Center pressure tube set

Abstract

In the internal sealing method, ensure that the seal between the inside and outside of the standard pipe is properly maintained. [Solution] Two types of sealing members (first sealing member, second sealing member) are used to seal the space between the central outer pipe and the central inner pipe. In terms of the positional relationship of the central outer pipe and the central inner pipe along the central axis direction (front-rear direction), there is a state in which the central inner pipe is at the rear (farther from the jacking pipe) (first state) and a state in which the central inner pipe is at the front (closer to the jacking pipe) (second state). The first state corresponds to the state when jacking work is being carried out, and in this state, the space between the central outer pipe and the central inner pipe is sealed only by the first sealing member and not by the second sealing member. On the other hand, the second state corresponds to the state in which the central inner pipe is moved as far forward as possible after the completion of jacking, and in this state, the space between the central outer pipe and the central inner pipe is sealed by the second sealing member.

Description

Technical Field

[0004] , , , , ,

[0003]

[0001] The present invention relates to a structure of a middle-pressing pipe set, which is composed of two types of middle-pressing pipes used in combination in the middle-pressing method in the propulsion construction for laying propulsion pipes, and a sealing member for sealing between them.

Background Art

[0002] Cylindrical fume pipes (propulsion pipes) made of reinforced concrete or the like are installed and used in the ground or the like in a state where a large number are connected in the central axis direction. At this time, when constructing a structure in which many propulsion pipes are connected horizontally from the side surface of a shaft formed in the ground, it is necessary to sequentially advance the propulsion pipe at the tip forward. For this purpose, this operation can be performed using a jack or the like. For this reason, a middle-pressing method is known in which a middle-pressing pipe is connected to the rear of the propulsion pipe in the ground, a jack or the like is installed inside the middle-pressing pipe, and the propulsion pipe is sequentially advanced by repeatedly expanding and contracting the jack.

[0003] The middle-pressing method is performed by using a middle-pressing pipe having a structure different from that of a normal propulsion pipe (standard pipe), pressurizing this with a jack, and indirectly pressurizing the standard pipe. Two types of middle-pressing pipes described later are used in combination. Since the middle-pressing pipe remains in a form attached to the standard pipe after the construction, it is shaped so as not to be an obstacle when using this standard pipe. Further, when performing the operation of advancing the propulsion pipe as described above, the space inside these and the outside are configured to be sealed so that water and mud do not enter the inside of the standard pipe or the middle-pressing pipe. Since the middle-pressing pipe remains as described above even after the construction, this sealed state needs to be permanently maintained even after the construction. Examples of specific structures for this are described in, for example, Patent Documents 1 and 2.

[0004] Figure 8 is a schematic diagram showing the overall configuration of the central pushing method. In the figure, multiple standard pipes 80 are connected and extend from a shaft S formed in the ground G toward the left in the ground. The structure of the standard pipes 80 is shown in a simplified manner here. The standard pipes 80 have a roughly cylindrical shape, and each standard pipe 80 is connected in the direction of the central axis, and in Figure 8, a cross-section along the central axis X is shown. Here, a cutting end 85 is attached to the tip of the leading (left) standard pipe 80A, and it can be advanced by applying pressure to the left in the figure. For this purpose, a central pushing mechanism 90 is provided between standard pipes 80B and 80C in the figure. The central pushing mechanism 90 is fixed to the rear standard pipe 80C and applies pressure to the front standard pipe 80B toward the front, thereby advancing the leading standard pipe 80A underground. Although not shown in Figure 8, a main pushing mechanism that pushes from the shaft S side is also provided inside the shaft S.

[0005] The center-pressing mechanism 90 is specifically composed of a front-side center-pressing outer tube (S-shaped tube), a rear-side center-pressing inner tube (T-shaped tube), and a jack sandwiched between them. When the jack extends and retracts, the center-pressing outer tube and the center-pressing inner tube slide against each other along the central axis X, and this movement advances the standard tube at the front. Figure 9 is a detailed cross-sectional view of the standard tube 80 in Figure 8, and Figures 10 and 11 are detailed cross-sectional views of the center-pressing outer tube 110 and the center-pressing inner tube 120, respectively, along the central axis X, corresponding to Figure 8. Figures 10 and 11 show the state in which the sealing member (elastic member), which will be described later, is attached.

[0006] In Figure 9, the standard pipe 80 comprises a standard pipe body 81 made of roughly cylindrical concrete (reinforced concrete) and a metal collar 82 attached to the rear so as to protrude to the rear. The outer diameter of the standard pipe body 81 and the outer diameter of the collar 82 are set to be equal. Furthermore, the leading end of the standard pipe body 81 is a slightly smaller diameter section 81A so as to be accommodated within the collar 82 of the standard pipe 80 in front of it. This allows the standard pipes 80 to be connected to each other using the collar 82 and fixed from the inside (central axis X side). Although not shown in the figure, a sealing member (sealing member) is attached to the small diameter section 81A to seal the space between the outer surface of the small diameter section 81A and the collar 82 of the standard pipe 80 in front of it, but this is not shown in the figure. As a result, soil and moisture are prevented from entering the inside of the standard pipe 80 after connection underground.

[0007] In the central outer tube 110 of Figure 10, the rear side (right side in the figure) has a cylindrical rear central tube portion 111 corresponding to the collar 82 and having the same outer diameter, while the front side has a cylindrical front central tube portion 112 corresponding to the small diameter portion 81A of the propulsion pipe body 81. Furthermore, the front side (left side in the figure) of the front central tube portion 112 has a front support portion 113 extending toward the central axis X. Viewed from the front, the front support portion 113 is formed in an annular shape centered on the central axis X. Similarly, the rear side (right side in the figure) has an annular rear support portion 114. The front central tube portion 112 and the rear central tube portion 111 are connected via the rear support portion 114. Therefore, the rear cylindrical portion 111 of the central outer pipe, the front cylindrical portion 112 of the central outer pipe, the front support portion 113 of the central outer pipe, and the rear support portion 114 of the central outer pipe are integrated and formed from metal. In addition, the space between the front support portion 113 and the rear support portion 114 of the central outer pipe is filled with concrete or the like, forming a filled portion 115.

[0008] Furthermore, a sealing member (front sealing member) 116 is attached to the outer surface of the front cylindrical portion 112 of the central outer tube, which seals the space between it and the inner surface of the collar 82 of the front standard tube 80, as will be described later. In Figure 10, the cross-sectional shape along the central axis X is shown, but in reality, the sealing member 116 is continuously formed in the circumferential direction along the outer surface of the front cylindrical portion 112 of the central outer tube.

[0009] The central inner pipe 120 in Figure 11, like the central outer pipe 110, is formed of metal with the rear cylindrical portion 121, front cylindrical portion 122, front support portion 123, and rear support portion 124 integrated into one piece. In addition, a filling portion 125 made of concrete or the like is formed between the front support portion 123 and the rear support portion 124.

[0010] A sealing member 126 is attached to the outer surface of the front cylindrical portion 122 of the central inner tube, as will be described later, to seal the space between it and the inner surface of the rear cylindrical portion 111 of the front central outer tube 110. In Figure 11, the cross-sectional shape along the central axis X is shown, but in reality, the sealing member 126 is continuously formed in the circumferential direction along the outer surface of the front cylindrical portion 122 of the central inner tube. Two sealing members 126 are provided along the direction of the central axis X, and between them, a lubricant injection hole 125A is formed, penetrating the filling portion 125 and the front cylindrical portion 122 of the central inner tube, for injecting lubricant from the inside to the outside. Note that in Figure 8, all parts except the lubricant injection hole 125A are uniformly provided around the central axis X, but in reality, multiple lubricant injection holes 125A are provided, dispersed in the circumferential direction.

[0011] Figure 12 shows the specific configuration when the standard pipe 80 is advanced using the above-mentioned central outer pipe 110 and central inner pipe 120. Here, only the parts corresponding to the portion above the central axis X in Figures 9 to 11 are described, and the small diameter portion 81A of the standard pipe 80 is omitted.

[0012] In Figure 12, the structural changes of the above-mentioned parts are shown in chronological order from top to bottom. First, as shown in Figure 12(1), the standard pipe 80 to be advanced is set in its initial position, and then, as shown in Figure 12(2), the central outer pipe 110 and central inner pipe 120 are inserted and fitted from the rear. In reality, the rear standard pipe 80 is fixed to the central inner pipe 120 with its small diameter portion 81A housed in the rear cylindrical portion 121 of the central inner pipe, or further rearward, as described above, but these are irrelevant to the present invention and are therefore omitted from the description.

[0013] Here, the front support portion 113 of the central outer pipe 110 abuts against the standard pipe body 81 of the front standard pipe 80, and a jack (pressure device) 200 and a support ring 210 are sandwiched between the rear support portion 114 of the central outer pipe 110 and the front support portion 123 of the central inner pipe 120. Here, although a simplified cross-section is shown in Figure 12, the support ring 210 has an annular shape similar to the front support portion 123 of the central inner pipe, and in reality, multiple jacks 200 are provided, evenly distributed in the circumferential direction (for example, 16). The jacks 200 expand and contract in the direction of the central axis X, but in Figure 12 (2), this is shown as the most contracted state.

[0014] In this state, by fixing the rear end of the rear central inner pipe 120 and extending the jack 200, the front standard pipe 80 (more precisely, the leading standard pipe 80A in Figure 8) can be advanced, as shown in Figure 12 (3). Subsequently, by retracting the jack 200 and advancing the central inner pipe 120, as shown in Figure 12 (4), the entire structure in Figure 12 (2) will have advanced by the amount extended by the jack 200. After that, the standard pipe 80 can be advanced further by repeating the operations in Figures 12 (3) and (4) again, as shown in Figures 12 (5) and (6). In other words, by repeating the operations in Figures 12 (3) and (4), the standard pipe 80 can be advanced to the desired position.

[0015] Subsequently, in the state shown in Figure 12 (7), where the standard pipe 80 has been advanced to the desired position, the jack 200 and the support ring 210 are removed, and the central inner pipe 120 is advanced as shown in Figure 12 (8), so that the front support portion 123 of the central inner pipe 120 comes into contact with the rear support portion 114 of the central outer pipe 110. With this state, the central outer pipe 110 and the collar 81 of the standard pipe 80 in front of it, and the central inner pipe 120 and the central outer pipe 110 can be fixed by welding or the like. Furthermore, as described above, the standard pipe 80 behind the central inner pipe 120 is fixed, so the front standard pipe 80, central outer pipe 110, central inner pipe 120, and rear standard pipe 80 are fixed in place.

[0016] Therefore, according to the construction method shown in Figure 12, the standard pipe 80 can be advanced to a predetermined position underground using the central outer pipe 110, central inner pipe 120, jack 200, etc. Although Figure 12 only shows the advancement of the leading standard pipe 80 using the central outer pipe 110 and central inner pipe 120, in reality, in the state shown in (2) of Figure 12, the standard pipe 80 connected to the rear side is advanced to a predetermined position via the rear standard pipe 80 using the main pushing mechanism in the shaft S. The leading standard pipe 80, central outer pipe 110, central inner pipe 120, etc. are advanced to a predetermined position. If it becomes difficult to advance further using the main pushing mechanism, the steps from (3) (advancement by jack 200) onwards in Figure 12 are performed. In other words, although the process shown in Figure 12 and the forward movement by the push mechanism are actually used in combination, the issue in the present invention concerns the changes in the relative positional relationship of the leading standard pipe 80, the middle push outer pipe 110, and the middle push inner pipe 120. Since these relative positional relationships do not change when the push mechanism is in operation, the following description will not cover the operation of the push mechanism. Ultimately, the middle push outer pipe 110, the middle push inner pipe 120, etc., can be used as part of a structure in which multiple standard pipes 80 are connected, together with the front and rear standard pipes 80, without being removed even after the completion of construction.

[0017] As described above, during the above construction work, in order to prevent soil and water from entering the interior of the standard pipe 80, etc. (the space on the central axis X side), a sealing member 116 is attached to the central outer pipe 110 side and a sealing member 126 is attached to the central inner pipe 120 side. In the state shown in Figure 12, the sealing member 116 seals the space between the outer surface of the front cylindrical portion 112 of the central outer pipe and the inner surface of the collar 82 of the standard pipe 80, and the sealing member 126 seals the space between the outer surface of the front cylindrical portion 122 of the central inner pipe and the inner surface of the rear cylindrical portion 111 of the central outer pipe 110. These sealing members are made of elastic material, and their elastic force seals the space between them and the surfaces they come into contact with, suppressing the intrusion of soil and water. This state in which the space on the central axis X side is sealed by the sealing members 116 and 126 is maintained even in the state shown in Figure 12 (8) after the jacking work is completed. As shown in Figures 10 and 11, these sealing members are pre-installed on the outer surface of the front cylindrical portion 112 of the central outer tube and the outer surface of the front cylindrical portion 122 of the central inner tube before installation. Conversely, the sealing member 116 may be installed on the inner surface of the collar 82, and the sealing member 126 may be installed on the inner surface of the rear cylindrical portion 111 of the central outer tube.

[0018] In the process shown in Figure 12, each sealing member is subjected to a compressive force in the vertical direction (perpendicular to the central axis X) as shown in the figure, as well as a horizontal force (along the central axis X) as the standard pipe 80, the outer central pipe 110, and the inner central pipe 120 move. For this reason, although not shown in the figure, a structure that acts as a stopper to suppress the lateral movement of these sealing members is also formed on the surface to which these sealing members are attached. [Prior art documents] [Patent Documents]

[0019] [Patent Document 1] Japanese Patent Publication No. 2014-70479 [Patent Document 2] Japanese Patent Publication No. 2012-246678 [Overview of the project] [Problems that the invention aims to solve]

[0020] In Figure 12, arrows are shown indicating the direction of the force applied to the sealing member in the horizontal direction (along the central axis X) when forming each step, as viewed from the sealing member side (the relative direction of movement of the surface that the sealing member side contacts from above). In Figure 12 (2), since the central outer tube 110 and central inner tube 120 are inserted from the rear side (right side), a force acts on the sealing member 116 towards the rear side (right side), as indicated by arrow A1 and arrow B1 on the sealing member 126. From Figure 12 (3) onward, the positional relationship between the central outer tube 110 and the standard tube 80 (collar 81) does not change, so no force is applied to the sealing member 116 in the horizontal direction from this point onward.

[0021] On the other hand, in Figure 12 (3), as the jack 200 extends, a force acts on the sealing member 126 toward the front (left side) as indicated by arrow B2, and in the subsequent (4), a force acts toward the rear (right side) as indicated by arrow B3. Figures 12 (5) and (6) are the same as Figures 12 (3) and (4). Furthermore, in the final form shown in Figure 12 (8), a force acts toward the rear (right side) as indicated by arrow B4.

[0022] In other words, in the above process, a backward force is applied to the sealing member 116 only once, while a backward and forward force is repeatedly applied to the sealing member 126 alternately. In particular, as mentioned above, the operations in (3) and (4) of Figure 12 are repeated multiple times, so this cycle is repeated many times. As a result, the effect of wear on the sealing member 116 is very small, while the effect of wear on the sealing member 126 is large, and its durability became a problem.

[0023] Figures 13(a) and (b) are cross-sectional views along the front-back direction, which show a simplified and enlarged structure of the sealing members 116 and 126 in FIGS. 10 and 11 and the structures around them. Here, the description of the structure serving as the stopper is omitted. As described above, a force directed toward the rear side (rightward) is applied to the sealing member 116 only once. In such a case, as shown in FIG. 13(a), a plurality of inclined portions 116A inclined so as to be separated from the surface to which it is attached (the outer surface of the front cylinder portion 112 of the middle-push outer tube) toward the rear side are provided, and the sealing member 116 composed of an elastic body having an asymmetric shape on the left and right can be used. Thereby, as shown in (2) of FIG. 12, the attachment to the collar 82 of the middle-push outer tube 110 becomes easy, and the elastic force acting on the inclined portion 116A makes the sealing by this strong.

[0024] On the other hand, as described above, since a horizontal force is applied to the sealing member 126 a number of times with the direction alternating, the sealing member 126 cannot have the same form as the sealing member 116. For this reason, the sealing member 126 has a symmetric shape in the front-back direction (left-right direction in the figure) as shown in FIG. 13(b). Also, two sealing members 126 are provided in the horizontal direction, and a lubricant injection hole 125A is provided between the two sealing members 126. Particularly in the steps such as (3) and (4) of FIG. 12, lubricant is injected from the inner side of the middle-push inner tube 120 to smoothly slide the sealing member 126 to facilitate the steps of FIG. 12 and suppress the deterioration of the sealing member 126.

[0025] In this case, the sealing member 126 seals between the outer surface of the inner peripheral portion 122 of the middle-push inner tube and the inner surface of the outer peripheral portion 111 of the middle-push outer tube 110 by the elastic force acting on its upper surface and lower surface. However, the sealing effect of the sealing member 126 having such a shape is smaller than that of the asymmetric sealing member 116 in which the direction of the applied force is considered as described above. Further, the number of cycles in which force is applied to the sealing member 126 may exceed 1000 times in some cases. In this case, even when the lubricant as described above is used, the sealing member 126 may deteriorate due to wear and its sealing ability may decrease.

[0026] Between the front cylinder part 122 of the inner middle pusher tube and the rear cylinder part 111 of the outer middle pusher tube, not only during construction as shown in Fig. 12, but actually also permanently sealed thereafter is required. For this reason, after taking the form of (8) in Fig. 12, considering the deterioration of the sealing member 126 at this point, an operation of sealing by welding is required over all directions around the central axis X between the front cylinder part 122 of the inner middle pusher tube and the rear cylinder part 111 of the outer middle pusher tube.

[0027] For this reason, in the middle pusher method, a technique that can surely seal between the inner side and the outside of the propulsion pipe has been demanded.

[0028] The present invention has been made in view of such a situation, and aims to solve the above problems.

Means for Solving the Problems

[0029] The present invention relates to a central pipe set used in a central pipe construction method for advancing a cylindrical standard pipe having a central axis along the front-rear direction underground, and comprises: an outer central pipe positioned behind the standard pipe and advancing the standard pipe, both having a cylindrical structure coaxial with the standard pipe; and an inner central pipe positioned behind the outer central pipe and movable along the central axis relative to the outer central pipe and advancing the outer central pipe and the standard pipe, wherein the inner central pipe has a front cylindrical portion that is coaxial with the standard pipe and faces forward, and the outer central pipe is positioned relative to the standard pipe The inner and outer pressing tubes are each provided with a rear cylindrical section of the inner pressing tube that is coaxial with the inner pressing tube and is located at the rear. A pressurizing device is provided between the inner pressing tube front support section, which is located inside the front cylindrical section of the inner pressing tube and in front of the front cylindrical section of the inner pressing tube, and the outer pressing tube rear support section, which is located inside the rear cylindrical section of the outer pressing tube and in front of the rear cylindrical section of the outer pressing tube. By pressurizing the outer pressing tube forward and the inner pressing tube rearward, the front support section of the outer pressing tube, which is located in front of the rear support section of the outer pressing tube, is provided. The part is formed to advance the standard pipe, and the central inner pipe is movable in the front-rear direction relative to the central outer pipe with respect to the central outer pipe when the front cylindrical portion of the central inner pipe is inside the rear cylindrical portion of the central outer pipe, and when the central outer pipe and the central inner pipe are assembled in the work of advancing the standard pipe, the first sealing member attached to the outer surface of the front cylindrical portion of the central inner pipe or the inner surface of the rear cylindrical portion of the central outer pipe, and when the central outer pipe and the central inner pipe are assembled in the work of advancing the standard pipe, the outer surface of the front cylindrical portion of the central inner pipe or the inner surface of the rear cylindrical portion of the central outer pipe The device is characterized in that it is provided with a second sealing member mounted in front of the first sealing member, and when the central outer tube moves in the front-rear direction relative to the central inner tube, it takes the following states: a first state in which the inner surface of the rear cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube are sealed by the first sealing member but not by the second sealing member; and a second state in which the central inner tube is positioned in front of the central outer tube relative to the central outer tube than in the first state, and the inner surface of the rear cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube are sealed by the second sealing member. In the center valve set of the present invention, the second sealing member is attached to the inner surface of the rear cylindrical portion of the center valve outer tube, and in the first state, the inner surface of the rear cylindrical portion of the center valve outer tube faces the outer surface of the front cylindrical portion of the center valve inner tube at the location where the first sealing member is present, and in the direction along the central axis, the location on the inner surface of the rear cylindrical portion of the center valve outer tube where the second sealing member is attached does not overlap with the front cylindrical portion of the center valve inner tube, and in the second state, the location on the inner surface of the rear cylindrical portion of the center valve outer tube where the second sealing member is attached faces the outer surface of the front cylindrical portion of the center valve inner tube. In the center-pressure tube set of the present invention, the second sealing member is attached to the outer surface of the front cylindrical portion of the center-pressure inner tube, the rear cylindrical portion of the center-pressure outer tube comprises a first cylindrical portion of the center-pressure outer tube provided on the rear side and having an inner diameter larger than the outer diameter of the front cylindrical portion of the center-pressure inner tube, and a second cylindrical portion of the center-pressure outer tube provided on the front side and having an inner diameter smaller than the first cylindrical portion of the center-pressure outer tube and an inner diameter larger than the outer diameter of the front cylindrical portion of the center-pressure inner tube, the second sealing member is thinner than the first sealing member in the radial direction as viewed from the central axis, and in the first state, the inner surface of the first cylindrical portion of the center-pressure outer tube and the center-pressure tube are connected at the location of the first sealing member. The outer surface of the front cylindrical portion of the inner tube faces the inner surface of the first cylindrical portion of the center-relief outer tube, and the space between the inner surface of the front cylindrical portion of the center-relief inner tube and the outer surface of the front cylindrical portion of the center-relief inner tube is sealed by the first sealing member, and the space between the inner surface of the front cylindrical portion of the center-relief inner tube where the second sealing member is attached and the inner surface of the first cylindrical portion of the center-relief outer tube is not sealed by the second sealing member, and in the second state, the space between the outer surface of the front cylindrical portion of the center-relief inner tube where the second sealing member is attached faces the inner surface of the second cylindrical portion of the center-relief outer tube, and the space between the outer surface of the front cylindrical portion of the center-relief inner tube and the inner surface of the second cylindrical portion of the center-relief outer tube is sealed by the second sealing member. The present invention is characterized in that the second state is achieved when the rear support portion of the outer center tube and the front support portion of the inner center tube are brought into contact with each other. In the central pressure tube set of the present invention, the second sealing member is characterized in that, on the surface opposite to the side with the central axis, it has an inclined portion that is inclined so as it moves from front to rear, it moves away from the surface to which the second sealing member is attached. In the central pressure tube set of the present invention, the second sealing member is made of an elastic material and is characterized in that, located behind the inclined portion, on the side opposite to the side to which the second sealing member is attached, the rear sealing portion has a surface that is arc-shaped in cross-sectional shape along the front-rear direction when no force is applied. [Effects of the Invention]

[0030] According to the present invention, in the central thrust method, reliable sealing can be achieved between the inside and outside of the jacking pipe. [Brief explanation of the drawing]

[0031] [Figure 1] This is a cross-sectional view along the central axis showing the structure of the outer center pressure tube in the center pressure tube set according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view along the central axis showing the structure of the central inner tube in the central pressure tube set according to the first embodiment of the present invention. [Figure 3] This is a cross-sectional view showing the configuration of a tunnel jacking construction project in which the central push pipe set according to the first embodiment of the present invention is used. [Figure 4] This is a cross-sectional view along the central axis showing the structure of the outer center pressure tube in the center pressure tube set according to the second embodiment of the present invention. [Figure 5] This is a cross-sectional view along the central axis showing the structure of the central inner tube in a central pressure tube set according to a second embodiment of the present invention. [Figure 6] This is a cross-sectional view showing the configuration of a tunnel jacking construction project in which the central pipe set according to the second embodiment of the present invention is used. [Figure 7] This is a cross-sectional view showing a modified structure of the second sealing member used in the center pressure tube set according to the second embodiment of the present invention. [Figure 8] This diagram shows an overview of the underground thrusting method used to advance jacking pipes underground. [Figure 9] This is a cross-sectional view along the central axis, showing the structure of the propulsion pipe. [Figure 10]This is a cross-sectional view along the central axis showing the structure of the outer center cap in a conventional center cap set. [Figure 11] This is a cross-sectional view along the central axis showing the structure of the central inner tube in a conventional central tube set. [Figure 12] This is a cross-sectional view showing the configuration of a conventional central pipe set used in pipe jacking construction. [Figure 13] This is a cross-sectional view showing two types of shapes in the sealing member. [Modes for carrying out the invention]

[0032] The central thrust pipe set according to an embodiment of the present invention consists of a central thrust outer pipe (S-shaped pipe) positioned behind the standard pipe to be advanced in the central thrust method, a central thrust inner pipe (T-shaped pipe) positioned behind the central thrust outer pipe, and a sealing material (sealing member) that seals the space between them. When the jack provided between the central thrust outer pipe and the central thrust inner pipe expands and contracts, the central thrust outer pipe and the central thrust inner pipe slide against each other along the central axis X, and this movement allows the standard pipe in front to be advanced. This central thrust pipe set remains even after the pipe jacking work is completed and becomes part of the structure to which the standard pipe is connected. The above points are the same as when using the conventional central thrust outer pipe 110, central thrust inner pipe 120, etc.

[0033] However, in the central pipe set according to the embodiment of the present invention, two types of sealing members (first sealing member, second sealing member) are used to seal the space between the central outer pipe and the central inner pipe. Here, the first sealing member corresponds to the sealing member 126 described above, and its function is the same. In contrast, here a second sealing member is newly provided on the forward side of the first sealing member, and the main sealing member used to seal the space between the central outer pipe and the central inner pipe differs depending on the positional relationship between the central outer pipe and the central inner pipe. As a result, the space inside the standard pipe, etc., is consistently and firmly sealed from the outside from the start to the end of the pipe jacking work. Here, "sealed" by the second sealing member between the central outer pipe and the central inner pipe means that water, soil, etc., are prevented from entering the inside of the central outer pipe and the central inner pipe (the side with the central axis X) through the gap between the central outer pipe and the central inner pipe. Therefore, if the second sealing member is in light contact with the central outer tube or central inner tube to the extent that this intrusion is not suppressed, or if the second sealing member is in contact with the central outer tube or central inner tube only on a portion of the circumference around the central axis X, then the space between the central outer tube and the central inner tube will not be "sealed" by the second sealing member.

[0034] Here, the central outer pipe and central inner pipe have two positional relationships along their central axis (front-to-back direction): a first state where the central inner pipe is at the rear (farther from the jacking pipe) and a second state where the central inner pipe is at the front (closer to the jacking pipe). The first state corresponds to the state during jacking work, in which case the space between the central outer pipe and central inner pipe is sealed only by the first sealing member and not by the second sealing member. On the other hand, the second state corresponds to the state after the completion of jacking when the central inner pipe is at its furthest forward position, in which case the space between the central outer pipe and central inner pipe is sealed by the second sealing member. In this state, the space between them may also be sealed by the first sealing member, but even if the sealing by the first sealing member is insufficient due to deterioration at this point, the space between them is reliably sealed by the second sealing member. The central outer pipe, central inner pipe, first sealing member, and second sealing member are configured to achieve these functions. In the following, we will describe a first embodiment in which the second sealing member is attached to the outer tube side of the center retainer, and a first embodiment in which the second sealing member is attached to the inner tube side of the center retainer, as examples of configurations for this purpose.

[0035] (First Embodiment) In the central push pipe set according to the first embodiment, the second sealing member is attached to the inner surface of the central push outer pipe. Figure 1(a) is a cross-sectional view along the central axis X with the front sealing member and the second sealing member attached to the central push outer pipe (S-shaped pipe) 10, and Figure 1(b) is an enlarged view of the second sealing member and its surroundings. Figure 2 is a cross-sectional view along the central axis X with the first sealing member attached to the central push inner pipe (T-shaped pipe) 20. Figures 1(a) and 2 correspond to Figures 10 and 11, respectively. The structure of the standard pipe 80 to be advanced here is as shown in Figure 9.

[0036] In the central outer tube 10 of Figure 1, there is a rear central outer tube section 11 and a front central outer tube section 12, both of which are cylindrical with the central axis X as their central axis. Furthermore, there is a front central outer tube support section 13 on the front side (left in the figure) and a rear central outer tube support section 14 on the rear side (right in the figure), both of which are annular in shape with the central axis X as their central axis. The same applies to the fact that the rear central outer tube section 11, the front central outer tube section 12, the front central outer tube support section 13, and the rear central outer tube support section 14 are integrated and formed from metal. In addition, the space between the front central outer tube support section 13 and the rear central outer tube support section 14 is a filled section 15 filled with concrete or the like.

[0037] Furthermore, a sealing member (front sealing member) 16 is attached to the outer surface of the front cylindrical portion 12 of the central outer tube, which seals the space between it and the inner surface of the collar 82 of the front standard tube 80, as will be described later. The sealing member 16 has the same shape as the sealing member 116 described above (Figure 10(a)).

[0038] Similar to the internal pipe 120 in Figure 2, the internal pipe 20 is also formed from metal, with the rear cylindrical section 21, front cylindrical section 22, front support section 23, and rear support section 24 being integrated into one piece. Furthermore, a filling section 25 made of concrete or the like is formed between the front support section 23 and the rear support section 24. As with the internal pipe 120 and the external pipe 110, the front cylindrical section 22 of the internal pipe 20 moves inside the rear cylindrical section 11 of the external pipe 10 during pipe jacking work.

[0039] Here, a sealing member (first sealing member) 26 is attached to the outer surface near the center along the central axis X direction (front-to-back direction) of the front cylindrical portion 22 of the central inner tube. In Figure 2, two sealing members 26 are formed, and, similar to the central inner tube 120, a lubricant injection hole 25A is provided between the two sealing members 26. The sealing member 26 has the same shape as the sealing member 126 (Figure 13(b)). In this central inner tube 20, the sealing member 26 and the lubricant injection hole 25A are located further rearward (to the right in the figure) compared to the central inner tube 120 in Figure 11.

[0040] On the other hand, in Figure 1, a sealing member (second sealing member) 27 is attached to the inner surface of the rear cylindrical portion 11 of the central outer tube 10. As shown in Figure 1(b), the sealing member 27 has multiple inclined portions 27A, similar to the sealing member 116. However, unlike the sealing member 116, the sealing member 27 is attached to the inner surface (upper side in the figure) of the rear cylindrical portion 11 of the central outer tube, so the inclined portions 27A are inclined toward the front so as to be spaced apart from the surface to which they are attached (the inner surface of the rear cylindrical portion 11 of the central outer tube). This makes it easier to insert the front cylindrical portion 22 of the central inner tube into the rear cylindrical portion 11 of the central outer tube, and also strengthens the seal between them by the sealing member 27.

[0041] Figure 3 shows the situation when the standard pipe 80 is advanced using the center-press outer pipe 10 and center-press inner pipe 20 described above, corresponding to Figure 12. That is, as shown in Figure 3(1), after the standard pipe 80 to be advanced is set in its initial position, the center-press outer pipe 10 and center-press inner pipe 20 are inserted and fitted from the rear, as shown in Figure 3(2). Here, the front support portion 13 of the center-press outer pipe 10 abuts against the standard pipe body 81 of the front standard pipe 80, and a jack 200 and a support ring 210 are sandwiched between the rear support portion 14 of the center-press outer pipe 10 and the front support portion 23 of the center-press inner pipe 20. In Figure 3(2), the jack 200 is shown in its most retracted state. The description regarding the rear standard pipe 80 and the operation of the main push mechanism are omitted, as in Figure 12.

[0042] In this state, by fixing the rear end of the rear central retaining tube 20 and extending the jack 200, the forward jacking pipe 80 can be advanced as shown in Figure 3 (3). Subsequently, by retracting the jack 200 and advancing the central retaining tube 20 as shown in Figure 3 (4), the entire structure shown in Figure 3 (2) will have advanced by the amount extended by the jack 200. After that, by repeating the operations in Figure 3 (3) and (4) again, as shown in Figure 3 (5) and (6), the jacking pipe 80 can be advanced further, and by repeating the operations in Figure 3 (3) and (4), the jacking pipe 80 can be advanced to a predetermined position. Subsequently, in the state shown in Figure 3 (7), where the jack 200 and the support ring 210 are removed to further advance the central inner pipe 20, and with the central inner pipe front support portion 23 of the central inner pipe 20 in contact with the central outer pipe rear support portion 14 of the central outer pipe 10, as shown in Figure 3 (8), the central outer pipe 10 and the collar 82 of the jack 80 in front of it, and the central inner pipe 20 and the central outer pipe 10 can be fixed by welding or the like.

[0043] In the states shown in Figure 3 (2) to (7), the inner surface of the rear cylindrical portion 11 of the central outer tube and the outer surface of the front cylindrical portion 22 of the central inner tube face each other, and the space between them is sealed by the sealing member 26. This state is the same as in Figure 12 (2) to (7). Therefore, in Figure 3 (2) to (7), as in Figure 12 (2) to (7), forces as indicated by arrows B2 and B3 are repeatedly applied, and the sealing member 26 may deteriorate due to wear.

[0044] On the other hand, in this state, the sealing member 27 is located in the space between the rear support portion 14 of the central outer pipe and the front support portion 23 of the central inner pipe, where the jack 200 and the support ring 210 are provided. Therefore, the space between the central outer pipe 10 and the central inner pipe 20 is not sealed by the sealing member 27. Furthermore, if the jack 200 and the support ring 210 are installed so that the sealing member 27 does not come into contact with them, the only place the sealing member 27 directly contacts is the inner surface of the rear cylindrical portion 11 of the central outer pipe. For this reason, in states (2) to (7) of Figure 3, no deterioration occurs in the sealing member 27.

[0045] In other words, in Figures 3(2) to (7), the inner surface of the rear cylindrical portion 11 of the central outer tube and the outer surface of the front cylindrical portion 22 of the central inner tube face each other, and the space between them is sealed by the sealing member 26, while the space between them is not sealed by the sealing member 27, thus realizing a first state.

[0046] On the other hand, in state (8) of Figure 3, the jack 200 and the support ring 210 are removed, and the inner pipe 20 is further forward than in state (7) of Figure 3 so that the front support portion 23 of the inner pipe and the rear support portion 14 of the outer pipe come into contact. In this state, the space between the inner surface of the rear cylindrical portion 11 of the outer pipe and the outer surface of the front cylindrical portion 22 of the inner pipe is sealed by the sealing member 26, which is the same as in states (2) to (7) of Figure 3. However, in this state, the sealing member 26 may be deteriorated due to wear.

[0047] In contrast, in state (8) of Figure 3, as the front cylindrical portion 22 of the central inner tube moves forward, the location on the inner surface of the rear cylindrical portion 11 of the central outer tube where the sealing member 27 is attached faces the outer surface of the front cylindrical portion 22 of the central inner tube, and the space between them is sealed by the sealing member 27. When transitioning from state (7) of Figure 3 to state (8) of Figure 3, a force directed to the right in the figure is applied to the sealing member 27, as indicated by arrow C1 in Figure 3 (8), but this force is applied to the sealing member 27 only once. Therefore, in state (8) of Figure 3, the space between the inner surface of the rear cylindrical portion 11 of the central outer tube and the outer surface of the front cylindrical portion 22 of the central inner tube is reliably sealed by the sealing member 27, which has not deteriorated. Therefore, even if deterioration occurs in the sealing member 26 at this point as described above, the space between the inner surface of the rear cylindrical portion 11 of the central outer tube and the outer surface of the front cylindrical portion 22 of the central inner tube is reliably sealed. In this case, the only force applied to the sealing member 27 is the force indicated by arrow C1 in (8) of Figure 3. Therefore, a sealing member 27 with a shape similar to the sealing member 116 (Figure 13(a)) above, which is asymmetrical in the front-to-back direction and has high sealing properties, can be used.

[0048] In other words, in Figure 3(8), a second state is achieved in which the inner surface of the rear cylindrical portion 11 of the central outer tube and the outer surface of the front cylindrical portion 22 of the central inner tube face each other, and the space between them is sealed by the sealing member 27.

[0049] Furthermore, the fact that the space between the jacking pipe 80 and the central outer pipe 10 is reliably sealed by the sealing member 16 is the same as in the case of Figure 12. Therefore, in Figures 3(2) to (8), the space inside the jacking pipe 80, the central outer pipe 10, and the central inner pipe 20 is always sealed from the outside. As a result, welding work (for example, welding around the entire circumference) to seal the space between the front cylindrical portion of the central inner pipe and the rear cylindrical portion of the central outer pipe by welding afterwards becomes unnecessary.

[0050] The operations performed in the process shown in Figure 3 are essentially the same as those performed in the process shown in Figure 12 using a conventional central pipe, except for the use of different central outer pipes, central inner pipes, and sealing members. Therefore, the above-mentioned pipe jacking work can be easily carried out.

[0051] In addition, similar to the sealing member 27 mounted on the inner surface of the rear cylindrical portion 11 of the central outer tube, the sealing member 26 may be mounted on the inner surface of the rear cylindrical portion 11 of the central outer tube further back than the sealing member 27. In this case as well, the operation shown in Figure 3 remains substantially unchanged.

[0052] (Second Embodiment) In the central push pipe set according to the second embodiment, the second sealing member is attached to the outer surface of the central push inner pipe. Figure 4 is a cross-sectional view along the central axis X with the front sealing member attached to the central push outer pipe (S-shaped pipe) 30. Figure 5(a) is a cross-sectional view along the central axis X with the first sealing member and the second sealing member attached to the central push inner pipe 40, and Figure 5(b) is an enlarged view of both sealing members and their surroundings. Figures 4 and 5(a) correspond to Figures 10 and 11, respectively. The structure of the standard pipe 80 to be advanced here is the same as described above.

[0053] In the central outer tube 30 of Figure 4, both are cylindrical with the central axis X as their central axis, and are provided with a rear central outer tube rear cylindrical portion 31 on the rear side and a front central outer tube front cylindrical portion 32 on the front side. Similarly, a front central outer tube front support portion 33 is provided on the front side (left in the figure) of the front central outer tube front cylindrical portion 32, and a rear central outer tube rear support portion 34 is provided on the rear side (right in the figure). The same applies to the fact that the central outer tube rear cylindrical portion 31, central outer tube front cylindrical portion 32, central outer tube front support portion 33, and central outer tube rear support portion 34 are integrally formed from metal. The same also applies to the filling portion 15 between the central outer tube front support portion 33 and the central outer tube rear support portion 34. The same also applies to the fact that a sealing member (front sealing member) 16 is attached to the outer surface of the central outer tube front cylindrical portion 32.

[0054] The central retaining tube 40 in Figure 5(a) is formed from metal, with the rear cylindrical portion 41, front cylindrical portion 42, front support portion 43, and rear support portion 44 being integrated, similar to the central retaining tube 20. A filling portion 25 made of concrete or the like and a lubricant injection hole 25A are provided between the front support portion 43 and the rear support portion 44. The sealing member (first sealing member) 46 is also provided in the same manner as the central retaining tube 20.

[0055] In Figure 4, the rear cylindrical portion 31 of the central outer tube is formed by connecting the rear central outer tube first cylindrical portion 31A and the front central outer tube second cylindrical portion 31B. The inner diameter of the central outer tube second cylindrical portion 31B is set to be smaller than the inner diameter of the central outer tube first cylindrical portion 31A. Therefore, a step is formed on the inner surface of the rear cylindrical portion 31 of the central outer tube such that the inner diameter on the front side is smaller (narrower) than the inner diameter on the rear side. Since the inner diameter of the central outer tube second cylindrical portion 31B is set to be larger than the outer diameter of the central inner tube front cylindrical portion 42, the central inner tube front cylindrical portion 42 can be moved along the central axis X direction inside the central outer tube rear cylindrical portion 31.

[0056] Furthermore, in Figure 5(a), a sealing member (second sealing member) 47 corresponding to the sealing member 27 is attached to the outer surface of the front cylindrical portion 42 of the central inner tube, in front of the sealing member 46. That is, here the sealing member (second sealing member) 47 is attached to the central inner tube 40 side together with the sealing member (first sealing member) 46.

[0057] Figure 5(b) is an enlarged view of the sealing members 46 and 47 and their surroundings in Figure 5(a). As described above, both sealing members 46 and 47 are made of elastic material, but the state in Figure 5(b) shows them mounted on the outer surface of the front cylindrical portion 42 of the inner retaining tube and no external force acting from anywhere other than this outer surface. As shown in Figure 5(b), the sealing member 47, like the sealing member 27, is equipped with multiple inclined portions 47A. However, unlike the sealing member 27, the sealing member 47 is mounted on the outer surface side (lower side in the figure) of the front cylindrical portion 42 of the inner retaining tube, so the inclined portions 47A are inclined toward the rear so as to be separated from the surface to which they are mounted (the outer surface of the front cylindrical portion 42 of the outer retaining tube). This makes it easier to insert the front cylindrical portion 42 of the inner retaining tube into the rear cylindrical portion 31 of the outer retaining tube, and also strengthens the seal between them by the sealing member 47.

[0058] As shown in the figure, the cross-sectional shapes of the sealing members 46 and 47 are different, but here, the thickness T2 of the sealing member 47 (the radial thickness viewed from the central axis X side: the maximum height along the vertical direction (radial direction viewed from the central axis X) in Figure 5(b)) is set to be smaller than the thickness T1 of the sealing member 46. This makes it possible to achieve a state in which the space between the inner surface of the rear cylindrical portion 31 of the central outer tube and the outer surface of the front cylindrical portion 42 of the central inner tube is sealed only by the sealing member 46 and not by the sealing member 47.

[0059] Figure 6 shows the situation when the standard pipe 80 is advanced using the above-described center-relief outer pipe 30 and center-relief inner pipe 40, corresponding to Figures 12 and 3. Here, as in the case of Figure 3, in Figures 6(2) to (7), the inner surface of the rear cylindrical portion 31 of the center-relief outer pipe and the outer surface of the front cylindrical portion 42 of the center-relief inner pipe face each other. In particular, in this case, the inner surface of the rear-side first cylindrical portion 31A of the center-relief outer pipe, which has a larger inner diameter, faces the outer surface of the front cylindrical portion 42 of the center-relief inner pipe.

[0060] In this section, both sealing members 46 and 47 are present, but their thicknesses T1 and T2 are set such that the inner surface of the first cylindrical portion 31A of the central outer tube and the outer surface of the front cylindrical portion 42 of the central inner tube are sealed only by the sealing member 46, and not by the sealing member 47 (the inner surface of the first cylindrical portion 31A of the central outer tube and the sealing member 47 do not come into contact).

[0061] Therefore, in Figures 6(2) to (7), the inner surface of the first cylindrical portion 31A of the rear central outer tube and the outer surface of the front cylindrical portion 42 of the central inner tube face each other, and the space between them is sealed by the sealing member 46, while the space between them is not sealed by the sealing member 47, thus realizing a first state.

[0062] On the other hand, in state (8) of Figure 6, the central inner tube 40 is further forward than in state (7) of Figure 6, so the inner surface of the front cylindrical portion 42 of the central inner tube at the location where the sealing member 47 provided at the front is attached faces the front side of the second cylindrical portion 31B of the central outer tube. At this time, the thickness T2 of the sealing member 47 is set so that it can seal the space between them (the inner surface of the second cylindrical portion 31B of the central outer tube and the sealing member 47 come into contact). As a result, in state (8) of Figure 6, the space between the rear cylindrical portion 31 of the central outer tube and the front cylindrical portion 42 of the central inner tube is sealed by the sealing member 47.

[0063] Therefore, in Figure 6(8), the inner surface of the front outer center pipe second cylindrical portion 31B and the outer surface of the front inner center pipe front cylindrical portion 42 face each other, and a second state is achieved in which the space between them is sealed by the sealing member 47. In the state of Figure 6(8), the sealing member 46 may be deteriorated due to wear, as in the case of Figure 3. In this case as well, by achieving the second state in this way, the space between the outer center pipe 30 and the inner center pipe 40 is consistently sealed in the states of Figure 6(2) to (8). It is also clear that in this case, the sealing member 46 may be attached to the inner surface of the first outer center pipe first cylindrical portion 31A.

[0064] In the above example, in the first state (Figure 6(2) to (7)), the sealing member 47 does not come into contact with the inner surface of the first cylindrical portion 31A of the central outer tube. However, for example, the upper end of the sealing member 47 in Figure 5(b) may be set to lightly contact the inner surface of the first cylindrical portion 31A of the central outer tube in this state. In this case, the sealing by the sealing member 47 in this state will be insufficient, but the deterioration of the sealing member 47 in steps 6(2) to (7) can be reduced to a negligible degree, and the sealing by the sealing member 47 can be firmly achieved in state 6(8).

[0065] Figure 7 shows the shape of a modified sealing member 48, which is a modified version of the sealing member (second sealing member) 47, in correspondence with Figure 13(a). This sealing member 48 is made of an elastic material, and the shape shown here is when no force is applied (it does not come into contact with the inner retaining tube 30). In this case as well, two of the inclined portions 48A are provided. At this time, a cavity 48B is formed on the lower side (towards the front cylindrical portion 42 of the inner retaining tube) to facilitate deformation near the inclined portion 48A at the stage of Figure 6(8) when the inner retaining tube 40 is fixed to the outer retaining tube 30.

[0066] Furthermore, in order to further firmly seal the space between the second cylindrical portion 31B of the central outer pipe and the front cylindrical portion 42 of the central inner pipe after fixing, a rear sealing portion 48C is provided at the rear in the cross-section shown in Figure 7, with the upper surface (opposite the front cylindrical portion 42 of the central inner pipe) having a substantially arc shape. When inserting the front cylindrical portion 42 of the central inner pipe into the second cylindrical portion 31B of the central outer pipe, the rear sealing portion 48C comes into contact with the inner surface of the second cylindrical portion 31B of the central outer pipe after the inclined portion 48A. Therefore, even if foreign matter is present on the inner surface of the second cylindrical portion 41B of the central outer pipe, it is removed by the inclined portion 48A in front of it, thereby preventing the rear sealing portion 48C from being affected. As a result, the sealing member 48 makes it possible to further ensure and firmly seal the space between the central outer pipe 30 and the central inner pipe 40 after installation. Note that a similar sealing member may be used to connect standard pipes 80 together. Furthermore, a second sealing member having a structure in which the structure of Figure 7 is reversed vertically and horizontally in the figure may be used in the first embodiment described above.

[0067] In the above example, the standard tube, inner tube, and inner tube were assumed to be approximately cylindrical in shape (with a circular cross-section perpendicular to the central axis X). However, as long as these can be combined in the same manner as described above, their cross-sectional shapes are arbitrary. In this case as well, it is clear that the same positional relationship between the inner and outer surfaces can be achieved, and the same sealing members can be used.

[0068] Furthermore, in the above example, the pressurization of the central outer pipe and central inner pipe during the jacking work was performed by jacks, etc., between the rear support part of the central outer pipe and the front support part of the central inner pipe. However, the structure for this purpose can be appropriately set for the central outer pipe and central inner pipe. In addition, although the rear support part of the central outer pipe and the front support part of the central inner pipe were assumed to be annular in shape when viewed from the front-rear direction, their shapes can be appropriately set as long as they have a surface perpendicular to the central axis so as to realize the process shown in Figures 3 and 6, and as long as they can be formed integrally with the other parts.

[0069] The present invention has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of these components, and that such modifications also fall within the scope of the present invention. [Explanation of Symbols]

[0070] 10, 30, 110 Medium extrusion tube (S type tube) 11, 31, 111 Rear cylindrical part of inner extrusion tube 12, 32, 112 Front tube part of inner push-out tube 13, 33, 113 Front support part of inner extrusion tube 14, 34, 114 Rear support part of inner extrusion tube 15, 25, 115, 125 Filling section 16, 116 Sealing member (front sealing member) 20, 40, 120 Medium inner tube (T type tube) 21, 41, 121 Rear cylinder part of inner inner tube 22, 42, 122 Front section of inner tube 23, 43, 123 Front support part of inner tube 24, 44, 124 Middle push inner tube rear support part 25A, 125A Lubricant injection port 26, 46 Sealing member (first sealing member) 27, 47, 48 Sealing member (second sealing member) 31A Inner push outer tube 1st cylindrical part 31B Middle extrusion outer tube 2nd cylinder part 27A, 47A, 48A, 116A Slope 48B Cavity 48C Rear sealing part 80, 80A~80C standard tube 81 Standard pipe body 81A Small diameter section 82 Colors 85 Blade mouth 90 Middle push mechanism 126 Sealing member 200 Jack (Pressurizing device) 210 Reinforcement ring G Ground S Shaft X center axis

Claims

1. A push pipe set used in a push pipe method for advancing a cylindrical standard pipe having a central axis along the front-to-back direction underground, comprising: a push pipe outer pipe positioned behind the standard pipe and advancing the standard pipe, both having a cylindrical structure coaxial with the standard pipe; and a push pipe inner pipe positioned behind the push pipe outer pipe and movable along the central axis relative to the push pipe outer pipe and advancing the push pipe outer pipe and the standard pipe, The aforementioned inner center tube is provided with a front cylindrical portion of the inner center tube that is coaxial with the standard tube, facing forward, and the aforementioned outer center tube is provided with a rear cylindrical portion of the outer center tube that is coaxial with the standard tube, facing rear. In the central inner tube, a central inner tube front support portion is provided on the inside side of the central inner tube front cylindrical portion and in front of the central inner tube front cylindrical portion, and in the central outer tube, a central outer tube rear support portion is provided on the inside side of the central outer tube rear cylindrical portion and in front of the central outer tube rear cylindrical portion. By pressurizing the central outer tube forward and the central inner tube rearward, the central outer tube front support portion, provided in front of the central outer tube rear support portion in the central outer tube, is formed to advance the standard tube. The inner center tube is movable in the front-rear direction relative to the outer center tube while the front cylindrical portion of the inner center tube is inside the rear cylindrical portion of the outer center tube. In the construction work to advance the standard pipe, when the central outer pipe and the central inner pipe are assembled, the first sealing member is attached to the outer surface of the front cylindrical portion of the central inner pipe or the inner surface of the rear cylindrical portion of the central outer pipe, In the construction work to advance the standard pipe, when the central outer pipe and the central inner pipe are assembled, a second sealing member is attached in front of the first sealing member on the outer surface of the front cylindrical portion of the central inner pipe or on the inner surface of the rear cylindrical portion of the central outer pipe, A system was established, When the outer center tube moves in the front-rear direction relative to the inner center tube, In a first state, the inner surface of the rear cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube are sealed by the first sealing member but not by the second sealing member, In the second state, the central inner tube is positioned further forward than the central outer tube compared to the first state, and the inner surface of the rear cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube are sealed by the second sealing member. A central pressure tube set characterized by being configured to take a specific position.

2. The second sealing member is attached to the inner surface of the rear cylindrical portion of the central outer tube, In the first state described above, at the location where the first sealing member is present, the inner surface of the rear cylindrical portion of the central outer tube faces the outer surface of the front cylindrical portion of the central inner tube, and in the direction along the central axis, the location on the inner surface of the rear cylindrical portion of the central outer tube where the second sealing member is attached does not overlap with the front cylindrical portion of the central inner tube. The center valve set according to claim 1, characterized in that, in the second state, the portion on the inner surface of the rear cylindrical portion of the center valve outer valve where the second sealing member is attached faces the outer surface of the front cylindrical portion of the center valve inner valve.

3. The second sealing member is attached to the outer surface of the front cylindrical portion of the central inner tube, The rear cylindrical portion of the central outer tube comprises a first cylindrical portion of the central outer tube provided on the rear side, having an inner diameter larger than the outer diameter of the front cylindrical portion of the central inner tube, and a second cylindrical portion of the central outer tube provided on the front side, having an inner diameter smaller than the first cylindrical portion of the central outer tube and an inner diameter larger than the outer diameter of the front cylindrical portion of the central inner tube. In the radial direction as viewed from the central axis, the second sealing member is made thinner than the first sealing member. In the first state described above, the inner surface of the first cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube face each other at the location where the first sealing member is located, and the space between the inner surface of the first cylindrical portion of the central outer tube and the outer surface of the front cylindrical portion of the central inner tube is sealed by the first sealing member, and the location on the inner surface of the front cylindrical portion of the central inner tube where the second sealing member is attached and the inner surface of the first cylindrical portion of the central outer tube are not sealed by the second sealing member. The center valve set according to claim 1, characterized in that, in the second state, the location on the outer surface of the front cylindrical portion of the center valve where the second sealing member is attached faces the inner surface of the second cylindrical portion of the center valve outer pipe, and the space between the outer surface of the front cylindrical portion of the center valve inner pipe and the inner surface of the second cylindrical portion of the center valve outer pipe is sealed by the second sealing member.

4. The center-pressing tube set according to claim 2 or 3, characterized in that the second state is achieved when the rear support portion of the center-pressing outer tube and the front support portion of the center-pressing inner tube are brought into contact with each other.

5. The central pressure pipe set according to claim 1, characterized in that the second sealing member has an inclined portion on the surface opposite to the side with the central axis that is inclined to move away from the surface to which the second sealing member is attached as it extends from front to rear.

6. The second sealing member is made of an elastic material and is located behind the inclined portion, The center cap set according to claim 5, further comprising a rear sealing portion having an arc-shaped surface in the cross-sectional shape along the front-rear direction when no force is applied, on the side opposite to the side to which the second sealing member is attached.

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