JP6934697B2 - Ground improvement method - Google Patents

Description

The present invention relates to a ground improvement method for forming sand piles in the ground in the ground near the target existing object and compacting the surrounding ground.
Here, the target existing object is a building such as a house, a building or a warehouse, an existing structure such as a road, a railroad 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 sand piles 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 is a vertical discharge rod that discharges sand material (here, fluidized sand) by applying pressure into the ground from the lower end, and penetration and withdrawal of the discharge rod into the ground. The construction machine has a construction machine that penetrates the discharge rod to a predetermined depth, and after the penetration, the fluidized sand is discharged from the lower end of the discharge rod by applying pressure into the ground. By discharging the fluidized sand into the ground until it reaches a predetermined amount, the fluidized sand expands in diameter and a part of sand piles for compacting the surrounding ground is created. By repeating this while pulling out the discharge rod from a predetermined depth little by little with a construction machine, sand piles are created in the ground and the surrounding ground is compacted (see Patent Document 1).

By the way, in the ground improvement method such as the sand press-fit type static compaction method, a sand pile is created by expanding the diameter of the fluidized sand discharged into the ground and compacting the surrounding ground. (During ground improvement), the pore water pressure in the ground rises due to the expansion of the diameter of the fluidized sand in the ground, and along with this, lateral displacement occurs in which the ground is displaced in the horizontal direction in the shallow part of the ground.

In this ground improvement method, when the ground near the target existing object is improved, the lateral displacement generated in the shallow part of the ground may adversely affect the target existing object. Therefore, conventionally, in order to prevent the existing object from being adversely affected, a displacement buffer groove or a displacement buffer wall using a steel sheet pile or the like is installed in the ground.
FIG. 10A is a plan view showing the installation state of the conventional displacement buffer groove, and FIG. 10B is a plan view showing the installation state of the conventional displacement buffer wall.
As shown in the figure, the displacement buffer groove M or the displacement buffer wall W reaches a predetermined depth in the ground between the range for improving the ground by creating a sand pile T in the ground and the target existing object K (boundary). As such, 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 it is possible to prevent the target existing object K from being adversely affected by the lateral displacement.

However, when the displacement buffer groove M is installed, the displacement buffer groove M may collapse due to the lateral displacement, and when the collapse occurs, it is necessary to dig up the displacement buffer groove M again and re-install it. Further, after the ground improvement work is completed, the installed displacement buffer groove M must be backfilled, and these works require a great deal of labor and time. Therefore, there are problems such as soaring construction cost and prolongation of construction period.
Further, even when the displacement buffer wall W is installed, after the ground improvement work is completed, the installed displacement buffer wall W must be removed from the ground, which is a great work for removing the displacement buffer wall W. It takes a lot of effort and time. Therefore, there are problems such as soaring construction cost and prolongation of construction period.

JP-A-2010-13885

The present invention has been made in view of such a problem, and an object of the present invention is to prevent the existing object from being adversely affected by lateral displacement when improving the ground in the vicinity of the existing object. It is to prevent soaring construction costs and shorten the construction period.

In the present invention, a drainage channel is provided in which a hole is made in the ground near the target existing object to a predetermined depth with a drilling rod, a drainage material is put inside the hole, and a plurality of drainage channels for discharging pore water in the ground are installed. The discharge rod is penetrated to a predetermined depth in 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. It has a sand pile construction process that creates a plurality of sand piles that compact the surrounding ground, and also covers the area where the drainage channel is installed in the drainage channel installation process. Based on the relationship between the impact and the length in the depth direction of the sand pile to be created, horizontally from the target existing object to a position the same distance as the length in the depth direction of the sand pile to be created in the sand pile construction process. This is a ground improvement method.

According to the present invention, when a sand pile is constructed in the sand pile construction process, the pore water in the ground is discharged to the ground by the drainage channel installed in the drainage channel installation process, and the increase in the pore water pressure in the ground is suppressed. It is possible to significantly reduce the lateral displacement that occurs in the shallow part of the ground, and it is possible to prevent the existing object from being adversely affected by the lateral displacement.
In addition, even after the ground improvement work is completed, the drainage channel installed in the ground can be left as it is without being removed, and the work can be simplified by eliminating the need for removing the drainage channel. It is possible to significantly reduce the labor and time required for the work, prevent the construction cost from rising, and shorten the construction period.

It is explanatory drawing of the drainage channel installation device used in the ground improvement method of this invention. It is explanatory drawing of the sand pile making apparatus used in the ground improvement method of this invention. It is explanatory drawing which shows the drainage channel installation process. It is a top view which shows the working state in a drainage channel installation process. It is explanatory drawing which shows the sand pile construction process. It is a top view which shows the working state in a sand pile construction process. It is explanatory drawing which shows the operation of a drainage channel. It is explanatory drawing which shows the range to install a drainage channel. It is explanatory drawing which shows another example of the drainage channel installed in the drainage channel installation process. It is a top view which shows the installation state of the conventional displacement buffer groove or 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 main ground improvement method) is to create sand piles in the ground in the ground near the target existing object to compact the surrounding ground. Here, the target existing structure will be described as an existing structure such as a building or a structure.
The ground improvement method is roughly defined as a drainage channel installation process in which multiple drainage channels for draining interstitial water in the ground are installed in the ground near the target existing object, and a drainage channel installation process in the drainage channel installation process. It has a sand pile construction step of constructing a plurality of sand piles for compacting the surrounding ground on the ground near the existing object.

In this ground improvement method, in the sand pile construction process, the ground improvement by the sand press-fitting static compaction method is taken as an example for explanation, but this sand pile preparation process is not limited to this, and sand is not limited to this. The ground may be improved by another construction method such as the compaction pile construction method.

The device for improving the ground by this ground improvement method is composed of a drainage channel installation device used in the drainage channel installation process and a sand pile construction device used in the sand pile construction process.
FIG. 1 is an explanatory view of a drainage channel installation device used in the main ground improvement method, and FIG. 2 is an explanatory view of a sand pile construction device used in the main ground improvement method.

As shown in FIG. 1, the drainage channel installation device 1 has a self-propellable construction machine 10, and the construction machine 10 has a mast 11 erected in front of the mast 11 and moves up and down along the mast 11. It has a drilling rod 12. The drilling rod 12 is a hollow pipe, and a discharge port 13 is provided at the lower end thereof, and an excavation portion 14 is provided to penetrate into the ground to make a hole. Further, above the drilling rod 12, a rotating portion 15 for rotating the drilling rod 12 and an elevating portion 16 for penetrating and pulling out the drilling rod 12 into the ground are provided.

As shown in FIG. 2, the sand pile construction device 2 has a self-propelled construction machine 20, and the construction machine 20 erects a mast 21 in front of the mast 21 and moves up and down along the mast 21. It has a discharge rod 22. The discharge rod 22 is a hollow pipe through which a sand material (here, fluidized sand) and compressed air pass, and has a discharge port 23 at the lower end for discharging the fluidized sand into the ground. Further, above the discharge rod 22, a rotating portion 24 for rotating the discharge rod and an elevating portion 25 for penetrating and pulling out the discharge rod 22 into the ground are provided.
Here, the fluidized sand is a sand material that has been fluidized by mixing a fluidizing agent with the sand.
Further, the sand material is not limited to fluidized sand. For example, when the ground is improved by the sand compaction pile method in the sand pile construction process, the sand material is sand, crushed stone, slag, or a mixture thereof. be.

In addition, the sand pile construction device 2 has peripheral equipment 26 that supplies fluidized sand to the discharge rod 22 of the construction machine 20. Peripheral equipment 26 has a fluidized sand generator 27 that mixes a fluidizing agent with sand to generate fluidized sand, sends fluidized sand from the fluidized sand generator 27 by a pressure pump 28, and uses a pressure gauge. 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 construction 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 construction 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 construction process.

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

In the drainage channel installation process, a hole is made in the ground near the target existing object K to a predetermined depth with a drilling rod 12, a drainage material is put inside the hole, and the pore water in the ground is discharged to the ground. Install multiple Ds.
To install the drainage channel D, as shown in FIG. 3A, the drilling rod 12 of the drainage channel installation device 1 is rotated to penetrate into the ground, and as shown in FIG. 3B, the drilling rod 12 is set to a predetermined depth, for example. Make a hole by penetrating from the ground surface to 15 to 20 m. Further, as shown in FIG. 3C, the drainage material is inserted into the drilling rod 12. The drainage material here is gravel material G such as crushed stone and gravel. Then, 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 done to the ground surface as shown in FIG. 3E. As a result, a hole containing the gravel material G is formed from a predetermined depth to the ground surface. In this way, the drainage channel D for discharging the interstitial water in the ground to the ground is installed. The drainage channel D is installed so as to face in the direction perpendicular to the ground, but the present invention is not limited to this, and the drainage channel D may be installed diagonally at an angle from the vertical direction. Further, the length of the drainage channel D (length in the depth direction) is not limited to 15 to 20 m from the above-mentioned ground surface, and may be any other length.

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

Further, in the drainage channel installation process of the present embodiment, the plurality of drainage channels D to be installed have different installation intervals of the drainage channels D on the side near the target existing object K and the side far from the target existing object K.
That is, as shown in FIG. 4, the installation interval P1 of the drainage channel D is narrowed to about 0.75 m at the place closest to the target existing object K, and the installation interval is narrowed to about 0.75 m at a place slightly away from the target existing object K. P2 is slightly widened to about 1.5 m, and the installation interval P3 is widened to about 2.1 m at a place further away from the target existing object K. In this way, the installation interval of the drainage channel D on the side closer 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. The installation interval of the drainage channel D is not limited to the above.

The sand pile construction 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, and after penetration. , The fluidized sand (sand material) is pressurized and discharged from the discharge rod 22, and the discharged fluidized sand is expanded in diameter to form a plurality of sand piles T for compacting the surrounding ground.
In the construction of the sand pile T, the discharge rod 22 of the sand pile construction device 2 is rotated to penetrate into the ground, and 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 penetration, as shown in FIG. 5B, while pulling out the discharge rod 22 upward by a predetermined distance, for example, 20 to 30 cm, a predetermined amount of fluidized sand is discharged from the discharge port 23 by applying pressure into the ground and into the ground. The discharged fluidized sand is expanded in diameter to compact the surrounding ground. After that, as shown in FIG. 5C, while pulling out the discharge rod 22 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 is repeated from a predetermined depth upward, and as shown in FIG. 5E, the ground is compacted by discharging fluidized sand into the ground to the vicinity of the ground surface. As a result, a sand pile T that compacts the surrounding ground from a predetermined depth to the vicinity of the ground surface is created. The length (length in the depth direction) of the sand pile T is not limited to 15 to 20 m from the above-mentioned ground surface, and may be any other length.

Further, in the sand pile construction process, the plurality of sand piles T to be created are created at positions deviated from the position of the drainage channel D installed in the drainage channel installation process. At this time, the plurality of sand piles T are created at predetermined intervals within the range for improving the ground. For example, as shown in FIG. 6, the construction interval S of the sand piles T is set to about 1.5 m, and the sand piles T are uniformly constructed over the entire area for improving the ground. The construction interval of the sand pile T is not limited to the above. Further, the sand pile T may not be uniformly formed over the entire area for improving the ground, but the creation interval S may be changed according to each place.

Further, in the main sand pile construction step, the action (work) of the drainage channel D when the sand pile T is constructed will be described.
FIG. 7 is an explanatory diagram showing the operation of the drainage channel.
As shown in the figure, when sand pile T is constructed in the sand pile construction step, fluidized sand is discharged into the ground by applying pressure, and the pore water pressure in the ground begins to rise due to the expansion of the diameter of the discharged fluidized sand. At this time, due to the increase in the pore water pressure, the pore water w in the ground flows into the drainage channel D, and the inflowing pore water w is discharged to the ground through the inside of the drainage channel D.
In this way, when the sand pile T is constructed, the pore water w in the ground is discharged to the ground by the drainage channel D, so that the increase in the pore water pressure in the ground is suppressed, thereby laterally in the shallow part of the ground. The occurrence of displacement can be suppressed.

Next, an experiment was conducted on the ground improvement method of the present embodiment, which will be described.
In the experiment, a hole is made in the ground with a drilling rod 12, a gravel material G (drainage material) such as crushed stone or gravel is put in the hole, and a plurality of drainage channels D are installed (drainage channel installation process). After the drainage channel D is installed, the discharge rod 22 is penetrated into the ground, fluidized sand is pressurized and discharged from the discharge rod 22, and a plurality of sand piles T are formed in the ground (sand pile construction step). The lateral displacement generated in the shallow part of the ground when the sand pile T was constructed was measured with a displacement meter.

This lateral displacement was measured multiple times according to the progress of the work (construction progress rate) until a plurality of sand piles T were created over the entire area for improving the ground and the ground improvement work was completed. .. In addition, the measurement locations of the displacement meters were measured at three different points, which 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 constructed in a place where the drainage channel D was not installed in the ground, and the lateral displacement generated in the shallow part of the ground at this time was also measured. Similar to the above, this measurement is also performed multiple times according to the progress of work (construction progress rate), and is also measured at three different points, and each of them is compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3. And said.
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. rice field. 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 increased significantly as the construction progress rate increased, and finally the lateral displacement reached nearly 110 mm. Further, also in Comparative Example 3, the lateral displacement finally exceeded 80 mm.
As described above, the lateral displacements in Experimental Example 1, Experimental Example 2, and Experimental Example 3 were less than half of the lateral displacements in Comparative Example 1, Comparative Example 2, and Comparative Example 3.
That is, from the results of this experiment, it was found that the lateral displacement was significantly reduced.

As described above, according to the ground improvement method, after installing a plurality of drainage channels D for discharging pore water in the ground in the drainage channel installation process in the ground near the target existing object K, a sand pile construction process is performed. By creating a plurality of sand piles T that compact the surrounding ground, when the sand piles T are created, the pore water in the ground is discharged to the ground by the installed drainage channel D, and the pore water pressure in the ground rises. Suppress. By suppressing the increase in pore water pressure, the lateral displacement that occurs in the shallow part of the ground can be significantly reduced, and this can prevent 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 even after the ground improvement work is completed, and the drainage channel D removal work can be performed. Make it unnecessary and simplify the work. As a result, the labor and time required for the work can be significantly reduced, 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 the drainage channel is installed.
As shown in the figure, the range in which the drainage channel D is installed is a position horizontally separated from the target existing object K by a predetermined distance A, and a plurality of drainage channels D are installed in this range. The predetermined distance A is the same as the length L (here, 15 to 20 m) in the depth direction of the sand pile T created in the sand pile creating step. That is, the range in which the drainage channel D is installed is a position 15 to 20 m horizontally away from the target existing object K.

Regarding this, the influence of the lateral displacement that occurs when the sand pile T is created in the target existing object K is related to the length L in the depth direction of the sand pile T to be created, and the sand pile When the length L in the depth direction of T becomes long, the influence of the lateral displacement in the horizontal direction also becomes long, and when the length L in the depth direction of the sand pile T becomes short, the lateral displacement becomes horizontal. 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.
From this, in order to prevent the target existing object K from being affected by the lateral displacement that occurs when the sand pile T is created, a predetermined horizontal distance A away from the target existing object K is the sand pile to be created. Make it 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, but if it is made longer, the range in which the drainage channel D is installed is expanded and the installation work is increased. Therefore, the construction cost increases. That is, in order to prevent the target existing object K from being affected by the lateral displacement and to reduce the construction cost, sand is set at a predetermined horizontal distance A away from the target existing object K in the range where the drainage channel D is installed. It is preferable that the length L of the sand pile T created in the pile forming step in the depth direction is the same.

Next, another embodiment of the ground improvement method of the present invention will be described.
Since this ground improvement method is different from the method of the above-described embodiment in the drainage channel D installed in the drainage channel installation step and is the same in other respects, only this drainage channel D will be described here.
FIG. 9 is an explanatory diagram showing another example of the drainage channel installed in the drainage channel installation process.

In the drainage channel D, a hole is made in the ground with a drilling rod 12, and as shown in FIG. 9, a gravel material G (drainage material) such as crushed stone or gravel is placed in, for example, substantially the lower half (lower side) of the inside of the hole. At the same time, a pipe C for preventing the hole from collapsing is arranged inside the hole, for example, in the substantially upper half (upper side). Further, a drainage pump 31 is provided on the ground, and the suction hose 32 of the drainage pump 31 is inserted into the gravel material G such as crushed stone or gravel on the lower side inside the hole. In this drainage channel D, the interstitial water in the ground flows into the substantially lower half of the drainage channel D, and the inflowing interstitial water is forcibly discharged to the ground by the drainage pump 31.

By forcibly discharging the pore water that has flowed into the drainage channel D in this way, 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. As a result, the lateral displacement generated in the shallow part of the ground can be significantly reduced, and it is possible to prevent the target existing object K from being adversely affected by the lateral displacement.

1 ... Drainage channel installation device, 2 ... Sand pile construction device, 10 ... Construction machine, 11 ... Mast, 12 ... Drilling rod, 13 ... Discharge port, 14 ... Excavation part, 15 ... Rotating part, 16 ... Elevating part, 20 ... Construction machine, 21 ... Mast, 22 ... Discharge rod, 23 ... Discharge port, 24 ... Rotating part, 25 ... Elevating part, 26 ... Peripheral equipment, 27 ... Fluidized sand generator, 28 ... Pump pump, 29 ... Pressure gauge , 31 ... drainage pump, 32 ... suction hose.

Claims (4)

It is a ground improvement method that creates sand piles in the ground near the target existing object and compacts the surrounding ground.
A drainage channel installation process in which a hole is made in the ground near the target existing object to a predetermined depth with a drilling rod, drainage material is put inside the hole, and multiple drainage channels are installed to drain the pore water in the ground.
The discharge rod is penetrated to a predetermined depth in the ground near the target existing object where the drainage channel was installed in 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 to surround it. The sand pile construction process to create multiple sand piles that compact the ground, and
And it has a,
The range of drainage channel installation in the drainage channel installation process is horizontal from the target existing object based on the relationship between the effect of lateral displacement that occurs when sand piles are created and the length of the sand piles to be created in the depth direction. A ground improvement method characterized in that the length of the sand pile to be created in the sand pile construction process is the same as the length in the depth direction of the sand pile. In the ground improvement method according to claim 1,
A ground improvement method characterized in that a plurality of drainage channels installed in the drainage channel installation process narrow the installation intervals of drainage channels on the side closer to the target existing object and widen the installation intervals as the distance from the target existing object increases. In the ground improvement method according to claim 1 or 2.
A ground improvement method characterized in that the drainage material to be put into the drainage channel is a gravel material such as crushed stone or gravel, a board drain material such as a paper drain or a plastic board drain, or a perforated pipe. In the ground improvement method according to any one of claims 1 to 3,
The drainage channel is equipped with a drainage pump and a drainage material is placed on the lower side of the inside and a pipe is placed on the upper side. A characteristic ground improvement method.

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