JP2004156247A - Directional correction method for immersed tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of a rubber gasket while developing the feature of an in-tube wedge type dimensional correction device. <P>SOLUTION: A wedge device which wedges vertically a fixing wedge 24 and a movable wedge 26 is arranged in the connection part of the right and left side walls of an existing tube 10 and a newly settled tube 11 and after the newly settled tube 11 is abutted against the existing tube 10 through the rubber gasket 12, a hermetically sealed chamber 18 between bulkheads is drained and the newly settled tube 11 is connected with hydraulic pressure to the existing tube 10 while sharing a load to the rubber gasket 12 and the right and left wedge devices. Next, water is injected between the bulkheads to push back the newly settled tube 11 by the reaction of the rubber gasket 12. In this state, the left or right movable wedge 26 is moved by a necessary distance to correct a shift of the rear end of the newly settled tube 11. Thereafter, the newly settled tube 11 is connected again by hydraulic pressure to the existing tube 10 while sharing a load to the rubber gasket 12 and right and left wedge devices. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for laying down a buried box for a buried tunnel, and more particularly to a method for correcting a direction of a buried box for correcting a horizontal displacement of a rear end of a new box with respect to a tunnel normal.
[0002]
[Prior art]
Conventionally, in the submerged box submerging method, the submerged box (new box) is settled, and its end face is abutted to the existing box via a rubber gasket. The new box is hydraulically joined to the existing box using the water pressure applied to the back of the box.
In such a submerged box submerging method, the direction of the new box is often shifted from the normal line of the tunnel due to various factors such as an installation error of the new box, a dimensional error of the submerged box, and a dimensional error of the rubber gasket. For this reason, conventionally, after the above-mentioned hydraulic joining, the bulkhead on the joining side was removed and detailed surveying (including surveying inside the box) was performed, and the horizontal displacement of the rear end of the new box from the tunnel normal was measured. Measured, if this deviation is larger than expected, insert a direction correction jack (hydraulic jack) between the end face of the new box and the existing box, and push back the right or left side of the new box to correct the direction I was trying to do it.
However, according to the conventional method of correcting the direction of a submerged box as described above, it is necessary to push back the newly installed box against a large load due to water pressure, so a large number of large hydraulic jacks are required, and it takes a long time to install them. However, there is a problem that the entire construction period is extended because the jack cannot be removed before the backfilling is completed.
[0003]
Therefore, for example, in Patent Document 1, a plurality of pairs of stoppers are fixed oppositely to the outer wall surfaces of the left and right side walls of the existing box and the new box, and between the wedge mating surfaces provided on the opposing surfaces of each pair of stoppers. The wedge (movable wedge) placed on the jack is supported by a jack so as to be movable in the normal direction of the outer wall surface, and the amount of drainage during hydraulic joining is adjusted, or water is injected between the bulkheads after the hydraulic joining to load by hydraulic pressure. A direction correcting device and method for moving the movable wedge by a jack while reducing the wobble have been proposed.
[0004]
[Patent Document 1]
JP-A-10-88597
[Problems to be solved by the invention]
However, according to the apparatus and method for correcting the direction of a buried box described in Patent Document 1, since a wedge device including a bracket and a movable wedge is arranged so as to protrude from a side surface of a buried box (a new box or an existing box), These are obstacles to the navigation of the buried box and the submersion work. In particular, in order to fine-tune the return amount of the new box to increase the accuracy of direction correction (in units of several mm), the wedge angle (wedge mating surface inclination angle) must be set to a small value. In addition to the need for a long device, jacks with a large stroke length are required, and these will protrude largely to the side of the buried box (new or existing box) as an obstacle.
[0006]
Therefore, the present inventors have moved a wedge device that vertically wedges a fixed wedge and a movable wedge to an inner portion of a rubber gasket at a joint between left and right side walls of an existing box and a new box, and moves the movable wedge. The present inventors have devised a direction correcting device provided with a driving device to be driven, and have already disclosed it in Japanese Patent Application No. 2001-236429 (unknown). According to this direction correcting device, since the wedge device is arranged in the joint end surface between the new box and the existing box, it does not protrude to the side of both boxes as an obstacle, and is described in Patent Document 1 described above. The problem in the invention can be solved.
By the way, recently, the demand for reducing the construction cost of the submerged box submersion method has become strict, and as a part thereof, various cost reduction measures have been studied for rubber gaskets interposed between submerged boxes. However, in addition to the conventional general submerged box submersion method, in the submerged box submersion method using the above-mentioned wedge device, since the entire load of hydraulic bonding is applied to the rubber gasket, even if the rubber gasket receives this full load It is necessary to use a large-sized one which does not cause buckling or breakage (has a large reaction force resistance), and there is a certain limit to the cost reduction.
In view of such a current situation, the present inventors have focused on a wedge-type direction correcting device described in Japanese Patent Application No. 2001-236429 and changed the direction correcting procedure by the device to obtain a rubber gasket. It has been found that such a load can be reduced. The present invention has been made based on the above findings, and an object thereof is to provide a direction correcting method which achieves a cost reduction of a rubber gasket while utilizing the characteristics of a box wedge type direction correcting device. It is in.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a wedge device for vertically wedge-locking a fixed wedge and a movable wedge to an inner portion of a rubber gasket at a joint between left and right side walls of an existing box and a new box. A driving device for moving the wedge is provided, and firstly, the new box is hydraulically joined to the existing box while sharing the load of hydraulic joining between the rubber gasket and the left and right wedge devices. And push back the new box by the reaction force of the rubber gasket, and in this state, move the movable wedge of the left or right wedge device by a corresponding amount to correct the displacement of the rear end of the new box. Then, the new box is hydraulically joined to the existing box while the rubber gasket and the left and right wedge devices are subjected to the hydraulic joining load.
In the present invention, the initial wedge height of the wedge device is set within a range that allows the rubber gasket to share a load lower than its allowable load and that guarantees the waterproofness and the allowable return deformation of the rubber gasket.
In the method of correcting the direction of the submerged box performed in this way, the load applied to the rubber gasket is reduced by sharing a part of the load of the hydraulic joining to the left and right wedge devices, and the use of a small rubber gasket is reduced. Becomes possible. In addition, since the wedge device and its driving device are arranged in the same manner as the wedge-type direction correcting device in the box, the wedge device does not protrude as an obstacle to the side of the submerged box (new or existing box).
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
7 to 9 show a direction correcting device used for carrying out the method for correcting the direction of a submerged box according to the present invention. This direction correcting device 20 is the same as that described in the above-mentioned Japanese Patent Application No. 2001-236429, and is a wedge device for setting a joining interval between the existing box 10 and the new box 11 which are hydraulically joined via the rubber gasket 12. It is schematically constituted by 21 and a driving device 22 for operating the wedge device 21.
[0009]
The existing box 10 and the new box 11 have a rectangular cross section here, and the internal space is divided into a plurality by an inner wall 13 (FIG. 10) and left and right partitions 14 and 15. Before joining, the opening of the existing box 10 on the joining end side with the new box 11 is closed by the bulkhead 16, and both ends of the new box 11 (the rear end side is omitted) are closed by the bulkhead 17. A sealed chamber 18 surrounded by the rubber gasket 12 is formed between the bulkheads 16 and 17 in accordance with the connection between the bulkheads 10 and 11. The existing box 10 and the new box 11 may be of any structure, and may be a reinforced concrete (RC) structure, a steel shell structure, a steel-concrete composite structure, or the like.
[0010]
On the other hand, the rubber gasket 12 is configured as a gina type here, and as shown in FIG. 3, a mountain-shaped nose portion 12b is provided on an upper surface of a trapezoidal main body portion 12a, and a fiber is provided on a lower surface of the main body portion 12a. The structure has a reinforcing flange portion 12c. The rubber gasket 12 is tightly fixed to the end surface of the new gasket 11 with the flange portion 12c aligned with the end surface of the new box 11 using a bolt (not shown) having a through hole 19 provided in the flange portion 12c. I have. The size of the gina-type rubber gasket 12 is defined by the width L of the bottom surface and the height H from the bottom surface to the upper surface of the main body 12a.
[0011]
The wedge device 21 used in the present invention is disposed on a pedestal 23 fixed to a step portion inside the rubber gasket 12 on the end surfaces of the left and right side walls 10a of the existing box 10, as will be described again with reference to FIGS. It comprises a fixed wedge 24 and a movable wedge 26 disposed on a pedestal 25 fixed to a step portion inside the rubber gasket 12 on the end face of the new box 11. The fixed wedge 24 and the movable wedge 26 are arranged on the corresponding pedestals 23 and 25 so as to extend in the vertical direction, that is, to be wedge-engaged in the vertical direction. The wedge engaging surface 24a of the fixed wedge 24 and the wedge engaging surface 26a of the movable wedge 26 are inclined so as to increase the wedge engagement height in accordance with the downward movement of the movable wedge 26. As a result, the joining distance between the existing box 10 and the new box 11 is increased in accordance with the downward movement of the movable wedge 26.
[0012]
On the other hand, the drive device 22 is disposed to extend in the vertical direction on the side of the pedestal 25 on the new box 11 side, and has a hydraulic cylinder 27 fixed to the pedestal 25 and an output shaft 27a of the hydraulic cylinder 27. And a connecting bar 29 whose upper end is fixed to the bracket 28 and whose lower end is connected to the movable wedge 26 (FIG. 7). The hydraulic cylinder 27 is formed to have a small diameter and a long length so as to secure a sufficient stroke length although having a low output. The operation of the hydraulic cylinder 27 is performed by an oil supply / discharge device (not shown) arranged in the new box 11. It is controlled by liquid supply and drainage.
[0013]
Various methods, such as a tower pontoon method, a placing barge method, and a floating crane method, can be adopted as a method of submerging the new box 11, but when the tower pontoon method is adopted, as shown in FIG. On the box 11, one or two control towers 30 (one in the illustrated example) and two pontoons 31 are fitted. A surveying and commanding room 32 is provided above the control tower 30, and an access shaft (not shown) for allowing workers to enter and leave the new box 11 is provided therein. A wire 34 having a tip connected to a sinker 33 installed on the sea floor is routed around the new box 11, and the new box 11 is operated by a winch (not shown) mounted on the control tower 30. It is designed to be operated horizontally. A wire 35 for suspending and supporting the new box 11 is routed through each pontoon 31. The new box 11 includes a sedimentation winch (not shown) mounted on each pontoon 31 and a ballast in the new box 11. It settles when water is injected into a tank (not shown).
[0014]
The new box 11 also has a submerged box position surveying system (not shown) which takes in GPS signals from the GPS antenna 36 on the control tower 30 and performs overall position management, and position management relative to the existing box 10. (Not shown), a distance meter 37 for measuring the compression amount of the rubber gasket 12 with high accuracy, a measuring device (laser measuring device) 38 for measuring the horizontal and vertical inclinations of the new box 11, and the like. Surveying means. The new box 11 further includes a pouring / draining pump for draining seawater in the closed chamber 17 between the bulkheads and injecting seawater into the closed chamber 18, a bearing jack, a mortar pump, and the existing box 11. A vertical shear key (bracket) and the like for positioning are mounted, but these are not shown.
[0015]
When the new box 11 is submerged, the submerged box 11 in which the above-described various outfittings have been fitted is towed to the submerged position, and at that position, a necessary number of sinkers 33 are installed on the seabed and necessary wiring is performed. After completion of the preparation, the new box 11 is guided with respect to the existing box 10 while controlling the position by the above-mentioned submerged box position measuring system, end face exploration device, etc., and a vertical shear key (not shown) at the tip thereof is inserted into the existing box 10. (Not shown), and the rear end thereof is further seated on a temporary support table installed on the excavated bottom of the sea floor via a support jack (not shown). Next, the new box 11 is pulled toward the existing box 10 by the operation of the pulling jack 39 (FIG. 1) provided on the existing box 10, and thereafter, the joining step including the direction correcting method according to the present invention is performed. .
[0016]
FIGS. 1 and 2 show a joining step including a direction correcting method according to the present invention. First, as shown in FIG. The nose portion 12b of the rubber gasket 12 attached to the joint end surface of the box 11 is compressed, and a closed chamber 18 surrounded by the rubber gasket 12 is provided between the bulkhead 16 of the existing box 10 and the bulkhead 17 of the new box 11. It is formed. At this time, the movable wedge of the wedge device 21 constituting the direction correcting device 20 has an appropriate initial wedge height S included in the maximum compression amount δ1 (FIG. 3) of the rubber gasket 12 described later. In this stage, the fixed wedge 24 and the movable wedge 26 maintain the non-wedge state at this stage, as shown in FIG.
[0017]
Next, the injection pump in the new box 11 is operated to drain, and the seawater in the closed chamber 18 between the bulkheads is drained. Then, as shown in FIG. 1 (2), the new box 11 is pushed toward the existing box 10 by the water pressure P applied to the back surface of the new box 11, and is hydraulically joined. At this time, the left and right wedge devices 21 wedge at the above-described initial wedge height S as shown in FIG. 2B, whereby the rubber gasket 17 has its maximum wedge as shown by the one-dot chain line in FIG. Deformation is stopped with a compression amount smaller than the compression amount δ1. That is, the load due to the water pressure P is received by being shared by the wedge device 21 and the rubber gasket 12. The amount of compression of the rubber gasket 12 is monitored by the end face distance meter 37 (FIG. 10).
[0018]
Simultaneously with the completion of the hydraulic joining, the inside of the box is surveyed by the measuring device 38 through an access shaft (not shown) provided in the control tower 30. Then, as shown in FIG. 5, if the rear end of the new box 11 is displaced by, for example, C to one side from the tunnel normal line by the inside-box survey and the displacement C is larger than expected, The injection pump in the new box 11 is switched to the water injection operation, and seawater is injected into the sealed chamber 18 between the bulkheads as shown in FIG. Then, the rubber gasket 12 restores the main body 12a to almost the original height, and the restoring force (reaction force) pushes back the new box 11, and accordingly, as shown in FIG. The distance between the fixed wedge 24 and the movable wedge 26 in the tunnel normal direction also increases.
[0019]
Then, as shown in FIG. 2 (3), the movable wedge 26 of the wedge device 21 of the left and right wedge devices 21 arranged on the side where the rear end of the new box 11 is shifted is moved by the operation of the hydraulic cylinder 27. Move down from the position. The moving amount (shift amount) α of the movable wedge 26 at this time is an amount suitable for eliminating the displacement amount C of the new box 11, and the wedge height of the wedge device 21 is reduced by the downward movement of the movable wedge 26. As shown in FIG. 4, the height increases from h1 (initial wedge height) to h2. The movement (downward movement) of the movable wedge 26 is performed in a free state in which the movable wedge 26 does not come into contact with the fixed wedge 24. Therefore, as the hydraulic jack 27 constituting the drive means 22, a small-sized and low-output hydraulic jack can be used. .
[0020]
Next, the pump is switched to the drain side, and the seawater in the closed chamber 18 between the bulkheads is drained again by the drain operation. Due to this drainage, the new box 11 is hydraulically joined to the existing box 10 again as shown in FIG. 1 (4). At this time, as shown in FIG. The wedge 24 and the movable wedge 26 come into contact with each other, and the movement of the new box 11 toward the existing box 20 is restricted by the wedge device 21. Since the wedge device 21 on the side where the rear end of the new box 11 has shifted has increased the wedge height by the shift of the movable wedge 26, the shifted side of the new box 11 is shown in FIG. As shown in (4), the state is returned to the existing box 10 by a predetermined amount (return amount) δ, and the direction is corrected.
[0021]
Thereafter, the inside of the box is surveyed again, and it is checked whether the deviation from the normal line of the tunnel is within the plan. If the deviation is within the plan, water is poured into a ballast tank (not shown) to the new box 11. The ballast water load is increased, and then the bulkhead 16 of the existing box 10 and the bulkhead 17 of the new box 11 are removed, and in parallel with this, a crushed stone stopper is constructed around the new box 11. Thereafter, mortar is filled into the bottom of the box, the bearing jack is lowered, and backfilling is performed in accordance with the normal method of submerging the submerged box, thereby completing the submerging of one submerged box.
[0022]
Here, as shown in FIG. 5, the return amount δ of the new box 11 with respect to the existing box 10 is C, the displacement of the new box 11 is A, the total length of the new box 11 is A, and the distance between the left and right wedge devices 21 is C. If B is given, it is given by the following equation (1).
δ = B × C / A (1)
On the other hand, as shown in FIG. 4, the shift amount α of the movable wedge 26 for obtaining the return amount δ is determined by the inclination angle (wedge angle) of the wedge engagement surfaces 24a, 26a of the wedges 24, 26 constituting the wedge device 21. ) Is given by θ, and is given by the following equation (2). By substituting equation (1) into this, the following equation (3) is obtained.
α = δ / tan θ (2)
α = (B × C) / (A × tan θ) (3)
[0023]
By the way, in order to improve the adjustment accuracy of the return amount δ of the new box 11 with respect to the existing box 10, the return amount per unit shift amount of the movable wedge 26 is made as small as possible, that is, the effective movement amount (shift amount) of the movable wedge 26 is reduced. Must be as large as possible. In this case, since the total length A of the new box 11 and the interval B between the left and right wedge devices 21 are constant, the wedge device 21 is required to obtain the shift amount α of the movable wedge 26 as large as possible from the above equation (3). It can be seen that it is desirable to set the wedge angle θ as small as possible. In this regard, as described above, the wedge device 21 of the present invention is provided so as to vertically wedge the joint between the left and right side walls 10a, 11a of the existing box 10 and the new box 11, so that the wedge angle θ Is small, the shift amount α of the movable wedge 26 can be made sufficiently large, and the adjustment accuracy of the return amount of the new box 11 can be greatly increased. As a result, the direction correction accuracy of the new box 11 is remarkably large. improves.
[0024]
The condition for maintaining the wedge state stably even when the wedge device 21 receives the water pressure P when the new box 11 is hydraulically joined to the existing box 10, that is, the movable wedge 26 is fixed to the fixed wedge 24. The condition for not sliding on the top is based on the relationship between the component force P × sin θ in the direction along the wedge engagement surfaces 24a and 26a and the component force P × cos θ in the normal direction of the wedge engagement surfaces 24a and 26a, as shown in FIG. Or from the relationship with the friction coefficient μ of the wedges 24 and 26, it is necessary to satisfy the following expression (4) or (5).
P × sin θ <P × cos θ × μ (4)
tanθ <μ ... (5)
[0025]
In this case, the friction coefficient μ is naturally determined because the fixed and movable wedges 24 and 26 are made of steel. Therefore, in order to prevent the movable wedge 26 from sliding, the above (4) or (5) From the equation, it is necessary to set the wedge angle θ as small as possible. In this regard, as described above, the wedge device 21 of the present invention can set the wedge angle θ to be sufficiently small. The movable wedge 26 does not slide due to the joining force P, and the joined state is stably maintained. This means that even if the hydraulic cylinder 27 is removed simultaneously with the removal of the bulkhead described above, the new box 11 maintains its position (hydraulic joining position), and awaiting the later stabilization work of the new box 11. It is possible to remove the hydraulic cylinder 27 without the need, and the construction period is shortened accordingly.
[0026]
On the other hand, the allowable return deformation amount δS of the rubber gasket 12 required for correcting the direction of the new box 11 is determined by the maximum compression amount δ1 at the time of hydraulic joining when the wedge device 21 is omitted and the height of the nose portion 12b of the rubber gasket 12. From the correlation between the deformation amount δ2 that satisfies the water stoppage, the manufacturing error δ3 of the end face between the submerged boxes 10 and 11, the manufacturing accuracy and the temperature shrinkage amount δ4 of the rubber gasket 12, and the unexpected deformation allowance δ5 determined by It is determined based on the following equation (6).
δS = δ1- {δ2 + δx (= δ3 + δ4 + δ5)} (6)
Therefore, it is necessary to set the original position of the wedge device 21 within a range that does not hinder the water stoppage (δ2 to δ5) of the rubber gasket 12 and sufficiently guarantees the allowable return deformation amount δS. In FIG. 3, the above-described elements required for the rubber gasket 12 are added. From this, it is desirable that the original position S of the wedge device 21 be set within the range of δx (= δ3 + δ4 + δ5). It can be said that.
[0027]
The rubber gasket 12 shows specific compression characteristics depending on its size (L, H) and hardness. As an example, the compression characteristics of a rubber gasket having L = 155 mm, H = 109 mm, and hardness 40 are shown in FIG. It is as follows. In this case, the allowable load Pf is at a level (about 65 × 9.8 kN / m) lower than the total load Po (about 87 × 9.8 kN / m) of the hydraulic joining, and the wedge device 21 is used for the hydraulic joining. If the load is not shared, the rubber gasket may buckle or break. Further, even when the load is shared by the wedge device 21, if the shared load Pk of the wedge device 21 is set to a level higher than the allowable load Pf, the rubber gasket similarly buckles or breaks. there is a possibility. Therefore, when setting the initial wedge height S of the wedge device 21, it is necessary to set the shared load Pk of the wedge device 21 to a level lower than the allowable load Pf. In the example shown in FIG. 6, the shared load Pk of the wedge device 21 is set to about 45 × 9.8 kN / m. In this case, the buckling and breakage of the rubber gasket can be prevented. In addition, the waterproofness of the rubber gasket (δ2 to δ5) and the allowable return deformation δS are sufficiently guaranteed.
[0028]
Here, in the conventional construction method in which the entire load Po (approximately 87 × 9.8 kN / m) of the hydraulic joining is applied to the rubber gasket, a rubber gasket having an allowable load Pf at a level higher than the total load Po must be selected. Must be used, and a large one is needed. Incidentally, the size of the rubber gasket having the allowable load Pf of the level of 95 × 9.8 kN / m is L = 190 mm, H = 148 mm when the hardness is 40, and the rubber gasket 12 usable in the method of the present invention described above. (L = 155 mm, H = 109 mm).
[0029]
【The invention's effect】
As described above, according to the method for correcting the direction of the buried box according to the present invention, a part of the load of the hydraulic joining is shared between the left and right wedge devices, so that the load applied to the rubber gasket is reduced. The reduced amount enables the use of a small rubber gasket, which is advantageous in cost. In addition, the wedge device and its driving device do not not only protrude as an obstacle to the side of the buried box, but also enable the removal of the driving means at an early stage. This has the effect of greatly contributing to
[Brief description of the drawings]
FIG. 1 is a schematic view showing a joining step including a method for correcting the direction of a buried box according to the present invention.
FIG. 2 is a schematic diagram showing an operation state of a wedge device in a joining step shown in FIG.
FIG. 3 is a cross-sectional view showing a cross-sectional shape and a deformed state of a rubber gasket used for a joint portion of a submerged box.
FIG. 4 is a schematic diagram showing the principle of direction correction by a wedge device.
FIG. 5 is a schematic diagram showing a state in which a new box is shifted in the horizontal direction.
FIG. 6 is a graph showing compression characteristics of a rubber gasket usable in the present invention.
FIG. 7 is a front view showing an installation structure of a direction correcting device used in the present invention.
FIG. 8 is a longitudinal sectional view showing an installation structure of the direction correcting device.
FIG. 9 is a cross-sectional view showing an installation structure of the direction correcting device.
FIG. 10 is a perspective view schematically showing a tower pontoon type construction method in which a new box is sunk.
[Explanation of symbols]
10 Existing Box 11 New Box 12 Rubber Gasket 16 Existing Box Bulkhead 17 New Box Bulkhead 18 Sealed Room 20 Between Bulkheads 20 Direction Correction Device 21 Wedge Device 22 Drive Device 24 Fixed Wedge 26 Movable Wedge 27 Hydraulic Cylinder 39 jack

Claims (2)

A wedge device for vertically wedge-engaging a fixed wedge and a movable wedge, and a drive device for moving the movable wedge are provided at a joint portion between the left and right side walls of the existing box and the new box, inside the rubber gasket. First, a new box is hydraulically joined to the existing box while sharing the load of hydraulic joining between the rubber gasket and the left and right wedge devices, and then water is injected between the bulkheads and the new gasket is installed by the reaction force of the rubber gasket. Push back the box, and in this state, move the movable wedge of the left or right wedge device by a corresponding drive by an amount necessary to correct the displacement of the rear end of the new box, and thereafter, the rubber gasket A method of correcting the direction of an immersed box, wherein the new box is hydraulically joined to the existing box again while sharing the load of the hydraulic joining to the right and left wedge devices. 2. The wedge device according to claim 1, wherein an initial wedge height of the wedge device is set within a range that allows the rubber gasket to share a load lower than its allowable load and that guarantees the water stoppage and allowable return deformation of the rubber gasket. The method of correcting the direction of the buried box described in.

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