JPS60208514A - Construction work of underground wall - Google Patents

Abstract

PURPOSE:To increase economical effects for the constrution of an underground wall by a method in which a main wall is formed by laying tension members between a temporary sheathing wall and the main wall, and after hardening the main wall, the tension members are tensed to introduce a prestress into both of the walls in such a way as to reduce the thickness of the wall. CONSTITUTION:Concrete is placed into a vertical trench to form a temporary sheathing wall 10, and after the concrete headens, the inside of the sheathing wall 10 is excavated. The excess portion 14a of tension members 14 buried in the wall 10 is pulled out, and a main wall 12 is formed in such a way as to position the excess portion 14a within the main wall 12. After the main wall 12 is hardened, the tension members 14 are tensed to introduce a prestress into the walls 10 and 12. The eccentric distance can thus be made greater, and the effects of prestress in the main wall 12 can be increased. The ecomonical effects can be obtained because the thickness of the wall can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION As is well known, when constructing an underground structure or a shaft for shield construction, a temporary retaining wall is constructed prior to the formation of a permanent wall.

This temporary earth retaining wall is necessary to prevent the collapse of the ground against the surrounding soil and water pressure during excavation work to form the permanent wall.

However, this is only a temporary structure until the permanent wall is constructed.

Therefore, the temporary earth retaining wall should be as thin as possible.

Being able to withstand water pressure is desirable from an economic standpoint.

For this reason, for example, as seen in Japanese Patent Publication No. 45-5225, we also provide a construction method that makes it possible to reduce the wall thickness by burying prestressed steel materials in the earth retaining wall and introducing prestress into the wall. has been done.

However, with the construction method disclosed in the publication, although the wall thickness of the temporary earth retaining wall can be reduced, the wall thickness of the permanent wall cannot be reduced.

On the other hand, underground structures, such as subways built in cities,
Due to the complexity of underground structures, they tend to be built in progressively deeper locations. For this reason, the soil of the earth.

In order to withstand water pressure, temporary earth retaining walls and permanent walls tend to have thicker walls.

Therefore, it may be possible to ensure economic efficiency by using a temporary earth retaining wall as part of the permanent wall.

However, if a permanent wall is simply formed on the inner surface of a temporary earth retaining wall, the integrity between the two will be weak, and the expected economic effect will not be obtained.

This invention was made in view of the above-mentioned background, and its purpose is to reduce the eccentric distance by making the tension material span both the temporary earth retaining wall and the permanent wall. Therefore, it is an object of the present invention to provide a construction method for an underground wall that can further increase the effect of prestress commonly introduced between both walls and reduce the wall thickness of both walls.

In order to achieve the above object, the present invention provides a construction method in which a temporary earth retaining wall is formed underground, the inside of the wall is excavated, and a permanent wall is formed along the inner surface of the temporary earth retaining wall. An extra length is provided in advance inside the temporary earth retaining wall so that tension material for introducing prestress can be placed inside the permanent wall, and this extra length is located at the inner edge of the temporary earth retaining wall. , and when forming the permanent wall, expose the extra length, and form the permanent wall so that the tension material straddles both the temporary earth retaining wall and the permanent wall, The structure is characterized in that after the main hall wall has hardened, the tension material is tensioned to introduce prestress into the temporary earth retaining wall and the permanent wall.

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

FIG. 1 shows a first embodiment of the underground wall construction method according to the present invention.

In the construction method shown in the figure, a narrow vertical trench is excavated from the ground surface, and concrete is poured into this vertical trench to create a temporary earth retaining structure.
10 is formed, and after this concrete has hardened, the inside of the temporary earth retaining wall 10 is excavated and the actual installation is done! form 12.

Here, inside the temporary earth retaining wall 10, as shown in FIG.
As shown in >, the tension material 14 is attached to a reinforcing bar cage or the like in advance and buried therein.

The tension member 14 is made of a flexible sheath and a steel material inserted into the sheath, and is provided with spirally formed extra length portions 14a at appropriate locations. As shown in FIG. 1(C), it is disposed within the main wall 12.

Further, the extra length portion 14a is located at the inner edge of the temporary earth retaining wall 10, that is, on the side where the permanent wall 12 is formed. .

Then, when the temporary earth retaining wall 10 is formed and the inside thereof is excavated to a predetermined depth, when forming the permanent wall 12,
The location where the extra length portion 14a is buried is shown in Figure 1 (
b), remove it to expose it, and pull out the extra length 14a.

In this case, since the extra length portion 14a is located at the inner edge of the temporary earth retaining wall 10, it can be easily pulled out.゛After that, as shown in Fig. 1(C), the extra length portion 14a is
is positioned within the permanent wall 12 to form this, the tension material 14 becomes the temporary earth retaining rJ! 1o, it comes to straddle both sides of the main wall 12.

Next, when the tendons 14 are tensioned after the permanent wall 12 has hardened, a common prestress is introduced into the temporary earth retaining wall 10 and the permanent wall 12.

Now, when constructing an underground wall using the construction method described above, the tension material 14
is arranged so as to straddle both the temporary earth retaining wall 10 and the permanent wall 12, and the eccentric distance 20 can be increased, further increasing the effect of the prestress commonly introduced between both walls. It is possible to reduce the thickness of these walls.

FIG. 2 shows a second embodiment of this invention, and only its features will be described below.

That is, the tension material 14 buried in the main wall 12 is made up of a cylindrical sheath 'I4b and the steel material 1 inserted into the inside thereof.
4c and C1 sheath 14b is generally flexible as in the above embodiment.

The extra length portion 14a of the tendon 14 is installed in the temporary earth retaining wall 10 in a substantially trapezoidal shape (see Fig. 2(a).
), the upper side of which is located at the inner edge of the retaining wall]0.

When forming and reeling the main wall 12, the extra length portion 14a is exposed as shown in FIG. is pulled out to a predetermined length, the covering material 16 is attached to this part, and the permanent wall 12 is attached as shown in FIG. 2(C).
buried within.

Even in such a construction method, the same effects as in the first embodiment can be obtained, and even if the wall thickness of the permanent wall 12 becomes large, the extra length 14a buried in the temporary earth retaining wall 10 can be
By adjusting , the wall thicknesses of the temporary earth retaining wall 10 and the permanent wall 12 can be reduced.

FIG. 3 shows a third embodiment of the present invention, and only its features will be described below.

In this embodiment, the tendons 14 are made of steel, and the extra length 14a buried in the main wall 12 is
4 is divided into approximately trapezoidal shapes so that their ends overlap, and each end is the upper side of the trapezoid and is positioned at the inner edge of the temporary earth retaining wall 10 (see Fig. 3). a
)reference). The extra length portion 14a is shown in FIG. 3(b).
After exposing as shown in FIG. 3(C), the vicinity of the ends are crossed and buried in the main wall 12, and each end protrudes from the inner surface of the main wall 12, as shown in FIG. 3(C). As shown, the anchor 18 is attached and tensioned.

Even when an underground wall is constructed using such a method, the same effects as those of the above embodiment can be obtained, and the following effects can also be achieved.

That is, since the soil water pressure applied to underground walls increases in the depth direction, the wall thickness must generally be increased as the depth increases.

At this time, in this embodiment, the tension material 14 is divided in the depth direction, so that the tension force of the tension material 14 can be increased as it goes downward.

Therefore, by appropriately selecting the magnitude of prestress and applying tension,
Even if an underground wall is formed, it can withstand earth water pressure without increasing the wall thickness very much.

As described above in detail in the embodiments, according to the underground wall construction method according to the present invention, the eccentric distance is increased by making the tendons straddle both the temporary earth retaining wall and the permanent wall. As a result, the effect of the prestress commonly introduced between both walls can be further increased, the thickness of these walls can be reduced, and extremely large economic effects can be obtained.
Saves on strands and labor compared to placing strands on both walls separately.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing the process order of a first embodiment of the present invention, FIG. 2 is a sectional view of a main part of a second embodiment of the invention without showing the process order, and FIG. FIG. 7 is a cross-sectional view of main parts showing the process order of the third embodiment. 10...Temporary earth retaining wall 12...Permanent wall 14...Tension material 14a...Extra length portion 14b
... Sheath 14c ... Steel material 16 ... Covering material 18 ... Fixture 20 ... Eccentric distance Patent applicant Obayashi Co., Ltd. Agent Patent attorney -Kensuke Shiro (Q) Figure 1

Claims (4)

[Claims] (1) Form a temporary earth retaining wall underground and excavate the inside of the child.
In a construction method in which a permanent wall is formed along the inner surface of the temporary earth retaining wall, an extra length is provided inside the temporary earth retaining wall so that tension material for introducing prestress can be placed in the permanent wall in advance. and the extra length is buried so that it is located at the inner edge of the temporary earth retaining wall, and when the permanent wall is formed, the extra length is exposed, and the tension material is placed on the inner edge of the temporary earth retaining wall. The permanent wall is formed so as to straddle both the temporary earth retaining wall and the permanent wall, and after the permanent wall has hardened, the tension material is tensioned to introduce prestress into the temporary earth retaining wall and the permanent wall. A construction method for underground walls that is characterized by the following: (2) The above-mentioned tension material is composed of a visible sheath and a steel material inserted inside the sheath, and the above-mentioned extra length part is formed in a spiral shape, and this part is pulled out and buried in the above-mentioned permanent wall. An underground wall construction method according to claim 1, characterized in that: (3) The tension member consists of a cylindrical sheath and a steel material inserted into the sheath, and the extra length is buried in the temporary earth retaining wall in a substantially trapezoidal shape, and the extra length is exposed. After that, the sheath is cut and the steel wire is pulled out, and this part is covered and buried in the main wall. Construction method. (4) The tension material is composed of a visible sheath and a steel material inserted into the sheath. The present invention relates to construction of an underground wall according to claim 1, characterized in that the end portion of the material projects from the inner surface of the main wall and serves as a fixing portion for the tension material. Regarding the construction method,
In particular, it relates to construction methods for underground walls that introduce prestress into both temporary earth retaining walls and permanent walls.