JP2019007133A - Ground improvement method - Google Patents

Abstract

When improving the ground in the vicinity of a target existing object, the target existing object is prevented from being adversely affected by lateral displacement, and the construction cost is prevented from rising and the work period is shortened. Drainage that drills holes in the ground near the target existing object K to a predetermined depth with a drilling rod, puts gravel material G such as crushed stone and gravel into the holes, and discharges pore water in the ground The drainage rod 22 penetrates to the ground near the target existing object K where the drainage channel D is installed in the drainage channel installation process in which a plurality of channels D are installed, and flows from the discharge rod 22 after the penetration. A sand pile forming step of discharging a plurality of sand piles T to discharge the chemical sand, expand the discharged fluidized sand, and compact the surrounding ground, and when the sand pile T is formed, The interstitial water w is discharged to the ground by the drainage channel D to suppress the increase of the pore water pressure in the ground. [Selection] Figure 7

Description

The present invention relates to a ground improvement method for forming a sand pile in the ground in the vicinity of a target existing object and compacting the surrounding ground.
Here, the target existing object is an existing structure such as a building such as a house, a building or a warehouse, a structure such as a road, a railway or a bridge, or a land such as a farmland or a residential land such as a rice field, a field or a ranch.

As an example of a ground improvement method for forming a sand pile in the ground and compacting the surrounding ground, a sand press-fit type static compaction method is known.
The sand press-fit type static compaction method consists of an upward and downward discharge rod that discharges sand material (here, fluidized sand) by applying pressure into the ground from the bottom, and penetration and extraction of the discharge rod into the ground. The construction machine has a construction machine, and the construction machine penetrates the discharge rod to a predetermined depth. After the penetration, the fluidized sand is discharged into the ground from the lower end of the delivery rod. By discharging the fluidized sand into the ground until a predetermined amount is reached, the fluidized sand expands in diameter, and a part of the sand pile that compacts the surrounding ground is formed. By repeating this while pulling out the discharge rod little by little from the predetermined depth with a construction machine, a sand pile is created in the ground and the surrounding ground is compacted (see Patent Document 1).

  By the way, the ground improvement methods such as the sand press-fit type static compaction method create a sand pile that expands the fluidized sand discharged into the ground and compacts the surrounding ground, but when creating a sand pile ( When the ground is improved), the pore water pressure of the ground rises due to the diameter expansion of the fluidized sand in the ground, and accordingly, a lateral displacement occurs in which the ground is displaced horizontally in the shallow part of the ground.

In this ground improvement method, when the ground in the vicinity of the target existing object is improved, the lateral displacement generated in the shallow part of the ground may adversely affect the target existing object. For this reason, conventionally, a displacement buffer wall using a displacement buffer groove or a steel sheet pile is installed in the ground in order to prevent adverse effects on the existing object.
10A is a plan view showing an installation state of a conventional displacement buffering groove, and FIG. 10B is a plan view showing an installation state of a conventional displacement buffering wall.
As shown in the drawing, the displacement buffer groove M or the displacement buffer wall W reaches a predetermined depth in the ground between the area where the sand pile T is formed in the ground and the ground is improved and the existing object K (boundary). And continuously along the target existing object K. Thereby, the lateral displacement generated at the time of ground improvement is absorbed or blocked by the displacement buffer groove M or the displacement buffer wall W, and the target existing object K can be prevented from being adversely affected by the lateral displacement.

However, when the displacement buffering groove M is installed, the displacement buffering groove M may be collapsed due to lateral displacement. When the displacement occurs, it is necessary to dig up the displacement buffering groove M again and install it again. In addition, after the ground improvement work is completed, the work for refilling the installed displacement buffering groove M must be performed, which requires a lot of labor and time. Therefore, there is a problem that the construction cost increases and the construction period becomes longer.
Further, even when the displacement buffer wall W is installed, after the ground improvement work is completed, the work to remove the installed displacement buffer wall W from the ground must be performed. Takes a lot of labor and time. Therefore, there is a problem that the construction cost increases and the construction period becomes longer.

JP 2010-13885 A

  The present invention has been made in view of such problems, and its purpose is to prevent adverse effects due to lateral displacement on the target existing object when improving the ground in the vicinity of the target existing object. It is to prevent the construction cost from rising and shorten the construction period.

  The present invention provides a drainage channel in which a plurality of drainage channels are formed in a ground near a target existing object by drilling a hole to a predetermined depth with a drilling rod, putting drainage material into the hole, and discharging pore water in the ground The discharge rod penetrates to the ground near the target existing object where the drainage channel was installed in the installation process and the drainage channel installation process, and after the penetration, the sand material is discharged from the discharge rod, and the discharged sand material is expanded in diameter. And a sand pile creation step of creating a plurality of sand piles for compacting the surrounding ground.

According to the present invention, when sand piles are created in the sand pile creation process, pore water in the ground is discharged to the ground by the drainage channel installed in the drainage channel installation process, thereby suppressing an increase in pore water pressure in the ground. The lateral displacement generated in the shallow part of the ground can be greatly reduced, and the adverse effect of the lateral displacement on the existing object can be prevented.
In addition, even after the ground improvement work is completed, it is possible to leave the drainage channel installed in the ground without removing it, and the work is simplified by eliminating the drainage channel removal work. The labor and time required for this can be greatly reduced, so that the construction cost can be prevented from rising and the construction period can be shortened.

It is explanatory drawing of the drainage channel installation apparatus used in the ground improvement method of this invention. It is explanatory drawing of the sand pile production apparatus used in the ground improvement method of this invention. It is explanatory drawing which shows a drainage channel installation process. It is a top view which shows the work state in a drainage channel installation process. It is explanatory drawing which shows a sand pile creation process. It is a top view which shows the working state in a sand pile creation process. It is explanatory drawing which shows the effect | action of a drainage channel. It is explanatory drawing which shows the range which installs a drainage channel. It is explanatory drawing which shows another example of the drainage channel installed at a drainage channel installation process. It is a top view which shows the installation state of the conventional displacement buffer groove or a displacement buffer wall.

An embodiment of the ground improvement method of the present invention will be described with reference to the drawings.
The ground improvement method according to the present embodiment (hereinafter simply referred to as the present ground improvement method) is a method of forming a sand pile in the ground in the vicinity of the target existing object and compacting the surrounding ground. Here, the target existing object will be described as an existing structure such as a building or a structure.
This ground improvement method is roughly the target of installing the drainage channel in the ground near the target existing object and installing the drainage channel in the drainage channel installation process to install multiple drainage channels to discharge pore water in the ground. And a sand pile creation process for creating a plurality of sand piles for compacting the surrounding ground on the ground in the vicinity of the existing product.

  In this soil improvement method, the sand pile creation process will be explained by taking an example of ground improvement by the sand press-fit type static compaction method, but this sand pile creation process is not limited to this. It may be ground improvement by other methods such as a compaction pile method.

A device for ground improvement by the ground improvement method includes a drainage channel installation device used in a drainage channel installation step and a sand pile creation device used in a sand pile creation step.
FIG. 1 is an explanatory view of a drainage channel installation device used in the present ground improvement method, and FIG. 2 is an explanatory view of a sand pile forming device used in the present ground improvement method.

  As shown in FIG. 1, the drainage installation apparatus 1 includes a construction machine 10 that can run on its own, and the construction machine 10 erects a mast 11 at a front portion thereof and moves up and down along the mast 11. A drilling rod 12 is provided. The drilling rod 12 is a hollow tube, and has a discharge port 13 at its lower end and a drilling unit 14 to penetrate into the ground and make a hole. Further, a rotating unit 15 that rotates the drilling rod 12 and an elevating unit 16 that penetrates and pulls the drilling rod 12 into the ground are provided on the upper part of the drilling rod 12.

As shown in FIG. 2, the sand pile building device 2 has a construction machine 20 that can be self-propelled. The construction machine 20 erects a mast 21 at a front portion thereof, and moves up and down along the mast 21. It has a discharge rod 22. The discharge rod 22 is a hollow tube, and a sand material (here, fluidized sand) or compressed air passes through the tube, and a discharge port 23 for discharging the fluidized sand into the ground is provided at the lower end. Moreover, the rotation part 24 which rotates a discharge rod, and the raising / lowering part 25 which penetrates and withdraw | extracts the discharge rod 22 in the ground are provided in the upper part of the discharge rod 22, respectively.
Here, the fluidized sand is a sand material obtained by mixing a fluidizing agent with sand and fluidizing it.
Further, the sand material is not limited to fluidized sand. For example, when performing ground improvement by the sand compaction pile method in the sand pile formation process, the sand material is sand, crushed stone, slag, or a mixture thereof. is there.

  The sand pile building device 2 has a peripheral facility 26 that supplies fluidized sand to the discharge rod 22 of the construction machine 20. The peripheral equipment 26 includes a fluidized sand generating device 27 that mixes a fluidizing agent with sand to generate fluidized sand. The fluidized sand is sent from the fluidized sand generating device 27 by a pressure feed pump 28, and a pressure gauge The fluidized sand is supplied to the discharge rod 22 via 29.

  The construction machine 10 of the drainage channel installation device 1 and the construction machine 20 of the sand pile creation device 2 may be the same construction machine. In this case, the drilling rod 12 is attached to the construction machine in the drainage channel installation process, and the discharge rod 22 is attached to the construction machine in the sand pile creation process. That is, by replacing the drilling rod 12 and the discharge rod 22 in the construction machine, the same construction machine can be used in the drainage channel installation process and the sand pile creation process.

Next, the ground improvement method will be specifically described.
3 is an explanatory diagram showing the drainage channel installation process, FIG. 4 is a plan view showing the working state in the drainage channel installation process, FIG. 5 is an explanatory diagram showing the sand pile creation process, and FIG. 6 is the sand pile creation It is a top view which shows the working state in a process.

In the drainage channel installation process, a drainage channel is formed in which a hole is drilled to a predetermined depth in the ground near the target existing object K with a drilling rod 12, drainage material is placed inside the hole, and pore water in the ground is discharged to the ground. Install multiple D's.
As shown in FIG. 3A, the drainage channel D is installed by rotating the drilling rod 12 of the drainage channel installation device 1 and penetrating into the ground. As shown in FIG. A hole is made by penetrating from the ground surface to 15-20 m. Further, as shown in FIG. 3C, the drainage material is inserted into the drill rod 12. The drainage material here is gravel material G such as crushed stone or gravel. Thereafter, as shown in FIG. 3D, while pulling out the drilling rod 12, the gravel material G inserted into the drilling rod 12 is discharged from the discharge port 13 and left inside the hole. This is performed up to the ground surface as shown in FIG. 3E. Thereby, the hole which put the gravel material G inside is formed from the predetermined depth to the ground surface. In this way, the drainage channel D for discharging the pore water in the ground to the ground is installed. In addition, although the drainage channel D is installed so that it may go in the orthogonal | vertical direction with respect to the ground, it is not limited to this, You may make it make an angle from the perpendicular direction and go diagonally. Moreover, the length (length in the depth direction) of the drainage channel D is not limited to 15 to 20 m from the above-described ground surface, and may be other lengths.

  The drainage material here is gravel material G such as crushed stone and gravel, but is not limited to this, and is a board drain material such as paper drain or plastic board drain, or drainage with a plurality of holes in the outer periphery. A perforated pipe with a function may be used.

Moreover, in the drainage channel installation process of this embodiment, the several drainage channels D to install differ in the installation interval of the drainage channel D by the side near the target existing thing K, and the far side.
That is, as shown in FIG. 4, the installation interval P1 of the drainage channel D is narrowed to about 0.75 m at a location closest to the target existing object K, and the installation interval is slightly away from the target existing object K. P2 is slightly expanded to about 1.5 m, and further away from the target existing object K, the installation interval P3 is expanded to about 2.1 m. Thus, the installation interval of the drainage channel D on the side close to the target existing object K is narrowed, and the installation interval is gradually increased as the distance from the target existing object K increases. In addition, the installation space | interval of the drainage channel D is not limited to the above-mentioned thing.

The sand pile creation process is performed after the drainage channel installation process, and the discharge rod 22 is penetrated to a predetermined depth in the ground near the target existing object K where the drainage channel D is installed in the drainage channel installation process. Then, fluidized sand (sand material) is pressurized and discharged from the discharge rod 22, and a plurality of sand piles T are formed to expand the diameter of the discharged fluidized sand and compact the surrounding ground.
The sand pile T is formed by rotating the discharge rod 22 of the sand pile forming device 2 and penetrating into the ground. As shown in FIG. 5A, the discharge rod 22 is penetrated to a predetermined depth, for example, 15 to 20 m from the ground surface. . After the penetration, as shown in FIG. 5B, a predetermined amount of fluidized sand is discharged from the discharge port 23 by applying pressure to the ground while pulling the discharge rod 22 upward by a predetermined distance, for example, 20 to 30 cm. The discharged fluidized sand is expanded in diameter and the surrounding ground is compacted. Thereafter, as shown in FIG. 5C, while the discharge rod 22 is pulled upward by 20 to 30 cm, a predetermined amount of fluidized sand is discharged from the discharge port 23 by applying pressure into the ground to compact the surrounding ground. As shown in FIG. 5D, this process is repeated from a predetermined depth upward, and as shown in FIG. 5E, the ground is compacted by discharging the fluidized sand into the ground to the vicinity of the ground surface. Thereby, the sand pile T which compacts the surrounding ground from predetermined depth to the ground surface vicinity is created. In addition, the length (length of the depth direction) of the sand pile T is not limited to 15-20m from the above-mentioned ground surface, Other length may be sufficient.

  In the sand pile creation process, the plurality of sand piles T to be created are created at positions shifted from the positions of the drainage channels D installed in the drainage channel installation process. At this time, the plurality of sand piles T are formed at predetermined intervals in a range where the ground is improved. For example, as shown in FIG. 6, the creation interval S of the sand piles T is set to about 1.5 m, and the sand pile T is uniformly created over the entire range for improving the ground. In addition, the creation interval of the sand pile T is not limited to the above-mentioned thing. Further, the sand pile T may not be uniformly formed over the entire range of improving the ground, but the formation interval S may be changed according to each place.

In addition, the action (work) of the drainage channel D when the sand pile T is created in the present sand pile creation process will be described.
FIG. 7 is an explanatory view showing the operation of the drainage channel.
As shown in the figure, when the sand pile T is created in the sand pile creation process, the fluidized sand is discharged into the ground by applying pressure, and the pore water pressure of the ground starts to rise due to the diameter expansion of the discharged fluidized sand. At this time, the pore water w in the ground flows into the drainage channel D due to the increase in pore water pressure, and the inflowing pore water w travels through the drainage channel D and is discharged to the ground.
Thus, when the sand pile T is created, the pore water w in the ground is discharged to the ground by the drainage channel D, so that the increase of the pore water pressure in the ground can be suppressed. Generation of displacement can be suppressed.

Next, since the experiment was conducted on the ground improvement method of the present embodiment, this will be described.
In the experiment, a hole is drilled in the ground with a drilling rod 12, and gravel material G (drainage material) such as crushed stones and gravel is placed therein, and a plurality of drainage channels D are installed (drainage channel installation process). After the drainage channel D is installed, the discharge rod 22 penetrates into the ground, the fluidized sand is pressurized and discharged from the discharge rod 22, and a plurality of sand piles T are created in the ground (sand pile creation process). The lateral displacement generated in the shallow part of the ground when creating the sand pile T was measured with a displacement meter.

This lateral displacement was measured several times depending on the progress of the work (construction progress rate) until a plurality of sand piles T were created in the entire ground improvement area and the ground improvement work was completed. . Moreover, the measurement place by a displacement meter was measured at three different points, and these were designated as Experimental Example 1, Experimental Example 2, and Experimental Example 3, respectively. On the other hand, as a comparative example, a plurality of sand piles T were formed in a place where the drainage channel D was not installed on the ground, and the lateral displacement generated in the shallow part of the ground at this time was also measured. Similarly to the above, this measurement is also performed a plurality of times according to the progress of the work (construction progress rate), and is measured at three different points, each of which is Comparative Example 1, Comparative Example 2, and Comparative Example 3. It was.
The results of this experiment are shown in Table 1 below.

As shown in Table 1, in Experimental Example 1 and Experimental Example 2, although the lateral displacement increases as the construction progress rate increases, the increase is not so large, and finally the lateral displacement is around 30 mm. It was. Also in Experimental Example 3, the lateral displacement did not exceed 40 mm. On the other hand, in Comparative Example 1 and Comparative Example 2, the lateral displacement also increased greatly as the construction progress rate increased, and finally the lateral displacement reached nearly 110 mm. Also in Comparative Example 3, the lateral displacement finally exceeded 80 mm.
Thus, the lateral displacement in Experimental Example 1, Experimental Example 2, and Experimental Example 3 was less than half of the lateral displacement in Comparative Example 1, Comparative Example 2, and Comparative Example 3.
That is, from the result of this experiment, it was found that the lateral displacement is greatly reduced.

  As described above, according to the present ground improvement method, a plurality of drainage channels D for discharging pore water in the ground in the drainage channel installation process are installed on the ground in the vicinity of the target existing object K, and then the sand pile creation process By creating a plurality of sand piles T that compact the surrounding ground, the pore water in the ground is discharged to the ground by the installed drainage channel D, and the pore water pressure of the ground rises. To suppress. By suppressing the increase in the pore water pressure, the lateral displacement generated in the shallow part of the ground can be greatly reduced, thereby preventing the target existing object K from being adversely affected by the lateral displacement. .

  In addition, the drainage channel D installed in the ground in the drainage channel installation process can be left installed in the ground without being removed after the ground improvement work is completed, and the drainage channel D can be removed. Eliminate unnecessary work. Thereby, the labor and time required for the work can be greatly reduced, so that the construction cost can be prevented from rising and the construction period can be shortened.

Next, the range in which the drainage channel D is installed in the drainage channel installation process will be described.
FIG. 8 is an explanatory diagram showing a range in which a drainage channel is installed.
As shown in the figure, the range in which the drainage channel D is installed is set to a position that is a predetermined distance A away from the target object K in the horizontal direction, and a plurality of drainage channels D are installed in this range. The predetermined distance A is the same as the length L (15 to 20 m in this case) in the depth direction of the sand pile T created in the sand pile creation process. That is, the range in which the drainage channel D is installed is up to a position 15 to 20 m away from the target existing object K in the horizontal direction.

About this, it is related with the length L of the depth direction of the sand pile T to produce, and the influence of the lateral displacement which generate | occur | produces when constructing the sand pile T in the target existing object K is sand pile. When the length L in the depth direction of T becomes longer, the influence of the lateral displacement on the horizontal direction becomes longer, and when the length L of the sand pile T in the depth direction becomes shorter, the lateral displacement becomes longer in the horizontal direction. The effect of is also shortened. Specifically, the range affected by the lateral displacement in the horizontal direction is substantially the same as the length L in the depth direction of the sand pile T to be created.
Therefore, in order to prevent the target existing object K from being affected by the lateral displacement generated when the sand pile T is formed, the predetermined distance A in the horizontal direction away from the target existing object K is the sand pile to be formed. The length is the same as the length L in the depth direction of T. The predetermined distance A may be longer than the length L in the depth direction of the sand pile T to be created. However, if the length A is longer, the range in which the drainage channel D is installed is expanded accordingly, and the installation work increases. Therefore, the construction cost increases. That is, in order to make the existing object K not affected by the lateral displacement and to reduce the construction cost, the predetermined distance A in the horizontal direction away from the existing object K in the range where the drainage channel D is installed is set to the sand. It is good to make it the same with the length L of the depth direction of the sand pile T created in a pile creation process.

Next, another embodiment of the ground improvement method of the present invention will be described.
In addition, since this ground improvement method differs in the drainage channel D installed at a drainage channel installation process from the method of the above-mentioned embodiment and others are the same, only this drainage channel D is demonstrated here.
FIG. 9 is an explanatory diagram showing another example of the drainage channel installed in the drainage channel installation process.

  The drainage channel D has a hole drilled in the ground with a drilling rod 12 and, as shown in FIG. 9, for example, gravel material G (drainage material) such as crushed stone and gravel is provided in the substantially lower half (lower side) of the inside of the hole. At the same time, a pipe C for preventing collapse of the hole is disposed, for example, in a substantially upper half (upper side) of the hole. Further, a drainage pump 31 is provided on the ground, and the suction hose 32 of the drainage pump 31 is inserted into a gravel material G such as crushed stone or gravel below the inside of the hole. In this drainage channel D, the pore water in the ground flows in at approximately the lower half of the drainage channel D, and the drainage pump 31 forcibly discharges the pore water that has entered into the ground.

  Thus, by forcibly discharging the pore water that has flowed into the drainage channel D, the pore water in the ground can be reliably discharged to the ground, and an increase in the pore water pressure in the ground can be suppressed. Thereby, the lateral displacement generated in the shallow part of the ground can be greatly reduced, and the adverse effect of the lateral displacement on the target existing object K can be prevented.

  DESCRIPTION OF SYMBOLS 1 ... Drainage installation apparatus, 2 ... Sand pile formation apparatus, 10 ... Construction machine, 11 ... Mast, 12 ... Drilling rod, 13 ... Discharge port, 14 ... Excavation part, 15 ... Rotation part, 16 ... Lifting part, 20 ... construction machine, 21 ... mast, 22 ... discharge rod, 23 ... discharge port, 24 ... rotating part, 25 ... lift part, 26 ... peripheral equipment, 27 ... fluidized sand generator, 28 ... pressure feed pump, 29 ... pressure gauge 31 ... Drain pump, 32 ... Suction hose.

Claims (5)

A ground improvement method for creating a sand pile in the ground in the vicinity of the target existing object and compacting the surrounding ground,
A drainage channel installation process in which a hole is drilled to a predetermined depth with a drilling rod in the ground near the target existing object, drainage material is put inside the hole, and a plurality of drainage channels for discharging pore water in the ground are installed,
In the ground near the target existing object where the drainage channel was installed in the drainage channel installation process, the discharge rod penetrates to a predetermined depth, and after the penetration, the sand material is drained from the discharge rod, and the discharged sand material is expanded in diameter to surround it. Sand pile creation process to create multiple sand piles to compact the ground,
The ground improvement method characterized by having. In the ground improvement method according to claim 1,
The ground improvement method characterized by narrowing the installation space | interval of the drainage channel of the side close | similar to a target existing thing, and widening a setting space | interval as it leaves | separates from a target existing thing for several drainage channels installed in a drainage channel installation process. In the ground improvement method according to claim 1 or 2,
The range where the drainage channel is installed in the drainage channel installation process is to a position that is a predetermined distance away from the target existing object in the horizontal direction, and this predetermined distance is the same as the length in the depth direction of the sand pile created in the sand pile creation process. The ground improvement method characterized by making it. In the ground improvement method according to any one of claims 1 to 3,
The ground improvement method characterized in that the drainage material to be put into the drainage channel is gravel material such as crushed stone or gravel, board type drain material such as paper drain or plastic board drain, or perforated pipe. In the ground improvement method according to any one of claims 1 to 4,
In the drainage channel, drainage material is placed on the lower side of the drainage channel, and a pipe is arranged on the upper side, and a drainage pump is provided to forcibly discharge the interstitial water that has flowed into the drainage channel. A ground improvement method characterized.

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