JP5166984B2 - Construction method of impermeable wall - Google Patents

Description

  The present invention relates to a method for constructing a water shielding wall using a clay mineral containing smectite such as bentonite.

  The coastal areas of Japan are densely packed with factories, as represented by the Pacific Belt Zone. In recent years, environmental pollution in which pollutants leak outside the site from such factories and their ruins has become an important issue. In addition, in industrial waste disposal sites built in inland areas and their former sites, pollutants may leak and worsen the surrounding environment in the same manner as in coastal factories and their former sites. And as a countermeasure against these pollutions, there is a method of blocking the leakage of pollutants (preventing diffusion) by constructing a water-impervious wall at a position that becomes the site boundary of the target ground.

  As a method for constructing this impermeable wall, for example, an earth ground auger machine or the like is used to excavate the target ground (the portion of the ground that constructs the impermeable wall), and the soil and sand in the ground formed by this excavation are cemented. A method of supplying and stirring a suspension of a solidifying material and bentonite is generally known. In this method, the agitated earth and sand hardens and becomes a water-impervious wall. However, if a cement-based solidifying material is supplied in the construction of the impermeable wall, the constructed impermeable wall cannot follow the deformation of the ground, so that the impermeable property cannot be maintained for a long time.

  Therefore, it is conceivable to adopt a method in which a clay mineral suspension is filled in a drilling hole or a trench formed by excavating the target ground without supplying cement-based solidified material. In this method, since the filled clay mineral which becomes a water-impervious wall has followability to ground deformation caused by self-repairing property, the water-impervious property can be maintained for a long time. However, in this method, since the cement-based solidifying material is not supplied, the strength of the water-impervious wall is relatively weak, which may cause the surrounding ground to collapse.

  Therefore, the method is to supply only the clay mineral suspension to the soil in the ground formed by excavation without supplying cement-based solidification material, and stir it, and use this stirred soil as a water-impervious wall. Has been proposed (see, for example, Patent Document 1). However, in order to make the impermeable wall constructed by this method as strong as the ground, it is necessary to supply a clay mineral suspension with a high concentration. However, since the clay mineral suspension is highly viscous, if the clay mineral suspension is supplied at a high concentration, the load of liquid feeding due to pumping becomes too large, and an earth auger machine or the like was used. There exists a problem that the stirring efficiency by mechanical stirring will worsen.

  Therefore, in order to solve this problem, the present applicant supplies a clay mineral suspension and performs prior stirring, and supplies the clay mineral powder to the previously stirred soil and performs subsequent stirring. And the method of using the earth and sand which carried out this subsequent stirring as a water-impervious wall was proposed (refer patent document 2).

  However, if the target ground is, for example, a coastal area, the sea, a land for disposal of industrial waste, or a site of these, and if the electrolyte contains seawater or contaminated water, the electrolyte acts on the clay mineral. As a result, the viscosity increases and the amount of dehydration increases (inhibition of swelling action). An increase in viscosity leads to a decrease in stirring efficiency and a decrease in the strength and water impermeability of the impermeable wall due to this, and an increase in the amount of dehydration directly leads to a decrease in the strength and water impermeability of the impermeable wall.

Therefore, it may be possible to refer to the already proposed “Method of adding sodium carbonate and caustic soda to seawater to suspend montmorillonite clay mineral and kaolinite clay mineral (see Patent Document 3)”. Be considered. However, the method described in Patent Document 3 is not conscious of actual construction, and it is not clear how to apply to the method described in Patent Document 2 and how to apply it. Even when the target ground contains water in which the electrolyte is dissolved, there is a demand for a method that can be actually constructed without reducing the strength and water barrier properties of the water barrier wall.
Japanese Patent Laid-Open No. 11-43934 Japanese Patent Laid-Open No. 2005-16295 Japanese Patent Laid-Open No. 1-103691

  The main problem to be solved by the present invention is the construction of a water-impervious wall that can be actually constructed without lowering the strength and water-imperviousness of the water-impervious wall even when the target ground contains water in which the electrolyte is dissolved. It is to provide a method.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
Suspension of clay mineral containing smectite is supplied to the soil in the ground formed by excavation of the target ground and pre-stirred, and clay mineral powder containing smectite is added to the pre-stirred soil and sand. A method for constructing a water-impervious wall, comprising supplying and agitating downstream, and using the earth and sand subjected to the subsequent agitation as a water-impervious wall,
Among the preceding stirring and the subsequent stirring, at least in the preceding stirring, an ion shielding agent is supplied to the earth and sand ,
As an ion shielding agent in the preceding stirring,
Using sodium carbonate and caustic soda,
These supplies are performed in the order of the sodium carbonate and the caustic soda after the clay mineral is supplied.
The construction method of the impermeable wall characterized by the above-mentioned.

[Invention of Claim 2]
Supplying the ion shielding agent;
In the state of suspension in the preceding stirring, and in the state of powder in the subsequent stirring.
The construction method of the impermeable wall according to claim 1.

[Invention of Claim 3]
The ion shielding agent is supplied in the preceding stirring after the clay mineral is supplied.
The construction method of the impermeable wall of Claim 1 or Claim 2.

[Invention of Claim 4 ]
As the clay mineral suspension, water containing 50 to 200 kg of the clay mineral in 1000 L of water is used. In the preceding stirring, 50 to 200 L of the clay mineral suspension is supplied per 1 m ^{3 of the} earth and sand, And 0.5 to 20 kg of the ion shielding agent is supplied,
On the other hand, in the subsequent stirring, 50 to 200 kg of the clay mineral powder is supplied per 1 m ^{3 of the} earth and sand, and 0.5 to 20 kg of the ion shielding agent is supplied.
The construction method of the impermeable wall according to any one of claims 1 to 3 .

  According to the present invention, even when the target ground contains water in which the electrolyte is dissolved, the water impervious wall can be actually constructed without lowering the strength and water imperviousness of the impermeable wall.

Next, an embodiment of the present invention will be described.
In the construction method of the impermeable wall of the present embodiment, for example, a target ground is excavated using a drilling device or the like to be described later, and a clay mineral suspension containing smectite is formed in the earth and sand formed by the excavation. Is supplied, and the pre-stirred earth and sand is supplied with a clay mineral powder containing smectite, followed by subsequent stirring, and the latter-stirred earth and sand is used as a water-impervious wall. By supplying a suspension of clay mineral containing smectite to the earth and sand in the ground and conducting agitation in advance, the stability of the excavation holes and grooves formed by the excavation is increased and the collapse of the ground is prevented. The In addition, when the clay mineral containing smectite is supplied to the pre-stirred earth and sand and the subsequent stirring is performed, the clay mineral is supplied not in a suspension state but in a powder state. When supplied in a powder state, the increase in viscosity of the earth and sand is delayed, and the stirring efficiency is improved. As a result, the properties of the water-impervious walls to be constructed are made uniform, and the strength and water impermeability are prevented from being lowered. Moreover, since the amount of water supplied to the earth and sand is reduced when supplied in the form of powder, there is an advantage that the amount of mud is reduced.

  Here, the “powder” is a state in which a large number of solids are aggregated as particles. Therefore, the size of each solid is not particularly limited, but is usually 40 mesh to 350 mesh, preferably 200 mesh to 320 mesh in consideration of economy. Furthermore, the degree of swelling is preferably 16 mL / 2 g or more, and more preferably 20 mL / 2 g.

  In this embodiment, the ground to be processed is not particularly limited. However, if the target ground is, for example, the ground, sea, land for disposal of industrial waste, or ground containing water in which electrolytes such as seawater and contaminated water are dissolved, the effects of the present invention are not significant. It is demonstrated without. In addition, smectite is a group of minerals having a crystal structure and properties similar to those of montmorillonite, and examples include montmorillonite, beidellite, nontronite, sabonite, hectorite, soconite, stevensite, etc. it can. Examples of clay minerals containing montmorillonite include bentonite.

  In the present embodiment, the ion shielding agent is supplied to the earth and sand at least in the preceding stirring, preferably both in the preceding stirring and the following stirring, among the preceding stirring and the following stirring. As described above, when the target ground contains water in which the electrolyte is dissolved, the electrolyte acts on the clay mineral, leading to an increase in viscosity and an increase in dewatering amount (inhibition of swelling action). An increase in viscosity leads to a decrease in stirring efficiency and a decrease in the strength and water impermeability of the impermeable wall due to this, and an increase in the amount of dehydration directly leads to a decrease in the strength and water impermeability of the impermeable wall. However, when an ion shielding agent is supplied to the earth and sand, the electrolyte becomes difficult to come into contact with the clay mineral, and an increase in viscosity and an increase in dehydration amount can be suppressed.

  Here, examples of the electrolyte that acts on the clay mineral containing smectite include alkaline earth metal ions such as calcium ions and magnesium ions. Therefore, in order to prevent the electrolyte from acting on the clay mineral, it is sufficient that such ions do not easily come into contact with the clay mineral, and it is preferable to shield the contact of the ions with the clay mineral. Therefore, in the present invention, a chemical solution having an ion shielding effect, that is, an ion shielding agent is supplied. Suitable examples of this ion shielding agent will be described later.

  By the way, the method of the present embodiment, that is, the soil in the ground formed by excavation of the target ground, the suspension of clay mineral containing smectite is supplied and pre-stirred, and the pre-stirred soil and sand, In the method of supplying the clay mineral powder containing smectite and performing the subsequent stirring, and using the soil and sand subjected to the subsequent stirring as the water shielding wall, there is no knowledge about the timing and method of supplying the ion shielding agent. The present inventors repeated various tests and examinations. As a result, it has been found that a large effect can be obtained when the ion shielding agent is supplied at least in advance stirring, and the present invention has been achieved. For example, since the viscosity of the earth and sand is relatively low, the ion shielding agent is preferably supplied in advance stirring. Therefore, the stirring efficiency is good, the ion shielding agent is excellent in diffusibility, and the ions act on the clay mineral. This is thought to be due to the fact that it can be prevented at an early stage.

  In this embodiment, the ion shielding agent can be supplied in the preceding stirring, preferably both in the preceding stirring and the subsequent stirring. It is preferable to carry out in the state of a turbid liquid and to carry out the subsequent stirring in the state of powder. In the prior stirring, since the clay mineral is supplied in a suspension state, it is preferable to supply the ion shielding agent in a suspension state. In this regard, when supplying the ion shielding agent at a different time (with a time difference) from that of the clay mineral, it is preferable to supply it in a suspension state so as not to inhibit the swelling action of the clay mineral.

  On the other hand, in the subsequent stirring, since the clay mineral is supplied in a powder state, the ion shielding agent is preferably supplied in a powder state. In this regard, when supplying the ion shielding agent at a time different from that of the clay mineral (with a time difference), it is preferable to supply the ion shielding agent in a powder state. This is because the purpose of supplying clay mineral in a powder state instead of a suspension state in the subsequent stirring, that is, the purpose of delaying the viscosity increase of the earth and sand and the purpose of reducing the amount of discharged mud, This is not to kill.

  In this embodiment, it is more preferable that the ion shielding agent is supplied in advance stirring after the clay mineral is supplied. Hereinafter, this point will be described in detail with reference to FIG. In addition, the supply method of the ion shielding agent in the preceding stirring described below can be applied to the supply of the ion shielding agent in the subsequent stirring as long as it does not contradict the purpose of the supply.

  In this embodiment, as a method for supplying the ion shielding agent A, as shown in FIGS. 1 (1) and (2), a method that is performed simultaneously with the supply of the clay mineral B (hereinafter, simply referred to as a “method simultaneously performed”). ) And a method (hereinafter also referred to simply as a “method with a time difference”) performed at a time different from the supply of the clay mineral B (with a time difference), as shown in (3) of FIG. There is. In addition, the description in FIG. 1 uses the horizontal direction as a time axis, and means that time progresses toward the right side of the drawing.

  In addition, as the former “method to be performed simultaneously”, as shown in FIG. 1 (1), in addition to a method in which the ion shielding agent A and the clay mineral B are mixed in advance and transported and supplied in this mixed state, As shown in (2) of 1, there is also a method in which the ion shielding agent A and the clay mineral B are not mixed in advance but are conveyed in separate systems and the supply timing is simultaneous. However, if the ion shielding agent A and the clay mineral B are supplied at the same time, depending on the type of the ion shielding agent A, the viscosity of the clay mineral B may increase, and the stirring efficiency may decrease. Therefore, from such a viewpoint, a method of transporting and supplying simultaneously in a separate system (method (2) of FIG. 1) rather than a method of mixing and transporting and supplying in advance (method (1) of FIG. 1). Is preferable, and the method of supplying with a time difference (method (3) in FIG. 1) is more preferable. In this regard, also in the method of mixing and transporting and supplying in advance (method (1) of FIG. 1), a dispersant is added to the mixture of the ion shielding agent A and the clay mineral B to suppress an increase in viscosity. However, there is a problem that the cost of the chemical solution increases.

According to the test conducted by the present inventors, the following results were obtained.
First, when the viscosity of 10% concentration bentonite is measured with a 500/500 mL funnel viscometer, it is 48.1 seconds. When 3 kg / m ^{3 of} soda ash (sodium carbonate) serving as an ion shielding agent was added thereto, the viscosity became 65.3 seconds, and it can be seen that the viscosity increased with the introduction of soda ash. Further, when 10 kg / m ^{3 of a} dispersant (Super Slurry B, Sanyo Kasei Co., Ltd., polycarboxylic acid type high performance dispersant) is added, the viscosity becomes 44.3 seconds. It turns out that it fell.

  As the dispersant, it is preferable to use the polycarboxylic acid-based high-performance dispersant used in this test. However, depending on the on-site soil properties, for example, Aron AK Flow (manufactured by AK Techno Co., Ltd., polycarboxylate) System), Sankopol DE (manufactured by Sanko Colloid Chemical Co., Ltd.), sodium nitrohumate, sodium tripolyphosphate, and the like can also be used.

  On the other hand, as the latter “method with time difference”, as shown in FIG. 1 (3), the ion shielding agent A is supplied after the clay mineral B is supplied, although not shown, There is a method in which the shielding agent A is supplied before the clay mineral B is supplied. Although any of these methods can suppress an increase in viscosity, if the ion shielding agent A is supplied before the clay mineral B is supplied, the ion shielding agent A may be diffused more than necessary. On the other hand, when the ion shielding agent A is supplied after the clay mineral B is supplied, the ion shielding agent A is supplied to the soil whose viscosity has been moderately increased by the supply of the clay mineral B. Since there is no possibility that A will diffuse more than necessary, it is preferable to supply the ion shielding agent A after supplying the clay mineral B.

  By the way, in the above, in the case where there is one kind of ion shielding agent, the form of supplying at one time has been described as an example. However, the ion shielding agent has two kinds, three kinds, four kinds or more kinds. It is also possible to supply in two, three, four or more times. When the ion shielding agent is used in a plurality of types, or when the ion shielding agent is supplied in a plurality of times, it can be supplied in the same manner as in the case of supplying the one type described above at a time. Below, the case where two types of ion shielding agents are supplied is demonstrated to an example.

  When supplying two kinds of ion shielding agents, as a method of simultaneously supplying the ion shielding agent and the clay mineral, for example, as shown in FIG. 1 (4), two kinds of ion shielding agents A1, A2 and clay. In addition to mixing the mineral B in advance and transporting and supplying it in the mixed state, as shown in FIG. 1 (5), the two types of ion shielding agents A1 and A2 and the clay mineral B are not mixed in advance. There is also a method in which the feeding timing is simultaneous while transporting in a separate system.

  In addition, as a method of supplying the ion shielding agent and the clay mineral with a time difference, for example, as shown in (6) of FIG. 1, two kinds of ion shielding agents A1 and A2 are mixed in advance, As shown in FIG. 1 (7), two types of ion shielding agents A1 and A2 are transported in separate systems without being mixed in advance as shown in FIG. There is a method of sequentially performing after supply.

  When supplying two types of ion shielding agents, as shown in FIG. 1 (8), one of the two types of ion shielding agents A1 and A2 is previously mixed with clay mineral B. In this mixed state, there is a method of conveying and supplying, and then supplying the other ion shielding agent A2. This method is a method of combining the method of supplying the ion shielding agent and the clay mineral at the same time with the method of supplying the ion shielding agent and the clay mineral with a time difference. This also applies to a method of supplying with a time difference. This method has the disadvantage that the supply system of chemical solutions such as ion shielding agents and clay minerals is complicated, but on the other hand, for example, an ion shielding agent that does not increase the viscosity of clay minerals at the same time is supplied at the same time as the clay minerals. For example, an ion shielding agent having a large shielding effect may be supplied after the clay mineral is supplied.

  In this embodiment, the type of ion shielding agent is not particularly limited in both the preceding stirring and the subsequent stirring, and it is also possible to supply the same ion shielding agent in both the preceding stirring and the subsequent stirring. A screening agent can also be supplied.

  However, as an ion shielding agent in the preceding stirring, sodium carbonate and caustic soda are used, and the supply thereof is as shown in (7) of FIG. 1, after the clay mineral B is supplied, soda carbonate (A1), caustic soda (A2). ) In order, it becomes more preferable. When sodium carbonate and caustic soda are used as an ion shielding agent, calcium ions as an electrolyte are insolubilized (inactivated) by sodium carbonate, and magnesium ions as an electrolyte are insolubilized by caustic soda (this insolubilization will be described in more detail later). To explain.) Therefore, the electrolyte contact with the clay mineral is effectively shielded. Moreover, the viscosity increase of a clay mineral can be suppressed by supplying sodium carbonate and caustic soda after supplying the clay mineral. Furthermore, if caustic soda is supplied, depending on the amount of supply, there is a risk of pH fluctuations and thermal fluctuations of the earth and surrounding soil, but if sodium carbonate, which is more stable than caustic soda, is supplied first, this risk is reduced. The construction is stable.

In this embodiment, a clay mineral suspension containing 50 to 200 kg, preferably 80 to 150 kg of clay mineral in 1000 L of water is used, and in the preceding stirring, the clay mineral suspension per 1 m ^{3 of} earth and sand. 50 to 200 L, preferably 80 to 150 L, and 0.5 to 20 kg, preferably 3 to 15 kg, of ion shielding agent are supplied. On the other hand, in the subsequent stirring, clay mineral powder per 1 m ^{3 of} earth and sand is supplied. It is suitable to supply 50 to 200 kg, preferably 80 to 150 kg of body, and 0.5 to 20 kg, preferably 3 to 15 kg of ion shielding agent.

  When the clay mineral per 1000 L of water is less than 50 kg, in order to secure the strength of the impermeable wall, the supply amount of the clay mineral suspension must be increased, and when the supply amount of the clay mineral suspension is increased, A problem arises when the amount of mud increases. On the other hand, when the clay mineral per 1000 L of water exceeds 200 kg, the viscosity of the clay mineral suspension becomes high, so that the stirring efficiency decreases.

In addition, the amount of the clay mineral suspension supplied in the prior stirring depends on the concentration of the suspension and the moisture content of the earth and sand, but when the clay mineral suspension contains 50 to 200 kg of clay mineral in 1000 L of water. However, if it is less than 50 L per 1 m ^{3 of} earth and sand, clay minerals are not sufficiently diffused, and the properties of the impermeable wall may be uneven. On the other hand, when it exceeds 200L per 1 m ^{3 of} earth and sand, there is a problem that the amount of mud increases when the concentration of the clay mineral suspension is relatively low, and on the other hand, when the concentration of the suspension is relatively high There is a problem that it is not preferable in terms of cost and a problem that the load of the subsequent stirring increases due to the soil becoming too hard.

In addition, if the supply amount of the ion shielding agent is less than 0.5 kg per 1 m ^{3 of} earth and sand in the prior stirring, sufficient ion shielding effect cannot be obtained. Inferior to

On the other hand, if the supply amount of clay mineral powder is less than 50 kg per 1 m ^{3 of} earth and sand in the subsequent stirring, the strength and water impermeability of the impermeable wall will not be sufficiently increased, and if it exceeds 200 kg, the effect will reach its peak. Inferior in economic efficiency.

Further, in the subsequent stirring, if the supply amount of the ion shielding agent is less than 0.5 kg per 1 m ^{3 of} earth and sand, a sufficient ion shielding effect cannot be obtained. Inferior to sex.

  In this embodiment, it is more preferable that one or two or more kinds selected from the group consisting of sodium carbonate, caustic soda, water glass, colloidal silica, Na-type zeolite, silica fume, and water-absorbing polymer are used as the ion shielding agent. It will be a thing. Details will be described below.

As a premise, for example, about 34 g of a metal compound “salt” is dissolved in 1 liter of seawater (the salinity of seawater is about 3.4%). Among them, sodium chloride (NaCl), also called salt, is 77.9% (25 g), followed by magnesium chloride (MgCl ₂ ) 9.6%, magnesium sulfate (MgSO ₄ ) 6.1%, calcium sulfate (CaSO ₄ ) 4.0%, potassium chloride (KCl) 2.1%, other 0.3%, chloride ion (Cl ⁻ ) 18.98 g / L, sulfate ion (SO ₄ ²⁻ ) 2.65 g / L Sodium ion (Na ⁺ ) 10.56 g / L, potassium ion (K ⁺ ) 0.38 g / L, magnesium ion (Mg ²⁺ ) 1.27 g / L, calcium ion (Ca ²⁺ ) 0.4 g / L It becomes. Among these ions (electrolytes), it is magnesium ions that cause the most deterioration of the impermeable walls constructed using clay minerals containing smectite.

[Sodium carbonate]
When sodium carbonate is supplied to seawater in which calcium ions and magnesium ions as electrolytes are dissolved, the following reaction is shown.
Na ₂ CO ₃ + Ca ²⁺ , Mg ²⁺ → CaCO ₃ , MgCO ₃ + 2Na ⁺
Since CaCO ₃ has a very low solubility of 0.0015 g / 100 g of water (25 ° C.), most of the calcium ions are inactivated by the supply of sodium carbonate.

[caustic soda]
When caustic soda is supplied to seawater in which calcium ions and magnesium ions as electrolytes are dissolved, the following reaction is shown.
NaOH + Ca ²⁺ , Mg ²⁺ → Ca (OH) ₂ , Mg (OH) ₂ + 2Na ⁺
Since Mg (OH) ₂ has a very low solubility of 0.0009 g / 100 g of water (17 ° C.), most of the magnesium ions are inactivated by the supply of caustic soda.

[Sodium carbonate and caustic soda]
MgCO ₃ has a solubility of 0.1518 g / 100 g of water (19 ° C.), and Ca (OH) ₂ has a solubility of 0.185 (0 ° C.), both of which have a relatively high solubility. Therefore, it is more preferable to use both sodium carbonate and caustic soda. Table 1 shows the concentrations of magnesium ions and calcium ions when sodium carbonate and caustic soda are supplied to seawater.

[Water glass]
(Physical effect)
When water glass (sodium silicate) is supplied to seawater in which alkaline earth metal ions (calcium ions, magnesium ions), which are electrolytes, are dissolved, silicate gel flocs (SiO ₂ ) are generated due to the salting-out effect of the salt in the seawater. Is done. This floc serves as a shielding film, physically preventing the electrolyte from contacting the clay mineral and preventing the water shielding wall from deteriorating. Moreover, since the said floc is filled in the gap | interval in a water-impervious wall, water-improvement improves (sealing effect).

(Chemical effect)
When water glass (sodium silicate) is supplied to seawater in which alkaline earth metal ions (calcium ions, magnesium ions) as electrolytes are dissolved, the following reaction is shown.
Na ₂ O · nSiO ₂ + Ca ²⁺ , Mg ²⁺ → CaO · nSiO ₂ ↓, MgO · nSiO ₂ ↓ + 2Na ⁺
MgO · nSiO ₂ is insoluble, and CaO · nSiO ₂ has a very low solubility of 0.0095 g / 100 g of water (17 ° C.), so that most of magnesium ions and calcium ions are inactivated. become. In addition, sodium ions derived from water glass (alkaline ions) insolubilize alkaline earth metal ions such as calcium ions and magnesium ions as hydroxides, and have the functions of both sodium carbonate and caustic soda. Very excellent in suppressing wall deterioration.

Here, when the molar ratio (SiO ₂ / Na ₂ O) of the supplied water glass is reduced, the chemical effect is increased. Conversely, when the molar ratio of the supplied water glass is increased, the physical effect is increased. Become. From such a viewpoint, the molar ratio of water glass is preferably 0.8 to 4.5, and more preferably 2.0 to 4.0.

[Colloidal silica]
Colloidal silica has a lower alkalinity than water glass. When colloidal silica is supplied, the effect of insolubilizing alkaline earth metal ions (magnesium ions, calcium ions, etc.) by alkali is small compared to when water glass is supplied. Further, since the colloidal particles of silicic acid have a slower reaction than silicic acid in water glass, it is considered that the reactivity with alkaline earth metal ions is low. However, since the colloidal particles are aggregated by salting out, the above physical effect can be expected. Moreover, when the alkalinity is low, it becomes difficult to increase the viscosity of the clay mineral suspension, which is advantageous in terms of construction.

[Na-type zeolite]
Zeolite has a high cation exchange capacity (CEC). For example, the CEC of the artificial zeolite of Maeda Construction Industry is 200 cmol / kg or more. Therefore, when zeolite is supplied, it is considered that alkaline earth metal ions can be adsorbed and removed, and deterioration of the impermeable wall is suppressed.

It should be noted that the amount of zeolite added to adsorb and remove calcium ions (0.4 g) and magnesium ions (1.27 g) in 1 L of seawater is assumed that the cation exchange capacity of the zeolite is 200 cmol / kg. , Magnesium ion equivalent is
1.27 ÷ 24.3 × 2 = 0.104 mol = 10.4 cmol
And the calcium ion equivalent is
0.4 / 40 × 2 = 0.02 mol = 2 cmol
It is. Therefore, the amount of zeolite required to adsorb the total amount of calcium ions and magnesium ions is
1 × (10.4 + 2) ÷ 200 = 0.062kg = 62g
It becomes.

[Silica fume]
Silica fume is very fine spherical silica fine particles having an average particle size of 0.15 μm generated during the production of ferrosilicon, electrofused zirconia, and metallic silicon. When silica fume is supplied, the silica fume is filled in the gaps in the water-impervious wall, so that the water barrier is improved. Moreover, since the improvement of the water shielding leads to a decrease in the amount of contact of the electrolyte with the clay mineral, the deterioration of the water shielding wall is suppressed. Thus, by supplying silica fume, an effect similar to the physical effect (sealing effect) when water glass is supplied can be obtained.

  In addition, as a material having a sealing effect similar to water glass and silica fume, for example, kaolin, fine calcium carbonate, white carbon, silica flower, silical, etc., cellulose-based that dissolves in water and exhibits a clogging effect A pulp, a fiber type, etc. can be mentioned. However, water glass or silica fume is an inorganic substance, is not subject to decomposition by microorganisms or the like, and is a durable material. Therefore, water glass or silica fume is preferable.

[Water-absorbing polymer]
The water-absorbing polymer is made of, for example, a polyacrylic acid-based highly water-absorbing resin that is used as a water-absorbing material such as a diaper. When a water-absorbing polymer is supplied, the polymer absorbs water and exhibits a compaction effect due to volume expansion and a clogging effect that fills the gaps between clay mineral particles with a jelly-like soft material after water absorption. Deterioration of is suppressed.

[Example of construction (single-axis excavator)]
Next, a construction example using a single-axis excavator will be described.
The single-shaft excavator 1 of this embodiment has the entire structure shown in FIGS. That is, the reader 3 supported and installed in front of the base machine 2 has a structure that is supported by the reader cradle 4 and the backstay 5 of the base machine 2. The leader 3 is provided with a long excavation shaft 6 constituted by connecting a plurality of unit excavation shafts in the longitudinal direction so as to be movable in the vertical direction. A power source 7 that slides along the line is mounted. The power of the power source 7 is transmitted to the excavation shaft 6 via the speed reducer 8.

  As the power source 7, a hydraulic motor may be used, but generally an electric motor is often used. This type of electric motor is not limited to one, and a plurality of electric motors can be used. The power from these electric motors is gathered together by a gear train (not shown), and the rotational speed is reduced by a reduction gear 8 and transmitted to the excavation shaft 6.

  As shown in FIG. 4, the excavation shaft 6 is configured by connecting a plurality of unit excavation rods in the longitudinal direction, and has a stirring head 6 a below the excavation head 6 b. . The stirring head 6a is composed of a blade piece, a spiral blade, or the like. Further, a fluid supply source (not shown) for supplying a suspension of clay mineral or ion shielding agent is provided at the upper end of the excavation shaft 6, and these liquid flow paths (see FIG. (Not shown) is formed, and the suspension can be discharged from a first supply port (not shown) at the lower end of the excavation shaft 6.

  Further, a conveying pipe (not shown) is formed in the excavation shaft 6, and a compressor that pneumatically feeds a clay mineral or an ion shielding agent powder to one end of the conveying pipe (not shown). A second delivery port (not shown) for discharging the powder transported to the lower end portion of the excavation shaft 6 is formed by connecting a pressure feeding device (not shown) such as the outside continuously.

  In addition, this kind of single-axis excavation apparatus is well-known, and the apparatus which can be used in constructing the construction method of the impermeable wall which concerns on this invention is not limited to this single-axis excavation apparatus 1. FIG.

(Pattern 1)
The construction method of the impermeable wall using the above single-axis excavation apparatus 1 is demonstrated based on FIG.
First, as shown in FIG. 5 (1), as a first step, the first discharge port at the lower end portion of the excavation shaft 6 using the suspension of the clay mineral and the ion shielding agent as a stable liquid by the single-axis excavator 1 is used. It is discharged from (not shown), and the earth and sand and the suspension are agitated in advance by the agitation head 6a, and the target ground is excavated by the excavation head 6b while preventing collapse of the excavation hole. At this time, according to the present apparatus 1, the excavation by the excavation head 6b and the prior agitation by the agitation head 6a are performed simultaneously, but excavation and agitation are performed separately (with a time difference) by improving the apparatus 1 or the like. This can be done as described above. Further, as described above, the viscous mineral suspension and the ion shielding agent suspension can be supplied separately (with a time difference) without being supplied at the same time.

  Next, as shown in FIG. 5 (2), after excavating to a predetermined depth, as shown in FIG. 5 (3), as a second step, powder of clay mineral and ion shielding agent is excavated. Pneumatically fed by a pressure feeding device (not shown) such as a compressor to a conveying pipe (not shown) formed in the shaft 6 and discharged from a second discharge port (not shown) formed in the excavating shaft 6. Then, the agitation head 6a is rotated, and the excavation shaft 6 is pulled out while the earth and sand, the clay mineral, and the ion shielding agent are agitated afterwards.

  As a result, a water-impervious wall S as shown in FIG. 5 (4) is formed in the target ground G. Although not shown in the figure, this impermeable wall S is usually constructed continuously to form a columnar wall type impermeable wall.

  In addition, although it is possible to use both the liquid flow path for conveying the suspension and the conveyance pipeline for conveying the powder, in order to prevent increase in the viscosity of the powder due to contact with moisture in the pipeline, It is preferable to use another route.

Here, in the second step, the powder of the clay mineral and the ion shielding agent is discharged when the excavation shaft 6 is pulled out in order to delay the increase in viscosity of the clay mineral.
That is, the clay mineral absorbs moisture and increases its viscosity about 30 minutes after contact with water. During that time, water, earth and sand, and powder are agitated later to increase the viscosity. If the excavation shaft 6 is pulled out by the time it comes, a homogeneous stirring can be easily performed in a low-viscosity state and the stirring efficiency is good. After stirring, a water-impervious wall having the same strength as the ground Built. Therefore, the subsequent stirring is not limited to being performed when the excavating shaft 6 is pulled out, and can be performed when the excavating shaft 6 is reinserted, but it is preferable to perform the stirring when pulling out.

(Pattern 2)
As shown in FIG. 10 (1), the pattern 2 is a first step in which the first axis at the lower end of the excavation shaft 6 is treated with a suspension of clay mineral and ion shielding agent as a stable liquid by the single-axis excavator 1. The target ground is excavated by the excavation head 6b while discharging from a discharge port (not shown) and pre-stirring the earth and the suspension by the agitation head 6a to prevent collapse of the excavation hole. At this time, the excavation by the excavation head 6b and the advance agitation by the agitation head 6a can be performed separately (with a time difference) by improving the apparatus 1 or the like, As described above, the suspension of the ion shielding agent can be supplied separately (with a time difference) without being simultaneously supplied.

  Next, as shown in FIG. 10 (2), after excavating to a predetermined depth, as shown in FIG. 10 (3), as a second step, without discharging clay mineral or ion shielding agent, The excavation shaft 6 is pulled out while rotating the stirring head 6a and stirring the earth and sand and the suspension of the clay mineral and the ion shielding agent previously supplied. In addition, when excavating the improved single-axis excavator 1 to a predetermined depth, the excavation by the excavation head 6b and the prior agitation by the agitation head 6a are not performed at the same time but separately (with a time difference). In this embodiment, the pre-stirring with the suspension of the clay mineral or the ion shielding agent is not performed, and the pre-stirring with the suspension of the clay mineral or the ion shielding agent is performed when the single-shaft excavator 1 is pulled out. Conceivable.

  Next, although not shown, as a third step, the clay mineral and the ion shielding agent powder are discharged while the excavation shaft 6 is inserted again into the excavation hole formed in the first step, and this powder is discharged. As shown in FIG. 10 (4), the agitated material and the earth and sand are uniformly stirred to the bottom.

  Next, as shown in FIG. 10 (5), as the fourth step, without stirring the clay mineral and the ion shielding agent, the stirring head 6a is rotated while stirring the earth and sand, the clay mineral, and the ion shielding agent. The excavation shaft 6 may be pulled out. As a result, a water shielding wall S as shown in FIG. 10 (6) is formed in the target ground G. Although not shown in the figure, this impermeable wall S is usually constructed continuously to form a columnar wall type impermeable wall.

(Other)
In addition to the above, various forms can be considered for the construction method of the impermeable wall using the single-axis excavator 1. Specifically, for example, the clay and mineral suspension are discharged from the first discharge port (not shown) at the lower end of the excavation shaft 6 as a stable liquid by using the single-axis excavator 1 as a clay mineral suspension. Are agitated in advance by the agitating head 6a, and the target ground is excavated by the excavating head 6b while preventing the excavation hole from collapsing. After excavation to a predetermined depth, the ion shielding agent is ejected from a first discharge port (not shown) at the lower end of the excavation shaft 6, and the earth and sand, the ion shielding agent, and the previously supplied clay mineral are agitated. The excavation shaft 6 is pulled out with prior stirring by the head 6a. Next, while the excavation shaft 6 is reinserted into the excavation hole formed by the above steps, only the subsequent agitation is performed by the agitation head 6a, or the powder of clay mineral and ion shielding agent is discharged, and this powder Stir the body and earth and sand uniformly to the bottom. Then, the clay mineral and the ion shielding agent are discharged, the agitation head 6a is rotated, and the excavation shaft 6 is pulled out while stirring the earth and sand, the clay mineral, and the ion shielding agent. As a result, the impermeable wall S is formed in the target ground G.

[Example of construction (multi-axis excavator)]
Next, an example of construction using a multi-axis excavator will be described mainly, particularly when a triaxial excavator is used.
The triaxial excavator 11 has, for example, the entire structure shown in FIG. The difference from the single-axis excavator 1 is that, as shown in FIG. 7, the excavation shaft 12 is composed of three excavation shafts, and is arranged so as to sandwich the central excavation shaft 13 and both sides of the central excavation shaft 13. The side end excavation shafts 14a and 14b. Therefore, since the configuration other than that is the same as the configuration of the single-axis excavator 1, only the configuration of the excavating shaft 12 is described, and the description of the other configuration is omitted.

  The central excavation shaft 13 and the side end excavation shafts 14a and 14b are each configured by connecting a plurality of unit excavation rods in the longitudinal direction, and have a stirring head 15 below the excavation head 16 at the lower end. It is attached. The stirring head 15 is constituted by a blade piece or a spiral blade. A fluid supply source (not shown) for supplying a suspension of clay mineral or ion shielding agent is provided at the upper ends of the central excavation shaft 13 and the side end excavation shafts 14a and 14b. 13. These liquid flow paths (not shown) are formed in the side end excavation shafts 14a and 14b, and the first excavation is formed on the side surfaces at the lower ends of the central excavation shaft 13 and the side end excavation shafts 14a and 14b. From the discharge port 17, a suspension of clay mineral or ion shielding agent can be discharged. Therefore, in this case, the first discharge port 17 rotates with the rotation of the central excavation shaft 13 and the side end excavation shafts 14a and 14b, and the suspension of the clay mineral and the ion shielding agent from the fluid supply source is rotationally jetted. Will be. Needless to say, the height of the first discharge port 17 is optimal at the lower end, but it can also be provided on the upper side. Further, the liquid flow path (not shown) up to the first discharge port 17 can pass outside the shaft without passing through the central excavation shaft 13 and the side end excavation shafts 14a and 14b as in the above example.

  Further, a conveyance pipe line (not shown) is formed in the central excavation shaft 13 and the side end excavation axes 14a and 14b, and one end of the conveyance pipe line (not shown) shields clay minerals and ions. A pumping device (not shown) such as a compressor that pneumatically feeds the powder of the agent is connected to the outside, and the clay mineral or ion shielding agent conveyed to the lower end of the central excavation shaft 13 and the side end excavation shafts 14a and 14b. A second discharge port 18 for discharging the powder is formed.

  In addition, this kind of triaxial excavator is well-known, and the construction method of the impermeable wall which concerns on this invention is not limited to use of this triaxial excavator 11. FIG.

As an example of construction using the above-described triaxial excavator 11, a method corresponding to the pattern 1 when the single-axis excavator 1 is used can be exemplified.
Although this method is not illustrated, first, as a first step, the first discharge port of the side end excavation shafts 14a, 14b is made by using the triaxial excavator 11 as a stabilizing liquid with a suspension of clay mineral and ion shielding agent. 17, the earth and sand and the suspension are preliminarily agitated by the agitation head 15 to prevent the auxiliary excavation hole from collapsing, and the excavation head 16 moves the target ground to the main excavation by the central excavation shaft 13. Prior to this, auxiliary excavation is performed by the side end excavation shafts 14a and 14b. Then, when the central excavation shaft 13 that follows this penetrates the target ground, a suspension of clay mineral and ion shielding agent is also discharged from the first discharge port 17 of the central excavation shaft 13, and the side end excavation shaft 14a. , 14b and the main excavation are performed. At this time, the triaxial excavator 11 is improved so that the excavation by the excavation head 16 and the prior agitation by the agitation head 15 are not performed at the same time, but separately (with a time difference), or the suspension of the viscous mineral As described above, the ion shielding agent suspension and the ion shielding agent suspension can be supplied separately (with a time difference). The suspension of the viscous mineral is discharged from the first discharge port 17 of the side end excavation shafts 14a and 14b, and the suspension of the ion shielding agent is discharged from the first discharge port 17 of the central excavation shaft 13. However, from the viewpoint of uniforming the properties of the impermeable walls to be constructed, it is preferable not to separate them by the excavation shaft in this way.

  After excavation to a predetermined depth, as a second step, the clay mineral and the ion shielding agent powder are transported through the central excavation shaft 13 and the side end excavation shafts 14a and 14b (not shown). ) Is pneumatically fed by a pressure feeding device (not shown) such as a compressor, and the stirring head 15 is rotated while being discharged from the second discharge port 18 formed in the central excavation shaft 13 and the side end excavation shafts 14a and 14b. The central excavation shaft 13 and the side end excavation shafts 14a and 14b are pulled out while the earth and sand, the clay mineral, and the ion shielding agent are stirred backward.

  As a result, a columnar impermeable wall is formed in the target ground. Although not shown in the figure, this impermeable wall is usually constructed continuously to form a columnar wall type impermeable wall.

  It is possible to use both the liquid flow path for transporting the suspension of clay mineral and ion shielding agent and the transport path for transporting the powder of clay mineral and ion shielding agent. In order to prevent an increase in the viscosity of the powder due to contact with moisture, it is preferable to use another route.

Here, in the second step, the powder of the clay mineral or the ion shielding agent is discharged when the central excavation shaft 13 and the side end excavation shafts 14a and 14b are pulled out in order to delay the increase in viscosity of the clay mineral. .
That is, the clay mineral absorbs moisture and increases its viscosity about 30 minutes after contact with water. During this period, the water, earth and sand, clay mineral, and ion shielding agent are stirred, and the viscosity is increased. If the central excavation shaft 13 and the side end excavation shafts 14a and 14b are withdrawn before the increase in the amount of water, homogenous agitation can be easily performed in a low viscosity state and the agitation efficiency is good. A water-impervious wall with the same strength as is constructed. Therefore, the subsequent agitation is not limited to being performed when the central excavation shaft 13 and the side end excavation shafts 14a and 14b are pulled out, and can be performed at the time of re-insertion, but is preferably performed at the time of pulling out.

  Various modifications of the discharge method of the clay mineral and the ion shielding agent by the triaxial excavator 11 can be considered. For example, in the preceding stirring stage, the suspension is discharged only from the first discharge port 17 of the side end excavation shafts 14a and 14b, and in the drawing stage, the powder is discharged from only the second discharge port 18 of the central excavation shaft 13. It is also possible to make it.

  In addition, although the three-axis drilling apparatus was demonstrated above, for example, it is applicable also to the drilling apparatus which has four axes | shafts, five axes | shafts, six axes | shafts, or more. The description of the method corresponding to the single-axis excavation pattern 2 described above is substantially the same as that of the single-axis excavation pattern 2, and thus the description thereof is omitted.

[Example of construction (chain cutter excavator)]
The chain cutter excavator 21 has an overall structure shown in FIGS. 8 (1) and 8 (2). 8 (1) is a side view of the chain cutter excavator 21, and FIG. 8 (2) is a front view thereof. The reader 23 supported and installed in front of the base machine 22 has a structure that is supported by a reader cradle 24 and a backstay 25 of the base machine 22. The leader 23 is provided with a guide post 28 formed by connecting a plurality of unit guide posts for guiding an endless chain 27 constituting a part of the cutter 26 in the longitudinal direction so as to be movable in the vertical direction. A power source 29 such as an electric motor that slides along the reader 3 is mounted on the head of the guide post 28. The power of the power source 29 is transmitted to an endless chain 27 described later via a chain drive drive wheel (not shown).

  The cutter 26 includes a guide post 28, a chain drive drive wheel (not shown), a chain sprocket 30, an endless chain 27, a plurality of cutter bits (not shown), and a stirring bar (not shown). Yes. The guide post 28 is provided with a chain drive wheel (not shown) at the top and a chain sprocket 30 pivotally or pivotally supported at the bottom of the lowermost guide post 28a. An endless chain 27 is wound around the drive wheel and chain sprocket 30, and a plurality of cutter bits (not shown) and agitation bars (not shown) are alternately arranged on the endless chain 27. Has been. The endless chain 27 is rotated by a power from a power source 29 via a chain driving drive wheel.

  In addition, a liquid flow path (not shown) for conveying a suspension of clay mineral and ion shielding agent supplied from a fluid supply source (not shown) provided outside is formed in the guide post 28. The suspension of clay mineral or ion shielding agent can be discharged from a first discharge port (not shown) at the lower part of the lowermost guide post 28a.

  Further, a conveyance pipe line (not shown) is formed in the guide post 28, and a compressor for pneumatically feeding clay mineral or ion shielding agent powder to one end of the conveyance pipe line (not shown). A second discharge port (not shown) for discharging the conveyed clay mineral or ion shielding agent powder is provided below the lowermost guide post 28a. Is formed.

  In addition, this kind of chain cutter type excavator 21 is well-known, and the construction method of the impermeable wall which concerns on this invention can also be implemented using apparatuses other than the chain cutter type excavator 21. FIG. Further, the first and second discharge ports are preferably formed in the lowermost guide post 28a, but may be formed in the guide posts 28, 28.

(Pattern 1)
A construction method of the impermeable wall S using the chain cutter excavator 21 will be described with reference to FIG.
First, as shown in FIG. 9 (1), the cutter 26 is inserted into a drilling hole that has been drilled to a predetermined depth in advance, or the unit guide posts are sequentially connected to perform the self-building to a predetermined depth. Cutter 26 is built in the ground. Then, as shown in FIG. 9 (2), as the first step, while moving the base machine 22 from the cutter mounting position in the direction of the arrow (outward) (right direction on the paper surface), the clay mineral and the ion shielding agent The suspension is discharged as a stable liquid from a first discharge port (not shown) below the lowermost guide post 28a, and the suspension of earth and sand and clay mineral or ion shielding agent is pre-stirred by a stirring bar. Then, the target ground G is excavated with the cutter bit while preventing the collapse of the excavation groove.

  After excavating the groove to a predetermined length, as shown in FIG. 9 (3), as a second step, the clay mineral and the ion shielding agent powder are discharged from a second discharge port (not shown). While rotating the agitation bar, the base machine 22 is moved in the direction of the arrow (return path) (to the left in the drawing) toward the starting position of the cutter while stirring the earth and sand, clay mineral, and ion shielding agent. After returning to the cutter built-in position, the cutter 26 is pulled out. As a result, as shown in FIG. 9 (4), the impermeable wall S which is a continuous wall is constructed in the groove excavated portion.

  It is possible to use both the liquid flow path for transporting the suspension of clay mineral and ion shielding agent and the transport path for transporting the powder of clay mineral and ion shielding agent. In order to prevent an increase in the viscosity of the powder due to contact with moisture, it is preferable to use another route.

Here, in the second step, when the base machine 22 moves in the return path, the powder of the clay mineral or the ion shielding agent is discharged in order to delay the viscosity increase of the clay mineral.
That is, the clay mineral absorbs moisture and increases its viscosity about 30 minutes after contact with water. During this period, the water, earth and sand, clay mineral, and ion shielding agent are stirred, and the viscosity is increased. If the cutter 26 is pulled out after returning to the position where the cutter is built up until the increase in the number of the cutters, the homogenous stirring can be easily performed in the low viscosity state and the stirring efficiency is good. The underground impermeable wall S having the same strength as the ground is constructed.

(Pattern 2)
As shown in FIG. 11 (1), the pattern 2 has a first construction area start point as the first process area as the first process area as shown in FIG. 11 (2). The base machine 22 is moved in the direction of the arrow (outward) (right direction on the paper) and the suspension of the clay mineral and the ion shielding agent is guided to the bottom end while the groove is excavated to the end of the primary work area of a predetermined length. The cutter bit is discharged from a first discharge port (not shown) below the post 28a, and the earth and sand and the suspension of clay mineral or ion shielding agent are pre-stirred to prevent the collapse of the excavation groove and the like. Then, the target ground is excavated.

  As the second step, as shown in FIG. 11 (3), the base machine 22 returns to the primary work area start point from the primary work area end point without discharging the clay mineral and the ion shielding agent. Only further stirring of the stirring earth and sand stirred by the process is performed.

  As a third step, after returning to the primary work area start point, as shown in FIG. 11 (4), while moving again toward the primary work area end point, from the primary work area start point to the primary work area end point. 11 discharges the powder of the clay mineral and the ion shielding agent, stirs the clay mineral and the ion shielding agent and the earth and sand, and shows the end point of the primary work area as the start point of the secondary work area as shown in FIG. 11 (5). As described above, from the start point of the secondary work area to the end point of the secondary work area of a predetermined length, the suspension of the clay mineral and the ion shielding agent is poured into the first discharge at the lower part of the lowermost guide post 28a while excavating the groove. The target ground is excavated with a cutter bit while discharging from an outlet (not shown) and pre-stirring the sediment and the suspension of clay mineral or ion shielding agent to prevent the excavation groove from collapsing.

  And although not shown in figure, the underground water-impervious wall of all the work areas is constructed by repeating the said 2nd process and a 3rd process one by one by making the preceding work area end point into a subsequent work area start point. Others are substantially the same as those of the pattern 1, and thus the description thereof is omitted.

(Other)
In addition to the above, various forms can be considered for the construction method of the impermeable wall using the chain cutter excavator 21. Specifically, for example, when the base machine 22 is moved forward, a clay mineral suspension is supplied, and when the base machine 22 is moved backward, an ion shielding agent is supplied. The form etc. which supply the powder and powder of an ion shielding agent can be considered.

Next, examples of the present invention will be described.
As shown in Table 2, a test was conducted to measure the water permeability coefficient by changing clay minerals and ion shielding agents. The details of the supply method, measurement method, etc. are as follows.

(Supply method)
2: Corresponds to method (2) in FIG. 1, 3: method (3) in FIG. 1, 7: method (7) in FIG.

(Clay mineral)
[Kunigel]
Dry sand: 1740 kg, seawater (dilution ratio): 348 L (2 times), supply amount: 100 L (10%), brand: Kunigel V-1.

[Hydrogel]
Dry sand: 1740 kg, seawater (dilution ratio): 348 L (2 times), supply amount: 100 L (7%), brand: Hydrogel.

[Gunma 1]
Dry sand: 1740 kg, seawater (dilution ratio): 348 L (double), supply amount: 100 L (10%), brand: Gunma bentonite.

[Gunma 2]
Dry sand: 1740 kg, seawater (dilution ratio): 348 L (4 times), supply amount: 100 L (10%), brand: Gunma bentonite.

[Clay minerals in subsequent stirring]
The clay mineral in the subsequent stirring is the same as the clay mineral in the preceding stirring.

(Measuring method)
Test Nos. 1 to 22: Measured in accordance with the water level permeability test specified in JIS A 1218: 1998 (JGS 0311-2000).

  Test Nos. 23 to 55: Measured according to the standard measurement method (Method B) of water permeability of a porous material in a saturated state using a water permeability test apparatus using a flexible membrane specified in American Society for Testing and Materials ASTM D5084-03 did.

  In Table 2, the obtained water permeability coefficient has some influence due to the difference in the test method and the test days, but supplies the ion shielding agent A and the ion shielding agent B rather than supplying only the ion shielding agent A relatively. It is preferable that the supply of the ion shielding agent is more effective in the preceding stirring than in the subsequent stirring. However, if the supplying is performed in the subsequent stirring, a larger effect can be obtained. There is also a difference in particle size and swelling degree, and it can be seen that the value varies depending on this difference.

  The present invention is applicable as a method for constructing a water-impervious wall using a clay mineral containing smectite such as bentonite.

It is a figure for demonstrating the supply method of an ion shielding agent. It is a side view of a single axis excavator. It is a front view of a single axis excavator. It is a front view of the tip part of a single axis excavation axis. It is a figure for demonstrating excavation and a stirring process. It is a front view of a triaxial excavator. It is a front view of the front-end | tip part of the excavation shaft of a triaxial excavator. It is the side view and front view of a chain cutter type excavator. It is a figure for demonstrating the excavation and stirring process using a chain cutter type excavation apparatus. It is a figure for demonstrating the excavation and stirring process using a single-axis excavation apparatus. It is a figure for demonstrating the excavation and stirring process using a chain cutter type excavation apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Single-axis drilling device, 2 ... Base machine, 3 ... Leader, 4 ... Reader cradle, 5 ... Backstay, 6 ... Drilling shaft, 6a ... Agitation head, 6b ... Excavation head, 7 ... Power source, 11 ... Three Axis excavator, 12 ... excavation axis, 13 ... central excavation axis, 14a, 14b ... side end excavation axis, 15 ... agitation head, 16 ... excavation head, 17 ... first discharge port, 18 ... second discharge port, DESCRIPTION OF SYMBOLS 21 ... Chain cutter type excavator, 22 ... Base machine, 23 ... Leader, 24 ... Leader cradle, 25 ... Backstay, 26 ... Cutter, 27 ... Endless chain, 28 ... Guide post, 28 ... Lowermost guide post, 29 ... Power source, 30 ... Chain sprocket, G ... Target ground, S ... Water impervious wall.

Claims (4)

Suspension of clay mineral containing smectite is supplied to the soil in the ground formed by excavation of the target ground and pre-stirred, and clay mineral powder containing smectite is added to the pre-stirred soil and sand. A method for constructing a water-impervious wall, comprising supplying and agitating downstream, and using the earth and sand subjected to the subsequent agitation as a water-impervious wall,
Among the preceding stirring and the subsequent stirring, at least in the preceding stirring, an ion shielding agent is supplied to the earth and sand ,
As an ion shielding agent in the preceding stirring,
Using sodium carbonate and caustic soda,
These supplies are performed in the order of the sodium carbonate and the caustic soda after the clay mineral is supplied.
The construction method of the impermeable wall characterized by the above-mentioned. Supplying the ion shielding agent;
In the state of suspension in the preceding stirring, and in the state of powder in the subsequent stirring.
The construction method of the impermeable wall according to claim 1. The ion shielding agent is supplied in the preceding stirring after the clay mineral is supplied.
The construction method of the impermeable wall of Claim 1 or Claim 2. As the clay mineral suspension, water containing 50 to 200 kg of the clay mineral in 1000 L of water is used. In the preceding stirring, 50 to 200 L of the clay mineral suspension is supplied per 1 m ^{3 of the} earth and sand, And 0.5 to 20 kg of the ion shielding agent is supplied,
On the other hand, in the subsequent stirring, 50 to 200 kg of the clay mineral powder is supplied per 1 m ^{3 of the} earth and sand, and 0.5 to 20 kg of the ion shielding agent is supplied.
The construction method of the impermeable wall according to any one of claims 1 to 3 .

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