JPH04111807A - Bottom stabilization work - Google Patents

Abstract

PURPOSE:To reduce the thickness of improved ground by a method in which the soil of excavated pit bottom is mixed with an improving agent having a greater specific gravity than the soil before mixing. CONSTITUTION:A sheathing wall W is constructed, and the ground G under the bottom B is improved by a deep-layer mixing treatment machine 2. The ground G on which a structure is to be constructed is excavated by using a backhoe 1 to form a pit. In this case, An improving agent such as iron sand- mortar mixture having a greater specific gravity than soil under the bottom B is used. The ground stabilization work can thus be attained even in city area and the thickness of improved ground can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is particularly applicable to bottom surface stabilization, which stabilizes the bottom surface when roots are cut in soft ground or ground with high water pressure (such as the bottom surface at great depths). It is related to chemical construction methods.

[Background Art] When constructing a building, root cutting is performed, that is, soil below the ground level is excavated to create a required space in order to construct the foundation. However, the pressure of groundwater in soft ground or, for example, in deep excavation (underground in an impermeable aquifer), where the water head is higher than the upper boundary surface of the aquifer at that location. ) or on high ground, heaving (the bottom surface bulges and breaks due to upward lifting force) is more likely to occur. Therefore, the following methods have been developed to prevent heaving.

■Water level lowering method This method uses a drainage device such as a deep well to drain groundwater and reduce overburden pressure.

Zero-gravity balance construction method This construction method uses the weight of the improved ground itself to resist uplift pressure.

[Problems to be Solved by the Invention] However, the above-mentioned prior art has the following problems.

■The problem with the water level lowering method was that it could not be used in urban areas where there are restrictions on pumping groundwater.

■'The heavy coverage method had a problem in that it required an improvement thickness (thickness of the improved ground) that was approximately the same as the excavation depth.

The present invention has been made in view of such problems,
The object is to provide a bottom stabilization method which can be used even in urban areas and which allows the improvement thickness to be reduced compared to the prior art.

Means for Solving Problem 1 The gist of the present invention is a bottom surface stabilization method that stabilizes the bottom surface by mixing earth and sand under the bottom surface of an excavation hole constructed by root cutting with an improvement material. The bottom surface stabilization method is characterized in that the improving material has a higher specific gravity than the earth and sand before mixing.

[Function] Since it does not pump up groundwater, it can be used in urban areas.

The material having a higher specific gravity than the earth and sand under the bottom surface makes the thickness of the improved ground thinner than when using materials with a low specific gravity such as cement or lime as in the prior art.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this example are intended to limit the scope of this invention to only those, unless otherwise specified. It's not, it's just an illustrative example.

Regarding the equipment used in the bottom surface stabilization method according to this example, the second
This will be explained using figures.

In the figure, numeral 1 is a backhoe that excavates the ground G on which a building is to be constructed, numeral 2 is a deep mixing machine that improves the ground, and numeral 3 is a mortar plant installed near the deep mixing machine 2. . The deep mixing device 2 mixes and stirs the improvement material made of mortar and iron sand with the earth and sand under the bottom surface.

The mortar plant 3 mixes cement, water, and iron sand to make an improved material, and sends the improved material to the deep mixing treatment machine 2. It is connected to the mixing processor 2.

In addition, in the figure, numeral 6 is a cement silo that sends cement to the mortar plant 3, numeral 7 is a water tank, numeral 8 is a submersible pump that sends water from the water tank to the mortar plant 3, and numeral 9 is a power source for the mortar plant 3. This is a power generator.

Next, the bottom surface stabilization method according to this embodiment will be explained using FIGS. 1(a) to 1(c).

First, as shown in FIG. 1(a), an earth retaining wall W is constructed using a construction method suitable for carrying out the present invention, such as a continuous underground wall construction method.

Next, as shown in FIG. 1(B), the ground G below the bottom surface B is improved from a predetermined depth using the deep mixing device 2.

Next, as shown in FIG. 1(C), the backhoe 1 is used to excavate the ground G on which the structure is to be constructed, and the excavated hole H is constructed.

Through the above steps, the bottom surface B is stabilized and the excavated hole H is constructed.

Next, the effects of the bottom surface stabilization method configured as described above will be explained.

It does not pump up groundwater, but only mixes and stirs the improvement material and the earth and sand under the bottom surface S, so it can be used in urban areas.

In addition, since the soil improved by the improvement material, which is a mixture of iron sand and mortar, has a higher specific gravity than the earth and sand under the bottom surface B, the improved soil has a higher specific gravity than the soil improved by the improvement material, which is a mixture of iron sand and mortar. Make it thinner. For example, as shown in FIG. 3, if the specific gravity of the improved soil I according to this embodiment is twice the specific gravity of the improved soil I in the conventional technology, the thickness of the improved soil I will be 172 times. It is.

In addition, in this example, the ground G below the bottom surface B was improved by the deep mixing method, but this is not intended to limit the scope of the present invention, and the present invention does not intend to limit the scope of the present invention to this method. The present invention can be applied to suitable construction methods such as the high-pressure jet mixing method, 100% soil improvement method (DEMICloo), and other deep mixing methods. When the 100% ground improvement method is used, the ground G below the bottom surface B can be improved without leaving any unimproved parts. Furthermore, when the high-pressure jet injection mixing treatment method is used, the cutting ability of the injection rod is improved, so the improved diameter can be increased compared to the prior art even at the same pressure.

Furthermore, although a mixture of mortar and iron sand was used as the improving material, this is not intended to limit the scope of the present invention, and in the present invention other materials, such as only iron sand, or a mixture of iron sand and lime or cement, may be used. , any suitable material can be used to carry out the present invention.

Further, although iron sand is used as a material having a higher specific gravity than the earth and sand under the bottom surface B, this is not intended to limit the scope of the present invention, and the present invention does not intend to limit the scope of the present invention. Any suitable method can be used to implement the method.

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

Because it does not pump up groundwater and uses water that has a higher specific gravity than the soil beneath the bottom, it can be used in urban areas, and the thickness of the improved ground can be made thinner than with conventional technology.

As a result, according to the present invention, underground structures can be constructed on soft ground or at great depths in urban areas. Furthermore, since the thickness of the improved ground can be reduced, the period required for improvement can be shortened and costs can be reduced.

[Brief explanation of the drawing]

Figures 1 (a) to 3 show one embodiment of the present invention, and Figures 1 (a) to 1 (c) are process diagrams, and Figure 2 is equipment related to the bottom surface stabilization method. FIG. 3 is a front view showing the operation of the embodiment. G...Ground, ■...Improved ground, W...
-Earth retaining wall, B...bottom, H...excavation hole, 2. Deep mixing machine, 3...mortar plant.

Claims (1)

[Claims] A bottom stabilization method that stabilizes the bottom surface of an excavated hole constructed by cutting roots by mixing the bottom surface with an improvement material, the improvement material being more stable than the earth and sand before being mixed. A bottom stabilization method characterized by having a high specific gravity.