JPH0447085B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is useful when using a continuous underground wall for a main structure, when increasing rigidity in order to effectively utilize the space within the continuous underground wall, etc. This article relates to a method for constructing continuous underground walls using cast-in-place methods that introduce prestress in the depth direction.

[Prior art and problems to be solved by the invention] Since conventional continuous underground walls are made of RC, there are concerns about adverse effects and cracks due to residual stress during temporary construction. However, some of them were difficult to use, and most of them could only be used as temporary structures, making them uneconomical.

Even during temporary construction, a large cross-section increases the cost to increase rigidity, and as the depth increases, the number of struts continues to increase, and the space within the continuous underground wall is restricted, making it difficult to carry out work inside. There were many cases where this caused problems.

An example of conventionally introducing prestress into a continuous underground wall is the invention of JP-A-62-242008, but this invention introduces prestress horizontally with the main purpose of ensuring the joints of each element. Therefore, it did not act on the tensile stress generated in the wall due to earth pressure, etc., and even though it could cover some cracks caused by quality etc., it did not cover cracks caused by stress. Furthermore, even if this invention is applied to a cylindrical shaft or structure, if it is circular, the entire cross section will be compressed, so introducing compressive stress in advance to the cross section to be compressed can be said to have a positive effect on the structure. It wasn't.

Also, as a continuous underground wall using pretension,
There is a construction method that uses precast plates as walls. Among these, other than the small-scale construction method that uses parent piles, installing precast slabs on trench walls increases the wall thickness and weight as the depth increases, and requires a large work yard and temporary construction of crane equipment with the necessary lifting capacity. equipment, costs,
Requires work space. Furthermore, it is difficult to manufacture and transport especially long and large precast plates;
There are also problems with preventing displacement and curing equipment when manufacturing walls on site. Furthermore, even if grout is injected into the gap created between the precast plate and the groove wall when the precast plate is hemmed, there are many problems such as ground displacement, watertightness due to grout holes, and loss of cross section. Due to the above-mentioned problems, there are only a few examples of construction, and the current situation is that the introduction of prestressing cannot be effectively utilized industrially using conventional construction methods.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and the gist thereof is as set forth in claims 1 and 2 of the present application.

Although the construction method of the present invention can be applied to constructing continuous underground walls of any size and depth, it is particularly suitable for constructing continuous underground walls with deep depths. It is also a construction method suitable for continuous underground walls that are subject to severe earth pressure, water pressure, or other loading conditions.

Normally, a steel plate may be used as the bearing plate provided at the lower end of the PC steel material used in the present invention, but if trench excavation is performed by muddy water excavation, slime removal holes are provided in the bearing plate to prevent slime from remaining on the bearing plate. It is preferable.

The PC steel material used in the present invention is not particularly limited, but preferably a PC steel bar or a PC strand. Moreover, the PC steel material naturally includes those in which the PC steel material is inserted into the sheath.

A major feature of the present invention is that prestress is introduced in the depth direction. For this reason, prestressing steel is installed in the depth direction. By introducing prestress in the depth direction, the rigidity of continuous underground walls can be dramatically increased, and PC walls can be constructed economically using the cast-in-place method similar to the construction of conventional RC walls. This can easily solve problems when using the main unit.

In the invention of claim 2 of the present application, a prestressed steel material is used in which a sheath provided with an exhaust pipe is fitted onto the prestressed steel material. The exhaust pipe is necessary for evacuation when injecting grout into the sheath, and may be provided either inside or outside the sheath, but is preferably used at the lower end of the sheath.

[Example] Next, an example of the present invention will be described in detail based on the drawings.

First, as shown in FIG. 1, the reinforcing bar cage 7 and the prestressed steel bar 5 fitted with the sheath 3 are assembled on the ground, the bearing plate 6 is fastened to the lower end of the prestressed steel bar 5 with the fastening fitting 13, and the It was installed in trench 2, which was excavated by mud excavation. FIG. 2 is a cross-sectional view in the groove extension direction in which only the arrangement of the PC steel bars 5, the bearing plate 6, and the exhaust pipe 9 are illustrated without showing the reinforcing bar cage 7 in order to make it easier to understand the installation state in the groove 2. .

Next, underwater concrete 10 was cast using a tremie pipe (not shown). Next, after the underwater concrete 10 was hardened to a predetermined strength, the PC steel rod 5 was tensioned using the jack 14 provided on the cone 16, as shown in FIGS. 3 and 4. Then, grout 8 was injected and filled into the sheath 3. Fifth
The figure is a sectional view showing the state of the sheath 3 and the PC steel rod 4 after grout 8 has been injected and filled.

FIG. 6 is a diagram showing an example of the bearing pressure (reaction force) plate 6 used in the embodiment of the present invention, in which slime extraction holes 12 were processed so that residual slime 14 would not remain on the bearing pressure plate 6. This is an example. 15 is a PC steel material attachment part.

FIG. 7 shows the state of the lower part of the continuous underground wall constructed according to the embodiment of the present invention, and shows the state in which the PC steel material 4 is fixed to the bearing plate 6 with the fastening fittings 13. Furthermore, an exhaust pipe 9 for injecting grout 8 into the sheath 3 was installed near the bearing plate. Grit bars 11 were attached to the bearing plate for reinforcement. The above device is installed on land together with reinforcing bars 7 to prevent any displacement or deformation when placing underwater concrete 10.
7. Assemble firmly while fixing to the horizontal reinforcement 18, and then tighten the groove 2.
It was installed after the slime processing was completed.

[Effects of the Invention] Since the present invention is configured as described above, it has the following intended effects.

●Adverse effects due to residual stress during temporary installation when using the main unit.
You can suppress cracks.

●The rigidity of the wall can be increased and the space inside the wall can be used effectively.

●An economical PC wall can be constructed by casting on site using the same method as conventional RC walls.

To explain in more detail, when conventional continuous underground walls are used as main bodies, there is an adverse effect due to residual stress during temporary construction, that is, when conventional RC walls are bent due to construction pressure, etc.
On the tensile side, both the reinforcing steel and concrete resist at the same time, causing the concrete to crepe and eventually crack, causing the reinforcing steel to resist. (See Figure 8), which caused problems in expecting a synthetic effect when used in a part of the main structure, but by introducing prestress in the depth direction with the present invention. , since the stress during temporary construction can be applied effectively to the entire cross section (see Figure 9), the cross section will not creep, so the rigidity effect when using the main body becomes clear, and the conventional load sharing is lower than the estimated value. Since it is possible to obtain reliable values, safe and economical designs can be made.Also, by introducing prestress in the depth direction, the rigidity increases in the depth direction, so the spacing between the struts can be widened. This makes it possible to effectively utilize the space within the wall, and furthermore, the method and equipment according to the present invention make it possible to use conventional RC.
Economical, cast-in-place method similar to building walls
It is possible to build a PC wall.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing a continuous underground wall constructed according to an embodiment of the present invention and prestressed in the depth direction, Fig. 2 is a side sectional view of the same continuous underground wall, and Fig. 3 is a tensioned state. 4 is a side sectional view showing the same tension state, and FIG. 5 is a front sectional view showing the sheath 3,
Diagram showing the arrangement of PC steel material 4 and grout 8, No. 6
The figure shows an example of the bearing plate used in the embodiment of the present invention, and Figure 7 shows the bearing plate constructed according to the embodiment of the present invention.
A side cross-sectional view of the lower part of the PC wall, Figure 8 is a cross-sectional stress diagram of the RC wall, and Figure 9 is a cross-sectional stress diagram of the PC wall. 1...Ground, 2...Groove, 3...Sheath, 4...
PC steel material, 5... Representation of sheath 3 and PC steel material 4 as one body, 6... Bearing plate, 7... Rebar cage, 8
... grout, 9 ... exhaust pipe, 10 ... underwater concrete, 11 ... grid reinforcement, 12 ... slime removal hole, 13 ... tightening fittings, 14 ... tensioning jack, 15 ... PC steel material mounting part , 16...corn.

Claims (1)

[Scope of Claims] 1. A reinforcing bar cage and a depth-wise prestressing steel material with a bearing plate at the lower end are installed in a trench made in the ground, and then concrete is poured and the concrete is hardened to a predetermined strength. A method for constructing a continuous underground wall that introduces prestress in the depth direction, which is characterized by tensioning the post-prestressing steel material. 2. In a trench prepared in the ground, install a prestressing steel material in the depth direction, which has a reinforcing bar cage and a bearing plate at the lower end, and is fitted with a sheath equipped with an exhaust pipe, and then concrete is poured, A method for constructing a continuous underground wall that introduces prestress in the depth direction, which comprises tensioning the PC steel material after the concrete has hardened to a predetermined strength, and then injecting grout into the sheath.