JP7139277B2 - Compaction soil improvement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a compacted ground improvement method for forming a compaction improved zone in the ground to improve the ground to a firm foundation.

Conventionally, the compaction ground improvement method to improve the ground is to discharge sand into the ground and compress the discharged sand to create sand piles with expanded diameters in the ground and improve the ground to a strong one. A compaction sand pile construction method (sand compaction pile construction method) is known (see Patent Document 1).
The soil improvement equipment used for the compaction sand pile construction method is equipped with a self-propelled construction machine with an erected mast on the front, and a casing pipe that can penetrate the ground vertically along the erected mast. . The construction machine intrudes the casing pipe into the ground or pulls it out of the ground. The casing pipe is a cylindrical tube, inside of which the sand is fed. Further, a discharge port is provided at the bottom of the casing pipe, and sand is discharged into the ground through the discharge port.

In the compacted sand pile construction method, a construction machine penetrates the casing pipe to a predetermined depth, pulls out the casing pipe a little after penetration, and discharges the sand from the discharge port of the casing pipe after it has been pulled out. After the sand is discharged into the ground, the casing pipe is hammered back to compress the discharged sand. By repeatedly pulling out the casing pipe, discharging the sand from the casing pipe, and compressing the sand by hammering the casing pipe upward, a sand pile with an expanded diameter is formed in the ground and the ground is crushed. It can be improved to be stronger.

However, in the conventional compaction sand pile construction method, when constructing a sand pile in the ground, sand is newly discharged into the ground, and the discharged sand is compressed by driving back the casing pipe and spreads in the ground. In order to form a sand pile with a diameter, lateral displacement occurs in the ground in a horizontal direction. Therefore, if there are existing structures such as houses and buildings near the work site, lateral displacement of the ground may adversely affect the existing structures such as damage. There is a problem that construction by the hardened sand pile construction method cannot be performed. In addition, by discharging sand into the ground and creating a sand pile with an expanded diameter, the volume of the ground increases and the ground surface rises above it. There is also the problem that the work cost for ground improvement increases due to the work cost for removal.

JP-A-8-284146

The present invention has been made in view of such problems, and its purpose is to reduce the lateral displacement that occurs in the ground when improving the ground, and to prevent existing structures from being affected by lateral displacement. To reduce construction costs by preventing adverse effects, preventing swelling of the ground surface, and eliminating work for removing the swelling.

The present invention is a compaction ground improvement method for forming a compaction improvement zone in the ground to improve the ground to a firm ground, and is a compaction device that attaches spiral screw blades to the outer periphery and compacts earth and sand at the bottom. A casing pipe penetrating step that excavates the ground while rotating forward and penetrates to a predetermined depth in the ground, and a casing pipe that has penetrated to a predetermined depth and a predetermined length After the casing pipe is pulled out, the casing pipe is reversely rotated, and the cavity created by pulling out the casing pipe with the screw blades is filled with the earth and sand excavated in the casing pipe penetration step. and an earth and sand compaction process for compacting the filled earth and sand with a compaction device. After the casing pipe penetration process, the casing pipe drawing process, the earth and sand filling process, and the earth and sand compaction process are sequentially repeated upward. It is a compaction soil improvement method that forms a compaction improvement zone in the ground.

According to the present invention, the cavity formed by pulling out the casing pipe is filled with earth and sand excavated at the time of penetration, and the filled earth and sand is compacted from above by a compaction device to form a compaction improvement zone in the ground. As a result, the impact on the surrounding ground is small, and the lateral displacement that occurs in the ground can be greatly reduced. As a result, it is possible to prevent adverse effects such as damage to existing structures due to lateral displacement of the ground, and it is possible to improve the ground even in urban areas where houses are densely packed.
In addition, when forming a compaction improvement area in the ground to improve the ground, since the soil excavated when the casing pipe is penetrated is compacted to form the compaction improvement area, new soil is added to the ground. Since there is no input, no volume increase occurs in the ground. As a result, it is possible to prevent the ground surface from rising and eliminate the need for work to remove the swelling, thereby significantly reducing construction costs. In addition, when improving the ground at a waste disposal site, the ground surface of the site where the ground improvement has been performed can be subsided. It is also possible to reduce the volume of waste in

It is a side view of a ground improvement device. FIG. 4 is a side view of the lower portion of the casing pipe; It is a bottom view of a casing pipe. FIG. 4A is an enlarged cross-sectional view showing the compaction device attached to the lower portion of the casing pipe, and FIG. 4B is an enlarged cross-sectional view showing the state when the compaction device operates. It is a top view explaining forward rotation of a casing pipe. 6A is a diagram showing a state in which the casing pipe is set in the casing pipe penetration process, FIG. 6B is a diagram showing a state of the casing pipe penetration in the casing pipe penetration process, and FIG. 6C is a diagram showing the casing pipe extraction process in the casing pipe extraction process. FIG. 10 is a diagram showing a state in which the FIG. 7A is a diagram showing a state in which the earth and sand are filled in the earth and sand filling process, FIG. 7B is a diagram showing the state in which the earth and sand are filled in the earth and sand filling process, and FIG. 7C shows the earth and sand in the earth and sand compaction process. It is a figure which shows a state. 8A is a diagram showing a state in which the casing pipe is pulled out in the casing pipe pulling process, FIG. 8B is a diagram showing a state in which the earth and sand are filled in the earth and sand filling process, and FIG. 8C is a diagram showing the earth and sand in the earth and sand filling process. It is a figure which shows a state. FIG. 9A is a diagram showing a state in which earth and sand are compacted in the earth and sand compaction process, and FIG. 9B is a diagram showing a state in which a compaction improvement zone is formed in the ground.

One embodiment of the compaction ground improvement method of the present invention will be described with reference to the drawings.
The compaction ground improvement method according to the present embodiment (hereinafter simply referred to as the main compaction ground improvement method) is a ground improvement device equipped with a casing pipe having a spiral screw blade attached to the outer periphery and a compaction device attached to the bottom. is used to form a compaction improvement zone in the ground, improving the ground to a strong one.

FIG. 1 is a side view of a soil improvement device. FIG. 2 is a side view of the lower portion of the casing pipe. FIG. 3 is a bottom view of the casing pipe. 4A is an enlarged cross-sectional view showing the compaction device attached to the lower portion of the casing pipe, and FIG. 4B is an enlarged cross-sectional view showing the state when the compaction device is activated.
(Soil improvement device)
As shown in FIG. 1, the ground improvement equipment used in the compaction ground improvement method is equipped with a self-propelled construction machine 1, a mast 2 is erected in front of the construction machine 1, and along the erected mast 2 It has a rotatable casing pipe 3 that extends upward and downward. The casing pipe 3 becomes penetrable into the ground. A rotating device 4 and a lifting device 5 are attached to the upper part of the mast 2 of the construction machine 1 for penetrating the casing pipe 3 into the ground or pulling it out from the ground.

The casing pipe 3, as shown in FIGS. 2 and 3, is a cylindrical pipe and has a plurality of drilling bits 6 attached to its lower end for drilling the ground. A spiral screw blade 7 is attached to the outer circumference of the casing pipe 3 . The spiral direction of the screw blades 7 is upward to the right (indicated by arrow Y in FIG. 2). It is common for the screw blades 7 to have a spiral direction upward to the right.

The screw vanes 7 are attached to substantially the lower half of the casing pipe 3 . For example, when the total length of the casing pipe 3 is 10 m, the screw blades 7 are attached to the lower 5 m portion (see FIG. 1). In addition, the attachment of the screw blades 7 is not limited to this, and may be attached to the entire length of the casing pipe 3, for example. Moreover, the spiral screw blade 7 is attached so as to be continuous with the outer circumference of the casing pipe 3 . As described above, the screw blades 7 are continuous, but not limited to this, and may be partially interrupted.

The casing pipe 3 has a compacting device 8 attached to its lower part. As shown in FIG. 4A , the compaction device 8 has a power generation unit 11 and a tip compaction unit 12 . Compaction is performed by impacting the earth and sand below 3 from above. Striking is to strike by applying an impact (a large momentary force). The compaction device 8 here is a device that uses electricity for power.
Note that the compaction device 8 is not limited to a device that uses electricity, and may be another device that uses hydraulic power as power. Further, the compaction of earth and sand by the compaction device 8 is not limited to impact, and may be compaction by pressing or impact.

The power generator 11 is, for example, a solenoid. The power generation unit 11 has a controller 13 , a drive unit 14 and a plunger 15 , and the controller 13 controls driving of the drive unit 14 so that the drive unit 14 moves the plunger 15 . The controller 13 , drive unit 14 and plunger 15 are arranged inside the casing pipe 3 .
The front end compaction part 12 has a cylindrical slide cover 16 and a compaction plate 17 , and the slide cover 16 and the compaction plate 17 can protrude downward from the lower end of the casing pipe 3 . The slide cover 16 is cylindrical, moves up and down along the inner circumference of the casing pipe 3, and has a compaction plate 17 fixed to its lower portion. The compaction plate 17 has the same circular outer periphery as that of the casing pipe 3, and has a conical lower surface that impacts earth and sand.

In this compaction device 8, as shown in FIG. 4B, the plunger 15 of the power generator 11 causes the slide cover 16 and compaction plate 17 of the tip compaction unit 12 to protrude downward from the lower end of the casing pipe 3. Thus, the compaction plate 17 impacts the earth and sand from above. Thereby, the earth and sand under the casing pipe 3 can be compacted.

Next, the main compaction ground improvement method will be explained.
(Main compaction ground improvement method)
This compaction ground improvement method includes a casing pipe penetration step of penetrating the casing pipe 3 to a predetermined depth in the ground, a casing pipe drawing step of drawing out the casing pipe 3 to a predetermined length, and a casing pipe 3 drawn out. An earth and sand filling process for filling the cavity C with earth and sand, and an earth and sand compaction process for compacting the filled earth and sand. After the casing pipe penetration process, the casing pipe drawing process, the earth and sand filling process, and the earth and sand compaction process are arranged upward. A compaction improvement zone K is formed in the ground by repeating successively. Thus, by forming the compaction improvement zone K in the ground, the ground can be improved to be strong.

FIG. 5 is a plan view for explaining forward rotation of the casing pipe. 6A is a diagram showing a state in which the casing pipe 3 is set in the casing pipe penetration process, FIG. 6B is a diagram showing a state in which the casing pipe 3 is inserted in the casing pipe penetration process, and FIG. 6C is a diagram showing the casing pipe in the casing pipe drawing process. It is a figure which shows the state which pulled out 3. FIG. 7A and 7B are diagrams showing a state in which the earth and sand are filled in the earth and sand filling process, and FIG. 7C is a diagram showing a state in which the earth and sand are compacted in the earth and sand compaction process. 8A is a diagram showing a state in which the casing pipe 3 is pulled out in the step of pulling out the casing pipe, FIG. 8B is a diagram showing a state in which the earth and sand are filled in the earth and sand filling process, and FIG. 8C is a diagram showing the earth and sand filling in the earth and sand filling process. It is a figure which shows the state which carried out. FIG. 9A is a diagram showing a state in which earth and sand are compacted in the earth and sand compaction process, and FIG. 9B is a diagram showing a state in which a compaction improvement zone K is formed in the ground.

(Casing pipe penetration process)
In the casing pipe penetration step, first, as shown in FIG. 6A, the casing pipe 3 with the screw blades 7 attached to the outer periphery is set at a predetermined position (the position where the compaction improvement area K is formed), and then, as shown in FIG. 6B As shown in , the casing pipe 3 set at a predetermined position is penetrated to a predetermined depth, for example, 8 to 10 m, in the ground while rotating forward by a construction machine (not shown). Forward rotation is indicated by an arrow R1 in the figure. However, the predetermined depth is not limited to this. Excavation of the ground during penetration is performed by a plurality of excavation bits 6 attached to the lower end of the casing pipe 3 .
Here, the forward rotation of the casing pipe 3 means rotation in the direction of screwing the screw blades 7 whose helical direction is upward to the right into the ground, that is, as shown in FIG. Clockwise (right) rotation.

(Casing pipe drawing process)
In the casing pipe drawing process, after the casing pipe 3 is penetrated to a predetermined depth, that is, after the casing pipe penetration process, as shown in FIG. 6C, the casing pipe 3 is drawn out by a predetermined length while rotating in the reverse direction. The predetermined length of withdrawal is, for example, 50 cm. However, the predetermined length to be pulled out varies depending on the soil quality. Therefore, it is not limited to 50 cm. The reverse rotation of the casing pipe 3 is the reverse rotation of the forward rotation, indicated by an arrow R2 in the drawing, and is counterclockwise (counterclockwise) rotation when the casing pipe 3 is viewed from above.
By pulling out the casing pipe 3 by a predetermined length in this manner, a cavity C is formed in the trace of the pulling out of the casing pipe 3 (below the casing pipe 3).

(Earth and sand filling process)
After the casing pipe 3 is pulled out, that is, after the casing pipe is pulled out, the earth and sand filling process fills the cavity C formed by the casing pipe 3 with the screw blades 7 on the outer periphery of the casing pipe 3 with earth and sand. That is, as shown in FIG. 7A, the casing pipe 3 is rotated in the reverse direction without moving up and down. The earth filling time T (the time for reversely rotating the casing pipe 3) is calculated based on the amount of earth and sand movement by the screw blades, and uses a later-described earth and sand movement time calculation formula. The filling time T of this earth and sand is, for example, about 1 minute.
In this way, by rotating the casing pipe 3 in the opposite direction without moving up and down, the earth and sand excavated when the casing pipe 3 penetrates is moved downward by the screw blades 7, and the cavity C formed by pulling out the casing pipe 3. Put sand inside. That is, the earth and sand are filled by the screw blades 7 while the casing pipe 3 is not moved up and down. Thereby, as shown in FIG. 7B, the inside of the cavity C is filled with earth and sand.

In addition, when filling the cavity C with the earth and sand by the screw blades 7 on the outer periphery of the casing pipe 3, the casing pipe 3 is kept in a state of not moving up and down, but the casing pipe 3 is not limited to this, and the casing pipe 3 is moved up and down slightly. can be The vertical movement at this time is, for example, a repetition of upward movement and downward movement.

(Earth and sand compaction process)
In the earth and sand compaction process, the earth and sand are compacted by the compaction device 8 after the cavity C formed by pulling out the casing pipe 3 is filled with earth and sand, that is, after the earth and sand filling process. That is, in the compaction device 8 attached to the lower part of the casing pipe 3, the compaction plate 17 of the tip compaction part 12 protrudes downward, and as shown in FIG. The earth and sand filled in C are impacted from above to compact the earth and sand. The compaction of earth and sand is not limited to compaction by impact, and may be compaction by pressing or impact.
By compacting the earth and sand filled in the cavity C with the compaction device 8 in this manner, a part of the compaction improved zone K can be formed in the ground.

In the earth and sand compaction process, when the earth and sand are compacted from above by the compaction device 8, the casing pipe 3 receives a recoil from the compaction device 8 and tries to be lifted. The screw blades 7 attached to the outer circumference of the casing bite into the ground, thereby suppressing the upward movement of the casing pipe 3. As a result, for the construction machine 1 that attaches and supports the casing pipe 3, a small construction machine can be used instead of a large construction machine, and the work cost can be reduced.

Thereafter, again, as shown in FIG. 8A, the casing pipe 3 is drawn out in the same casing pipe drawing step as described above. The predetermined length of drawing at this time is also 50 cm. However, the upper end of the compacted earth and sand is used as a reference, and 50 cm is pulled out from this point.
Next, as described above, as shown in FIG. 8B, the cavity C is filled with earth and sand in the earth and sand filling step. The cavity C is filled with earth and sand, and the inside of the cavity C is filled with earth and sand as shown in FIG. 8C. Subsequently, as shown in FIG. 9A, compaction of the filled earth and sand in the earth and sand compaction process is performed. Repeat this upwards.

As described above, after the casing pipe penetration process, the casing pipe extraction process, the earth filling process, and the earth and sand compaction process are successively repeated upward to a predetermined depth near the ground surface as shown in FIG. 9B. As a result, the improved compaction zone K can be formed in the ground, and by forming the improved compaction zone K in the ground, the ground can be improved to be strong.

In addition, in this compaction ground improvement method, when the compaction improvement zone K is formed in the ground to improve the ground, the excavated soil is compacted without adding new soil into the ground. A decrease in volume can occur at , causing the ground surface above it to subside. As a result, for example, when improving the ground at a waste disposal site such as a garbage disposal site, the ground surface of the place where the ground improvement is performed can be subsided, and waste ( garbage) can be buried. In other words, it is possible to reduce the volume (increase the density) of the waste at the waste disposal site and process more waste.
In other words, this compacted ground improvement method can be used favorably for life extension measures of waste treatment plants.

Next, the calculation formula of the earth and sand moving time used in the earth and sand filling process will be explained.
The calculation formula for the earth and sand movement time is based on the amount of earth and sand movement by the screw blades 7. In this earth and sand movement time calculation formula, the time required to reversely rotate the casing pipe 3 and fill the earth and sand, that is, the earth and sand filling time. Calculate the time T.

The formula for the sediment movement time is as follows. A movement amount V2 of earth and sand per rotation by the screw blade 7 is calculated (first formula). Along with this, the volume Va of the cavity C formed by pulling out the casing pipe 3 is calculated (second equation). The rotational speed N of the screw blades 7 for filling the cavity C is calculated from the movement amount V2 of the earth and sand calculated by the first formula and the volume Va of the cavity C calculated by the second formula (third formula). A filling time T of earth and sand is calculated from the rotation speed N for filling the cavity C calculated by the third formula (fourth formula).

That is, the first formula for calculating the movement amount V2 (m ³ /time) of earth and sand per rotation by the screw blade 7 is V2=e×S×(P−v/f), where e is the transfer efficiency (the ratio of the potential energy for moving earth and sand in the vertical direction to the energy for rotating the casing pipe 3 once), which can be set to 0.3 based on past data. In addition, S is the screw blade cross-sectional area (m ² ), P is the screw blade pitch (m), v is the casing pipe penetration speed (m/min), and f is the casing pipe rotation speed (times/min). be.

The second formula for calculating the volume Va (m ³ ) of the cavity C formed by pulling out the casing pipe 3 is Va=A×U, where A is the casing pipe cross-sectional area (m ² ), U is the drawing length (m) of the casing pipe 3.
A third formula for calculating the number of revolutions N (turns) of the screw blades 7 for filling the cavity C is N=Va/V2.
A fourth formula for calculating the earth filling time T (minutes) is T=N/f.
Thereby, the filling time T of the earth and sand in the earth and sand filling process can be calculated.

Next, a specific example of calculating the earth and sand filling time T using the earth and sand moving time calculation formula will be described.
Assuming that the outer diameter D of the casing pipe 3 is 0.4 m, the outer diameter W of the screw blades 7 is 0.5 m, and the screw blade pitch P is 0.5 m (see FIG. 2), the casing pipe cross-sectional area A is 0.126 m ² , and the screw blade cross-sectional area S is 0.071 m ² . Also, the casing pipe penetration speed v is 0.5 m/min, the casing pipe rotation speed f is 6 times/min, the movement efficiency e is 0.3, and the withdrawal length U of the casing pipe 3 is 0.5 m. .

According to the first formula, the movement amount V2 of earth and sand per rotation by the screw blade 7 is 0.3×0.071×(0.5−0.5/6)=0.00888 m ³ /turn.
According to the second formula, the volume Va of the cavity C formed by pulling out the casing pipe 3 is 0.126×0.5=0.063 m ³ .
According to the third formula, the number of revolutions N of the screw blades 7 for filling the cavity C is 0.063/0.00888=7.1 times.
According to the fourth equation, the sand filling time T is 7.1/6=1.18 minutes. That is, the earth and sand filling time T in the earth and sand filling step is 1 minute and 11 seconds.

As described above, in the earth and sand filling process, the earth and sand filling time T is calculated by a formula for the earth and sand movement time based on the amount of earth and sand movement by the screw blade 7, and the earth and sand are filled according to the calculated time. The earth and sand can be filled rationally, that is, in the minimum necessary time, and the working time (time for filling the earth and sand) can be shortened.

As described above, according to this compaction ground improvement method, the cavity C formed by pulling out the casing pipe 3 is filled with the earth and sand excavated at the time of penetration, and the filled earth and sand is compacted from above by the compaction device 8. , By forming the improved compaction zone K in the ground, unlike the conventional compacted sand pile construction method in which sand is newly discharged into the ground to create a sand pile with an expanded diameter, The impact on the surrounding ground is small, and the lateral displacement that occurs in the ground can be greatly reduced. As a result, it is possible to prevent adverse effects such as damage to existing structures due to lateral displacement of the ground, and it is possible to improve the ground even in urban areas where houses are densely packed.

In addition, when the ground is improved by forming the compaction improvement area K in the ground, the soil excavated when the casing pipe 3 is penetrated is compacted to form the compaction improvement area K, so new soil is added. Since there is no injection into the ground, there is no increase in volume in the ground. As a result, it is possible to prevent the ground surface from rising and eliminate the need for work to remove the swelling, thereby significantly reducing construction costs.

DESCRIPTION OF SYMBOLS 1... Construction machine, 2... Mast, 3... Casing pipe, 4... Rotating device, 5... Elevating device, 6... Excavating bit, 7... Screw blade, 8... Compacting device, 11... Power generation part, 12... Tip tightening Hardening part 13... Controller 14... Driving part 15... Plunger 16... Slide cover 17... Compaction plate.

Claims (4)

A compaction ground improvement method for forming a compaction improvement zone in the ground to improve it to a strong ground,
Spiral screw blades are attached to the outer circumference, and a casing pipe that can penetrate up and down into the ground with a compaction device attached to the bottom to compact the soil is rotated forward to excavate the ground to a predetermined depth in the ground. A casing pipe penetration step that penetrates to
A casing pipe drawing step of drawing out a predetermined length of the casing pipe that has penetrated to a predetermined depth;
a sand filling step of, after pulling out the casing pipe, rotating the casing pipe in reverse and filling the cavity formed by pulling out the casing pipe with the screw blades with the sand excavated in the casing pipe penetrating step ;
an earth and sand compaction step of compacting the filled earth and sand with a compaction device;
A compaction ground improvement method, characterized in that, after a casing pipe penetration process, a casing pipe extraction process, a sand filling process, and a sand compaction process are sequentially repeated upward to form a compaction improvement zone in the ground.
In the method for improving compacted ground according to claim 1,
A compaction ground improvement method in which earth and sand are filled with screw blades while the casing pipe does not move up and down in the earth and sand filling process. In the compacted ground improvement method according to claim 1 or 2,
A compaction ground improvement method in which, in the earth and sand filling process, the earth and sand are filled during the earth and sand filling time calculated based on the amount of movement of the earth and sand by the screw blades. In the method for improving compacted ground according to any one of claims 1 to 3,
In the earth and sand compaction process, using a compaction device that has a power generation unit attached to the lower part of the casing pipe and a tip compaction part that is moved by the power generation part, the tip compaction part of the compaction device removes earth and sand from above. A compaction ground improvement method for compaction by striking or pressing or striking.

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