JP3200696B2 - How to protect the starting wellhead - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a start tunnel when a shield excavator is inserted and propelled between two entrance packings provided in the start tunnel, and more particularly, to a two annular entrance packing and a shield. Characterized by filling filling water at a pressure almost equal to the muddy water pressure of the face with the propulsion of the shield machine, into the hollow part surrounded by the outer peripheral surface of the shield body of the excavator and the inner wall surface of the starting wellhead It is.

[0002]

2. Description of the Related Art As a protection device for a starting wellhead for starting a shield machine, there is a device using two entrance packings as shown in FIG. FIG. 10 is a sectional view showing a schematic structure of a protection device provided at a starting wellhead, and FIG.
FIG. 12 is a partially enlarged cross-sectional view showing a state in which the middle bent portion of the shield machine shown in FIG. 10 passes through the entrance packing on the face side. FIG. 12 is a rear view protruding from the outer peripheral surface of the rear shield body of the shield machine. FIG. 1 is a partially enlarged explanatory view showing a state in which a filling injection tube and the like pass through an entrance packing on the face.
3 is a partially enlarged sectional view showing a state where the tail end of the shield machine passes through the entrance packing on the face side.

A starting shaft 2 having a circular shape is formed on a side wall 1 of a shaft shown in FIG. Around the starting wellhead 2, a concrete reinforcing layer 5 having an annular shape having the same diameter is formed.
A protective device is provided inside this. This protective device has an annular entrance packing 3 made of rubber.
4 is provided. These entrance packings 3 and 4
While maintaining a predetermined interval in the propulsion direction A of the shield machine 6,
Its outer edge is fixed to the inner wall surface 5a of the concrete reinforcing layer 5.

In the illustrated shield machine 6, a bent portion 7 is formed between a front shield body 8 and a rear shield body 9, and a cutter head 8 is provided in front of the front shield body 8.
a is rotatably mounted. Further, a lining segment 12 having a diameter smaller than the diameter of the rear shield body 9 is formed continuously behind the rear shield body 9. As shown in FIG. 11, the middle bent portion 7 has a step portion 9 a having a diameter smaller than the diameter of the outer peripheral surface formed at the connection end of the rear shield body 9 with the front shield body 8 over the entire circumference. Between the outer peripheral surface of the step portion 9a and the back surface of the front shield main body 8, a middle bend seal 10 is provided over the entire circumference. Thereby, muddy water is prevented from entering from the center bent portion 7.

Incidentally, the entrance packings 3, 4
The openings 3a and 4a are in close contact with the outer peripheral surfaces of the front and rear shield bodies 8 and 9 of the shield machine 6 inserted therein and the outer peripheral surface of the lining segment 12 following the rear shield body 9. The inner diameter is formed to prevent the muddy water W of the face K from leaching into the shaft. In addition, if two entrance packings 3 and 4 are provided as shown in the figure, even if the entrance packing 3 on the face K is broken for some reason, the entrance packing 4 on the shaft will prevent the muddy water from entering. There is an advantage that the leaching of W can be prevented.

Further, as shown in FIGS. 10 and 12, the outer peripheral surface of the rear shield body 9 is filled with a filler between the lining segment 12 and the ground at predetermined angular intervals. The injection tube 13 and the like are formed to protrude. Further, FIG.
As shown in FIG. 0 and FIG. 13, a tail seal 11 for preventing infiltration of muddy water is similarly provided between the tail end of the rear shield body 9 and the outer peripheral surface of the lining segment 12.

[0007]

The shield machine 6 having such a structure is connected to the above-mentioned entrance packings 3 and 4.
When the inner bent portion 7 and the tail end of the rear shield body 9 pass through the entrance packing 3 on the face K, the following phenomenon occurs. <When the middle bent portion passes> That is, as shown in FIG. 11, the pressure of the muddy water W is constantly applied to the entrance packing 3 on the face K side. For this reason, when the center bent portion 7 passes through the entrance packing 3 on the face K under pressure, the opening 3a of the entrance packing 3 is formed.
Is suddenly pushed into the middle bend portion 7 by the pressure of the muddy water W and strongly strikes the middle bend seal 10, and the shock causes the middle bend seal 10 to be broken or damaged.

<When the Backfill Injection Pipe or the Grease Injection Pipe Passes> As shown in FIG. 12, when the backfill injection pipe 13 passes through the entrance packing 3 on the face K, the entrance packing 3 is used for backfill injection. The gap S,
S is generated, and a large amount of muddy water W spouts from the gaps S, S. In addition, at this time, if the distance between the entrance packings 3 and 4 is set to be equal to or less than the length of the backfill injection pipe 13 in the propulsion direction, the entrance packing 4 on the shaft side is used.
There is a risk that gaps S and S will also be generated between the backfill injection pipe 13 and the muddy water W passing through both the entrance packings 3 and 4 and jetting into the shaft. Such a phenomenon also occurs not only when the backfill injection pipe 13 but also, for example, a grease injection pipe (not shown) or another convex portion is formed on the outer peripheral surface of the rear shield body 9.

<When Passing Through the Tail End> As shown in FIG. 13, when the tail end of the rear shield body 9 passes through the entrance packing 3 on the face K, the opening 3a of the entrance packing 3 becomes muddy as described above. The end seal 11 is strongly hit by water pressure, and the end seal 11 is broken or damaged. Conventionally, in order to prevent the seepage of the muddy water and the damage to the center-fold seal 10 and the end seal 11, the center-fold portion 7, the backfill injection pipe 13 and the like are provided with a face K.
Until passing through the entrance packing 3 on the side, the mud pressure is lower than the normal pressure. For this reason,
In order to prevent the collapse of the ground, a necessary auxiliary construction method must be applied over a long section until the bent part 7 and the backfill injection pipe 13 pass through the entrance packing 3.
For this reason, there are drawbacks that extra time is required for construction and construction costs are high.

Therefore, the present invention prevents the leakage of muddy water from the entrance packing and the damage of the seal of the shield machine, even when the outer peripheral surface of the shield machine is uneven.
In addition, an object of the present invention is to provide a method for protecting a starting wellhead capable of shortening an auxiliary construction section.

[0011]

According to the present invention, there is provided a method for protecting a starting wellhead, comprising the steps of:
In addition, two annular entrance packings 18, 18 made of an elastic body are provided at a predetermined interval in the propulsion direction A of the shield machine 6, and the two entrance packings 18, 1 are provided.
8, the shield excavator 6 is inserted and propelled, and the front and rear shield main bodies 8, 9 of the shield excavator 6 are formed with concave portions 7, 11 such as a bent portion, a tail seal, etc. And the like, when the protruding portion 13 passes through the entrance packing 18 on the rear side of the propulsion direction A, that is, on the wellhead side,
Filling water having a pressure substantially equal to the muddy water pressure W of the face is poured into the outer peripheral surfaces of the front and rear shield bodies 8 and 9, the inner wall surface 15 a of the starting wellhead 15, and the hollow portion B defined by the entrance packings 18 and 18. After filling, the concave portions 7 and 11 such as the center bent portion and the tail seal and the convex portion 13 such as the backfill injection pipe pass through the entrance packing 18 on the front side in the propulsion direction A, that is, the face side, and then the filling of the hollow portion B is performed. The water is discharged and the hollow portion is opened to the atmosphere.

In the above description, the muddy water W of the face K is filled as filling water into the hollow portion B. Further, the concave portions 7 and 11 such as the center bent portion and the tail seal and the convex portions 13 such as the back-filling injection pipe are formed. It is practically preferable to provide the two entrance packings 18 with a distance exceeding the length in the propulsion direction A.

[0013]

Operation The operation of the above-described starting well protection method will be described. When the concavo-convex portion formed on the outer peripheral surface of the shield body passes through the rear side of the propulsion direction, that is, the wellhead side entrance packing, the outer peripheral surface of the shield body, the inner wall surface of the starting wellhead, and the inside of the hollow part defined by both entrance packings By filling the filling water at a pressure substantially equal to the muddy water pressure of the face, the pressure applied to the front side of the entrance packing on the front side in the propulsion direction, that is, the face side, is made the same pressure, whereby the uneven portion is substantially in a no-load state. After passing through the entrance packing, the filling water is blocked by the entrance packing on the rear side in the propulsion direction, that is, on the wellhead side, and does not leak. Further, after the uneven portion passes through the entrance packing on the front side in the propulsion direction, that is, the face side, the filling water is discharged to open the hollow portion to the atmosphere, so that the uneven portion places the entrance packing substantially in a no-load state. And the muddy water of the face is blocked by the entrance packing on the front side in the propulsion direction, that is, the face side, and does not leak.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the structure of a protective device as an example for carrying out the protective method of the present invention, and FIGS.
FIG. 2 is an enlarged side view showing the structure of the presser fitting shown in FIG.
It is the same front view. Since the shield machine shown in the present embodiment is the same as that described above, the same reference numerals are given here and the description is omitted.

The illustrated protective device shown in FIG.
4 is installed in a cylindrical starting wellhead 15. This protection device is composed of two identical seal structures 16 and 17 provided on the inner wall surface 15a of the starting wellhead 15.
And a pipe line 30 for guiding the muddy water W of the face K between the seal structures 16 and 17.

An annular recess 15b having an inner diameter larger than the diameter of the starting well 15 is formed at the center of the inner wall surface 15a of the starting well 15. This recess 15
b, one sealing structure 16
Is attached, and the other seal structure 17 is the side wall 1 of the shaft.
4 is attached to the inner peripheral wall 14a. Seal structure 1
The entrance packings 18 into which the shield machine 6 is inserted are held at the entrance holes 6 and 17 so as to coincide with the center of the starting wellhead 15, respectively. This entrance packing 18
The above-mentioned lining segment 12 has a ring shape in which an opening 18a having an inner diameter smaller than the outer diameter of the lining segment 12 is formed, and is formed of, for example, an elastic body such as rubber.

At the outer peripheral edge of the entrance packing 18, a plurality of presser fittings 19 are arranged at predetermined angular intervals on the same circumference centering on the starting wellhead 15. As shown in detail in FIGS. 2 (A) and 2 (B), each presser fitting 19 is fixed with an entrance packing 18 and a pair of washers 20, 20 together with a fixing tool 21 so as to form a side wall 15 c of the recess 15 b and an inner peripheral wall of the side wall 14 of the shaft. 14a. The holding metal 19 is provided with an anchor bolt 22
And a first plate 24 fixed to each of the walls by a nut 23 screwed thereto, and a second plate which is pivotally attached to the first plate 24 via a pin 25, thereby being swingable.
And a stopper 27 for restricting the rotation of the second plate 26 in the counterclockwise direction. In the above structure, the second plate 26 rotates clockwise about the pin 25, but the rotation in the counterclockwise direction is restricted by the upper portion of the stopper 27 abutting on the first plate 24.

The distance L between the entrance packings 18 exceeds the length in the propulsion direction A of the uneven portion such as the backfill injection pipe 13 formed on the outer peripheral surface of the rear shield body 9 of the shield machine 6. Dimensions are set. That is,
Backfill injection pipe 13 or grease injection pipe or bent part 7
It is sufficient that the concave and convex portions such as the above do not pass through both the entrance packings 18, 18 at the same time. In this embodiment, the interval is set to exceed the length of the back-filling injection pipe 13 having the longest dimension in the propulsion direction A.

One end 31a of the pipe passage 30 is formed on the inner wall surface 15 of the starting wellhead 15 on the left side of the seal structure 16 on the face K side.
a, the other end 31b of which is connected to a water pipe 32 via a valve 33, and one end 32a serving as a filling port and a drain port for muddy water.
The other end 32b is disposed on the inner wall surface 15a between
Includes a water supply pipe 32 connected to a mud tank (not shown) via a valve 34. In this piping structure, the valve 3
When the valve 3 is opened and the valve 34 is closed, the muddy water W is filled in the hollow portion B, and the pressure in the hollow portion B becomes equal to the pressure of the muddy water W. Further, when the hollow portion B is filled with the muddy water W, if the valve 33 is closed and the valve 34 is opened, the muddy water W in the hollow portion B is discharged to the muddy water tank side, and the inside of the hollow portion B is discharged. The pressure becomes almost equal to the atmospheric pressure. The muddy water W may be discharged from the hollow portion B by providing a suction pump on the side of a muddy water tank (not shown) and suctioning and discharging the water by the suction pump.

Next, a method for protecting the starting wellhead with the protection device having the above-described configuration will be described with particular reference to FIGS. First, before the shield machine 6 is propelled, the valve 33 of the water pipe 31 and the valve 34 of the water pipe 32 are closed. Then, the shield machine 6 described above is installed concentrically facing the entrance side of the starting wellhead 15 and is moved in the propulsion direction A. During this movement, the back surface of the stopper 27 of the holding member 19 abuts on the outer peripheral surface of the front shield body 8 of the shield machine 6, and the stopper 27 and the second plate 2
6 is rotated clockwise about the pin 25. Further, the opening 18a of the entrance packing 18 is moved by the second plate 26 so that the face K is cut as shown in FIG.
Elastically deformed to the side.

The shield machine 6 is connected to both seal structures 16, 1
7 and is propelled by a predetermined distance in the direction A, the entrance packings 18, 18 and the inner wall surface 1 of the starting wellhead 15 as shown in FIG.
A hollow portion B is formed by 5 a and the shield body 8 on the front side of the shield machine 6. When the hollow portion B is formed as shown in FIG. 3, the muddy water pressure of the mud water W is applied to the front side in the propulsion direction A, that is, to the side surface on the face K side of the entrance packing 18 of the seal structure 16 on the face K side. ing. On the other hand, since the above-mentioned muddy water pressure is not applied to the entrance packing 18 of the seal structure 17 on the rear side of the propulsion direction A, that is, on the shaft side, since the hollow portion B is substantially open to the atmosphere, the shield excavation is performed. The front shield body 8 of the machine 6 is only affected by the elastic force of the entrance packing 18 which is in close contact.

Accordingly, even when the shield machine 6 is propelled in the direction A from the position shown in FIG. The middle bend seal of the bend portion 7 is not hit hard. Then, the shield machine 6 is further propelled in the direction A, and the bent part 7 is moved between the entrance packings 18 of the seal structures 16 and 17, as shown in FIG. At this time, the valve 33 on the water pipe 31 is manually opened, for example, while the shield machine 6 is stopped or the propulsion is continued. By opening the valve 33, a pressure difference is generated between the hollow portion B and the muddy water W on the left side of the entrance packing 18 of the seal structure 16. Due to this pressure difference, the muddy water W passes through the water pipe 32 and the water pipe 32 via the valve 33.
From the one end portion 32a as a filling port.

As shown in FIG. 4, when the muddy water W is filled in the hollow portion B, the muddy water W of the same pressure is filled on both sides of the entrance packing 18 of the seal structure 16 on the face K, and the pressure is in an equilibrium state. Only the elastic force of the entrance packing 18 acts on the shield machine 6. Then, in this pressure equilibrium state, the shield machine 6 is further moved in the direction A, and the entrance packing 18 on the face K is passed through the center bent portion 7. At this time, the seepage of the muddy water W into the shaft is prevented by the entrance packing 18 on the seal structure 17 side.

Then, the shield machine 6 is further propelled in the direction A from the position shown in FIG.
After moving to the face K side beyond the seal structure 16 on the side, and closing the valve 33 of the water supply pipe 31, the valve 3 of the water supply pipe 32 is closed.
When opening 4, a pressure difference similar to that described above is generated between the hollow portion B and a muddy water tank (not shown). Due to this pressure difference, the muddy water W in the hollow portion B flows into the water pipe 32 from one end 32a as a drain port and is discharged into the muddy water tank. Then, after discharging the muddy water W in the hollow portion B, the valve 34 of the water supply pipe 32 is closed. In this case, even if the muddy water W in the hollow portion B is not completely drained, the pressure in the hollow portion B may be equal to the atmospheric pressure.

As shown in FIG. 5, when the shield machine 6 is further propelled in the direction A, the backfill injection pipe 13 protruding from the rear shield main body 9 causes the entrance packing 18 of the seal structure 17 on the shaft shaft side to move. After passing through, the above-mentioned gap S is formed between the entrance packing 18 and the backfill injection pipe 13. However, since the muddy water W in the hollow portion B has already been discharged, or even if some muddy water W remains, the muddy water W has a pressure substantially equal to the atmospheric pressure. The muddy water W is waterproofed by the entrance packing 18 of the seal structure 16 on the face K side.

Further, the shield machine 6 is propelled in the direction A to move the backfill injection pipe 13 between the entrance packings 18,18. At this time, as shown in FIG. 6, since the distance L between the entrance packings 18, 18 is set to a dimension exceeding the length M of the backfill injection tube 13,
The backfill injection tube 13 does not simultaneously contact the entrance packings 18,18.

As shown in FIG. 6, when the backfill injection tube 13 is moved between the entrance packings 18, 18,
Once the shield machine 6 is stopped or the propulsion is continued, the valve 33 on the water pipe 31 is manually opened, for example, to fill the muddy water W into the hollow portion B. When the hollow portion B is in a pressure equilibrium state where muddy water W is filled,
As shown in FIG. 7, the shield propulsion unit 6 is further moved in the direction A, and the backfill injection pipe 13 is passed through the entrance packing 18 of the seal structure 16 on the face K side. During this passage, a gap S is generated between the entrance packing 18 and the backfill injection pipe 13, but the muddy water W is prevented from being flooded by the entrance packing 18 of the seal structure 17 on the shaft side. Further, since the backpacking injection pipe 13 is in contact with the backfill injection pipe 13 only by the elastic force of the entrance packing 18, the entrance packing 18 itself is not damaged by the backfill injection pipe 13.

Next, the shield excavator 6 is further propelled in the direction A from the position shown in FIG. 7, and the backfill injection pipe 13 is moved to the cutting face K side beyond the sealing structure 16 on the cutting face K side. Then, after closing the valve 33 of the water pipe 31, the valve 34 of the water pipe 32 is opened to discharge the muddy water in the hollow portion B, and thereafter, the valve 34 of the water pipe 32 is closed.

When the shield machine 6 is further propelled in the direction A, the tail seal 11 between the tail end of the rear shield body 9 and the lining segment 12, as shown in FIG.
Is the entrance packing 1 of the seal structure 17 on the shaft side.
Go through 8. However, since the muddy water in the hollow portion B has already been discharged, only the elastic force of the entrance packing 18 abutting on the tail seal 11 acts. Therefore, the tail seal 11 is not hit hard by the entrance packing 18.

The entrance packings 18, 18
When the tail seal 11 is moved during the operation, the valve 33 on the water pipe 31 is manually opened, for example, while the shield machine 6 is stopped or the propulsion is continued, so that the mud water W To be filled. When the pressure at which the hollow portion B is filled with the muddy water W is in an equilibrium state, the shield machine 6 is further moved in the direction A as shown in FIG. 9 to the entrance packing 18 of the seal structure 16 on the face K side. Pass through the tail seal 11. At this time, the seepage of the muddy water W into the shaft is prevented by the entrance packing 18 on the seal structure 17 side. The operation of filling the muddy water into the hollow portion B and the operation of discharging the muddy water are repeated each time the uneven portion is passed through the entrance packing.

According to the above-described protection method, the following effects can be obtained. (A) When the center bent portion 7 and the tail seal 11 pass through the entrance packing 18 of the seal structure 16 on the face side,
Approximately equal mud pressure is applied to both sides of the abutting entrance packing 18. Therefore, the middle packing seal 10 and the tail seal 11 passing through the entrance packing 18 are provided with the entrance packing 1 which comes into contact with the center packing seal 10 and the tail seal 11.
Only the elastic force of 8 itself acts. For this reason, breakage of the middle bend seal 10 and the tail seal 11 can be prevented.

(B) Both entrance packings 18, 18
Since the interval between them is set to be longer than the length of the backfill injection pipe 13 in the propulsion direction A, the backfill injection pipe 13 is
Even when passing through the entrance packing 18 on the side of the shaft, the entrance packing 18 on the side of the shaft is connected to the rear shield body 9.
Closely adhered to. Therefore, even if the gaps S, S are generated on both sides of the backfill injection pipe 13, it is possible to prevent the muddy water W from spouting into the shaft.

(C) Folded seal 10 and backfill injection pipe 1
3. It is possible to shorten the distance for performing the auxiliary construction method for preventing the collapse of the ground, which was indispensable until the uneven portion such as the tail seal 11 passes through the entrance packing 18, thereby shortening the construction time. In addition, construction costs can be reduced. Note that the present invention is not limited to the above-described embodiment, and the following modified embodiments are also possible.

(1) In the above embodiment, the muddy water of the face was used as the filling water for filling the hollow portion. However, for example, a muddy water tank storing the muddy water is installed in a shaft, and the muddy water of the muddy water tank is used for both entrance packings. Provide a water pipe to fill between,
The hollow portion may be filled with the muddy water of the muddy water tank at substantially the same pressure as the muddy water pressure of the face. Even with this structure,
The same effects as in the above embodiment can be obtained.

(2) In the above embodiment, the backfill injection tube 13 and the center bent portion 7 have been described as examples of the uneven portion. However, other uneven portions formed on the grease injection tube and the shield body may be used. The same can be applied.

(3) In the above embodiment, the entrance packing 18 is held by the presser fitting to prevent buckling. However, when the entrance packing buckling is not concerned due to the relationship between the muddy water pressure and the entrance packing. In such a case, it is not always necessary to provide them.

(4) Although the protective device shown in FIG. 1 and the like has two seal structures, three or more seal structures may be provided.
For example, assuming that three seal structures are provided,
If the distance between the entrance packings of the seal structure arranged on the most sides is set to be larger than the dimension in the propulsion direction of the uneven portion, the distance between adjacent entrance packings located between them is not necessarily the direction of the propulsion of the uneven portion. It is not necessary to set the dimension to exceed the length of. It is considered that the same effect can be obtained even if the above-described protection method is implemented in a protection device having such a structure.

(5) In the above embodiment, an example was described in which the valve provided on the water pipe was manually opened and closed while visually checking the propulsion distance of the shield machine, but a plurality of sensors for detecting the shield machine were used. A control unit that calculates the propulsion distance of the shield machine 6 based on the detection signals output from the plurality of sensors, and a valve drive unit that opens and closes each valve according to the open / close drive signal output from the control unit. Alternatively, the valve may be automatically opened and closed. In this case, it is possible to contribute to labor saving in addition to the effects described above.

[0039]

According to the method for protecting a starting wellhead according to the first aspect, when the uneven portion formed on the outer peripheral surface of the shield body of the shield excavator passes through the entrance packing on the face side, the surface on the face side is protected. The pressure on both sides of the entrance packing is in an equilibrium state. For this reason, only the elastic force of the entrance packing acts on the above-mentioned uneven portion, and it is possible to prevent the seal of the shield machine from being damaged. Further, when the uneven portion passes through the entrance packing on the face side, a gap is formed between the entrance packing and the uneven portion. However, the muddy water is waterproofed by the other entrance packing, so that the muddy water can be prevented from seeping out. Further, the muddy water pressure required for the face to be self-supporting does not need to be lowered until the uneven portion passes through the entrance packing on the face side, thereby making it possible to shorten the auxiliary construction section.

According to the starting wellhead protection method described in claim 2, in addition to the effect obtained by the starting wellhead protection method described in claim 1, the muddy water of the face is used as the filling water for filling the hollow portion. Therefore, there is no need to adjust the pressure between the filling water and the muddy water as in the case of supplying the filling water different from the muddy water. Therefore, the protection device can have a simple structure, and the cost can be reduced.

According to the method for protecting a starting wellhead according to the third aspect, in addition to the effect obtained by the method for protecting a starting wellhead according to the first or second aspect, both the entrance packings are long in the propulsion direction of the uneven portion. The protrusions are provided with an interval exceeding the height, so that the irregularities do not pass through both entrance packings at the same time, and even when long irregularities are provided in the propulsion direction, it is possible to reliably prevent muddy water from seeping out. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of a protective device as an example for implementing a protective method of the present invention.

2 (A) and 2 (B) are an enlarged side view and a front view showing the structure of the holding member shown in FIG. 1 in an enlarged manner.

FIG. 3 is an explanatory view showing a state in which a concavo-convex portion formed on an outer peripheral surface of a shield machine has been moved to a position closer to an entrance packing on a shaft.

FIG. 4 is an explanatory view showing a state in which a concavo-convex portion formed on an outer peripheral surface of the shield machine has been moved between two entrance packings.

FIG. 5 is an explanatory diagram showing a state in which an uneven portion formed on the outer peripheral surface of the shield machine passes through an entrance packing on the shaft side.

FIG. 6 is an explanatory view showing a state in which an uneven portion formed on the outer peripheral surface of the shield machine has been moved between two entrance packings.

FIG. 7 is an explanatory view showing a state in which an uneven portion formed on the outer peripheral surface of the shield machine passes through a transformer packing on the face side.

FIG. 8 is an explanatory diagram showing a state in which the concavo-convex portions formed on the outer peripheral surface of the shield machine pass through the transformer packing on the shaft.

FIG. 9 is an explanatory view showing a state in which the concavo-convex portion formed on the outer peripheral surface of the shield machine passes through the transformer packing on the face side.

FIG. 10 is a sectional view showing a schematic structure of a protection device provided at a starting wellhead.

FIG. 11 is a partially enlarged cross-sectional view showing a state in which the middle bent portion of the shield machine shown in FIG. 9 passes through the entrance packing on the face side.

FIG. 12 is a partially enlarged explanatory view showing a state in which a backfill injection pipe or the like protruding from an outer peripheral surface of a rear shield of the shield machine passes through an entrance packing on a face side.

FIG. 13 is a partially enlarged cross-sectional view showing a state where a tail end of the shield machine passes through an entrance packing on a face side.

[Explanation of symbols]

 7 Folded part as a concave part 11 Tail seal as a concave part 13 Backfill injection pipe as a convex part 15 Start-up well 15a Inner wall surface 16, 17 Seal structure 18 Entrance packing 19 Presser fitting 30 Pipe line 32a Filling port, discharging port A Propulsion direction

Claims (3)

(57) [Claims] 1. An inner wall made of an elastic material is provided on an inner wall surface of a starting wellhead.
Two annular entrance packings are provided at predetermined intervals in the propulsion direction of the shield excavator, and the shield excavator is inserted and propelled into both of the entrance packings, and irregularities formed on the outer peripheral surface of the shield body of the shield excavator. When passing through the entrance packing on the rear side of the propulsion direction, that is, on the wellhead side, when the outer peripheral surface of the shield body, the inner wall surface of the starting wellhead, and the hollow part surrounded by both entrance packings have a pressure almost equal to the muddy water pressure of the face. After the filling water is filled and the uneven portion passes through the entrance packing on the front side in the propulsion direction, that is, the face side, the filling well of the hollow portion is discharged and the hollow portion is opened to the atmosphere, and the starting wellhead is characterized by being opened to the atmosphere. Protection method. 2. The starting wellhead protection method according to claim 1, wherein a water pipe for guiding muddy water of the face into the hollow portion is provided, and the muddy water is filled into the hollow portion as filling water. 3. The starting wellhead protection method according to claim 1, wherein both entrance packings are provided so as to maintain an interval exceeding a length of the uneven portion in the propulsion direction.