JPH08144306A - Method for lining internal surfaces of manhole - Google Patents

Abstract

PURPOSE: To line the internal surfaces of a manhole efficiently. CONSTITUTION: An invert is removed from the bottom of a manhole 10, a spiral pipe fixing device 30 is set on a flat bottom surface 13, and a pipe producing machine 40 is set on the opening of the manhole 10. Also a spiral pipe 15 is produced by the pipe producing machine 40, and the produced spiral pipe 15 is inserted directly into the manhole 10. Then the bottom part of the spiral. pipe 15 is set movably in radial direction without moving in circumferential direction by the fixing member 33 of the spiral pipe fixing device 30, and a profile 20 is fed by the pipe producing machine 40. Thus the bottom part of the spiral pipe 15 is increased in diameter so that it is adhered closely to the internal surfaces of the bottom part of the manhole 10. Thereafter the spiral pipe 15 is increased in diameter from the bottom side upward in order, and fitted closely to the entire inner surfaces of the manhole 10.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for lining a manhole.

[0002]

2. Description of the Related Art Manholes in sewers usually have a concrete structure and are aged over time due to corrosion, external pressure, reaction of hydrogen sulfide in sewage with alkali, and cracks and damages. Since groundwater enters the cracked or damaged manhole, there is a possibility that sewage that exceeds the treatment capacity of the sewage treatment plant will flow into the sewage treatment plant from the manhole during rainy weather.

For this reason, it is necessary to rehabilitate the cracked or damaged manhole. However, when removing old manholes and rebuilding with concrete, etc.,
There is a problem in workability because the manhole must be excavated. In addition, it is necessary to block the traffic on the road where the manhole opens for a long period of time, which is extremely difficult in reality.

For such a method, Japanese Patent Laid-Open No. 5-24
No. 7993 discloses that a bottomed tubular lining material made of low density polyethylene is inserted into an existing manhole in a state of being folded small, and heating steam is introduced into the lining material to form a tubular lining material. A method is disclosed in which the shape of the manhole is restored and the restored lining material is cooled and solidified. In this lining method, after the cylindrical lining material has cooled and solidified, a heater is placed on the bottom wall of the lining material to soften it, and the softened bottom wall is pressed to form it along the shape of the invert at the bottom of the manhole. are doing.

[0005]

In the manhole lining method disclosed in the above publication, heating steam is introduced into the tubular lining material in order to restore the tubular lining material inserted into the manhole into a tubular shape. And the step of heating the bottom wall to form the shape along the invert in the manhole, and moreover, it takes a long time to cool and solidify the heated tubular lining material. There is a problem that the traffic is bad and the time to cut off the traffic on the road is long.

The present invention solves such a problem, and an object of the present invention is to provide a lining method in a manhole which has good workability and requires a short road traffic interruption time.

[0007]

A method for lining a manhole according to the present invention comprises a step of spirally winding a flexible band-shaped profile by a pipe making machine to produce a spiral pipe, and a pipe making machine. Including a step of directly inserting the spiral tube manufactured by the method into the inside through the opening of the manhole, and a step of expanding the diameter of the spiral tube manufactured by the pipe-making machine to be in close contact with the inner peripheral surface of the manhole. The above object is achieved thereby.

The spiral tube is inserted so as to reach the bottom of the manhole, and is expanded in diameter so as to be in close contact with the entire inner peripheral surface of the manhole. In this case, the lower end of the spiral tube inserted into the manhole is in a state in which the movement in the circumferential direction is restricted and can be moved in the radial direction by the spiral tube fixing device arranged at the bottom of the manhole, The profile is fed to the spiral pipe by the pipe making machine to expand the diameter.

On the other hand, the spiral tube may be inserted from the opening portion by a predetermined length and expanded in diameter so as to be in close contact with the inner peripheral surface of the tapered portion above the manhole.

In this case, after the tapered portion of the upper portion of the manhole by the spiral tube is lined, the profile is closely adhered to the inner peripheral surface of the cylindrical portion of the lower portion of the manhole for lining.

In any case, it is preferable that the spiral tube is inserted from the opening of the manhole after removing the invert provided at the bottom of the manhole.

[0012]

In the lining method for manholes according to the present invention,
The spiral pipe manufactured by the pipe making machine is directly inserted into the manhole to expand the diameter of the spiral pipe inserted into the manhole, so that the inner peripheral surface of the manhole is lined with the profile forming the spiral pipe. . The spiral tube is manufactured to reach the bottom of the manhole, and the spiral tube fixing device arranged at the bottom of the manhole restricts the rotation of the lower end of the spiral tube in the circumferential direction and can move in the radial direction. In the state, the diameter is expanded by feeding the profile to the spiral tube. The profile of the expanded spiral tube lines the entire inner peripheral surface from the opening to the bottom of the manhole.

Further, the spiral tube is expanded in a state of being inserted into the manhole by a predetermined length so that the inner peripheral surface of the taper portion above the manhole is lined. As a result, the profile forming the spiral tube lines the tapered portion of the manhole. After that, the flexible profile introduced into the manhole is closely adhered to the inner peripheral surface of the lower cylindrical portion which is continuous with the tapered portion of the lined manhole.

If the invert provided at the bottom of the manhole is removed in advance before performing the lining work, the invert is newly constructed after the lining in the manhole is completed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is carried out when the inner peripheral surface of the manhole 10 having the opening 14 at the upper end surface is lined as shown in FIG. The upper part of the manhole 10 is a truncated conical taper portion 16 having an inner diameter that decreases toward the upper side, and the lower part of the manhole 10 has a tapered portion 16.
Is a cylindrical portion 17 having a constant inner diameter.

In the lining method of the present invention, first, referring to FIG.
As shown in, the invert 11 formed at the bottom of the manhole 10 is removed. The invert 11 has a groove 11a having a semicircular cross section that is linearly arranged between a pair of sewers 12 that are in communication with each other in the manhole 10 and that face each other, and the groove 11a side is the lower side on each side of the groove 11a. Thus, the pair of upper surfaces 11b are inclined. Each end surface of the groove 11 a is in alignment with the lower part of each end surface of each sewer 12. When the invert 11 is removed, the bottom surface 13 of the manhole 10 is made flat, and the manhole 10 is placed on the flat bottom surface 13.
A spiral tube fixture 30 used to fix the lower end of the spiral tube inserted therein is installed.

The spiral tube fixture 30 is, as shown in FIG.
Manhole 1 installed on the bottom surface 13 of manhole 1
Four ring-shaped reinforcing members 31 fitted in 0
And a guide member 32 arranged in a cross shape in the ring-shaped reinforcing member 31. The guide member 32 has four guide portions 32a each extending in the radial direction (radial direction) of the bottom surface 13 of the manhole 10, and the arc-shaped reinforcing member is provided between the tip portions of the guide portions 32a. Three
1 is arranged. The inside of each guide portion 32a is hollow, and a guide hole 32b is formed on the upper surface over substantially the entire length of each guide portion 32a.

A fixing member 33 is slidably arranged on each guide portion 32a along the upper surface of each guide portion 32a. Each fixing member 33 has a fitting groove 33 extending in a direction orthogonal to the guide hole 32b of each guide portion 32a.
a fixed main body portion 33a having an upward U shape having b;
The guide hole 3 is attached to the lower surface of each fixed main body 33a.
Locking part 33 that has entered each guide part 32a through 2b
c (see FIG. 1). And the locking portion 33c
Is locked to the tip of a compression spring 34 (see FIG. 1) arranged in each guide portion 32a, and the entire fixing member 33 is biased in the radial direction of the bottom surface 13 of the manhole 10. It has become.

In the spiral tube fixing device 30 having such a structure, for example, each guide member 32 and each reinforcing member 31 are separated from each other through the opening 14 on the upper surface of the manhole 10 into the manhole 10. It is carried in and assembled in the manhole 10.

When the spiral tube fixture 30 is placed in the bottom surface 13 of the manhole 10, a pipe making machine 40 is placed on the opening 14 of the manhole 10, as shown in FIG. A flexible strip-shaped profile 20
When the pipe-making machine 40 is fed, the pipe-making machine 40 spirally winds the fed profile 20 by a plurality of pipe-making rollers arranged on the circumferential surface, each having a predetermined spiral angle. The spiral tube 15 is manufactured by turning. Manufactured spiral tube 15
Has an outer diameter smaller than the inner diameter of the opening 14 of the manhole 10, and is inserted directly into the manhole 10 from the pipe making machine 40 through the opening 14.

FIG. 4 is a cross-sectional view of the profile 20 which constitutes the spiral tube 15 introduced into the manhole 10.
The profile 20 has a strip plate-shaped substrate body 21 whose inner surface is flat when wound in a spiral shape. One side edge portion of the substrate body 21 is continuous with the step portion 22 located outside by the thickness of the substrate body 21.

In the vicinity of the other side edge of the board body 21, a fitting projection 25 projecting in a direction opposite to the inner surface of the board body 21.
Are provided along the longitudinal direction. This fitting ridge 2
Reference numeral 5 is configured such that an insertion portion 25b having a semicircular cross section is provided at the tip of a column portion 25a standing upright with respect to the substrate body 21.

A fitting rib 26 having a cross-sectional space 26a into which the fitting projection 25 can be fitted is provided at the side edge of the step portion 22 on the substrate body 21 side so as to project outward. Has been. The fitting rib 26 is configured such that a flange portion 26c that is parallel to the step portion 22 is provided outside the fitting portion 26b that protrudes outward in a semicircular cross section surrounding the space portion 26a. Space portion 26 of fitting rib 26
A wire 28 is arranged between a and the fitting protrusion 25.

The fitting rib 26 and the fitting projection 25 of the step portion 22
In between, there are three reinforcing ribs 27 having a T-shaped cross section.
The step portions 22 are provided so as to project outward.

The profile 20 having such a structure is integrally formed of a flexible synthetic resin such as polyethylene, polypropylene, vinyl chloride, etc. When the profile 20 is spirally wound by the pipe making machine 40, Profile 2
Adjacent fitting protrusions 25 are fitted into the fitting ribs 26 of 0. At this time, the wire 28 is fitted between the fitting rib 26 and the fitting protrusion 25. As a result, the fitting rib 26 and the fitting projection 25 are fitted to each other in the profile 20 to form the spiral tube 15 having a predetermined inner diameter.

The fitting rib 26 and the fitting ridge 25 are slidable with respect to each other, but the wire rod 28 interposed therebetween prevents them from sliding. Then, when the fitting protrusion 25 is fitted in the fitting rib 26, a delayed hardening urethane resin is applied to the fitting rib 26.

The spiral tube 15 produced by the pipe making machine 40
However, as shown in FIG. 5, when reaching the vicinity of the bottom surface 13 of the manhole 10, the pipe making work by the pipe making machine 40 is temporarily stopped.
Suspended. Then, the worker makes the spiral pipe 1 from the internal space formed by each pipe making roller in the pipe making machine 40.
Go into 5 The worker who entered the spiral tube 15
Each fixing member 33 of the spiral tube fixing device 30 arranged on the bottom surface 13 of the manhole 10 is moved in the direction approaching the spiral tube 15 against the biasing force of each compression spring 34, and the spiral tube 15 is moved. Fitting projection 25 of the profile 20 at the lower end
And the side edge portion of the peripheral portion is fitted into the fitting groove 33b of the fixing main body portion 33a of each fixing member 33, as shown by the chain double-dashed line in FIG.

Bolt holes 33d (see FIGS. 2 and 4) are formed on the inner surface of each fixed main body portion 33a, and when the side edge portion of the profile 20 is fitted in the fitting groove 33b, A bolt is screwed into each bolt hole 33d, and the lower end portion of the spiral tube 15 fitted in the fitting groove 33b is fixed to the fixed body portion 33a by each bolt.

As a result, the fixing members 33 are urged only by the urging force of the compression spring 34 in the radial direction on the outer peripheral side of the manhole 10, and the movement in the circumferential direction is restricted. . In such a state, the spiral tube 15
Despite the fact that each fixing member 33 is biased,
It is kept at a constant inner diameter.

Thereafter, the pipe making machine 40 restarts the pipe making of the spiral pipe 15, and the wire rod 28 interposed between the fitting rib 26 and the fitting projection 25 of the spiral pipe 15 is removed. The profile 20 is newly fed to the spiral tube 15 in the manhole 10,
Profile 2 of spiral tube 15 whose movement in the circumferential direction is restricted
A force is applied to 0 in the spiral direction. As a result, the fitting portions of the fitting projections 25 and the fitting ribs 26 of the adjacent profiles 20 slide with each other, and the profile 20 forming the spiral tube 15 is propelled in the spiral direction. Since the movement of the profile 20 in the circumferential direction is restricted by each fixing member 33, the profile 20 at the lower end portion of the spiral tube 15 is fixed by each compression spring 34. By means of 33, they are respectively expanded only in the radial direction, and as shown in FIG. 6, the diameter is expanded so as to be in close contact with the inner peripheral surface of the lower end of the cylindrical portion 17 of the manhole 10.

In this state, the spiral pipe 15 is further manufactured by the pipe making machine 40, and the profile 20 forming the spiral pipe 15 is propelled in the spiral direction. The diameter is increased in order from and the state becomes close to the inner peripheral surface of the cylindrical portion of the manhole 10.

In this case, the delayed-curing urethane resin applied to the fitting ribs 26 of the profile 20 forming the spiral tube 15 is fitted into the fitting ribs 26 because the hardening has not started. The fitting protrusion 25 smoothly slides with respect to the fitting rib 26, and the diameter of the spiral tube 15 is surely expanded.

In this way, the diameter of the spiral tube 15 of the manhole 10 is increased in order from the lower side, and the spiral tube 15 is brought into close contact with the inner peripheral surface of the cylindrical portion 17 of the manhole 10.
Also in the tapered portion 16 above the manhole 10, the diameter of the spiral tube 15 is sequentially increased from the lower side, and the spiral tube 1 is expanded.
5 is brought into close contact with the inner peripheral surface of the tapered portion 16 of the manhole 10. As a result, as shown in FIG. 7, the entire inner peripheral surface of the manhole 10 is in a state in which the spiral pipe 15 is in close contact with the entire inner peripheral surface of the manhole 15,
It is lined by a profile 20 which constitutes the spiral tube 15. When this happens, the manhole 10
The spiral tube 15 inserted therein is cut in the vicinity of the opening 14 of the manhole 10, and the pipe manufacturing machine 40 is removed.

The upper part of the manhole 10 has a truncated conical taper portion 16 whose inner diameter gradually decreases toward the upper side.
Since the lower side of the tapered portion 16 is a cylindrical portion 17 having a constant inner diameter, the profile 20 has an inner peripheral surface of the tapered portion 16 at the boundary between the two. The cylindrical portion 17 is bent so as to come into close contact with the inner peripheral surface of the cylindrical portion 17.

When the entire inner peripheral surface of the manhole 10 is lined with the profile 20, as shown in FIG. 7, the portion covering the end surface of each sewer 12 in the spiral pipe 15 lining the inner peripheral surface of the bottom of the manhole 10. Are cut and removed. As a result, each sewer 12 is in communication with the inside of the manhole 10 lined with the profile 20. Then, a water blocking material such as cement or epoxy resin is filled between the peripheral portion of each sewer 12 and the spiral pipe 15 to perform a water shut off process between each sewer 12 and the spiral pipe 15.

Then, on the bottom surface 13 of the manhole 10,
Epoxy resin or the like is applied and waterproofing is performed, and then a backfill material is filled between the manhole 10 and the spiral tube 15. Then, the invert 11 is constructed by concrete on the bottom surface 13 in the spiral tube 15. Therefore, the spiral tube fixture 30 installed on the bottom surface 13 of the manhole 10
Is embedded in the concrete invert 11. This completes the lining of the manhole 10.

FIG. 8 is a sectional view of the manhole 10 showing a step of another embodiment of the manhole lining method of the present invention. In this embodiment, first, the bottom invert 1
The pipe making machine 40 is installed on the opening 14 of the manhole 10 from which 1 is removed, and the spiral pipe 15 having a predetermined inner diameter is made by the profile 20 fed to the pipe making machine 40. . Then, the manufactured spiral tube 15 is directly inserted into the manhole 10 through the opening 14.

In this case also, the fitting rib 26 of the profile 20 is in a state in which the delayed hardening urethane resin is applied, and the fitting projection 25 is fitted in the fitting rib 26. .

In this way, over a predetermined length,
When the spiral pipe 15 is inserted into the manhole 10, the pipe manufacturing by the pipe manufacturing machine 40 is stopped and the lower end of the spiral pipe 15 is expanded. In this case, the worker who enters the manhole 10 through the pipe making machine 40 forcibly forces the spiral pipe 15
The profile 20 is spirally propelled and the fitting ribs 26 and the fitting projections 25 of the profile 20 are slid relative to each other, and the diameter of the spiral tube 15 is sequentially increased from the lower end to the upper side. The diameter-enlarged spiral tube 15 is brought into close contact with the inner peripheral surface of the upper tapered portion 16 of the manhole 10 in order from the lower side.
And the spiral tube 15 inserted into the manhole 10
As shown in FIG. 9, the taper portion 16 provided on the upper portion of the manhole 10 is entirely adhered to the inner peripheral surface thereof.

In such a state, as shown in FIG. 10, the spiral pipe 15 is cut in the opening 11 of the manhole 10, and the pipe making machine 40 installed on the opening 11 of the manhole 10 is cut. Will be removed. Then, the profile 20 for lining the inner peripheral surface of the cylindrical portion 17 at the lower portion of the manhole 10 is newly carried into the manhole 10. As this profile 20, for example, the same one as the profile 20 forming the spiral tube 15 is used, and an operator who has entered the manhole 10 continues the profile 20 forming the spiral tube 15 to make the manhole 10
The inner peripheral surface of the cylindrical portion 17 having a constant inner diameter is pressed spirally in order from the upper side.

In this case, since the profile 20 constituting the spiral tube 15 and the profile 20 newly introduced into the manhole 10 have the same cross-sectional shape, both can be easily continued in an aligned state. Therefore, there is no possibility of forming a gap between the profile 20 of the spiral tube 15 lining the inner peripheral surface of the tapered portion 16 and the profile 20 lining the inner peripheral surface of the cylindrical portion 17.

Further, since the profile 20 newly introduced into the manhole 10 does not require the fitting portions to slide with each other, the fitting rib 26 is coated with the delayed hardening urethane resin. Instead, profile 2
It is preferable that the hot melt adhesive is applied in advance to the outer surface of the substrate 21 adjacent to the fitting protrusion 25 fitted in the stepped portion 22 at 0.

Thus, as shown in FIG. 11, when the profile 20 is lined up to the inner peripheral surface of the lower end portion of the cylindrical portion 17 close to the flat bottom surface 13 of the manhole 10, the profile 20 is cut. To be done.

After that, each sewer 12 of the profile 20 lining the lower end of the cylindrical portion 17 of the manhole 10
The part covering the end face of is cut and removed. As a result, each sewer 12 is in communication with the inside of the manhole 10 lined with the profile 20. Then, a water blocking material such as cement or epoxy resin is filled between the peripheral edge of each sewer 12 and the profile 20 to perform a water blocking process between each sewer 12 and the profile 20.

Then, the bottom surface 13 of the manhole 10 is coated with an epoxy resin or the like to stop water, and then the spiral tube 15
At the bottom inside, the invert 11 is constructed by concrete. In the case of the present embodiment, since the inner peripheral surface of the manhole 10 and the profile 20 are in close contact with each other, it is not necessary to fill the backfill material between them, and the invert 11 is constructed. By doing so, the lining of the inner peripheral surface of the manhole 10 is completed.

In the case of the present embodiment, the inner peripheral surface of the tapered portion 16 of the manhole 10 is lined with the spiral tube 15, and then the inner peripheral surface of the cylindrical portion 17 of the manhole 10 is newly carried into the manhole 10. The lining was done in order from the upper side by the
The linings of No. 7 may be lined in order from the bottom surface 13 side to the upper side depending on the profile introduced into the manhole 10. In this case, it is difficult for the profile lining the inner peripheral surface of the cylindrical portion 17 to be in alignment with the profile 20 forming the spiral tube 15 with the tapered portion 16 lined,
It is not necessary to use a profile with a cross-sectional shape similar to profile 20. The profile 20 forming the spiral tube 15 and the profile lining the cylindrical portion 17 are connected to each other by welding or the like.

In each of the above embodiments, the manhole 10
After removing the invert 11 provided at the bottom of the inside,
Although the inner peripheral surface of the manhole 10 is lined, the inside of the manhole 10 may be lined by inserting the spiral tube 15 without removing the invert 11. In this case, if necessary, invert 11
Is covered with a plastic cover member or the like and fixed by an anchor member,
May be repaired.

Further, the spiral tube 15 inserted into the manhole 10 is manufactured by simply fitting the side edges of the profile 20 to each other. However, when the inner diameter of the spiral tube 15 is large, the profile is reduced. When the side edges of 20 are fitted to each other, a wire material is sandwiched between the fitting portions to increase the slide resistance of the fitting portion, and when the diameter of the spiral tube 15 is expanded, the wire material is It may be removed to reduce the sliding resistance of the fitting portion.

[0049]

As described above, according to the lining method for a manhole of the present invention, the spiral tube constituted by the flexible profile is introduced into the manhole and the diameter of the spiral tube is expanded to thereby increase the inner circumference of the manhole. Since the surface is lined, no special device for heating or cooling is required, and the work in the manhole is simple, and the work efficiency is significantly improved. By expanding the diameter with the spiral tube inserted to the bottom of the manhole,
It is also possible to continuously line the inner peripheral surfaces of the upper tapered portion and the lower cylindrical portion of the manhole. Further, by lining the upper tapered portion of the manhole with the spiral tube and then lining the lower cylindrical portion, the profile can be lined in a state of being in close contact with the entire inner peripheral surface of the manhole.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a manhole showing one step in an embodiment of a method for lining a manhole according to the present invention.

FIG. 2 is a perspective view showing an example of a spiral tube fixture used in the lining method.

FIG. 3 is a vertical sectional view of a manhole showing another step of the lining method.

FIG. 4 is a cross-sectional view of a profile used in the lining method.

FIG. 5 is a vertical cross-sectional view of a manhole showing still another step of the lining method.

FIG. 6 is a longitudinal sectional view of a manhole showing still another step of the lining method.

FIG. 7 is a vertical cross-sectional view of a manhole lined with a profile by the lining method.

FIG. 8 is a longitudinal sectional view of a manhole showing one step in another embodiment of the method for lining a manhole according to the present invention.

FIG. 9 is a longitudinal sectional view of a manhole showing another step of the lining method.

FIG. 10 is a longitudinal sectional view of a manhole showing still another step of the lining method.

FIG. 11 is a longitudinal sectional view of a manhole showing a state of being profile-lined by the lining method.

[Explanation of symbols]

 10 Manhole 11 Invert 11b Bottom 12 Sewer 13 Bottom 14 Opening 15 Spiral Pipe 16 Taper 17 Cylindrical 20 Profile 21 Board Body 22 Step 25 Fitting Ridge 26 Fitting Rib 30 Spiral Pipe Fixture 32 Guide Member 33 Fixing Member 34 Compression spring 40 Pipe making machine

Claims (6)

[Claims] 1. A flexible strip-shaped profile,
The process of making a spiral tube by spirally winding with a pipe making machine, the process of directly inserting the spiral pipe made by the pipe making machine into the inside through the opening of the manhole, and the process made by the pipe making machine And a step of expanding the diameter of the spiral tube and bringing it into close contact with the inner peripheral surface of the manhole, the lining method in the manhole. 2. The manhole lining method according to claim 1, wherein the spiral tube is inserted so as to reach a bottom portion of the manhole and is expanded in diameter so as to be in close contact with the entire inner peripheral surface of the manhole. 3. The lower end portion of the spiral pipe inserted into the manhole is in a state in which the spiral pipe fixing member arranged at the bottom of the manhole restricts the movement in the circumferential direction so that the spiral pipe can move in the radial direction. The method of lining a manhole according to claim 2, wherein the pipe is expanded by feeding the profile to the spiral pipe by a pipe making machine. 4. The lining method for a manhole according to claim 1, wherein the spiral tube is inserted by a predetermined length from the opening and expanded in diameter so as to be in close contact with the inner peripheral surface of the taper part on the upper part of the manhole. 5. The manhole lining method according to claim 4, wherein after lining the tapered portion of the upper portion of the manhole by the spiral tube, a profile is brought into close contact with the inner peripheral surface of the cylindrical portion of the lower portion of the manhole for lining. 6. The method of lining a manhole according to claim 1, wherein the spiral tube is inserted from an opening of the manhole after removing an invert provided at a bottom of the manhole.