JPH0438844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> This invention relates to improvements in reinforcing bar cages used in construction methods for underground structures such as continuous underground walls.

<<Conventional technology>> The method of constructing a continuous underground wall cast in place is constructed through the following steps.

This construction method involves building a reinforcing bar cage made up of reinforcing bars vertically and horizontally in a previously excavated trench, and pouring concrete into the excavated trench. Build an underground structure made of reinforced concrete that is integrated with the reinforcing bar cage in the section where the reinforcing bar cages are integrated, excavate a section adjacent to this preceding section in the same way, and connect the reinforcing bar cages to each other via the box joint, The underground structure is constructed using the same method as described above, and the process of successively paving is repeated.

One of the features of the above construction method is that the resulting underground structure has better compatibility with the surrounding ground than with conventional open caissons.

On the other hand, in this construction method, as a means to prevent the poured concrete from wrapping around the outer periphery of the housing joint, especially the side of the drawn plate and the bottom, which was a cause of problems at the joint part, for example,
As shown in Publication No. 10464, both sides and the entire bottom of the reinforcing bar cage are surrounded by sheet material in a bag shape,
Efforts are made to prevent concrete from leaking at the joints.

≪Problems to be solved by the invention≫ However, underground structures actually constructed using this type of construction method are characterized by a greater frictional resistance between the surrounding ground and the structure than, for example, the new caisson construction method. It is becoming.

In this regard, if the concrete leakage prevention mechanism is adopted, the sheet will be interposed between the ground and concrete in the finished state of the underground structure, and the poured concrete will be inside the sheet. Since the structure remains confined and the structure's surface has little effect on the ground, sufficient frictional resistance cannot be obtained and the characteristics of this type of construction method cannot be fully demonstrated.

The present invention has been made in view of the above problems, and its purpose is to substantially prevent concrete from going around the outer periphery of the enclosure joint, while allowing direct contact between the poured concrete and the ground. To provide a reinforcing bar cage for an underground structure construction method that can sufficiently improve the frictional force between the structure and the ground and eliminate waste of materials.

<<Means for Solving the Problems>> In order to achieve the above-mentioned object, the present invention erects a reinforcing bar cage having a box joint at its end in an excavated trench, and connects the trench via a tremie pipe. A reinforcing bar cage used in a method of constructing an underground structure by pouring concrete into a hole: On both sides and the bottom of the reinforcing bar cage, one end is fixed to both sides and the bottom of the housing joint. , the other end is temporarily fixed to the side and bottom surfaces of the reinforcing bar cage, and the length of the flexible wire mesh is at least enough to cover the tremie tube insertion position, and the wire mesh has a coarse mesh. The gist is that the mesh is set to a roughness that does not allow coarse aggregate contained in the concrete to pass through, but allows fine aggregate to pass through.

<<Operation>> Due to the casting pressure of the concrete cast through the tremie pipe, the temporarily fixed portion of the wire mesh separates from the reinforcing bar cage, is flexibly deformed, and comes into contact with the ground. In the side portions of the reinforcing bar cage where the wire mesh is not present, the concrete directly contacts the ground and hardens according to the uneven shape of the ground. The part where the wire mesh is present comes into contact with the ground through the wire mesh, but concrete components containing fine aggregate contained in the concrete leak through the wire mesh and come into direct contact with the ground.

At the same time, concrete is trying to get around through the wire mesh into the space between the body joint and the ground.
Only the fine aggregate penetrates the wire mesh, and since the coarse aggregate closes the mesh, there is no large amount of leakage, and leakage can be substantially prevented.

<<Example>> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a previously excavated trench hole excavated in the ground E, 2 is a reinforcing bar cage to be built in this excavated trench hole, and tremie pipes 3 are installed vertically in the hollow interior of the reinforcing bar cage 2 on both left and right sides. By sequentially pulling the tremie pipe 3 upward while discharging concrete 4 from its tip, the muddy water 5 filling the inside of the excavated trench 1 is replaced with concrete 4, and finally the above-mentioned An underground structure integrated with the reinforcing bar cage 2 is constructed.

The reinforcing bar cage 2 used in the above construction method basically consists of a reinforcing bar cage body 21 formed in a rectangular parallelepiped shape by combining reinforcing bars in a vertical and horizontal lattice pattern, and a thin iron plate integrated at both ends of the reinforcing bar cage body 21. It is composed of a rectangular housing joint 22 with a hollow interior.

One end portion of a wire mesh 23 is fixed to both sides of the housing joint 22 along its longitudinal direction, and is fixed to the bottom portion in an overlapping state.

The other end of the wire mesh 23 is temporarily fixed to both outer surfaces of the reinforcing bar cage main body 21, and is temporarily fixed to the bottom of the main body 21 in an overlapping state as described above.

The length of this wire mesh 23 is set to the length from the housing joint 22 to the point where it extends perpendicularly to the insertion position of the tremie tube 3 and covers this. This is the part that doesn't work.

As a temporary fixing means for the wire mesh 23, for example, a binding wire 24 for binding the reinforcing bars is used, and the binding wire 24 is sequentially cut from the bottom by the concrete placing pressure, and the wire mesh 2
3 is spaced apart from the side surface of the reinforcing bar cage main body 21.

Further, the mesh size of the wire mesh 23 is set to be larger than the diameter of the fine aggregate contained in the poured concrete 4 and smaller than the diameter of the coarse aggregate.

After erecting the reinforcing bar cage 2 with the above configuration in the excavated trench 1, insert the tremie pipe 3 into the planned insertion position of the tremie pipe, and pull it upward while discharging concrete 4 from the tip of the tremie pipe 3. The concrete 4 flows sequentially from the periphery of the tremie pipe 3 and fills the entire inside of the reinforcing bar cage body 21.

At this time, the portion where the wire mesh 23 is present is strongly pressed outward by the casting pressure, and as a result, the binding wire 24 for temporarily fixing the wire mesh 23 is cut.
The wire mesh 23 in a free state is flexibly deformed and strongly pressed against the wall surface of the excavation groove 1, thereby preventing the concrete flowing out from the central portion of the reinforcing bar cage body 21 from flowing toward the box joint 22 side.

Then, the concrete component containing fine aggregate flowing out from the wire mesh 23 flows and solidifies according to the uneven shape of the wall surface.

At the same time, since the wire mesh 23 is interposed between the outer side of the housing joint 22, which is near the fixed end of the wire mesh 23, and the wall surface of the excavation groove 1, leakage of the poured concrete 4 is prevented. do.

In this case, the concrete component containing fine aggregate in the concrete 4 leaks out of the wire mesh 23 and tries to enter the inside of the gap d, but the coarse aggregate present together with this fine aggregate leaks out of the wire mesh 23. Therefore, after the concrete component containing fine aggregate leaks out to some extent, the leakage stops, and there is virtually no problem caused by leakage of concrete to the outer periphery of the housing joint 23.

After completing the construction of the preceding underground structure as described above, the ground E adjacent to the enclosure joint 23 is excavated to form a trailing excavation groove, and the trailing reinforcing bar cage is inserted through the enclosure joint 23. By repeating the process of joining them together and pouring concrete in this state, the construction of a continuous underground wall is completed.

<<Effects>> As explained in detail by the embodiments above, in the reinforcing bar cage for underground structure construction method according to the present invention, the temporary reinforcement of the wire mesh is achieved by the casting pressure of the concrete discharged from the tremie pipe. The stop part separates from the reinforcing bar cage, flexibly deforms, and comes into contact with the earth. The concrete in the central part of the reinforcing bar cage, where the wire mesh is not present, comes into direct contact with the ground and hardens according to the uneven shape of the ground. The part where the wire mesh is present comes into contact with the ground through the wire mesh, but the fine aggregate contained in the concrete leaks through the wire mesh and comes into direct contact with the ground. Also, at the same time, concrete tries to get around through the wire mesh into the space between the box joint and the ground, but only fine aggregate leaks through the wire mesh, and coarse aggregate closes the wire mesh, resulting in a large amount of concrete. There was no leakage, and any substantial leakage could be prevented.

Therefore, in the present invention, the poured concrete and the ground can come into direct contact while substantially preventing the concrete from going around the outer periphery of the housing joint. Frictional resistance can be sufficiently improved.

Further, in the present invention, since the entire outer surface and bottom surface of the reinforcing bar cage body are not wrapped, waste of materials can be avoided.

[Brief explanation of drawings]

Figures 1a and b are plan views showing the construction method of continuous underground walls using the reinforcing bar cage according to the present invention, Figure 2 is a partial side sectional view showing a part of the same reinforcing bar cage, and Figure 3 is a FIG. 2 is a sectional view taken along the - line in FIG. 2; 1... Excavation groove, 2... Rebar cage, 3... Tremy pipe, 4... Concrete, 21... Rebar cage body,
22... Box joint, 23... Wire mesh, 24... Binding wire (temporary fastening means).

Claims (1)

[Scope of Claims] 1. A reinforcing bar cage with a box joint placed at the end is erected in the excavated trench, and concrete is poured into the trench via a tremie pipe to construct an underground structure. A reinforcing bar cage used in a construction method in which: one end is fixed to both sides and the bottom of the housing joint, and the other end is fixed to the side and bottom surfaces of the reinforcing bar cage, and at least A flexible wire mesh formed to a length that covers the tremie tube insertion position is temporarily fixed, and the coarseness of the wire mesh prevents coarse aggregate contained in the concrete from passing through, and A reinforcing bar cage for use in underground structure construction methods, characterized by having a mesh having a roughness that allows aggregate to pass through.