JPH0684638B2 - Prefabricated underground structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a concrete assembly type that is suitably used when constructing a drainage ditch or the like for treating a common ditch or sewage and rainwater underground. It concerns underground structures.

[Prior Art] Recently, when constructing an underground structure of this type, a lower block with a top opening and an upper block with a bottom opening are manufactured in advance in a factory or the like, and these blocks are moved up and down at the construction site. It is popular to construct a concrete structure of a required scale by connecting a plurality of pieces in the lateral direction. With such a construction method, it is possible to reduce complicated work at the construction site and greatly shorten the construction period.

In such a structure, for example, connecting recesses that open to the inner surfaces of the lower block and the upper block are provided in the wall bodies of both blocks, and communication holes that open to the upper and lower connecting recesses and the upper surfaces of the upper blocks, respectively. Is provided. Then, a PC steel rod is inserted into this communication hole, its upper end and lower end are projected into the upper and lower connecting recesses, and nuts and the like are temporarily fixed to each end. After that, the lower end of the tension rod inserted into the communication hole from the upper surface side of the upper block and the upper end of the PC steel rod are connected to each other in the upper connecting concave portion via the connector. Then, while tension is applied to the PC steel rod with a hydraulic jack connected to the upper end of the tension rod, tighten the temporarily fixed nut at the upper end so that the lower block and the upper block are tightly joined. There is.

[Problems to be Solved by the Invention] However, with such a configuration, it is necessary to perform attachment / detachment work of the tension rod, the connector, etc. inside the block in accordance with the procedure described above, and such work is required. Since the position is often high, it is difficult to perform the tightening and joining work of the upper block and the lower block smoothly. Moreover, after the tightening and joining work, a special waterproof material such as grout is injected into the communication hole,
It is necessary to prevent corrosion of PC steel rods.

In order to eliminate such inconvenience, a connecting concave portion is provided only on the lower block side, and a communicating hole that opens to the upper surface of the connecting concave portion and the upper block is provided in the wall bodies of the lower block and the upper block. Further, a PC steel rod inserted into the communication hole is given a tension force so that the upper block and the lower block are tightened and joined.

According to this structure, the above-mentioned work can be reduced, and the upper block and the lower block can be efficiently tightened and joined, but the work of injecting the waterproof material into the communication hole is indispensable.

An object of the present invention is to provide a prefabricated underground structure that can eliminate the above-mentioned problems at once.

[Means for Solving the Problems] The present invention adopts the following configuration in order to achieve such an object.

That is, the prefabricated underground structure according to the present invention is a prefabricated underground structure in which a concrete upper block having a lower opening is placed on a lower block made of concrete having an upper opening, and a load of the lower block. In addition to providing an opening on the inner surface of the intermediate portion where the moment due to earth pressure is small and providing a connecting concave portion on the wall body, the lower end opens inside the connecting concave portion and the upper end in the wall body of the lower block and the upper block. Is provided with a communication hole opening on the upper surface of the upper block, and the lower block and the upper block are tightly joined by an unbonded PC steel rod inserted into the communication hole.

Unbonded PC steel rods are usually used by being embedded in concrete during the production of concrete blocks, and have undergone special treatment to cut the adhesion of concrete and prevent corrosion. .

[Operation] According to such a configuration, the strength of the wall body is substantially the same as that of the wall body having no recess. In other words, in an underground structure buried in the soil, a bending moment is generated in each wall body due to the pressure (earth pressure) from the surrounding soil, and the bending moment is underground in the central part of each wall body. It becomes the largest towards the inside of the construct, and acts at each corner in the opposite direction to the central part. Bending moments in different directions are balanced and minimized at a distance of about 1/4 from the end of the wall. By selecting the position where the bending moment is the smallest and providing the concave portion, the upper block and the lower block can be tightly coupled to each other without lowering the strength against the bending moment.

Then, when assembling, the lower block and the upper block can be sequentially joined as follows.

First, insert an unbonded PC steel rod into the communication hole from the upper side of the upper block placed on the lower block, project the lower end into the connecting recess, and attach nuts and the like to both upper and lower ends. deep. Next, the jack is connected to the upper end of the unbonded PC steel rod via a connector or a tension rod. Then, while tightening the nuts temporarily fixed to the upper end with a predetermined tension applied to the unbonded PC steel rod with a jack, and then removing the jack, etc., the wall of the lower block and the upper block is removed. It is possible to join the upper and lower blocks one after another with high pre-stress introduced. Moreover, since the unbonded PC steel bar has been subjected in advance to a treatment for cutting the adhesion of concrete and a high anticorrosion treatment, it is possible to eliminate the special waterproof material such as grout to be injected into the communication hole. Become.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

In this prefabricated underground structure, an upper block 2 is placed on a lower block 1, and the lower block 1 and the upper block 2 are tightly joined to each other by an unbonded PC steel rod 3. It is possible to simultaneously construct two adjacent culverts by connecting a plurality of them in the lateral direction.

As shown in FIG. 1, the lower block 1 is made of top-cast precast concrete, and has side walls 5 standing on both sides of the bottom slab 4 and walls erected at the center of the bottom slab 4. It is provided with a body inner wall 6 and a connecting box 7 as a connecting recess provided on each of the side wall 5 and the inner wall 6. The lower blocks 1 adjacent to each other have anchor plates in the connecting box 8 as schematically shown in FIG. 8 with a sealing material (polyurethane resin or the like) interposed between the end surfaces 1a and 1b. A plurality of vertically-tightened PC steel rods 9 whose ends are fixed via nuts and nuts (not shown) are used to make a plurality of transversely tight-fitting joints. The connecting box 7 is
It is an iron-made box-like body whose one end face is opened to the inner surface 1c of the lower block 1, and is located at a position away from the upper joint surface 1d of the lower block 1, that is, the prefabricated underground structure is assembled and buried in the soil. In this case, it is arranged at an intermediate position where the bending moment due to the load earth pressure applied to the side wall 5 becomes small.

The upper block 2 is made of precast concrete having an underside opening, and is symmetrical with the lower block 1. That is, the top plate 10 includes a side wall 11 that is a wall body that hangs from both sides and a middle wall 12 that is a wall body that hangs from the central portion of the top plate 10. Adjacent upper blocks 2 have end faces
With the sealing material (polyurethane resin, etc.) interposed between the 2a and 2b, as shown in FIG. 8, the end is fixed in the connecting box 13 via the anchor plate and the nut (not shown). A plurality of vertically tightened PC steel rods 14 are adapted to be tightly joined laterally.

Further, the side wall 5 and the middle wall 6 of the lower block 1 and the side wall 11 and the middle wall 12 of the upper block 2 are provided with communication holes 15 as shown in FIGS. Each communication hole 15
Has a lower end opening into the connecting box 7 and an upper end opening into the bottom of a recess 2d formed in the upper surface 2c of the upper block 2. Spiral muscles 16 are embedded around the opening of the communication hole 15 as shown in FIGS. 6 and 7.

As shown in FIG. 6 and FIG. 7, the rubber block 17 is interposed between the upper joint surface 1d of the lower block 1 and the lower joint surface 2e of the upper block 2 so that the upper block 1 is covered. The upper block 2 is placed on the upper part, and both blocks 1 and 2 are tightly joined by the unbonded PC steel rod 3 inserted into the connecting hole 15. The unbonded PC steel rod 3 has, for example, a surface of the PC steel rod body coated with a rust preventive material and a resin (such as polypropylene), and has a function of preventing the adhesion of concrete and preventing the occurrence of rust. The lower end 3a and the upper end 3b are provided with threaded portions. Anchor plates 18 and 19 and nuts 20 and 21 are attached to the lower end portion 3a and the upper end portion 3b, respectively. Tighten the nut 21 of the upper end portion 3b while applying a constant tension to the unbonded PC steel rod 3. The lower block 1 and the upper block 2 are tightly joined. The concave portion of the upper block 2
2d and the connecting box 7 are filled with resin mortar 25.

When constructing this prefabricated underground structure, the following construction procedures are followed. The upper block 2 is placed on the lower block 1, and the unbonded PC steel rod 3 is inserted into the communication hole 15 from the upper surface 2c side of the upper block 2. Bottom edge 3a
Is an anchor plate that projects into the connecting box 7.
18 and the nut 20 are attached, and the upper end 3b is projected into the recess 2d of the upper block 2 so that the anchor plate 19 and the nut 21
Temporarily stop. A tension rod 23 is connected to the upper end portion 3b via a connector 22, and the tension jack 23 is connected to the hydraulic jack 24.
Are connected. Then, the tension rod 23 is pulled upward by the hydraulic jack 24 with a predetermined force, and the nut 20 is tightened with a wrench or the like in that state, and then the connector 22 and the tension rod 23 are removed. Tension is applied to the unbonded PC steel rods 3 arranged at each position in the same manner, and the lower block 1 and the lower block 2 are tightly joined.

Therefore, according to the above configuration, the upper block 2
Since the connector 22 and the tension rod 23 can be attached / detached on the upper surface 2c side of the above and the man-hours for attaching / detaching them can be reduced, the lower block 1 and the upper block 2 can be efficiently tightened and joined. it can.

Moreover, since the unbonded PC steel rod 3 has been previously provided with not only a function of cutting off the adhesion of concrete but also a function of preventing corrosion, a special waterproof material such as grout that has been conventionally injected into the communication hole 15. Can be eliminated, and the number of man-hours at the construction site can be further reduced. Moreover,
Since the connecting box 7 is formed substantially at the center of the side wall 5 in the height direction, it is less affected by the bending moment due to earth pressure, and the strength of the side wall 5 can be prevented from decreasing.

The embodiment of the present invention has been described above.
It is also applicable when introducing prestress to the lower half of the wall of the lower block. Another embodiment of the present invention will be described below with reference to FIGS. 9 and 10. In addition, the same parts as those in the above embodiment are denoted by the same reference numerals,
The description is omitted.

In FIG. 9, the unbonded PC steel rod 103 is embedded in the lower half portion of the side wall 5 of the lower block 1 together with the anchor plate 118 and the nut 120 attached to the lower end portion 103a of the lower block 1 at the factory, and the upper end portion 103b is formed. It is made to project in the box 7 for connection which is a concave part for connection. And this unbonded PC
After connecting the upper end 103b of the steel rod 103 and the lower end 3a of the upper unbonded PC steel rod 3 by the coupler 26, the unbonded PC
The nuts 20 and 21 are tightened and the lower block 1 and the upper block 2 are tightly joined to each other in a state where the steel rods 3 and 103 are given the same tension as described above.

In FIG. 10, in the lower half of the side wall 5 of the lower block 1,
A communication hole 115 is provided, the lower end of which opens into a recess 4b formed in the lower surface 4a of the bottom plate 4 and the upper end of which opens into the connecting box 7 which is a connecting recess. Then, before installing the lower block 2 at a construction site or the like, the unbonded PC steel rod 103 is inserted into the communication hole 115.
, And the anchor plate 118 and the nut 120 are attached to the lower end portion 103b thereof. Next, the coupler 26
After connecting both unbonded PC steel rods 3, 103 by
With the tension applied to the unbonded PC steel rods 3 and 103 in the same manner as described above, the nuts 20 and 21 are tightened to tightly join the blocks 1 and 2.

EFFECTS OF THE INVENTION Since the present invention has the above-mentioned configuration, it is possible to efficiently and securely fasten the upper block and the lower block to each other with high pre-stress introduced into the entire wall of the upper block and the lower block. It is possible to suppress the decrease in the strength of the wall of
Moreover, the waterproof material such as grout can be eliminated.
As a result, the work man-hours at the construction site can be reduced, and the prefabricated underground structure can be efficiently constructed in a short period of time.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a front view, FIG. 2 is a front sectional view of a side wall, FIG. 3 is a side sectional view of a side wall, and FIG. FIG. 5 is a side sectional view of the inner wall, FIG. 6 is a detailed view of an essential part of the side wall, FIG. 7 is a detailed view of an essential part of the inner wall, and FIG. 8 is a right side view. . 9th
The drawing is a front sectional view corresponding to FIG. 2 showing another embodiment of the present invention. FIG. 10 is a front sectional view corresponding to FIG. 2 showing still another embodiment of the present invention. 1 …… Lower block, 1a, 1b …… End face 1c …… Inner surface, 1d …… Upper surface joining surface 2 …… Upper block, 2a, 2d …… End surface 2c …… Upper surface, 2d …… Recess 2e …… Lower end joining surface 3, 103 …… Unbonded PC steel rods 3a, 103a …… Lower end 3b, 103b …… Upper end 4 …… Bottom plate, 4a …… Lower surface 4b …… Recessed 5, 11, …… Wall body (side wall) 6, 12 ...... Wall (middle wall) 7 ...... Recessed recess (connecting box) 8, 13 ...... Connecting box 9, 14 ...... Vertical-tightened PC steel rod 10 ...... Top plate, 15, 115 ...... Communication Hole 16 …… Spiral streak, 17 …… Sealing material 18, 19, 118 …… Anchor plate 20, 21, 120 …… Nut 22 …… Connector, 23 …… Tension rod 24 …… Hydraulic jack, 25 …… Resin Mortar 26 …… Cupra

Claims (1)

[Claims] 1. A prefabricated underground structure in which an upper concrete block having a lower opening is mounted on a lower concrete block having an upper opening, and a moment due to earth pressure under load of the lower block is reduced. An opening is formed on the inner surface of the intermediate portion, and a connecting recess is provided in the wall body, and a lower end is opened in the connecting recess and a top end is opened on an upper surface of the upper block in the wall bodies of the lower block and the upper block. An assembly type underground structure, characterized in that the lower block and the upper block are tightly joined by an unbonded PC steel rod inserted into the communication hole.