JP7258696B2 - Injection method of suspension injection material - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Public Interest Incorporated Association Japan Society of Civil Engineers 2019 74th Annual Academic Lecture DVD-ROM of the 2019 Japan Society of Civil Engineers National Convention published on August 7, 2019

TECHNICAL FIELD The present invention relates to a method for pouring a suspension grout into the ground to improve the ground.

Among chemical injection methods for ground improvement, for example, a suspension injection material injection method that uses a suspension injection material containing suspended particles such as cement particles is known.
In the injection method of the suspension type injection material, the injection pipe is drilled into the ground to a predetermined depth, and after the penetration, the suspension type injection material is injected into the ground through the injection pipe. When the injection of the suspension type injection material is completed, the injection tube is pulled out by a predetermined length, and the suspension type injection material is injected into the ground again. By injecting this suspension-type grouting material several times while pulling out the grouting pipe, a compaction improvement body is formed in the ground, and the ground is improved. In this injection method of suspension injection material, injection of suspension injection material into the ground is generally performed by double-pipe double packer injection method, double-pipe rod single-phase injection method, double-pipe It is performed by the rod multi-phase injection method, the single tube rod injection method, and the like.

It is necessary to consider the permeability to the ground for the suspension grout used in the grouting method of the suspension grout. Therefore, a groutability ratio GR (Groutability Ratio) is used as an index for determining whether or not the suspension-type grouting material penetrates into the ground. The groutability ratio GR is the ratio of the 85% grain size G ₈₅ of the grain size accumulation curve of the suspension injection material and the 15% grain size D ₁₅ of the grain size accumulation curve of the ground to be improved, GR = _D15 / _G85 .
Conventionally, suspension-type grouting materials having a groutability ratio GR of greater than 24 have been used in consideration of permeability into the ground.

However, in the suspension grouting method, even when a suspension grouting material having a groutability ratio GR greater than 24 is used, the suspension grouting material has poor permeability to the ground. In some cases, it may not be possible to reliably inject the suspension-type injection material into the ground, and as a result, there is a problem that a compaction improvement body having a desired size cannot be created in the ground.

The present invention has been made in view of such problems, and an object of the present invention is to provide a method for pouring a suspension grout into the ground with certainty. , to make it possible to create a consolidated improvement body of a desired size in the ground.

The present inventors have conducted intensive research in order to ensure that the suspension injection material can be injected into the ground in the injection method of the suspension injection material. Regarding the permeability of grouting materials, it was found that not only the groutability ratio GR, which has been used conventionally, but also the hydraulic conductivity of the ground has an effect. Therefore, the present inventors conducted experiments on the effects of the groutability ratio GR and the hydraulic conductivity of the ground on the permeability of the suspension grout, and completed the grouting method of the suspension grout of the present invention. came to.

That is, the present invention is a suspension grouting material injection method for improving the ground by injecting the suspension grouting material into the ground, wherein the ground to be improved has a hydraulic conductivity of 10 ⁻⁶ m / s or more. In the case of 3.00×10 ⁻⁴ m/s or less, a suspension-type grouting material having a groutability ratio of more than 40 is used to inject into the ground to improve the ground, and the hydraulic conductivity of the ground is 3.0. 00 × 10 ^-4 m / s and 10 ^-1 m / s or less, the groutability ratio is injected into the ground using a suspension type grouting material with a value greater than 24 , and the suspension type The injection pressure of the injection material into the ground is 50 kPa or more and 280 kPa or less .

According to the present invention, by using a suspension type grouting material having a different groutability ratio value according to the hydraulic conductivity of the ground to be improved, the suspension type grouting material is reliably injected into the ground. As a result, it is possible to create a consolidated improvement body of a desired size in the ground.

It is a figure which shows the ground improvement apparatus used with the grouting method of the suspension type grouting material of this invention. FIG. 2A shows a state in which the injection pipe is penetrated, FIG. 2B shows a state in which the injection pipe has penetrated to a predetermined depth, and FIG. 2C shows a suspension injection material injected into the ground. It is a figure which shows the state which is. FIG. 3A is a diagram showing a state in which the suspension injection material is injected into the ground after the injection tube is pulled out a little, and FIG. 3B is a diagram showing a state in which the suspension injection material is injected multiple times. and FIG. 3C is a diagram showing a state in which a consolidated improvement body is created in the ground.

One embodiment of the injection method of the suspension type injection material of the present invention will be described with reference to the drawings.
The injection method of the suspension type injection material according to the present embodiment (hereinafter simply referred to as the injection method of the suspension type injection material) involves penetrating the injection pipe into the ground, and releasing the suspension type injection material from the injected injection pipe. The soil is improved by injecting it into the ground to form a consolidated improvement body in the ground, and in the suspension type injection material to be injected into the ground, a predetermined suspension type injection material is used.

FIG. 1 is a diagram showing a ground improvement device used in the injection method of this suspension-type grouting material.
The ground improvement device 1 used in the injection method of this suspension type injection material, for example, as shown in the figure, comprises a construction machine 2 installed on the ground surface, and the construction machine 2 is equipped with an injection pipe 3 that penetrates into the ground. . As a result, the construction machine 2 penetrates the injection pipe 3 into the ground or pulls it out from the ground. The injection pipe 3 is a hollow steel pipe through which the suspension injection material passes, and a plurality of discharge ports 4 for injecting the suspension injection material into the ground are provided at the lower part thereof. In addition, the soil improvement device 1 includes an injection material supply device 5 near the construction machine 2, and the injection material supply device 5 includes a material storage unit 6, an injection material generation unit 7, a pressure feed pump 8, and a flow rate/pressure gauge 9. and so on. In the injectable material supply device 5 , the injectable material producing unit 7 produces a suspended injectable material, and the produced suspended injectable material is pressure-fed to the injecting pipe 3 via the flow rate/pressure gauge 9 by the pressure-feeding pump 8 .

FIG. 2A shows a state in which the injection pipe is penetrated, FIG. 2B shows a state in which the injection pipe has penetrated to a predetermined depth, and FIG. 2C shows a suspension injection material injected into the ground. It is a figure which shows the state which is. FIG. 3A is a diagram showing a state in which the suspension injection material is injected into the ground after the injection tube is pulled out a little, and FIG. 3B is a diagram showing a state in which the suspension injection material is injected multiple times. and FIG. 3C is a diagram showing a state in which a consolidated improvement body is created in the ground.

As shown in FIG. 2A, the injection pipe 3 is penetrated into the ground while drilling the injection pipe 3 into the ground with the construction machine 2, and as shown in FIG. Penetrate the tube 3 . After the penetration, as shown in FIG. 2C, the suspension injection material S is injected into the ground by applying pressure from the discharge port 4 of the injection pipe 3 . When the injection of the suspension-type grouting material S into the ground is completed, the construction machine 2 pulls out the grouting pipe 3 by a predetermined length. After pulling out, as shown in FIG. 3A, the suspension injection material S is again pressurized from the discharge port 4 of the injection pipe 3 and injected into the ground. As shown in FIG. 3B, the suspension-type injection material S is injected into the ground a plurality of times while pulling out the injection pipe 3 . As a result, as shown in FIG. 3C, a consolidated improvement body T can be formed in the ground. A plurality of consolidation improved bodies T are constructed at predetermined intervals in the ground of the site to be improved.

In this suspension injection material injection method, a predetermined suspension injection material S is used in the suspension injection material S to be injected into the ground.
That is, when the hydraulic conductivity K of the ground to be improved is 10 ^-6 m / s (meters per second) or more and 3.00 × 10 ^-4 m / s (meters per second) or less, the groutability in the injection material supply device 5 A suspension-type injection material S having a GR ratio greater than 40 is produced, and this suspension-type injection material S is used. That is, a suspended grouting material S having a groutability ratio GR greater than 40 is supplied to the grouting pipe 3 and injected into the ground through the grouting pipe 3 .

In addition, when the hydraulic conductivity K of the ground to be improved is greater than 3.00 × 10 ^-4 m / s (meters per second) and 10 ^-1 m / s (meters per second) or less, the grauterbi in the grouting material supply device 5 A suspension-type injection material S having a value greater than 24 is produced, and this suspension-type injection material S is used. That is, the suspension type grouting material S having a groutability ratio GR greater than 24 is supplied to the grouting pipe 3 and injected into the ground through the grouting pipe 3 .

As described above, the suspension-type grouting material S to be injected into the ground has different groutability ratios GR depending on the hydraulic conductivity K of the ground to be improved.
As described above, the groutability ratio GR is the ratio of the 85% grain size G ₈₅ of the grain size accumulation curve of the suspension grout S and the 15% grain size D ₁₅ of the grain size accumulation curve of the ground to be improved. and represented by the formula GR=D ₁₅ /G ₈₅ .

The hydraulic conductivity K of the ground expresses the water permeability in the ground, that is, the speed at which water moves in the ground. The coefficient of permeability K of the ground is obtained by performing an on-site permeability test (in-situ permeability test) to directly determine the coefficient of permeability K in the ground at the site, or by reproducing the soil collected at the site indoors (compacting it to the same density as the site). It can be easily determined by an indoor permeability test or the like.

Regarding the hydraulic conductivity K of the ground here, the lower limit is set to 10 ⁻⁶ m/s and the upper limit is set to 10 ⁻¹ m/s.
That is, if the hydraulic conductivity K of the ground is smaller than the lower limit of 10 ⁻⁶ m/s, the water moves very slowly, that is, the ground is practically impermeable, in which water hardly moves. Therefore, in such ground, the ground is not improved by the injection method of the suspension-type grouting material. Also, if the hydraulic conductivity K of the ground is larger than the upper limit of 10 ⁻¹ m/s, the speed of water movement is extremely high, which is impossible in normal ground, that is, it is a special ground. Therefore, in such ground, the ground is not improved by the injection method of the suspension-type grouting material. Therefore, the lower limit value and the upper limit value are set as described above.

The suspension-type injection material S contains suspended particles such as cement particles, and the cement particles are, for example, fine particle cement, ultrafine particle cement, or ultrafine particle cement. The fine particle cement has an average particle size of about 8 μm, the ultrafine particle cement has an average particle size of about 4 μm, and the ultrafine particle cement has an average particle size of about 1.5 μm. As a result, the suspension-type injection material S contains fine particle cement, ultra-fine particle cement, or ultra-ultra-fine particle cement as cement particles (suspension particles), thereby increasing the permeability of the suspension-type injection material S into the ground. .
The suspension type injection material S contains cement particles such as fine particle cement, ultrafine particle cement, or ultrafine particle cement, but is not limited to this, and other cement particles, or other cement particles such as slag and bentonite. It may contain suspended particles.

Further, when the suspension-type injection material S is injected into the ground, the injection pressure varies depending on the water permeability of the ground. Therefore, in the ground with good water permeability, the suspension-type grouting material may be injected into the ground at a low injection pressure of, for example, 50 kPa to 100 kPa, and in the ground with poor water permeability, for example, 300 kPa to 500 kPa. In some cases, the suspension-type grouting material is injected into the ground at a high injection pressure of .

(Experimental example)
Next, in order to confirm the effect of this suspension grouting method in the grouting method, an experiment was conducted on the effects of the groutability ratio GR and ground hydraulic conductivity K on the permeability of the suspension grouting material S. So let's talk about this.
In the experiment, a plurality of experimental grounds with different soil hydraulic conductivity K were prepared, and a plurality of suspension grout materials S with different groutability ratios GR were injected into each experimental ground. The permeability of the suspension-type injection material S into the ground was investigated.

That is, Ube silica sand or Namegata mountain sand alone or mixed is placed in each cylindrical container and compacted to a predetermined density to prepare a plurality of experimental grounds. The total length of the cylindrical container is 60 cm. Also, a plurality of suspension injection materials S having different groutability ratios GR are prepared. Suspension-type injection material is suspended particles of ultrafine particle cement with an average particle size of about 4 μm, ultra-ultrafine particle cement with an average particle size of about 1.5 μm, or slag-based injection material with an average particle size of about 2.4 μm. It contains.

A plurality of suspension grouting materials S having different groutability ratios GR were injected into a plurality of test grounds prepared, and the permeation distance (reaching distance) of the injected suspension grouting materials S was measured.

The results are shown in Table 1 below.
In Table 1, the vertical axis represents the permeation distance of the suspension injection material S, and the horizontal axis represents the groutability ratio GR.

As shown in Table 1, when the groutability ratio GR was large, the permeation distance was 60 cm, that is, the suspension injection material S reached the end of the cylindrical container (total length 60 cm). Here, it is assumed that the suspension type injection material S having a penetration distance of 60 cm has a permeability of 100%. In the table, ◯ indicates that the permeability is 100%. In addition, although the permeation distance did not reach 60 cm, there were some that reached 50 cm. The suspension injection material S with a penetration distance of 50 cm has a permeability of 83.333%, that is, 80% or more. In the table, Δ indicates that the permeability is 80% or more. If the permeability of the suspension-type grouting material S is 80% or more, it has good permeability into the ground, and can be reliably injected into the ground.

In addition, even with the suspension-type grouting material S, which has a groutability ratio GR greater than 24, which was conventionally thought to have good permeability to the ground, the permeation distance is 30 cm or less, that is, the cylindrical container (total length 60 cm) There were some that did not reach even half of the The suspension injection material S with a permeation distance of 30 cm or less has a permeability of 50% or less. In the table, those with a permeability of 50% or less are indicated by x. If the permeability of the suspension-type grouting material S is 50% or less, the permeability to the ground is poor, and it cannot be reliably injected into the ground.

Next, the effects of the ground hydraulic conductivity K and the groutability ratio GR on the permeability of the suspension grout S into the ground were examined.
That is, the hydraulic conductivity K of each ground was obtained when the permeation distance of the suspension-type injection material S in Table 1 was measured, and the relationship between the groutability ratio GR and the hydraulic conductivity K of the ground was investigated.

The results are shown in Table 2 below.
In Table 2, the vertical axis represents the groutability ratio GR, and the horizontal axis represents the hydraulic conductivity K of the ground in a logarithmic scale. In the table, as in Table 1, when the penetration distance of the suspension injection material S was measured, ◯ indicates 100% permeability, △ indicates 80% or more permeability, and △ indicates permeability. is 50% or less is indicated by x.

As shown in Table 2, even in the suspension-type grouting material S with a groutability ratio GR greater than 24, there were those with a permeability of 50% or less (x shown in Table 2), but permeation All of the soils with a hardness of 50% or less have a hydraulic conductivity K of 3.00×10 ⁻⁴ m/s or less and a groutability ratio GR of 40 or less.
From the above, the groutability ratio GR at which the suspension-type grouting material S can be reliably injected into the ground, with the hydraulic conductivity K of the ground being 3.00×10 ⁻⁴ m/s as a boundary, is It turned out to be wrong.

That is, in order to ensure the injection of the suspension-type grouting material S into the ground, when the permeability coefficient K of the ground is 3.00×10 ⁻⁴ m/s or less, the groutability ratio GR is Suspended injection material S having a value greater than 40 may be used, and when the hydraulic conductivity K of the ground is greater than 3.00 × 10 ^-4 m / s, the groutability ratio GR is a value greater than 24 A suspension-type injection material S that becomes
As described above, it was confirmed that the groutability ratio GR and the hydraulic conductivity K of the ground are related to each other and affect the permeability of the suspension grout S.

Moreover, in this experiment, the pressure (injection pressure) when injecting the suspension-type grouting material S into the experimental ground was between 50 and 300 kPa.
As a result, when the injection pressure was 50 to 250 kPa, the suspension type injection material S could be injected as prescribed. Further, when the injection pressure was set to 300 kPa, splitting fracture occurred in the ground into which the suspension type injection material S was injected, and the suspension type injection material S could not be injected well. In this case, there was no cracking failure in the ground, and the suspension type grouting material S could be injected as prescribed.
From this, it was found that the injection pressure of the suspension-type injection material into the ground should be 50 kPa or more and 280 kPa or less.

As described above, according to the injection method of the suspension type injection material, when the hydraulic conductivity of the ground to be improved is 10 ^-6 m / s or more and 3.00 × 10 ^-4 m / s or less, glautabi When using a suspension type grouting material S with a value greater than 40 and the hydraulic conductivity of the ground to be improved is greater than 3.00 × 10 ^-4 m / s and 10 ^-1 m / s or less, By using the suspension type grouting material S with a groutability ratio greater than 24, it is possible to reliably inject the suspension type grouting material S into the ground. A narrow consolidation improvement T can be created in the ground.

In addition, in the injection construction method of the suspension type injection material, the injection of the suspension type injection material S into the ground can be performed by various methods. For example, a single pipe rod injection method in which a single pipe is used as the injection pipe 3 and the suspension type injection material S is injected into the ground from the discharge port 4 of the injection pipe 3, and a double pipe is used as the injection pipe 3. Then, the injection material flows separately inside the injection pipe 3, joins just before the discharge port 4, and is injected into the ground from the discharge port 4. A double pipe rod multi-phase injection method in which two types of injection materials are separately flowed inside the injection pipe 3 using pipes and separately injected into the ground from the discharge port 4 like primary injection and secondary injection. can be done with
In addition, using an injection pipe 3 consisting of an outer pipe and an inner pipe fitted with upper and lower packers inserted into the outer pipe, the suspension type injection material S is injected into the ground while preventing liquid leakage by the upper and lower packers. A double tube double packer injection method for injection can also be performed. Injection of the suspension-type grouting material S into the ground is not limited to this.

DESCRIPTION OF SYMBOLS 1... Soil improvement apparatus, 2... Construction machine, 3... Injection pipe, 4... Discharge port, 5... Injection material supply apparatus, 6... Material storage part, 7... Injection material production|generation part, 8... Pumping pump, 9... Flow rate - Pressure gauge.

Claims (2)

A suspension injection material injection method for improving the ground by injecting a suspension injection material into the ground,
If the hydraulic conductivity of the ground to be improved is 10 ^-6 m/s or more and 3.00 × 10 ^-4 m/s or less, the ground is ground using a suspension type injection material that has a groutability ratio greater than 40. If the hydraulic conductivity of the ground to be injected into and improved is greater than 3.00 × 10 ^-4 m / s and 10 ^-1 m / s or less, the groutability ratio will be a value greater than 24 Suspension injection A method of injecting a suspension type injection material, characterized in that the injection pressure of the suspension type injection material into the ground is 50 kPa or more and 280 kPa or less . In the injection method of the suspension type injection material according to claim 1,
A method of injecting a suspension injection material, wherein the suspended particles contained in the suspension injection material are fine particle cement, ultrafine particle cement, or ultrafine particle cement.

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