JP5320248B2 - Ground improvement management device and ground improvement construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil improvement managing device capable of properly managing the discharge flow volume and discharge pressure of fluidized sand discharged from a lower end opening of a hollow pipe, and of effectively and rationally constructing and managing a sand pile of a predetermined strength or a predetermined pile diameter by predetermined length when the sand pile is constructed in a narrow sand-pile construction area such as right below, near an existing structure, or the like. <P>SOLUTION: The soil improvement managing device is to discharge the fluidized sand containing a fluidizing agent and a slow-acting plasticizer from the lower end opening of the hollow pipe 53 penetrated into the ground 8 to a predetermined depth, so as to construct and manage the sand pile 9 by the predetermined length. After the hollow pipe 53 is penetrated into the ground 8 to the predetermined depth by an ascending/descending mechanism 52, a flow volume sensor detects the time point at which the discharge flow volume of the fluidized sand discharged from the lower end opening of the hollow pipe 53 reaches a predetermined flow volume. Based on the detected output, a signal for pulling up the hollow pipe 53 by a step length corresponding to the predetermined flow volume is automatically transmitted to the ascending/descending mechanism 52. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention is, for example, a ground improvement management device and a ground improvement method suitable for use in a compacted sand pile construction method using sand as a material that can be constructed in a narrow space such as immediately below or immediately below an existing structure under an existing quay. About.

  The compacted sand pile construction method using sand as a sand pile material is, for example, after penetrating a hollow pipe to a predetermined depth in the ground along a supporting leader as disclosed in Patent Document 1 and the like In this method, the process of drawing out the hollow pipe as appropriate and the process of re-penetrating the hollow pipe are sequentially repeated until reaching the ground surface, and compacted into a soft ground to form a sand pile, thereby improving the ground.

JP-A-8-284146 Japanese Examined Patent Publication No. 62-25808 Japanese Patent Laid-Open No. 2000-212951

  However, when constructing sand piles in a narrow sand pile construction area, such as directly under an existing structure or in the immediate vicinity, it is not possible to secure a space for operating means for supplying sand such as tire excavators. It was difficult to apply the pile construction method. In order to cope with this, there is a technology that makes it easy to flow sand as sand pile material so that it can be transported by pipe, but sand is discharged from the lower end opening of the hollow tube to form a sand pile of a predetermined pile diameter. An effective ground improvement management device that can manage the long development has not been established yet.

  Therefore, the present invention has been made to solve the above-described problems, and when a sand pile is constructed in a narrow sand pile construction area immediately below an existing structure or in the immediate vicinity, it is discharged from the lower end opening of the hollow pipe. A ground improvement management device capable of appropriately and reasonably managing a sand pile having a predetermined strength or a predetermined pile diameter by appropriately managing the discharge flow rate and discharge pressure of the fluidized sand, and adjacent to it It aims at providing the ground improvement construction method which can suppress the displacement of the ground around the existing structure (henceforth "close structure").

  According to the first aspect of the present invention, the sand pile is managed to have a predetermined length by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow pipe penetrating to a predetermined depth in the ground. The ground improvement management apparatus according to claim 1, wherein the flow rate of the fluidized sand discharged from the lower end opening of the hollow pipe after the hollow pipe has been penetrated to a predetermined depth in the ground through an elevating mechanism. Is detected, and a signal for pulling out the step width corresponding to the predetermined flow rate is automatically transmitted to the lifting mechanism based on the detection output. And

  According to the invention of claim 2, fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent is discharged from a lower end opening of a hollow pipe penetrating to a predetermined depth in the ground so that a sand pile is managed for a predetermined length. The ground improvement management apparatus according to claim 1, wherein the fluidized sand is discharged from a lower end opening of the hollow pipe after the hollow pipe has been penetrated to a predetermined depth in the ground through an elevating mechanism. Is detected, and a signal for extracting a predetermined step width of the hollow tube is automatically transmitted to the lifting mechanism based on the detected output.

  According to the invention of claim 3, the sand pile is managed to have a predetermined length by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow tube penetrating to a predetermined depth in the ground. The ground improvement management apparatus according to claim 1, wherein the flow rate of the fluidized sand discharged from the lower end opening of the hollow pipe after the hollow pipe has been penetrated to a predetermined depth in the ground through an elevating mechanism. Alternatively, the time when the discharge pressure reaches a predetermined flow rate or a predetermined pressure is detected, and a signal for pulling out the hollow tube by a predetermined step width is automatically transmitted to the lifting mechanism based on the detection output. It is characterized by.

  The invention according to claim 4 is the ground improvement management device according to claim 1, wherein a signal for vertically moving the hollow tube until the discharge flow rate reaches a predetermined flow rate while pulling out the step width is automatically sent to the lifting mechanism. It is characterized by being transmitted.

  According to the invention of claim 5, the sand pile is formed to a predetermined length by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow tube penetrating to a predetermined depth in the ground. In this ground improvement method, after penetrating the hollow tube to a predetermined depth in the ground through a lifting mechanism, by the discharge flow rate of the fluidized sand discharged from the lower end opening of the hollow tube, When a displacement occurs in the adjacent structure, the time when the allowable displacement set in advance in the adjacent structure is reached is detected, and the fluidized sand discharged from the lower end opening of the hollow tube is detected based on this detection output. By stopping the discharge flow rate for a predetermined time, the displacement of the adjacent structure is suppressed to an allowable value or less due to the change of the fluidized sand.

  According to the sixth aspect of the present invention, a sand pile is formed to a predetermined length by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow tube that penetrates to a predetermined depth in the ground. In this ground improvement method, after penetrating the hollow tube to a predetermined depth in the ground through an elevating mechanism, by the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow tube, When a displacement occurs in the adjacent structure, the time when the allowable displacement set in advance in the adjacent structure is reached is detected, and the fluidized sand discharged from the lower end opening of the hollow tube is detected based on this detection output. By returning the discharge pressure to 0 (zero) for a certain time, the displacement of the fluidized sand suppresses the displacement of the adjacent structure to an allowable value or less.

  According to the seventh aspect of the present invention, a sand pile is formed to a predetermined length by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow pipe that penetrates to a predetermined depth in the ground. In the ground improvement method, the flow rate or discharge rate of the fluidized sand discharged from the lower end opening of the hollow tube after the hollow tube has been penetrated to a predetermined depth in the ground via an elevating mechanism. When a displacement occurs in the adjacent structure due to the pressure, a time point at which a permissible displacement amount set in advance in the adjacent structure is reached is detected, and a flow discharged from the lower end opening of the hollow tube based on this detection output Stopping the displacement of the adjacent structure to an allowable value or less by changing the fluidized sand by stopping the discharge flow rate of the fluidized sand for a certain time or returning the fluidized sand discharge pressure to 0 for a certain time. To do.

  The invention of claim 8 is the ground improvement construction method according to claim 5 to claim 7, wherein a time for stopping the discharge flow rate or discharge pressure of the fluidized sand discharged from the lower end opening of the hollow tube for a certain period of time, It is characterized in that it is determined from the value obtained from the hydraulic conductivity from the particle size distribution of the ground to be improved.

  As described above, according to the first aspect of the present invention, the fluidized sand discharged from the lower end opening of the hollow pipe after the hollow pipe has been penetrated to a predetermined depth in the ground via the lifting mechanism. By detecting when the discharge flow rate reaches a predetermined flow rate and automatically sending a signal to pull out the step width corresponding to the predetermined flow rate to the lifting mechanism based on this detection output, When building a sand pile in a narrow sand pile construction area, such as directly under or near the structure, by controlling the discharge flow rate of fluidized sand discharged from the lower end opening of the hollow pipe, it has a predetermined strength or a predetermined pile. It is possible to effectively and reasonably manage and create a sand pile with a diameter. In addition, it is only necessary to manage the discharge flow rate of the sand pile material from the lower end opening of the hollow tube, and management of the drawing speed etc. of the hollow tube becomes unnecessary, so the number of overall construction management can be reduced accordingly. It is possible to construct a sand pile having a predetermined length and a predetermined diameter easily and reliably at low cost.

  According to the invention of claim 2, after the hollow tube has been penetrated to a predetermined depth in the ground via the lifting mechanism, the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow tube is a predetermined pressure. Is detected, and a signal for pulling out the predetermined step width of the hollow tube is automatically transmitted to the lifting mechanism based on the detection output, so that a narrow space such as directly below or near the existing structure is obtained. When creating sand piles in the sand pile construction area, the sand piles with the specified strength can be effectively and reasonably managed for a specified length by simply controlling the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe. can do. Moreover, it is only necessary to control the discharge pressure of the sand pile material from the lower end opening of the hollow pipe, and management of the drawing speed of the hollow pipe becomes unnecessary, so the total number of construction management can be reduced accordingly. A sand pile having a predetermined length and a predetermined strength can be easily and reliably produced at a low cost.

  According to the invention of claim 3, the flow rate or pressure of the fluidized sand discharged from the lower end opening of the hollow tube after the hollow tube has been penetrated to a predetermined depth in the ground via the lifting mechanism is By detecting when a predetermined flow rate or a predetermined pressure is reached and automatically sending a signal for pulling out the predetermined step width of the hollow tube to the lifting mechanism based on this detection output, When constructing a sand pile in a narrow sand pile construction area, such as directly underneath or nearest, just managing the discharge flow rate and discharge pressure of fluidized sand discharged from the lower end opening of the hollow pipe will give a predetermined strength or a predetermined pile. It is possible to effectively and reasonably manage and create a sand pile with a diameter. Moreover, it is only necessary to manage the discharge flow and discharge pressure of the sand pile material from the lower end opening of the hollow pipe, and management of the drawing speed etc. of the hollow pipe becomes unnecessary, thereby reducing the total number of construction management. Therefore, a sand pile having a predetermined length, a predetermined diameter or a predetermined strength can be easily and reliably produced at a low cost.

  According to the fourth aspect of the present invention, the signal for moving the hollow pipe up and down is automatically transmitted to the lifting mechanism until the discharge flow rate reaches a predetermined flow rate while pulling out the step width. The effect can be further enhanced, and a sand pile having a predetermined length and a predetermined diameter can be easily and reliably created with well-compacted sand.

  According to the invention of claim 5, by stopping the discharge flow rate of the fluidized sand for a certain period of time, using the dewatering function of the fluidized sand and using the dissipation time of the pore water pressure, The displacement can be reliably reduced. Thereby, even when the construction is performed directly under or near the adjacent structure, the displacement control for the adjacent structure is facilitated, and there is an effect that an auxiliary construction method for the displacement control is not required.

  According to the invention of claim 6, the discharge pressure of fluidized sand is returned to 0 for a certain time, the dewatering function of fluidized sand is used, and the dissipation time of pore water pressure is used to The displacement of the ground can be reliably reduced. Thereby, even when the construction is performed directly under or near the adjacent structure, the displacement control for the adjacent structure is facilitated, and there is an effect that an auxiliary construction method for the displacement control is not required.

  According to the seventh aspect of the present invention, the fluidized sand discharge flow rate is stopped for a certain period of time or the fluidized sand discharge pressure is returned to zero for a certain period of time to use the fluidized sand dewatering function, and the pore water pressure dissipation time. By using this, the displacement of the ground around the adjacent structure can be reliably reduced. Thereby, even when the construction is performed directly under or near the adjacent structure, the displacement control for the adjacent structure is facilitated, and there is an effect that an auxiliary construction method for the displacement control is not required.

  According to the invention of claim 8, by determining the time for stopping the discharge flow rate or discharge pressure of the fluidized sand for a certain time from the value obtained by determining the hydraulic conductivity from the particle size distribution of the ground to be improved, until the fluidized sand is dewatered. By effectively using this time and performing the next step, it is possible to easily and reliably suppress the displacement of the adjacent structure below the allowable value.

It is a schematic structure figure showing a sand pile creation system of an embodiment of the present invention. It is a front view of the fluidization sand production plant used for the above-mentioned sand pile creation system. It is a side view of the said fluidization sand production plant. It is explanatory drawing of the calculating part of the said fluidization sand production plant. (A) is a schematic diagram of the fluidized sand produced in the fluidized sand production plant, (b) is a schematic diagram showing a state in which the fluidized sand is plasticized, and (c) is a diagram of the fluidized sand. It is a schematic diagram which shows the plasticized state. It is a principal part circuit block diagram of the control system of the ground improvement management apparatus used for the said sand pile creation system. It is a figure which shows an example of the screen displayed on the instrument panel of the said ground improvement management apparatus. It is a figure which shows the other example of the screen displayed on the instrument panel of the said ground improvement management apparatus. It is a flowchart at the time of the sand pile creation by the program of the said ground improvement management apparatus. It is a figure which shows an example of the management data in the said ground improvement management apparatus. It is a figure which shows the other example of the management data in the said ground improvement management apparatus. It is a figure which shows another example of the management data in the said ground improvement management apparatus. It is explanatory drawing which shows the step construction of the sand pile construction method using the said fluidization sand. It is expansion explanatory drawing of the principal part of the said step construction. It is expansion explanatory drawing of the principal part which added wave construction to the said step construction. It is explanatory drawing which shows the relationship between the depth of a hollow pipe, the flow volume of fluidized sand, pore water pressure, and the displacement of the ground by standard construction which carries out construction continuously in the sand pile construction method using the fluidized sand. It is explanatory drawing which shows the relationship between the depth of a hollow pipe, the flow volume of fluidized sand, a pore water pressure, and the displacement of the ground by construction performed by temporarily stopping construction in the sand pile construction method using the fluidized sand. It is a conceptual diagram which shows the measurement state of the displacement of a proximity | contact structure and a ground by construction performed by temporarily stopping construction in the sand pile construction method using the fluidized sand.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a sand pile creation system according to an embodiment of the present invention, FIG. 2 is a front view of a fluidized sand production plant used in the sand pile production system, and FIG. 3 is a side view of the fluidized sand production plant. 4 and FIG. 4 are explanatory diagrams of the calculation unit of the fluidized sand production plant, FIG. 5A is a schematic diagram of fluidized sand produced at the fluidized sand production plant, and FIG. 5B is the fluidized sand. Fig. 5 (c) is a schematic diagram showing a state where the sand is plasticized, Fig. 5 (c) is a schematic diagram showing a state where the fluidized sand is plasticized, and Fig. 6 is a control of the ground improvement management device used in the sand pile building system. FIG. 7 and FIG. 8 are diagrams showing examples of screens displayed on the instrument panel of the ground improvement management device, and FIG. 9 is a flowchart at the time of sand pile creation by a program of the ground improvement management device 10 to 12 show examples of management data in the ground improvement management device. , FIG. 13 is an explanatory view showing step construction of the sand pile construction method using the fluidized sand, FIG. 14 is an enlarged explanatory view of the main part of the step construction, and FIG. 15 is a diagram in which wave construction is added to the step construction. FIG.

  As shown in FIG. 1, a sand pile creation system 1 includes a fluidized sand production plant 10 and a fluidized sand containing a fluidizing agent R and a slow-acting plasticizing agent T produced by the fluidized sand production plant 10. The ground 8 for improving the ground has a pump 5 for pumping 7 'to the fluidized sand supply pipe (supply pipe) 2 and a hollow pipe 53 connected to the fluidized sand supply pipe 2 via a swivel 54. A small construction machine main body 50 for creating a sand pile 9 is provided. A flow rate / pressure gauge 3 is attached in the middle of the fluidized sand supply pipe 2.

  As shown in FIG. 1, the fluidized sand production plant 10 is installed in a place away from the sand pile formation area 4, and water W, a fluidizing agent R, and a slow-acting effect are added to sand (sand pile material) 7 used for ground improvement. The plasticizing agent T is mixed and stirred to produce fluidized sand 7 '. As shown in FIGS. 1 to 3, the fluidized sand production plant 10 is attached to a plant main body 11 including an upper frame base 11 a and a lower frame base 11 b, and an upper frame base 11 a of the plant main body 11. Of the plant body 11, and the sand 7 containing the mixed water W, the fluidizing agent R and the slow-acting plasticizing agent T are agitated. An agitator for storing fluidized sand 7 'comprising water W, sand 7, fluidizer R, and slow-acting plasticizer T, which is attached to the upper side of the lower frame base 11b and stirred by the biaxial paddle mixer 12. A fluidizing agent agitation tank 20 which is attached to the tank 15 and the upper stage frame base 11a and agitates the stock solution of the fluidizing agent R and the water W, and is attached to the lower side of the lower stage frame base 11b, and the fluidizing agent agitation tank 20 To supply fluidizing agent R to Compressed air (air) for supplying the fluidizing agent R diluted with the water W in the fluidizing agent stirring tank 20 to the biaxial paddle mixer 12 under pressure, attached to the agent pump unit 25 and the upper frame base 11a. ) An air tank 30 for storing E, an air compressor 32 for supplying compressed air E to the air tank 30 and the like, and a lower shaft base 11b. 12, a slow-acting plasticizer pump unit 35 for supplying a slow-acting plasticizer T, an operation panel 40 attached to one side surface of the lower frame base 11b, and a palite 45 attached to the other side surface of the upper frame base 11a. And.

  As shown in FIGS. 2 and 3, the biaxial paddle mixer 12 is provided with a pair of load cells 13 and 13 for weighing the weight of the sand 7 introduced by the backhoe 6 from the upper surface side opening 12 a. Further, the water W in the water storage tank 14 is supplied to the upper surface side opening 12a of the biaxial paddle mixer 12 through the water supply pipe 14a and the pressure feed pump 14b. Then, the sand 7 containing water W mixed by the biaxial paddle mixer 12 is added with a fluidizing agent R and a slow-acting plasticizing agent T and stirred to become fluidized sand 7 '. The agitator tank 15 is supplied and stored by opening a valve (open / close valve) (not shown) provided in the opening 12b. In addition to the pressure pump 14b, a valve 14c is attached to the water supply pipe 14a.

  As shown in FIGS. 2 and 3, the agitator tank 15 is formed in a bottomed cylindrical shape having an upper surface opened, and a stirring shaft 16 having a stirring blade 17 at the center thereof is rotatably supported. . A chain 19 is spanned between a sprocket 16 a attached to the lower end of the stirring shaft 16 and a sprocket 18 b attached to the output shaft 18 a of the motor 18, and the stirring blade 17 is integrated with the stirring shaft 16 by driving the motor 18. It is designed to rotate.

  As shown in FIG. 2, the fluidizer stirring tank 20 includes a stirring shaft 22 that is rotated by a motor 21. A stirring blade 22 a is attached in the middle of the stirring shaft 22. An air supply port 23a for compressed air E is provided on the upper side of the fluidizing agent agitation tank 20, and a water supply port 23b for water W and a stock solution supply port 23c for fluidizing agent R are provided. Further, a fluidizing agent supply pipe 24 for supplying the fluidizing agent R diluted with water W to the biaxial paddle mixer 12 is provided on the lower end side of the fluidizing agent stirring tank 20. A valve 24 a is attached to the fluidizing agent supply pipe 24.

  As shown in FIGS. 2 and 3, the fluidizing agent pump unit 25 includes a fluidizing agent stock solution storage tank 26 that stores a stock solution of the fluidizing agent R, and a fluidizing agent R in the fluidizing agent stock solution storage tank 26. A raw solution supply pipe 27 and a pressure feed pump 28 for supplying the stock solution to the fluidizing agent stirring tank 20, and a water supply pipe 29 a and a pressure feed pump 29 b for supplying the water W in the water storage tank 14 to the fluidizing agent stirring tank 20. ing. A valve 27 a is attached to the stock solution supply pipe 27. In addition to the pressure pump 29b, a flow meter 29c and a valve 29d are attached to the water supply pipe 29a. The fluidizing agent R facilitates the flow of the sand 7 as the sand pile material so that it can be transported by pipe, and a water-absorbing polymer, a polymer agent or the like is suitable.

  As shown in FIG. 3, the slow-acting plasticizer pump unit 35 includes a slow-acting plasticizer storage tank 36 that stores the slow-acting plasticizer T, and a slow-acting plasticization in the slow-acting plasticizer storage tank 36. A slow-acting plasticizer supply pipe 37 for supplying the agent T to the biaxial paddle mixer 12 and a pressure pump 38 are configured. A valve 39 is attached to the slow-acting plasticizer supply pipe 37.

  The slow-acting plasticizing agent T is used for ensuring fluidity both during pumping and during press-fitting (discharge) and for controlling the time until plasticizing (returning to the original sand property). A synthetic polymer agent or the like is preferred. Next, the plasticization of the slow-acting plasticizing agent T will be described with reference to FIGS. 5A to 5C. As shown in FIG. 5A, the fluidizing agent R and the slow-acting plasticizing agent T are used. The fluidized sand 7 ′ containing the sand is a state in which the fluidizing agent R that bonds the particles K and K of the sand 7 extends to form a network, and holds the slow-acting plasticizing agent T and water W, From this state, as shown in FIG. 5 (b), the fluidizing agent R that connects the particles K and K is contracted by the physical pressurization of the pumping pump 5, so that the slow-acting plasticizing agent T is formed. When touched, since the molecular bonds are decomposed and the retained water is discharged, the fluidized sand 7 'returns to the sand 7 having the original particle size shown in FIG. 5 (c).

  As shown in FIGS. 2 and 4, the operation panel 40 starts or stops the operation of the fluidized sand production plant 10 by operating a button (not shown), and includes a calculation unit 41 inside. . In this calculation unit 41, the amount of water added to the biaxial paddle mixer 12 is determined by calculation, and the amount of fluidizing agent and the amount of slow-acting plasticizer supplied to the biaxial paddle mixer 12 are respectively determined by calculation. Further, the calculation unit 41 determines the stirring time of the biaxial paddle mixer 12 after adding the fluidizing agent R and the stirring time of the biaxial paddle mixer 12 after adding the slow-acting plasticizing agent T by calculation. Further, the calculation unit 41 is connected to the patrol light 45 and the abnormality detection buzzer 46. This patrol light 45 turns on the blue light that can be thrown in when the load cell 13 of the biaxial paddle mixer 12 is reset to “0 kg”, and turns red when the sand is thrown above the set value and no more sand can be thrown in. Is turned on, and a yellow light is turned on at an emergency stop or the like. Further, the abnormality detection buzzer 46 sounds an alarm to inform the operator that no material has been produced for some reason.

  As shown in FIGS. 1 and 3, the agitator tank 15 of the fluidized sand production plant 10 includes a fluidized sand supply pipe 2, a flow rate / pressure gauge 3, a pumping pump 5, and a swivel 54. The small construction machine main body 50 is connected to the upper end of the hollow tube 53.

  As shown in FIG. 1, the small construction machine main body 50 has a reader 51 on the front side thereof. The reader 51 stands vertically with respect to the ground surface of the ground 8, and a hollow tube 53 is disposed along the leader 51 via an elevating mechanism 52 so as to be movable up and down. The fluidized sand 7 ′ containing the fluidizing agent R and the slow-acting plasticizing agent T produced and pumped from the fluidized sand production plant 10 is discharged (discharged) from the lower end opening of the hollow tube 53. Then, it is press-fitted and left in the ground of the ground 8.

  The elevating mechanism 52 holds the hollow tube 53 and moves the hollow tube 53 up and down into the ground 8 by driving means such as an elevating motor (not shown). As shown in FIG. 6, the elevating mechanism 52 is provided with a hydraulic pressure sensor 55 that detects the oil pressure during the elevating operation of the hollow tube 53. Further, the elevating mechanism 52 is provided with a depth meter 56 that detects the depth of the lower end of the hollow tube 53.

  The hollow tube 53 is formed in a cylindrical shape, and a swivel 54 is attached to the upper end thereof. The hollow pipe 53 is provided with a pressure sensor 57 for detecting the discharge pressure of the fluidized sand 7 'discharged from the lower end opening thereof and a flow rate sensor 58 for detecting the discharge flow rate of the fluidized sand 7'. .

  Next, the control system of the ground improvement management device 60 will be described.

  As shown in FIG. 6, the detection outputs of the hydraulic sensor 55, the depth meter 56, the pressure sensor 57, and the flow rate sensor 58 are input to the control unit 59, and the control unit 59 is based on these information and the like. The lifting / lowering mechanism 52 and the pressure feed pump 5 of the sand pile forming system 1 are automatically controlled. That is, the discharge pressure of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is detected by the pressure sensor 57 provided in the hollow tube 53, and the discharge pressure of the fluidized sand 7 ′ is a predetermined pressure. Is reached, a signal for pulling out the predetermined step width of the hollow tube 53 is automatically transmitted to the lifting mechanism 52 based on the detection output of the pressure sensor 57, and the lifting mechanism 52 causes the hollow tube 53 to have a predetermined step width (for example, , The step length is 20 cm) and automatically moves to the next step.

  Further, the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is detected by a flow rate sensor 58 provided in the hollow tube 53, and the discharge flow rate of the fluidized sand 7 ′ is a predetermined flow rate. When a predetermined amount (for example, 100 L / min) is reached, a signal for pulling out the predetermined step width corresponding to the predetermined flow rate is automatically transmitted to the lifting mechanism 52 based on the detection output of the flow sensor 58. Then, the hollow tube 53 is pulled out by the elevating mechanism 52 by a predetermined step width (for example, a step length of 20 cm) and automatically moves to the next step.

  Further, detection information and the like of the various sensors 55 to 58 are displayed on the instrument panel (monitor) 61 provided at the position of the driver's seat of the construction machine body 50 via the control unit 59. Examples of screens displayed on the instrument panel 61 are shown in FIGS. Each screen of the instrument panel 61 displays the setting items such as the depth of the hollow tube 53, the ascending / descending speed, the discharge flow rate, the discharge pressure, the integrated amount of the discharge amount, the setting change, and the like. 59 is automatically controlled by a program of construction management software (software corresponding to the reference numeral 62 in FIG. 9) built in 59. That is, as shown in FIG. 7, the pile item setting screen of the instrument panel 61 displays setting items to be input, information for each construction step, and the like. As shown in FIG. 8, the integration screen of the instrument panel 61 displays the discharge flow rate, discharge pressure, and the like of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53. Furthermore, on the setting change screen (not shown) of the instrument panel 61, changed items such as the step width, wave width, discharge flow rate, discharge pressure, etc. of the hollow tube 53 are displayed. It can be changed by the instrument panel 61 at the seat. Accordingly, the operator of the construction machine main body 50 can grasp, monitor and manage the status of the sand pile creation work at the driver's seat by the instrument panel 61 of the ground improvement management device 60.

  Next, the sand pile creation work by the ground improvement management device 60 will be described based on the schematic configuration diagram of the sand pile creation system 1 in FIG. 1, the flow in FIG. 9, and the management data in FIGS.

  First, before starting the sand pile creation, the depth of the hollow tube 53, the growth, and the blanking so that the drawing creation by the hollow tube 53 is automatically controlled by the program of the control unit 59 of the ground improvement management device 60. The length, the press-fitting amount (discharge amount) per step, the target pressure, and the like are input in advance to the instrument panel 61 of the ground improvement management device 60. Further, fluidized sand 7 'containing a fluidizing agent R and a slow-acting plasticizing agent T is used as a sand pile material.

  Next, as shown in FIGS. 1 and 9, the construction machine main body 50 is placed in a narrow sand pile creation area 4 directly below or near the existing structure far away from the fluidized sand production plant 10 of the sand pile creation system 1. It moves to a predetermined construction position, and the raising / lowering mechanism 52 is driven to start an initial penetration process for penetrating the hollow tube 53 into the ground 8 (step S1). Then, the depth meter 56 always checks whether the lower end opening of the hollow tube 53 has reached a predetermined depth L (GL) (step S2), as shown in the depth locus (GL locus) in FIG. When the lower end opening of the hollow tube 53 reaches a predetermined depth L (for example, −3 m), the initial penetration process is terminated (step S3).

  Next, the fluidized sand 7 ′ produced in the fluidized sand production plant 10 is pumped to the hollow pipe 53 of the construction machine main body 50 through the fluidized sand supply pipe 2, the pressure pump 5 and the swivel 54, The press-fitting process of discharging (discharging) the fluidized sand 7 'from the lower end opening of the pipe 53 and press-fitting and leaving it in the ground of the ground 8 is started (step S4).

  Next, whether or not the discharge amount of the fluidized sand 7 ′ projected from the lower end opening of the hollow tube 53 by the flow rate sensor 58 has reached a predetermined discharge amount, or the lower end of the hollow tube 53 by the pressure sensor 57. It is always checked whether or not the discharge pressure of the fluidized sand 7 'protruding from the opening has reached a predetermined pressure (step S5), and the detection value of either the flow sensor 58 or the pressure sensor 57 is determined in advance. When the set value is reached, the elevating mechanism 52 is driven to automatically pull out the hollow tube 53 by a predetermined step width (step S6). The process of pulling out the hollow tube 53 by a predetermined step width is sequentially repeated a predetermined number of steps to check whether the hollow tube 53 has reached a predetermined construction base surface (step S7). When the predetermined construction base surface is reached, creation of the sand pile 9 is completed.

  As described above, according to the sand pile creation method by the ground improvement management device 60 of the sand pile creation system 1, the operator of the construction machine main body 50 can operate the instrument panel 61 of the ground improvement management device 60 or perform a simple work to monitor. The situation of the construction work of the sand pile 9 can be grasped at the driver's seat and managed. As a result, when the sand pile 9 is created in the narrow sand pile construction area 4 directly below or near the existing structure far away from the fluidized sand production plant 10 of the sand pile creation system 1, the lower end of the hollow pipe 53. By appropriately managing the discharge flow rate and discharge pressure of the fluidized sand 7 ′ discharged from the opening, the sand pile 9 having a predetermined strength or a predetermined pile diameter can be managed effectively and reasonably for a predetermined length.

  Next, the specific example of the step construction of the sand pile construction method by the ground improvement management apparatus 60 of the sand pile construction system 1 is demonstrated using FIG.13 and FIG.14. In this step construction, fluidized sand 7 'containing a fluidizing agent R and a slow-acting plasticizing agent T is used as a sand pile material.

  First, as shown in FIG. 13A, the hollow tube 53 is penetrated to a predetermined depth (for example, −2.0 mm) in the ground 8. Next, as shown in FIG. 13 and FIG. 14A, the hollow tube 53 is stopped at this depth, and in this stopped state, the fluidized sand 7 ′ is set to a predetermined set amount from the lower end opening of the hollow tube 53. (For example, 100 L / min) The discharge is continued and the fluidized sand 7 ′ is pressed into the ground and left.

  Next, as shown in FIG. 13 and FIG. 14B, the hollow tube is allowed to pass through a predetermined step width S (for example, a step length) while fluidized sand 7 ′ is being discharged from the lower end opening of the hollow tube 53. Pull out 20 cm). Even in the process of pulling out the hollow tube 53, the fluidized sand 7 'is continuously discharged by a predetermined set amount (for example, 100 L / min), and the fluidized sand 7' is pressed into the ground and left.

  Then, the hollow tube 53 is stopped and the fluidized sand 7 ′ is discharged from the lower end opening of the hollow tube 53 by a set amount, and the fluidized sand 7 ′ is discharged from the lower end opening of the hollow tube 53. In this state, the hollow pipe 53 is pulled out by a predetermined step width and the process B is repeated alternately (C, D, E...) And the sand pile 9 having a predetermined length and a predetermined diameter (for example, 70 cm in diameter) is repeated. Create.

  At this time, the water retained by the physical pressurization of the pressure pump 5 is discharged, and the fluidizing agent R that joins the particles K and K constituting the fluidized sand 7 'is contracted and is delayed. Since the contact with the plasticizing agent T breaks down the molecular bonds and returns to the sand 7 having the original particle size shown in FIG. Can be created.

  Further, since the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is detected by the flow sensor 58, the discharge amount of the fluidized sand 7 ′ is automatically determined by this detection output. When accumulated and a predetermined set amount of fluidized sand 7 'is supplied, the hollow tube 53 is automatically pulled out by a predetermined step width. The accumulated amount of the fluidized sand 7 'discharged at each construction step is displayed on the accumulated screen of the instrument panel 61 of the ground improvement management device 60 provided to the operator of the construction machine body 50. The state of the sand pile creation work can be easily grasped at the driver's seat by the panel 61, and can be monitored and managed.

  Thus, in the step (A, C, E...) For stopping the hollow tube 53 penetrated to a predetermined depth in the ground 8 and the step (B, D...) For extracting the hollow tube 53 to the ground surface side. A predetermined set amount of fluidized sand 7 'is pressed into and left in place, so that each step ([1], [2], [3]) from the lower end opening of the hollow tube 53 Since only the discharge flow rate of the fluidized sand 7 'needs to be managed and the management of the drawing speed of the hollow tube 53 is not required, the number of construction management can be reduced correspondingly, and the sand pile formation can be reduced. Cost can be further increased. In addition, when the sand pile 9 is created in the narrow sand pile construction area 4 immediately below the existing structure or the nearest by the instrument panel 61 provided to the operator of the construction machine main body 50, the lower end opening of the hollow tube 53 is opened. By appropriately managing the discharge flow rate and discharge pressure of the fluidized sand 7 ′ discharged from the sand, the sand pile 9 having a predetermined strength or a predetermined pile diameter can be effectively and rationally managed for a predetermined length.

  Next, a specific construction method in which wave construction is added to the step construction will be described with reference to FIG.

  First, as shown in FIG. 15A, the hollow tube 53 is penetrated to a predetermined depth (for example, −2.0 mm) in the ground 8. Next, as shown in FIG. 15A, while the hollow tube 53 is moved up and down at a predetermined wave width H (for example, a wave length of 15 cm) at the same position at the predetermined depth, the hollow tube 53 is opened from the lower end opening. The fluidized sand 7 'is continuously discharged at a predetermined set amount (for example, 100 L / min), and the fluidized sand 7' is pressed into the ground and left.

  Next, as shown in FIG. 15B, the hollow tube is pulled out by a predetermined step width S (for example, a step length of 20 cm) while the fluidized sand 7 'is being discharged from the lower end opening of the hollow tube 53. . Also in the process B of pulling out the hollow tube 53, a predetermined set amount (for example, 100 L / min) is continuously discharged, and fluidized sand 7 'is pressed into the ground and left.

  Then, the process A in which the fluidized sand 7 ′ is discharged from the lower end opening of the hollow tube 53 while moving the hollow tube 53 up and down with a predetermined wave width at the same position at a predetermined depth, and the lower end opening of the hollow tube 53. Step B for extracting the hollow tube 53 with a predetermined step width while the fluidized sand 7 ′ is still discharged is repeated alternately (C, D, E... For example, a sand pile 9 having a diameter of 70 cm) is created.

  At this time, the water that has been retained by the physical pressurization of the pressure feed pump 5 is discharged, and the fluidizing agent R that joins the particles K and K constituting the fluidized sand 7 'is in a contracted state. Since the molecular bond is decomposed due to contact with the slow-acting plasticizing agent T, and the sand 7 having the original particle size shown in FIG. And it can be built reliably.

  Further, since the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is detected by the flow sensor 58, the discharge amount of the fluidized sand 7 ′ is automatically determined by this detection output. When accumulated and a predetermined set amount of fluidized sand 7 'is supplied, the hollow tube 53 is automatically pulled out by a predetermined wave width or step width. Since the accumulated amount of the fluidized sand 7 'for each wave and step of this construction is displayed on the integral screen of the instrument panel 61 provided to the driver of the small construction machine main body 50, this instrument panel. With 61, the status of sand pile creation work can be easily grasped at the driver's seat and monitored and managed.

  Thus, the process (A, C, E...) Of moving the hollow tube 53 penetrated to the predetermined depth in the ground 8 up and down with the predetermined wave width H at the same position and the hollow tube 53 on the ground surface side. A predetermined set amount of fluidized sand 7 ′ is pressed into the ground in the drawing process (B, D...) And left so that each wave and each step ([1], [2], [3 )), It is only necessary to manage the discharge flow rate of the fluidized sand 7 'from the lower end opening of the hollow tube 53, and the management of the drawing speed of the hollow tube 53 is not necessary, so the total number of construction managements accordingly. The cost of sand pile creation can be further reduced. In particular, the dewatering effect of the fluidized sand 7 ′ is further enhanced by alternately repeating wave construction in which the hollow pipe 53 is moved up and down with a predetermined wave width H at the same position and step construction with which the hollow pipe 53 is pulled out with a predetermined step width. Therefore, it is possible to easily and reliably build the sand pile 9 made of the sand 7 that is well compacted.

  Furthermore, according to each construction described above, after the fluidized sand 7 'is pumped from the fluidized sand production plant 10 to the hollow pipe 53 of the construction machine main body 50 by the fluidized sand supply pipe 2 and the pressure pump 5, When the sand 7 'is pressed into the ground 8 and left, the fluidized sand 7' can be plasticized and returned to the sand 7 having the original particle size. A sand pile 9 having a predetermined length and a predetermined diameter is easily and reliably produced at a low cost in the ground 8 to be liquefied in a narrow sand pile formation area 4 directly below or near an existing structure far away from the production plant 10. be able to.

  FIG. 16 is a standard construction in which the construction shown in FIGS. 13 and 14 is continuously performed in the sand pile construction method by the ground improvement management device 60 of the sand pile construction system 1, and the depth of the hollow pipe 53 and the fluidized sand 7 ′. The relationship between the discharge flow rate, the pore water pressure and the displacement of the ground 8 is shown.

  Next, with reference to FIG. 17, an explanation will be given of the construction performed by temporarily stopping the construction in the sand pile construction method by the ground improvement management device 60 of the sand pile construction system 1. In this sand pile construction method, fluidized sand 7 'containing a fluidizing agent R and a slow-acting plasticizing agent T is used as a sand pile material.

  First, after penetrating the hollow tube 53 to a predetermined depth in the ground 8 through the lifting mechanism 52, the hollow tube 53 is stopped and fluidized from the lower end opening of the hollow tube 53 in the stopped state. The sand 7 'is continuously discharged by a predetermined amount, and the fluidized sand 7' is pressed into the ground and left.

  Next, as in the case shown in FIG. 13, the hollow tube 53 is pulled out by a predetermined step width while the fluidized sand 7 ′ is being discharged from the lower end opening of the hollow tube 53. Even in the process of pulling out the hollow tube 53, the fluidized sand 7 'is continuously discharged by a predetermined amount, and the fluidized sand 7' is pressed into the ground and left. Then, the hollow tube 53 is stopped and the fluidized sand 7 ′ is discharged from the lower end opening of the hollow tube 53 by a set amount, and the fluidized sand 7 ′ is discharged from the lower end opening of the hollow tube 53. In this state, the process of pulling out the hollow tube 53 by a predetermined step width is repeated alternately.

  In the middle of the process of discharging the fluidized sand 7 ′ from the lower end opening of the hollow tube 53, an existing flow around the construction is established by the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53. When a displacement occurs in the adjacent structure 70, the time point when the allowable displacement amount set in advance in the adjacent structure 70 is reached is detected, and the program of the control unit 59 of the ground improvement management device 60 is based on this detection output. The discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is stopped for a certain time. By stopping the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow pipe 53 for a certain period of time, the change in pore water pressure due to the dewatering function of the fluidized sand 7 ′ causes the vicinity of the adjacent structure 70 to be The displacement of the ground 8 can be reduced to an allowable value or less.

  And after stopping the discharge flow rate of the fluidized sand 7 'discharged from the lower end opening of the hollow tube 53 for a certain time, discharging the set amount of fluidized sand 7' from the lower end opening of the hollow tube 53; The step of drawing out the hollow pipe 53 with a predetermined step width while discharging the fluidized sand 7 ′ from the lower end opening of the hollow pipe 53 is repeated alternately and sequentially thereafter, and a sand pile with a predetermined length and a predetermined diameter is obtained. 9 is created.

  At this time, the time for stopping the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 for a certain time is determined from the value obtained from the water permeability coefficient from the particle size distribution of the improvement target ground. In addition, if necessary, dynamic observation is performed to observe the displacement of the target structure. As an example, as shown in FIG. 18, the displacement measurement of the proximity structure 70 is performed by an inclinometer 72 attached to the opposite side of the displacement measurement point 71 of the proximity structure 70, and the horizontal displacement and vertical displacement of the proximity structure 70 are measured. The inclination is measured, and it is confirmed that it is less than the allowable displacement amount (allowable value). Further, the displacement of the ground surface of the ground 8 is measured by placing the ground surface displacement pile 73 vertically and sufficiently with respect to the ground 8 so that the pile head is as horizontal as possible so as not to be affected by the unevenness of the ground surface. Install and perform as follows. In addition, the displacement measurement in the ground 8 is performed by installing the measurement tube 74 of the underground inclinometer so as to reach the support layer as the fixed point of the ground 8. It is done by combining.

  In this way, when the sand pile 9 is constructed in a narrow sand pile construction area, such as directly below or near the adjacent structure 70, the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53 is constant. By stopping the time, the displacement of the ground 8 around the adjacent structure 70 can be reliably reduced by using the pore water pressure dissipation time. Thereby, even when it is constructed directly under or in the vicinity of the adjacent structure 70, the displacement control for the adjacent structure 70 becomes easy, and the construction method according to the allowable displacement amount for each structure allows the displacement control. There is an advantage that does not require an auxiliary method.

  In addition, by determining the time to stop the discharge flow rate of fluidized sand 7 'for a certain time from the value obtained from the permeability coefficient from the particle size distribution of the ground to be improved, the dissipation time of pore water pressure can be used effectively, By applying to the step, the displacement of the adjacent structure 70 can be easily and reliably suppressed to the allowable value or less.

  Further, when displacement occurs in the adjacent structure 70 due to the discharge flow rate of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53, when the allowable displacement amount set in advance in the adjacent structure 70 is reached. Is detected, and the discharge flow rate of the fluidized sand 7 'discharged from the lower end opening of the hollow tube 53 is stopped for a certain period of time based on this detection output, so that the displacement of the adjacent structure 70 is allowed by the change of the pore water pressure. Although the ground improvement method to suppress the value to below the value has been described, when the adjacent structure 70 is displaced by the discharge pressure of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53, the lower end of the hollow tube 53 is The discharge pressure of the fluidized sand 7 ′ discharged from the opening may be returned to 0 (zero) for a predetermined time, and the discharge flow rate or the discharge pressure of the fluidized sand 7 ′ discharged from the lower end opening of the hollow tube 53. Causes displacement in the adjacent structure 70 Even if the discharge flow rate of the fluidized sand 7 'discharged from the lower end opening of the hollow tube 53 is stopped for a certain time or the discharge pressure of the fluidized sand 7' is returned to 0 for a certain time, the fluidized sand 7 'is dehydrated. Due to the change in pore water pressure due to the function, the displacement of the adjacent structure 70 can be suppressed to an allowable value or less.

1 Sand pile creation system 2 Fluidized sand supply piping (supply piping)
5 Pressure pump 7 Sand (sand pile material)
7 'Fluidized sand 8 Ground 9 Sand pile 10 Fluidized sand production plant 12 Twin screw paddle mixer (mixer)
DESCRIPTION OF SYMBOLS 15 Agitator tank 20 Fluidizer stirring tank 50 Construction machine main body 52 Lifting mechanism 53 Hollow pipe 60 Ground improvement management apparatus 61 Instrument panel 70 Adjacent structure R Fluidizer T Slow-acting plasticizer S Step width H Wave width

Claims (8)

A ground improvement management device that discharges fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from the lower end opening of a hollow tube that penetrates to a predetermined depth in the ground, and manages the creation of a predetermined length of sand pile. There,
After the hollow pipe has been penetrated to a predetermined depth in the ground via an elevating mechanism, a time point at which the discharge flow rate of the fluidized sand discharged from the lower end opening of the hollow pipe reaches a predetermined flow rate is detected. A ground improvement management device, wherein a signal for pulling out the step width corresponding to the predetermined flow rate is automatically transmitted to the lifting mechanism based on the detection output. A ground improvement management device that discharges fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from the lower end opening of a hollow tube that penetrates to a predetermined depth in the ground, and manages the creation of a predetermined length of sand pile. There,
After the hollow pipe has been penetrated to a predetermined depth in the ground via an elevating mechanism, a time point at which the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe reaches a predetermined pressure is detected. A ground improvement management device, wherein a signal for extracting a predetermined step width of the hollow tube is automatically transmitted to the lifting mechanism based on the detection output. A ground improvement management device that discharges fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from the lower end opening of a hollow tube that penetrates to a predetermined depth in the ground, and manages the creation of a predetermined length of sand pile. There,
After penetrating the hollow pipe to a predetermined depth in the ground via an elevating mechanism, the discharge flow rate or discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe is a predetermined flow rate or a predetermined flow rate. A ground improvement management device which detects a point in time when pressure is reached and automatically transmits a signal for extracting a predetermined step width of the hollow tube to the lifting mechanism based on the detection output. The ground improvement management device according to claim 1,
A ground improvement management apparatus, wherein a signal for moving the hollow tube up and down is automatically transmitted to the lifting mechanism until the discharge flow rate reaches a predetermined flow rate while pulling out the step width. A ground improvement method in which a sand pile is formed by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow pipe that penetrates to a predetermined depth in the ground. ,
After the hollow tube has been penetrated to a predetermined depth in the ground via the lifting mechanism, displacement occurs in the adjacent structure due to the discharge flow rate of the fluidized sand discharged from the lower end opening of the hollow tube. In this case, the time when the preset allowable displacement amount is reached in the adjacent structure is detected, and the discharge flow rate of the fluidized sand discharged from the lower end opening of the hollow tube is stopped for a certain time based on the detection output. The ground improvement construction method is characterized in that the displacement of the adjacent structure is suppressed to an allowable value or less by the change of the fluidized sand. A ground improvement method in which a sand pile is formed by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow pipe that penetrates to a predetermined depth in the ground. ,
After the hollow pipe penetrates to a predetermined depth in the ground through the lifting mechanism, displacement occurs in the adjacent structure due to the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe , The time point when the preset allowable displacement amount is reached in the adjacent structure is detected, and the discharge pressure of the fluidized sand discharged from the lower end opening of the hollow tube is returned to zero for a certain time based on this detection output. Then, the ground improvement construction method characterized by restraining the displacement of the adjacent structure to an allowable value or less by the change of the fluidized sand. A ground improvement method in which a sand pile is formed by discharging fluidized sand containing a fluidizing agent and a slow-acting plasticizing agent from a lower end opening of a hollow pipe that penetrates to a predetermined depth in the ground. ,
After penetrating the hollow pipe to a predetermined depth in the ground through an elevating mechanism, the hollow pipe is displaced to a neighboring structure by the discharge flow rate or discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe. Is detected, the time point when the preset allowable displacement amount is reached in the adjacent structure is detected, and the discharge flow rate of the fluidized sand discharged from the lower end opening of the hollow tube is determined for a certain time based on the detection output. Stopping or returning the discharge pressure of the fluidized sand to 0 for a certain time, thereby suppressing the displacement of the adjacent structure to an allowable value or less due to the change of the fluidized sand. It is the ground improvement construction method of any one of Claims 5-7,
The ground improvement characterized by determining the time to stop the discharge flow rate or discharge pressure of the fluidized sand discharged from the lower end opening of the hollow pipe for a certain time from the value obtained from the permeability coefficient from the particle size distribution of the improvement target ground Construction method.

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