JP7060399B2 - Ground improvement equipment, ground improvement system, and ground improvement method - Google Patents

Description

The present invention relates to a ground improvement device, a ground improvement system, and a ground improvement method.

Deep-sea resources such as methane hydrate, rare earth, and hydrothermal deposits exist in the deep sea near Japan. There are various methods for collecting deep-sea resources. For example, there is a method of excavating the seabed ground with an excavator installed on the seabed to collect resources in the ground.

However, there is also ultra-soft ground with a shear strength of about 2 to 10 kilopascals in the ground on the deep sea floor, which may not be suitable for the installation and running of excavators. When using an excavator on ultra-soft ground, it is necessary to ensure the transportability, bearing capacity, and stability of the excavator, and it is necessary to improve the ground on which the excavator is installed.

Examples of the technique for improving soft soil in water include the techniques described in Patent Documents 1 and 2. The technique described in Patent Document 1 is to solve the problem that when the solidifying material is added to the hydrous soft soil, the rotating stirring blade moves up and down the hydrous soft soil, so that the hydrous soft soil soars and pollutes the water. belongs to. In Patent Document 1, an inverted bottomed cylindrical shell is provided at the lower end of a frame body lowered from the hull, a stirring blade is arranged in the inverted bottomed tubular shell, and after landing, the stirring blade is made of water-containing soft soil. The method of intruding into is described.

Further, in Patent Document 2, in order to keep the inclination angle and position of the ground improvement machine suspended in water from a turret provided on the hull constant by a wire, the ground improvement machine is provided with a telescopic clamp device. A technique of restraining and controlling the stroke of the telescopic clamping device in response to changes in the tilt and position of the hull is described.

Japanese Unexamined Patent Publication No. 61-1718 Japanese Unexamined Patent Publication No. 60-233223

However, since the techniques of Patent Documents 1 and 2 all require a configuration in which the ground improvement device is pushed toward the submarine ground, it is difficult to apply it to the improvement of a deep submarine ground having a water depth of, for example, 300 meters or more.

One of the objects of the invention of the present application is to improve the bottom ground without the need for a configuration for pushing toward the bottom ground.

The ground improvement device according to claim 1 of the present invention is suspended in water and a measuring unit that measures a resistance value when the ground improvement device is dropped from a position higher than the upper surface of the bottom ground by a predetermined distance and penetrates into the bottom ground. , A spout for ejecting a ground improvement material supplied by a hose , and the bottom ground is cut by the ground improvement material ejected from the spout, and at least one of the spouts is centered on a predetermined axis. It is a ground improvement device that penetrates into the bottom ground by its own weight while rotating around the axis by the propulsive force received from the ground improvement material by ejecting the ground improvement material along the circumferential direction of the side surface.

The ground improvement device according to claim 2 of the present invention measures the resistance value when dropped from a position higher than the upper surface of the bottom ground by a predetermined distance and penetrates into the bottom ground in the embodiment according to claim 1. It is a ground improvement device equipped with a measuring unit.

The ground improvement system according to claim 2 of the present invention is a ground improvement system including the ground improvement device according to claim 1 and a positioning system for specifying the position of the ground improvement device.

The ground improvement method according to claim 3 of the present invention includes a step of suspending a ground improvement device provided with an outlet for ejecting a ground improvement material supplied by a hose into water and landing it on the upper surface of the bottom ground, and the upper surface thereof. The resistance value when the ground improvement device penetrates into the water bottom ground in the step of dropping the ground improvement device from a position higher by a predetermined distance from the ground and causing the ground improvement device to penetrate the water bottom ground and the step of penetrating the ground improvement device. The step of specifying the strength of the bottom ground based on the resistance value measured in the step of measuring, and the step of supplying the ground improvement material to the ground improvement device that has landed on the upper surface, and the above-mentioned The ground improvement device is provided on the bottom ground cut by the ejected ground improvement material in the step of ejecting the ground improvement material from the ejection port. This is a ground improvement method in which a material is pierced by its own weight while being rotationally moved around the axis by a propulsive force received from the ground improvement material ejected along the circumferential direction of a side surface centered on a predetermined axis.

The ground improvement method according to claim 4 of the present invention is the embodiment according to claim 3 , from the viewpoint of a reference surface when the ground improvement device has landed on the upper surface in the step of landing on the upper surface. It is a ground improvement method including a step of measuring the depth to the upper surface.

According to the invention according to the present application, the underwater ground can be improved without the need for a configuration for pushing toward the underwater ground.

The figure which shows the structure of the ground improvement apparatus 1. The figure which showed the operation which penetrates the ground improvement apparatus 1 into the underwater ground 4. The figure which shows the example of the ground improvement apparatus 1 provided with the measuring part 15. The figure which showed the operation of the ground improvement apparatus 1 in the modification 1. FIG. The figure which shows the structure of the ground improvement apparatus 1 which concerns on modification 4. The figure which shows the structure of the ground improvement system 9 in the modification 5. The figure for demonstrating the identification of the position by the ground improvement system 9.

<Embodiment>
<Structure of ground improvement equipment>
FIG. 1 is a diagram showing the configuration of the ground improvement device 1. The ground improvement device 1 shown in FIG. 1 is a cylindrical weight, and is used in a posture in which the axes are arranged along the direction of gravity. The ground improvement device 1 has a side spout 11 on the side surface 10 and a bottom spout 12 on the bottom surface 14. Both the side spout 11 and the bottom spout 12 are spouts for ejecting the ground improvement material to the outside.

The ground improvement device 1 may have any shape, but is preferably cylindrical or spherical in order to suppress the influence of water flow. In FIG. 1, both the side ejection port 11 and the bottom ejection port 12 project from the surface of the ground improvement device 1, but the shape is not limited to this, and it is sufficient that there is a hole for ejecting the ground improvement material.

<Operation of ground improvement device>
FIG. 2 is a diagram showing an operation of penetrating the ground improvement device 1 into the underwater ground 4. In FIG. 2, water and water surface are omitted.

As shown in FIG. 2A, the ground improvement device 1 has a wire 2 connected to its top surface 13, and is suspended from a ship (not shown) by the wire 2 in the water. Since the ground improvement device 1 has a higher specific gravity than the surrounding water or seawater, the wire 2 is wound down from the ship to descend underwater by its own weight.

As shown in FIG. 2B, when the ground improvement device 1 lands on the ground, the bottom surface 14 of the ground improvement device 1 comes into contact with the upper surface 40 of the bottom ground 4, and receives a normal force from the upper surface 40, so that the tension applied to the wire 2 is applied. Changes. The operator on the ship recognizes that the ground improvement device 1 has landed, for example, by observing this change in tension.

The hose 3 is a pipe for supplying the ground improvement material to the inside of the ground improvement device 1, and is connected to the top surface 13 of the ground improvement device 1. The ground improvement material supplied from the hose 3 is ejected to the outside from the side ejection port 11 or the bottom ejection port 12 through the internal flow path of the ground improvement device 1. That is, both the side ejection port 11 and the bottom ejection port 12 are ejection ports for ejecting the ground improvement material supplied by the hose 3.

When the operator recognizes that the ground improvement device 1 has landed, the operator supplies the ground improvement material from the ship to the ground improvement device 1 through the hose 3. As a result, the ground improvement material is ejected to the outside from the side ejection port 11 or the bottom ejection outlet 12, and the bottom ground 4 is cut by the ejected ground improvement material. Then, as shown in FIG. 2C, the ground improvement device 1 penetrates into the bottom ground 4 by its own weight while cutting the bottom ground 4. That is, the ground improvement device 1 is a ground improvement device that penetrates into the bottom ground 4 by its own weight while cutting the bottom ground 4 with the ground improvement material ejected from the side ejection port 11 or the bottom ejection port 12 (spout). The ejected ground improvement material becomes the improved ground 5 whose strength is improved by mixing with the underwater ground 4.

The above-mentioned operation of the ground improvement device 1 is to suspend the ground improvement device 1 provided with a spout (side spout 11 or bottom spout 12) for ejecting the ground improvement material supplied by the hose 3 into the water, and to lower the water bottom. Recognized as a ground improvement method including a step of landing on the upper surface 40 of the ground 4 and a step of supplying the ground improving material to the ground improving device 1 landing on the upper surface 40 and ejecting the ground improving material from the spout. obtain. In this ground improvement method, in the step of ejecting the ground improvement material, the ground improvement device 1 is penetrated into the underwater ground 4 cut by the ejected ground improvement material by its own weight.

Further, the above-mentioned operator who recognizes that the ground improvement device 1 has landed and supplies the ground improvement material to the ground improvement device 1 has a control unit, a storage unit, a detection unit for detecting the tension of the wire 2, and a wire. It may be an information processing device provided with a drive unit or the like for hoisting / unwinding of 2. In this case, the control unit included in the information processing device has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and the CPU is stored in the ROM and the storage unit. By reading and executing (hereinafter, simply referred to as a program), the above-mentioned detection unit, drive unit, and the like are controlled.

Further, when there is a concern that the ground improvement material diffuses into water, water, seawater, or the like is supplied to the ground improvement device 1 in front of the ground improvement material in order to cut the surface of the bottom ground 4. You may. For example, when the operator recognizes that the ground improvement device 1 has landed, the operator supplies water from the ship to the ground improvement device 1 through the hose 3. Then, when the operator recognizes that the surface of the bottom ground 4 has been cut to a predetermined depth (for example, 0.5 m to 1 m or more) based on the length of the wound wire 2, the operator recognizes that the ground has been cut. The fluid supplied to the improvement device 1 may be switched from water to a ground improvement material. This switching may be performed once, or may be performed by increasing the concentration of the ground improving material over a plurality of times. If the surface of the bottom ground 4 is cut by water, seawater, etc. and the ground improvement device 1 is buried in the bottom ground 4 beyond a certain depth, even if the ground improvement material is ejected from the spout, the surface improvement material can be ejected. There is no concern that the ground improvement material will flow out or diffuse into the water.

As described above, in the prior art, in order to push the device for improving the ground toward the underwater ground, a configuration such as an inverted bottomed cylindrical shell or a telescopic clamp device (referred to as a “pushing mechanism”) was required. .. As described above, the ground improvement device 1 according to the present invention penetrates the bottom ground 4 by its own weight while cutting the bottom ground 4 with the ground improvement material ejected from the spout, so that it is necessary to provide the above-mentioned pushing mechanism. not.

<Modification example>
The above is the description of the embodiment, but the content of this embodiment can be modified as follows. Further, the following modification examples may be combined.

<Modification 1>
In the above-described embodiment, when the operator recognizes that the ground improvement device 1 has landed, the ship supplies the ground improvement material from the ship to the ground improvement device 1 through the hose 3, but the ground improvement device 1 has landed. When recognizing that, for example, the wire 2 may be wound up and the ground improvement device 1 may be pulled up to a position higher than the upper surface 40 of the bottom ground 4 by a predetermined distance. In this case, the operator may drop the pulled up ground improvement device 1 to penetrate the submerged ground 4.

The ground improvement device 1 may be provided with a measuring unit 15 that measures the resistance value when the ground improvement device 1 penetrates the bottom ground 4 by falling from a position higher than the upper surface 40 by a predetermined distance h. FIG. 3 is a diagram showing an example of a ground improvement device 1 provided with a measuring unit 15. The measuring unit 15 is, for example, a load cell of a spring type, a piezoelectric element type, a magnetostrictive type, a capacitance type, a gyro type, a strain gauge type, etc. When a normal force is received from the upper surface 40 of the bottom ground 4, the resistance value due to the normal force is measured.

FIG. 4 is a diagram showing the operation of the ground improvement device 1 in the modified example 1. The operator on the ship recognizes that the ground improvement device 1 has landed as shown in FIG. 4A due to, for example, a change in tension applied to the wire 2. As shown in FIG. 4B, the operator winds up the wire 2 so that the ground improvement device 1 rises to a position higher than the upper surface 40 of the bottom ground 4 by a predetermined distance h. Then, the operator freely drops the ground improvement device 1 by winding down the wire 2.

As a result, the ground improvement device 1 penetrates into the bottom ground 4 under the condition that the ground improvement device 1 is dropped from a position higher than the upper surface 40 of the bottom ground 4 by a distance h. That is, this method can be recognized as a ground improvement method including a step of dropping the ground improvement device 1 from a position higher than the upper surface 40 by a predetermined distance h and allowing the ground improvement device 1 to penetrate into the underwater ground 4.

At this time, the measuring unit 15 measures the resistance value received from the bottom ground 4. Then, the measured resistance value is converted into, for example, an electric signal, transmitted from the measuring unit 15 to an information processing device installed on the water by a communication line extending toward the water, and used to specify the strength of the bottom ground 4. .. That is, in this method, in the step of penetrating the ground improvement device 1 into the bottom ground 4, the resistance measured in the step of measuring the resistance value when the ground improvement device 1 penetrates into the bottom ground 4 and the step of measuring the resistance value are measured. It can be recognized as a ground improvement method including a step of specifying the strength of the bottom ground 4 based on the value. The measuring unit 15 may store the measured resistance value in the storage device. In this case, the resistance value stored in the storage device may be read out by an information processing device or the like when the ground improvement device 1 is recovered on the water.

According to the ground improvement device 1 according to the modification 1, the resistance value when the ground improvement device 1 penetrates into the bottom ground 4 is measured when the ground improvement device 1 falls from a position higher than the upper surface 40 of the bottom ground 4 by a predetermined distance h. Therefore, the strength of the bottom ground 4 is specified. The user of the ground improvement device 1 may select, for example, the ground improvement material to be supplied to the bottom ground 4 or change the weight of the ground improvement device 1 based on the specified strength.

<Modification 2>
In the above-described embodiment or modification 1, the operator did not measure the position of the upper surface 40 in the gravity direction when he / she recognized that the ground improvement device 1 had landed, but he / she may measure this. ..

For example, as shown in FIG. 4A, when the operator recognizes that the ground improvement device 1 has landed, the water surface DL (an example of a reference surface) is based on the winding state of the wire 2. ) To the upper surface 40, the depth d0 may be measured. The reference surface is not limited to the water surface, and may be an average water surface, a maximum water surface, a minimum water surface, or the like. Further, the depth d0 may be estimated from the water pressure measured by using a water pressure gauge.

In this case, in this ground improvement method, when the ground improvement device 1 lands on the upper surface 40 in the step of landing the ground improvement device 1 on the upper surface 40, the depth from the reference surface to the upper surface 40 is measured. It can be recognized as a ground improvement method including a process.

According to the ground improvement device 1 according to the modification 2, the depth from the reference surface to the bottom ground 4 is measured.

<Modification 3>
In the above-mentioned modification 1, the ground improvement device 1 includes a measuring unit 15 for measuring the resistance value when the ground improving device 1 falls from a position higher than the upper surface 40 by a predetermined distance h and penetrates into the bottom ground 4. It may have a configuration for measuring the depth when penetrating into the ground 4.

For example, as shown in FIG. 4C, when the ground improvement device 1 is penetrated into the bottom ground 4, the operator penetrates from the upper surface 40 of the bottom ground 4 based on the winding state of the wire 2. The depth d to the bottom surface 14 of the ground improvement device 1 may be measured. In this case, the operator may specify the strength of the bottom ground 4 based on the measured depth d. The depth d may be estimated from the water pressure measured using a water pressure gauge.

In this case, this ground improvement method is measured in a step of measuring the depth of penetration of the ground improvement device 1 into the submerged ground 4 in a step of penetrating the ground improvement device 1 into the upper surface 40, and a step of measuring this depth. It can be recognized as a ground improvement method including a step of specifying the strength of the bottom ground 4 based on the depth.

According to the ground improvement device 1 according to the modification 3, for example, the strength of the bottom ground 4 is specified without measuring the resistance value when the ground improvement device 1 penetrates into the bottom ground 4.

<Modification example 4>
In the above-described embodiment, the ground improvement device 1 includes a side outlet 11 and a bottom outlet 12 for ejecting the ground improvement material supplied by the hose 3, but the side outlet 11 or the bottom ejection 12 is predetermined. It may be provided with a rotation mechanism for rotating and moving around the axis of the hose.

FIG. 5 is a diagram showing the configuration of the ground improvement device 1 according to the modified example 4. FIG. 5A shows a view of the ground improvement device 1 from the horizontal direction. Further, FIG. 5B shows a cross-sectional view in which the ground improvement device 1 is cut at a cross section F passing through the side ejection port 11 shown in FIG. 5A.

As shown in FIG. 5B, a central supply pipe 110 and a swirling flow path 111 opened from the central supply pipe 110 toward the side ejection port 11 are provided inside the ground improvement device 1. ..

The central supply pipe 110 is connected to, for example, a hose 3 by a rotary joint or the like, and is sent to the swirling flow path 111 through the ground improvement material supplied from the hose 3. As shown in FIG. 5B, the swirling flow path 111 is formed in a spiral shape centered on the axis of the cylindrical ground improvement device 1. Due to this shape, the ground improvement material sent to the swirling flow path 111 is located in the opposite circumferential direction from the side ejection holes 11 provided at two locations on the opposite sides of the axis, as shown in FIG. 5 (b). Since it is ejected along the above, the ground improvement device 1 rotates about the axis by the propulsive force received from the ejected ground improvement material. That is, the ground improvement device 1 shown in FIG. 5 is a ground improvement device provided with a rotation mechanism for rotating the side ejection port 11 and the bottom ejection port 12 around an axis along the gravity direction of the ground improvement device 1.

According to the ground improvement device 1 according to the modification 4, since the ground improvement device 1 is rotationally moved around the axis along the direction of gravity, the ground improvement material ejected from the side ejection port 11 is compared with the case where the rotation mechanism is not provided. It is easy to be uniformly ejected along the side surface 10 of the ground improvement device 1. Therefore, according to this ground improvement device 1, the underwater ground 4 is easily cut.

<Modification 5>
Although the configuration for specifying the position of the ground improvement device 1 is not mentioned in the above-described embodiment or modification, the position of the ground improvement device 1 may be specified by the positioning system. The "position" here may be, for example, a position on the ground surface specified by latitude and longitude, or a position in three-dimensional space specified by latitude, longitude, and depth. ..

FIG. 6 is a diagram showing the configuration of the ground improvement system 9 in the modified example 5. The ground improvement system 9 includes a ground improvement device 1, a wire 2, a hose 3, a sound wave transceiver 7, and an information processing device 8.

The sound wave transceiver 7 shown in FIG. 6 is installed on, for example, the upper surface 40 of the underwater ground 4. In the ground improvement system 9, the position and orientation in which the sound wave transceiver 7 is installed is used as a reference for latitude, longitude, depth, and orientation. The latitude and longitude of the position of the sonic transceiver 7 are specified, for example, by measuring the boring point at the time of installation by a Global Navigation Satellite System (GNSS) or the like. The posture of the sound wave transceiver 7 is specified, for example, by being adjusted at the time of installation. Further, the sound wave transceiver 7 may include, for example, a water pressure gauge for measuring water pressure. In this case, the depth of the position of the sound wave transceiver 7 is estimated from the water pressure measured by this water pressure gauge.

The sound wave transceiver 7 has a wave transmitting unit that transmits sound waves such as ultrasonic waves into water, and a plurality of receiving units that receive sound waves transmitted into water.

The plurality of receiving units have a so-called receiving array.

The ground improvement device 1 shown in FIG. 6 includes a sound wave transponder 16. When the sound wave transponder 16 receives a sound wave transmitted from the sound wave transceiver 7, the sound wave transponder 16 transmits a sound wave corresponding to the sound wave. The sound wave transmitted by the sound wave transponder 16 is received by a plurality of receiving units of the sound wave transceiver 7. By exchanging this, the sound wave transponder 16 is called by the sound wave transceiver 7.

As shown in FIG. 6, the sound wave transceiver 7 is connected to the other end of the communication line 20 whose one end is connected to the information processing apparatus 8. The sound wave transceiver 7 transmits a signal corresponding to the sound wave received from the sound wave transponder 16 to the information processing apparatus 8 by the communication line 20.

The information processing device 8 has a control unit, a storage unit, a connection unit, and the like. The control unit included in the information processing device 8 has a CPU, ROM, RAM, and the like, and the CPU controls the information processing device 8 by reading and executing a program stored in the ROM and the storage unit. The connection unit included in the information processing apparatus 8 is connected to the communication line 20 and receives the signal transmitted from the sound wave transceiver 7. The information processing apparatus 8 receives the distance from the sound wave transceiver 7 to the sound wave transponder 16 based on the time required for the sound wave to propagate between the sound wave transceiver 7 and the sound wave transponder 16 and the phase difference of the receiving portion. It has an arithmetic unit that calculates the angle of the wave and performs an operation to specify the position of the sound wave transponder 16, that is, the information of the position of the ground improvement device 1. This arithmetic unit may be realized by the control unit of the information processing apparatus 8 executing the arithmetic program, or may be realized by the arithmetic processor controlled by the control unit. Further, the information processing apparatus 8 may control the call of the sound wave transponder 16 by the sound wave transceiver 7 via the communication line 20.

Since the ground improvement system 9 according to the modification 5 has a positioning system including a sound wave transceiver 7, a sound wave transponder 16, a communication line 20, an information processing device 8, and the like, and the ground improvement device 1, the ground improvement device 1 The position of can be specified. FIG. 7 is a diagram for explaining the identification of the position by the ground improvement system 9.

The positioning system in the modified example 5 is not limited to the above-mentioned configuration. For example, the sound wave transceiver 7 may be installed in the water under the ship bottom or under the ship instead of the upper surface 40 of the water bottom ground 4. In this case, the sound wave transceiver 7 may be installed in water by suspending it with a wire or the like lowered from the ship into the water or by attaching it to the tip of a rod extending from the ship into the water.

Further, the sound wave transceiver 7 may be installed in the ground improvement device 1, and the sound wave transponder 16 may be installed on the wire, the rod, or the upper surface 40 of the bottom ground 4 dropped from the ship into the water.
Further, although the above-mentioned sound wave transceiver 7 has a plurality of receiving units, a plurality of sound wave transceivers 7 arranged at different positions may each have one receiving unit.

Further, the sound wave transceiver 7 and the sound wave transponder 16 may have a so-called acoustic modem, an acoustic converter, or the like. In this case, the sound wave transceiver 7 and the sound wave transponder 16 convert the information exchanged with each other by using an acoustic converter or the like into sound waves and transmit them into water, and when the sound waves are received, the above-mentioned information is extracted from the sound waves. do it. Further, the communication line 20 described above may be built in the wire 2 or the hose 3, or may be laid along the wire 2 or the hose 3.

Further, the positioning system in the modified example 5 is not limited to the configuration using sound waves. For example, one or more sensors may be arranged along the wire 2, and the information processing apparatus 8 may specify the position of the ground improvement apparatus 1 based on the information regarding the position detected by the sensor. For this sensor, for example, an angular velocity sensor such as an optical fiber gyro, an acceleration sensor such as a strain gauge type, a piezoelectric element type, or a capacitance type is used.

The ground improvement system 9 penetrates the ground improvement device 1 into the reform target region R of the submarine ground 4 a plurality of times, and each time, the position of the ground improvement device 1 is specified with reference to the sound wave transceiver 7. As a result, the information processing apparatus 8 of the ground improvement system 9 stores the distribution of the intrusion positions shown in FIG. 7, that is, the distribution of the positions of the improved ground 5 improved by the ground improvement material. By referring to this distribution, it is possible to grasp which part of the submarine ground 4 is being reformed in the reform target region R.

1 ... Ground improvement device, 10 ... Side surface, 11 ... Side spout, 110 ... Central supply pipe, 111 ... Swirling flow path, 12 ... Bottom spout, 13 ... Top surface, 14 ... Bottom surface, 15 ... Measuring unit, 16 ... Sonic transponder, 2 ... Wire, 20 ... Communication line, 3 ... Hose, 4 ... Underwater ground, 40 ... Top surface, 5 ... Improved ground, 7 ... Sonic transceiver, 8 ... Information processing device, 9 ... Ground improvement system.

Claims (4)

A measuring unit that measures the resistance value when the water is dropped from a position higher than the upper surface of the bottom ground by a predetermined distance and penetrates into the bottom ground.
It is provided with a spout that is suspended in water and ejects a ground improvement material supplied by a hose , and the bottom ground is cut by the ground improvement material ejected from the spout, and at least one of the spouts is specified. A ground improvement device that penetrates into the bottom ground by its own weight while rotating around the axis by the propulsive force received from the ground improvement material by ejecting the ground improvement material along the circumferential direction of the side surface centered on the axis of. .. The ground improvement device according to claim 1 and
A positioning system that identifies the position of the ground improvement device and
Ground improvement system equipped with. The process of suspending a ground improvement device equipped with a spout that ejects the ground improvement material supplied by a hose into the water and landing it on the upper surface of the bottom ground.
A step of dropping the ground improvement device from a position higher than the upper surface by a predetermined distance and allowing the ground improvement device to penetrate into the bottom ground.
In the step of penetrating, the step of measuring the resistance value when the ground improvement device penetrates into the bottom ground, and the step of measuring the resistance value.
A step of specifying the strength of the bottom ground based on the resistance value measured in the step of measuring, and a step of specifying the strength of the bottom ground.
A step of supplying the ground improvement material to the ground improvement device that has landed on the upper surface and ejecting the ground improvement material from the ejection port.
Equipped with
In the step of ejecting the ground improvement material, the ground improvement device is applied to the bottom ground cut by the ejected ground improvement material in the circumferential direction of the side surface of the ground improvement material centered on a predetermined axis. A ground improvement method in which a propulsive force received from a ground improvement material ejected along the axis causes the ground improvement material to penetrate by its own weight while rotating around the axis. A step of measuring the depth from the reference surface to the upper surface when the ground improvement device has landed on the upper surface in the step of landing on the upper surface.
The ground improvement method according to claim 3 .

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