JP7121542B2 - Method for producing fluidized sand - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing fluidized sand in which a fluidizing agent is added to a sand material together with water for adjusting the water content, and the sand is transferred .

For example, when building structures are demolished or when revetments and river bridges are replaced, many existing piles are pulled out and removed. material). This filling operation presents a variety of problems such as draw-in settling, especially due to the incomplete filling leaving voids and weak spots later.

More specifically, conventional fillers generally include locally generated soil, fluidized soil, and cement slurry. Among these, cement slurry is often avoided because it causes alkali elution and underground obstruction. Filling methods include a structure in which the filling material is put in from the surface side after the piles are pulled out, and a structure in which the filling material is injected by free fall or pumping by inserting a pipe to the side when the piles are pulled out. separated. In the former case, the bottom of the hole is not filled and a cavity is formed, and the earth and sand dropped into the hole during extraction tends to remain as soft soil. In the latter, since the filling material is inserted in accordance with the pulling out of the pile or the like, it is easily filled from the bottom of the hole.

By the way, in order to reliably fill the holes formed by the drawing with sand at the same time when the sheet pile is pulled out, the applicants previously provided a sand injection cylinder in the longitudinal direction of the inner surface of the sheet pile as disclosed in Patent Document 1. We have developed a structure in which the sheet pile is pulled out from the ground and sand is injected into the extraction hole through a sand injection cylinder at the same time. However, in such a configuration, it is necessary to attach a sand injection cylinder or a sand injection pipe to the sheet pile or pile before driving, and it cannot be applied to the case of pulling out the existing pile or sheet pile.

In addition, as disclosed in Patent Document 2, the present applicants put the sand material for ground improvement into a fluidized state that can be pumped by a pump, and pumped it into holes formed in the ground to reduce costs and reduce environmental impact. A press-fitting sand pile construction method has been developed and has already been put into practical use. This construction method is also called the SAVE-SP method (registered trademark), in which fluidized sand containing a fluidizer and a slow-acting plasticizer is added to the ground while maintaining a fluidized state, along with water for adjusting the water content ratio. It is pressed in and plasticized in the ground. That is, after penetrating the hollow pipe 23 into the ground as shown in FIG. A step amount of fluidized sand is press-fitted, and this process is repeated to form an improved body 25 of a predetermined length. Reference numeral 10 is a fluidized sand manufacturing plant, 1 is a fluidized sand supply means, 2 is a sand material supply means, 3 is a fluidizing agent supply means, 4 is a pumping pump, and 5 is a slow acting plasticizer supply means. In manufacturing plant 10, fluidized sand is mixed with sand material in the order of water, fluidizer, and slow-acting plasticizer.

FIG. 5 is a schematic diagram showing changes in the state of fluidized sand. (a) shows fluidized sand before injection. Fluidized sand increases the viscosity of interstitial water between sand particles until it is pressed into the ground through a hollow tube, eliminating friction between particles and suppressing separation between sand and water. maintain liquidity. (b) shows fluidized sand during injection. During injection, the fluidized sand is dehydrated and compacted to a dense state. The superplasticizer remains reticulated. (c) shows the end state of plasticization. In this state, the slow-acting plasticizing agent electrically neutralizes the fluidizing agent, making it impossible to maintain the network structure of the fluidizing agent, thereby restoring the friction between the particles.

JP-A-61-254715 JP 2010-13885 A

Since the above-mentioned fluidized sand is excellent in handling and filling properties, it has been studied for application as a filling material for holes and cavities formed by pulling out existing piles and sheet piles in addition to soil improvement. Something like that is a problem. In other words, the physical properties of fluidized sand were adjusted and managed mainly by the table flow value, texture value, and bleeding value. For this point, please refer to Japanese Patent Application Laid-Open No. 2015-183466 (hereinafter referred to as Reference 1) and Japanese Patent Application No. 2017-152091 (hereinafter referred to as Reference 2). The reason for this is that air is mixed into the fluidized sand during mixing and stirring during the production of fluidized sand, and the amount of air mixed in varies widely, making it difficult to control and adjust the volume and density of the fluidized sand. rice field. In addition, in the above SAVE-SP method, the fluidized sand is injected into the ground at a set discharge pressure. No effect on body. However, when filling a hole or cavity formed by drawing with fluidized sand, the discharge pressure is set low in order to suppress the impact of the injection on the surrounding ground. remain. Against this background, the applicants have studied a method of managing fluidized sand by density as a physical property value.

An object of the present invention is to make it possible to adjust and manage the density of fluidized sand relatively easily. Another object of the present invention is to provide fluidized sand that can be evaluated more accurately. Other purposes will be made clear in the following description.

In order to achieve the above object, the invention of claim 1 provides a method for producing fluidized sand in which a fluidizing agent is added to and mixed with water for adjusting the water content ratio in a fluidized sand producing unit, wherein the fluidizing sand producing unit comprises: Air desorption means for receiving the mixed fluidized sand, volume measuring means and weight measuring means for the fluidized sand, and air amount increasing/decreasing means for adjusting the amount of air in the fluidized sand to reduce air in the fluidized sand. It has a density adjustment unit provided with an air mechanism and an air addition mechanism for increasing air in the fluidized sand, and the flow received from the fluidized sand production unit to the density adjustment unit by the volume measurement means and the weight measurement means The density of the composted sand and the amount of air mixed in are grasped, and if the density is lower than a predetermined value or range, the air is removed from the fluidized sand by the air deaeration mechanism to adjust the density so that the density reaches the predetermined value. If it is higher than the value or range of , the air addition mechanism mixes air into the fluidized sand to adjust it to be lower.

Here, in the present invention, the sand material is not limited to pure sand as long as it has been used in the conventional production of fluidized sand. used in a sense. In addition, the present applicants have proposed a structure containing a superabsorbent resin in Reference Document 1 and a nonionic fluidization retention agent in Reference Document 2 as a structure for expanding the application range of sand materials used for fluidized sand. We are developing a configuration that contains In order to expand the applicable range of the sand material, the present invention may be configured to contain such a superabsorbent resin or nonionic fluidization retention agent as necessary.

More preferably, the present invention described above is further embodied as follows. i.e.
First, the air degassing mechanism is a vibrating mechanism and/or a vacuum suction mechanism, and the air adding mechanism is a stirring mechanism and/or an air blowing mechanism (Claim 2).

These are specific examples of the air degassing mechanism and the air adding mechanism. is effective as an air degassing mechanism as in the second embodiment.

Secondly, a slow-acting plasticizer is added to the sand material together with the water for adjusting the water content ratio and the fluidizer (Claim 3).

According to the invention of claim 1, the density of the fluidized sand and the amount of air mixed therein are grasped by the volume measuring means and the weight measuring means, and when the density is out of a predetermined value or range, the air amount increasing/decreasing means Since the density is controlled by adjusting the amount of air contained in the fluidized sand, it can be provided as a fluidized sand for filling or ground improvement with a controlled density.

As a result, in the case of fluidized sand for filling, compared to fluidized sand for press-in sand pile construction, press-in compaction is not required. By properly adjusting the density, it is possible to obtain the highest quality and best evaluation as a filling material. In the case of press-in type sand pile construction fluidized sand, the density of the sand pile to be constructed can be easily estimated and evaluated from the density of the sand pile construction fluidization material used, and reliability can be improved.

In addition, the present invention specifies in detail that the air amount increasing/decreasing means has an air degassing mechanism and an air adding mechanism, and the control of the density is performed by the air degassing mechanism or the air adding mechanism. This can be done relatively easily by adjusting the amount of air contained in the produced fluidized sand.

The invention of claim 2 exemplifies a typical example of the air degassing mechanism or the air adding mechanism. However, the air degassing mechanism may be other than the vibrating mechanism and/or the vacuum suction mechanism, and the air adding mechanism may be other than the stirring mechanism and/or the air blowing mechanism.

According to the invention of claim 3, as an ideal composition of the fluidized sand, water for adjusting the water content ratio and a fluidizing agent are added to the sand material together with a slow-acting plasticizer.

The slow-acting plasticizer acts to electrically neutralize the fluidizing agent contained in the fluidized sand, and separates the water retained in the fluidized sand, thereby facilitating the return to the original sand state. .

1 is a schematic diagram showing an example of a fluidized sand manufacturing apparatus used in a fluidized sand manufacturing method according to the present invention; FIG. It is a flowchart which shows the manufacturing procedure example of the said fluidized sand. FIG. 2 is a schematic diagram showing an outline of a sand filling method using fluidized sand produced by the fluidized sand manufacturing apparatus of FIG. 1; It is a figure which shows the sand pile construction apparatus disclosed by patent document 2. FIG. (a) to (c) are schematic diagrams showing changes in the state of fluidized sand during construction.

Embodiments to which the present invention is applied will be described below with reference to the drawings. In this explanation, after clarifying the production method of the fluidized sand according to the present invention, Examples 1 and 2 when the density of the fluidized sand prepared in the same manner as before was adjusted, and the fluidized sand after density adjustment to mention the use case of .

(Manufacturing Method of Fluidized Sand) FIG. 1 shows an example of a fluidized sand manufacturing apparatus used in the manufacturing method of the present invention, and FIG. 2 shows an example of the fluidized sand manufacturing procedure. In FIG. 1, this fluidized sand manufacturing apparatus 1 includes a fluidized sand manufacturing section 2 provided in an upper frame 10A, a density adjusting section 3 provided in a middle frame 10B, and a lower frame 10C. A curing section (agitator section) 4 is provided, and fluidized sand whose density is controlled in the curing section 4 is transferred to a pipeline 6 by a pressure pump P. A reference numeral 5 is a pressure gauge for measuring the pressure of the fluidized sand transferred through the pipeline 6 . The fluidized sand manufacturing unit 2 and the curing unit 4 have almost the same configuration as the existing fluidized sand manufacturing apparatus.

That is, in the fluidized sand producing section 2, the mixing tank 20 is provided with a stirring mechanism 21 such as a paddle mixer and a weight measuring means 22 such as a load cell for measuring the weight of the sand material S to be fed. After a predetermined amount of sand material S corresponding to one batch amount is charged into the mixing tank 20 by a sand supply means 12 such as a backhoe, as shown in FIG. A predetermined amount of water for adjusting the water content ratio is supplied by the water supplying means 13, and a predetermined amount of the fluidizing and retaining agent is supplied by the fluidizing and retaining agent supplying means 16 as required. Further, the fluidizing agent is supplied by the fluidizing agent supplying means 14 and the slow-acting plasticizing agent is supplied by the plasticizing agent supplying means 15 in predetermined amounts. Preferably, based on the weight of the sand material in the mixing tank, the amounts of the water for adjusting the water content ratio, the fluidizing agent, and the slow-acting plasticizer are automatically calculated and supplied. In the mixing tank 20, they are mixed and stirred by the stirring mechanism 21 so that they become uniform.

Here, the sand material S supplied by the sand supply means 12, the water supplied by the water supply means 13, the fluidizing and retaining agent supplied by the fluidizing and retaining agent supplying means 16, and the fluidizing agent supplied by the fluidizing agent supplying means 14. Selection criteria for the fluidizing agent supplied by the plasticizing agent supplying means 15 and the plasticizing agent supplied by the plasticizing agent supply means 15 will be clarified below.

(1) Since the sand material is pumped once in a state of increased fluidity, it is preferable that the sand material has both good water retention properties so as not to clog the pipes and good drainage properties such as dehydration at the time of press-fitting. For this point, refer to FIG. 6 of Reference 1 and its related description.

(2) Water is used for adjusting the water content, and it is preferable to use neutral tap water, avoiding industrial water and seawater containing components that affect fluidizing agents, especially cations such as metal ions. The amount of water used is usually calculated so that the produced fluidized sand has a water content of 20 to 40%. If the water content ratio is high, the input capacity will also increase proportionally, making it easier to cause ground displacement.

(3) The fluidization retention agent improves the properties of the fluidized sand over time to enable normal press-in construction. Specifically, it is a nonionic surfactant or similar agent. be. Nonionic surfactants have been found to be considerably better than anionic and cationic surfactants in improving the behavior of fluidized sand over time (see reference 2). The fluidity retention agent described above cannot be expected to have a significant improvement effect even if it is mixed with the raw material sand material at the same time as the fluidizing agent, and furthermore, if it is mixed after the fluidizing agent is mixed with the sand material, no improvement effect can be obtained. In other words, the fluidizing agent is mixed into the raw material sand material after eliminating or suppressing the above-described inhibitory factors of the fluidizing agent contained in the sand material or water with the fluidizing retention agent. In addition, although the mixing ratio to the sand material varies depending on the sand material and water content, generally the lower limit of the amount to be added is 0.05% or more, and the higher the upper limit of the amount to be added, the higher the cost proportionally. Therefore, it is preferable to set the content to about 0.10%. However, the fluidity retention agent may be omitted.

(4) The fluidizing agent is an additive that increases the viscosity of interstitial water between sand particles, suppresses separation of sand and water in a saturated state, and improves pumpability. An anionic polymer flocculant that increases viscosity and suppresses sedimentation and separation of sand particles is preferred, and a nonionic polymer flocculant, a cationic polymer flocculant, and the like may also be used. These are excellent in the ability to retain moisture inside the hydrophilic group of the polymer and in the polymer network, and have high long-term quality stability. The mixing ratio of the fluidizing agent is 0.01 to 2.0% by weight, preferably 0.1 to 1.0% by weight, based on the sand material. If the mixing ratio is too low, the sand material will not be fluidized and will separate or clog in the pipe, making it impossible to pump. .

(5) The slow-acting plasticizer is used to ensure fluidity during pumping and press-fitting, and to control the time until plasticization. Cationic synthetic polymer agents having a molecular weight of 104 to 107 can be used as slow-acting plasticizers. Examples of cationic synthetic polymer agents include polycondensates of ammonia, aliphatic alkyl mono- or diamines, or polyamines and epihalohydrin. The amount of the plasticizer used is 0.001 to 2% by weight, preferably 0.01 to 1.0% by weight, based on the sand material in the produced fluidized sand. If the amount added is too small, the fluidized product will not be plasticized, making it impossible to form a packed body or improved body as designed.

In the density adjusting section 3, the density adjusting tank 30 includes a stirring mechanism 31 such as a paddle mixer, a weight measuring means 32 such as a load cell for measuring the weight of the fluidized sand received from the fluidized sand producing section 2, and a volume measuring means. and an air amount adjusting means 17 for adjusting the amount of air contained in the fluidized sand. Although not shown, the air amount increasing/decreasing means 17 releases the air in the fluidized sand transferred into the density adjusting tank 30 to the upper part of the density adjusting tank 30 or to the outside through the intake/exhaust pipe 18 to reduce the amount of air. It has an air degassing mechanism and an air adding mechanism for mixing or introducing air into the fluidized sand from the outside via the upper space of the tank or the intake and exhaust pipe 18 to increase the amount of air. A filter is attached to the tip of the intake/exhaust pipe 18 to allow only air to enter and exit without allowing water or sand to pass through.

Here, as the air deaeration mechanism, a vibrating mechanism for vibrating the density adjusting tank 30 to release the air contained in the fluidized sand from the upper surface side opening of the density adjusting tank 30 and further from the intake and exhaust pipe 18, and/or , a vacuum suction mechanism using a vacuum pump for vacuuming air contained in the fluidized sand through an intake/exhaust pipe 18 and a switching valve (not shown). On the other hand, as an air addition mechanism, a stirring mechanism 31 that mixes air into the fluidized sand in the density adjustment tank 30 by devising a stirring speed or the like, and/or an intake/exhaust pipe to the fluidized sand in the density adjustment tank 30 18 and an air blowing mechanism using an air pump that blows air through a switching valve (not shown) or the like. However, the air degassing mechanism and the air adding mechanism may be mechanisms other than those listed here.

The density adjustment unit 3 sets the density of the fluidized sand to a predetermined value or range (for example, 1.50 to 1.70 g/cm ³ ) for density control, and the minimum value (for example, 1.50 g/cm 3 ). cm ³ ), the air is removed from the fluidized sand in the density adjusting tank ³⁰ by the air deaeration mechanism to adjust the density to be higher. The air addition mechanism blows air into the fluidized sand transferred to the density adjustment tank 30 to mix and adjust the density. These adjustment operations are repeated to increase or decrease the amount of air in the fluidized sand, as shown in FIG. 2, until the desired density value or range is achieved.

In the curing section 4, the agitator tank 40 is provided with an agitating mechanism 41 such as a paddle mixer, and the fluidized sand in the agitator tank 40 received from the density adjusting tank 30 is agitated and cured in order to maintain quality such as density. . Compared to the stirring mechanism 21 of the fluidized sand manufacturing section and the stirring mechanism 31 of the density adjusting section, this stirring mechanism 41 is designed to prevent air from entering the fluidized sand during stirring, such as the shape of the stirring blades and rotation speed.

The fluidized sand in the agitator tank 40 is pumped through the pressure pump P and line 6 to the site of use for filling or for forming press-fit sand piles. For this pumping pump P, a type using a hydraulic piston is selected for the pumping structure because it has a particularly high suction force, is highly airtight, does not cause air intake, and can suppress changes in the properties of the fluidized sand. The pump drive can be automatically controlled via the controller or controlled by the operator.

(Example 1) In this Example 1, Komono sand (produced in Komono Town, Mie Prefecture) was used as the raw sand material, and a mixing tank similar to the mixing tank 20 of the fluidized sand production section in Fig. 1 was used to adjust the water content. 25%, fluidizing agent L1=0.64%, fluidizing retention agent S1=0.1%, and slow-acting plasticizer P1=0.05%. The fluidized sand was transferred from the mixing tank to a density adjustment tank similar to density adjustment tank 30 in the density adjustment section. The fluidized sand in the initial state had a density γ of 1.115 g/cm ³ based on the weight of the fluidized sand obtained from the weight measuring means 32 and the volume of the fluidized sand obtained from the volume measuring means 33. . Also, the relative density Dr was -256.6%, and the amount of air contained was 43.7%.

(1) The formula for calculating the relative density Dr is as follows.
Dr = ( _{emax-e)/(emax-emin ) x} 100 (%)
Here, e _max : Maximum void ratio of sand (calculated from minimum density/maximum density test of sand)
e _min : Sand minimum void ratio (calculated from sand minimum density/maximum density test)
e: Void ratio of fluidized sand

The formula for calculating the void ratio e of the fluidized sand is as follows.
e = (V - V _s ) / V _s = (volume of fluidized sand - volume of sand particles) / volume of sand particles It is possible to calculate the weight of sand when the volume is 1 cm ³ .

Next, for the fluidized sand, the water content ratio, the blending amount of the fluidizing agent (L1), the blending amount of the fluidization retention agent (S1), and the blending amount of the slow-acting plasticizer (P1) are determined based on the ratio to the weight of the sand. Therefore, when the volume of sand particles is 1 cm ³ , the weight of fluidized sand can be obtained by calculation. Also, since the density of the fluidized sand can be obtained from the density measurement described above, the volume of the fluidized sand when the volume of sand particles is 1 cm ³ can also be obtained. From the above, the void ratio of the fluidized sand can be calculated using the above equation.

Based on the above, in Example 1, sand particles having a specific gravity of 2.651, e _max of 0.913, and e _min of 0.493 were used. Suppose that the measured density of the fluidized sand prepared with a ratio of 0.05% and S1 of 0.1% is 1.115g/ ^cm3 . in this case,
・Sand particle weight of 1 cm ³ sand particle volume is 2.651×1=2.651g
・The weight of fluidized sand is 2.651 x (1 + 0.25 + 0.0064 + 0.0005 + 0.001) = 3.335g
・The fluidization volume of ^1cm3 of sand particles is 3.335/1.115 = 2.991
・Therefore, the void ratio of the fluidized sand is (2.991－1)/1=1.991
・The relative density of fluidized sand is {(0.913-1.991)/(0.913-0.493)}×100=-256%.

(2) The ratio of the amount of air mixed in the fluidized sand is calculated by the following formula.
Ratio of amount of air=Volume of air/Volume of fluidized sand Here, the weight of the fluidized sand is obtained from the weight of the sand and the mixing ratio.
・In addition, since the density of the fluidized sand is measured, the volume of the fluidized sand can also be calculated.
・Furthermore, since the weight of sand and the specific gravity of sand particles are known, the volume of sand particles in the fluidized sand can be calculated.
・Therefore, the volume of the gap (water + air) can be obtained from (fluidized sand volume - sand particle volume).

Next, the ratio of water and air in the gap is determined.
Since the void ratio of the fluidized sand is known, if the void ratio of only the liquid can be obtained, the ratio of water and air can be obtained, and the volume of the amount of air can be obtained. In this case, the void ratio of the liquid in the fluidized sand can be obtained by obtaining the void ratio at the theoretical saturation density when the fluidized sand is assumed to consist only of sand and water. Theoretical saturation density can be obtained because the mixing ratio of the fluidized sand and the specific gravities of the sand particles and the chemicals (L1, P1, S1 above) are known.

Based on the above, in Example 1, sand particles having a specific gravity of 2.651, e _max of 0.913, and e _min of 0.493 were used, and the water content ratio was 25% and L1 was 0.64% (specific gravity 1.05), P1 is 0.05% (specific gravity 1.15) ^, and S1 is 0.1% (specific gravity 1.0). Here, assuming that the sand is 1000 g, the composition of the fluidizing sand is 250 g of water content, 6.4 g of L1, 0.5 g of P1, and 1.0 g of S1.
・The fluidized sand volume at the above blending is (1000 + 250 + 6.4 + 0.5 + 1.0) / 1.115 = 1128.161 cm ³
・The volume of sand particles is 1000/2.651 = 377.216 cm ³
・Gap volume is 1128.161－377.216＝750.945cm ³

Then, the theoretical saturation density of fluidized sand is
(1000 + 250 + 6.4 + 0.5 + 1.0) / (1000 / 2.651 + 250 / 1 + 6.4 / 1.05 + 0.5 / 1.15 + 1.0 / 1.0) = 1.983g/ ^cm3
The theoretical saturation void ratio (water only void ratio) is
(2.651 x (1 + 0.25 + 0.0064 + 0.0005 + 0.001)) / 1.983 = 0.681
Of the fluidized sand void ratio of 1.991, the water void ratio of 0.681 and the air void ratio of 1.309 can be obtained. From the gap volume of 750.945 ^cm3 ,
The volume of air is 750.945 x (1.309/1.991) = 493.715 cm ³
Therefore, the ratio of air in the fluidized sand is (493.715/1128.161) x 100 = 43.7%.

The above-mentioned fluidized sand at the initial stage of production contains a considerably high amount of air, and it is preferable to reduce the amount of air contained as a filler for holes and cavities, or for construction of press-in sand piles. Therefore, as the air degassing mechanism, the upper surface of a density adjustment tank similar to the density adjustment tank 30 is opened or half-opened, and vibration is applied by a vibrator, that is, a vibration mechanism attached to the density adjustment tank. The air contained in the fluidized sand was degassed or vented. That is, the method of venting is to apply vibration. At that time, the contained air was made to escape from above the fluidized sand and from the intake/exhaust pipe 18 as well. Further, the density of the fluidized sand was measured after 10 minutes, 15 minutes, and 20 minutes of the degassing time. Table 1 lists the relative density and air content along with the results.

(Table 1)

(Embodiment 2) In this embodiment 2, kira sand (produced in Kira Town, Aichi Prefecture) was used as the raw material sand material, and a mixing tank similar to the mixing tank 20 in FIG. A fluidized sand was prepared with a composition of L1=0.64% and P1=0.05% of the slow-acting plasticizer. The fluidized sand was transferred from the mixing tank to a density adjustment tank similar to density adjustment tank 30 in the density adjustment section. The fluidized sand in the initial state had a density γ of 1.861 g/cm ³ based on the weight of the fluidized sand obtained from the weight measuring means 32 and the volume of the fluidized sand obtained from the volume measuring means 33 . Also, the relative density Dr was -25.8% and the amount of air contained was 7.2%. The method of calculating the relative density and the amount of air contained is the same as in Example 1, so the explanation is omitted.

In Example 2, the air degassing mechanism is configured such that the agitation mechanism attached to the density adjustment tank is driven while the upper surface of the density adjustment tank is half-opened, that is, the air removal method is agitation. At that time, the contained air was made to escape from above the fluidized sand and from the intake/exhaust pipe 18 as well. Further, the density of the fluidized sand was measured after 10 minutes and 60 minutes of the degassing time. Table 2 lists the relative density and air content along with the results.

(Table 2)

As is clear from each of the above examples, the fluidized sand can be managed and controlled in terms of density by adjusting the amount of air contained. As an advantage of this, in the case of fluidized sand for filling, in order to suppress the impact on the surrounding ground due to compaction, compared to the fluidized sand for press-in sand pile construction, the amount of air contained is set to be smaller and the density is adjusted higher. By doing so, it can be used as a filler whose density is controlled, and the best quality and evaluation can be obtained. In the case of fluidized sand for press-fitting sand pile construction, the density of the sand pile to be constructed can be easily estimated and evaluated from the density of the fluidized sand used, and reliability can be improved. Of course, with regard to the suitable density of the fluidized sand, even for filling or press-fitting sand pile construction, the optimum value or range is designed depending on the target ground properties and target values. The present invention is significant in enabling such a design.

(Usage Example of Fluidized Sand) FIG. 3 shows an example of refilling the hole formed by pulling out the existing pile with the fluidized sand having the density adjusted in the agitator tank 40 . In this use area, a large number of piles 9 used for ground improvement or foundation structures are driven, and a sand filling device 7 is arranged together with a pile extraction device (not shown). This sand filling device 7 is a substitute for the sand pile forming device (press-in type sand pile forming device) shown in FIG. A lifting mechanism 26 that moves up and down along one side via a rack and pinion mechanism or the like; It has a guide member 29 or the like that is bent and supports the upper side of the pipe line 6 . The upper end of the conduit 6 is connected to the upper end of the tremie tube 8 via a joint 27 .

In this example, when the pile 9 is pulled out, the tremie pipe 8 is penetrated by the elevating mechanism 26 along the pile 9, and the fluidized sand S1 whose density is adjusted in the agitator tank 40 is adjusted according to the pulling out of the pile 9. is sent via a pressure pump P and a line 6 and a tremie tube 8 to the hole formed by pulling out the pile 9 . For this reason, in this sand filling method, the pull-out hole can be filled and backfilled almost at the same time as the pile 9 is pulled out. The bottom of the hole can be refilled with plasticized sand S accurately without compaction. As a result, as a sand filling method, the density, filling amount, etc. of the fluidized sand S1 can be easily centrally managed and can be evaluated more accurately. In addition, the fluidized sand whose density is adjusted and managed in this way is suitable for the press-in sand pile construction method among the ground improvement methods shown in Fig. 4, in addition to the sand filling method illustrated in Fig. 3. .

It should be noted that the above embodiments and examples do not limit the present invention in any way. The present invention only needs to have the technical elements specified in the claims, and the details can be changed in various ways as necessary. The fluidized sand apparatus 1 shown in FIG. 1 is modified according to the production scale and cost of the fluidized sand. For example, in this embodiment, the fluidized sand producing section 2 in the upper stage, the density adjusting section 3 in the middle stage, and the curing section 4 in the lower stage, that is, a vertical three-stage system is used. A two-stage system consisting of the production section 2 and the density adjustment section 3, or a two-stage arrangement consisting of the density adjustment section 3 and the curing section 4 by separating the fluidized sand production section 2 is also conceivable.

REFERENCE SIGNS LIST 1: Fluidized sand manufacturing device 2: Fluidized sand manufacturing unit 3: Density adjusting unit 4: Curing unit (agitator unit)
5: pressure gauge 6: pipeline 7: fluidized sand filling device 8: tremie pipe 9: pile 12: sand supply Means 13...Adjustment water supply means 14...plasticizer supply means 15...plasticizer supply means 16...fluidization and retention agent supply means 17...・Air amount increasing/decreasing means (18 is an intake/exhaust pipe)
20: Mixing tank (21 is a stirring mechanism, 22 is weight measuring means)
30 Density adjustment tank (31 is a stirring mechanism, 32 is a weight measuring means)
33: Volume measuring means 40: Agitator tank (41 is a stirring mechanism)

Claims (3)

In a fluidized sand manufacturing method in which a fluidizing agent is added to and mixed with water for adjusting the water content ratio in a fluidized sand manufacturing section ,
Fluidized sand as volume measuring means and weight measuring means for fluidized sand and air amount increasing/decreasing means for adjusting the amount of air in the fluidized sand while receiving the fluidized sand mixed in the fluidized sand manufacturing section It has a density adjustment unit with an air deaeration mechanism to reduce the air inside and an air addition mechanism to increase the air in the fluidized sand ,
When the density of the fluidized sand received from the fluidized sand manufacturing unit and the amount of air mixed therein are grasped by the volume measuring means and the weight measuring means, and the density is lower than a predetermined value or range. is adjusted to be high by extracting air from the fluidized sand by the air deaeration mechanism, and when the density is higher than a predetermined value or range, the air addition mechanism mixes air into the fluidized sand to lower it. A method for producing fluidized sand, characterized by adjusting. 2. The method for producing fluidized sand according to claim 1, wherein the air degassing mechanism is a vibrating mechanism and/or a vacuum suction mechanism, and the air adding mechanism is a stirring mechanism and/or an air blowing mechanism. . 3. The method for producing fluidized sand according to claim 1, wherein a slow-acting plasticizer is added to the sand material together with the water for adjusting the water content and the fluidizer.

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