JP2000303465A - Method for retaining earth by low strength underground wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earth retaining method by a low strength underground wall capable of maintaining self-standing of the underground wall even when at least a shore struts out of supports are eliminated in the case when the low strength underground wall such as a low priced soil cement column wall or the like is adopted. SOLUTION: After an underground wall 10 composed of a soil cement column strip is constructed in the peripheral ground of a planned site to make underground excavation, reinforced concrete underground buttresses 12 are constructed across the soil cement underground wall 10 at specific pitch intervals. Then, when a walling 17 supporting the wall surface of the underground wall is constructed while excavating the ground of the area surrounded by the underground wall 10, the walling 17 is supported with an underground space projected position of the underground buttresses 12 as an achor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a retaining method using a low-strength underground wall such as a soil cement column wall.

[0002]

2. Description of the Related Art For example, Japanese Patent Publication No. 5-11166 discloses a digging method using an underground wall made of soil cement as a digging wall in an underground excavation work. In this mountain retaining method, a soil cement column in which a solidifying agent such as cement milk is injected and solidified into the stirred portion while stirring the ground in a column shape using a multiaxial auger or the like is used as an underground wall. It is a method of excavating the inside of this, and has an advantage that it is cheaper than a ridge wall construction method using a general reinforced concrete ground wall.

[0003]

However, because the strength of the column of soil cement is lower than that of reinforced concrete, in large-scale construction, as shown in FIG. When excavating an underground space, it is necessary to support the exposed side wall surface of the underground wall wall 1 by a support so as to oppose the earth pressure of the surrounding ground E. The support includes an upright 2 arranged along the surface of the underground wall 1, a cutting beam 3 orthogonally disposed between the uplifting 2 and the It is composed of fire struts 4 that are slanted between them. All of them are made of steel and must be arranged at pitch intervals according to the strength of the underground wall 1. Therefore, many materials are required, and as a whole, Has a disadvantage that the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an inexpensive soil cement column wall or other low-strength underground wall, and to use at least a cut beam of a support structure. The present invention is to provide a retaining wall construction method using a low-strength underground wall, which can maintain the independence of the underground wall even when omission is performed.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for constructing a low-strength underground wall in a ground around a planned underground excavation site, and then forming the low-strength underground wall at predetermined pitch intervals. Build an underground buttress made of reinforced concrete across
Next, in erection of the erection supporting the wall surface of the underground wall while digging the ground in the area surrounded by the underground wall, supporting the erection using the underground space protruding position of the underground buttress as an anchor. It is characterized by the following. Therefore, according to the method of the present invention, it is possible to reduce the amount of steel material to be used without disposing a cutting beam for the self-supporting of the low-strength underground wall.

Further, in the present invention, a joint recess is formed in advance on the side of the underground buttress where the underground space protrudes, and an embedded reinforcing bar is protruded in the recess so that the underground buttress can be used when constructing a permanent underground outer wall. In this case, the joint of the underground buttress and the permanent underground outer wall is connected via the reinforcing bar, thereby simplifying the processing of the joint.

Further, in the present invention, a notch is formed on the side of the underground buttress protruding from the underground space at a position corresponding to the end of the prong, and the protruding end is formed in the notch. By embedding, the length of the underground buttress projecting into the underground space can be shortened.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Figure 1
FIG. 4 shows a construction procedure according to the method of the present invention.

First, as shown in FIG. 1, an underground wall 10 composed of a column of soil cement is constructed in a ground E. The underground wall 10 is agitated in a columnar manner in the ground E by a multi-axis auger excavator, and then withdrawn from the ground E while injecting cement milk.
Is completed by the hardening of the cement milk.

[0010] In the underground buttress construction planned position which crosses the underground wall 10 indicated by the broken line in the figure, the underground wall 10 is formed continuously and partially spaced apart from each other without being continuously constructed. . Although only one side of the underground wall 10 is illustrated in the figure, the underground wall 10 is formed around the entire shape of the underground space to be excavated.

Next, as shown in FIG. 2, an underground buttress 12 is constructed in the ground E. The method of constructing this underground buttress 12 is similar to a general underground wall construction method, in which a trench wall is constructed by an excavator while using a bentonite muddy water to prevent collapse of the excavation trench wall, and a reinforcing cage is built. This is done by replacing the muddy water with concrete by the tremy pipe method. The construction pitch interval of the underground buttress 12 is set in accordance with the strength of the soil cement underground wall 10 and is set in accordance with the design of the main underground structure in order to form a part of the frame of the main underground structure. You.

Also, as shown in an enlarged view in a part of the figure, a JOF iron plate 1 having a concave cross section is provided on both side surfaces of the protruding portion of the underground space of each underground buttress 12 in advance for joining with a permanent underground outer wall.
4 (see Japanese Patent Publication No. 47-34334) are integrated in an exposed state, and a pair of jointing reinforcing bars 15a extending to the side of the reinforcing bar cage 15 protrude from the inside thereof. Further, on both sides of the distal end position of the underground buttress 12, fired beam receiving concave portions 16 are formed in advance.

After the above construction work, as shown in FIG.
At the same time as excavating the internal underground space surrounded by the underground wall 10, the installation work of the shoring is performed in parallel. The shoring according to the present invention is performed only by the combination of the bulge 17 arranged on the inner wall surface of the underground wall 10 and the blow beam 18 supporting the bulge 17, and the conventionally used cutting beam is omitted. You. That is, the other end side of the striking beam 18 is supported by the recess 16 at a projecting portion in the space of the underground buttress 12.

In this supporting position, as shown in an enlarged view of a part of the drawing, a pair of anchor bolts 19 protruding inside the concave portion 16 are passed through end flanges 18a of the striking beam 18, and the flanges of the anchor bolts 19 are formed. By screwing the nut 20 into the protruding end from 18a, the striking beam 18 is fixed.

As described above, the bulge 17 is fixed to the side surface of the underground wall 10 with a sufficient supporting force to oppose the earth pressure, so that the underground wall 10 can be retained even if the cut beam is omitted. As a result, the independence can be sufficiently maintained.

After excavation of the underground space, as shown in FIG. 4, a post-strike body outer wall concrete 21 is cast and integrated with the underground buttress 12. At this time, as shown in an enlarged view in a part of the figure, by connecting the joint reinforcing bar 15a to the reinforcing bar on the side of the outer wall concrete 21 at the position of the JOF iron plate 14, the connection of the reinforcing bars at the joint position of both members is achieved. It can be done easily.

In the above description, the case in which the fire strut is used as the support member of the belly is described. However, the fire strut is not provided, and the end of the belly is provided in the notch provided in the side surface of the underground buttress. You may make it fit and support it.

FIG. 5 and FIG. 6 show this state. FIG. 5 shows a state immediately before the concrete is placed in the underground buttress 12, and the filling 12 a and the steel 1 attached to the reinforcing bar 12 c are shown.
2b is installed. FIG. 6 shows that after the buttress concrete has hardened, the padding 12a has been removed and a bulge 17 has been embedded in its trace. The steel material 12b buried at the edge of the notch 12a 'functions to prevent the edge from collapsing. The belly 17 may be a steel material or a precast concrete member. It is also possible to integrate the outer wall concrete without removing the bulging 17.

In the above description, the soil cement underground wall has been described, but the present invention is applicable to other low strength underground walls. Another example of a low-strength underground wall is to construct the underground wall by excavating (removing earth and sand) rather than agitating the ground, and by solidifying muddy water or self-hardening stabilizer in the borehole. There is a middle wall.

[0020]

As is apparent from the above description, according to the method of retaining by the low-strength underground wall according to the present invention, when a low-strength underground wall such as an inexpensive soil cement column wall is employed, Even if at least the cut beam of the shoring is omitted, the independence of the underground wall can be maintained, and the amount of steel used for the shoring can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view showing a construction state of a soil cement underground wall as an example of a low strength underground wall.

FIG. 2 is an explanatory plan view showing a construction state of an underground buttress.

FIG. 3 is an explanatory plan view showing an excavation of an underground space and an installation state of a shoring.

FIG. 4 is an explanatory plan view showing a joint state between an underground buttress and a permanent underground outer wall.

FIG. 5 is an explanatory plan view showing a state immediately before concrete casting in another joint state between the underground buttress and the permanent underground outer wall.

FIG. 6 is an explanatory plan view showing a state in which a belly is embedded in another state of joining the underground buttress and the permanent underground outer wall.

FIG. 7 is an explanatory plan view showing a conventional shoring method using a soil cement underground wall.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Soil cement underground wall (low-strength underground wall) 12 Underground buttress 12a 'Notch 17 Upset 18 Fire strut 14 JOF iron plate (concave) 15a Reinforcing bar 21 Body outer wall concrete

Claims (3)

[Claims] 1. A low-strength underground wall is constructed in the ground surrounding a planned underground excavation site, and then a reinforced concrete underground buttress is constructed across the low-strength underground wall at a predetermined pitch interval;
Next, in erection of the erection supporting the wall surface of the underground wall while digging the ground in the area surrounded by the underground wall, supporting the erection with the underground space protruding position of the underground buttress as an anchor. A method of retaining by a low-strength underground wall. 2. A joint recess is formed in advance on the side of the underground space where the underground buttress protrudes, and an embedded reinforcing bar is protruded in the recess. 2. The method according to claim 1, wherein the joint between the underground buttress and the outer wall of the permanent underground is connected via a base. 3. A notch is formed at a position corresponding to an end of the protruding portion of the underground buttress on a side of a protruding position of an underground space, and the protruding end is embedded in the notch. The method according to claim 1 or 2, wherein the method comprises the steps of: