JPH0160634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing a water tank wall in an underground water tank used as a fire protection water tank, a water receiving tank, or the like.

Conventional underground water tanks are classified into steel, reinforced concrete, FRP, etc. based on the construction material.
Among them, underground water storage tanks made of reinforced concrete are the mainstream, and the structures include cast-in-place RC structures, cast-in-place prestressed concrete structures, or so-called prefabricated RC made of precast materials produced in factories.
Structures are diversifying, including prefabricated and prestressed concrete structures.

By the way, when constructing this type of reinforced concrete underground water storage tank, it goes without saying that safety and reliability are required in the construction design and construction, but also low construction costs, short construction times, and construction site availability. It is desirable to make effective use of the materials and facilitate quality control.

However, each of the above-mentioned structures has advantages and disadvantages. For example, cast-in-place concrete can be installed in narrow spaces and is low cost, but it takes a lot of time to cure the concrete, and the construction period may be longer if the site is in a high-traffic area or in a residential area. It becomes a problem. On the other hand, in the case of prefabrication, although it has advantages such as easy quality control and a short construction period, it has disadvantages such as the weight of each member, making it difficult to install in a narrow space, and high cost.

The present invention has been made in consideration of the above-mentioned points, and the cutting edge part is prefabricated, and the peripheral wall of the water tank is formed with cast-in-place concrete on the upper part of the cutting edge part, thereby forming a water storage tank. The purpose of the present invention is to provide a method for constructing a water tank wall in an underground water tank that can improve the accuracy of the base and start construction of the submerged box early, is easy to install in a narrow space, and can reduce costs. shall be.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The method for constructing a water tank wall in an underground water tank according to the present invention is as shown in FIG. 1. First, as shown in FIG. The blade segment 1, which has a shape and includes reinforcing bars (not shown) inside, is connected in a ring shape on the ground G of the construction site to assemble the blade part 2, which forms the base of the water tank body.

Then, as shown in FIG. 2, a form 3 for the peripheral wall of the water tank consisting of an inner form 3a and an outer form 3b is placed above the blade mouth part 2, and the peripheral wall is placed inside the form 3. A reinforcing bar unit 4 is set to provide reinforcement. Note that the inner formwork 3a is supported by a stay 6 between it and a weight 5 installed inside the peripheral wall. Further, it is not necessary to particularly install this weight 5 as long as the stay 6 can be supported by the inner formwork 3a.

When the above-mentioned formwork 3 and reinforcing bar unit 4 have been set, concrete is poured to form the peripheral wall 7 of the water tank, as shown in FIG. At this time, the concrete is integrated with the blade opening 2 to form a water tank wall A consisting of the peripheral wall 7 and the blade opening 2.

Next, even if the concrete does not reach an appropriate strength, that is, a strength that can withstand the earth pressure when sinking the water tank wall A into the ground, the outer formwork 3b
When the concrete reaches a strength that can be removed from the mold, the weight 5 is placed outside the water tank wall A, and before the concrete reaches a predetermined strength, the ground G inside the water tank wall A is excavated to remove the soil inside. be carried outside. As the ground G within the water tank wall A is excavated one after another, the water tank wall A sinks due to its own weight and is buried underground.

Note that the inner wall frame 3a is left without being removed from the mold in order to protect and cure the peripheral wall 7. In this subcase construction, the cutting edge portion 2 is assembled by cutting edge segments 1 made of precast concrete or the like previously formed in a factory, etc., so that the accuracy of the base of the water tank wall A can be improved, and the peripheral wall The ground G can be excavated before curing in step 7. That is, since the earth pressure applied to the surrounding wall 7 during the subcase construction is smaller than the earth pressure at the cutting edge portion 2, the strength of the circumferential wall 7 after demolding the formwork does not impede the subcase construction. Therefore, it is possible to start construction of the submersible at an early stage, and since the peripheral wall 7 is formed of cast-in-place concrete, installation in a narrow area is easy and costs can be reduced.

After the water tank wall A has been lowered to a predetermined position in the ground, the inner formwork 3a is first removed from the mold as shown in FIG. 5, and a layer of chestnut stone, split stone, etc. So-called ground hardening is performed by applying foundation material 11 and foundation concrete 12 as sacrificial concrete. After solidifying the ground, the main reinforcing bars 13 and distribution bars 1 are placed on the bottom slab.
4 is reinforced and concrete is poured to form the bottom slab 10. At this time, as shown in the figure, the bottom plate 10 is formed higher than the joint between the blade mouth portion 2 and the peripheral wall 7, so that the water-stopping effect in this portion is enhanced.

After the bottom slab 10 is cast, prestress is introduced into the water tank wall A, as shown in FIG. When introducing this prestress, one end should be fixed in advance to the PC tendon fixing box cutout 2a of the cutting edge part 2 (see also Fig. 1) and the other end to the upper end of the surrounding wall 7 before construction of the subcase. , and using prestressing tendons (PC stranded wires) 15 arranged in a diagonal lattice pattern at angles to each other when viewed from the side, as shown in the illustrated example, the surrounding wall 7 is Prestress is introduced by tensioning the prestressing tendon 15 at the upper end of the holder.

In addition, the above-mentioned method of arranging the tendons 15 is particularly as follows.
The present invention is not limited to the embodiment. For example, the tendons 15 may be arranged vertically and horizontally only in the circumferential direction or the vertical direction, as in the conventional case. Since prestress can be introduced from the upper end of the peripheral wall 7 in the circumferential direction and in the vertical direction of the peripheral wall 7 after construction, work on site is easy and workability can be improved.

Next, a top slab segment 20 made of precast concrete or the like, which has been previously formed in a factory or the like to have a certain size and shape, is passed over the upper part of the water tank wall A to open the underground water tank as shown in FIG. Top version 2
Assemble 1. In addition, the above top plate segment 20
A prestress is introduced in advance in the length direction thereof, and after the top plate 21 is assembled, a prestress is introduced in the joint direction of the top plate segment 20.

The top plate 21 may be constructed by assembling a precast material as in the embodiment, but is not particularly limited to this, and may be formed from cast-in-place concrete. In this way, the top plate 21 is attached to the water tank wall A.
and finally backfill the top of the water tank. Note that 22 in the figure indicates a manhole.

As described above in detail, the present invention connects the cutting edge segments made of precast concrete or the like on the ground at the construction site to assemble the cutting edge part, and then molds concrete onto the upper part of the cutting edge part by formwork. forming a peripheral wall of the water tank consisting of the above concrete, and excavating the ground within the water tank wall consisting of the cutting edge part and the surrounding wall during the curing period of the concrete, and extending the water tank wall to a predetermined position underground. Since it is characterized by sinking, it is possible to improve the precision of the foundation and facilitate the early start of submerged box construction, and it also facilitates installation in narrow spaces and reduces costs. It has excellent effects.

[Brief explanation of drawings]

The figures are shown to explain the method of constructing a water tank wall in an underground water tank according to the present invention. FIG. 1 is a half-sectional view showing the assembled state of the cutting edge part, and FIG. Figure 3 is a cross-sectional view showing the state in which the formwork is placed, Figure 3 is a cross-sectional view showing the state in which concrete is poured into the formwork, Figure 4 is a cross-sectional view showing the construction state of the water tank wall, and Figure 5 is the water tank. A sectional view showing the state where the wall is sunk; Figure 6 is a half cross section similar to Figure 5;
The figure is a sectional view illustrating the completed state. G...Ground, 2...Blade opening, A...Water tank wall.

Claims (1)

[Claims] 1. Assemble the cutting edge segment by connecting the cutting edge segments made of pre-cast concrete etc. on the ground at the construction site, form the peripheral wall of the water tank made of concrete on the upper part of the cutting edge part by molding, An underground water storage tank characterized in that, during the curing period of the concrete, the ground within the water tank wall consisting of the cutting edge portion and the peripheral wall is excavated to sink the water tank wall to a predetermined position in the ground. How to construct a water tank wall in.