JPH057357Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a block used in a propulsion method when constructing underground conduits such as culverts, tunnels, and other underground conduits such as electric cables.

[Prior Art] Conventionally, as a block for use in this type of propulsion method, a rectangular cylindrical block comprising a bottom plate, both side walls, and a top plate is known.

When constructing a culvert or the like in the ground using blocks for this type of propulsion method, first attach a cutting edge to the front end of the first block, and use it to excavate and push back the earth and sand in front of the block. A jack propels the cutting edge and the block.
Then, when the blocks have been propelled a certain distance, the jacks are moved back to join the next block to the rear end of the previous block, and the push jack is operated again to propel these blocks. Thereafter, a plurality of blocks are successively connected and propelled in the same manner.

[Problems to be Solved by the Invention] However, when implementing such a propulsion method, a compressive force in the axial direction acts on each block during propulsion. If an unbalanced load is applied due to changes in the ground, a particularly large compressive force will be applied to any part of the structure. Therefore, it is necessary to make the bottom plate, side walls, and top plate of each block thick enough to withstand the compressive force, but conventional blocks of this type are generally made of simply reinforced concrete.
They tend to lack strength, and their thickness cannot help but increase. Therefore, there is a problem in that the cross-sectional area of the block becomes relatively large, and large-scale jacking equipment that can exert a strong propulsive force is required.

The present invention aims to solve the above problems.

[Means for Solving the Problems] In order to achieve the above objectives, the present invention employs the following configuration.

That is, the block for the propulsion method according to the present invention is a square cylindrical concrete block comprising a bottom slab, both side walls, and a top slab, and inside each of the bottom slab, both side walls, and the top slab, Multiple unbonded PC steel bars are buried in parallel at equal intervals perpendicular to the propulsion direction, and each unbonded
The threaded portions at both ends of the PC steel bars are passed through anchor plates embedded and fixed within the concrete structure, and each unbonded PC steel bar is inserted into the threaded portions at both ends with tension applied between the corresponding anchor plates. It is characterized by being firmly established.

[Function] If the block has such a configuration, prestress will be applied to each of the bottom plate, both side walls, and the top plate due to the tension applied to the unbonded PC steel bars embedded in the bottom plate, both side walls, and the top plate. It will be introduced. Moreover, the unbonded PC steel rod is
Since a plurality of rods are buried perpendicularly to the propulsion direction and parallel to each other at equal intervals in the bottom plate, both side walls, and the top plate, prestress can be applied evenly over substantially the entire surface of the bottom plate, both side walls, and the top plate. It becomes possible to leave it there. As a result, the concrete block as a whole exhibits a large resistance against compressive force in the direction of propulsion. Therefore, it is possible to make the bottom plate, both side walls and the top plate evenly thinner, and the cross-sectional area of each block can be reduced without difficulty.

It should be noted that this type of block is known to have prestress applied to the top plate, etc., but conventional blocks are reinforced in the thickness direction in the areas necessary to resist earth pressure and overburden loads. However, it has a completely different function from that of the present invention.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

1 to 4 show a block 1 for the propulsion method according to the present invention. This block 1 has a square cylindrical shape and includes a bottom plate 2, both side walls 3, and a top plate 4. And its bottom plate 2, both side walls 3
and unbonded PC steel rod 5 on each of the top plate 4
is buried. The unbonded PC steel bar 5 is a steel bar with asphalt emulsion coated on the outer circumferential surface.
A circular concave portion 6 in which the fixed end 5a is located within the wall thickness of the block 1, and the tension end 5c having a threaded portion 5b on the outer periphery is opened on the outer surface 1a of the block 1.
It protrudes inward and is embedded in the bottom plate 2, both side walls 3, and top plate 4. And the tension end 5c
After installing the nut 9 through the anchor plate 7 and washer 8, the tensile end 5 of this PC steel bar 5 is
c is towed using a hydraulic jack (not shown),
In this state, the nut 9 is tightened to apply the required tension to the PC steel bar 5. After that, the hydraulic jack is removed and mortar 1 is placed in the recessed part 6.
Fill with 1. In addition, when manufacturing the block 1 by pouring concrete into the formwork, the above-mentioned
Since it is necessary to hold the fixed end 5a of the PC steel bar 5 in the formwork via a holder, a hole 12 remains in the block 1 when the holder is removed after demolding.
Therefore, this hole 12 is also filled with mortar 13.

In the case of this embodiment, for example, four unbonded PC steel bars 5 are buried in each of the bottom plate 2, both side walls 3, and the top plate 4 in parallel at equal intervals perpendicular to the propulsion direction n. ing.

Next, a propulsion method for constructing a culvert in the ground using this propulsion method block 1 will be explained with reference to FIG.

First, a starting shaft 15 surrounded by sheet piles 14 is formed, a bearing wall 16 is formed on one side wall of the shaft 15, and a starting shaft entrance 17 is provided on the other wall opposite to the bearing wall 16. Then, a driving platform 18 is laid on the bottom of the shaft 15, and a push angle 19, a jack 21, a strut 22, and a
A pressure ring 23 and cushion material 24 are provided.
Then, the block 1 having the cutting edge 25 attached to its front end is placed at the starting tunnel mouth 17, and the block 1 is propelled into the ground by the pushing force of the jack 21.
Then, when this block 1 has been advanced a certain distance, the jack 21 is retracted, and the tip of the next block 1, which has been lowered into the shaft 15 by a crane 27, is fitted into the inner periphery of the collar 26 attached to the rear end of the previous block 1, and the jack 21 is operated again to advance these blocks 1. This operation is then repeated the required number of times.

As described above, the block 1 can be propelled, but this block 1 has unbonded PC steel rods 5 embedded in the bottom plate 2, both side walls 3 and top plate 4, respectively, and running perpendicular to the propulsion direction. Since the prestress in the direction of propulsion is applied to the entire surface, the bottom plate 2, both side walls 3, and top plate 4 exhibit high resistance against compressive force in the propulsion direction. Therefore, even if the bottom plate 2, both side walls 3, and top plate 4 are made relatively thin, they can withstand the pressing force during propulsion, especially the strong compressive force when an uneven load is applied. Therefore, when the bottom plate 2, both side walls 3 and top plate 4 are made thin as described above, the cross-sectional area of the block 1 can be made reasonably small. Therefore, it becomes possible to reduce the propulsive force required to propel the block 1.

It should be noted that the number of unbonded PC steel rods to be buried is of course not limited to that of the illustrated embodiment, and can be modified in various ways without departing from the spirit of the present invention.

[Effects of the invention] Since the present invention has the above-mentioned configuration, the bottom plate, both side walls, and the top plate can be equally distributed by improving the strength that can resist the splitting stress generated in the direction perpendicular to the propulsion direction. The walls can be made thinner, so the cross-sectional area can be easily reduced without causing a decrease in strength, and the required propulsion force can be reduced, making it possible to downsize jacking equipment and increase the efficiency of construction. It is possible to provide a block for the propulsion method that can be used.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a front view, Fig. 2 is a side view, Fig. 3 is a plan view, Fig. 4 is an enlarged sectional view showing the main parts, and Fig. 5 is a propulsion method. It is an explanatory view for explaining an example. 1...Block, 1a...Outer surface, 2...Bottom plate,
3...Side wall, 4...Top plate, 5...Unbonded PC
Steel rod, 5a...fixed end, 5b...screw part, 5c...
... tension end, 6 ... recess, 7 ... anchor plate, 8 ... washer, 9 ... nut, 11 ... mortar, 12 ... hole, 13 ... mortar, 14 ...
... Sheet pile, 15 ... Starting shaft, 16 ... Bearing wall, 17 ... Starting shaft, 18 ... Propulsion platform, 19
... Push angle, 21 ... Jacket, 22 ... Strut, 23 ... Push ring, 24 ... Cushion material, 25
...Blade mouth, 26...Color, 27...Crane,
n... Propulsion direction.

Claims (1)

[Scope of utility model registration request] It is a square cylindrical concrete block comprising a bottom plate, both side walls, and a top plate, and a plurality of unbonded PC steel rods are installed inside each of the bottom plate, both side walls, and the top plate in the direction of propulsion. Bury at right angles and in parallel at equal intervals, and unbond each
The threaded portions at both ends of the PC steel bars are passed through anchor plates embedded and fixed within the concrete structure, and each unbonded PC steel bar is inserted into the threaded portions at both ends with tension applied between the corresponding anchor plates. A block for the propulsion method, which is characterized by being firmly fixed.