JPH03262836A - Underground structure and its construction - Google Patents

Abstract

PURPOSE:To reduce cost by conducting construction in water in which the bottom part of an underground continuous wall is blocked with a bottom plate, downward protrudedly and curvedly formed, and the bottom plate is fixed with plural anchors. CONSTITUTION:A part, surrounded with close-ringed tubular underwater continuous wall 10 in the natural ground G is underwater-excavated, and moreover a part lower than the lower end of the wall 10 is bowllikely excavated. Next a bottom plate 20, curvedly formed so as to be a downwardly protruded state, is intergratedly constructed with the continuous wall 10 in water to improve the bearing force of the bottom plate 20 against buoyancy. Then plural anchors, for supporting the bottom plate 20 with their upper end parts fixed to the bottom plate 20, are provided in water on the natural ground G under the bottom plate 20. This permits low-cost construction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an underground structure and a method of constructing the same, and in particular, to an underground structure that effectively reduces the buoyant force acting on the bottom slab (bottom slab) of an underground structure due to groundwater. Concerning underground structures that can be used and their construction methods.

[Conventional technology]

Conventionally, the caisson method has been known as a very common method for constructing underground structures. When constructing an underground structure using the caisson construction method, a method is adopted in which, for example, a concrete box is sunk into the ground while excavating the ground where the box will be installed.

However, in the method of constructing underground structures using the caisson construction method, as the caisson becomes larger, it becomes difficult to sink it, and when applied to large-diameter, deep-seated underground structures, the cost increases and the construction period is also shortened. There is a problem with the length.

Therefore, when the underground structure to be constructed is large-sized or located at a great depth, it is common to construct the underground structure using an underground continuous wall.

Because underground continuous walls are constructed as a concrete structure within the ground, they are easier to apply to larger and deeper underground structures than the caisson construction method, which involves sinking a ready-made structure. be.

[Problem to be solved by the invention]

By the way, even when constructing an underground structure using the underground continuous wall construction method as described above, there are the following problems.

In other words, as shown in Fig. 9, there is usually groundwater within the mountain G (line W in the figure indicates the groundwater level), so the bottom slab 20 of the underground structure I generally has buoyancy due to this groundwater. receive. In order to reduce this buoyancy, there are methods to actively drain groundwater, such as installing a spring water treatment layer at the bottom of the structure, but this drainage of groundwater causes deformation or collapse of the surrounding ground, causing May have a negative impact on the environment. For this reason, conventionally, as shown in Fig. 9, a water-stop wall was formed by embedding an underground continuous wall lO up to the impermeable layer 4 in the ground G, thereby preventing the intrusion of groundwater and The structure was designed to resist buoyancy.

However, in the underground structure I having the above structure, it is necessary to construct the underground continuous wall 10 extending far below the actual bottom of the underground structure, which increases the cost. There were some inconveniences.

The present invention has been made in view of the above circumstances, and it is possible to effectively suppress the buoyant force acting on the bottom plate, reduce the thickness of the bottom plate as much as possible, and reduce costs. It is an object of the present invention to provide an underground structure and a method for constructing the same, which can be effectively applied to structures.

[Means to solve the problem]

The underground structure according to claim 1 of the present invention includes an underground continuous wall formed in a cylindrical shape in the earth and forming the outer shell of the structure, and a bottom plate formed by closing the bottom of the underground continuous wall. and a plurality of anchors whose upper ends are fixed to the bottom plate and provided in the ground below the bottom plate, and the bottom plate is curved so as to be convex downward. It is characterized by:

The invention described in claim 2 of the present invention is a method for constructing an underground structure according to claim 1, which includes the step of constructing a closed cylindrical underground continuous wall in a horizontal plane in the ground, and a step of excavating a portion of the ground surrounded by the underground continuous wall and excavating a portion further below the lower end of the underground continuous wall into a bowl shape; A step of constructing a bottom slab in water that forms a bowl shape along the bottom and is integrated with the underground continuous wall, and supporting the bottom slab by fixing its upper end to the bottom slab in the ground below the bottom slab. The method is characterized by comprising a step of providing an anchor for the purpose underwater.

Furthermore, the invention described in claim 3 of the present invention is the method for constructing an underground structure according to claim 2, in which, when constructing the bottom slab, a reinforcing bar cage constituting the bottom slab is formed into a bowl shape, and The present invention is characterized in that an upper formwork that follows the shape of the upper surface of the reinforcing bar cage is attached in advance to the upper part of the reinforcing bar cage, and the reinforcing bar cage and the upper formwork are installed as one at the bottom of the excavation hole.

[Function] According to the underground structure according to the first aspect, the upward force acting on the bottom slab is supported by the anchor, and the resistance of the bottom slab to the buoyancy force is increased. Moreover, since the bottom plate is formed into a so-called bowl shape that is curved downward, the resistance of the bottom plate against buoyancy is improved.

Further, according to the method for constructing an underground structure according to claim 2,
Since the bottom slab is constructed underwater and the water in the underground continuous wall is drained after the bottom slab is fixed with anchors, construction can be carried out without creating buoyancy in the bottom slab even during construction.

According to the method for constructing an underground structure according to claim 3, there is no need to attach the formwork to the reinforcing bar cage while performing troublesome positioning operations at the bottom of the excavated hole. It is extremely effective when used in

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an underground structure according to the present invention. The underground structure l is constructed in the ground G,
In this case, the whole is formed into a cylindrical shape with a bottom. The underground structure 2 constitutes, for example, the foundation of a building, or an underground facility such as a building basement, an underground factory, or an underground parking lot. Line W within Mt. G in the map
represents the groundwater level, and numeral 4 represents the impermeable layer.

In the underground structure (hereinafter abbreviated as "structure") 1, reference numeral 10 denotes an underground continuous wall (hereinafter abbreviated as "continuous wall °") 20 that constitutes the side wall of the structure 1. is a bottom plate of the structure 1, and reference numeral 30 is an anchor whose upper end is fixed to the bottom plate 20 and is driven into the ground below the bottom plate 20.The structure 1 may be used, for example, as an underground facility. In this case, a permanent floor slab (as shown) is constructed on top of the bottom slab 20.

Here, the bottom plate 20 is curved so as to be convex downward, and is formed in a so-called bowl shape.

Further, as shown in the figure, the inner diameter portion of the bottom plate 20 is formed to have a bowl shape with a slightly smaller diameter than the inner diameter of the continuous wall 10. In this case, the bottom plate 20 is continuous! ! A portion of L10 that goes inside the inner surface 10a extends slightly upward along the inner surface 10a.

The above structure 1 is constructed by the following steps.

, Construction of underground continuous wall The underground continuous wall 10 is constructed within the ground G. This underground continuous wall IO may be constructed by a conventional common underground continuous wall construction method.

Since this underground continuous wall (20) forms the outer shell of the Fi structure relic, its cross-sectional shape may be arbitrarily determined depending on the structure (1). In this embodiment, this underground continuous wall 10 is
It is formed into a cylindrical shape with a circular cross section.

, Underwater excavation Once the underground continuous wall 10 is constructed, the part of the ground G surrounded by the continuous wall 10 and further the part further below the lower end of the continuous wall 10 is excavated. This excavation work
This is done using the underwater drilling method while storing water in the excavation area. This underwater excavation method may also be carried out according to the method generally practiced in the past.

The water 3 to be stored may be fresh water or muddy water. At this time, the portion below the continuous wall 10 is excavated in a so-called bowl shape so that the excavated surface is curved downward. that time,
Excavation of the portion corresponding to the continuous wall IO can be carried out using a general clamshell or the like, and excavation below the lower end of the continuous wall IO can be carried out using a boom cutter device 50, for example, as shown in FIG. By using this, it is possible to form an excavated hole having a diameter larger than the inner diameter of the continuous wall IO.

iii. Construction of bottom slab Next, the bottom slab 20 is constructed at the bottom of the excavated hole 2 formed by the underwater excavation.

1ii-■ In order to integrate the bottom slab 20 to be formed in the bottom slab construction part of the underground continuous wall with the underground continuous wall IO, the bottom slab, 2 on the inner surface 10a of the underground continuous wall IO is installed.
Carve the bottom edge where 0 is to be formed.

In this embodiment, this cleaning work is performed using a cleaning device 60 shown in FIGS. 3 and 4.

Here, the configuration of this cleaning device 60 will be explained.

The cleaning device 60 is suspended and supported by a lifting means installed on the ground, and is opened from the upper opening of the excavation hole 2.
inserted within. The keren device 60 includes a ring-shaped frame 61, at least three guide arms 62 (four in the illustrated example) extending radially from the frame 61, and at least three guide arms 62 (four guide arms 62 in the illustrated example) extending radially from the frame 61. The main component includes an injection nozzle 66 provided at the tip of a shaft portion 65.

The frame 6I is suspended and supported so as to be rotatable around the axis of a center ball (support member) 67, with the center of the ring body as the center of rotation. The guide arm 62 is
In this case, it is configured to be extendable and retractable in the longitudinal direction by the operation of a hydraulic jack 68, and a wheel 64 is provided at the tip that comes into contact with the wall surface of the underground continuous wall IO. The frame 61 has this guide arm 62 connected to the underground continuous wall lO.
Horizontal movement is restricted by tensioning the inner surface. Further, the injection nozzle 66 is set at a position where its tip is slightly retracted from the tip of the guide arm 62.

Using the cleaning device 60 having the above configuration, when the entire cleaning device 60 is rotated while injecting water and air vigorously from the injection nozzle 66, the jet from the injection nozzle 66 flows into the inner surface of the underground wall lO. Adhering soil and the like on the lower end portion 10a and the lower end surface 10b can be removed to expose the concrete surface.

Mountain - ■ Assembling the reinforcing bar cage Once the inner surface of the lower end of the underground continuous wall 10 has been cleaned,
The reinforcing bar cage 21 for constructing the floor slab 20 is assembled.

The reinforcing bar cage 21 is assembled on a barge, for example, by floating a barge on the surface of water 3 stored in the excavated hole 2.

Here, as shown in FIG. 5, this reinforcing bar cage 21 is formed into a bowl shape as a whole, and has a vertical shape. Further, on the upper part of the reinforcing bar 21, a formwork (upper formwork) 29 previously formed in a bowl shape so as to follow the top surface shape of the reinforcing bar cage 21 is installed.
Fix it together.

Furthermore, in this embodiment, the reinforcing bar cage 21 is provided with an auxiliary tremie tube 26 for connecting a tremie tube 25, which will be described later, as shown in the drawing, and an anchor guide tube 31, which will be described later.
An auxiliary anchor guide tube 32 for connecting the anchor guide tubes is provided integrally in advance. Auxiliary tube 2 for these tremie tubes
6 and the anchor guide pipe auxiliary pipe 32 are both provided vertically penetrating the formwork 29 and the reinforcing bar cage 21, and are arranged at a plurality of locations on the reinforcing bar cage 21 at predetermined intervals. The tremie tube auxiliary pipe 26 has, for example, its lower end terminating slightly above the lower end of the reinforcing bar basket 21 as shown in the figure, while its upper end projects upward from the formwork 29. Further, the anchor guide pipe auxiliary pipe 32 has its lower end positioned approximately at the same position as the lower end of the reinforcing bar cage 21, and its upper end protrudes above the formwork 29.

Moreover, a plug material 33 for temporarily closing the opening is packed in the lower end opening of this anchor guide tube auxiliary tube 32. The plug material 33 is, for example, a rubber plug, wood mortar, or the like. Furthermore, connection means (not shown) such as screws are provided at the upper ends of both of the auxiliary pipes 26.32. Incidentally, reference numeral 27 is an anchor reinforcing bar for integrating the bottom slab 20 formed by the reinforcing bar basket 21 with the main floor slab installed later on the upper part of the bottom slab 20.

111-■ Sinking the reinforcing bar cage Once the reinforcing bar basket 21 integrated with the formwork 29 as described above is assembled, the reinforcing bar cage 21 is once lifted upward,
Remove the barge mentioned above.

Thereafter, the reinforcing bar basket 21 is gradually suspended into the excavated hole 2 and is brought to the bottom of the excavated hole 2. At this time, the reinforcing bar cage 2
1, as shown in FIG. 6, the branch pipes 25a, 25a,
... and branch tubes 31a, 31 of the anchor guide tube 31
A, ... will be added one after another on the water. That is, the first of the branch pipes 25a, 25a, .

The first one is connected to the anchor guide pipe auxiliary pipe 32 which is also provided in the reinforcing bar cage 21. In addition, the tremie tube 25 and the anchor guide tube 31
In the state where the reinforcing bar cage 21 is sunk to the bottom of the excavated hole 2, its upper end is extended at least to the point where it protrudes above the water surface.

11-■ Placing concrete on the bottom slab Once the reinforcing bar cage 21 has been placed at the bottom of the excavated hole 2 as described above, concrete is placed inside the formwork 29, that is, at the bottom of the excavated hole 2, using the tremie pipe 25. (shown in Figure 7) is poured underwater. The poured concrete 28 is discharged from the lower end of the tremie pipe 25, that is, in this case, from the lower end opening of the auxiliary pipe 26 for the tremie pipe. At this time, as the concrete 28 is being filled into the formwork 29, a force is applied to the formwork 29 that tries to push the formwork 29 upward, so that force is transferred to the anchor guide pipe 31 3.
1, supported by... In this case, the anchor guide pipe 31 is supported on the ground (aquatic part).

The reinforcing bar cage 21 is buried in poured concrete 28. Further, the concrete 28 also sinks into the inner surface 10a side of the continuous wall 10, but since the inner surface 10a and the lower end surface 10b of the continuous wall IO are smeared by the above-mentioned smearing device 60, the poured concrete 28
The inner surface 10a and the lower end surface 10b of the underground continuous wall 10 are completely in contact with each other, and the underground continuous wall IO and the concrete 28
Reliable water shielding is achieved by structurally integrating the connection surface with the Once the concrete 28 has hardened, the bowl-shaped bottom plate 20 is completed. Note that the tremie pipe 25 may be removed when the concrete 28 is finished being poured.

iv. Installation of anchors Once the bottom slab 20 has been constructed, the anchors 30 for fixing the bottom slab 20 are installed in the ground beneath the formed bottom slab 20. The installation work of the anchor 20 itself is similar to the commonly used earth anchor construction method, but
In this example (the present invention), this is carried out underwater.

1v-■ To install the hole-drilling anchor 30, first, a hole is drilled to bury the anchor 30, but this hole-drilling work is performed by using the anchor guide pipe 31 as shown in FIG. It is possible to do this from above the water surface. That is, a casing drill 34 for drilling holes is installed in the anchor guide pipe 31.
is inserted, and the casing drill 34 is brought to the ground G on the lower surface of the bottom plate 20 via the auxiliary pipe 32 for the anchor guide pipe, and from this state, downward drilling is started. The plug material 3 provided at the lower end of the auxiliary pipe 32 for anchor guide pipe
3 is removed during this drilling.

As described above, the reinforcing bar cage 21 and the formwork 29 constituting the bottom plate 20 are provided with the anchor guide pipe auxiliary pipe 32 for inserting the casing drill 34 in advance, and from this anchor guide pipe auxiliary pipe 32 Since the anchor guide pipe 31 extends above the water surface, the bottom plate 20
This makes it possible to easily perform the drilling work after construction, and moreover, the drilling work can be easily performed while water 3 is stored in the excavated hole 2.

1v-■ Installation of PC material and filling of mortar Once a hole of a predetermined depth has been formed, a PC material 36 (FIG. 8) is inserted into the casing drill 34. Thereafter, a hardened filler 37 such as mortar is injected into the bottom of the drilled hole, and then the casing drill 34 is pulled out.

1v-■ Introducing tension to the PC material After the cured filler 37 has hardened, the PC material 36 is tensioned in the following manner.

First, the anchor guide tube 31 is removed from the anchor guide tube auxiliary tube 32 and removed. In this state,
Since the concrete 28 has already completely hardened and the formwork 29 is also integrated with the concrete 28, even if the anchor guide pipe 31 is removed, the formwork 29 will not be lifted up unlike when the concrete 28 is poured. The anchor guide tube 31 and the anchor guide tube auxiliary tube 32 can be separated by, for example, screwing the screws connecting the anchor guide tube auxiliary tube 32 and the branch tube 31a directly connected to the auxiliary tube 32 into each branch tube 31a, 31a, . . . If the screws connecting them are configured with opposite threads, the anchor guide tube 31 can be removed by simply turning the anchor guide tube 31 in a predetermined direction.
1 is removed from the anchor guide pipe auxiliary pipe 32, so it can be carried out above the water.

After the anchor guide pipe 31 is removed, first, the anchor fixing plate 38 shown in FIG.
0 (The bottom of the mold 29). However, in this case, the upper end of the anchor guide tube auxiliary tube 32 protrudes from the upper surface of the formwork 29, and the anchor fixing plate 38 that has slipped down is at a position where it abuts on the anchor guide tube auxiliary tube 32. Since the anchor plate 38 does not reach the stop form 29, a leg 38a is provided at the lower part of the anchor fixing plate 38, and this leg 38a abuts against the upper surface of the form 29. Further, the anchor fixing plate 38 is provided with a chuck 39 that can grip the PC material 36 by a wedge action when the PC material 36 moves downward.

Next, similarly to the anchor fixing plate 38, the center hole gloss 40 is submerged in water using the PC material 36 as a guide, and is made to reach the anchor fixing plate 38. Reference numeral 41 is a hydraulic hose that extends to the upper part of the water and operates the center hold jack 40. After that, using this center hole jack 40, the PC material 3 is
It is sufficient to introduce tension force in step 6. The center hole jack 40 can be operated above the water. Therefore, when the tensile force is released after tensioning the PC material 36 with the center hole jack 40, the PC material 36 is restrained from relaxing by the action of the chuck 39 of the anchor fixing plate 38 (that is, the tension force is introduced). ), and the tension force is introduced into the bottom plate 20 via the anchor fixation plate 38.

V, drainage, etc. Once the anchor 30 is installed as described above, the excavated hole 2
Drain the water 3 inside. Thereafter, by cutting the PC material 36 above the anchor fixing plate 38, the intended underground structure 1 is completed.

When the underground structure 1 is to be used, for example, as an underground facility serving as a living space, a permanent floor slab may be placed on top of the bottom slab 20.

Furthermore, for example, the underground structure 1 may be further formed into multiple layers, or the above-ground part of a building may be constructed above the underground structure 1, etc., depending on the purpose of the underground structure 1. It is optional to further develop the structure.

According to the underground structure 1 having the above structure, the anchor 30 can support the buoyant force acting on the bottom slab 20 due to the influence of groundwater, and can prevent the bottom slab 20 from floating or deforming. As a result, there is no need to extend the underground continuous wall IO far below the bottom slab 20 more than necessary, unlike conventional underground structures constructed using underground continuous walls, and the penetration depth can be shortened. to reduce construction costs,
The construction period can be shortened.

Further, since the bottom plate 20 is formed to be curved downward so as to have a bowl shape, the resistance of the bottom plate 20 to buoyancy can be increased.

Furthermore, in the example, by forming the excavated hole 2 below the continuous wall IO to have a larger diameter than the inner diameter of the continuous wall IO, the concrete 28 constituting the bottom plate 20 can go around the lower part of the continuous wall IO. Since the structure is such that the bottom plate 20 is locked to the lower end surface 10b of the continuous wall IO, the buoyant force acting on the bottom plate 20 is also supported by the continuous wall IO, and the buoyant force acting on the bottom plate 20 is reduced. It can be supported more reliably.

Moreover, according to the construction method described above, it goes without saying that the underground structure 1 described above can be reliably realized, but also has the following effects. That is, the bottom plate 20 is constructed with the excavated hole 2 filled with water 3, and the bottom plate 20 is fixed with the anchor 30 in the state where the water 3 is present, and then the water 3 is drained. Bottom plate 2 after complete fixation
The applied load (water 3) to 0 is removed, and the bottom plate 2
0 is not affected by the buoyancy of groundwater even during construction.

Furthermore, in the above construction method, when installing the reinforcing bar cage 21 at the bottom of the excavated hole 2, the formwork 29 is integrally attached to the reinforcing bar cage 21 constituting the floor slab 20, so that the mold There is no need to separately install the frame 29, and work efficiency can be improved.

This is especially true because these reinforcing bar cages 21 and the like are installed underwater, and it is extremely difficult to fix the formwork 29 at a predetermined position of the reinforcing bar cage 21 after the reinforcing bar cages 21 are installed and underwater. It is extremely effective when taking this into account.

In addition, in the above embodiment, since the cleaning device 60 can reliably clean the joint portion of the continuous wall IO with the bottom slab 20, that is, the lower part of the inner surface IOa and the lower end surface 10b of the continuous wall IO, the bottom slab 20 and the underground continuous wall can be cleaned by the cleaning device 60. It has excellent effects such as increased integration and adhesion with 10 and reliable water-blocking properties.

C Effect of the Invention] As explained above, according to the underground structure described in claim 1 of the present invention, the anchor can support the buoyant force acting on the bottom slab, and prevent the bottom slab from lifting or deforming. This eliminates the need to extend the underground continuous wall far below the bottom slab unnecessarily, unlike conventional underground structures constructed using underground continuous walls.
By shortening the penetration depth, it is possible to reduce construction costs and shorten the construction period. Moreover, since the bottom plate is curved downward to form a bowl shape, it is possible to greatly increase the bottom plate's resistance to buoyancy and make the wall thinner, making it especially suitable for large and deep underground structures. Can be applied effectively.

Further, according to the method for constructing an underground structure described in claim 2, in addition to being able to reliably realize the above-mentioned underground structure, the bottom slab is constructed with the excavation hole filled with water,
Moreover, since water is drained after fixing the bottom slab with anchors in the presence of water, the battlefield load (water) on the bottom slab is removed after the bottom slab is completely fixed, and even during construction can be constructed without being affected by buoyancy.

Furthermore, according to the method for constructing an underground structure according to claim 3, when carrying out the method for constructing an underground structure according to claim 2, a reinforcing bar cage constituting the floor slab is installed at the bottom of the excavation hole. Since the formwork is integrally attached to the reinforcing bar cage in advance, there is no need to separately install the formwork, and it is possible to achieve effects such as greatly improving efficiency, especially in underwater work.

[Brief explanation of drawings]

FIG. 1 is an overall side view showing one embodiment of an underground structure according to the present invention, and FIGS. 2 to 8 show an embodiment of the method for constructing an underground structure according to the present invention. The figure is a partial side sectional view showing the formation state of the excavation hole, Figure 3 is a plan view showing the Keren device together with the underground continuous wall, Figure 4 is a side sectional view of Figure 3, and Figure 5
The figure is a partial side view showing the reinforcing bar cage, Fig. 6 is a partial side sectional view showing the installed state of the reinforcing bar cage, Fig. 7 is a partial side sectional view showing the installed state of the anchor, and Fig. 8 is the tension of the PC steel bar. FIG. 9 is a partial side sectional view showing the state, and is a side sectional view of the entire underground structure for explaining the prior art. 21...Reinforced cage, 29...Formwork (upper formwork), 30...Anchor

Claims (3)

[Claims] (1) An underground continuous wall formed in a cylindrical shape in the earth and forming the outer shell of the structure, a bottom slab formed by closing the bottom of the underground continuous wall, and a top end fixed to the bottom slab. An underground structure comprising a plurality of anchors provided in the ground below the bottom slab, and the bottom slab is curved so as to be convex downward. (2) A method for constructing an underground structure according to claim 1, comprising:
A step of constructing a closed cylindrical diaphragm wall in a horizontal plane in the ground, and excavating a portion of the ground surrounded by the diaphragm wall by underwater excavation, and further excavating the area from the bottom end of the diaphragm wall. a step of excavating the lower part into a bowl shape; and a step of constructing underwater a bottom slab that forms a bowl shape along the bottom of the excavation hole formed by the step and is integrated with the underground continuous wall. A method for constructing an underground structure, comprising the steps of: providing an anchor in the ground below the bottom slab, the upper end of which is fixed to the bottom slab to support the bottom slab. (3) In the method for constructing an underground structure according to claim 2,
When constructing the bottom plate, the reinforcing bar basket constituting the bottom slab is formed into a bowl shape, and an upper formwork that follows the top surface shape of the reinforcing bar cage is attached in advance to the top of the reinforcing bar cage, and these reinforcing bar cages are and a method for constructing an underground structure, comprising installing the upper formwork as one piece at the bottom of the excavation hole.