JP3176819B2 - Cable laying method and manhole used for it - 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 laying cables for power and communication using underground pipes under roads and the like, and a manhole used for the method.

[0002]

2. Description of the Related Art Recently, due to demands for space utilization, etc.
The transition to various underground cable systems for communications etc. is being actively pursued. In this case, a plurality of manholes for connecting cables are provided at predetermined intervals, cables are extended between these manholes, and cables are connected in the manholes to form a predetermined circuit network. And

Conventionally, there are the following two methods for laying cables underground or underground.

A method of directly burying a directly buried cable (see Japanese Patent Application Laid-Open No. 6-109931). A connection box is provided in the manhole, and the cables are connected to each other in the connection box.

As shown in FIG. 8, a manhole (hereinafter, referred to as a first manhole) 1 for cable connection is provided about every 1 km.
A manhole (hereinafter referred to as a second manhole) 2 for work is installed at intervals of about 200 m between the manholes 1, these manholes are connected by an underground pipe 3, and the second manhole 2 is connected through the pipe 3. And laying the cable 4 between the first manholes 1 and 1. The connection box 5 is provided in the first manhole 1 in the same manner as described above.

In the above method, a corrugated rigid flexible electric conduit or the like is used for the underground conduit 3. Second manhole 2
Is for pulling or sending out the cable 4 at an intermediate position when the cable is extended.
From the frictional force of the cable 4 and the allowable tension of the cable 4, etc.
Generally, they are installed at intervals of 0 m or less.

[0007]

By the way, such cable laying is often carried out under the road, and there is a demand to carry out the work as short as possible and in a short section as far as traffic regulation is concerned.

According to this method, the steps of excavating a road, burying a cable, and restoring a road must be repeated for each short section. And increase construction costs.

On the other hand, in the case of the other method, once the first and second manholes are installed, the conduit can be formed from the inside of the manhole by using a digging device or the like, and the cable can be extended in the manhole. There is an advantage that large-scale civil engineering work is not required, and the work can be performed easily and in a short time. In addition, since the construction section is limited to the manhole, the impact on traffic can be minimized.

However, disadvantages of this method include:
While a large number of second manholes are required, the manholes are left as permanent structures in the ground. The former causes an increase in construction or material costs, and the latter creates a need for regular management.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a cable laying method and a cable laying method capable of minimizing the number of manholes as permanent structures remaining in the ground. To provide manholes for use.

[0012]

In order to achieve the above object, a cable laying method according to claim 1 of the present invention comprises:
Between the first manholes for cable connection, a second manhole for removal work is installed, these manholes are connected by underground conduits, and the cable is connected between the first manholes through the conduits. After the extension, the passing portion of the cable introduced from one conduit into the second manhole and led out to the other conduit is stored in a protective tube connecting the two conduits to protect the passage portion. The second manhole was removed and the protective tube was buried underground.

[0013] The present invention described in claim 2 provides the present invention in claim 1.
In the above described cable laying method, the protection tube is housed in the pipeline in advance so as to be slidable.

The present invention according to claim 3 provides the present invention according to claim 1.
In the above described cable laying method, the protective tube is housed so as to be slidably movable between the conduit and an outer tube covering the outside of the conduit.

According to a fourth aspect of the present invention, there is provided a manhole according to the present invention, wherein a side wall having a length corresponding to the depth of a buried pipe is provided, and the pipe is formed at a lower portion of the side wall and opened downward. With the introduction port.

The present invention described in claim 5 provides the present invention according to claim 4.
In the manhole described above, the side wall is formed in a tapered shape that gradually decreases toward a lower side.

The present invention described in claim 6 is directed to claim 4
In the described manhole, the side wall can be divided into a plurality from the top side to the bottom side.

The present invention according to claim 7 provides the present invention according to claim 4.
The described manhole further comprises a bottom wall, and on the bottom wall,
A slit-shaped opening having a width substantially equal to the outer diameter of the conduit is formed continuously with the open end of the inlet.

[0019]

According to the first aspect of the present invention, the second manhole, which has been a permanent structure, is removed, and the cable inside the second manhole is protected by a protection tube and buried underground.

According to the second and third aspects of the present invention, the protection tube is pulled out from one of the conduits in the second manhole and connected to the other conduit while accommodating the cable. .

Further, according to the present invention, the manhole can be moved upward by using the inlet as a passage portion of the conduit.

According to the fifth aspect of the present invention, the influence of earth pressure can be reduced, and the force for pulling the manhole out of the ground can be reduced.

Further, according to the present invention, it is possible to reduce the weight when removing the manhole.

According to the present invention, the opening can be a portion through which the protective tube passes, and the opening area can be minimized.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

As described above, referring to FIG. 8, the first manholes 1 for cable connection are provided at intervals of about 1 km. Second manholes 2 are installed between the manholes 1 at intervals of about 200 m. These manholes 1 and 2 are connected by an underground conduit 3, and a cable 4 is extended between the first manholes 1 and 1 through the conduit 3.

FIG. 1A particularly shows the state around the second manhole 2 at this time. As shown, the second
In the manhole 2, pipe lines 3a and 3b protrude from opposing positions. Then, the cable 4 passes through the pipelines 3a and 3b and passes through the second manhole 2 in an exposed state. If a tensile force or the like is applied to the passing or exposed portion, the wire drawing becomes easy.

In particular, the second manhole 2 is formed so as to be removable. Specifically, a structure as shown in FIG. 2 is employed. The second manhole 2 is made of concrete and is divided into upper and lower three-tiered pieces 2a, 2 so that the second manhole 2 can be divided from above to below or from the top to the bottom.
b, 2c. And the second manhole 2
It is formed in a tapered shape with a rectangular cross section in which the bottom side is smaller than the top side. The length of the side wall 2d of the second manhole 2, that is, the dimension in the height direction is substantially equal to the depth dimension from the ground surface to the bottoms of the pipelines 3a and 3b.

The upper piece 2a has a top wall (not shown), which is partially open to allow a person to enter and exit. The opening can be freely opened and closed by a lid (not shown). The middle piece 2b is formed in a rectangular frame shape.

The lower piece 2c has a side wall 6a formed in a rectangular frame shape and a bottom wall 6b formed at the bottom thereof. An introduction port 7 is formed at a position facing the side wall 6a so as to project the ends of the conduits 3a and 3b in a penetrating state.
The inlet 7 is conventionally a simple circular hole, but is formed in a groove shape opening to the bottom in the present embodiment. That is, the introduction port 7 has an upper part defined by the semicircular part 8 and a lower part defined by the opposing parallel part 9.
The diameter of the semicircular portion 8, that is, the width formed by the parallel portion 9 is determined by the conduits 3 a, 3
The value is substantially equal to and slightly larger than the outer diameter of b. The bottom wall 6b has a slit-shaped opening 10 which is continuous with the open end, that is, the lower end of the inlet 7. Therefore, the width of the opening 10 is also equal to the width of the parallel portion 9 and is slightly larger than the outer diameter of the conduits 3a and 3b (see FIG. 3). Thus, the inlet 7 and the opening 10 are formed in a continuous U-shaped slit shape.

As shown in FIG. 1A, a protective tube 1 for accommodating an exposed portion of the cable 4 is provided in a conduit 3a.
1 is stored in advance. The protection tube 11 is slidably movable in the pipeline 3a, and is fixed in the pipeline 3a by a stopper (not shown) or the like so that the stored state is maintained when the cable 4 is extended.

In the state shown, the pipes 3a, 3b
The upper surface portions thereof are in contact with or very close to the semicircular portion 8 of the inlet 7 and are separated from the mud under the opening 10 by a certain distance.

Now, after extending the cable 4 in such a state, as shown in FIGS. 1 (b) and 3, the protective tube 11 is slid and pulled out from the conduit 3a to expose the cable 4. While inserting the portion, it is inserted into the conduit 3b. In this case, the ends of the conduits 3a and 3b and the protective tube 11
Are overlapped with each other, so that the protective tube 11 is connected to both conduits 3a and 3a.
b is connected. The pipes 3a and 3b and the protection pipe 1
1 is sealed with a sealing member 12 such as a vinyl tape.

Next, the second manhole 2 is removed as shown in FIG. Specifically, the upper piece 2a and the middle piece 2b are sequentially pulled up and taken out, and finally the lower piece 2c is taken out from the ground and taken out. At this time, in particular, the groove-shaped inlet 7 and the opening 10 connected thereto are
The passage of the conduits 3a, 3b and the protective tube 11 is permitted. The pieces 2a are easily pulled up by hooks (not shown) provided on the pieces 2a.

Further, mud is injected into the hole 13 formed by removing the second manhole 2, and as shown in FIG. 3b and the protection tube 11 are embedded in the ground, and the installation of the cable 4 is completed.

According to such a cable laying method, since the second manhole 2 is removed, only the first manhole 1 as a permanent structure to be left in the ground is the first manhole 1, and the number of the manholes can be suppressed to the minimum. it can. Therefore,
Since only the first manhole 1 needs to be managed, the management is greatly facilitated. In addition, since only a minimum number of hollow portions called manholes are provided in the ground, a decrease in ground strength can be minimized.

Further, since the protective tube 11 is slid, the connecting operation is facilitated, and the working time can be reduced.

Further, since the second manhole 2 can be removed and reused by forming the inlet 7 and the opening 10 as described above, the construction or material cost can be greatly reduced. Can be.

In addition, by making the second manhole 2 tapered, the influence of earth pressure is reduced, the force at the time of extraction is reduced, and easy extraction or extraction is made possible. In addition, since the second manhole 2 is of a split type, the weight at the time of removal can be reduced and the removal operation can be facilitated. Furthermore, since the opening 10 is formed in a slit shape having substantially the same width as the outer diameter of the conduits 3a and 3b, the opening area is minimized, and even when the manhole sinks by its own weight, the entry of mud is minimized. And work can be facilitated. Since the inlet 7 is formed near the bottom of the second manhole 2, the passage distance of the conduits 3a and 3b at the time of taking out can be minimized, and the taking out can be facilitated.

Next, a modified embodiment will be described.

FIG. 4 shows a modified example of the protection tube 11. In this example, the protection tube 11 is a tube 3a and an outer tube 1 covering the outside thereof.
4 and stored. The outer pipe 14 is fixed to the pipe 3a by an appropriate means, and forms a gap 15 between the outer pipe 14 and the pipe 3a. The protection tube 11 is slidably housed in the gap 15 (state (a)), and is pulled out and inserted into the outside of the conduit 3b (state (b)) at the time of use. Then, as described above, the seal member 12 is provided at the joint by taping.

According to the present embodiment, the outer pipe 14 blocks the earth pressure and reduces the external pressure to the protection pipe 11. Thereby, the protection tube 1
1 becomes smooth and the connection work becomes easy.

5 to 7 show modified examples of the second manhole, FIG. 5 is a perspective view showing the whole, FIG. 6 is a partially longitudinal front view, and FIG. 7 is a plan view.

As shown, the second manhole 15 is
Upper piece 15a, middle piece 15b and lower piece 1
5c are stacked to form a substantially rectangular box. These pieces 15a are designed not to be displaced in the horizontal direction due to, for example, the joint surfaces formed in an uneven shape.
It is a structure that only stacks, and it is easily divided by lifting it up.

The upper piece 15a is substantially flat and has a ring-shaped fitting portion 17 for fitting the lid 16 on the upper surface thereof. The fitting portion 17 is provided offset from the center of the manhole. And in the upper piece 15a,
An entrance 18 having the same diameter as the inside diameter of the fitting portion 17 is provided to allow a person to enter and exit. The middle piece 15b is formed in a frame shape, and has a shorter dimension in the height direction than the lower piece 15c. The lower piece 15c is formed in a bottomed cylindrical shape, and has an inlet 19 and an opening 20 similar to the above at the bottom side.

In the second manhole 15, only the lower piece 15c is formed in a tapered shape in which the bottom is slightly smaller. In other words, the taper angle of the lower piece 15c is a very small value. Middle and lower piece 15
b and 15c include ladder members 21 used when people enter and exit.
Is provided.

Particularly in the case of the present example, each piece 15a is made of reinforced concrete, that is, the frame 2 made of reinforcing steel is provided inside.
2 is buried to significantly improve the strength in the vertical direction in particular. This also sufficiently compensates for a decrease in strength due to the provision of the inlet 19 and the opening 20. By doing so, it is possible to sufficiently withstand the load caused by a large trailer of up to 20 tons in the safety standard of road transport vehicles.

As another modified example, it is conceivable that the protective tube is formed into a half-split shape, or the protective tube is connected to the pipeline by a connector or the like. Further, the protection tube may be replaced with another member for protecting the cable, or the manhole may be made of iron or the like.

In the same manner as described above, for example, a pull box, a hand hole, or the like used only for laying a cable can be made removable or dividable.
Further, the method of the present invention is applicable not only to cables but also to other wires.

[0050]

The present invention exhibits the following excellent effects.

(1) According to the first aspect of the present invention, the number of manholes as permanent structures remaining in the ground can be minimized, and management can be facilitated.

(2) According to the second aspect of the present invention, the work of connecting the protection tube becomes easy, and the work time can be shortened.

(3) According to the third aspect of the present invention, the outer pipe cuts off the earth pressure, smoothes the sliding of the protection pipe, and facilitates the connection work.

(4) According to the present invention, the manhole can be removed and reused.

(5) According to the fifth aspect of the present invention, the manhole can be easily extracted by reducing the influence of earth pressure.

(6) According to the sixth aspect of the present invention, the weight at the time of removing the manhole can be reduced and the removal operation can be facilitated.

(7) According to the seventh aspect of the present invention, the manhole can be removed by using the opening as a portion through which the protective tube passes, and the opening area is minimized, and the entry of mud is minimized. Work can be facilitated.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a cable laying method according to the present invention.

FIG. 2 is a partially cutaway perspective view showing a manhole according to the present invention.

FIG. 3 is a plan view showing a state in which conduits are connected by protective tubes.

FIG. 4 is a schematic vertical sectional front view showing a modified example of the protection tube.

FIG. 5 is a perspective view showing a modification of the manhole.

FIG. 6 is a partial vertical sectional front view of the manhole of FIG. 5;

FIG. 7 is a plan view of the manhole of FIG. 5;

FIG. 8 is a schematic plan view showing a conventional example.

[Description of Signs] 1 First manhole 2 Second manhole 2d Side wall 3, 3a, 3b Pipe line 4 Cable 6b Bottom wall 7 Inlet 10 Opening 11 Protection tube 14 Outer tube

Continuation of the front page (72) Inventor Yoshihiro Narita 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Hidaka Factory, Hitachi Cable Corporation (56) References JP-A-6-22423 (JP, A) JP-A-8-130812 (JP, A) JP-A-58-39888 (JP, A) JP-A-56-38906 (JP, A) JP-A-56-115110 (JP, A) JP-A-4-199104 (JP, A) JP-A-1-304228 (JP, A) JP-A-60-184126 (JP, A) JP-A-1-159519 (JP, U) JP-A-5-74121 (JP, U) 57-8852 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02G 1/06 H02G 9/10

Claims (7)

(57) [Claims] 1. A detachable second manhole is installed between first manholes for cable connection, and these manholes are connected by an underground conduit, and the cable is connected to the manhole through the conduit. After extending between the first manholes, the passing portion of the cable introduced from one conduit into the second manhole and led out to the other conduit,
A cable laying method, wherein the cable is laid in a protective tube connecting the two conduits for protection, and then the second manhole is removed to bury the protective tube in the ground. 2. The cable laying method according to claim 1, wherein the protection tube is previously slidably housed in the conduit. 3. The cable laying method according to claim 1, wherein the protective tube is slidably housed between the conduit and an outer tube covering the outside thereof in advance. 4. A side wall having a length corresponding to a depth of a pipe to be buried, and an inlet formed at a lower portion of the side wall to introduce the pipe and open downward. Manhole. 5. The manhole according to claim 4, wherein the side wall is formed in a tapered shape that gradually decreases toward the lower side. 6. The manhole according to claim 4, wherein the side wall is dividable into a plurality from the upper side to the lower side. 7. The apparatus according to claim 4, further comprising a bottom wall, wherein the bottom wall is formed with a slit-shaped opening which is continuous with the open end of the inlet and has substantially the same width as the outer diameter of the conduit. manhole.