JPH083986A - Foundation structure of underground structure - Google Patents

Abstract

PURPOSE:To use a temporary foundation of a conventional inverted support as a permanent foundation so that a sufficient pull-out resistance, which can overcome buoyant forces, is given to the foundation. CONSTITUTION:In a foundation structure of an' underground structure wherein concrete floor slabs 2 are constructed in multilayers successively from above by an inverted construction method while the ground surrounded by an earth retaining wall 1 is being excavated and the slabs 2 are supported by a plurality of temporary inverted support 4, a foundation is constructed as a permanent foundation 10 by excavating the ground under a location where an inverted support 4 is installed. At first, a hole is excavated to a depth deeper than a predetermined depth of construction of a bottom plate 3. And the deepest section of the hole is formed into a trapezoidal shape. After completion of excavation work, concrete is placed to a predetermined depth for the plate 3, so that the permanent foundation 10 wherein a trapezoidal bottom portion 10a is integral with the lower part of the foundation is constructed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground structure constructed by a reverse construction method, and more particularly to a solid foundation structure of an underground structure having sufficient resistance to buoyancy applied to the underground structure. It is a thing.

[0002]

2. Description of the Related Art In the reverse construction method, floor slab concrete for the main structure is constructed sequentially from the top along with root cutting, and this is used as a support work to support the mountain retaining wall and work sequentially on the lower part. It is an excellent construction method and safety, especially when constructing underground structures with deep underground.

FIG. 3 shows a conventional underground structure constructed by the upside down construction method. In the interior surrounded by a mountain retaining wall 1, a floor slab in which beams 2a are vertically and horizontally integrated in order from the top to the bottom. Concrete 2 is constructed in multiple stages, and bottom plate 3 is at the deepest part.
Is being built.

Each slab concrete 2 is supported by a large number of temporary upright columns 4 built in the ground in the vertical direction in advance. In addition, the lower end of the upright strut 4 is integrated with the temporary foundation 5 made of concrete, etc.
The supporting strength of the counter strut 4 is obtained.

[0005]

In the underground structure having the above structure, when the volume scale is large and the groundwater level is high, the water pressure P always acts upward and a huge buoyancy acts. Therefore, conventionally, a large number of permanent anchors 6 are driven into the lower portion of the bottom slab 3 to form a pull-out resistor, or concrete 7 is additionally struck in the hollow portion above the bottom slab 3 to increase the weight and counteract buoyancy. .

However, the former requires a large number of construction steps and the latter requires a large amount of concrete, which requires a long construction period and is uneconomical in terms of construction cost and materials.

The present invention has been made in order to solve the above problems, and its purpose is to use a temporary foundation of a conventional counter strut as a foundation for main construction, and to pull out sufficient buoyancy against the foundation. It provides a foundation structure for underground structures designed to provide resistance.

[0008]

In order to achieve the above-mentioned object, the present invention constructs a slab concrete in a multi-step manner from top to bottom by excavating the ground surrounded by a mountain retaining wall, and In an underground structure in which floor slab concrete is supported by a plurality of temporary upright columns, in order to increase pullout resistance to overcome buoyancy,
It is characterized in that the main foundation of the inverted strut is deeply formed and the bottom of the foundation is expanded.

[0009]

[Operation] According to the above construction, the permanent foundation is formed deep and the bottom of the foundation is expanded according to the number of the temporary upright columns to be built, and the anchor effect of this portion forms an underground structure. Sufficient pull-out resistance is obtained against the buoyancy acting.

Further, since it is possible to secure a large supporting strength of the reverse strut, the supporting strength of the reverse strut until the bottom slab is completed becomes sufficient.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the entire structure of an underground structure having a multilayer structure according to the present invention. In the figure, the same parts as those in the related art are designated by the same reference numerals, and different parts are denoted by different reference numerals.

That is, in this embodiment, the mountain retaining wall 1
In the interior surrounded by, the floor slab concrete 2 in which the beams 2a are vertically and horizontally integrated in order from the top is constructed in a multi-tiered manner by using the upright strut 4, and the concrete slab 3 is constructed in the deepest part. There is.

Each slab concrete 2 is supported by a large number of temporary upright columns 4 built in the ground in the vertical direction in advance. Further, the lower part of each of the reverse strut columns 4 is integrated with the permanent foundation 10 according to the present invention, whereby
The supporting strength of the counter strut 4 is obtained.
The upper part of the main foundation 10 is integrated with the bottom plate 3.

Next, the construction procedure will be described with reference to FIG. First of all, the holes for constructing the pillars will be excavated from the ground surface, but at this time, while pouring a stabilizing solution such as bentonite so that the holes do not collapse, excavate with an earth drill etc. To go. Further, in the present invention, as shown in FIG. 2A, the excavation hole 12 is dug down to a depth deeper than the planned construction depth D of the bottom slab 3, and then the deepest part of the excavation hole 12 is expanded into a trapezoidal shape. To do. As a method of forming the expanded bottom portion 10a, for example, a bucket 100 having a special shape disclosed in Japanese Patent Publication No. 3-71527 is adopted. As shown in an enlarged view in a part of FIG. 2A, the bucket 100 has a feature that the maximum width of the open position is larger than the maximum width of the closed position, and a hole is first drilled to a planned depth. After that, the trapezoidal expanded bottom portion 10a is formed by scraping off the excavated wall surface at the deepest portion with the maximum width of the open position.

After the excavation work is completed, as shown in FIG. 2 (b), a reverse strut (steel frame) 4 is erected from the ground surface so that an appropriate depth of rooting can be obtained in the concrete. ,
Next, by pouring concrete to the planned construction depth D of the bottom slab 3, the permanent foundation 10 in which the trapezoidal expanded bottom portion 10a is integrated at the bottom is constructed. And
The permanent foundation 10 is constructed to a depth sufficiently deeper than that of a conventional temporary foundation, and in combination with an increase in the area and weight of the expanded bottom portion 10a, the supporting strength of the reverse strut 4 is further increased. It also has a function to make it.

After that, while excavating the inside surrounded by the mountain retaining wall 1, the floor slab concrete 2 is constructed in multiple stages from the top,
By constructing the bottom slab 3 at the deepest part as shown in FIG. 2C, the permanent foundation 10 is integrated with the bottom slab 3.

When the buoyancy force due to the water pressure P acts on the underground structure having the above structure, the frictional force of the shaft portion of each permanent foundation 10 and
The expanded bottom portion 10a serves as an anchor to generate sufficient pull-out resistance to overcome buoyancy, and an underground structure can be fixed in the ground without requiring a permanent anchor or additional concrete.

[0018]

As described above in detail with reference to the embodiments, in the substructure of the underground structure according to the present invention,
Depending on the number of reverse strut columns built, the permanent foundation is deep and the bottom of the foundation is expanded, and the anchor effect of this part provides sufficient pull-out resistance against buoyancy acting on underground structures. Since it can be obtained, the underground structure can be fixed in the ground without the construction of permanent anchors or the placing of additional concrete as in the past, and the construction period can be shortened, the construction cost can be saved, and the waste of materials can be omitted.

Further, by increasing the bottom expanding area and increasing the weight of the permanent foundation, it is possible to secure a large supporting strength of the upright strut, and it is possible to obtain sufficient supporting strength of the upright strut until the bottom slab is completed. There is also.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall structure of an underground structure according to the present invention.

2A to 2C are partial cross-sectional explanatory views showing a procedure for constructing a foundation.

FIG. 3 is a cross-sectional view showing the overall structure of a conventional underground structure.

[Explanation of symbols]

 1 Yamadome wall 2 Floor slab concrete 3 Concrete bottom slab 4 Reverse strut 10 Main installation foundation 10a Expanded part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Tsuji 2-3 Chome, Kandajimachi, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Head Office

Claims (1)

[Claims] 1. While excavating the ground surrounded by a mountain retaining wall, the floor slab concrete is constructed in multiple stages in order from the top by the reverse piling method, and the floor slab concrete is supported by a plurality of temporary reverse piling columns. In order to increase pull-out resistance to overcome buoyancy,
A foundation structure for an underground structure, characterized in that the main foundation of the above-mentioned inverted strut is deeply formed and the bottom portion of the foundation is expanded.