [0034]      FIG. 14  is a cross section seen along B-B in  FIG. 12 . 
           [0035]      FIG. 15  is an expanded cross section along the direction of advancing excavation of the leading end portion of the excavating mechanism in an excavating apparatus according to an embodiment of the present invention. 
           [0036]      FIG. 16  is a cross section seen along C-C in  FIG. 15 . 
           [0037]      FIG. 17  is a vertical section in the direction of advancing excavation, for the purpose of explaining a tunnel excavation method using the excavating apparatus according to a third embodiment of the present invention. 
           [0038]      FIG. 18  is a vertical section (No.  1 ) of an excavating apparatus, for the purpose of explaining a method for propelling an excavating apparatus according to a third embodiment of the present invention. 
           [0039]      FIG. 19  is a vertical section (No.  2 ) of an excavating apparatus, for the purpose of explaining a method for propelling an excavating apparatus according to a third embodiment of the present invention. 
           [0040]      FIG. 20  is a vertical section (No.  3 ) of an excavating apparatus, for the purpose of explaining the method of propelling an excavating apparatus according to a third embodiment of the present invention. 
           [0041]      FIG. 21  is an expanded vertical section of the leading end portion of an excavating mechanism, for the purpose of explaining another method for discharging excavated dirt in an excavating apparatus according to a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0042]    Below, referring to figures, we discuss details of the excavating apparatus and excavating method constituting a first embodiment of the present invention. 
         [0043]      FIG. 1  is a perspective view showing an excavating apparatus  1  according to the present embodiment;  FIG. 2  is a vertical section in the direction of advancing excavation by the excavating apparatus  1  according to the present embodiment;  FIG. 3  is a side elevation seen along A-A in  FIG. 2 ; and  FIG. 4  is a section seen along B-B in  FIG. 2 .  FIG. 5  is an expanded diagram of the C portion in  FIG. 2 . 
         [0044]    As shown in  FIGS. 1 and 2 , the excavating apparatus  1  comprises: a cylindrical shell body  2 ; an excavating mechanism  4  disposed on the end of the shell body  2  in the direction of advancing excavation thereof (the “front” hereafter); an excavated dirt discharge mechanism  6 ; and a propelling mechanism  8  for propelling the excavating mechanism  4 . 
         [0045]    As shown in  FIG. 2 , the shell body  2  comprises, sequentially connected from the front: a first excavating portion shell body  10 ; a second excavating portion shell body  11 ; a front shell body  12 ; and a rear shell body  14 . Each shell body  10 ,  11 ,  12 , and  14  comprises: outer cylinder bodies  10 C,  11 C,  12 C, and  14 C; inner cylinder bodies  10 B,  11 B,  12 B, and  14 B disposed inside outer cylinder bodies  10 C,  11 C,  12 C, and  14 C; and multiple support members  20 ,  22 , and  24  disposed so as to connect inner cylinder bodies  10 B,  11 B,  12 B, and  14 B and outer cylinder bodies  10 C,  11 C,  12 C, and  14 C (first excavating portion shell body  10  support member is not shown). Inner cylinder bodies  10 B,  11 B,  12 B, and  14 B and outer cylinder bodies  10 C,  11 C,  12 C, and  14 C are respectively made of steel. Note that in the first excavating body shell body, the inner cylinder body  10 B ends further back on the rear side than the outer cylinder body  10 C. 
         [0046]    These inner cylinder bodies  10 B,  11 B,  12 B, and  14 B, and outer cylinder bodies  10 C,  11 C,  12 C, and  14 C are disposed concentrically and coaxially with the rotational axis of the excavating mechanism  4  described in detail below; by this means an annular space is formed between the inner cylinder bodies  10 B,  11 B,  12 B, and  14 B and the outer cylinder bodies  10 C,  11 C,  12 C, and  14 C. The support members  20 ,  22 , and  24  are made of rod-shaped steel, and are disposed in a number capable of supporting the ground pressure acting on the outer cylinder bodies  10 C,  11 C,  12 C, and  14 C in a radiating fashion around the center axis of the inner cylinder bodies  10 B,  11 B,  12 B, and  14 B, appropriately spaced in the circumferential and axial directions to connect these inner cylinder bodies  10 B,  11 B,  12 B, and  14 B and outer cylinder bodies  10 C,  11 C,  12 C, and  14 C. A propelling mechanism  8  is housed in the annular space between the inner cylinder bodies  10 B,  11 B,  12 B, and  14 B and the outer cylinder bodies  10 C,  11 C,  12 C, and  14 C. 
         [0047]    The first excavating portion shell body  10  is formed to have a fixed outer diameter and inner diameter from the leading end portion to the center portion in the direction of advancing excavation, and the inner circumferential surface at the rear end portion of the inner cylinder body  10 B and outer circumferential surface of the rear end portion of the outer cylinder body  10 C are notched. The leading end portion of the inner circumferential surface of the second excavating portion shell body  11  inner cylinder body  11 B and the leading end portion of the outer circumferential surface of the outer cylinder body  11 C are also notched, and the first excavating portion shell body  10  is rotatably connected to the second excavating portion shell body  11  by housing the leading end portion of the second excavating portion shell body  11  inside the rear end portion of the first excavating portion shell body  10 . Note that a member or material for improving the sliding of a bearing or the like may be interposed between the first and second excavating portion shell bodies  10  and  11 . 
         [0048]    On the second excavating portion shell body  11 , the rear end portion of the inner circumferential surface of inner cylinder body  10 B and the rear end portion of the outer circumferential surface of outer cylinder body  10 C are notched. Also, on the front shell body  12  the rear end portion of the outer circumferential surface of inner cylinder body  12 B and the rear end portion of the inner circumferential surface of outer cylinder body  12 C are notched. By housing the second excavating portion shell body  11  on the inside of the leading end portion of the front shell body  12 , the second excavating portion shell body  11  is connected so as to be slidable in the axial direction relative to the front shell body  12 . 
         [0049]    Similarly, on the front shell body  12 , the rear end portion of the inner circumferential surface of inner cylinder body  12 B and the rear end portion of the outer circumferential surface of outer cylinder body  12 C are notched. Also, on the rear shell body  14 , the rear end portion of the inner circumferential surface of inner cylinder body  14 B and the rear end portion of the inner circumferential surface of outer cylinder body  14  are notched. By housing the rear end portion of the front shell body  12  on the inside of the leading end portion of the rear shell body  14 , the front shell body  12  is connected so as to be slidable in the axial direction relative to the rear shell body  14 . Note that it is also acceptable to provide a guide member to guide axial sliding at the connecting portion between second excavating portion shell body  11  and front shell body  12 , and between front shell body  12  and rear shell body  14 . 
         [0050]    As shown in  FIGS. 2 and 3 , excavating mechanism  4  is affixed to the leading end portion of the first excavating portion shell body  10 . Excavating mechanism  4  comprises: a cutter portion  26  attached to the leading end in the direction of advancing excavation of the first excavating portion shell body  10  so as to cover the area between the inner cylinder body  10 B and the outer cylinder body  10 C; a speed reducer  28  disposed within the excavating portion shell body  10 ; and a motor  30  disposed within the front shell body  12 . 
         [0051]    The cutter portion  26  comprises: a ring-shaped cutter portion main body  32 ; 13 pairs of roller bits  36  disposed on the cutter portion main body  32  and separated by spaces in the circumferential direction; and boring bits  38 , disposed on the edge of opening  32 A formed on the cutter portion main body  32 . In addition, as shown in  FIG. 5 , a pin rack  34  is attached along the edge at the rear of the cutter portion main body  32 . 
         [0052]    As shown in  FIG. 5 , the cutter portion main body  32  has a U-shaped cross sectional shape in axial section, and the diameter D 1  thereof is approximately equal to the outer diameter of the excavating portion shell body  10  outer cylinder body  10 C. The inner diameter D 3  of cutter portion main body  32  is smaller than the inner diameter D 2  of the first excavating portion shell body  10  inner cylinder body  10 B by exactly dx. In addition, as discussed above, in the first excavating portion shell body  10 , the inner cylinder body  10 B terminates further back than the outer cylinder body  10 C. Given the above constitution, a gap  40  is formed between the inside rear of the cutter portion main body  32  and the inner cylinder body  10 B of the first excavating portion shell body  10 , and the space inside this cutter portion main body  32  and the space inside the first excavating portion shell body  10  inner cylinder body  10 B communicate through this gap  40 . 
         [0053]    As shown in  FIG. 5 , a motor  30  is disposed inside the second excavating portion shell body  11 ; speed reducer  28  is connected to the rotating shaft of this motor  30 , and a pinion  28 A is attached to the speed reducer  28 . The pinion  28 A attached to the speed reducer  28  engages a pin rack  34  attached to the cutter portion  26 . When the motor  30  rotates a rotary force is thus transferred to the cutter portion  26  with a torque amplified by the speed reducer  28 , so that cutter portion  26  rotates relative to the second excavating portion shell body  11  about the center axis of the first excavating portion shell body  10 . 
         [0054]      FIG. 6  shows the radial disposition of the respective multiple roller bits  36  attached to the cutter portion main body  32 ; (a) through (m) depict the radial disposition of each roller bit  36 , and (A) depicts all of the roller bits in superimposition. As shown in the figure, each roller bit is disposed at a different radial position. Thus when the cutter portion  26  rotates in the circumferential direction, the trajectories traveled by each of the roller bits  36  form concentric circles approximately evenly spaced in the radial direction, making excavation uniform irrespective of diameter. 
         [0055]    Boring bits  38  are sharp-tipped bits which, by the rotation of the cutter portion  26 , excavate so that surfaces excavated by roller bits  36  are uniformly flattened. 
         [0056]    As shown in  FIG. 5 , the excavated dirt discharge mechanism  6  comprises: a blade  42  constituting a screw conveyor attached along the inner circumferential surface of the inner cylinder body  10 B of the first excavating portion shell body  10 ; and a jet nozzle (not shown) disposed so that a jetting outlet thereon is exposed on the surface of the cutter portion main body  32  to jet water toward ground. The blade  42  is made of spiral steel concentric and coaxial with the excavating apparatus  1 ; it is affixed to the inner circumferential surface of the inner cylinder body  10 B of the first excavating portion shell body  10  in the axial direction from the rear end of the cutter portion main body  32  to the rear end of the first excavating portion shell body  10 . The blade  42  forms an isosceles triangle shape in section, the height of which is approximately equal to dx, which is half the difference between the inner diameter D 2  of the first excavating portion shell body  10  inner cylinder body  10 B and the inner diameter D 3  of the cutter portion main body  32 . I.e., the distance (inner diameter) from the peak of the blade  42  to the center axis of the excavating apparatus  1  is equal to the inner diameter D 3  of the cutter portion main body  32 . Note that in the present embodiment, blade  42  height is approximately equal to dx, but it may also be made shorter. 
         [0057]    As shown in  FIGS. 1 and 3 , the propelling mechanism  8  comprises: multiple pairs of serially connected front and rear axial hydraulic jacks  48  and  50  extending in the direction of advancing excavation; multiple front and rear radial hydraulic jacks  52  and  54  disposed between circumferentially adjacent axial hydraulic jacks  48  and  50 ; and multiple support plates  56  and  58 , respectively connected to front and rear radial hydraulic jacks  52  and  54 . 
         [0058]    Each pair of front and rear axial hydraulic jacks  48  and  50  is serially connected to extend in the direction of advancing excavation. In the present embodiment  10  pairs of the front and rear axial hydraulic jack  48  and  50  in each pair are disposed at equal angle spacing in the shell body  2  circumferential direction so that uniform propulsion force is obtained regardless of angle. 
         [0059]    Front and rear hydraulic jacks  48  are housed between the inner cylinder bodies  11 B,  12 B and outer cylinder bodies  11 C,  12 C from the second excavating portion shell body  11  to the front shell body  12 ; the leading end is affixed to the second excavating portion shell body  11  support member  20  and the rear tip is affixed to front shell body  12  support member  22 . 
         [0060]    A rear hydraulic jack  50  is housed between inner cylinder bodies  12 B,  14 B and outer cylinder bodies  12 C,  14 C from front shell body  12  to rear shell body  14 ; the leading end is affixed to the support member  22  of the front shell body  12  and the rear tip is affixed to the support member  24  of the rear shell body  14 . Thus front and rear hydraulic jacks  48  and  50  are serially connected via support member  22 . 
         [0061]    Front and rear radial hydraulic jacks  52  and  54  are disposed at positions corresponding to the four corners of support plates  56 ,  58  as a set of four hydraulic jack units relative to rectangular support plates  56 ,  58 . The paired front and rear radial hydraulic jacks  52 ,  54  are respectively housed in the front shell body  12  and rear shell body  14 , separated by a space in the excavation advancing direction. In the present embodiment, the front and rear radial hydraulic jacks  52 ,  54  are respectively disposed at equal angle spacing in the circumferential direction so that uniform ground reaction force is obtained regardless of angle. 
         [0062]    Formed on front and rear front shell body  12  and  14  outer cylinder bodies  12 B and  14 B are openings  12 A and  14 A at positions corresponding to front and rear radial hydraulic jacks  52  and  54 . The front and rear radial hydraulic jacks  52  and  54  are affixed at one end to front and rear shell body  12  and  14  inner cylinder bodies  12 B and  14 B, and at the other end to support plates  56  and  58  having approximately the same shape as the openings  12 A and  14 A formed on outer cylinder body  18 . In this constitution, extension of the radial hydraulic jacks  52  and  54  causes support plates  56  and  58  to project outward toward the outer perimeter. 
         [0063]    Note that these axial hydraulic jacks  48  and  50  and radial hydraulic jacks  52  and  54  are connected to a control device (not shown), and hydraulic pressure is supplied from the control device. 
         [0064]    Below we explain a tunnel excavation method using the above-described excavating apparatus  1 . 
         [0065]      FIG. 7  is a vertical cross section showing tunnel excavation using an excavating apparatus  1  according to the present embodiment. As shown in that figure, in the present embodiment a tunnel with a circular cross section is constructed by a forward excavation of ground  62  in a cylindrical shape using excavating apparatus  1 , followed by excavation of ground  64  in the remaining center portion using heavy equipment. 
         [0066]    First, referring to  FIGS. 8 through 10 , we discuss a method for propelling excavating mechanism  4  using propelling mechanism  8 . Note that the propelling operation is accomplished by rotating the excavating mechanism  4  cutter portion  26  about the axis of the excavating apparatus  1  and discharging excavated dirt using excavated dirt discharge mechanism  6 . 
         [0067]    First, as shown in  FIG. 8 , the front and rear radial hydraulic jacks  52  and  54  are extended with the front and rear axial hydraulic jacks  48  and  50  in a contracted state so that surrounding ground is pressed by the support plates  56  and  58 . With reaction force obtained from the ground using support plates  56  and  58 , the front axial hydraulic jack  48  is extended to push the excavating mechanism  4  forward, and ground is excavated in a cylindrical shape by the excavating mechanism  4 . 
         [0068]    In this manner, as shown in  FIG. 9 , once excavation has been carried out over a predetermined distance, the front radial hydraulic jack  52  is caused to contract and ground is pressed by the rear support plate  58  alone. The front axial hydraulic jack  48  is then caused to contract and the rear axial hydraulic jack  50  is extended at that same speed. This enables the front shell body  12  to be advanced while maintaining the position of the excavating mechanism  4 . 
         [0069]    Next, as shown in  FIG. 10 , the front radial hydraulic jack  52  is extended and ground is pressed by the front support plate  56 , while the rear radial hydraulic jack  54  is caused to contract. The rear axial hydraulic jack  50  is then caused to contract. This enables the rear shell body  14  to be advanced while maintaining the position of the excavating mechanism  4  and the front shell body  12 . 
         [0070]    By repeating the aforementioned steps, the excavating mechanism  4  can be made to advance forward and the excavating apparatus  1  can be propelled. 
         [0071]    In addition to the aforementioned propelling operation, the cutter portion  26  is rotated to excavate ground and the excavated dirt thus excavated is fed to rear of the apparatus. 
         [0072]    I.e., the motor  30  of the excavating mechanism  4  is rotated with the cutter portion  26  pushed against the ground by the propelling mechanism  8 . The rotary force of the motor  30  is transferred to speed reducer  28  where torque is amplified, and cutter portion  26  is rotated via pinion  60  and pin rack  34 . When the cutter portion  26  rotates, ground is first excavated in a saw-tooth sectional shape by roller bits  36 , then surface unevenness is ground off using boring bits  38 . This enables ground to be excavated in an annular shape. 
         [0073]    When the cutter portion  26  rotates, the blade  42  also rotates together therewith. Excavated dirt produced by excavation of ground by the cutter portion  26  is mixed with water jetted from the jet nozzle to improve its fluidity. Excavated dirt is then directed from the opening  32 A formed in cutter portion main body  32  into the annular space within the excavating portion shell body  10  and discharged from the rear opening  40  of the first excavating portion shell body  10 . Excavated dirt discharged from the rear of the first excavating portion shell body  10  is fed to the annular space between the inner cylindrical body  10 B of the first excavating portion shell body  10  and the ground left as a columnar shape therein at the time of annular excavation. Excavated dirt fed between the inner cylindrical body  10 B and the columnar remaining ground is fed toward the rear of the apparatus along the inner circumferential surface of the inner cylindrical body  10 B of the first excavating portion shell body  10  by the spiral blade  42  which rotates together with the cutter portion  26 . At this point, the distance (inner diameter) from the peak of the blade  42  to the center axis of the excavating apparatus  1  is equal to the inner diameter of the cutter portion main body  32 , therefore no gap is formed between the leading end of the blade  42  and the ground left in an annular shape, and dirt can be reliably transported. 
         [0074]    If at this point clogging of blade  42  occurs, blade  42  can be exposed by excavating the ring-shaped residual dirt left on the inside of the excavating apparatus  1 , and the clogging can be easily removed. 
         [0075]    Behind the excavating apparatus  1 , a temporary protection plate  72  is attached to the inner circumferential surface of the annularly excavated tunnel. 
         [0076]    In parallel to the forward excavation work above, ground  64  on the inside of the part excavated in a ring shape by the excavating apparatus  1  is excavated up to a position behind the first excavating portion shell body  10 . This excavating work may be done using a breaker  66  or heavy equipment such as a backhoe or the like. 
         [0077]    Excavated dirt resulting from the excavation of excavated dirt and ground moved by the blade is loaded onto a dump truck  70  by a Schaeff loader  68  and conveyed outside the tunnel. 
         [0078]    Next, in the part of the total tunnel cross section in which excavation is completed, temporary protection plate  72  is removed from the inner circumferential surface of the tunnel, and lining using segment  74  or the like is installed. 
         [0079]    A circular section tunnel can be constructed using the steps above. 
         [0080]    Using the present embodiment, a spiral blade  42  is attached to the inner circumferential surface of the inner cylindrical body  10 B of the first excavating portion shell body  10  as an excavated dirt discharge mechanism  6 , thus ensuring space for discharging large sectional area excavated dirt and permitting the transport of large volumes of excavated dirt. 
         [0081]    Also, because the blade  42  is attached to the inner circumferential surface of the first excavating portion shell body  10  inner cylindrical body  10 B, even if clogging should occur dirt can be easily eliminated by removing dirt remaining on the inside of the first excavating portion shell body  10 . 
         [0082]    In addition, in the present embodiment excavated dirt can be transported by the rotation of the cutter portion  26 , therefore no separate drive force is required apart from the drive force for turning the cutter portion  26 . 
         [0083]    Note that in the present embodiment only one spiral blade  42  is provided on the first excavating portion shell body  10  inner cylindrical body  10 B, but the invention is not limited thereto, and multiple spiral blades may also be provided. 
         [0084]    Furthermore, the embodiment above provided front and rear axial hydraulic jacks  48  and  50 , but the invention is not limited thereto, and it is also acceptable to provide only one axial hydraulic jack. 
       Second Embodiment 
       [0085]    Below we discuss a second embodiment of the present invention. 
         [0086]    In the present embodiment, it is primarily the constitution of the propelling mechanism which differs from the first embodiment. Note that in the explanation of the present embodiment, elements in common with the first embodiment are given the same reference numerals and explanations thereof are omitted. 
         [0087]      FIG. 11  is a vertical cross section showing the constitution of an excavating apparatus having a propelling mechanism different from that of the first embodiment. As shown in that figure, an excavating apparatus  101  comprises: a cylindrical shell body  102 , an excavating mechanism  4  disposed on the leading end of the shell body  102 , an excavated dirt discharge mechanism  6 , and a propelling mechanism  108  connected to the rear of the excavating mechanism  4 . 
         [0088]    In the present embodiment, the shell body  102  comprises: a first shell body  110  and a second shell body  111 , sequentially connected from the front. The first and second shell bodies  110  and  111  are respectively constituted by cylindrical outer cylinder bodies  110 C and  111 C, inner cylinder bodies  110 B and  111 B disposed within outer cylinder bodies  110 C and  111 C, and multiple support members  120  disposed to connect inner cylinder bodies  110 B,  111 B and outer cylinder bodies  110 C,  111 C. 
         [0089]    These inner cylinder bodies  110 B,  111 B and outer cylinder bodies  110 C,  111 C are disposed concentrically and coaxially with the rotating axis of excavating mechanism  4 , such that an annular space is formed between inner cylinder bodies  110 B,  111 B and outer cylinder bodies  110 C,  111 C. Support members  120  are made of rod-shaped steel, and are arrayed radially about the center axis of the inner cylinder bodies  110 B,  111 B in a number capable of supporting the ground pressure acting on outer cylinder bodies  110 C,  111 C, and spaced appropriately in the circumferential and axial direction, connecting these inner cylinder bodies  110 B,  111 B and outer cylinder bodies  110 C,  111 C. The excavating mechanism  4  speed reducer  28 , motor  30 , and propelling mechanism  108  are housed within the annular space between the inner cylinder bodies  110 B,  111 B and outer cylinder bodies  110 C,  111 C. 
         [0090]    A propelling mechanism  108  is constituted by multiple axial hydraulic jacks  148  extending in the direction of advancing excavation. In the present embodiment,  10  axial hydraulic jacks  148  are disposed at equal angle spacing in the shell body  102  circumferential direction so that uniform propulsion force is obtained regardless of angle. The axial hydraulic jacks  148  are affixed at the leading end to the second excavating portion shell body  111  support members  120 . Note that, although not shown, the axial hydraulic jacks  148  are supported on the shell body  111  by an appropriate support means so as to be maintained in a parallel orientation to the axial direction of the excavating apparatus  101  when the axial hydraulic jacks  148  extends and contracts. 
         [0091]    In the present embodiment the propelling mechanism is propelled by extension of the axial hydraulic jacks with reaction force obtained from segments affixed to the inner circumference of a tunnel in which excavation has been completed. In parallel with this excavating work, as in the first embodiment, the cutter portion  26  the excavating mechanism  4  is rotated about the axis of the excavating apparatus  1  and excavated dirt is discharged by the excavated dirt discharge mechanism  6 . 
         [0092]    The same effect as in the first embodiment can also be obtained using the second embodiment excavating apparatus described above. 
         [0093]    In addition, the overall length of the excavating apparatus can be shortened using the present embodiment. 
       Third Embodiment 
       [0094]    Below, referring to figures, we discuss details of the excavating apparatus and excavating method constituting the third embodiment of the present invention. In the present embodiment, it is primarily the constitution of the excavated dirt discharge mechanism which differs from the first embodiment and the second embodiment. 
         [0095]      FIG. 12  is a vertical section in the direction of advancing excavation by the excavating apparatus  1  according to the present embodiment;  FIG. 13  is a side elevation seen along A-A in  FIG. 12 ; and  FIG. 14  is a section seen along B-B in  FIG. 13 .  FIG. 15  is an expanded section of the leading end portion of an excavating apparatus  201  excavating mechanism  204 ;  FIG. 16  is a cross section through C-C in  FIG. 15 . 
         [0096]    As shown in  FIGS. 12 and 15 , the excavating apparatus  201  comprises: a cylindrical shell body  202 ; an excavating mechanism  204  disposed on the end of shell body  2  in the direction of advancing excavation thereof (the “front” hereafter); an excavated dirt discharge mechanism  206 ; and a propelling mechanism  8  for propelling excavating mechanism  204 . 
         [0097]    The shell body  2  comprises: an excavating portion shell body  210 ; a front shell body  212 ; and a rear shell body  214  connected sequentially from the leading end in the advancing direction of excavation. Each shell body  210 ,  212 , and  214  comprises: inner cylinder bodies  210 B,  212 B, and  214 B made of cylindrically formed steel; an outer cylinder body  218  with a larger diameter than the inner cylinder bodies  210 B,  212 B, and  214 B disposed concentrically and coaxially and made of steel; and multiple support members  220 ,  222 , and  224  disposed to connect between these inner cylinder bodies  210 B,  212 B, and  214 B and outer cylinder bodies  210 C,  212 C, and  214 C, holding the spacing between these inner cylinder bodies  210 B,  212 B, and  214 B and outer cylinder bodies  210 C,  212 C, and  214 C. In this constitution, an annular space is formed between the inner cylinder bodies  210 B,  212 B,  214 B and the outer cylinder body  218 , and the excavating mechanism  204 , excavated dirt discharge mechanism  206 , and propelling mechanism  208  are housed within this annular space. 
         [0098]    The excavating portion shell body  210  is formed to have a predetermined diameter from the leading end to the mid-portion; the rear end is formed with a smaller diameter than the mid-portion, and this small diameter portion is housed within the leading end of the front shell body  212 . Similarly, the front shell body  212  is formed to have a predetermined diameter from the leading end to the mid-portion; the rear end is formed with a smaller diameter than the mid-portion, and this small diameter portion is housed within the leading end of the rear shell body  214 . 
         [0099]    Support members  220 ,  222 , and  224  are made of rod-shaped steel, and are arrayed radially about the center axis of the inner cylinder body  216  in a number capable of supporting the ground pressure acting on outer cylinder body  218 , and spaced appropriately in the circumferential and axial direction. 
         [0100]    As shown in  FIG. 12 , the excavating mechanism  204  is housed in the leading end of the excavating portion shell body  210 , and comprises: a cutter portion  226 ; a speed reducer  228 ; and a motor  230  disposed at the leading end of the excavating portion shell body  210 .As shown in  FIGS. 13 and 15 , the cutter portion  226  is annular, and comprises: a cutter portion main body  232  having a U-shaped section; an annular pin rack  234  disposed along the edge of the rear side of the cutter portion main body  232 ; roller bits  236  spaced apart in the circumferential direction on the cutter portion main body  232 ; and intake hole  238  and scraper  240  disposed circumferentially behind the roller bits  236 . 
         [0101]    A speed reducer  228  is connected to the rotary shaft of motor  230 , and a pinion  260  is attached to this speed reducer  228 . As shown in  FIG. 16 , speed reducer  228  pinion  260  meshes with the pin rack  234  of the cutter portion  226 . Thus when the motor  230  rotates, this rotary force is transferred to the cutter portion  226  with torque amplified via speed reducer  228 , and cutter portion  226  is rotated with a large force. 
         [0102]    As shown in  FIG. 13 , an intake hole  238  is formed to extend over the width direction of the cutter portion main body  232 . Intake hole  238  communicates with an excavated dirt discharge pipe  242  forming an excavated dirt discharge mechanism  206 , and excavated dirt taken in from intake hole  238  is fed to excavated dirt discharge pipe  242 . Roller bits  236  and scraper  240  are attached to cutter portion main body  232  so as to be able to excavate ground when the cutter portion  226  is rotated in the circumferential direction. 
         [0103]    As shown in  FIG. 15 , the excavated dirt discharge mechanism  206  comprises: multiple excavated dirt discharge pipes  242  spaced apart in the circumferential direction within the shell body  202 ; a screw feeder  246  disposed within the excavated dirt discharge pipe  242 ; and a jet nozzle (not shown) for jetting water toward the ground. Excavated dirt resulting from excavation of ground is mixed with the jetted water from the jet nozzle, moved through the intake hole  238  by rotation of the cutter portion  226 , and transported through the excavated dirt discharge pipe  242  by rotation of the screw feeder  246  to the rear of the excavator. 
         [0104]    As shown in  FIGS. 12 and 14 , the propelling mechanism  208  comprises: multiple pairs of serially connected front and rear axial hydraulic jacks  248  and  250  extending in the direction of advancing excavation; multiple front and rear radial hydraulic jacks  252  and  254  disposed between circumferentially adjacent axial hydraulic jacks  248  and  250 ; and multiple support plates  256  and  258 , respectively connected to front and rear radial hydraulic jacks  252  and  254 . 
         [0105]    Each pair of front and rear axial hydraulic jacks  248  and  250  is serially connected to extend in the direction of advancing excavation. In the present embodiment, 10 pairs of each pair of front and rear axial hydraulic jack  248  and  250  are disposed at approximately equal spacing in the shell body  202  circumferential direction so that uniform propulsion force is obtained regardless of angle. 
         [0106]    Front and rear hydraulic jacks  248  are housed between the inner cylinder bodies  210 B,  212 B and outer cylinder bodies  210 C,  212 C from the excavating portion shell body  210  to the front shell body  212 ; the leading end is affixed to the support member  220  of the second excavating portion shell body  210  and the rear tip is affixed to the support member  222  of the front shell body  212 . 
         [0107]    A rear hydraulic jack  250  is housed between inner cylinder bodies  212 B,  214 B and outer cylinder bodies  212 C,  214 C from front shell body  212  to rear shell body  214 ; the leading end is affixed to the front the support member  222  of the shell body  212  and the rear tip is affixed to the support member  224  of the rear shell body  214 . Thus, the front and rear hydraulic jacks  248  and  250  are serially connected via support member  222 . 
         [0108]    Front and rear radial hydraulic jacks  252  and  254  are disposed at positions corresponding to the four corners of support plates  256 ,  258  as a set of 4 hydraulic jack units relative to rectangular support plates  256 ,  258 . The paired front and rear radial hydraulic jacks  252 ,  254  are respectively housed in the front shell body  212  and rear shell body  214 , separated by a space in the advancing direction of excavation. In the present embodiment the front and rear radial hydraulic jacks  252 ,  254  are respectively disposed at equal angle spacing in the circumferential direction so that uniform ground reaction force is obtained regardless of angle. 
         [0109]    Formed on the outer cylinder bodies  212 B and  214 B of the front and rear front shell body  212  and  214  are openings  212 A and  214 A at positions corresponding to the front and rear radial hydraulic jacks  252  and  254 . The front and rear radial hydraulic jacks  252  and  254  are affixed at one end to the inner cylinder bodies  212 B and  214 B of the front and rear shell body  212  and  214 , and at the other end to support plates  256  and  258 , which have approximately the same shape as the openings  212 A and  214 A formed on outer cylinder body  218 . In this constitution, extension of the radial hydraulic jacks  252  and  254  causes support plates  256  and  258  to project outward toward the outer perimeter. 
         [0110]    Note that these axial hydraulic jacks  248  and  250  and radial hydraulic jacks  252  and  254  are connected to a control device (not shown), and hydraulic pressure is supplied from the control device. 
         [0111]    Below we explain a tunnel excavation method using the above-described excavating apparatus  201 . 
         [0112]      FIG. 17  is a vertical cross section showing tunnel excavation using an excavating apparatus  201  according to the present embodiment. As shown in that figure, in the present embodiment a tunnel with a circular cross section is constructed by forward excavation of ground  262  in a cylindrical shape using excavating apparatus  201 , followed by excavation of ground  264  in the remaining center portion using heavy equipment. 
         [0113]    When excavating using excavating apparatus  201 , excavated dirt is discharged to the outside by excavated dirt discharge mechanism  206  at the same time as ground  264  is excavated by excavating mechanism  204 , while excavating mechanism  204  is pushed in the direction of advancing excavation by propelling mechanism  208 . 
         [0114]    First, referring to  FIGS. 18 through 20 , we discuss a method for propelling excavating mechanism  204  using propelling mechanism  208 . Note that the propelling operation is accomplished by rotating the excavating mechanism  204  cutter portion  226  about the axis of the excavating apparatus  201  and discharging excavated dirt using excavated dirt discharge mechanism  206 . 
         [0115]    First, as shown in  FIG. 18 , the front and rear radial hydraulic jacks  252  and  254  are extended with the front and rear axial hydraulic jacks  248  and  250  in a contracted state so that surrounding ground is pressed by the support plates  256  and  258 . With reaction force obtained from the ground using support plates  256  and  258 , the front axial hydraulic jack  248  is extended to push the excavating mechanism  204  forward, and ground is excavated in a cylindrical shape by the excavating mechanism  204 . 
         [0116]    In this manner, as shown in  FIG. 19 , once excavation has been carried out over a predetermined distance, the front radial hydraulic jack  252  is caused to contract and ground is pressed by the rear support plate  258  alone. The front axial hydraulic jack  248  is then caused to contract and the rear axial hydraulic jack  250  is extended at that same speed. This enables the front shell body  212  to be advanced while maintaining the position of the excavating mechanism  204 . 
         [0117]    Next, as shown in  FIG. 20 , the front radial hydraulic jack  252  is extended and ground is pressed by the front support plate  256 , while the rear radial hydraulic jack  254  is caused to contract. The rear axial hydraulic jack  250  is then caused to contract. This enables the rear shell body  214  to be advanced while maintaining the position of the excavating mechanism  204  and the front shell body  212 . 
         [0118]    By repeating the aforementioned steps, the excavating mechanism  204  can be made to advance forward and the excavating apparatus  201  can be propelled. 
         [0119]    Together with the aforementioned propelling operation, the cutter portion  226  is rotated to excavate ground. In other words, the motor  230  of the excavating mechanism  204  is rotated in a state whereby the cutter portion  226  pushed against the ground by the propelling mechanism  208 . The rotary force of the motor  230  is transferred to speed reducer  228 , where torque is amplified, and cutter portion  226  is rotated via pinion  260  and pin rack  234 . When the cutter portion  226  rotates, ground is first excavated in a saw-tooth sectional shape by roller bits  236 , then surface unevenness is ground off using scraper  240 . This enables ground to be excavated in an annular shape. Behind the excavating apparatus  201 , a temporary protection plate  272  is attached to the inner circumferential surface of the annularly excavated tunnel. Note that excavated dirt resulting from the excavation of ground is taken in to the intake hole  238  on the cutter portion  226  and discharged through excavated dirt discharge pipe  242  by excavated dirt discharge mechanism  206  to behind the excavating apparatus  201 . 
         [0120]    In parallel to the forward excavation work above, ground  264  in the inside of the portion excavated in an annular shape by the excavating apparatus  201  is excavated. This excavating work may be done using a breaker  266  or an apparatus such as a backhoe or the like. Excavated dirt resulting from the excavation of ground is loaded onto a dump truck  270  by a Schaeff loader  268  and conveyed outside the tunnel. 
         [0121]    Next, in the part of the total tunnel cross section in which excavation is completed, temporary protection plate  272  is removed from the inner circumferential surface of the tunnel, and lining using a segment  274  or the like is installed. 
         [0122]    The steps above enable the construction of a circular section tunnel. 
         [0123]    In the present embodiment, reaction force is not obtained from a lining such as segments, as is done in the shield construction method; rather reaction force is received by pressing support plates  256  and  258  against ground when excavating ground in an annular shape using excavating apparatus  201 , therefore a greater reaction force can be received. Hence even in ground where bedrock strength is approximately 120 to 200 MPa, such as granite, and the application of the shield construction method is difficult, excavation work can be performed using the excavating apparatus  201  of the present embodiment. 
         [0124]    Furthermore, because reaction force is taken from the ground, the excavating apparatus  201  can be propelled even if lining work using segments or the like is not completed, and construction can be efficiently carried out. 
         [0125]    In addition, when the excavating mechanism  204  is advanced toward the ground by the excavating mechanism  208 , reaction force is received by pressing against the ground using the front and rear support plates  256  and  258 , therefore a larger reaction force can be received. 
         [0126]    It is also possible to excavate the tunnel outer perimeter portion in advance and install lining, and since ground left remaining on the inside becomes a restraint on the tunnel face, stable construction is possible even in soft ground. 
         [0127]    Note that in the above-described embodiment excavated dirt taken in from the intake holes  238  in the cutter portion  226  is transported to the rear of the excavating apparatus  201  through excavated dirt discharge pipe  242 , but the invention is not limited thereto, and as shown in  FIG. 21 , may also be constituted by causing the excavated dirt intake opening  276  of the cutter portion  226  and discharge port  278  disposed on the two sides of excavating portion shell body  210  to communicate, thereby discharging excavated dirt taken in from the excavated dirt intake opening  276  to the rear through the gap between excavating portion shell body  210  and the ground; in other words, there is no restriction on the constitution for discharging excavated dirt. 
         [0128]    Furthermore, the embodiment above provided front and rear axial hydraulic jacks  248  and  250 , but the invention is not limited thereto, and it is also acceptable to provide a single axial hydraulic jack. 
         [0129]    In addition, the propelling mechanism  108  described in the second embodiment can also be used in place of the propelling mechanism  208  of the present embodiment.