JP2006063596A - Soil improving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil improving method which is carried out under optimum improvement conditions for target ground, by switching an improving material to be fed to an agitating and mixing apparatus from particulate material to fluid substance and vice versa in mid-course, depending on soil character or ground properties. <P>SOLUTION: The soil improving method is carried out by employing an agitation shaft 19, agitation blades 20, and a material feeding apparatus for introducing the improving material into a feeding conduit arranged along the agitation shaft 19, so that the improving material discharged from a lower discharge port of the feeding conduit is mixed with in-situ soil. According to the method, the material feeding apparatus is comprised of a particulate material force-feeding plant 1 for feeding the particulate material by compressed air, a fluid substance force-feeding plant 2 for feeding fluid substance which is a mixture of the particulate material and water, and a transport passage 7 for selectively connecting the particulate material force-feeding plant 1 or the fluid substance force-feeding plant 2 to an upstream side of the feeding conduit via switching means. Then by taking into consideration the soil character in a ground depth direction, the particulate material of the particulate material force-feeding plant 1 is force-fed to a stratum B having a high water content via the switching means 8, 9 of the transport passage 7, whereas the fluid substance of the fluid substance force-feeding plant 2 is force-fed to a stratum A having a low water content via the switching means 8, 9 of the transport passage 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention discharges an improved material (either a granular material such as cement or a fluid such as cement milk) in the ground, and an in-situ soil in the ground by a stirring blade provided below the stirring shaft. The present invention relates to a ground improvement method for improving the ground by mixing and improving materials.

 In the soft ground improvement method, a stirring shaft, a stirring blade attached to the lower side of the stirring shaft, a supply pipe line provided along the stirring shaft, and an upstream side of the supply pipe line improved on the ground surface side. A material supply device for introducing the material, and mixing the improved material discharged from the lower discharge port of the supply pipe with the in-situ soil in the process of penetration of the stirring shaft into the ground, extraction process, etc. I have to. In this method, soil at the construction site is collected in advance by boring, indoor blending experiments are performed according to the target improvement strength, safety factors are taken into consideration, and powders such as cement, or cement milk are used as improvement materials. The amount of discharge or the amount of ground mix is set. Moreover, in this construction method, when the soil property of the target ground has a high water content, the construction is performed with a granular material, and when the soil property is a low water content, the construction is performed with a fluid. In the former, powder particles are directly hydrated with water contained in the in situ soil to promote hardening. In the conventional construction method, as exemplified in Patent Document 1, when the water content ratio greatly fluctuates in the depth direction of the ground, water is added to the formation with a low water content ratio so that the hydration reaction is maintained. The soil properties may be adjusted.

Japanese Patent Laid-Open No. 10-245898

In the construction design of the ground improvement method described above, it is determined whether to use a granular material or a fluid for the target ground, and the discharge amount and the blending amount are calculated. However, the soil properties are often alternating layers whose water content ratio has changed greatly in the depth direction of the ground, so the following problems cannot be solved with improvements using only granular materials or improvements using only fluids. Has occurred.
(A) In the improvement by a granular material, if it hydrolyzes partially like the patent document 1 with respect to the formation with a low water content ratio, construction efficiency will worsen. In the sand layer, a jamming phenomenon occurs at the time of penetration, and it is difficult to pull out the stirring shaft and the stirring blade. In the loose layer of the ground, there is a possibility that the surrounding ground layer may be loosened by compressed air for pumping the granular material or an existing structure may be adversely affected. Cohesive soil has poor mixing with in-situ soil compared to fluid construction, and so-called lumps are likely to occur. When the penetration depth is deep, or when the hard clay layer is used, it becomes difficult to collect compressed air for pumping, that is, to discharge the compressed air to the ground surface. .
(B) In the improvement by the fluid, the amount of soil and mud discharged to the surface is increased compared to the powder construction due to the moisture for kneading. Kneaded water tends to remain in the soil rather than air. The amount of water necessary to harden the cement is generally about 25% of the cement weight, and the remainder is diffused into the soil.

  The object of the present invention is to solve the above-mentioned problems, as an improved material to be discharged to the in-situ soil, by switching between powder and fluid according to the soil properties in the depth direction of the ground, optimal for the ground It is to make it possible to obtain various improvement conditions.

  To achieve the above object, the present invention provides a stirring shaft rotated by a driving mechanism, a stirring blade provided below the stirring shaft, a supply pipe provided along the stirring shaft, and a ground surface side. And a material supply device that introduces an improved material upstream of the supply pipe, and is discharged from a lower discharge port of the supply pipe in the process of penetration of the stirring shaft into the ground or a drawing process. In the ground improvement construction method in which the improvement material and the in-situ soil are mixed, the material supply device includes: a powder feeding plant capable of supplying powder as compressed material by compressed air as the improved material; and a granular material as the improved material. A fluid pressure feeding plant capable of supplying a fluid mixed with water, and a transportation route capable of selectively connecting the powder pressure feeding plant and the fluid pressure feeding plant to the upstream side of the supply pipe via a switching unit. With soil properties in the depth direction of the ground In addition, the granular material of the powder pumping plant is fed to the formation with a high water content ratio, and the fluid of the fluid pressure feeding plant is pumped to the supply pipe through the switching means of the transport route to the formation with a low water content ratio. It is characterized by.

  In the construction method of the present invention described above, in the construction design, for example, according to the change in the water content ratio in the depth direction of the ground as grasped in the preliminary survey, etc., the formation A using the granular material (the formation with a high water content ratio) and the flow A stratum B (a stratum having a low water content ratio) using animals is determined, and discharge amounts (total discharge amount and discharge flow rate, etc.) of the granular material and fluid mixed in the various strata A and B are calculated. In the construction work, for example, the penetration depth of the stirring shaft is measured by the detection sensor, and based on the measured value, the powder particles are discharged to the formation A and immediately before passing through the formation A. The switching means is switched, and when reaching the formation B, the fluid is discharged and mixed with the in situ soil. In such a construction method, when switching from the fluid to the granular material, and / or when switching from the granular material to the fluid, the compressed air of the powder pumping plant is pumped to supply the transport route and supply. Switching after removing what remains or adhering to the pipeline (Claim 2), the fluid pressure feeding plant is a fluid production unit that produces a fluid by mixing granular material and water. And the fluid production unit uses the granular material sent by compressed air from the powder pressure feeding plant, and deaerates before or after mixing the granular material and water. (Claim 3) is preferable.

The above method of the present invention can have the following advantages.
In the invention of claim 1, according to the soil properties in the depth direction of the ground, the granular material is discharged to the formation with a low moisture content and the fluid is applied to the formation with a high moisture content by the switching means of the transportation route. By discharging, it is possible to realize an optimal improvement that matches the ground properties, and to eliminate the problems listed in paragraph 0004.
-In invention of Claim 2, the purity as a granular material and a fluid by removing the residue and adhering matter which remain in a transportation route or a supply pipeline using compressed air by the side of a granular pressure feed plant And the physical properties can be easily maintained, and at the same time, clogging of each part can be prevented.
-In the invention of claim 3, by supplying the powder and granular material used in the fluid production unit on the fluid pressure feeding plant side from the powder pressure feeding plant side, the equipment for powder particles is shared and the equipment is simplified. it can.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings. 1 is a schematic configuration diagram showing the entire apparatus used in the method of the present invention, FIGS. 2 and 3 are schematic operation diagrams showing main steps when the method of the present invention is carried out, and FIG. 4 is an example of carrying out the method of the present invention. It is a flowchart which shows the example of a detailed procedure when doing. FIG. 5 shows an example of a powder feeding machine of a powder feeding plant, and FIGS. 6 and 7 show two specific examples of the fluid production unit. In the following description, after describing the configuration of the ground improvement method and an example of the construction procedure, a structural example of the main part of each plant will be referred to with reference to FIGS.

(Ground improvement method) In FIG. 1, reference numeral 1 is a powder pumping plant, reference numeral 2 is a fluid pumping plant, and 3 is a stirring and mixing device installed on the surface of the target ground. In addition, the target soil has a detailed understanding of the soil properties in the depth direction by prior geological surveys, and the water content ratio is deeper than ultra-soft or soft strata A with a low water content ratio from the surface to the predetermined depth. It consists of a relatively hard formation B with a high height. In addition, in this form, although the granular material assumes cement, other than this may be sufficient. The fluid is assumed to be cement milk in which cement and water are mixed, but any fluid may be used as long as it is similar to cement milk.

  Here, the powder pumping plant 1 includes at least a silo 4 storing cement, a compressor 5 for supplying compressed air, and a powder pump 6. Among these, the powder pressure feeder 6 receives the cement from the silo 4, mixes the cement with the compressed air generated by the compressor 5, and pumps the cement using the compressed air as a transport medium. The outlet of the powder pressure feeder 6 is disposed along the agitation shaft 19 on the agitation and mixing device 3 side via the transport path 7 and the first switching valve 8 and the second switching valve 9 provided in the transport path 7. It is connected to the upper end side of a supply pipe (not shown) that can be switched. The outlet of the compressor 5 is connected to the transport path 7 via the bypass path 15 and the bypass valve 16. The bypass flow path 15 enables compressed air generated by the compressor 5 to be directly pumped into the transport path 7 via the bypass valve 16, so that the transport path 7, the supply pipe line in the stirring shaft 19, and the supply pipe line Cement, cement milk, or the like remaining or adhering to a discharge port such as a nozzle provided at the lower end is discharged out of the system, and for example, clogging of each part after switching can be prevented in advance. Actually, the compressed air generated by the compressor 5 can be heated by a dryer (not shown), and when the residue or deposits are discharged, the heated compressed air is generated and pumped. It is like that.

  The fluid pressure feeding plant 2 includes a mixer 10 that is a fluid production unit that is switchably connected via a first switching valve 8 provided in the transport path 7, and a water tank 11 that supplies water into the mixer 10. And a grout pump 13 for supplying water-cement cement milk mixed in the mixer 10 at a predetermined mixing ratio from the transport path 12 to the transport path 7 side. Of these, the mixer 10 is configured to discharge the compressed air for transporting the powder supplied together with the cement to the atmosphere side through the dust collector 14 before or after mixing. The downstream side of the transport path 12 is connected to the downstream side of the transport path 7 via the second switching valve 9, and is arranged along the stirring shaft 19 on the stirring and mixing device 3 side via the transport path 7. It is connected to the upper end side of the supply pipeline that can be switched. In practice, a path (not shown) for compressing compressed air is provided between the base end side in the transport path 12 and the compressor 5, and residues and deposits in the transport path 12 can be discharged by the compressed air. It has become.

  The stirring and mixing device 3 includes a caterpillar traveling type base machine 16, a tilting vertical guide 17 erected at the tip of the base machine 16, and a driving head 18 that is a rotary driving mechanism that can be moved up and down along the guide 17. And a stirring shaft 19 suspended rotatably below the drive head 18 and a plurality of stirring blades 20 projecting from the outer periphery of the lower end of the stirring shaft 19, the connecting end of the transport path 7 being the drive head 18 is connected to a supply pipe line in the stirring shaft 19 through a swivel joint 18a attached to 18 and connected to the lower end of the supply pipe line so as to be attached around the lower end of the stirring shaft 19 and on the stirring blade 20 side. This is a configuration in which cement that is powder or cement milk that is fluid is ejected from a discharge port such as a nozzle. The drive head 18, the stirring shaft 19, the stirring blade 20, and the like are schematically shown, but these are the same as or similar to those in Patent Document 1.

(Example of construction procedure) Next, the construction procedure will be described with reference to the flowcharts of FIGS. First, in this embodiment, as described above, a layer from the ground surface to a predetermined depth is a soft formation A having a high moisture content, and a lower layer is a relatively hard formation B having a low moisture content. Moreover, it is judged that the ground improvement using the cement which is a granular material is the best in the formation A, and the ground improvement using cement milk which is a fluid is the optimum in the formation B. Note that the boundary between both strata A and B is not necessarily constant and varies somewhat depending on the location, but the boundary position can be detected by a detection sensor for penetration depth of the stirring shaft 19 or a torque sensor. Yes.

  In this implementation, first, as shown in FIG. 2 (a), in a state where the operations of the plants 1 and 2 are stopped, the stirring and mixing device 3 is driven to rotate the stirring shaft 19, and the stirring blade It penetrates while solving the surroundings by 20, and when it reaches the ground improvement depth, the penetration is stopped and the idle rotation is continued (steps ST1 to ST6). If the rotational torque changes before the penetration, the change position is recorded (steps ST3 and ST4). This position is the boundary position between both layers A and B.

  That is, normally, when the tip of the stirring shaft 19 (the lowermost stirring blade 20) descends to the boundary position between the formation A and the formation B, the penetration resistance and the rotational resistance increase, and this is detected by a torque sensor, and this detection When the value and the detection value of the penetration depth detection sensor are substantially within the boundary depth fluctuation range determined by the preliminary survey, it is determined that the boundary position has been reached, and the position is recorded. Even before reaching the boundary position, if gravel or the like is mixed in the formation A, the torque may temporarily increase. However, this is ignored because it is not within the boundary depth variation range.

  While the stirring shaft 19 continues idling, the first switching valve 8 is switched to the connection side of the fluid production plant 2 to bring the powder pressure feeding plant 1 into an operating state, and the fluid production plant 2 The operating state is set (steps ST7 to ST9). Specifically, the cement in the silo 4 is pumped into the mixer 10 via the powder pump 6 and the first switching valve 8, and the amount of water having a predetermined water-cement ratio is set in the mixer 10 from the water tank 11 side. To supply. The mixer 10 kneads the cement and water to produce cement milk.

  Thus, after cement milk is manufactured, the 2nd switching valve 9 is switched, the fluid transport path 12 is made to join the transport path 7 side, and the grout pump 13 is driven simultaneously. Thereby, the cement milk produced by the mixer 10 is jetted from a discharge port such as a nozzle through a supply pipe in the stirring shaft 19, and continues to rotate while raising the stirring shaft 19 from that state. As shown in 2 (b), a soil cement column b in which the in-situ soil and cement milk are mixed is created (steps ST10 to ST12).

  In addition, the supplied cement milk is a value according to the water content ratio, soil quality, viscosity, etc. of the formation B whose water-cement ratio and supply amount per hour (discharge amount by the pump 13) are known by the preliminary survey. In addition, it is calculated according to the ground drawing speed of the stirring shaft 19 and the rotation speed of the stirring blade 20.

  When the stirring shaft 19 rises to the previously recorded torque change position, the idle rotation is continued while stopping at that position, the operations of the plants 1 and 2 are temporarily stopped, and the first switching valve 8 and the second switching valve are stopped. 9 is closed so that the normal transportation route 7, that is, the switching valve 8 is closed with the mixer 10 side, and the switching valve 9 is closed with the transportation route 12 side (steps ST13 to ST16). Thereafter, the bypass valve 16 is switched so that the compressed air of the compressor 5 is directly ejected from the bypass flow path 15 into the transport path 7, and the residual adhering to the pipe such as the transport path 7 and the supply pipe line in the stirring shaft 19. Cement milk is discharged from the outlet. After that, the compressor 5 is temporarily stopped, the bypass valve 16 is switched, and the drive standby state is set again (steps ST17 to ST21). In addition, although the adhesion | attachment discharged | emitted and the residual cement milk are added in the soil cement pillar b, since the quantity is slight, the influence which it has on an improvement body can be disregarded.

  Next, this time, the fluid production plant 2 is stopped, only the powder pumping plant 1 is operated, and the stirring shaft 19 is raised again (steps ST22 and ST23). That is, in this process, the cement in the silo 4 is quantitatively transferred to the powder pump 6 and is accompanied by the compressed air introduced into the powder pump 6 from the compressor 5 side. It is pumped from the outlet and ejected from the discharge port on the lower end side through the supply path in the transport path 7 and the stirring shaft 19. Then, the injected cement is mixed with the in-situ soil by the action of the stirring blade 20, so that a soil cement column a is formed in the formation A as shown in FIG. The soil cement column a is formed continuously with the soil cement column b. In addition, the supply amount per hour of the cement which is the above granular material is, for example, the water content ratio of the formation A, the ground penetration speed of the stirring shaft 19, the rotational speed of the stirring blade 20, etc., which have been found by the preliminary survey. Set in consideration. Moreover, the compressed air injected as a transport medium rises to the surface side along the stirring shaft 19, and is diffused and discharged from the surface side toward the atmosphere.

  As described above, when the stirring shaft 1 is pulled up to the ground surface and the soil cement column a is formed in the formation A as shown in FIG. If the remaining cement adhering to the pipes such as the transport path 7 and the supply pipe line in the stirring shaft 19 is discharged by the same operation as Steps 17 to 21 after stopping the rotation and ascending, one or one ground The improvement work is completed (steps ST22 to ST26). After the formation, the hydration reaction proceeds and cures with time, and soil cement columns a and b that are continuously integrated in the vertical direction are formed in the ground. Thereafter, after the stirring and mixing device 3 is moved to the adjacent work area, the column of soil cement columns a and b continuously formed across the formations A and B is obtained by repeating the same operation procedure as described above. Will be formed.

  In the above embodiment, the stirrer shaft 19 is penetrated through a relatively hard formation B to a predetermined improvement depth in advance, and then the ground is improved by cement milk while pulling it up, and then in the soft formation A The ground was improved with cement. This is a general construction procedure in the stirring and mixing method. However, in the construction procedure, for example, the injection of cement or cement milk into the formation may be performed in the penetration process of the stirring shaft 19 or in the penetration and extraction process. In short, the procedure of FIG. 4 is merely an example and does not limit the present invention.

(Powder Pump) Next, an example of the detailed structure of the powder pump 6 used in the powder pumping plant 1 will be described. In FIG. 5, the powder pressure feeder 6 has a pressure vessel 32, and the upper flange 30 of the vessel 32 is supported on the installation part S via a load cell 31 as load measuring means. The container 32 has a cement receiving container portion 34 in the upper half portion and a pumping pump chamber 35 in the lower half portion with a partition wall 33 arranged inside. A hopper 36 is provided above the pressure vessel 32 so as to face the supply nozzle 4 a of the cement silo 4. In addition, a check valve 37 is disposed inside the upper portion of the pressure vessel 32 so as to face the supply port of the hopper 36 and close the supply port when the internal pressure increases. The partition wall 33 has a funnel shape. An L-shaped nozzle 38 that penetrates the side surface of the pressure vessel 32 and is connected to the compressor 5 is disposed in the opening 33 a formed in the center of the partition wall 33, and its tip is directed into the pump chamber 35. Yes.

  In the pump chamber 35, a rotor shaft 40 supported by a bearing portion 39 provided at the lower portion of the pressure vessel 32, a plurality of rotors 41 integrated on the periphery of the rotor shaft 40, and a bracket 42 at the lower portion of the pressure vessel 32. And a motor 44 for rotationally driving the rotor shaft 40 via a rotation transmission mechanism 43 such as a bevel gear. In addition, a discharge pipe 45 that protrudes from one side lower portion of the pressure vessel 32 and communicates with a corresponding portion of the pump chamber 35 and has the other end connected to the transport path 7 is provided. The discharge pipe 45 is provided with an electromagnetic valve 46, and the tip nozzle 47 of the bypass flow path 15 joins the pipe on the near side of the electromagnetic valve 46.

  In the above, when the powder pressure feeder 6 is driven, the electromagnetic valve 46 is opened, the compressor 5 is driven, compressed air is blown into the pump chamber 35 through the nozzle 38, and the motor 44 is driven to move the rotor 41. By rotationally driving, the upper receiving container portion 34 becomes negative pressure, the check valve 37 is opened, the cement led out from the supply nozzle 4a into the hopper 36 is taken in, and the pump chamber is opened through the opening 33a of the partition wall 33. Cement is sequentially put into 35, and is sent into the transport path 7 through the discharge pipe 45 using compressed air as a transport medium. During this drive, the weight in the pressure vessel 32 is constantly measured by the load cell 31, and when the weight of cement supplied from the silo 4 reaches a set value, an electromagnetic valve (not shown) provided in the supply nozzle 4a is closed. When the value is lower than the set value, the quantity of cement can be supplied by opening the electromagnetic valve, and the quantity of cement is supplied into the transport path 7 through the pump chamber 35. When the driving of the powder pressure feeder 6 is stopped, the driving of the compressor 5 and the motor 44 is stopped, and the electromagnetic valve 46 is closed.

(Fluid Manufacturing Department) The fluid manufacturing plant 2 receives the cement from the powder pumping plant 1 and kneads the cement and water. The structure example in this case is a compression used as a transport medium. This will be described with reference to FIGS.

  The structure shown in FIG. 6 is an example of a form that is open to the atmosphere. In this example, the cement pumped from the powder pumping plant 1 is deaerated before being introduced into the mixer 50 (corresponding to the mixer 10 in FIG. 1). That is, the mixer 50 is a screw type, and has a funnel-shaped cyclone 51 as a deaeration means standing at the intake, an introduction pipe 52 connected to the upper periphery of the cyclone 51, and an upper center of the cyclone 51. A suspended exhaust pipe 53 a, a dust collector 53 connected to the exhaust pipe 53 a, and a blower 54 connected to the discharge side of the dust collector 53 are provided.

  In this structure, when cement, which is a granular material, is introduced into the cyclone 51 from the introduction pipe 52 together with the compressed air, a cyclone flow is generated in the cyclone 51, and the cement having a high specific gravity spirals along the inner surface of the cyclone 51. It is dropped while drawing and is continuously introduced into the mixer 50. Further, the compressed air is guided from the cyclone 51 to the dust collector 53 side through the exhaust pipe 53 a, and is discharged to the atmosphere side through the blower 54 connected to the discharge side of the dust collector 53. The suction force of the blower 54 is substantially equal to the discharge pressure of the powder compressor 6, whereby the cement is separated from the compressed air immediately before the mixer 50. However, a small amount of cement may be mixed in the separated compressed air. The cement is separated or removed by a filter 55 disposed in the dust collector 53.

  Further, in this structure, the water in the water tank 11 is supplied to the inlet side of the mixer 50, that is, the side to which the cyclone 51 is connected via the pipe and the submersible pump 56. The pipe is provided with a flow meter 57, a flow rate adjustment valve 58, and the like. Then, the water in the water tank 11 is introduced to the inlet side of the mixer 50 via the pump 56. At this time, a predetermined water-cement ratio is set so as to have an appropriate water-cement ratio with respect to the cement that is continuously supplied in a fixed amount. The flow rate is controlled through a flow meter 57 and a flow rate adjustment valve 58 so as to be introduced by a water amount or a flow rate. The mixer 50 mixes the cement and water to be introduced with a screw to produce cement milk, which is supplied from the discharge end of the mixer 50 to the pump 13 side reservoir. The cement milk accommodated in the reservoir is pumped to the transport path 12 side via the pump 13.

  The structure of FIG. 7 is an example of a closed type. In this example, the cement pumped from the powder pumping plant 1 is introduced into a closed mixer 60 (corresponding to the mixer 10 in FIG. 1), mixed with water and manufactured into cement milk, and then deaerated. Is done. That is, the hermetic mixer 60 has a starter mixer 61 connected to the container body, water is quantitatively supplied from one end side supply port of the starter mixer 61, and a check valve is supplied from the powder pumping plant 1. Cement is supplied via 62, and is discharged into the mixer 60 while being mixed with gas and liquid in the static mixer 61. Further, the inside of the mixer 60 is divided forward and backward by a vertically arranged partition wall 63 except for the lower side. On the left side of the partition wall 63, that is, in the front space on the static mixer 61 side, stirring means 66 that is rotated by a drive motor 65 is provided. Air separation means is provided on the right side of the partition wall 63, that is, on the rear space. The rear space portion has an upper portion connected to the dust collector 64 and a lower portion connected to the pump 13 described above.

  In this structure, the mixture of cement and water supplied from the static mixer 61, that is, cement milk, is introduced into the front space of the mixer 60 and further stirred and mixed by the stirring means 66. The lower side of the partition wall 63 is open, and cement milk is introduced into the rear space portion from the lower opening. The rear space is further divided into two parts by the overflow weir 67, and when the agitated and mixed bubble-mixed cement milk exceeds the overflow weir 67, the bubbles rise and repel, and the repelled air is discharged from the upper part of the rear space. 64 to the atmosphere. The cement milk overflowing from the overflow weir 67 is cement milk from which air has been separated, and this cement milk is pumped by the pump 13 toward the transport path 12 described above. In each of the above structures, the powder pumping plant 1 can be shared as a cement supply source of the fluid production plant, so that there is no duplication of plants and the equipment can be simplified.

  In addition, the above embodiment does not restrict | limit this invention at all. The present invention may be provided with the technical elements specified in claim 1, and the details can be variously changed as necessary.

It is the schematic which shows the whole structure containing the improvement apparatus in the case of applying this invention construction method. (A), (b) is sectional explanatory drawing which shows a construction procedure. (A), (b) is sectional explanatory drawing which shows the construction procedure following FIG. It is a flowchart which shows the detail of the said construction procedure. It is sectional drawing which shows the example of the powder pumping machine by the side of the powder pumping plant of this invention construction method. It is a schematic diagram which shows the structural example by the side of the fluid manufacturing plant of this invention construction method. It is a schematic diagram which shows the structural example by the side of the other fluid production plant of this invention construction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Powder pressure feeding plant 2 ... Fluid manufacturing plant 3 ... Stirring mixing apparatus (19 is a stirring shaft, 20 is a stirring blade)
5 ... Compressor (Air compressor)
6 ... powder feeder 7,12 ... transport route 8,9 ... first and second switching valves (switching means)
10, 50, 60 ... mixer (fluid production department)
DESCRIPTION OF SYMBOLS 11 ... Water tank 13 ... Pump 15 ... Bypass flow path 16 ... Bypass valve (switching means)

Claims (3)

An agitation shaft rotated by a drive mechanism, an agitation blade provided below the agitation shaft, a supply line provided along the agitation axis, and an upstream side of the supply line provided on the ground surface side A material supply device for introducing an improved material, and mixing the improved material discharged from the lower discharge port of the supply pipe with the in-situ soil in the process of penetrating and extracting the stirring shaft into the ground In the ground improvement method to
The material supply device includes: a powder pumping plant capable of supplying powder as compressed material with compressed air; and a fluid pumping plant capable of supplying a fluid obtained by mixing powder and water as the improver. A transport path capable of selectively connecting the powder pumping plant and the fluid pumping plant to the upstream side of the supply pipe via switching means,
As the soil properties in the depth direction of the ground, the granular material of the powder pumping plant is used for the formation with a high water content ratio, and the fluid of the fluid pumping plant is used for the formation with a low water content ratio. The ground improvement construction method characterized by pumping to the said supply piping through.   When switching from the fluid to powder or / and when switching from the powder to fluid, the compressed air of the powder pumping plant is pumped to remain in the transport path and supply pipeline The ground improvement construction method according to claim 1, which is switched after removing the attached material. The fluid pressure feeding plant has a fluid production unit for producing a fluid by mixing powder and water, and the fluid production unit is sent from the powder pressure feeding plant by compressed air. The ground improvement construction method according to claim 1 or 2, wherein the ground material is used and deaerated before or after mixing the powder material and water.

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