JP2018053701A - Fluidized sand and method for producing the same, and ground improvement method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve properties with time as fluidized sand produced by mixed with an additive for ion charge neutralization even in a sand material that is difficult to apply a press-in type sand pile construction method and a sand filling method, and to enable the methods to be applied to the sand material.SOLUTION: In fluidized sand for ground improvement which is obtained by adding not only water content adjustment water but also a fluidization agent to a sand material and is treated so as to be capable of being transferred through piping by a pressure pump, an additive for ion charge neutralization, which can neutralize cation such as a metal ion that is contained in the sand material and becomes a hindrance factor of the fluidizing agent, is mixed, and then the fluidization agent is mixed into the resultant substance. The method for producing the fluidized sand includes mixing the sand material with the additive for ion charge neutralization and then mixing the fluidizing agent, the water content adjustment water and a slow acting plasticizing agent, into the resultant substance.SELECTED DRAWING: Figure 1

Description

  The present invention is a fluidized sand in which a fluidizing agent is mixed with a sand material used for ground improvement and is in a pumpable state, a manufacturing method thereof, and a ground improvement method such as press-fit sand pile formation and sand filling using the same. About.

  Among the ground improvement methods, the sand compaction pile method (SCP method) is often used as a countermeasure for liquefaction, and increases the density of the ground by creating a compacted sand pile in the ground. In this SCP method, since a large construction machine is used, there are many cases where it cannot be applied due to restrictions in securing a construction space. As an alternative construction method, a chemical solution injection system using a small construction machine or a method of press-fitting cement mortar may be applied, but the cost becomes high. In addition, a construction method that enables the use of material sand, which is a natural material that can reduce the environmental burden, has been desired. From such a background, as disclosed in Patent Documents 1 and 2, the present applicants put the material sand into a fluidized state that can be pumped by a pump, and press-fit into the ground to reduce costs and reduce environmental impact. A press-in sand pile construction method that enables reduction has been developed and put into practical use. This construction method is called sand press-fit static compaction construction method or SAVE-SP construction method (registered trademark), and can be applied to construction in confined areas and improvement directly under existing structures by using a small construction machine.

  Patent document 1 is disclosing the basics of a press-in type sand pile construction method. In this construction method, a sand pile material fluidized material (hereinafter referred to as fluidized sand) containing a fluidizing agent and a slow-acting plasticizing agent together with water content adjustment water in the material sand is retained in the ground while maintaining the fluidized state. Press fit and plasticize in the ground. As shown in FIG. 11, the details are as follows. After the hollow tube 23 has penetrated into the ground to the design depth, the fluidized sand is pressed into the ground from the surface through the hollow tube 23, and the fluidized sand enters the ground. The fluidized sand for the next step is press-fitted on this, and the improved body 25 having a predetermined length is formed by repeating this. Reference numeral 10 denotes a fluidized sand production plant, 1 a fluidized sand supply means, 2 a sand material supply means, 3 a fluidizing agent supply means, 4 a pressure feed pump, and 5 a slow-acting plasticizer supply apparatus.

  Patent Document 2 discloses a fluidized sand production plant. In this production plant, a fluidizing agent is mixed with material sand to produce fluidized sand. The fluidized sand is mixed with sand material in the order of water, fluidizing agent, and slow-acting plasticizer. Preferably, the fluidized sand measures the weight of the sand material, and based on the weight, water, a fluidizing agent, and a slow-acting plasticizer are automatically calculated and mixed.

  FIG. 12 is a schematic diagram showing changes in the state of fluidized sand during construction. (A) shows fluidized sand before press-fitting. Until the fluidized sand is pressed into the ground from the hollow tube, the fluidizing agent (for example, an anionic polymer material) increases the viscosity of the pore water between the sand particles and eliminates the friction between the particles. Suppresses separation from water and maintains high fluidity. (B) shows fluidized sand during press-fitting. During the press-fitting, the fluidized sand is dehydrated and compacted into a dense state. The fluidizer remains reticulated. (C) shows the plasticized end state. In this state, the slow-acting plasticizing agent electrically neutralizes the fluidizing agent so that the network structure of the fluidizing agent cannot be maintained, and the friction between the particles is recovered.

Japanese Patent No. 5188894 Japanese Patent No. 5189951

  In the press-fit sand pile construction method using fluidized sand, a hollow tube having a diameter of about 100 to 200 mm is used, and an improved body having a diameter of about 500 to 700 mm is often created by injecting fluidized sand into the ground. . At the time of construction, the characteristics of the target ground are ascertained by a preliminary survey, and selection of material sand and formulation specifications are determined accordingly, and the produced fluidized sand can be applied through table flow tests, bleeding tests, and texture tests. Judgment is made and whether or not it is usable is determined. In addition, regarding the material sand of the raw material, a usable range is set based on the particle size distribution and the like.

  However, in practice, the material sand that is within the specified range may have a high penetration resistance at an early stage and may be difficult to apply. That is, depending on the material sand to be used, when it is pressed into the ground as fluidized sand, the pressure increases in a short time or the pumping loss increases and the press-fit amount does not reach the target value. The applicant has investigated the cause, but as a main factor, the target value is obtained when a cation such as a metal ion contained in the material sand and a polymer material as a fluidizing agent react with each other or influence each other. On the other hand, it is considered that the performance deteriorates rapidly.

  As a result of studying measures to prevent such a sudden change in properties as described above, the present applicant has found that cations such as metal ions, which are inhibiting factors, can be eliminated chemically or chemically physically, leading to the present invention. It was. The object of the present invention is to provide a time-dependent change to fluidized sand produced by mixing an additive for neutralizing ionic charge even with material sand that is difficult to apply when applying the press-fitting sand pile construction method or sand filling method. It is to improve the properties and make it applicable. Other or specific purposes will be clarified in the following description.

  In order to achieve the above-mentioned object, the invention according to claim 1 is the fluidized sand for ground improvement, wherein a fluidizing agent is added to the material sand together with water for adjusting the water content ratio, and the material sand is processed so as to be transportable through a pipe by a pressure pump. In contrast, after mixing an additive for neutralizing an ionic charge that can neutralize a cation such as a metal ion contained in the material sand, which is an inhibiting factor of the fluidizing agent, the fluidizing agent is mixed. It is characterized by being.

In the above invention, as a cation such as a metal ion that becomes an inhibiting factor of the fluidizing agent contained in the material sand, in particular, a metal ion having a valence of 2 or more, such as calcium ion (Ca ²⁺ ), magnesium ion (Mg ²⁺ ) ^Examples thereof include iron ions (Fe ²⁺ , Fe ³⁺ ) and aluminum ions (Al ³⁺ ). On the other hand, the ionic charge neutralizing additive is an inorganic charge neutralizing agent such as sodium hydrogen carbonate, or an organic charge neutralizing agent such as tetrasodium imidosuccinate. These points will be described later.

The above-mentioned present invention is more preferably embodied as follows. That is,
First, the ionic charge neutralizing additive includes sodium bicarbonate (NaHCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), sodium tripolyphosphate (Na ₅ P ₃ HCO ₁₀ ), sodium polyacrylate (C It is an inorganic charge neutralizing agent such as ₃ H ₃ NaO ₂ ) _n (Claim 2).
Second, the ionic charge neutralizing additives, 3- hydroxybenzoic 2,2' iminodisuccinic acid tetrasodium _{(C 8 H 7 NO 9 ·} 4Na), tetrasodium ethylenediaminetetraacetate tetrahydrate _{(C 10} H a _{12 N 2 O 8 Na 4 ·} 4H 2 O) the organic charge neutralizing agents such (claim 3). The organic charge neutralizing agent is generally called a chelating agent, and may also be called an organic charge retarder.

  Thirdly, the fluidized sand has a configuration in which the penetration stress value of the fluidized sand is at least about 6,000 (Pa) at least 1 hour after the creation of the texture test (Claim 4).

  On the other hand, the invention according to claim 5 is the fluidized sand manufacturing method according to any one of claims 1 to 4, wherein the ionic charge neutralizing additive is mixed into the material sand, and then the fluidized sand is mixed. It is characterized by mixing the agent, water content adjustment water and slow-acting plasticizer.

  On the other hand, the invention of claim 6 is a ground improvement method such as press-fitting sand pile formation or sand filling, and the fluidized sand according to any one of claims 1 to 5 is penetrated into the ground through a pipe by a pump. It is characterized in that it is pumped to a hollow tube to be pulled out, pressed into the ground from the tip side of the hollow tube, and plasticized in the ground.

  According to the first aspect of the present invention, an ionic charge neutralizing additive capable of charge neutralizing a cation (particularly a divalent or higher-valent metal ion) contained in the material sand is mixed with the raw material material sand. By mixing the agent, the time-dependent properties of the fluidized sand are improved, and normal press-fitting work can be maintained. In this case, from various tests, it is important to mix the ionic charge neutralizing additive with the raw material sand. It can be improved by mixing the material sand with the fluidizing agent or after mixing the fluidizing agent. The effect cannot be expected so much. This indicates that it is essential to eliminate or suppress the inhibiting factor in advance by mixing the additive for ionic charge neutralization with the material sand before mixing the fluidizing agent with the material sand.

  As described above, the fluidized sand of the present invention can be used as material sand of raw material, which is unapplicable despite satisfying the prescribed range such as particle size distribution, The application range of the material sand to be used can be expanded, and it can contribute to the expansion of application opportunities of the ground improvement method using fluidized sand as well as cost reduction.

  In the invention of claim 2, as the ionic charge neutralizing additive, as is apparent from the test examples described later, an inorganic charge neutralizing agent such as sodium hydrogen carbonate, sodium carbonate, sodium tripolyphosphate, sodium hexametaphosphate is used as a raw material. By mixing it with the material sand, it is possible to reliably improve the property inhibiting factor of the fluidized sand by reacting or suppressing it.

  In the invention of claim 3, as the ionic charge neutralizing additive, as will be apparent from the following test examples, organic charges such as tetrasodium 3-hydroxy-2,2′-iminodisuccinate, tetrasodium ethylenediaminetetraacetate tetrahydrate, etc. By mixing the neutralizing agent with the raw material sand, the property inhibiting factor of the fluidized sand can be reliably improved by reaction or suppression action.

  In the invention of claim 4, as the properties of the fluidized sand after the improvement, the particularly important penetration stress, that is, the penetration stress of the fluidized sand after one hour from the texture test is improved to 6,000 (Pa) or less. This is a specific point. This value is meaningful in clearly specifying that it satisfies the standard value that is considered preferable in the current implementation.

  In the invention of claim 5, in the method for producing fluidized sand according to any one of claims 1 to 4, the ideal composition of the fluidized sand is clarified. Works the same as described.

  In the invention of claim 6, in the ground improvement method such as press-fitting sand pile creation disclosed in Patent Documents 1 and 2 and sand filling disclosed in Japanese Patent No. 5478386, the amount of press-fitting of fluidized sand (material sand) Therefore, the press-fitting construction can always be achieved as designed.

It is a schematic diagram for description which showed the apparatus structure in the case of implementing the press-fit type sand pile construction method and sand filling construction method of this invention. It is a graph which shows a texture test result among the physical-property test results of fluidized sand (example in which the additive for ionic charge neutralization is sodium bicarbonate) to which the present invention is applied. It is a graph which shows a flow test result among the physical property test results of the fluidized sand (example in which the additive for ionic charge neutralization is sodium bicarbonate) used in FIG. It is a graph which shows a texture test result among the physical-property test results of the fluidization sand (example in which the additive for ionic charge neutralization is sodium carbonate) to which the present invention is applied. It is a graph which shows a texture test result among the physical-property test results of the fluidization sand (example in which the additive for ionic charge neutralization is sodium tripolyphosphate) to which the present invention is applied. It is a graph which shows a texture test result among the physical-property test results of the fluidized sand to which this invention is applied (the additive for ionic charge neutralization is sodium polyacrylate). It is a graph which shows a texture test result among the physical-property test results of fluidized sand (example in which the additive for ionic charge neutralization is sodium hexametaphosphate) to which the present invention is applied. It is a graph which shows a texture test result among the physical-property test results of fluidized sand to which the present invention is applied (an example in which the additive for ionic charge neutralization is HIDS). It is a graph which shows a flow test result among the physical property test results of the fluidized sand (example in which the additive for ionic charge neutralization is HIDS) used in FIG. It is a graph which shows a texture test result among the physical-property test results of fluidized sand to which the present invention is applied (an example in which the additive for ionic charge neutralization is Kirest OD). It is explanatory drawing which shows the sand pile production apparatus currently disclosed by patent document 1. FIG. (A)-(c) is explanatory drawing which shows the state change of the fluidization sand at the time of construction.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. In this explanation, the construction machine used in the sand press-fit static compaction method and the sand filling method, the fluidized sand production plant, the fluidized sand production method, and the sand press-fit static compaction method that is the ground improvement method are described. Then, physical property test results of fluidized sand produced in Examples 1 to 5 as Test Example 1 and Examples 6 and 7 as Test Example 2 will be described.

(Ground improvement method) The construction machine used in the ground improvement method of the present invention can be broadly divided into a crawler type that vertically penetrates or pulls out a hollow tube along a leader, and a hollow tube suspended from an auxiliary crane. There are a boring machine type that penetrates and pulls out in a state and a rotary percussion drill type that penetrates and pulls out a hollow tube at an arbitrary angle, and it is selected according to the target ground and construction depth.

  FIG. 1 shows an example of a small crawler type construction machine 1, schematically showing a fluidized sand production plant 2. The construction machine 1 includes an elevating mechanism 4 that moves the hollow tube 3 up and down, a rotating mechanism 5 that is held by the elevating mechanism 4 and rotates the hollow tube 3, and a swivel provided at the upper end 3a of the hollow tube. 15, a pump P for pumping the fluidized sand produced in the production plant 2, a pipe 16 connecting the outlet of the pump P and the swivel 15, and a pump 16 provided in the middle of the pipe 16. A pressure gauge 6 for detecting the pressure of fluidized sand is provided.

  Here, the elevating mechanism 4 is moved up and down via a rack and pinion mechanism or the like along one side of the columnar leader 12 erected so as to be movable by the base machine 10. The rotating mechanism 5 is moved up and down along the leader 12 by the elevating mechanism 4 and forwardly and reversely rotates the hollow tube 3 via a motor and a reduction gear mechanism. The base machine 10 positions and holds the lower end side of the leader 12 in front of the cab 11, and a hydraulic device, an electric motor, and the like not shown are mounted on the rear side of the cab 11. In the cab 11, various construction operation units and control units are arranged. The leader 12 is supported by a raised cylinder 13 or the like, and is attached to the lower side to restrain the swinging of the hollow tube 3, and the guide tool 17 is attached to the upper side to support the upper side of the pipe line 16. Etc. The upper end of the pipe line 16 is connected to the upper end 3 a of the hollow pipe 3 through the swivel 15.

  As for the pump P, a pumping structure using a hydraulic piston is selected as a pump P that does not cause particularly high suction force, confidentiality, and air suction, and can keep the change in fluidized sand property low. The pump drive is automatically controlled via a control unit arranged in the cab 11 or controlled by the operator. The pressure gauge 6 detects the pressure of the fluidized sand being pumped by the pump P, and is pressed into the ground side region from the lower end opening of the hollow tube 3, that is, the portion where the density is lowered by drawing the hollow tube and the periphery thereof. It is possible to estimate the press-fitting pressure of the fluid when And the pressure gauge 6 detects the pressure at the time of pumping of fluidized sand at the time of construction, and transmits the detection signal to the control part of the cab 11. In the control unit, the pump P stops driving when the set pressure is reached as the fluid pressure based on the detection signal.

(Fluidized sand production plant) This production plant 2 is mainly composed of a production apparatus 20 having a mixing chamber 21 and an agitator chamber 22 and the like, and sand supply means 23 such as a backhoe for feeding sand material 7 into the mixing chamber 21. , An additive supply means 24 for supplying an ion charge neutralizing additive, a fluidizing agent supply means 25 for supplying a fluidizing agent, a water supply means 26 for supplying water for adjusting the water content, and a plasticizing agent. A plasticizer supply means 27 is provided.

  When applying the sand press-fit type static compaction method, material sand selection and blending specifications are determined according to the characteristics of the target ground through a preliminary survey. In the production plant 2, the intended fluidized sand is normally produced in the mixing chamber 21 for each batch (improved body 9). Sand supplied by the sand supply means 23, ionic charge neutralizing additive supplied by the additive supply means 24, fluidizing agent supplied by the fluidizing agent supply means 25, water supply means 26 The selection criteria and action of the plasticizer supplied by the water and plasticizer supply means 27 will be clarified below.

(1) Since the material sand 7 is pumped in a state where the fluidity is once increased, the material sand 7 preferably has the property of having both good water retention that does not block in the piping and good drainage that dehydrates during press-fitting. For this point, refer to FIG. 6 of JP-A-2015-183466 and the related description. In addition, the material sand 7 may include divalent or higher valent metal ions as cations that may inhibit the fluidizing agent, although it varies depending on the collection location. Examples of divalent or higher metal ions include calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ), iron ions (Fe ²⁺ , Fe ³⁺ ), and aluminum ions (Al ³⁺ ). Note that the material sand subject to the invention is an irregular sand that is not normal, that is, the sand contains a cation that hinders the fluidizing agent, and sand press-fit static compaction method or sand filling from texture tests etc. Sand that was judged to be difficult to apply to the construction method. Accordingly, it is needless to say that the ionic charge neutralizing additive of the present invention does not need to be mixed in other cases, that is, in the case of ordinary material sand.

(2) The ionic charge neutralizing additive is mixed with the material sand 7 described above, and as a clogging factor of the fluidizing agent, that is, as a cation contained in the material sand, the metal having a valence of 2 or more It is an inorganic charge neutralizing agent suitable for neutralizing ions in terms of ionic charge, or an organic charge neutralizing agent particularly suitable for neutralizing or sequestering trivalent or higher metal ions. Next, a specific example is given.

Examples of the inorganic charge neutralizing agent include sodium bicarbonate (NaHCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), sodium tripolyphosphate (Na ₅ P ₃ HCO ₁₀ ), and polyacrylic used in Examples 1 to 5 described later. Sodium nitrate (C ₃ H ₃ NaO ₂ ) _n , sodium hexametaphosphate (NaPO ₃ ) _{6 and the} like. It has been confirmed by the present inventors that potassium chloride (NaCl), sodium chloride (NaCl), potassium carbonate (K ₂ CO ₃ ) and the like are effective as other ionic charge neutralizing additives. In contrast, as the organic charge neutralizer, 3-hydroxybenzoic 2,2' iminodisuccinic acid tetrasodium used in Example _{8~10 (C 8 H 7 NO 9} · 4Na), ethylenediaminetetraacetic acid tetrasodium four it is a tetrahydrate _{(C 10 H 12 N 2 O} 8 Na 4 · 4H 2 O) and the like.

0
The additive for neutralizing ionic charge is, for example, inferred from what kind of aspect to neutralize divalent or higher-valent metal ions contained in the material sand in terms of ionic charge, but by the following reaction It is considered a thing. As an example, when the ionic charge neutralizing additive is sodium hydrogen carbonate (NaHCO ₃ ) as an inorganic charge neutralizing agent, for example, calcium ions (Ca ²⁺ ) and magnesium ions (Mg ²⁺ ) contained in the material sand ( 1) Ca ²⁺ + NaHCO ₃ = CaCO ₃ + (Na ⁺ + H ⁺ )
(2) Mg ²⁺ + NaHCO ₃ = MgCO ₃ + (Na ⁺ + H ⁺ )
The reaction formulas (1), (2), etc. are considered to neutralize Ca ²⁺ and Mg ²⁺ , which are divalent or higher metal ions, in an ionic charge to eliminate or suppress the inhibitory factor of the fluidizing agent. .

  The above ionic charge neutralizing additives cannot be expected to improve much when mixed with the raw material sand at the same time as the fluidizing agent. Absent. In other words, the material sand of the raw material is neutralized in an ionic charge manner with a cation charge neutralizing additive as a hindering factor of the fluidizing agent contained in the material sand. The fluidizing agent is mixed after eliminating or suppressing the inhibiting factor in advance. In addition, the mixing ratio of the additive to the material sand of the raw material is a fluid produced by mixing the additive with the target material sand as inferred from the examples described later, and then mixing the fluidizing agent and water for adjusting the water content ratio. For fluidized sand produced by mixing sand, or fluidizing agent, water content adjustment water, and slow-acting plasticizer, the properties of the fluidized sand are determined by a texture test, flow test, etc. Values that fall within the range will be confirmed and determined through testing.

(3) Water is used for adjusting the water content ratio, and avoids industrial water and seawater containing various components (cations such as the above-mentioned metal ions) that affect fluidizing agents. It is preferable to use it. The amount of water used is usually calculated so that the water content of the fluidized sand produced is 30% to 40%.

(4) The fluidizing agent is an additive that increases the viscosity of pore water between sand particles and suppresses separation of sand and water in a saturated state to improve pumpability. Preferably, it is an anionic polymer flocculant that increases the viscosity and suppresses the settling and separation of sand particles, and may also be a nonionic polymer flocculant or a cationic polymer flocculant. These are excellent in the performance of retaining moisture inside the polymer hydrophilic groups and the polymer network, and also have high quality long-term stability. As anionic polymer flocculants, homopolymers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, acrylamide 2-methylpropane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, and copolymers with acrylamide Is mentioned.

  The blending ratio of the fluidizing agent is 0.01 to 2.0% by weight, preferably 0.1 to 1.0% by weight, based on the material sand. If this blending ratio is too small, the material sand will not fluidize, it will be separated or clogged in the piping and cannot be pumped, and if it is too much, the fluidization effect will not change, and the cost will be increased. It will be.

(5) The amount of the slow-acting plasticizing agent used is a blending amount capable of plasticizing the fluidized sand, and is 0.001 to 2% by weight based on the material sand in the fluidized sand to be produced. %, Preferably 0.01 to 1.0% by weight. If the amount added is too small, the fluidized material will not be plasticized, and it will not be possible to produce an improved body as designed.If the amount added is too large, plasticization will occur quickly, hindering pumping and at the same time will be expensive. Become.

(Manufacturing method of fluidized sand) In manufacturing plant 2, when preparing fluidized sand for use in the sand press-fit static compaction method and sand filling method, it is judged that the material sand of the raw material is difficult to apply from the texture test etc. In this case, the desired fluidized sand is produced in the following manner. First, mix the required amount of ionic charge neutralizing additive uniformly with a predetermined amount of material sand 7 corresponding to one batch amount, or adjust the water content ratio together with the required amount of ionic charge neutralizing additive Mix water. Thereafter, a fluidizing sand is prepared by adding a fluidizing agent and a slow-acting plasticizing agent. For example, after preparing fluidized sand by mixing a fluidizing agent, or a fluidizing agent and water content adjustment water, or a fluidizing agent, water content ratio adjusting water and a slow-acting plasticizer with respect to the material sand. This is because mixing the ionic charge neutralizing additive does not improve the properties over time of the fluidized sand produced. That is, in the stage before mixing the fluidizing agent with the material sand of the raw material, the additive for neutralizing ionic charge is mixed to inhibit the fluidizing agent contained in the material sand (metal ion as cation, especially divalent or higher) It is essential to eliminate or suppress the metal ions.

(Sand press-fit type static compaction method) This method is as follows when the feature points are exemplified in the example using the construction machine 1 of FIG. First, the operation procedure is such that the hollow tube 3 is penetrated to the design depth in the ground via the lifting mechanism 4 and then pulled out by a predetermined pitch, and the density that can be formed below the hollow tube 3 in the pulling step. The improvement body 9 having a predetermined length is formed by repeatedly performing the supply process of press-fitting fluidized sand into the low area and the surrounding area. The construction management is carried out in the control section of the cab 11 with the maximum penetration depth of the hollow tube 3 (lower end depth), the drawing length L for one pitch, the total number of pitches ((lower end depth−upper end depth) / L), Values such as the set press-fit (discharge) pressure are input to the program. The produced fluidized sand is prepared in the agitator section 22.

  At the time of construction, after the construction machine 1 is moved and positioned at the construction site, the hollow tube 3 is inserted into the ground while being rotated through the lifting mechanism 4 and the rotating mechanism 5. This penetration is determined by a signal from a depth meter (not shown) whether or not the lower end of the hollow tube 3 has reached the design depth (lower end depth). The penetration is stopped.

  Next, the control unit controls to start drawing the hollow tube 3 by one pitch (for example, 20 cm) through the lifting mechanism 4, and at the same time, the pump P is operated and the fluidized sand is pumped. It controls so that it may press-fit in the area | region formed under the hollow tube 3, and its periphery with drawing | extracting. That is, the control unit determines whether or not the drawing has reached one pitch, and when it is determined that the drawing has reached one pitch, controls the lifting mechanism 4 to be stopped or in an idling state. Further, the control unit determines whether or not the press-fitting pressure of the fluidized sand discharged to the above-described region has reached a set value as the press-fitted state of the fluidized sand based on the detection signal sent from the pressure gauge 6. When it is determined that the press-fitting pressure has reached the set pressure, the pump P stops or switches an open / close valve (not shown) to a closed state.

  In the above control unit, it is determined whether or not the total number of pitches or all pitches have been drawn, and the drawing and press-fitting of fluidized sand are repeated until the total number of pitches is reached. Further, when the total number of pitches is reached, one improved body 9 is terminated. Then, after the ground improvement apparatus 1 is moved to the next construction location and positioned, the above operation is performed again.

(Example) Examples 1-5 shown in FIGS. 1 to 7 are used as raw material sand (this material sand can be applied to a sand press-fit static compaction method or a sand filling method from a texture test or the like). Among the ionic charge neutralizing additives, sodium hydrogen carbonate (NaHCO ₃ ) is used in Example 1 as an inorganic charge neutralizing agent, and sodium carbonate (Example 2 is used in Example 2). Na ₂ CO ₃ ), sodium tripolyphosphate (Na ₅ P ₃ HCO ₁₀ ) in Example 3, sodium hexametaphosphate (NaPO ₃ ) ₆ in Example 4, and sodium polyacrylate (C ₃ H ₃ NaO ₂ ) _n is mixed, and then each fluidized sand produced by mixing water content adjustment water, a fluidizing agent, and a slow-acting plasticizing agent in a determined ratio is shown in FIGS. Texture of FIG. -The test results when the test and the flow test of Fig. 3 were performed are summarized in a graph.

Further, Examples 6 and 7 shown in FIG. 8 to FIG. 10 show that raw material sand (this material sand is difficult to be applied to a sand press-fit static compaction method or a sand filling method from a texture test or the like). In Example 6 as an organic charge neutralizing agent among the ionic charge neutralizing additives, 4-hydroxy-2,2′-iminodisuccinic acid tetrasodium (C ₈ H ₇ NO _9). · 4Na) and, after mixing example 7 In tetrasodium ethylenediaminetetraacetate tetrahydrate _{(C 10 H 12 N 2 O} 8 Na 4 · 4H 2 O), water content adjusted water, flowing agents, slow-acting plastic FIG. 11 is a graph summarizing the test results when the texture test of FIG. 8 and FIG. 10 and the flow test of FIG. 9 are performed on each fluidized sand produced by mixing the agent in a determined ratio.

  In the texture test, fluidized sand (sample) is filled in a predetermined container and set as a commercially available texture test device on a tabletop physical property measuring instrument manufactured by Yamaden Co., Ltd. Perform 20 mm penetration and withdrawal. The penetration stress is a value obtained by converting the maximum load ha at the time of penetration into stress. Further, the flow (table flow) test was performed in accordance with a cement physical property test method (JIS R5201-1997).

Example 1: 2 and 3, for a given amount of material sand, 0 ppm of NaHCO ₃ as mixing ratio, was mixed 100 ppm, 500 ppm, and 1000 ppm, water content ratio adjusting water, flowing agents, slow-acting plasticized The results of examining a texture test (hardness) and a flow test (fluidity) are shown for four types of fluidized sand prepared by mixing agents at a predetermined ratio. In the figure, the composition of NaHCO ₃ , which is an additive for neutralizing ionic charge, is a sample in which black circles are 0 ppm, that is, not mixed, a sample in which squares are mixed in 100 ppm, a sample in which white circles are mixed in 500 ppm, and a sample in which triangles are mixed with 1000 ppm. From this test result, the penetration stress in FIG. 2 is significantly reduced even when 100 ppm is mixed as compared with the conventional sample in which sodium hydrocarbon is not mixed. When sodium hydrocarbon is added to 14,880 Pa (Pa), the change in properties is suppressed to 10,000 (Pa), and the standard value by mixing 1000 ppm of sodium hydrocarbon, that is, 3 hours of preparation It can be seen that even the intrusion stress of the later fluidized sand is improved to about 5,878 (Pa), that is, all are 6,000 (Pa) or less.

  Moreover, from the flow test result of FIG. 3, it can be understood that the fluctuation of the table flow value (mm) due to the presence or absence of mixing of hydrocarbon sodium is hardly recognized, and the influence of the fluidized sand on the table flow value can be ignored. In addition, the inorganic charge neutralizing agent which is an additive for ionic charge neutralization may be either a method of mixing with material sand in a powder state or a method of mixing with material sand in a state dissolved in water. In general, the latter method is preferable from the viewpoint of uniform mixing. In this case, the used water is treated as part of the water content adjustment water.

Example 2: FIG. 4 shows a mixture of 0 ppm, 100 ppm, 500 ppm, and 1000 ppm of Na ₂ CO ₃ as a mixing ratio with a predetermined amount of material sand, and then water for adjusting the water content, fluidizer, and slow-acting plasticizer. The result of having investigated the texture test (hardness) about four types of fluidized sand produced by mixing each in a determined ratio is shown. In the figure, the composition of NaCO ₃ which is an additive for neutralizing ionic charge is a sample in which black circles are 0 ppm, that is, not mixed, a sample in which squares are mixed in 100 ppm, a sample in which white circles are mixed in 500 ppm, and a sample in which triangles are mixed with 1000 ppm. From this test result, the penetration stress is significantly reduced even when 100 ppm is mixed as compared with the conventional sample in which sodium carbide is not mixed. In other words, for example, looking at the change over time after 3 hours of preparation, when no additive is added, the change in properties is suppressed to 10,970 (Pa) when the additive is added to 14,880 (Pa). The point is that, by mixing 500 ppm of sodium carbide, the reference value, that is, the penetration stress of fluidized sand after 3 hours of preparation, for example, is improved to 6,000 (Pa) or less. The penetration stress is 500 ppm of sodium carbide. It can be seen that there is little change between mixing and 1000 ppm. Although omitted for the flow test, as in Example 1, the change in the table flow value (mm) due to the presence or absence of mixing of sodium carbide is hardly recognized, and the influence of the fluidized sand on the table flow value can be ignored. .

Example 3 FIG. 5 shows a mixture of 0 ppm, 100 ppm, 500 ppm, and 1000 ppm of sodium tripolyphosphate (Na ₅ P ₃ HCO ₁₀ ) with a predetermined amount of material sand, water content adjustment water, and flow 4 shows the results of examining the texture test (hardness) of four types of fluidized sand prepared by mixing an agent and a slow-acting plasticizer at a predetermined ratio. In the same figure, the composition of Na ₅ P ₃ HCO ₁₀ which is an additive for ionic charge neutralization is a sample in which black circle is 0 ppm, that is, not mixed, sample in which square is mixed in 100 ppm, sample in which white circle is mixed in 500 ppm, triangle mixed in 1000 ppm It is a sample. From this test result, it is found that the intrusion stress is significantly reduced even when 100 ppm is mixed as compared with the conventional sample in which sodium tripolyphosphate is not mixed. When sodium tripolyphosphate is added to 880 (Pa), the change in properties is suppressed to 7,970 (Pa), and the flow after 3 hours of preparation by mixing 1000 ppm of sodium polyphosphate Even if it is the penetration stress of fossil sand, it is 3,807 (Pa), and it turns out that it is improved to 6,000 (Pa) or less which is a standard value. Although omitted for the flow test, as in Example 1, the fluctuation of the table flow value due to the presence or absence of mixing of sodium tripolyphosphate is hardly observed, and the influence of the fluidized sand on the table flow value can be ignored.

Example 4: FIG. 6 shows a mixture of 0 ppm, 100 ppm, 500 ppm and 1000 ppm of sodium polyacrylate (C ₃ H ₃ NaO ₂ ) _n with a predetermined amount of material sand, The result of having investigated the texture test (hardness) about four types of fluidized sand produced by mixing a fluidizing agent and a slow-acting plasticizing agent at a predetermined ratio is shown. In the figure, the composition of (C ₃ H ₃ NaO ₂ ) _n , which is an additive for ionic charge neutralization, is a sample in which the black circle is 0 ppm, that is, a sample that is not mixed, a sample in which a square is mixed in 100 ppm, a sample in which a white circle is mixed in 500 ppm, and a triangle A sample mixed with 1000 ppm. From this test result, it is found that the penetration stress is greatly reduced even when 100 ppm is mixed as compared with the conventional sample in which sodium polyacrylate is not mixed. When an additive is added to 880 (Pa), the change in properties is suppressed to 9,389 (Pa), and by mixing 1000 ppm of sodium polyacrylate, a reference value, that is, 3 hours after preparation It can be seen that even the penetration stress of fluidized sand is improved to 6,000 (Pa) or less. Although omitted for the flow test, as in Example 1, the change in table flow value due to the presence or absence of mixing of sodium polyacrylate is hardly observed, and the influence of the fluidized sand on the table flow value can be ignored.

Example 5: FIG. 7 shows a mixture of 0 ppm, 100 ppm, 500 ppm, and 1000 ppm of sodium hexametaphosphate (NaPO ₃ ) ₆ with a predetermined amount of material sand, water content adjustment water, fluidizing agent, The result of having investigated the texture test (hardness) about four types of fluidized sand produced by mixing slow-acting plasticizers at a predetermined ratio is shown. In the figure, the composition of (NaPO ₃ ) ₆ , which is an additive for neutralizing ionic charge, is a sample in which black circle is 0 ppm, that is, not mixed, sample in which square is mixed in 100 ppm, sample in which white circle is mixed in 500 ppm, sample in which triangle is mixed with 1000 ppm It is. From this test result, it is found that the penetration stress is significantly reduced by mixing 100 ppm as compared with the conventional sample in which sodium hexametaphosphate is not mixed. When an additive is added to 880 (Pa), the change in properties is suppressed to 7,257 (Pa), the fluctuation of penetration stress due to the mixing ratio of sodium hexametaphosphate, for example, 2 hours after preparation Comparing the penetration stress of the fluidized sand, the penetration stress is 6,000 (Pa), which is the smallest at 100 ppm, and the penetration stress is about 7,000 (Pa), 1000 ppm, which is greater than 500 ppm. Since it is 9,000 (Pa), which is larger, when selecting specific ionic charge neutralizing additives, the optimum blending ratio is verified and determined by preliminary tests. The point that must be seen. Although the flow test was omitted in Example 5 as well, as in Example 1, the change in the table flow value due to the presence or absence of mixing of sodium hexametaphosphate was hardly observed, and it affected the table flow value of the fluidized sand. The impact is negligible.

Example 8: FIG. 8 and FIG. 9 show that 0 ppm as a mixing ratio of 4-hydroxy-2,2′-iminodisuccinic acid tetrasodium (hereinafter referred to as HIDS) as an organic charge neutralizing agent with respect to a predetermined amount of material sand. After mixing 600 ppm, 1200 ppm, and 2400 ppm, four types of fluidized sand prepared by mixing water content adjustment water, fluidizing agent, and slow-acting plasticizing agent at a determined ratio, respectively, texture test (hardness) And the results of examining the flow test (fluidity). In the figure, the composition of HIDS, which is an organic charge neutralizing agent, is a sample in which black circles are 0 ppm, that is, not mixed, a sample in which squares are mixed in 600 ppm, a sample in which white circles are mixed in 1200 ppm, and a sample in which triangles are mixed with 2400 ppm. From this test result, the penetration stress of FIG. 8 is significantly reduced even by mixing 600 ppm as compared with the conventional sample not mixed with HIDS. When 600 ppm of HIDS is mixed with 380 (Pa), the change in properties is suppressed to 6,378 (Pa). By mixing 2400 ppm of HIDS, the standard value, that is, fluidized sand 1 hour after creation It can be seen that the penetration stress is improved to 5,948 (Pa), that is, about 6,000 (Pa) or less.

  Further, from the flow test result of FIG. 9, it is understood that the fluctuation of the table flow value (mm) due to the presence or absence of mixing of HIDS is hardly recognized, and the influence of the fluidized sand on the table flow value can be ignored. In the case of the organic charge neutralizing agent, either the method of mixing with the material sand in the form of a powder or the method of mixing with the material sand in the state of being dissolved in water may be used as in the case of the inorganic charge neutralizing agent. In general, the latter method is preferable from the viewpoint of uniform mixing. In this case, the used water is treated as part of the water content adjustment water.

  Example 2: FIG. 10 shows a mixture of 0 ppm, 600 ppm, 1200 ppm, and 2400 ppm of ethylenediaminetetraacetic acid tetrasodium tetrahydrate (hereinafter referred to as “Cylest OD”) as an organic charge neutralizing agent to a predetermined amount of material sand. After that, the results of examining the texture test (hardness) of four types of fluidized sand prepared by mixing water content adjustment water, fluidizing agent, and slow-acting plasticizer at a predetermined ratio are shown. Yes. In the figure, the blend of Cylest OD, which is an organic charge neutralizing agent, is a sample in which black circles are 0 ppm, that is, not mixed, a sample in which squares are mixed in 600 ppm, a sample in which white circles are mixed in 1200 ppm, and a sample in which triangles are mixed with 2400 ppm. From this test result, the penetration stress is greatly reduced even by mixing 600 ppm as compared to the conventional sample in which no quirest OD is mixed. In other words, for example, looking at the change over time after 1 hour of preparation, when no additive is added, the change in properties can be suppressed to 6,128 (Pa) when mixing 600 ppm of Kyrest OD with 16,380 (Pa). The point is that, by mixing 1200 ppm of Kirest OD, the standard value, that is, the penetration stress of fluidized sand, for example, 1 hour after creation is improved to 4,877 (Pa) or less, the penetration stress is mixed with 600 ppm of Kirest OD. It can be seen that there is not much change between the case of 2400 ppm and the case of mixing. Although omitted for the flow test, as in Example 1, the change in the table flow value (mm) due to the presence or absence of mixing of sodium carbide is hardly recognized, and the influence of the fluidized sand on the table flow value can be ignored. .

  In addition, the above form example and Example do not restrict | limit this invention at all. The present invention only needs to include technical elements specified in the claims, and the details can be variously changed as necessary. In addition, regarding “press-fit sand pile creation (same as sand press-fit static compaction method) and ground improvement such as sand filling”, the methods described in Patent Documents 1 and 2, Patent No. 5478386, and It includes construction methods that can be easily considered from the contents.

DESCRIPTION OF SYMBOLS 1 ... Construction machine 2 ... Fluidized sand manufacturing plant 3 ... Hollow pipe 4 ... Elevating mechanism 5 ... Rotating hand mechanism 6 ...・ Pressure gauge 7 ... Material sand 8 ... Injection pipe 9 ... Improved body 15 ... Swivel 16 ... Pipe line 24 ... Ion Charge neutralizing additive supply means 25... Fluidizing agent supply means 26... Adjustment water supply means 27.

Claims (6)

In fluidized sand for ground improvement that is treated so that it can be transferred through piping by a pressure pump by adding a fluidizing agent together with water for adjusting the water content ratio to the material sand,
After mixing the material sand with an additive for neutralizing an ionic charge capable of charge neutralizing cations such as metal ions contained in the material sand and inhibiting the fluidizing agent, the fluidizing agent is added. Fluidized sand characterized by contamination.   The fluidized sand according to claim 1, wherein the ionic charge neutralizing additive is an inorganic charge neutralizing agent such as sodium carbonate, sodium tripolyphosphate, or sodium hexametaphosphate.   The ionic charge neutralizing additive is an organic charge neutralizing agent such as 4-hydroxy-2,2'-iminodisuccinic acid tetrasodium, ethylenediaminetetraacetic acid tetrasodium tetrahydrate, and the like. Fluidized sand as described.   The fluidized sand according to any one of claims 1 to 3, wherein the fluidized sand has an intrusion stress of about 6,000 (Pa) or less after at least 1 hour of preparation from a texture test. In the manufacturing method of the fluidized sand in any one of Claim 1 to 4,
A method for producing fluidized sand, comprising mixing the ionic charge neutralizing additive with the material sand, and then mixing the fluidizing agent, water content adjusting water, and slow-acting plasticizer.   In ground improvement methods such as press-fitting sand pile creation and sand filling, the fluidized sand according to any one of claims 1 to 4 is pumped to a hollow pipe that is penetrated into or pulled out from the ground through a pipe by a pump. A ground improvement method characterized by press-fitting into the ground from the tip side of the hollow tube and plasticizing in the ground.

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