JPH0874244A - Underground foundation construction process - Google Patents

Abstract

PURPOSE: To construct an underground foundation which does not sink even in a soft ground where there is no supporting foundation bed in the relatively shallow part of the ground. CONSTITUTION: When an underground foundation Z is constructed in the ground G where a foundation for a building must be installed, specified amounts of lightweight beads 6 having extremely low specific gravity, a solidifying material 7, and water 8 are mixed to produce a solidifying material-slurry containing lightweightbeads having a lower specific gravity than that of the soil of the ground G. Then, a suitable amount of the solidifying material-slurry containing lightweight beads is supplied into and mixed with the soil of the ground G to construct an underground foundation Z made of soil cement containing beads. Thus, the underground foundation Z which does not sink even in a soft ground where there is no supporting foundation bed in the shallow part of the ground, can be constructed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction method for constructing an underground foundation in the ground where a structure is constructed, and is particularly suitable for the ground of soft soil (for example, clay soil) such as a wetland. It relates to the underground foundation construction method.

[0002]

2. Description of the Related Art Conventionally, as an example of a construction method for an underground foundation, there is a wrapping method shown in FIG. This wrapping method is suitable when there is a supporting base in a relatively shallow portion, and the ground G on which the foundation 10 of the building 9 is constructed.
Is excavated and soiled, a mold is assembled in the void S, and then fresh concrete is filled in the mold to construct the wrapping concrete X.

By the way, the specific gravity of the ground G on which the building is constructed is about 1.5 to 1.8 (t / m ³ ), and the specific gravity of the wrapping concrete X is about 2 to 2.4 (t / m ³ ). in this way,
Since the specific gravity of the laple concrete X shown in FIG. 4 is larger than the specific gravity of the surrounding ground G, especially in the ground G where the soft soil (such as clay soil) such as a wetland continues to a large depth, The ground foundation X sinks into the ground due to the weight and the weight of the structure 9 built on it. Therefore, the ground foundation made of the wrapping concrete X is suitable for the case where the supporting base is located in a relatively shallow portion, but cannot be used for the ground where soft soil continues to a large depth.

Further, as a ground foundation construction method for soft ground, there is a soil cement column method as shown in FIG. In this soil cement column method, an excavator having a vertically long rotating shaft is used, and after excavating to a predetermined large depth with a supporting base on the rotating shaft, the solidified material mixed slurry is sequentially discharged from the lower end head of the rotating shaft and By vertically pulling up the rotary shaft while stirring, a vertically long columnar pile (underground foundation) Y made of soil cement is constructed. Such column-shaped piles Y are respectively formed at locations where the foundation 10 of the building 9 is installed (a large number of locations are required at predetermined intervals). In that case, mechanical equipment such as an excavator is sequentially moved while moving each time. It is necessary to form the column pile Y. In many cases, the foundation 10 of the building 9 is placed across a plurality of (for example, four) columnar piles Y, Y ...

[0005]

However, when constructing an underground foundation in soft ground, in the soil cement column method shown in FIG. 5, it is necessary to excavate the ground G to a large depth with a supporting base ( Sometimes, it may be necessary to excavate more than 50 m), and mechanical equipment such as excavation equipment for that purpose becomes large, and the equipment cost becomes expensive,
Further, there is a problem that the work is complicated and takes a long time (the work is prolonged) to sequentially move and install the large-scale mechanical device to the installation location of the building foundation 10. In the ground foundation constructed by the laple method shown in FIG. 4, since the laple concrete X is constructed only to a relatively shallow depth, the construction method is relatively easy. Is an unsuitable construction method.

The present invention is cheaper than the conventional soil cement column method described above and can shorten the construction period. On the other hand, the present invention can improve the problem of subsidence of the ground foundation as compared with the conventional laple method. The purpose of this project was to propose a construction method for the underground foundation.

[0007]

The method for constructing an underground foundation of the present invention is to construct an underground foundation in a relatively shallow portion of the ground where soft soil continues to a relatively large depth such as a wetland. This method is suitable for construction and has the following means.

[0008] That is, the construction method of the present invention, when constructing an underground foundation in the ground where the foundation of the building is installed,
Lightweight beads with a very small specific gravity, solidifying material (cement) and water are mixed by a predetermined amount respectively to generate a lightweight beaded solidifying material slurry having a specific gravity smaller than the specific gravity of the soil in the ground, in the soil of the ground. The solidifying material slurry containing lightweight beads is mixed in an appropriate amount to construct an underground foundation using soil cement containing lightweight beads. Thus, the underground foundation construction method of the present invention, by constructing the underground foundation with lightweight beaded soil cement, so that the specific gravity of the constructed underground foundation can be made smaller than the specific gravity of the surrounding ground soil. The basic configuration is to.

Further, in the construction method of the present invention, if the weight of the building is relatively light, the underground foundation may be constructed only in a partial area where the foundation of the building is installed. In terms of bearing capacity, it is preferable to construct the underground foundation in a planar shape over the entire floor area of the building.

As the lightweight beads used in the present invention, for example, beads made of expanded polystyrene and having an extremely lightweight specific gravity of about 0.01 (g / cm ³ ) are used. Then, the light weight beads, the solidifying material (cement), and water are accommodated in the mixer in predetermined amounts, respectively, and the light weight beads-containing solidifying material slurry is generated by stirring them at high speed in the mixer.
Further, the mixing ratio of the materials of the lightweight beads containing solidified material in the slurry is ground foundation 1 m ³ per, for example lightweight beads 0.2
34m ³ (weight 2.34Kg), solidifying material 0.024m ³ (weight 73Kg), water 58l (weight 58Kg) for slurry formation are suitable.
In this case, the specific gravity of the solidifying material slurry containing lightweight beads is about 0.42 (t / m ³ ), and the specific gravity of the ground soil is 1.5 to 1.8 (t / m ³ ).
It is much smaller than m ³ ).

The underground foundation construction work by mixing the solidification material slurry containing light beads with soil is carried out by injecting and stirring the solidification material slurry containing light beads into the soil while excavating the ground soil with an excavator. Or excavate and remove the soil of the underground foundation construction part, stir and mix the soil and the solidifying material slurry containing lightweight beads on the ground, and then backfill the soil-solidifying material mixed slurry. It may be performed by. Further, in the construction method of the present invention, since the ground foundation is constructed in a relatively shallow area of the ground, a relatively simple excavator such as a backhoe can be used as an excavator for excavating soil in the ground.

[0012] The mixing ratio of the lightweight beads into the underground foundation to be constructed depends on the geology of the ground, the weight of the structure to be constructed above, the structure (area / depth) of the underground foundation to be constructed, etc. Adjust the specific gravity of the underground foundation to meet the construction conditions. That is, by adjusting the specific gravity of the ground foundation, the total weight per unit area of the building and the ground foundation is set so as not to exceed the allowable ground strength of the ground. For example, the allowable ground bearing capacity of the ground is 3.5 (t / m ² ),
When the weight (including foundation) per unit area is 2.6 (t / m ² ), the underground foundation has a specific gravity of 1.1 (t / m ³ ) and a thickness of 8
It may be constructed so as to be 0 cm. In this case, the total load applied to the ground per unit area (total load of the building and the ground foundation) is 2.6 + 0.88 = 3.48 (t / m ² ), and the allowable ground strength of the above ground is 3.5 (t / m ^2). ) It becomes smaller and the subsidence phenomenon of the underground foundation does not occur. The specific gravity of the underground foundation is 1.1 (t /
To adjust the m ^3), to the soil 0.409M ³ (weight 695.3Kg), lightweight beads containing solidifying material slurry 0.316M ³ of the specific gravity 0.42 (t / m ³⁾ (weight 133.34Kg), adjusting water 275 l (weight 27
5 kg) and each (total volume is 1 m ³ and total weight is about 1.1 t). Note that these mixing ratios are merely examples, and it goes without saying that the mixing ratios can be changed according to various construction conditions.

[0013]

As described above, in the underground foundation construction method of the present invention,
Since the solidification material slurry with lightweight beads with a small specific gravity is mixed in the soil of the ground to construct an underground foundation made of soil cement with lightweight beads, the specific gravity of the constructed underground foundation is It is smaller than the specific gravity of the soil. Therefore, even when constructing an underground foundation and a building on soft ground (for example, clay soil) where there is no supporting foundation in a relatively shallow part, the unit area of the underground foundation and the structure above it. If the total weight per hit is within the allowable ground strength of the ground, the ground foundation will not sink.

Further, according to the construction method of the present invention, the specific gravity of the underground foundation can be reduced. Therefore, when the scale (weight) of the building is relatively small, even if the ground is soft, the underground foundation is in a relatively shallow range. It will be possible to build only on. Therefore, large-scale underground foundation work unlike the conventional soil cement column method is unnecessary.

[0015]

According to the underground foundation construction method of the present invention, it is possible to construct an underground foundation having a specific gravity smaller than the specific gravity of the soil of the soil in the ground, so that the soil foundation is soft and the underground foundation is relatively shallow. Even if it is constructed only in the range, if the total weight of the ground foundation and the building per unit area is within the allowable ground bearing capacity of the ground, the ground foundation and the building can be built without problems ( (Underground foundation does not sink). Therefore, there is an effect that even if the ground is soft, it can be handled with an underground foundation in a relatively shallow range, and the construction period can be shortened at low cost as compared with the conventional soil cement column construction method.

[0016]

EXAMPLE An example of the present invention will be explained with reference to FIGS. 1 to 3. In this example, the ground foundation Z is constructed in a planar shape over the entire floor area of the building 9. The medium foundation construction method is shown. This underground foundation construction method is a method suitable for constructing a comparatively lightweight building 9 (for example, a steel-framed three-story house) on soft ground without a supporting base such as clay soil. , Furthermore, the ground foundation Z is 0.
It is suitable for building in a relatively shallow area of about 5 to 3 m.

In the ground foundation construction method of this embodiment, as shown in FIG.
And the function of excavating the soil of the ground G as shown in FIG.
(Bucket 2), a function of injecting the lightweight bead-containing solidifying material slurry into the soil excavation portion (slurry injecting device 3), and a function of stirring and mixing the excavated soil and the injected light-weight beading solidifying material slurry (agitating device It is convenient to use the excavator 1 equipped with 4) and 4) respectively.

In this embodiment, a backhoe as shown in FIG. 1 is used as the excavator 1. This excavator 1
In a self-propelled vehicle body 11, a bending arm 12 is horizontally rotatably mounted, and a bucket 2 for excavating soil is attached to a tip portion of the bending arm 12.

The bucket 2 portion is provided with a nozzle 34 (see FIG. 2) of the slurry injecting device 3 for discharging the solidifying material slurry containing light beads into the excavated soil. As shown in FIG. 1, the solidified material slurry containing the light beads produced in the mixer 31 is pumped into the nozzle 34 by the nozzle 34.
2 through the supply pipe 33.

The bucket 2 portion is provided with a stirring device 4 for stirring and mixing the soil excavated in the bucket 2 and the solidifying material slurry containing light beads discharged from the nozzle 34. As shown in FIG. 2, the stirring device 4 has a configuration in which a stirring blade 42 is rotated by a hydraulic motor 41 incorporated in the bucket 2.

The lightweight beads 6 used in this underground foundation construction method are, for example, polystyrene beads and have a specific gravity of 0.
An extremely light weight of about 01 (g / cm ³ ) is used. Then, as shown in FIG. 1, light-weight beads 6, solidifying material (cement) 7 and water 8 are contained in a predetermined amount in a mixer 31, respectively, and are stirred at high speed in the mixer 31 to solidify with light beads. A material slurry can be produced.

The mixing ratio of each material in the solidifying material slurry containing the light beads is 1 m ^{3 of the} ground foundation to be constructed,
For example, lightweight beads 6 are 0.234m ³ (weight 2.34Kg), solidifying material 7
0.024m ³ (weight 73kg), 58l of water 8 for slurry generation
(Weight 58Kg), appropriate degree. In this case, the specific gravity of the solidifying material slurry containing light beads is about 0.42 (t / m ³ ), which is significantly lighter than the specific gravity of the ground soil of 1.5 to 1.8 (t / m ³ ).

In this embodiment, the ground foundation construction work by mixing the solidification material slurry containing light beads with soil is carried out while excavating the soil of the ground G with the excavator 1 and the solidification material slurry containing light weight beads in the soil. It is performed by pouring and stirring.

Lightweight beads 6 into the ground foundation Z to be constructed
The mixing ratio of is adjusted according to the geology of the ground G, the weight of the building 9 (including the foundation 10) constructed above, the structure (area / depth) of the underground foundation Z constructed, Adjust the specific gravity of the ground foundation Z to meet the construction conditions. That is, by adjusting the specific gravity of the underground foundation Z (adjusting the mixing ratio of the lightweight beads 6), the total weight per unit area of the building 9 and the underground foundation Z is the allowable ground strength of the ground G. Set not to exceed. For example, the allowable ground bearing capacity of the ground is 3.5
(t / m ² ), when the weight per unit area of the building 9 (including the foundation 10) is 2.6 (t / m ² ), the underground foundation Z has a specific gravity of 1.1 (t / m ³ ). It may be constructed so that the thickness is 80 cm. In this case, the total load applied to the ground G per unit area (the total load of the building 9 including the foundation 10 and the underground foundation Z)
Is 2.6 + 0.88 = 3.48 (t / m ² ), which is less than the allowable ground bearing capacity of 3.5 (t / m ² ) of the ground G, and the subsidence phenomenon of the ground foundation Z does not occur. In addition, the specific gravity of the underground foundation Z is 1.1 (t /
To adjust the m ^3), to the soil 0.409M ³ (weight 695.3Kg), lightweight beads containing solidifying material slurry 0.316M ³ of the specific gravity 0.42 (t / m ³⁾ (weight 133.34Kg), adjusting water 275 l (weight 27
5 kg) and each (total volume is 1 m ³ and total weight is about 1.1 t). Note that these mixing ratios are merely examples, and it goes without saying that the mixing ratios can be changed according to various construction conditions.

In the underground foundation construction method of this embodiment, the above-mentioned excavator 1 is used to form a planar underground foundation Z as shown in FIG.
First, the excavator 1 is moved to the underground foundation construction position, and the bending arm 12 and the bucket 2 are operated there to excavate the soil of the ground G. Further, as shown in FIG. 2, at the same time as the soil excavation work by the bucket 2 (at this time, an appropriate amount of adjusted water is supplied), the solidification material slurry containing the light beads produced in the mixer 31 is pumped from the nozzle 34 by the pump 32. At the same time as discharging, the soil and the solidifying material slurry containing lightweight beads are mixed and stirred by the stirring device 4. At this time, the soil mixed with the solidifying material slurry containing the lightweight beads becomes sludge-like, and the bucket 2 can move up and down and front and back and left and right in the sludge-like mixed soil with some resistance. Then, while performing the injection work and the mixing / stirring work of the solidified material slurry containing the lightweight beads, the bending arm 12 and the vehicle body 11 are operated to sequentially move the bucket 2 up and down and front and back and left and right. By doing so, for example, as shown in FIG. 3, a planar ground foundation Z made of lightweight cement containing beads is constructed.
In this embodiment, the underground foundation Z has an area corresponding to the total floor area of the building 9 to be built. And
After the underground foundation Z is hardened, as shown in FIG. 3, an appropriate number of foundations 10, 10 ... (may be a planar foundation having the same area as the bottom surface of the building 9) on the underground foundation Z. And the building 9 such as a building may be built on it.

As described above, in the underground foundation construction method of this embodiment, the soil of the present ground is excavated by the simple excavator 1,
Moreover, since the soil of the underground foundation building portion can be successively improved while mixing the excavated soil and the solidifying material slurry containing lightweight beads, it is possible to form the improved soil in the underground foundation building portion simultaneously with the progress of the excavation work. . Therefore, the underground foundation Z can be constructed by a simple mechanical device such as a backhoe, and the construction period can be shortened. Further, when constructing an underground foundation, it is not necessary to excavate and remove soil (or a small amount), so the work and cost for excavating and removing soil are unnecessary (or can be reduced), and Since the soil at present can be used as a constituent material of the underground foundation,
The work cost and material cost can be reduced and the overall construction cost can be reduced.

Further, in this underground foundation construction method, the solidified material slurry containing lightweight beads having a small specific gravity is mixed in the soil of the ground G to construct the underground foundation Z made of soil cement containing lightweight beads. Therefore, the specific gravity of the constructed ground foundation Z (for example, specific gravity 1.1) is smaller than the specific gravity of the surrounding soil (for example, specific gravity 1.5 to 1.8). Therefore, even when the underground foundation Z and the building 9 are constructed on a soft ground where there is no supporting base in a relatively shallow portion, Total weight
(Eg 3.48 t / m ² ) is the allowable ground bearing capacity of the ground (eg 3.50 t / m ² )
If it is within the range of m ² ), the underground foundation Z will not subside, and even the soft ground can be dealt with by the underground foundation Z in a relatively shallow area.

In the above-mentioned embodiment, while excavating the soil in the ground, the excavated soil and the solidifying material slurry containing light beads are mixed on the spot, but in other embodiments,
Underground foundation By excavating and discharging soil in the part where the foundation is built, stirring and mixing the soil and the solidifying material slurry containing lightweight beads on the ground, and then backfilling the soil-solidifying material mixed slurry Z may be constructed.

[Brief description of drawings]

FIG. 1 is a perspective view of an excavator for performing an underground foundation construction method according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a working state of the underground foundation construction method according to the embodiment of the present invention.

FIG. 3 is a sectional view of an underground foundation constructed by an underground foundation construction method according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of an underground foundation formed by a conventional lapping method.

FIG. 5 is a sectional view of an underground foundation manufactured by a conventional soil cement column method.

[Explanation of symbols]

1 is an excavator, 2 is a bucket, 4 is a stirrer, 6 is light beads, 7 is a solidifying material, 8 is water, 31 is a mixer, 34 is a nozzle, and Z is an underground foundation.

Claims (1)

[Claims] 1. Lightweight beads (6) and a solidifying material having an extremely small specific gravity when constructing an underground foundation (Z) in the ground (G) at a place where the foundation (10) of the building (9) is installed. (7) and water
(8) and (8) are mixed with each other in a predetermined amount to generate a solidified material slurry containing lightweight beads having a specific gravity smaller than the specific gravity of the soil of the ground (G), and the lightweight beads are mixed in the soil of the ground (G). An underground foundation construction method, characterized in that a solid foundation slurry (Z) is constructed by mixing an appropriate amount of a slurry of solidifying material to construct a soil foundation containing lightweight beads.