JP2002138791A - Jacking method to portal, and entrance packing supporting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a jacking method to a portal and its packing supporting structure in which a covering can reliably be drawn out of an arrival entrance, and a holding plate can be prevented from biting a surface of the covering and an excavator. SOLUTION: The annular entrance packing 20 and the holding 24 for preventing curling are successively disposed from a distal end side of the arrival portal 14 to an opening side. The covering 26 is inserted inside the entrance packing 20 so that the tip of the entrance packing 20 is directed toward the distal end side of the entrance. A space is formed between the outer circumference of the covering 26 and the holding plate 24, and a bolt 25 is passed through a through hole 34 in an outer flange 30 provided on the covering 26. Since the entrance packing 20 is supported by the covering 26, the covering 26 can be released only by drawing the bolt 25 from the through hole 34, and the bolt can be reliably drawn out of the arrival shaft 14 even when the covering 26 is inclined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for propulsion to a wellhead and a support structure for an entrance packing, and more particularly to a method for sealing a gap between the reaching wellhead and the excavating device when the digging device reaches the reaching wellhead. Also, the present invention relates to a method for propelling a wellhead and a structure for supporting an entrance packing, which can prevent muddy water from flowing out.

[0002]

2. Description of the Related Art In recent years, cables such as communication cables and optical cables are sometimes extended through tunnels formed underground. When a new tunnel is to be constructed, an excavator for underground propulsion is generally used.

When a tunnel is constructed by an excavator, firstly, a shaft is dug to an arbitrary depth on both sides where the tunnel is to be formed, and one shaft is set as a starting side and the other shaft is set as a reaching side. Then, the excavator is sent out from the shaft on the starting side toward the arrival side, and a fume tube is added and inserted from the starting side to form a tunnel with the sent out fume tube.

[0004] By the way, a large earth pressure or water pressure acts on the outside of the wall surface of the shaft. For this reason, at the start entrance and arrival entrance provided in the shaft, an entrance packing is provided near the opening, and this entrance packing is brought into contact with a drilling device or a fume pipe,
Muddy water is prevented from flowing into the shaft.

FIG. 9 is an explanatory view showing a support structure of an entrance packing at a reaching wellhead. That is, as shown in FIG. 1A, when the excavator 3 reaches the entrance packing 2 at the arrival wellhead 1, the entrance packing 2 is deformed to the shaft 4 side. For this reason, when the earth pressure or the water pressure exceeds the deformation force of the entrance packing 2, there is a possibility that muddy water or the like flows into the shaft 4.

For this reason, at the arrival well, FIG.
As shown in (1), a cover ring 5 capable of containing the excavator is inserted in advance into the opening, and the tip of the entrance packing 2 is set in the direction opposite to the propulsion direction of the excavator 3 (the back side). . Entrance packing 2
The holding plate 6 for preventing the turning over is pressed against the cover ring 5 to hold the cover ring 5.

The excavator 3 propelled from the back of the mine
When the cover ring 5 is pressed at the position, the entrance packing 2 is deformed in the direction opposite to the propulsion direction, and the excavator 3
Alternatively, since the vehicle moves to a fume pipe (not shown), a seal corresponding to a change in earth pressure or water pressure can be secured.

The cover ring is supported only by the entrance packing without providing the holding plate, or as shown in FIG. 3 (3), the cover ring 5 is provided with a retractable holding plate 6 (restriction piece). Is also known.

[0009]

However, the above-described structure for supporting the entrance packing at the arrival well has the following problems. That is, in the support structure as shown in FIG. 2B, the pressing plate presses the cover ring. For this reason, it is necessary that the cover ring slides with respect to the holding plate by the amount of insertion of the cover ring. During this time, if the sliding direction is inclined, the holding plate bites into the surface of the cover ring. There was a risk that the cover ring could not be removed from the arrival well.

If the cover ring is supported only by the entrance packing as shown in FIG. 3 (3), the problem that the cover ring does not come off from the arrival well can be avoided. The entrance packing was turned up, and there was a risk that muddy water would flow into the shaft from this turned up point.

If a folding type holding plate is attached to the entrance packing in FIG. 3 (3), it is possible to prevent the entrance packing from being turned over, but when the cover ring or the excavator is moved, the holding plate is used for the cover. There is a risk that the cover ring and the excavator will not be able to get out of the reaching wellhead, because it will bite into the surface of the ring or the excavator.

The present invention focuses on the above-mentioned conventional problems, and ensures that the covering can be pulled out from the arrival well,
An object of the present invention is to provide a method of propulsion to a wellhead and a support structure of an entrance packing, which can prevent a holding plate from biting into a surface of a covering or a drilling device.

[0013]

SUMMARY OF THE INVENTION According to the present invention, biting by the holding plate can be prevented by preventing the holding plate for preventing the entrance packing from being turned up from coming into contact with the surface of the covering or the excavator. It was made based on the finding.

In other words, in the method for propelling a wellhead according to the present invention, a cover ring is inserted from the opening side into an entrance packing located at the wellhead, and the front end of the entrance packing is directed toward the inner side of the well, and the entrance packing is used. After holding the cover ring in a floating state, an excavator is introduced into the cover ring, and the entrance packing is received by a holding plate separated from the cover ring to maintain the floating state of the cover ring. The entrance packing is transferred from the covering to the excavator, and the excavator is held only by the entrance packing.

[0015] Further, in the entrance packing supporting structure according to the present invention, an annular entrance packing is arranged in order from the inner side of the reaching wellhead to the opening side, and a pressing plate for preventing the entrance packing from being turned up. A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing so that a tip of the entrance packing faces a pit side, and a gap for floating is formed between an outer periphery of the cover ring and the holding plate. At the same time, the cover ring is provided with a flange portion, and the flange portion is provided with a hook portion for fixing to the opening end surface of the reaching wellhead. The cover ring may be composed of a plurality of blocks, which may be arranged in a circular shape along the reaching wellhead.

[0016] An annular entrance packing and a pressing plate for preventing the entrance packing from being turned up are arranged in order from the inner side of the arrival well to the opening side.
A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing so that a tip of the entrance packing faces a pit side, wherein a floating gap is provided between the outer periphery of the cover ring and the holding plate. And the cover ring was supported only by the entrance packing. It is preferable that a brush is disposed inside the cover ring, and the end face on the opening side of the cover ring may be sealed.

[0017]

According to the above construction, by arranging the entrance packing at the wellhead and inserting and inserting the cover ring from the inside of the shaft into the center of the entrance packing, the tip of the entrance packing can be moved along the surface of the cover ring to the inside of the downhole. Following to the side, the covering can be held in this state. A holding plate for preventing the entrance packing from being turned up is provided on the opening side of the entrance packing at the wellhead, and the length of the holding plate is set so that a gap is formed between the tip of the holding plate and the cover ring. Is set.

In order to fix the cover ring, a flange portion is provided on the cover ring, and the cover ring may be fixed to the opening end face of the wellhead by a hook formed on the flange portion. A through-hole may be formed in the portion, and a bolt protruding from the opening end face of the wellhead may be inserted into this through-hole. If the cover ring is fixed by the hook portion formed in the flange portion as described above, when the cover ring is pulled out from the wellbore, the release of the cover ring from the opening end face becomes the hook portion (the flange portion). Just pull it out of the (thick) through hole,
Therefore, it is possible to prevent the cover ring from falling out of the arrival well due to the inclination of the cover ring.

If the cover ring is composed of a plurality of blocks, the blocks can be attached along the wellbore, and can be easily attached manually. By the way, the entrance packing is arranged at the wellhead, and the holding plate is arranged closer to the opening than the entrance packing. If a gap is formed between the outer periphery of the cover ring and the holding plate, and the cover ring is supported only by the entrance packing, the cover ring will be in a floating state supported by the elastic body. Can be absorbed by the elastic deformation of the entrance packing.

Further, the covering is pushed into the inside of the shaft by the excavator. If the propulsion direction of the excavator is inclined or the propulsion resistance is not uniform, the covering may be inclined. However, since the cover ring is supported only by the entrance packing, it is possible to prevent the surface of the cover ring from being bitten by a rigid body, and it is possible to reliably remove the cover ring from the wellhead. Even if the entrance packing is transferred from the covering to the excavator, the excavator is supported only by the entrance packing, so that it is possible to prevent the surface of the excavator from biting.

Further, the sliding resistance of the entrance packing is received by the pressing plate adjacent to the cover ring,
Since the turning-up prevention is performed, it is possible to maintain the attitude of the entrance packing with the tip directed toward the inner side of the pit.

If a brush is arranged inside the cover ring and the brush is pressed against the excavator, muddy water flows out of the gap between the inner periphery of the cover ring and the outer periphery of the excavator to the shaft. Can be prevented. If the shape of the cover ring is made of a tea caddy instead of the brush and one end face is sealed, it is possible to reliably prevent the muddy water from flowing out to the shaft.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention, which is suitable for a method of propulsion to a wellhead and a support structure for an entrance packing, according to the present invention will be described in detail with reference to the drawings. FIG.
FIG. 2 is an explanatory view showing a support structure of the entrance packing according to the first embodiment, and FIG. 2 is a perspective view showing a cover ring used in the embodiment.

When a new tunnel for inserting cables such as a communication cable and an optical cable is newly provided, firstly, shafts are formed at both ends of the planned tunnel site. Then, one side of the shaft is set as the starting shaft, and the other is set as the reaching shaft 10, the excavator 12 is propelled from the starting shaft, and a fume pipe is added and inserted from the starting shaft to form a tunnel.

On the other hand, the arrival shaft 10 is provided with an arrival well 14 for receiving the excavator 12 on a side surface thereof, as shown in FIG. A mounting ring 16 with a flange is mounted on the periphery of the opening of the arrival well 14, and an annular entrance packing 20, a spacer 22, and a holding plate 24 are sequentially laminated on the flange 18 of the mounting ring 16. ing. Bolts 25 are inserted through these, and the above-mentioned packings are mounted on the flange 18. An elongated hole is formed in the holding plate 24 so as to coincide with the longitudinal direction, and the holding plate 24 can be inserted and removed along the radial direction of the reaching well 14.

A cover ring 26 is inserted into the arrival well 14 from the inside of the shaft. The cover ring 26 has a cylindrical main body 28 as shown in FIG. 2A, and the inner diameter thereof is set to a size enough to take the excavator 12 into the inside thereof. Note that the clearance between the cutter bit formed at the tip of the excavator 12 and the inner wall of the main body 28 may be set in accordance with the accuracy of the arrival position of the excavator 12. The clearance set in consideration of the accuracy of the arrival position secures a margin for taking the excavator 12 into the main body 28.

On the other hand, the outer diameter of the main body 28 is set to be equal to or larger than the inner diameter of the entrance packing 20 and smaller than the diameter of a circle connecting the tips of the holding plates 24. By setting the inner and outer diameters of the main body 28 in this manner, it is possible to deform the entrance packing 20 to the inner side of the pit while preventing the contact with the holding plate 24, and to take the excavator 12 inside the main body 28. Become.

By the way, from one end face of the main body 28, the outer flange 3 is formed in the radial direction of the main body 28.
0 and an inner flange 32 are respectively formed. The outer flange 30 has the same diameter as the above-described flange 18 of the mounting ring 16, and further has a plurality of through holes 34 so that the bolt 25 can be inserted.
If the through hole 34 is formed so as to correspond to the installation radius of the bolt 25, the bolt 25 is inserted into the through hole 34, and a nut (not shown) is screwed into the bolt 25. The cover ring 26 can be fixed to the flange 18.

On the other hand, the inner flange 32 extending in the opposite direction to the outer flange 30 is configured such that the tip of the excavator 12 comes into contact with the inner flange 32 when the excavator 12 enters the inside of the main body 28. The size may be set as much as possible. By setting the inner flange 32 to such dimensions,
By pressing the excavator 12 against the inner flange 32,
The cover ring 26 can be removed from the arrival well 14.

As described above, the covering 2 is
The procedure for inserting the excavator 6 into the supporting structure in which the entrance packing 20 is supported by the cover ring 26 will be described.

FIG. 4 is an explanatory cross-sectional view showing a state in which the excavator reaches the destination wellhead. As shown in FIG.
When taking the excavator 12 sent out from the starting well into the inside of the cover ring 26, first remove a nut (not shown) screwed to the bolt 25, and move the cover ring 26 in the extension direction of the bolt 25. So that you can pull it along. In such a state, the tip of the entrance packing 20 is in close contact with the main body 28 so as to be directed to the inner side of the pit, and the pressing plate 24 provided on the opening side of the entrance packing 20 is attached to the main body 28 of the cover ring 26. On the other hand, the feeding amount is set so that a gap that does not cause catching is formed.

A bent portion 24A is formed at the front end of the holding plate 24 so as to extend toward the inner side of the pit. The bent portion 24A is used to receive the deformation of the entrance packing 20 applied with water pressure or the like from the inner side of the pit. Things. That is, if the bent portion 24A is formed at the tip of the holding plate 24, the entrance packing 20 to which pressure is applied along the arc of the bent portion 24A follows, so that concentrated stress may be applied to the entrance packing 20. Absent. In this manner, the entrance packing 20 is formed with an arc along the bent portion 24A and is not subjected to concentrated stress, so that the holding plate 24 and the cover ring 26 (or the excavator 12) are not formed.
And the fume tube 36) can have a large clearance and can be easily pushed out. (If there is no bent portion 24A at the end of the holding plate 24 and the shape is straight, the entrance packing 20 will be covered by the cover ring. 26
And into the gap between the holding plate 24 and
That part receives concentrated stress. Therefore, the clearance between the holding plate 24 and the cover ring 26 must be reduced to prevent the entrance packing 20 from entering the gap between the cover ring 26 and the holding plate 24. ).

After such setting is completed, the excavator 12 is taken into the body 28 of the cover ring 26, and the tip of the excavator 12 is connected to the inner flange 32.
Contact. Connect the tip of the drilling rig 12 to the inner flange 32
When the excavator 12 is moved forward as it is, the covering 26 is pushed out of the reaching shaft 14 into the reaching shaft 10 as shown in FIG. With the movement of the cover ring 26, the entrance packing 20 moves toward the opening side of the arrival well 14. After the entrance packing 20 moves by the thickness of the spacer 22, the entrance packing 20 is supported by the holding plate 24. Keep state. Therefore, it is possible to prevent the packing itself from being turned up by the movement of the cover ring 26.

When the cover ring 26 moves, a bolt 25 attached to the flange 18 is inserted into the outer flange 30 of the cover ring 26, and slides between the bolt 25 and the inner wall of the through hole 34. Movement occurs,
This sliding occurs in addition to the thickness of the outer flange 30 and the bolt 25
It is only the tightening allowance of the nut. For this reason, the bolt 25 comes out of the through hole 34 by only slightly moving the cover ring 26, and thereafter the cover ring 26 has a floating structure supported only by the entrance packing 20. Therefore, even if the propulsion direction of the excavator 12 is tilted, or even if the cover ring 26 is tilted due to a difference in frictional resistance around the cover ring 26, a rigid body may bite into the surface of the cover ring 26. Therefore, by extruding the cover ring 26 with the excavator 12, the cover ring 26 can be reliably removed from the reaching shaft 10 side.

As shown in FIG. 3C, when the cover ring 26 is to be taken out to the reaching shaft 10, the holding plate 24 is extended to the excavator 12 and the cover ring 26 is taken out.
As in the case of the above, the space between the tip of the holding plate 24 and the outer surface of the excavator 12 may be narrowed. If the gap between the pressing plate 24 and the cover ring 26 is set in the same manner as described above (the feeding amount is set so as to form a gap that does not cause snagging), the entrance packing 20 is supported by the pressing plate 24, Since the posture is maintained, even if earth pressure or water pressure is applied to the entrance packing 20, it is possible to prevent the muddy water from flowing out to the shaft due to the increase in the pressure.

Then, the excavator 12 is moved while the tip of the entrance packing 20 is brought into close contact with the excavator 12, and the tip of the entrance packing 20 is moved to the excavator 12.
When the fume pipe 38 following the fume pipe 38 is reached, the fume pipe 38 has a smaller diameter than the excavator 12, so that the pressing plate 24 is again adjusted to match the outer diameter of the fume pipe 38.
May be extended toward the central portion of the entrance packing 20 (the amount of extension is set so as to form a gap that does not cause snagging). If the amount of extension of the holding plate 24 corresponds to the outer diameter of the fume tube 38 in this manner, even if the entrance packing 20 moves onto the fume tube 38, the entrance packing 2
Water can be reliably stopped without turning over to zero.

Incidentally, it is necessary to individually set the feeding amount of the pressing plate 24 according to the outer diameter of a member which advances in the central portion of the entrance packing 20. For this reason, hooks 35 are provided on the respective holding plates 24 except for the holding plate 24 arranged at the upper part as shown in FIG. 1, and the wires 36 are inserted through the hooks 35.
By pulling the wire 36, the throttle position of the holding plate 24 is adjusted according to the outer circumference of the main body 28, the outer circumference of the excavator 12, and the outer circumference of the fume tube 38 connected to the excavator 12 in the covering 26. By doing so, the setting can be easily performed. Note that the holding plate 24 disposed at the upper portion can be brought close to the center of the entrance packing 20 by its own weight, so that the insertion of the wire 36 becomes unnecessary.

FIG. 3 is a perspective view showing an application example of the cover ring used in the first embodiment. As shown in the figure, if the ring-shaped cover ring 26 is composed of individual blocks 27, the blocks 27 can be individually attached to the reaching wellhead 14, so that the attachment can be easily performed and a large lift can be achieved. This eliminates the need for preparing heavy equipment.

FIG. 5 is an explanatory view showing a support structure of the entrance packing according to the second embodiment.
FIG. 3 is a perspective view showing a cover ring used in the embodiment. As shown in these figures, the second embodiment is different from the first embodiment only in the shape of the cover ring 26. Therefore, in this embodiment, only the cover ring 26 will be described, description of other members will be omitted, and the same members as those in the first embodiment will be assigned the same reference numerals.

The cover ring 40 used in the second embodiment has a cylindrical main body 42, the inner diameter of which is set to a size enough to take the excavator 12 into the inside. The clearance between the cutter bit formed at the tip of the excavator 12 and the inner wall of the main body 42 is as follows.
What is necessary is just to set according to the arrival position precision of the excavator 12.
And in this embodiment (second embodiment),
Since the floating structure in which the cover ring 40 is supported by the rubber packing is used, the position of the cover ring 40 can be set flexibly. Therefore, in the second embodiment as compared with the first embodiment, the clearance can be narrowed. Specifically, the clearance between the cutter bit formed at the tip of the digging device 12 and the inner wall of the main body 28 depends on the position accuracy of the digging device 12 and the covering 40 in the floating state.
May be set according to the adjustment allowance. The clearance set in consideration of the accuracy of the arrival position and the allowance for adjustment allows a margin for taking the excavator 12 into the main body 28 to be secured.

On the other hand, the outer diameter of the main body 42 is set to be equal to or larger than the inner diameter of the entrance packing 20 and smaller than the diameter of a circle connecting the tips of the holding plates 24. By setting the inner and outer diameters of the main body 42 in this manner, it becomes possible to deform the entrance packing 20 to the inner side of the pit and to take the excavator 12 inside the main body 28.

By the way, from one end face of the main body 42, the inner flange 4 extends in the radial direction of the main body 42.
4 are formed. The inner flange 32 is attached to the main body 4.
When the excavator 12 enters the interior of the digging device 2, it is sufficient that the tip of the excavator 12 is set to a size that can contact the inner flange 44. The inner flange 4 has such dimensions.
If 4 is set, the covering 40 can be removed from the arrival well 14 by pressing the excavator 12 against the inner flange 44. On the side opposite to the end face where the inner flange 44 is formed inside the main body 42, the main body 42 is provided.
A wire brush 46 extending to the inner side of the pipe is provided in a circular shape.
2 and the fume pipe 38 following the fume pipe 38 can prevent earth and sand from entering the shaft from between the covering 40 and the excavator 12.

FIG. 8 is an explanatory sectional view showing a state in which the excavator reaches the arrival well. As shown in FIG.
Since the cover ring 40 is supported by the entrance packing 20 having elasticity, even if the excavator 1
Even if 2 is displaced from the arrival well 14, this displacement is absorbed by the elasticity of the entrance packing 20, and the excavator 12 can be taken into the covering 40.

The drilling rig 14 is placed in the covering 40.
When the cover ring 40 is pushed out by the excavator 14, the cover ring 40 is pushed out of the arrival shaft 14 to the inside of the arrival shaft 10 as shown in FIG. As the cover ring 40 moves, the entrance packing 20 moves toward the opening side of the arrival well 14.
Is moved by the thickness of the spacer 22, and then the pressing plate 2
4 and maintain the same state. Therefore, it is possible to prevent the packing itself from being turned up by the movement of the cover ring 26.

The pressing plate 24 supporting the entrance packing 20 has a clearance with respect to the cover ring 40, and therefore does not contact the cover ring 40. For this reason, it is possible to prevent the pressing plate 24 from biting into the surface of the cover ring 40, and it is possible to reliably remove the cover ring 40.

Then, as shown in FIG. 3C, the entrance packing 20 is moved from the covering 40 to the excavator 14.
When transferring to the excavator 14, the holding plate 24 is extended and the same clearance as that of the covering 40 is provided.
And may be formed between them. By setting the clearance between the holding plate 24 and the excavator 14 in this manner, even when the entrance packing 20 contacts the excavator 14, the holding plate 24 does not bite into the excavator 14,
The propulsion of the excavator 14 can be reliably performed. It is needless to say that the same effect can be obtained with respect to the fume pipe 38 disposed at the subsequent stage of the excavator 14 by setting an appropriate clearance between the fume pipe 38 and the holding plate 24.

FIG. 7 is a perspective view showing an application example of the covering used in the second embodiment. As shown in the figure, the wire brush 46 formed inside the cover ring 40 is eliminated, and the central portion of the inner flange 44 is sealed, so that the cover ring 40 is in the form of a tea caddy. Earth and sand from the space between the excavator 12 and the excavator 12 can be reliably prevented.

[0048]

As described above, according to the present invention, an annular entrance packing and a pressing plate for preventing the entrance packing from being turned up are arranged in order from the inner side of the arrival port to the opening side. A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing so that a tip of the entrance packing faces a pit side, wherein a floating gap is provided between the outer periphery of the cover ring and the holding plate. While forming, a flange portion is provided on the cover ring, and a hook portion fixing the opening end surface of the reaching wellhead is provided on the flange portion,

Alternatively, an annular entrance packing and a pressing plate for preventing the entrance packing from being turned up are arranged in order from the inner side of the arrival well to the opening side, and the front end of the entrance packing faces the inner side. A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing as described above,
Since a gap for floating is formed between the outer periphery of the cover ring and the holding plate, and the cover ring is supported only by the entrance packing, the cover ring can be reliably pulled out from the arrival well, and the holding plate is covered. It is possible to prevent biting into the surface of the ring or the drilling rig.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a support structure of an entrance packing according to a first embodiment.

FIG. 2 is a perspective view showing a cover ring used in the embodiment.

FIG. 3 is a perspective view showing an application example of the covering used in the first embodiment.

FIG. 4 is an explanatory cross-sectional view showing a state where the excavator reaches a destination wellhead.

FIG. 5 is an explanatory diagram showing a support structure of an entrance packing according to a second embodiment.

FIG. 6 is a perspective view showing a cover ring used in the embodiment.

FIG. 7 is a perspective view showing an application example of the covering used in the second embodiment.

FIG. 8 is an explanatory sectional view showing a state in which the excavator reaches a destination wellhead.

FIG. 9 is an explanatory diagram showing a support structure of an entrance packing at a reaching wellhead.

[Explanation of symbols]

1 ...... Arrival wellhead 2 ...... Entrance packing 3
Drilling rig, 4 shaft, 5 shaft, covering, 6 holding plate, 10 shaft, 12 shaft
... Excavation equipment, 14 ... Arrival wellhead, 16 ... Ring for mounting, 18 ... Flange, 20 ... Entrance packing, 22 ... Spacer, 24 ... Pressing plate, 2
5 Bolt, 26 Covering, 27
Block body, 28 body, 30 outer flange, 32 inner flange, 34 through-hole, 35
... hook, 36 ... wire, 38 ... fume tube, 40 ... covering, 42 ... body, 44 ...
…… Inner flange, 46 …… Wire brush

Claims (6)

[Claims] 1. A cover ring is inserted into an entrance packing located at a wellhead from an opening side, and a tip of the entrance packing is directed toward a deep side. After the cover ring is held in a floating state by the entrance packing, Introducing the excavator into the cover ring, receiving the entrance packing with a holding plate separated from the cover ring, and keeping the floating state of the cover ring, and moving the entrance packing from the cover ring to the excavator. Characterized in that the excavation device is held only by the entrance packing. 2. An annular entrance packing and a pressing plate for preventing the entrance packing from being turned up are arranged in order from the inner side of the arrival port to the opening side, and the tip of the entrance packing faces the inner side. A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing as described above, wherein a gap for floating is formed between the outer periphery of the cover ring and the holding plate, and a flange portion is formed on the cover ring. A support structure for an entrance packing, wherein a hooking portion is provided on the flange portion for fixing to the opening end surface of the reaching wellhead. 3. The entrance packing support structure according to claim 2, wherein the cover ring is composed of a plurality of blocks, which are arranged in a circular shape along the reaching wellhead. 4. An annular entrance packing and a pressing plate for preventing the entrance packing from being turned up are arranged in order from the inner side of the arrival well to the opening side, and the tip of the entrance packing faces the inner side. A support structure for an entrance packing in which a cover ring is inserted inside the entrance packing as described above, wherein a gap for floating is formed between the outer periphery of the cover ring and the holding plate, and the cover ring is provided only by the entrance packing. Entrance packing support structure characterized by being supported by 5. The support structure for an entrance packing according to claim 4, wherein a brush is arranged inside the cover ring. 6. The support structure for an entrance packing according to claim 4, wherein an opening-side end face of the cover ring is sealed.