JP6248424B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement method mainly applied to soft ground for the purpose of preventing liquefaction and improving bearing capacity.

  Liquefaction due to earthquakes causes damage such as collapse of the pile due to the lateral flow of the ground as well as the ground losing vertical bearing capacity and causing collapse of the building, so various countermeasures have been researched and developed conventionally. In addition to the drain method and the groundwater level lowering method that dissipate excess pore water pressure, as a countermeasure work by improving the ground, a consolidation method by chemical injection or a compaction method by sand compaction pile is known.

  In addition, when performing civil engineering construction work, if the strength of the ground is insufficient, it is necessary to improve the ground prior to construction of the main body. An improved body with improved strength is created in the ground by injecting chemicals into the ground and by mixing with a cement-based hardener in place while cutting the soil that spreads over a predetermined area in the ground. The method of doing is known.

JP 2012-251368 A

  Here, the countermeasure work by the chemical injection is widely adopted for preventing liquefaction and improving the ground and has high reliability. However, since the cost is high, it may be difficult to adopt when the target is wide.

  On the other hand, when hydraulic materials such as cement are used to prevent liquefaction and improve the ground, sufficient strength can be expected, but the growth of the plant is inhibited by the transition of the pH environment to the alkali side, or heavy metals Cause problems such as elution.

  For example, harmful substances such as lead and selenium that naturally exist in the ground exceed the environmental standards because the ground has changed to an alkaline environment even though there is no problem if the amount of elution is below the environmental standards. May elute.

  In addition, hexavalent chromium may be contained in cement, but since it is fixed by hydration reaction, it is not a problem at all. May leach into the ground.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a ground improvement method which is excellent in economic efficiency and has a small environmental load.

In order to achieve the above object, the ground improvement method according to the present invention, as described in claim 1, uses a nanofiber- containing liquid in which only nanofibers derived from animals and plants are added and mixed in water as a target ground for liquefaction prevention. Osmotic injection.

In addition, the ground improvement method according to the present invention, as described in claim 2, adds the nanofibers derived from animals and plants to the stirring region while stirring the target ground for improving the ground bearing capacity, or only the nanofibers are in water. By injecting the nanofiber- containing liquid that has been added and mixed, the stirring soil that spreads into the stirring region and the nanofiber or the nanofiber- containing liquid are mixed.

Further, soil improvement method according to the present invention as described in claim 3, excavated soil, soil generated other raw soil nanofiber containing liquid only nanofibers or the nanofiber from plants and animals have been added to and mixed in water Is added, and then these are mixed to prepare a nanofiber mixed soil, and the nanofiber mixed soil is applied as a backfill material, embankment material or other improved soil.

  In the ground improvement method according to the present invention, the improved soil is laid as a banking material, and then the banking material is rolled.

  Moreover, the ground improvement method which concerns on this invention uses the said nanofiber as a cellulose nanofiber.

In the ground improvement method according to the first invention, a nanofiber- containing liquid obtained by adding and mixing only nanofibers derived from animals and plants into water is infused into the target ground to prevent liquefaction.

  In this way, since the nanofiber has a fiber diameter of the order of nanometers, coupled with the fact that the target ground is not sufficiently compacted, the gap between the soil particles diffuses widely as a flow path, and then Intertwined with soil particles within the infused range.

  During an earthquake, the nanofibers entangled with the soil particles exert a fiber reinforcing action that resists the displacement and movement of the soil particles. As a result, shear deformation of the entire ground is suppressed, and between the soil particles An increase in pore water pressure, and hence liquefaction, can be prevented in advance.

  Further, since no cement-based hardener is used, there is no fear that clogging will occur in the injection source or the ground in the vicinity thereof during penetration and there is no concern that penetration will be hindered and no harmful substances will be eluted.

  The target ground is a loose saturated sandy ground that is not sufficiently compacted, and the soil particles in the first invention are mainly used in the sense of sand particles.

In the ground improvement method according to the second invention, the nanofibers containing only the target ground stirred while adding nanofibers from plants and animals to the stirred region or said nanofibers improved soil bearing capacity is admixed to the water By injecting the liquid, the agitating soil spreading in the agitating region and the above-mentioned nanofiber or nanofiber- containing liquid are mixed.

  In this way, the nanofibers have a fiber diameter on the order of nanometers, so that they can be entangled with the soil particles of the agitated soil and exert a fiber reinforcing action that resists the displacement and movement of the soil particles. Will increase.

  In addition, since no cement-based hardener is used, there is no risk of clogging occurring at the injection source or in the vicinity of the ground during injection, and the injection may be hindered, and the ground becomes an alkaline environment and harmful substances are eluted. There is no concern.

When adding and mixing the nanofiber or the nanofiber- containing liquid, while cutting and stirring and mixing with a stirring and mixing device in which a stirring blade is provided on the peripheral surface of the hollow rod, the nanofiber or the nanofiber is discharged from the discharge hole of the hollow rod. You may comprise so that a nanofiber containing liquid may be ejected, and it is good also as a structure which carries out high pressure injection of these with compressed air and water.

  Among these, addition mixing by high-pressure injection is a method used when creating an improved body on the ground using a hardening material such as cement milk, for example, moving forward or backward while rotating a multi-tube rod inserted in the ground. In addition, it is possible to use a high-pressure jet stirring method called a jet grout method or a high-pressure jet stirring method in which a hardener, water, or compressed air is injected into the ground from a discharge port provided in the multi-tube rod. There are various methods such as the JSG method, the CJG method, the CCP method, and the RJP method that have been developed depending on the type of the high-pressure jetted fluid and the manner of jetting.

In the ground improvement method according to the third invention, the nanofibers derived from animals and plants or the nanofiber- containing liquid in which only the nanofibers are added to water are added to the excavated soil, generated soil and other raw material soil, and then these are added. A nanofiber mixed soil is prepared by mixing, and the nanofiber mixed soil is applied as a backfill material, a fill material, or other improved soil.

  If it does in this way, since the fiber diameter of a nanofiber is a nanometer order, nanofiber mixed soil will be produced in the state where the nanofiber entangled with the soil particle of raw material soil.

  Therefore, when the nanofiber mixed soil is constructed as improved soil, the nanofiber exhibits a fiber reinforcing action that resists displacement and movement of the soil particles, and as a result, the supporting force of the constructed ground increases.

  Here, if the improved soil is laid as a banking material, and then the banking material is rolled, the above-mentioned fiber reinforcing action is further enhanced by the rolling, so that a banking with excellent deformation characteristics can be created. It becomes possible.

  In addition, since the nanofiber itself becomes a water passage, or the gap formed between the nanofiber and the soil particles or between the nanofibers becomes a water passage, it is possible to create a bank with excellent drainage. Become.

As described above, the local ground improvement method according to the first to third inventions is a method in which a nanofiber or a nanofiber- containing liquid is infiltrated, injected or added to a target ground or a raw soil, and is cement-based. Although there is an effect that there is no need to worry about various problems caused by the use of the hardener of this type, the present invention is a hardener (cement-based material) conventionally used for liquefaction countermeasures or ground improvement . It does not exclude the combined use with chemicals ) .

That is, since nanofiber is a chemically stable material, it can be used in combination with a conventionally known curing material or chemical, for example, a water glass chemical .

In the first invention, the nanofiber in each of the above-described inventions is used in the form of a contained liquid because it is osmotic injection. In the second and third inventions, in addition to the contained liquid, it is used in the form of a powder. It doesn't matter if you do.

  In addition, the nanofiber of each invention has a diameter of 10 nm to 100 nm, as long as the diameter is less than 1 μm, that is, the specific configuration is not limited as long as the fiber is intertwined with the soil particles and exhibits a fiber reinforcing action. In the case of nanofibers having a length of about 1 to 10 μm, the above-described fiber reinforcing action is further improved by good entanglement with soil particles.

  Animal and plant-derived nanofibers, that is, bio-nanofibers, can be composed of chitin nanofibers obtained from animal-derived resources such as crustaceans, but if they are composed of cellulose nanofibers (cellulose microfibrils), Since this can be taken out from plant-derived resources abundant on the earth such as wood, pulp, paper, and cloth, it is possible to realize a ground improvement method that is excellent in economic efficiency.

  In particular, if the above-mentioned plant-derived resources are composed of materials that have been incinerated conventionally, such as waste wood generated during construction, paper lumber mill residue, rice straw and straw, thinned wood and driftwood, biomass and On the other hand, carbon dioxide absorbed by plants during photosynthesis can be effectively used in a fixed form without returning to the atmosphere, thus greatly contributing to the realization of a low-carbon society.

The vertical sectional view showing the implementation situation of the ground improvement method concerning a 1st embodiment. Explanatory drawing which showed the effect | action of the ground improvement method which concerns on 1st Embodiment. The vertical sectional view showing the implementation situation of the ground improvement method concerning a 2nd embodiment. The conceptual diagram which showed the ground improvement method which concerns on 1st Embodiment.

  Hereinafter, embodiments of a ground improvement method according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a vertical sectional view showing a ground improvement method according to the first embodiment. As shown in the figure, in the ground improvement method according to the present embodiment, first, an osmotic injection tube 1 in which a large number of water permeable holes are formed is buried in a target ground 2 to prevent liquefaction, and then the osmotic injection tube is Then, a nanofiber- containing liquid obtained by adding and mixing nanofibers derived from animals and plants, in this embodiment, cellulose nanofibers, is infused into the target ground 2.

  Cellulose nanofibers are, for example, cellulose nanofibers with a diameter of 10 to 100 nm that are microfibrillated by applying a shearing force to plant fibers such as pulp by an ultra-high pressure homogenizer treatment. Specifically, Daicel Finechem Co., Ltd. Microfibrous cellulose sold under the name can be used.

What is necessary is just to produce a nanofiber containing liquid so that the density | concentration of a cellulose nanofiber may be 0.01 to 0.1 weight%.

When the nanofiber- containing liquid is infiltrated and injected into the target ground 2 in this manner, as shown in FIG. 2A, the cellulose nanofiber 21 has a fiber diameter on the order of nm, so that the target ground 2 is sufficiently compacted. In combination with this, the gap between the soil particles 22 is diffused widely as a flow path, and then entangled with the soil particles 22 within the infiltrated and injected range.

  When an earthquake occurs in such a state, the cellulose nanofibers 21 entangled with the soil particles 22 exhibit a fiber reinforcing action that resists displacement and movement of the soil particles 22 as shown in FIG.

As described above, according to the ground improvement method according to the present embodiment, the nanofiber- containing liquid in which the cellulose nanofibers 21 are added and mixed through the permeation injection tube 1 is infused into the target ground 2. Therefore, in the event of an earthquake, the cellulose nanofibers 21 entangled with the soil particles 22 exert a fiber reinforcing action that resists the displacement and movement of the soil particles, and as a result, shear deformation of the entire target ground 2 is suppressed. In addition, an increase in pore water pressure between the soil particles 22 and, in turn, liquefaction can be prevented.

  Further, according to the ground improvement method according to the present embodiment, since a cement-based hardener is not used, there is no possibility that clogging may occur in the ground at or near the injection source and penetration may be hindered when infiltrating. There is no concern of toxic substances eluting.

In this embodiment, the nanofiber- containing liquid obtained by adding and mixing the cellulose nanofibers 21 is infiltrated and injected into the target ground 2 alone, but at the same time as or after the infiltration of the nanofiber- containing liquid, A cement-type hardener may be injected.

According to such a configuration, in addition to the above-described fiber reinforcing action by the cellulose nanofibers 21, an effect of increasing the strength by the cement-based curing material is exhibited, and the cement is not as much as when the nanofiber- containing liquid is used alone. Since the amount of the system-hardening material can be reduced, it is possible to reduce the concern that clogging occurs during injection and the injection is hindered, or that the ground becomes an alkaline environment and harmful substances are eluted. .

[Second Embodiment]
Next, a second embodiment will be described. Note that components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the ground improvement method according to the second embodiment, as shown in FIG. 3 (a), first, according to the JSG method, for example, the rod 32 is inserted into the ground 31 to be improved in ground support force. While rotating around the material axis and raising along the material axis, the nanofiber- containing liquid is jetted together with compressed air through a discharge port 33 provided near the lower end thereof.

Similar to the first embodiment, the nanofiber- containing liquid may be prepared as a containing liquid in which cellulose nanofibers 21 are added and mixed.

The rod 32 has a double pipe structure in which two flow paths are formed along the material axis direction, and the proximal end side of each flow path is respectively connected to a pumping device and a compressor (not shown) installed on the ground. In addition to being connected in communication, the tip is connected to the discharge port 33 so that the nanofiber- containing liquid and compressed air separately pumped from the ground can be ejected from the discharge port 33 simultaneously.

When the nanofiber- containing liquid is injected into the ground 31 together with compressed air through the discharge port 33 at a high pressure, the ground 31 is cut and stirred by the jet flow generated by the high-pressure injection and contains nanofibers injected into the ground 31 in the form of high-pressure injection The liquid is mixed with the stirring soil in the ground 31 at the original position, and after the high pressure injection is finished, the dimension from the depth position where the high pressure injection is started to the depth position where the high pressure injection is finished is the height H, and the injection pressure and the ground A cylindrical nanofiber distribution region 34 having a radius R as a cuttable distance from the discharge port 33 determined by the properties is formed in the ground 31 as shown in FIG.

  Thus, in the nanofiber distribution region 34 formed in the ground 31, since the cellulose nanofiber 21 has a fiber diameter on the order of nm, as described with reference to FIG. It exerts a fiber reinforcing action that resists displacement and movement of soil particles.

As described above, according to the ground improvement method according to the present embodiment, the stirring soil and the nanofiber- containing liquid are mixed by injecting the nanofiber- containing liquid into the stirring region while stirring the ground 31. In the nanofiber distribution region 34, the cellulose nanofiber 21 entangled with the soil particles has a fiber reinforcing action that resists displacement and movement of the soil particles. As a result, the supporting force of the nanofiber distribution region 34 is increased.

  Further, according to the ground improvement method according to the present embodiment, since no cement-based hardener is used, there is no possibility that harmful substances are eluted.

In the present embodiment, the cellulose nanofibers 21 are injected into the ground 31 in the form of a containing liquid as in the first embodiment. Instead, the cellulose nanofibers 21 are added to the ground 31 in the form of powder. It doesn't matter.

In the present embodiment, the nanofiber- containing liquid obtained by adding and mixing the cellulose nanofibers 21 is injected into the ground 31 as a single unit, but at the same time as or after the injection of the nanofiber- containing liquid, A cementitious hardener, such as cement milk, may be injected. In the above-described modification, a cementitious hardener, such as cement milk, may be added at the same time as or after the cellulose nanofiber 21 is added in the form of powder. It does not matter if you inject.

According to such a configuration, in addition to the above-described fiber reinforcing action by the cellulose nanofibers 21, an effect of increasing the strength by the cement-based curing material is exhibited, and the cement is not as much as when the nanofiber- containing liquid is used alone. Since the amount of the system-hardening material can be reduced, it is possible to reduce the concern that clogging occurs during injection and the injection is hindered, or that the ground becomes an alkaline environment and harmful substances are eluted. .

[Third Embodiment]
Next, a third embodiment will be described. In addition, about the components substantially the same as 1st, 2 embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the ground improvement method according to the third embodiment, as shown in FIG. 4, the excavated soil that is the raw soil is put into the stirring and mixing tank 41 and the cellulose nanofibers 21 are added to the excavated soil, and then these are added. The nanofiber mixed soil 42 is prepared by stirring and mixing in the stirring and mixing tank 41.

  Next, the nanofiber mixed soil 42 is laid on the ground 43 as a fill material, and the fill 44 is formed by rolling the fill material.

  In this case, since the fiber diameter of the cellulose nanofibers 21 is on the order of nm, the nanofiber mixed soil 42 is produced in a state where the cellulose nanofibers 21 are intertwined with the soil particles of the excavated soil, as described in FIG. Is done.

  As described above, according to the ground improvement method according to the present embodiment, since the nanofiber mixed soil 42 is constructed as the embankment material that is the improved soil, the contained cellulose nanofibers 21 are displaced from the soil particles. The fiber reinforcing action that resists the movement is exhibited, and as a result, the supporting force of the embankment 44 increases.

  Further, according to the ground improvement method according to the present embodiment, since the nanofiber mixed soil 42 laid as the embankment material is rolled, the above-described fiber reinforcement action is further enhanced by the rolling pressure, and the embankment 44 is deformed. The characteristics can be further improved.

  Moreover, according to the ground improvement method which concerns on this embodiment, the cellulose nanofiber 21 itself contained in the nanofiber mixed soil 42 becomes a water passage, or between the cellulose nanofiber 21 and soil particles or between the cellulose nanofibers 21. Since the gap formed between the two becomes a water passage, the drainage of the embankment 44 can be improved.

  Moreover, according to the ground improvement method which concerns on this embodiment, since a cement hardening material is not used, there is no fear that a harmful substance elutes.

In the present embodiment, the cellulose nanofibers 21 are added to the excavated soil, which is the raw material soil, in the form of powder. Instead of this, the raw material soil is formed in the form of a contained liquid as in the first and second embodiments. It may be added to.

In the present embodiment, the cellulose nanofibers 21 are added alone to the excavated soil, which is a raw material soil. However, a cement-based hardener, such as cement milk, is added simultaneously with or before the addition of the cellulose nanofibers. In the above modification, a cement-based hardener, such as cement milk, is injected at the same time as or after the addition of the nanofiber- containing liquid to which the cellulose nanofibers 21 are added. It doesn't matter if you do.

  According to such a configuration, in addition to the above-described fiber reinforcing action by the cellulose nanofibers 21, an effect of increasing the strength by the cement-based hardener is exhibited, and the cement is not as much as when the cellulose nanofibers 21 are used alone. Since the usage-amount of a system hardening material can be reduced, it becomes possible to reduce a concern that the ground becomes an alkaline environment and a harmful substance elutes.

2,31 Target ground 21 Cellulose nanofiber (Nanofiber derived from animals and plants)
22 Soil particles 42 Nanofiber mixed soil (improved soil, embankment material)

Claims (5)

A ground improvement method comprising infiltrating and injecting a nanofiber- containing liquid, in which only animals and plants-derived nanofibers are added and mixed into water, into the target ground for liquefaction prevention. Stirring that spreads to the stirring region by adding nanofibers derived from animals and plants to the stirring region while stirring the target ground for improving the ground bearing capacity or injecting a nanofiber- containing liquid in which only the nanofibers are added to water A soil improvement method, comprising mixing soil and the nanofiber or the nanofiber- containing liquid. Add nanofibers derived from animals and plants to the excavated soil, generated soil or other raw material soil or a nanofiber- containing liquid in which only the nanofibers are added to water, and then mix them to create a nanofiber mixed soil, A ground improvement method characterized by constructing the nanofiber mixed soil as a backfill material, embankment material or other improved soil. The ground improvement method according to claim 3, wherein the improved soil is laid as a banking material, and then the banking material is rolled. The ground improvement method according to any one of claims 1 to 4 , wherein the nanofibers are cellulose nanofibers.

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