JP3896544B2 - Solidification slurry manufacturing method and ground improvement body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground improvement body obtained by the same method as the method for producing a solidifying material slurry, and in particular, at a site where an in-situ solidification method is performed, a solidified material slurry obtained by mixing regenerated fine powder obtained from concrete waste is simplified. Furthermore, the present invention relates to a method for producing a solidified material slurry which is produced while ensuring a certain quality, and a ground improvement body obtained by solidifying the solidified material slurry at the production site.
[0002]
[Prior art]
Conventionally, a shallow ground improvement method is known as an example of an in-situ solidification method for soft ground. In this shallow ground improvement method, in the surface layer of the target soft ground, the powdered cement-based solidified material and the in-situ soil in the improvement target range are mixed with a backhoe equipped with a stirring attachment or a mixing machine such as a stabilizer. In many cases, it is constructed by the “in-situ mixing method” where direct mixing is performed. However, in this construction method, there is a problem that dust due to powdered solidification material is generated and the surrounding environment is deteriorated. Therefore, construction is performed using a solidification material slurry that is slurried by adding water to the solidification material. Often done.
[0003]
On the other hand, for the shallow ground improvement, a mechanical stirring method and a high-pressure jet stirring method are known as a deep mixing method using a solidified slurry. In the mechanical agitation method, agitation mixing with the original position is performed by a mixing processor having an agitating blade while supplying the solidified material slurry to the ground. In the high-pressure jet agitation method, the solidified material slurry produced in the solidified material production plant installed on the ground is high-pressure injected into the ground using a high-pressure spray nozzle to simultaneously cut the ground in a predetermined range. The ground is forcibly agitated by the mixing action by the jet to improve the ground to a predetermined depth (see, for example, Patent Document 1 and Non-Patent Document 1).
[0004]
By the way, the applicant recycles 100% of the concrete waste material in order to re-apply the concrete waste generated at the time of dismantling of the reinforced concrete structure to the concrete structure again from the viewpoint of resource recycling type concrete recycling. We are researching and developing a concrete resource circulation system that can be separated into recycled aggregate and fine powder with the same quality as aggregate. In the recycled aggregate production plant in this concrete resource circulation system, the crushed demolished concrete is heated to about 300 ° C. in a heating tower, the residual moisture inside is removed and dehydrated, and the internal bonded state is made weak. By grinding (the process of these steps is hereinafter referred to as the “heated surimi method”), coarse aggregates and fine aggregates can be classified according to particle size, and concrete dust is collected by collecting fine powder. All materials recovered from can be recycled. Among them, the regenerated fine powder has stable quality with a specific surface area of 4,000 cm ² / g or more, and it is confirmed to have self-hardening (hydration-hardening) since it is mainly composed of cement hydrate. Yes. Utilizing the characteristics, an application as a material to be used for a solidified material in a deep mixing treatment method for sandy ground has already been proposed (see Patent Document 2). The solidified material slurry to which the regenerated fine powder is added has sufficient material separation resistance during construction, and can exhibit practical strength as a ground improvement material even during curing.
[0005]
[Patent Document 1]
JP 2000-54368 A.
[Patent Document 2]
JP 2002-70000 A.
[Non-Patent Document 1]
Edited by the Japan Cement Association, “Ground improvement manual using cement-based solidification material [2nd edition]”, Gihodo Publishing Co., Ltd., August 1994, p. 115-125.
[0006]
[Problems to be solved by the invention]
Each of the above-mentioned solidifying material slurries is manufactured through adjustment of mixed water and mixing and stirring of materials in a dedicated solidifying material manufacturing plant installed at the site, and is supplied to the improved position. For this reason, the manufacturing plant requires mechanical organization such as a stirring tank, a measuring device, a storage silo for solidifying material and bentonite, and a pressure pump, and depending on the construction scale, it is difficult to install and operate an appropriate manufacturing plant. There is.
[0007]
Moreover, since the wet density of the solidified material slurry produced by the facilities of these solidified material production plants is about 1.2 t / m ³ or less, it is 1.2 to 1.6 t / used in the shallow ground improvement method. production of solidifying material slurry m ³ approximately and becomes formulation difficult. Fixed mortar mixers and agitator vehicles are functionally suitable for mixing this type of solidified material slurry, but have a problem in terms of stably supplying the material used for the solidified material, and are used in actual sites. It is hard to be done.
[0008]
Therefore, when providing the solidified material slurry as the ground improvement material, the applicant, from the viewpoint of promoting the recycling of construction materials and the appropriate amount of materials used, solidifies by simple means on site, assuming the use of recycled concrete powder. The method which can manufacture a material slurry was examined, and the effective manufacturing method of the solidification material slurry by the following method was implement | achieved. Moreover, the solidified material slurry was produced at the original position where the ground improvement is scheduled, and solidified at the same position, so that the ground improved body could be directly created within the planned improvement area.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention excavates a slurry pit in the planned improvement area of the soft ground surface layer, pipes a supply pipe for injecting fine air into the slurry pit, and stores water (W ) Recycled fine powder (P) obtained by heating and grinding concrete waste material in the range of 60% = <W / P <= 150% and generated from the supply pipe It is characterized in that a slurry-like solidified material slurry is produced by stirring and mixing air blow by an upward flow of fine air for 30 minutes or more .
[0011]
The solidified material slurry filled in the slurry pits is solidified and formed in the planned improvement area of the soft ground surface layer .
[0012]
As another invention, a recycle fine powder (P) obtained by piping a supply pipe for injecting fine air into the water tank, heating the concrete waste material to the water (W) stored in the water tank, and grinding it, Is 60% = <W / P <= 150%, and air blow by upward flow of fine air generated from the supply pipe is performed for 30 minutes or more and stirred to mix the slurry solidified material slurry. It is characterized by manufacturing.
[0014]
[Production of recycled aggregate and recycled fine powder]
In the present invention, a process for producing a regenerated fine powder used as a compounding material for a solidifying material slurry as a ground improvement material will be described. In the present invention, in order to obtain a desired recycled fine powder from the concrete waste material, the “heated and ground rice cracking method” is adopted in the recycled aggregate production plant. In this heated grinding method, first, crushed concrete waste (so-called concrete waste) is put into a furnace of a heating tower and heated to about 300 ° C. Then, it grind | pulverizes by grinding (scrubbing) mechanically with a special grinding equipment, Furthermore, it classifies through a well-known classifier, The reproduction | regeneration aggregate of a desired particle size can be obtained. At this time, the recycled fine aggregate and the recycled coarse aggregate have the same quality as the conventional aggregate, and therefore can be used as an aggregate of general structural concrete. The regenerated fine aggregate and the regenerated coarse aggregate produced by this heated grinding method are in an absolutely dry state. In addition, regenerated fine powder is obtained at the same time as these reclaimed aggregates, and has a specific surface area of about 4,000 to 10,000 cm ² / g and is much finer than ordinary cement. A solidified material slurry having material separation resistance can be manufactured by mixing with water as a binder of the solidified material slurry as a material at a predetermined mixing ratio.
[0015]
[Production of solidified slurry]
In this embodiment, as will be described later, recycled fine powder as a solidified material or a mixture of cement-based solidified material and recycled fine powder is put into a slurry pit excavated and stored in the ground, Solid-liquid mixing is performed by an upward flow generated by the rising fine air, and a solidified material slurry having a predetermined quality can be obtained.
[0016]
FIG. 1 is a schematic view showing the configuration of an apparatus used in the method for producing a solidifying material slurry of the present invention and the operating state of the apparatus. FIG. 1 shows an upward flow 3 of fine air generated in the water of the slurry pit (hereinafter referred to as air blow) and a stage before the powdered solidified material is introduced into the water 2. This slurry pit 1 corresponds to, for example, a surface layer of a predetermined range of soft ground to be improved in the shallow layer, and in this embodiment, the planar range of the original ground planned for ground improvement is excavated into a pool of a certain depth. Has been. The solidified material slurry 5 is manufactured by mixing the water 2 stored in the slurry pit 1 and the charged solidified material 4 (FIG. 3). Then, it is planned to create a ground improvement body 6 as an improved ground or an artificial ground directly in the pit 1 by solidifying the solidified material slurry itself in the pit. At this time, the scale of the slurry pit 1 is preferably set to a depth of at least 1.0 m in order to ensure the quality of the solidified slurry produced by mixing in the pit with respect to the planned improvement plane range. . Thereby, the effect of the shallow layer improvement by solidification of the solidified material slurry produced by mixing in the slurry pit 1 at the original position can be surely obtained. Similarly, in the production of the solidified material slurry in the water tank, which will be described later, the depth at which sufficient stirring and mixing of water and the regenerated fine powder 4 as the powder solidified material is realized, for example, a water depth of 1.0 m. It is preferable that the water tank has a degree.
[0017]
In this slurry pit 1, regenerated fine powder 4 as a solidifying material is directly charged and mixed with water 2 stored in advance. At this time, as shown in FIG. The flexible container bag 7 made of cloth is packed, and the flexible container bag 7 is suspended above a predetermined position of the slurry pit 1 and dropped into the pit 1 from the discharge port 7a at the bottom. In addition, regenerated fine powder is carried in a powder transport vehicle (not shown) equipped with a powder tank, a powder supply hose is extended from the powder tank to the slurry pit 1, and a powder pressure pump installed in the vehicle. It is also possible to discharge directly into the slurry pit 1.
[0018]
As shown in FIG. 1 and FIG. 2 in advance, a plurality of nozzle tubes are erected in the slurry pit 1 at predetermined intervals in the vertical and horizontal directions. These nozzle tubes 10 are particularly formed of bottomed pipes as shown in an enlarged view in FIG. 2. In this embodiment, the total length is slightly longer than the depth of the slurry pit 1, and the diameter is about 25 mm (for example, 1 inch tube). The pipe made of vinyl chloride resin is used. Each nozzle tube 10 is installed over the entire plane of the slurry pit 1 with an installation interval of 0.5 m vertically and horizontally. Each nozzle tube 10 is fixed while maintaining a substantially vertical posture at the intersection of the spacer frames 11 (shown in broken lines) so that the arrangement position and posture of the nozzle tube 10 are maintained when the solidifying material is introduced. Yes. In this embodiment, as shown in FIG. 2, the spacer frame 11 is composed of a pipe frame assembled in a lattice shape with a 0.5 m interval, and its end is supported by the peripheral edge of the slurry pit 1. It has become so. Further, as shown in the figure, four air ejection holes are formed on the side surface near the bottom of each nozzle tube 10 at intervals of 90 ° in the circumferential direction. The diameter of the air ejection hole 12 is set to φ2 to 3 mm in the present embodiment. Each nozzle tube 10 is supplied with high-pressure air from an air supply tube connected to the top. In this embodiment, a flexible urethane tube is used as the air supply tube 13, and each air supply tube 13 is connected to each of the air branch portions 14 connected to the air compressor 15 installed on the ground in FIG. 1. The nozzle pipe 10 is connected in parallel. Thereby, the air pressure supplied to each nozzle tube 10 can be kept equal. At this time, the air pressure of the fine air continuously ejected from the nozzle tube 10 is strong in the relatively high viscosity slurry 5 in a state where the water 2 and the regenerated fine powder 4 as the solidifying material are mixed. A sufficiently high pressure is set so that the upward flow 3 is generated. The air pressure varies depending on the design flow value of the solidifying material slurry, but is preferably set to about 200 to 400 kN / m ² . In addition, it is preferable to set suitably the capability of the air compressor 15 provided, etc. according to the number of the nozzle pipes 10 to be connected and the set air pressure. In the present embodiment, the air ejection holes 12 of the nozzle tube 10 are provided only at the lower end. However, the nozzle tube 10 has a multi-tube structure, and a plurality of air ejection holes are provided at predetermined intervals in the longitudinal direction of the tube. It is also preferable.
[0019]
Next, an embodiment in which the method for producing a solidified slurry of the present invention is directly applied to an in-situ solidification method (shallow ground improvement) will be described with reference to FIG.
As shown by the broken line in FIG. 3A, the surface layer range where ground improvement is planned by the in-situ solidification method (in this embodiment, width 5.0 m × depth 5.0 m × depth 1.5 m) Is excavated by a heavy excavator such as a power shovel (not shown), and this excavation space is used as the slurry pit 1 of the present invention (FIG. 3B). Next, water 2 necessary for producing the solidified slurry is stored in the excavation space (FIG. 3C). At this time, when the target ground is sandy soil, it is preferable to form a thin temporary water shielding film (not shown) using a viscous material on the excavation wall surface and bottom surface. Furthermore, a necessary number of nozzle tubes 10 corresponding to the flat area of the improved range are arranged in the pit 1, an air supply tube 13 is connected to each nozzle tube 10, and an air branching portion 14 and an air compressor 15 are provided (see FIG. 1). Fine air is ejected from each nozzle tube 10 by the high-pressure air supplied from the air compressor 15, and a strong ascending water flow is formed in the water in the slurry pit 1 along with the ascending flow 3 (air blow) of the fine air. Can do. While continuing this air blow, as shown in FIG. 3D, the regenerated fine powder 4 as the solidifying material is uniformly introduced into the slurry pit 1 using the container bag 7 or the like. Then, by continuing the air blow for a certain time, the water 2 in the slurry pit 1 is sufficiently stirred and mixed with the regenerated fine powder 4 that has been charged, and a homogeneous solidified material slurry 5 is produced. Then, the solidified material in the slurry pit 1 is solidified to a predetermined strength with the elapse of a predetermined solidification time, and the ground improvement body 6 is created, so that the target ground is solidified in situ. It is preferable to set the air blowing time so that water and a regenerated fine powder as a solidifying material are sufficiently mixed to form a homogeneous slurry.
[0020]
As the above-described modification, the solidified material slurry can be manufactured using a pool-shaped water tank or the like installed on the ground. Also in this case, the nozzle tube 10 is erected at a predetermined interval in the stored water tank, and air blow is generated in the water of the water tank by the operation of the air compressor to produce the solidified slurry, but the predetermined quality is obtained. The solidified slurry can also be ground improved by being pumped to a ground improvement location with a mortar pump through a supply hose, or put into the improvement range with a bucket or the like.
[0021]
FIG. 4 is a perspective view showing a modified example of the nozzle tube 10. The nozzle tube 20 has air ejection holes 22 formed at predetermined intervals in the longitudinal direction of the tube, and a plurality of nozzle tubes 10 are laid side by side on the bottom surface, so that the nozzle tube 10 is erected (see FIG. 2). The effect of stirring and mixing by the same air blow can be expected with a small number. This modified example is supposed to be used when laying on the bottom of the water tank and using it to produce a solidified slurry, but laying on the bottom of the excavation space in the ground improvement range When the slurry is produced and solidified in situ, it is also possible to fill the nozzle tube with a solidifying material and embed it as it is.
[0022]
[Water-solidifying material ratio]
In the production of the solidified material slurry, in consideration of the self-hardness of the regenerated fine powder (exhibited by hydraulic action), when the regenerated fine powder is used as the solidifying material, the mass of the regenerated fine powder is regarded as the mass of the solidified material. If the ratio of the mass of water to be added is the water-solidifying material ratio W / P, it is preferable that 60% = <(or more) W / P <= (below) 150%. When W / (P + C) <60%, the amount of mixed water is insufficient and a homogeneous slurry cannot be obtained. When 150% <W / P, the gap ratio as improved soil increases and sufficient strength is exhibited. There is a problem in the ground improvement effect. For this reason, it is preferable to determine a water solidification material ratio in the above-mentioned range.
[0023]
[Set air blow time]
In the above-described slurry pit 1, it is preferable to set an appropriate air blow time in order to obtain a uniform solidified slurry having a predetermined density by mixing water and the charged solidified material. In the present invention, as can be confirmed in the following examples, the stirring time for mixing the water and the solidified material to obtain a uniform density, that is, the air blowing time is set to 30 minutes or more.
[0024]
【Example】
FIG. 5 is a relational graph showing the density of the solidified slurry for each air blowing time during the mixed production of water and regenerated fine powder. In this example, a water tank of about 1.0 m ³ is used as a mixing container, a regenerated fine powder is used as a solidifying material, and the density of the solidifying material slurry for each air blowing time in a preparation with a water solidifying material ratio W / P = 80%. It was measured. It was confirmed that a solidified material slurry having a substantially uniform density was obtained by performing the stirring action by air blow for 30 minutes or more. Further, in the same formulation, the relationship between the air blowing time and the flow value of the solidified slurry (JHS A313) was determined (FIG. 6). As shown in the figure, when the stirring action by air blow is performed for 30 minutes or more, the resulting solidified material slurry has a small decrease in flow value over time. That is, it was confirmed that the material separation resistance was sufficiently maintained within the actual workable time.
[0025]
【The invention's effect】
As mentioned above, when implementing in-situ solidification method, it can be easily manufactured at the ground improvement site for the solidified material slurry that has been produced by setting up a dedicated manufacturing plant. By solidifying in the original position where the material slurry is manufactured, the ground improvement body can be created and the ground can be improved, and the construction process can be shortened.
[0026]
In addition, in the improvement of shallow ground where powder solidified material was used, it was possible to prevent the generation of dust by using slurry instead of powder solidified material, and to construct artificial ground without deteriorating the surrounding environment, surface ground Improvement can be advanced, and the effect that it can be reliably filled even in the improved ground range of a complicated shape can be expected especially due to the characteristics of the slurry.
[0027]
Furthermore, by using fine powder as a recycled material as a valuable material, the cycle of the concrete resource circulation system can be reliably rotated, and the environmental load can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a configuration for producing a solidified material slurry according to the present invention.
FIG. 2 is a partial perspective view showing a configuration of a nozzle tube standing in a slurry pit.
FIG. 3 is an operation sequence diagram schematically showing a manufacturing process of a solidifying material slurry.
FIG. 4 is a partial perspective view showing a modified example of the nozzle tube.
FIG. 5 is a graph showing the relationship between the air blowing time and the density of the solidified slurry.
FIG. 6 is a graph showing a change with time of a decrease in the flow value of the solidified slurry corresponding to the air blowing time.
[Explanation of symbols]
1 Slurry pit 2 Water 4 Recycled fine powder (solidified material)
5 Solidifying material slurry 6 Ground improvement body 10, 20 Nozzle tube 12, 22 Air ejection hole

Claims (3)

A slurry pit is excavated in the planned improvement area of the soft ground surface, a supply pipe for injecting fine air is piped into the slurry pit, and the concrete waste is heated and ground in the water (W) stored in the slurry pit. The regenerated fine powder (P) obtained in this manner is charged in a range where the mixing ratio is 60% = <W / P <= 150%, and air blow is performed by the upward flow of fine air generated from the supply pipe. A method for producing a solidified material slurry, characterized by producing a slurry-like solidified material slurry by stirring and mixing for at least minutes . A ground improvement body, wherein the solidified material slurry filled in the slurry pits according to claim 1 is solidified and formed in a planned improvement area of the soft ground surface layer . A supply pipe for injecting fine air into the water tank is piped, and the recycled fine powder (P) obtained by heating and grinding the concrete waste material to the water (W) stored in the water tank has a mixing ratio of 60% = <W / P <= 150%, and air blow by upward flow of fine air generated from the supply pipe is performed for 30 minutes or more to produce a slurry-like solidified material slurry by stirring and mixing. A method for producing a solidifying material slurry.

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