JP5350200B2 - Underground box and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underground buried box which can be further reduced in weight, while securing the necessary strength, and can be easily connected to an underground buried pipe by expanding an area of a knockout portion. <P>SOLUTION: The underground buried box comprises a square or rectangular bottom plate portion 3a, a window-frame shaped side wall portion 3b erected from the respective sides of the bottom plate portion 3a, and a lightweight panel 4 installed on the side wall portion 3b so as to cover an opening 3c of the side wall portion 3b. The lightweight panel 4 comprises a panel body consisting of reinforced fiber and hardened foam cement having a large number of foams dispersed approximately uniformly in the cement, and a surface reinforcing layer made of FRP having reinforced fiber embedded in a resin layer and laminated on the surface of the panel body to be integrated with the panel body. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an underground box such as a handhole or a manhole used when an electric cable, a communication cable, or the like is wired underground, and a manufacturing method thereof.

  Underground boxes such as manholes and handholes are usually made of reinforced concrete, and are manufactured at the factory, then transported to the site, installed in the ground, and embedded in the ground to store electrical and communication cables. The tubes are connected to each other (see, for example, Patent Document 1).

  This type of underground burial box is available in various sizes depending on the application, but large sized boxes not only require large heavy machinery for carrying out and carrying in, but are also inferior on-site workability. Thus, as an underground box that takes transportability and workability into account, an assembly-type one is known in which parts divided into an upper part and a lower part are assembled and integrated on site.

  In addition to the above, assembling-type ones are also known in which a top panel, a bottom panel, and four side panels are assembled in a box shape. In the panel assembly type underground burial box, for at least four side panels, a composite panel in which a lightweight cement board is attached to a frame-like frame is used, and the lightweight cement board is reinforced by reinforcing fibers, Weight reduction is achieved (for example, refer patent document 2).

  In addition, a thin wall part for connecting underground pipes, a so-called piping knockout part, is provided at the lower part of the side wall of such an underground box, which is necessary for the knockout part by drilling with a drill. A large number of openings are provided, the connection side end of the underground pipe is inserted, and the gap between the opening and the underground pipe is sealed with mortar or the like.

JP 2002-238118 A JP 2008-291453 A

  However, in the underground burial box described in Patent Document 1 described above, there is a desire to increase the area of the knockout portion in order to connect more underground pipes, but when the area of the knockout portion is expanded, There is a problem that it is not possible to secure a strength that can withstand pressure and water pressure.

  In addition, when connecting the connection side end of a large number of underground pipes to the knockout part, the connection work must be performed within the range of the knockout part where the area is limited. is there.

  In addition, since the underground box disclosed in Patent Document 2 has a large number of parts, it can be reduced in weight, but takes longer to install than an integrated underground box.

  The present invention has been made in consideration of the problems in the conventional underground burial box as described above, and can be easily installed with light weight, and the area of the knockout portion can be expanded to simplify the underground burial pipe. An underground burial box that can be connected to the ground and a method for manufacturing the same are provided.

The underground burial box of the present invention has a rectangular or rectangular bottom plate,
A window frame-shaped side wall portion standing from each side of the bottom plate portion;
A lightweight panel constructed on the side wall so as to cover the opening of the side wall,
The lightweight panel is composed of a panel body made of a hardened foam cement in which reinforcing fibers and a large number of bubbles are dispersed almost uniformly in the cement, and FRP in which reinforcing fibers are embedded in a resin layer, and is laminated on the surface of the panel body. The gist is that it is composed of a surface reinforcing layer integrated with the panel body.

  In the underground burial box of the present invention, the foamed cement foam is solidified by filling a foamed cream-like cement obtained by kneading cement, water, reinforcing fibers and a foaming agent into a mold. It is preferable that the specific gravity is in the range of 0.5 to 1.5.

  Moreover, if a waterproof layer is further laminated on the outer surface of the surface reinforcing layer, it is possible to reliably prevent water from penetrating into the lightweight panel.

  If a reinforcing bar is provided on the outer peripheral part of the lightweight panel and a part of the reinforcing bar protrudes from the outer peripheral part of the lightweight panel and is embedded in the side wall part, the lightweight panel and the side wall part can be integrated more firmly. it can.

  Moreover, if the said baseplate part and the said side wall part are comprised with lightweight concrete, an underground burial box can be further reduced in weight.

  Moreover, it is preferable to reinforce the side wall portion by embedding a reinforcing steel material at the edge of the opening in the side wall portion.

The underground buried box manufacturing method of the present invention forms a panel made of a hardened foam cement in which reinforcing fibers and a large number of air bubbles are dispersed almost uniformly in cement,
FRP in which reinforcing fibers are embedded in a resin layer is laminated on the surface of the panel to form a reinforcing layer on the surface of the panel,
A lightweight panel in which the panel and the surface reinforcing layer are integrated is fixed to each inner surface of the side wall forming mold divided into four parts,
In the state where the lightweight panel and the inner frame are in close contact, the side wall forming mold is assembled into a square tube around the inner frame,
By filling concrete or lightweight concrete in the gap between the inner frame, the bottom surface forming frame, and the side wall forming frame, the side wall portion of the underground box is molded into a window frame shape and at the same time the opening of the side wall portion The gist is to fit the lightweight panel into the part and integrate it with the side wall.

  In the underground box manufacturing method of the present invention, it is preferable that reinforcing bars are provided on the outer peripheral portion of the lightweight panel, and a part thereof is protruded from the outer peripheral portion and fixed to each inner surface of the side wall forming mold. .

  The lightweight concrete in the present invention has a density obtained by mixing lightweight aggregates, or by adding a large amount of bubbles, and by mixing lightweight aggregates and bubbles with a predetermined composition in the concrete. It means the concrete which lowered.

  According to the present invention, it is lightweight and can be easily installed, and has an advantage that the underground pipe can be simply connected by expanding the area of the knockout portion.

It is a longitudinal cross-sectional view which shows the whole structure of the underground burial box which concerns on this invention. It is an expanded longitudinal cross-sectional view of the lightweight panel attached to the lower box component shown in FIG. It is a top view which shows the state before attachment of the lightweight panel shown in FIG. It is the perspective view which showed the formwork for lower box component shaping | molding in which the lightweight panel was set. It is a perspective view which shows the external appearance of the manufactured lower box component. It is a longitudinal cross-sectional view of the side wall of the lower box part. It is a cross-sectional view of the side wall of the lower box part.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

1. Overall structure of underground burial box In Fig. 1, the underground burial box 1 such as a handhole or manhole has an upper box part 2 having a circular opening 2a on the upper surface and an open lower part, and an upper part and a knockout. A lower box part 3 having an open bottom part 3a, a lightweight panel 4 attached to a knockout part of the lower box part 3, and an upper peripheral edge of the circular opening 2a in communication with the circular opening 2a. An annular lid frame 5 is provided, and a circular lid 6 is attached to the lid frame 5 so as to be freely opened and closed. The lid 6 is shown for explaining the usage pattern of the underground burial box 1.

  In the present embodiment, a description will be given taking an underground box made of a cube as an example. However, the shape of the underground box 1 is not limited to a cube, and may be a rectangular parallelepiped or other shapes.

  In the connection joint S between the upper box part 2 and the lower box part 3, a concave groove (not shown) is formed in the connection surface of the lower box part 3, and an epoxy resin is formed in the connection surface and the concave groove. An adhesive is applied so that the upper box part 2 and the lower box part 3 are connected and integrated.

  Also, the connection between the lid frame 5 and the upper peripheral edge of the circular opening 2a is made by applying an epoxy resin adhesive and integrating them.

  In the present embodiment, an underground box that connects and integrates the upper box part 2 and the lower box part 3 is taken as an example, and since the knockout portion N is provided at the lower part of the side wall, the configuration of the lower box part 3 is described below. However, as long as it is an underground burial box that requires the knock-out portion N, it is not limited to a split type, and may be configured integrally.

  The lower box part 3 has a structure in which a rectangular or rectangular bottom plate portion 3a and a window frame-shaped side wall portion 3b erected from each outer periphery of the bottom plate portion 3a are integrated, and formed on the side wall portion 3b. The lightweight panel 4 is installed on the side wall 3b so as to cover the opening.

  The present invention is intended to reduce the weight of the underground box by configuring the knockout portion N with a lightweight panel. The concrete constituting the upper box part 2 and the lower box part 3 is (a) normal Concrete, (b) Lightweight concrete in which light aggregate is mixed with concrete and lower in density than normal concrete, (c) Lightweight concrete containing a large amount of air bubbles in concrete, (d) Lightweight aggregate and air bubbles It is possible to use lightweight concrete mixed with concrete in a predetermined composition. It should be noted that (a) normal concrete and (b) to (d) lightweight concrete are embedded with reinforcing bars for reinforcing the strength.

  However, if the upper box part 2 and the lower box part 3 are made of lightweight concrete, only the knockout portion N is lightened by a lightweight panel. (A) Compared to the underground box made of ordinary concrete, the underground box is lighter. Can be achieved. Therefore, as a material for the upper box part 2 and the lower box part 3, it is preferable to select any one of the above-mentioned (b) to (d) lightweight concrete.

2. Structure of lightweight panel The lightweight panel 4 can be comprised from a foam cement hardened | cured material or a foamed cement hardened | cured material.

2.1 Lightweight panel made of hardened foam cement
2.1.1 Panel body In FIG. 2, the panel body 4a of the lightweight panel 4 made of foamed cement cement is made of a material in which reinforcing fibers 4b and a large number of bubbles (not shown) are dispersed substantially uniformly in the cement. It can be obtained by filling and solidifying cream-like foaming cement obtained by kneading cement, water, reinforcing fiber 4b and foaming agent into a mold, and curing for a predetermined period after demolding. it can.

  Examples of the reinforcing fibers 4b include polyvinyl alcohol fibers (vinylon), polyolefin fibers such as polypropylene fibers and polyethylene fibers, aramid fibers, carbon fibers, steel fibers, and glass fibers.

  Of these reinforcing fibers 4b, vinylon fibers are particularly preferred because of their high durability and excellent affinity with cement.

  The fiber length of the reinforcing fiber 4b is preferably in the range of 4 to 35 mm. When the fiber length is less than 4 mm, the reinforcing effect tends to be insufficient, and when the fiber length exceeds 35 mm, the dispersibility decreases.

  Furthermore, the fiber thickness of the reinforcing fiber 4b can be 10 μm to 100 μm.

  The compounding amount of the reinforcing fiber 4b is preferably 0.5 to 5 parts by weight, more preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of cement. When the blending amount of the reinforcing fibers 4b is less than 0.5 parts by weight, the reinforcing effect becomes low, and when the blending amount of the reinforcing fibers 4b exceeds 5 parts by weight, the dispersibility in the foamed cement is deteriorated.

  As the foaming agent, a conventionally known foaming agent can be used, and the addition amount may be adjusted according to the specific gravity of the intended lightweight panel. In this embodiment, the specific gravity of the panel body 4a is 0. It is prepared to be in the range of 5 to 1.5.

2.1.2 Surface Reinforcement Layer The surface reinforcement layer 4c comprises FRP by resin layers 4d and 4d provided on the front and back surfaces of the panel body 4a and reinforcement fibers 4e embedded in these resin layers 4d and 4d. A waterproof layer 4f is formed on the outermost surface of the resin layers 4d and 4d.

  As the resin layers 4d and 4d, a synthetic resin for FRP or a foamable synthetic resin can be selected.

  Examples of the synthetic resin for FRP include polystyrene resin, polyethylene resin, hard polyurethane resin, hard vinyl chloride resin, urea resin, phenol resin, acrylic resin, and cellulose acetate resin.

  Examples of the foamable synthetic resin include polystyrene foam, polyethylene foam, rigid polyurethane foam, rigid vinyl chloride foam, urea foam, phenol foam, acrylic foam, and cellulose acetate foam.

  Moreover, it is preferable to adjust the expansion ratio of the expandable synthetic resin to about 2 to 10 times. Since the density of the FRP layer increases as the expansion ratio decreases, the strength of the lightweight panel 4 increases, but on the other hand, the panel weight increases. On the contrary, as the expansion ratio increases, the density of the FRP layer decreases, so that the panel weight can be reduced, but the strength of the lightweight panel 4 decreases.

  Therefore, when the expansion ratio is adjusted within a range of about 2 to 10 times, it is possible to suppress an increase in the weight of the lightweight panel 4 while securing the required strength of the lightweight panel 4 with the surface reinforcing layer.

  The reinforcing fiber 4e for FRP is the same as the reinforcing fiber 4b embedded in the panel body 4a, such as polyvinyl alcohol fiber (vinylon), polyolefin fiber such as polypropylene fiber or polyethylene fiber, aramid fiber, carbon fiber, steel fiber, glass fiber, etc. However, in order to form a stable FRP, it is preferably embedded in the resin layers 4d and 4d in the form of a woven fabric or a non-woven fabric.

In the form of the nonwoven fabric, a glass mat made of glass fibers having a basis weight of 50 to 1000 g / m ² , preferably 200 to 300 g / m ² is easily available as a general-purpose product, and has a strength of FRP constituting the surface reinforcing layer 4c. As a result, the strength of the lightweight panel 4 can be significantly increased.

  The reinforcing fibers 4e may be embedded in the surface of the surface reinforcing layer 4c, or may be embedded in an intermediate portion in the thickness direction of the surface reinforcing layer 4c.

  Further, when used in the form of woven fabric or non-woven fabric, FRP synthetic resin or foamable synthetic resin can be passed through the fiber gaps of the reinforcing fibers 4e, and the surface reinforcing layer 4c is firmly attached to the surface of the panel body 4a. Can be integrated.

  In the present embodiment, the thickness of the surface reinforcing layer 4c formed using the FRP synthetic resin or the foamable resin is set in the range of 0.5 to 2 mm.

  The waterproof layer 4f formed on the outermost surface of the resin layers 4c, 4c is a single layer or a plurality of sheets made of polyolefin resin such as polyethylene or polypropylene, polyester resin such as polyethylene terephthalate, ABS, MMA or the like. It can form by sticking as a layer.

  The waterproof layer 4f can be formed not only by attaching the resin sheet but also by applying a waterproof resin.

2.1.3 Manufacturing method of lightweight panel When manufacturing lightweight panel 4 using foamable synthetic resin, first, formwork (top plate, bottom plate, side plate) that can be assembled into a box shape corresponding to the size of lightweight panel 4 ) And assemble the mold into a container shape using the bottom plate and the side plate.

  A foamable synthetic resin is applied to the bottom surface of the mold to a predetermined thickness, and mat-like reinforcing fibers 4e having the same size as the panel body 4a are embedded in the synthetic resin.

  Next, the panel body 4a produced in advance is lifted by a predetermined gap from the bottom surface of the mold and set and fixed in the container-shaped mold. The gap between the lower surface of the panel body 4a and the bottom surface of the formwork is the formation thickness of the surface reinforcing layer 4c.

  Next, FRP synthetic resin or foamable synthetic resin is applied to the upper surface of the panel body 4a to a predetermined thickness, and mat-like reinforcing fibers 4e having the same size as the panel body 4a are embedded in the synthetic resin. .

  Next, the mold for attaching the top plate on the side plate is sealed. At this time, a predetermined gap is provided between the upper surface of the panel body 4a and the lower surface of the top plate. The gap between the upper surface of the panel main body 4a and the lower surface of the top plate also becomes the formation thickness of the surface reinforcing layer 4c. It is assumed that the mold is provided with an air vent for releasing air in the mold when foaming synthetic resin is foamed.

  The foaming synthetic resin has a reaction start time adjusted so that the reaction starts after the mold is closed. When foaming of the foaming synthetic resin starts, foaming pressure acts in the closed gap. Thus, the FRP is formed in a state where the density of the foamable synthetic resin in which the reinforcing fibers 4e are embedded is increased, and the FRP is in close contact with the upper and lower surfaces of the panel body 4a, and is integrated with the panel body 4a.

  Thus, the lightweight panel 4 in which the surface reinforcing layer 4c is integrally formed on the upper surface and the lower surface of the panel body 4a is manufactured.

  After demolding, the lightweight panel 4 with the surface reinforcing layer 4c is taken out and cured for a predetermined period. After curing, a waterproof layer 4f is formed on the surface of the surface reinforcing layer 4c, and the lightweight panel 4 with waterproofness is completed. To do. The thickness of the manufactured lightweight panel 4 is 25 mm. Incidentally, the thickness of the thin knockout part of the conventional underground buried box made of ordinary concrete varies depending on the size of the underground buried box, but an effective dimension of 500 mm × 500 mm handhole to effective In a hand hole with dimensions of 1500 mm × 1500 mm, it is 20 to 70 mm.

  The lightweight panel 4 manufactured in this way is excellent in drilling workability, and cracks are not generated from the holed portion due to the embedded reinforcing fibers 4e. Thereby, the drilling operation when connecting the underground buried pipe at the site can be easily performed, and the drilling operation time can be greatly shortened.

2.1.4 Seal structure The gap formed between the opening edge of the knockout portion N (see FIG. 1) on the side surface of the lower box part 3 and the lightweight panel 4 is provided with a sealing material for filling and sealing the gap. It is designed to be filled. Note that a silicon-based sealing material is preferably used as the sealing material.

2.2 Lightweight panel made of hardened foam cement When the hardened foam cement is used as the panel body of a lightweight panel, the manufacturing method of the panel body is as follows.

  A foamable aluminum powder, a stabilizer and water are added to silica stone, cement, quicklime, etc., and these are mixed to form a slurry, which is then poured into a mold and foamed.

  The volume expands to about 2 times due to foaming, the incomplete curing (softness remains) is cut to a desired size, and the panel body formed in a panel shape is carried into a steam kiln and heated. The reaction is caused to cure by steaming for about 5 to 10 hours under high pressure. In this way, a panel body can be obtained. However, unlike the panel body 4a described above, the reinforcing fibers 4b are not included.

  Such a hardened foamed cement material has a high water permeability because it contains many fine bubbles and pores communicating with them, and as such is unsuitable as an underground box.

  Therefore, similarly to the lightweight panel made of the above-mentioned foamed cement cement, the surface reinforcing layer 4c is formed on the surface of the panel body, and the surface reinforcing layer 4c is covered with the waterproof layer 4f, thereby reducing the weight of the underground buried box. The panel 4 can be used.

  In addition, the clearance gap between the opening edge of the knockout part in the side surface of the lower box part 3 and the said lightweight panel 4 is filled with the sealing material for filling the clearance gap and sealing.

3. Manufacturing Method of Underground Box FIG. 3 is a plan view showing the lightweight panel 4 before being attached to the lower box part 3.

  In the figure, a reinforcing bar 7 is embedded in the outer peripheral portion of the lightweight panel 4, and a part of the reinforcing bar 7 is projected in four directions in a state exposed from the outer peripheral surface of the lightweight panel 4 (exposed reinforcing bars 7a, 7b). 7c, 7d).

  The reinforcing bar 7 is used in both cases of the above-described foamed cement cured product and foamed cement cured product. In the following description, the case where the reinforcing bar 7 is provided on the foamed cement cured product will be described as a representative.

  FIG. 4 shows a lower box part mold 8 for manufacturing the lower box part 3 by setting the lightweight panel 4 having the above-described configuration.

  In the figure, a lower box part mold 8 includes a bottom plate 8a, four side plates 8b to 8e arranged on the bottom plate 8a to form a square tube, an intermediate frame 8f, and an upper portion of the assembled side plate. It is mainly composed of a top plate (not shown) that closes the opening.

  The lightweight panel 4 with the reinforcing bars is detachably fixed to the inner walls of the side plates 8b to 8e.

  Further, a reinforcing bar 9 for reinforcing the lower box part 3 is set so as to surround the box-shaped middle frame 8f.

  In the figure, reference numeral 10 denotes a spacer for positioning the reinforcing bar 9.

  Further, the convex portion 8g formed on the upper surface of the middle frame 8f is provided to form the opening of the hand hole, and has a size slightly smaller than that of the lightweight panel 4, and is formed on the middle frame 8f. The window frame 8h protruding in a window shape from the side face abuts on the lightweight panel 4 when the mold is closed, and secures an area not filled with lightweight concrete. The window frame 8h is formed such that the side wall portion 3b is formed into a window frame shape.

  Assembling the lower box part mold 8 having the above configuration into a box shape, a gap formed between the side plates 8b to 8e and the middle frame 8f, a gap formed between the middle frame 8f and the top plate, If any one of the lightweight concrete b to d is selected and filled, the lower box part 3 reinforced by the reinforcing bars 9 is manufactured.

  Further, since the reinforcing bars 7a to 7d (see FIG. 3) protruding from the periphery of the lightweight panel 4 are embedded in the filled concrete, the lightweight panel 4 is integrated with the side wall 3b simultaneously with the manufacture of the lower box part 3. It can be made.

  In addition, when the load (for example, earth pressure, water pressure, etc.) which acts on the lightweight panel 4 is small, the said reinforcing bar 7 can also be abbreviate | omitted.

  FIG. 5 shows an appearance of the lower box part 3 manufactured by the above method.

  A lightweight panel 4 is provided and integrated on the four side walls of the lower box part 3 in place of the thin knockout portion.

  The weight when a lower box part (outside dimension: 720 mm long x 720 mm wide x 530 mm high) is made of ordinary concrete is 240 kg, whereas the weight when a lower box part of the same size is produced according to the present invention is The weight was reduced to 150 kg and 38%.

In addition, the bending strength of the knockout portion when the lower box part is made of ordinary concrete is 3 to 6 N / mm ² , whereas the bending strength of the lightweight panel according to the present invention is 15 to 25 N / mm ² , An improvement in strength was observed over ordinary concrete.

4. Cross section structure of lower box parts
4.1 Side Wall Vertical Section Structure FIG. 6 shows a side wall vertical section of the lower box part 3.

  In the figure, an opening 3c is formed in the side wall 3b of the lower box part 3 by removing a window frame 8h when demolding, and a lightweight panel 4 is attached so as to close the opening 3c. It is integrated with the part 3b.

  Further, on the outer surface side of the opening 3c in the side wall portion 3b, step portions 3d and 3e that engage with the outer peripheral portion of the lightweight panel 4 are formed in the horizontal direction, and the direction in which earth pressure and water pressure act (arrows in the figure). In D), the outer peripheral portion of the lightweight panel 4 is supported.

  A grooved steel (reinforcing steel material) 11 as a reinforcing member is embedded on the inner side of the upper portion of the side wall portion 3b so as to reinforce the upper portion of the side wall. The embedded grooved steel 11 not only reinforces the strength, but also can prevent the occurrence of cracks in the stepped portion 3d due to earth pressure and water pressure.

  In this embodiment, the grooved steel 11 is used. However, as long as the member has a strength necessary for reinforcing the upper portion of the side wall, not only the grooved steel but also an angle steel, a flat steel, a spherical flat steel, etc. It can also be used. In the figure, reference numeral 12 denotes a sealing material that fills a gap formed between the opening edge of the knockout portion N and the lightweight panel 4 to achieve waterproofing.

4.2 Side Wall Cross Section Structure FIG. 7 shows a side wall cross section of the lower box part 3.

  In the same figure, step portions 3f and 3g that engage with the outer peripheral portion of the lightweight panel 4 are formed in the vertical direction at the opening edge of the side wall portion 3b, and the direction in which earth pressure and water pressure act (in the figure, arrows) In D), the outer peripheral portion of the lightweight panel 4 is supported.

  Inside the opening 3c in the side wall 3b, a flat steel (reinforcing steel material) 13 as another reinforcing member is embedded in the vertical direction, and both left and right opening edges of the side wall 3b are reinforced. . The buried flat bar 13 not only reinforces the strength, but also can prevent the stepped portions 3f and 3g from cracking due to earth pressure and water pressure. In the figure, reference numeral 12 denotes a sealing material.

  In addition, when it is desired to further increase the strength of the left and right opening edges of the side wall portion 3b, unequal side unequal thickness angle steel or spherical flat steel can be used.

5. Another Manufacturing Method for Underground Box In the above-described embodiment, the lightweight panel 4 is set in the lower box part mold, and the lightweight panel 4 is integrated with the side wall 3b simultaneously with the production of the lower box part 3. Although the method has been shown, the lightweight panel 4 can be attached to the opening edge of the side wall 3b after the lower box part is manufactured.

  Specifically, the side wall 3b having the opening 3c shown in FIG. 7 is manufactured as the lower box part 3, and the stepped parts 3f and 3g formed in the vicinity of the opening 3c are made of rubber, epoxy resin, urethane resin, gypsum. It is also possible to apply an adhesive such as a system, and fit and fix a lightweight panel to the stepped portions 3f and 3g to which the adhesive is applied, so as to be integrated with the lower box part 3. However, the lightweight panel in this case shall not be reinforced by the reinforcing bars 7.

  Thus, according to the method of fixing the lightweight panel to the side wall portion 3b in a separate process, it becomes possible to integrate the lightweight panel with the side wall portion 3b in a state where a joint for connecting underground pipes is attached to the lightweight panel. There is an advantage that the connection work of the underground pipe can be performed easily and in a short time.

  Although the present invention has been fully described with reference to the preferred embodiments with reference to the accompanying drawings, it is possible for those skilled in the art to implement the invention with various modifications and corrections. It should be understood that such variations and modifications are included in the technical scope of the present invention without departing from the scope of the problem-solving idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Underground box 2 Upper box part 2a Circular opening part 3 Lower box part 3a Bottom plate part 3b Side wall part (window frame side wall part)
3c opening 3d, 3e step 3f, 3g step 4 lightweight panel 4a panel body 4b reinforcing fiber 4c surface reinforcing layer 4d resin layer 4e reinforcing fiber 4f waterproofing layer 5 lid frame 6 lid 7 rebar 7a-7d exposed rebar 8 lower box parts Formwork 8a Bottom plate 8b-8e Side plate 8f Middle frame 8g Projection 8h Window frame 9 Reinforcement 10 Spacer 11 Channel steel (reinforcing steel)
12 Sealing material 13 Flat steel (steel material for reinforcement)

Claims (8)

A square or rectangular bottom plate,
A window frame-shaped side wall portion standing from each side of the bottom plate portion;
A lightweight panel constructed on the side wall so as to cover the opening of the side wall,
The lightweight panel is composed of a panel body made of a hardened foam cement in which reinforcing fibers and a large number of bubbles are dispersed almost uniformly in the cement, and FRP in which reinforcing fibers are embedded in a resin layer, and is laminated on the surface of the panel body. An underground burial box comprising a surface reinforcing layer integrated with the panel body.   The above-mentioned foamed cement hardened product is composed of a porous molded body in which cream foamed cement obtained by kneading cement, water, reinforcing fiber and foaming agent is filled into a mold and solidified, and has a specific gravity. The underground burial box according to claim 1, wherein is in the range of 0.5 to 1.5.   The underground burial box according to claim 1 or 2, wherein a waterproof layer is further laminated on an outer surface of the surface reinforcing layer.   The underground embedding box according to any one of claims 1 to 3, wherein a reinforcing bar is provided on an outer peripheral portion of the lightweight panel, and a part of the reinforcing bar protrudes from the outer peripheral portion of the lightweight panel and is embedded in the side wall portion.   The underground burial box according to any one of claims 1 to 4, wherein the bottom plate portion and the side wall portion are made of lightweight concrete.   The underground embedding box according to any one of claims 1 to 5, wherein a reinforcing steel material is embedded in an opening edge portion of the side wall portion. A panel made of a hardened foam cement in which reinforcing fibers and a large number of air bubbles are almost uniformly dispersed in the cement is formed.
FRP in which reinforcing fibers are embedded in a resin layer is laminated on the surface of the panel to form a reinforcing layer on the surface of the panel,
A lightweight panel in which the panel and the surface reinforcing layer are integrated is fixed to each inner surface of the side wall forming mold divided into four parts,
In the state where the lightweight panel and the inner frame are in close contact, the side wall forming mold is assembled into a square tube around the inner frame,
By filling concrete or lightweight concrete in the gap between the inner frame, the bottom surface forming frame, and the side wall forming frame, the side wall portion of the underground box is molded into a window frame shape and at the same time the opening of the side wall portion A method for manufacturing an underground burial box, wherein the lightweight panel is fitted into a portion and integrated with the side wall portion.   The manufacturing method of the underground burying box of Claim 7 which provides a reinforcing bar in the outer peripheral part of the said lightweight panel, and fixes to each inner surface of the said side wall formation mold in the state which protruded from the outer peripheral part.