JPH1113049A - Improving method for organic soil ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a universal stabilizer at a relatively low blending ratio by concurrently applying the substitution method to an aggregate and the mixing process method using the normal stabilizer for the soft organic soil ground. SOLUTION: A casing type excavator 3 is installed on a sand mat 2 prepared on the surface of the organic soil ground, the ground soil is excavated and removed, a casing 4 is driven at least to the depth penetrating an organic soil layer 1, and only the excavator 3 is lifted. The casing 4 is driven into the ground 10 deeper by about 50 cm after penetrating the organic soil layer 1, for example. Sea sand or mountain sand 5 serving as an aggregate is inserted into the cavity of the casing 4, the insertion is stopped when the mountain sand 5 is filled in the cavity of the casing 4 nearly to the ground level, then the casing 4 is extracted. The substitution work between the organic soil 1 and the mountain sand 5 is completed for the soft ground at this portion by these processes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a soft ground in which dead leaves, dead branches and the like are deposited and composted, that is, contains a large amount of organic matter, has an extremely high water content, and has a very small amount of aggregate. It belongs to the technical field of soil improvement method to develop the strength of the organic soil where the organic soil layer covers the surface layer considerably deeply by the mixing processing method using stabilizers, and more specifically, the sand replacement method and the mixing processing method. The present invention relates to a soft ground improvement method that is carried out in combination with the above.

[0002]

2. Description of the Related Art Even now, in some areas, there is a soft ground in which organic soil covers a surface layer considerably deeply. As described above, the organic soil layer contains a large amount of organic matter, has an extremely high water content, and has a very small amount of aggregate. As a means for developing strength, even if a soil improvement method by a mixing method using an organic soil cement-based solidifying agent is performed, the strength hardly improves, for example, as shown in the test results of uniaxial compressive strength in FIG. It is known. Incidentally, a dotted line a in FIG. 7 the blending ratio of the organic dog days cement solidifying agent indicates a strength at the age of 7 days at ^{300kg / m 3, 350kg / m} 3, the solid line b is the formulation of the cement solidifying agent The strength at the age of 28 days when the ratio is 300 kg / m ³ and 350 kg / m ³ is shown. In each case, the target strength is 4.34.
kg · f / cm ^2, and 7.23kg · f / cm ² (see FIG. 8) are significantly below. For reference, FIG. 8 shows the test results of the unconfined compressive strength when the viscous ground was improved under the same conditions. The dotted line c in FIG. 8 indicates that the compounding ratio of the ordinary Portland cement-based solidifying agent is 300 kg / m ³ and 350 kg /
The strength at the age of 7 days at m ³ and 400 kg / m ³ is shown. The solid line d shows that the compounding ratio of the cement-based solidifying agent is 300 kg / m ³ ,
And the strength at the age of 28 days at 350 kg / m ³ and 400 kg / m ³ . In each case, the target strength is 4.34.
It is evident that exceeds kg · f / cm ^2, and 7.23kg · f / cm ² significantly.

[0003] The test results shown in FIG. 7 indicate that an expensive cementitious solidifying agent for organic soil (eg, UKC-A manufactured by Ube Industries)
, And FIG. 8 is a result using ordinary Portland cement. Organic soil cement-based solidifying agents are considerably more expensive than ordinary Portland cement. Moreover, FIG. 7 shows a result that even if a cement-based solidifying agent for organic soil is used in a considerably large amount (300 to 400 kg / m ³ ), it is not effective. In short, the results show that it is impossible to consolidate the organic soil with the cement-based solidifying agent to develop the strength.

Therefore, conventionally, in consideration of the above-mentioned situation, when the organic soil layer is relatively shallow (for example, up to a depth of about 2 m), the organic soil layer is scraped off using a bulldozer or the like, Many replacement methods for backfilling soil materials (sand, clay soil, etc.) that exhibit strength by the ground improvement method have been implemented.

[0005]

The conventional replacement method is effective when the organic soil layer is shallow. But 4
When the depth is more than m, the replacement work itself becomes too large, and it is considered difficult to perform the replacement work in terms of the construction period and construction cost. For example, it is difficult to secure backfill soil, and all the organic soil that has been shaved off becomes construction residual soil, which makes disposal difficult.

[0006] Accordingly, an object of the present invention is to replace a soft organic soil ground covered with an organic soil layer with a relatively deep layer with a bone material such as sea sand or mountain sand and to use a usual stabilizer. It is an object of the present invention to provide a soft ground improvement method that is performed in combination with a mixed processing method. A further object of the present invention is to use a general-purpose stabilizer such as inexpensive ordinary Portland cement or blast furnace cement in a relatively small mixing ratio, and to replace the organic soil layer with bone material by volume ratio. It is an object of the present invention to provide a method for improving the organic ground, which can be replaced by about 50%, and the improvement work is easy.

[0007]

According to a first aspect of the present invention, there is provided a method for improving an organic soil layer, wherein the organic soil layer covers a surface layer of the ground. Preparing a support such as a sand mat of sufficient strength to allow construction machinery to be installed on the surface of the ground, installing an excavator on the prepared support, excavating and discharging the soil, Casting to the depth that penetrates the soil layer, charging the bone material into the cavity of the cast casing, then pulling out the casing, and replacing the ground with the bone material as described above And performing an improvement treatment by a mixing treatment method using a stabilizer by a ground improvement machine.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When an organic soil layer 1 according to the first aspect of the present invention covers a surface layer of a ground 10 considerably deeper than 3 m to 4 m or more, first of all, when implementing a method of improving an organic ground, FIG. As shown below, for example, a sand mat 2 is prepared on the surface of the organic ground as a support having a strength capable of installing construction machines. The above-mentioned sand mat 2 is piled up about 1 m in thickness. As described above, the ground surface is soft, and the heavy construction machine is to be installed in a stable operation (operation) state. Therefore, a sheet pile or a steel plate may be spread as a support.

Next, a casing type excavator 3 is installed on the sand mat 2 prepared as described above, and the casing 4 is excavated and discharged from the ground soil and at least the organic soil layer 1 is removed.
And then excavator (excavation shaft 3
Only a) is raised. As the casing type excavator 3, specifically, a chemical pile driving machine, a sand drain construction machine, or the like can be suitably used. Alternatively, it is also possible to install the auger excavator, first excavate and excavate the hole, and then press-fit the casing 4 into the hole.

The casing 4 to be cast as described above.
Is, for example, penetrated through the organic soil layer 1 and is driven into the ground 10 by about 50 cm deeper (see the dotted line in FIG. 1 and FIG. 2). Then, as shown in FIG. 2, sea sand or mountain sand 5 as a bone material is introduced into the cavity of the casing 4.
For example, a concrete bucket 6 which is always provided at a construction site is used and put. The charging is stopped when the cavity in the casing 4 is filled with the mountain sand 5 to approximately the ground level, and then the casing 4 is pulled out (FIG. 3).

Through the above steps, the replacement work of the organic soil 1 and the mountain sand 5 on the soft ground at the site is completed. Hereinafter, similarly, the above-described replacement work is sequentially performed on the ground in the construction area at a constant pitch (FIG. 4). The above replacement may be performed up to about 50%, and therefore does not need to be performed until wrapping. Since the replacement is performed by about 50% as described above, the amount of the removed organic soil generated as construction residual soil is reduced accordingly. As the bone material, in addition to the sand, ordinary soil (including cohesive soil) can be used.

For the soft ground in which the replacement of the organic soil 1 with the bone material 5 has been completed as described above, a ground improvement machine 7, not shown in detail, is also installed on the sand mat 2, and the ground improvement is performed. The known ground improvement treatment is performed to the design depth by the mixing process using the inexpensive ordinary Portland cement-based solidifying agent as a stabilizer. In this case, the ground improvement is performed by lapping as usual, and the compounding ratio of the stabilizer (normal Portland cement-based solidifying agent) that effectively achieves the effect of replacing the bone material is 350.
It is about kg / m ³ .

By the way, sea sand and mountain sand are used as bone materials:
1 was mixed, and this was replaced with 60% by weight of an organic ground, into which an ordinary Portland cement-based solidifying agent having a water-to-cement ratio of 80% was injected at a rate of 350 kg / m ³ and mixed and treated. FIG. 6 shows the test results of the uniaxial compressive strength. According to FIG. 6, the strength at the age of 7 days is 12 kg · f / c.
With m ² , the target strength of 4.34 kg · f / cm ² is sufficiently cleared. The strength at the age of 28 days is 14.25kg.
At f / cm ² , the target strength of 7.23 kg · f / cm ² was also far cleared, and it is clear that the improved method of the present invention can be sufficiently put to practical use.

[0014]

[Effects of the present invention] The improvement method of organic soil according to the present invention is an economical method for improving soft organic soil, which is unsatisfactory in terms of both construction period and economic efficiency with the ordinary replacement method, and has a considerably deep organic soil layer. In addition, it can be easily and efficiently implemented by the combination of the conventional techniques, and the purpose of the ground improvement can be sufficiently achieved.

[Brief description of the drawings]

FIG. 1 is an elevation view showing a stage of excavation and discharge of ground by a casing type excavator as an improved construction method of the present invention.

FIG. 2 is an elevational view showing a stage of charging and replacing bone material into a casing.

FIG. 3 is an elevational view showing a stage of pulling out a casing.

FIG. 4 is a cross-sectional view showing the situation of the ground after the replacement.

FIG. 5 is a construction drawing of ground improvement.

FIG. 6 is a graph showing the results of a uniaxial compression test of ground improved by the method of the present invention.

FIG. 7 is a graph showing the results of a uniaxial compression test of improved ground of organic ground.

FIG. 8 is a graph showing the results of a uniaxial compression test of improved ground of cohesive ground.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic soil layer 2 Sand mat 3 Casing type excavator 4 Casing 3a Excavator 7 Ground improvement machine

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[Procedure amendment]

[Submission date] June 25, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

Continued on the front page (72) Inventor Junji Hori 8-21-1, Ginza, Chuo-ku, Tokyo Co., Ltd. Takenaka Civil Engineering Co., Ltd. (72) Tomohiro Shimamura 4-2-2, Tenjin, Chuo-ku, Fukuoka City, Fukuoka Prefecture Inside Takenaka Civil Engineering Kyushu Branch (72) Inventor Yukio Goto 4-20-20 Tenjin, Chuo-ku, Fukuoka City, Fukuoka Prefecture Inside Takenaka Civil Engineering Kyushu Branch (72) Inventor Katsuyoshi Sugimoto 1-18-18 Nishiki, Naka-ku, Nagoya City, Aichi Prefecture No. 22 Inside Takenaka Civil Engineering Nagoya Branch

Claims (1)

[Claims] 1. A step of preparing a support such as a sand mat having a strength capable of installing construction machinery on a surface of an organic ground in which an organic soil layer covers a surface layer of the ground; Excavator, excavating and discharging the ground soil and placing the casing at least to a depth that penetrates the organic soil layer; charging bone material into the cavity of the placed casing, and then withdrawing the casing And the step of performing an improvement treatment by a mixed treatment method using a stabilizing material by a soil improvement machine on the ground on which the replacement with the bone material has been completed as described above, Construction method.