JP2015113659A - Continuous fiber-reinforced earth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous fiber-reinforced earth method, capable of restraining an increase in soil hardness and a rise of pH to a necessary minimum limit, while improving strength of continuous fiber-reinforced earth, by mixing an additive such as cement with sandy soil.SOLUTION: The additive is added so that uniaxial compression strength of a mixture of the sandy soil and the additive becomes within a range of 30kN/m-150kN/m. Long fiber, for example, polyester fiber is used as continuous fiber. Normal Portland cement, highly-early -strengthening cement, a lime calcium-based solidification material, cement lime, gypsum and magnesium can be applied as the additive.

Description

  The present invention relates to a continuous fiber reinforced earth method for reinforcing various wall surfaces and slopes in a state where continuous fibers (long fibers: for example, polyester fibers) are evenly mixed with sandy soil.

In order to reinforce various wall surfaces and slopes, continuous fiber reinforced soil construction method, in which continuous fiber reinforced soil, in which continuous fibers are evenly mixed with sandy soil, is sprayed onto the object to be reinforced, is used for environmental conservation and reinforcement. Widely used to improve safety.
In such a continuous fiber reinforced earth method, it is considered to add additives such as cement (including ordinary cement, early-strength cement, lime-based cement, etc.) in order to improve the strength of continuous fiber reinforced soil. It is done. If cement or the like is added as an additive, continuous fiber reinforced soil can be used for river revetments where the aggregate sand may be eroded.
However, when an additive such as cement is mixed with continuous fiber reinforced soil, there is a problem that soil hardness increases and pH increases. And when the continuous fiber reinforced soil sprayed is a vegetation base, the increase in soil hardness and the raise of pH will become a factor which inhibits the growth of a plant.

On the other hand, the prior art (refer patent document 1) which increases and uses the addition amount of a solidification material in the range which can be vegetated in the mixture of a long fiber, a solidification material (cement), and soil is also proposed.
However, the related art (Patent Document 1) discloses only the extent to which it is described that the amount of cement as a solidifying material is not an amount exceeding 30 kg per 1 m ^{3 of} soil volume. . And the technique which can suppress the increase in soil hardness and a raise of pH to the required minimum is not disclosed, adding the solidification material (cement) and improving the intensity | strength of continuous fiber reinforced soil.

JP 2009-243225 A

  The present invention has been proposed in view of the above-mentioned problems of the prior art, and increases the soil hardness and pH while improving the strength of continuous fiber reinforced soil by mixing additives such as cement with sandy soil. The purpose is to provide a continuous fiber reinforced earth method that can suppress the increase in the minimum required.

The continuous fiber reinforced earth method of the present invention is a continuous fiber reinforced earth method in which sandy soil and continuous fibers are sprayed, and has a step of mixing an additive with sandy soil, and the additive is a mixture of sandy soil and additive. uniaxial compressive strength of is characterized in that it is added in an amount of within the range of ^{30kN / m 2 ~150kN / m 2} .

In the practice of the present invention, normal Portland cement, early-strength cement, lime, calcium-based solidified material (low alkali calcium-based solidified material), cement lime, gypsum, magnesium and the like can be applied as the additive.
As sandy soil, sand or sand-like material (for example, mountain sand, river sand, sea sand, masa soil, shirasu soil, crushed sand, etc.) can be used, but is not limited thereto.

  In the continuous fiber reinforced earth method of the present invention, continuous fiber reinforced soil (a mixture of sandy soil, continuous fiber, and additive) is sprayed as a vegetation base (on a slope or the like). However, it includes cases where continuous fiber reinforced soil is used for purposes other than vegetation.

  In this invention, it is preferable that the length of the spray hose used for spraying continuous fiber reinforced soil is 60 m or more.

According to the present invention having the above-described configuration, it is possible to increase the reinforcing effect and shear strength of the continuous fiber-reinforced soil without increasing the pH and soil hardness to an extent that adversely affects plant growth.
And according to this invention, since an additive is mixed with sandy soil, it becomes difficult to pull out continuous fiber from sandy soil. Therefore, since the reinforcing effect and shear strength of the continuous fiber are increased, the reliability of the continuous fiber reinforced earth method can be improved.
Furthermore, according to the present invention, since the amount of additive added is defined by the uniaxial compressive strength, which is a highly reliable parameter because it is defined by the Japanese Industrial Standard (JIS), it is accurate and objective even at the construction site. Sandy soil and additives can be adjusted and mixed.

In the present invention, when the continuous fiber reinforced soil is sprayed, if the length of the spray hose is 60 m or more, the sandy soil, the continuous fiber, and the additive are uniformly mixed, and the necessary uniaxial compressive strength (30 kN / m ^2). The above can be expressed.

It is explanatory drawing which shows the outline | summary of the system for enforcing the continuous fiber reinforcement earthwork method. It is a characteristic view which shows the test result of the one-side shear test of the sandy soil which does not include the continuous fiber. It is a characteristic view which shows the test result of the single-sided shear test of the sandy soil containing a continuous fiber. Specimen No. shown in Table 3 2-No. 14 is a characteristic diagram in which 14 uniaxial compressive strengths and adhesive force increase values are plotted. FIG. Specimen No. shown in Table 4 15-No. It is the characteristic view which plotted the uniaxial compressive strength of 31 and soil hardness. It is a characteristic view which shows the characteristic of the spraying hose length and uniaxial compressive strength of continuous fiber reinforcement soil.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 illustrates an overview of a system for carrying out a continuous fiber reinforced earth method.
In FIG. 1, a system 100 for carrying out a continuous fiber reinforced earth method has a sand transport mechanism 8 for transporting sandy soil to a construction area and a continuous fiber supply mechanism 20. Then, the continuous fiber supplied from the continuous fiber supply mechanism 20 (shown by a region surrounded by a one-dot chain line in FIG. 1) is entangled (mixed) with the sand conveyed from the sand conveyance mechanism 8 as continuous fiber reinforced soil. We are constructing.

The sand transport mechanism 8 has a measuring instrument 11 connected to the hopper 10 via a belt conveyor 9a and a sprayer 12 connected to the measuring instrument 11 via a belt conveyor 9b. In FIG. 1, reference numeral 13 denotes a tractor excavator for sand conveyance, and reference numeral 15 denotes a compressor for supplying compressed air to the sprayer 12. A material hose 33 is connected to the sprayer 12, and an injection device for injecting sandy soil (sandy soil mixed with additive) to the tip of the material hose 33 is provided.
Although not clearly shown in FIG. 1, an additive is mixed in the sandy soil filled in the hopper 10. Details of the sandy soil and the additive will be described later.

The continuous fiber supply mechanism 20 includes a continuous fiber supply device 35 that stores the continuous fiber 2 and an ejector 7. The ejector 7 uses the high-pressure water to spray the continuous fiber 2 from the continuous fiber supply device 35. It is comprised so that it may inject from.
The continuous fiber supply device 35 has a plurality of bobbin cases 21 (four in FIG. 1). The bobbin case 21 entangles the continuous fibers 2 from a plurality of (for example, four) bobbins 19 to guide the guide stay 25. It has the function to send out via.
The bobbin case 21 has a load cell 34 and measures the continuous fiber 2.
Here, reference numeral 16 denotes a generator, reference numeral 17 denotes a distribution board, and reference numeral 18 denotes a weighing device.

The continuous fiber 2 fed out from the continuous fiber supply device 35 is injected from the injection nozzle 6 using high-pressure water sent from the water tank 3 through the high-pressure pump 4 through the supply pipe 5.
As described above, from the tip of the material hose 33, sandy soil to which a predetermined amount of additive has been added is sprayed onto the construction surface in the construction area. The continuous fiber 2 is jetted from the jet nozzle 6. As a result, the sandy soil added with a predetermined amount of the additive and the continuous fiber 2 are suitably mixed and laminated in the construction area.

Hereinafter, the sandy soil to which a predetermined amount of additive is added or the continuous fiber reinforced soil used in the illustrated embodiment will be described with reference to the experimental example.
In the system shown in FIG. 1, what is sprayed onto the construction area is a mixture of sandy soil and additive and continuous fibers.
The continuous fiber is, for example, a multifilament non-twisted yarn such as polyester fiber, and is uniformly mixed with the mixture of sandy soil and additive in the construction area.

According to the inventors' experiments, the type of continuous fiber has little effect on the shear strength. Further, it has been confirmed that the mixing ratio (or mixing amount) of continuous fibers has little influence on the shear strength in continuous fiber reinforced soil.
In particular, it has been confirmed that there is no difference in the shear strength measured by the single-sided shear test when the mixing rate of continuous fibers is 0.15% to 0.25% of sandy soil.

Sandy soil in which continuous fibers are uniformly mixed is sand or soil similar to sand. Soil other than sandy soil, such as clay soil, cannot be used for the continuous fiber reinforced earth method.
When soil other than sandy soil, for example, viscous soil, is mixed, it is difficult to spray the construction target region because of its high viscosity. In addition, when soil other than sandy soil (for example, viscous soil) is mixed with continuous fiber reinforced soil, drainage (water permeability) after spraying may deteriorate and the slope may become unstable.

As the sandy soil, those in the range shown in Table 1 below are applicable. In other words, the soil having the properties in the range shown in Table 1 can be used as a sandy soil by a continuous fiber reinforced earth method.
Even sandy soil deviating from the range shown in Table 1 can be used when a one-side shear test is conducted and the adhesive strength (shear strength) is greater than or equal to the design value.
Examples of usable sandy soil (sand or sand-like material) include mountain sand, river sand, sea sand, masa soil, shirasu soil, and crushed sand.
Table 1

As the additive, ordinary Portland cement, early-strength cement, lime, calcium-based solidified material (low alkali calcium-based solidified material), cement lime, gypsum, magnesium and the like are applicable.
Additive is an amount uniaxial compressive strength of the sandy soil after the addition is ^{30kN / m 2 ~150kN / m 2} , is added to the continuous fibers reinforced soil. The uniaxial compressive strength is measured by a method according to Japanese Industrial Standard (JIS) A1216.

Here, the additive is not limited to those described above. Any additive can be used as long as the pH of the sandy soil after addition is less than 11.0 (weak alkaline) and the uniaxial compressive strength is 30 kN / m ^{2 to} 150 kN / m ² or less.
Incidentally, the uniaxial compression strength 30kN ^{/ m 2} ~150kN ^/ m 2 is used measured values at the time of "28 days elapsed". However, the uniaxial compressive strength measured at the time of “elapsed 28 days” may be considered to be synonymous with the “final” uniaxial compressive strength.

The merit of using the mixture of sandy soil and additive used in the system as shown in FIG. 1 for the continuous fiber reinforced soil will be described below.
2 and 3 show a one-side shear test for sandy soil not containing continuous fibers (FIG. 2) and sandy soil containing continuous fibers (continuous fiber reinforced soil) (FIG. 3). The results are shown. Here, in the one-surface shear test, a vertical stress is applied from the up-down direction of the box-shaped specimen, the specimen is sheared on one fixed surface, and the shear strength (kN / m ² ) of the specimen is obtained.

In FIG. 2 and FIG. 3, the plot of “◯” indicates the measurement result of the specimen not added with the additive, and the plot of “■” indicates the measurement result of the specimen added with the additive. .
In the one-side shear test of FIGS. 2 and 3, the additive and the amount of the additive were selected such that the uniaxial compressive strength of the specimen after addition was 50 kN / m ² . And about FIG. 2, there was no significant difference in the result of a one-sided shear test if it was an additive and addition amount with which the uniaxial compressive strength of the specimen after addition was 50 kN / m ² .

As is clear from FIG. 2, in the one-sided shear test using sandy soil that does not include continuous fibers as the specimen, the shear strength (plot “■”) of the specimen added with the additive and the additive were added. There is no significant difference in the shear strength (plot “◯”) of the specimens that are not. That is, as a result of the single-sided shear test shown in FIG. 2, it is clear that in a sandy soil that does not include continuous fibers, the shear strength does not increase significantly even when an additive is added.
On the other hand, as a result of the one-sided shear test shown in FIG. 3, the shear strength (plot “■”) of the specimen to which the additive was added was particularly large in the region where the normal stress was small (the region on the left side in FIG. 3). It was found that the specimen was improved compared to the shear strength (plot “◯”) of the specimen not added.
2 and 3, it was found that the shear strength of the continuous fiber reinforced soil increases when the additive is added so that at least the uniaxial compressive strength after the addition becomes 50 kN / m ² .

Next, how much additive should be added to increase the shear strength of the continuous fiber reinforced soil is examined.
As shown in Table 2 below, the inventor obtained a specimen No. 1 in which an additive was mixed with sandy soil. 1-No. 14 was created. However, the specimen No. No. 1 added no additive. Specimen No. 1-No. 14 does not include continuous fibers.
And the uniaxial compressive strength of each test body, adhesive force, the adhesive force increase value, soil hardness, and pH were measured.
Table 2

Specimen No. 1-No. 14 uniaxial compressive strength, adhesive strength, increased adhesive strength, soil hardness, and pH are as shown in Table 3 below.
In the present specification, the term “adhesive strength” means the shear strength when the normal stress is 0 kN / m ² in the one-side shear test. The “adhesive strength increase value” means the specimen No. 2-No. “Adhesive strength” in each of the specimens Nos. The value (shear strength) increased from the “adhesive strength” in FIG.
Table 3

In the measured values shown in Table 3, in the chart in which the uniaxial compressive strength is on the horizontal axis and the adhesive force increase value is on the vertical axis, the specimen No. 2-No. FIG. 4 is a plot of 14 uniaxial compressive strengths and adhesive strength increase values.
Specimen No. with no additive added. It is clear from FIG. 4 that the adhesive strength (shear strength when the normal stress is 0 kN / m ² in the single-surface shear test) is significantly increased (the adhesive strength increase value is large) compared to 1. Thus, the uniaxial compressive strength is a plot of 30 kN / m ² or more.
In other words, from the results shown in FIG. 4, it was revealed that the uniaxial compressive strength should be 30 kN / m ² or more in order to increase the shear strength significantly by adding the additive.

Next, the upper limit value of the additive amount will be examined.
As shown in Table 4 below, the inventor obtained a specimen No. 1 in which an additive was mixed with sandy soil. 15-No. 31 was created. Specimen No. 15-No. The 31 additive materials, the amount added and the production method are shown in the remarks column of Table 4 below. Here, specimen no. 15-No. 31 does not include continuous fibers.
And the uniaxial compressive strength and soil hardness of each specimen were measured.
Here, soil hardness (mm) is an index of whether or not plants are easy to grow, and is an index of whether or not the roots of plants can enter the soil. In the experiment shown in Table 4 below, the soil hardness is measured using a Yamanaka type soil hardness meter.
Table 4

In the measured values shown in Table 4, in the chart with the uniaxial compressive strength on the horizontal axis and the soil hardness on the vertical axis, the specimen No. 15-No. FIG. 5 is a plot of 31 uniaxial compressive strength and soil hardness.
It is well known to those skilled in the art that in sandy soil, if the soil hardness is greater than 27 mm, plant root growth may be inhibited.
As is apparent from FIG. 5, the uniaxial compressive strength corresponding to a soil hardness of 27 mm is 150 kN / m ² .
In other words, from the result shown in FIG. 5, even if an additive is added, there is no risk of inhibiting the growth of plant roots, and the uniaxial compressive strength is 150 kN / m ² or less that can be applied as a vegetation base. It became clear that it was the compounding quantity of the additive material.
And from the experiments of the inventors described above with reference to Tables 2 to 4, FIG. 4 and FIG. 5, the shear strength can be significantly increased, and there is no possibility of inhibiting the growth of plant roots. is appropriate as vegetation foundation, uniaxial compressive strength was found to be a compounding amount of the additive material to be ^{30kN / m 2 ~150kN / m 2} .

About the soil hardness and pH of the continuous fiber reinforced soil which concerns on embodiment, the inventor experimented also with another specimen.
The specimens shown in Table 5 below were measured for uniaxial compressive strength and pH.
Specimen No. The specimens with “N” added thereto do not include continuous fibers, and the specimens with “F” added include continuous fibers.
Table 5

In Table 5, low alkali (pH is less than 11) is the specimen No. CN2 (uniaxial compressive strength is 238.0 kN / m ² ) and specimen No. Specimens other than CF2 (uniaxial compressive strength was 238.0 kN / m ² ).
That is, if the amount of additive material uniaxial compressive strength is in the range of ^{30kN / m 2 ~150kN / m 2} , pH of continuous fiber reinforced soil has on low alkali (pH less than 11), and the plants affected It became clear that can be reduced.

According to the inventor's experiment, it was found that the blowing hose length needs to be 60 m or more in order to express the required uniaxial compressive strength of 30 kN / m ² .
Add 1% of calcium-based solidified material (low alkali calcium-based solidified material) to sandy soil as additive, do not mix continuous fibers, and mix the length of sandy soil and calcium-based solidified material. It transferred with the spraying hose of 20m, 40m, 60m, 80m, and 100m, and measured the uniaxial compressive strength after that.
The results are shown in Table 6 below.
Table 6

FIG. 6 shows the results shown in Table 6 plotted in a chart in which the ordinate represents uniaxial compressive strength and the abscissa represents the blowing hose length.
From Table 6 and FIG. 6, it is clear that the length of the spray hose should be 60 m or more in order to develop the uniaxial compressive strength of 30 kN / m ² .
In addition, even when an additive other than the low alkali calcium-based solidified material is mixed in the sandy soil, as in the case shown in Table 6 and FIG. 6, in order to express the uniaxial compressive strength of 30 kN / m ² , The length of the spray hose was required to be 60 m or more.
When spraying the continuous fiber reinforced soil, the sandy soil and the additive are agitated in addition to being agitated by the spraying machine and being transported through the spraying hose. Therefore, in order to mix the sandy soil and the additive uniformly, it is necessary to sufficiently stir in the spray hose, and the length of the spray hose needs to be 60 m or more.

From the above-described experiment results of the inventors, if the continuous fiber reinforced soil (sandy soil, additive, mixture of continuous fibers) used in the embodiment, the additive such as cement is added to increase the shear strength. It is clear that soil hardness does not increase to the extent that plant growth is adversely affected.
Therefore, since the continuous fiber reinforced soil sprayed to the area to be constructed has high shear strength, various wall surfaces, slopes, and the like can be reinforced. At the same time, it can be suitably sprayed as a vegetation base.
As described with reference to FIGS. 2 and 3, the continuous fiber reinforced soil used in the illustrated embodiment does not improve the shear strength of the sandy soil itself, but increases the reinforcing effect of the continuous fibers. doing.
The reason why the shear strength of continuous fiber reinforced soil containing continuous fibers is higher than that of sandy soil containing no continuous fibers is due to the frictional force between sandy soil and continuous fibers. Presumed. In the continuous fiber reinforced soil used in the embodiment, by adding an additive, the frictional force between the sandy soil and the continuous fiber increases, making it difficult to pull out the continuous fiber from the sandy soil. The effect and shear strength are thought to have increased.

As described above, the reinforcing effect of continuous fibers is expressed by an improvement in shear strength.
Here, the shear strength increases when the force for solidifying the sand and fiber is large. Here, in general, the force by which the sand and the fiber are solidified is often indicated by uniaxial compressive strength. This is because the measurement of the uniaxial compressive strength is easy and the reliability is high because it is defined by the Japanese Industrial Standard (JIS).
As a parameter for displaying the force with which sand and fibers harden, it may be expressed as “force to pull out continuous fibers”. However, it is difficult to measure the “force for pulling continuous fibers”. For this reason, uniaxial compressive strength is used in the present invention to define the amount of additive added.

According to the illustrated embodiment, the increase in pH can be suppressed without increasing the soil hardness to an extent that adversely affects plant growth, and the reinforcing effect and shear strength of continuous fiber reinforced soil can be increased. I can do it.
And according to embodiment of illustration, since it becomes difficult to pull out a continuous fiber from sandy soil and the reinforcement effect and shear strength of a continuous fiber increase, the reliability of a continuous fiber reinforcement earthwork method can be improved.
In addition, since the amount of additive added is defined by the uniaxial compressive strength, which is a highly reliable parameter because it is defined by the Japanese Industrial Standards (JIS), continuous fiber reinforced soil can be accurately and objectively used at the construction site. Can be adjusted and mixed.

It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.
For example, in the illustrated embodiment, the case where the continuous fiber reinforced soil is used as a vegetation base is described. Is possible.
Further, the system for applying the continuous fiber reinforced earth method is not limited to the system shown in FIG.

DESCRIPTION OF SYMBOLS 2 ... Continuous fiber 6 ... Injection nozzle 7 ... Ejector 8 ... Sand conveyance mechanism 10 ... Hopper 11 ... Metering device 12 ... Spraying machine 15 ... Compressor 19 ... Bobbin 20 ... Continuous fiber supply mechanism 21 ... Bobbin case 25 ... Guide stay 33 ... Material hose 35 ... Continuous fiber supply device

Claims (1)

In the continuous fiber reinforced earth method in which sandy soil and continuous fibers are sprayed, the method includes a step of mixing an additive with the sandy soil, and the additive has a uniaxial compressive strength of 30 kN / m ² to the mixture of the sandy soil and the additive. It is added so that it may become in the range of 150 kN / m < ² >, The continuous fiber reinforcement earthwork method characterized by the above-mentioned.

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