JP6905816B2 - Displacement-reducing compaction sand pile construction hollow pipe and compaction sand pile construction method - Google Patents

Description

The present invention relates to a hollow pipe for forming a compacted sand pile that reduces displacement generated due to diameter expansion during compaction, and a method for forming a compacted sand pile using the hollow pipe.

Conventionally, as shown in FIGS. 10 and 11, ground improvement sand for improving the ground by placing compacted sand piles 82 in soft ground A such as loose sandy ground or highly water-containing viscous ground. There is a pile construction method (Japanese Unexamined Patent Publication No. 2003-147756). In this ground improvement sand pile construction method, for example, after penetrating the hollow pipe 80 to a predetermined depth H, a step of pulling out the hollow pipe 80 to an appropriate length and a step of re-penetrating the hollow pipe 80 are sequentially performed. This is a compaction sand pile construction method in which a compaction sand pile 82 is constructed in the soft ground A by repeating the process up to the ground surface.

In such a compaction sand pile construction method, the displacement (arrow Z in FIG. 11) that occurs due to the diameter expansion during compaction is the above-ground structure 92 and trees and other natural objects 93 that are close to the ground improvement area 95. , The existing structure 96 such as the underground structure 94 may be adversely affected. Therefore, for example, an empty hole or groove 91 is provided between the ground improvement area 95 and the existing structure 96 to absorb the displacement Z (91a in FIG. 11).

Japanese Unexamined Patent Publication No. 2003-147756 Japanese Unexamined Patent Publication No. 9-125359

However, in the case of the compaction sand pile construction method, the holes and grooves 91 of the empty digging for displacement reduction measures require a predetermined size and shape in width, depth and length, so that the ground improvement area 95 and the existing structure It is necessary to provide a countermeasure area between 96 and 96. In this case, the range of the ground improvement area 95 may be limited. Further, since the holes and grooves 91 of the empty digging are close to the ground improvement area 95, there is also a problem that the improvement effect of the ground improvement area 95 is diminished. Further, in addition to the compaction sand pile construction method, a separate process for adding holes and grooves 91 for empty digging is required, which complicates the construction and increases the construction cost.

Further, Japanese Patent Application Laid-Open No. 9-125359 describes a step of providing a plurality of excavation holes around the ground for ground improvement and installing a rubber tube (buffer) loaded with a liquid inside the excavation holes, and ground improvement. A ground improvement method including a process of constructing a sand pile while vibrating it in the ground is disclosed. In this ground improvement method, a buffer zone in which a buffer is installed is provided between the place where the SCP method is used and the adjacent land, and the transmission of vibration and displacement to the adjacent land is suppressed. However, according to the construction method described in Japanese Patent Application Laid-Open No. 9-125359, it is necessary to provide an area for a buffer zone between the ground improvement area and the existing structure, as in the case of the holes and grooves of the empty excavation for the displacement reduction measures. Similarly, the range of the ground improvement area is limited.

In addition, as a ground improvement sand pile construction method other than the above-mentioned compaction sand pile construction method, the casing tube is rotated all around, the inside of the casing hole is excavated by a middle excavator, sand is thrown in after the excavation is completed, and compaction is performed. The all-turning cast-in-place sand pile construction method for solidifying and creating sand piles is also known. According to this construction method, high-quality cast-in-place sand piles can be created because of the all-casing. However, in the case of the all-turning place-casting sand pile construction method, the construction efficiency is poor and the cost is high.

Therefore, an object of the present invention is to solve the problem of displacement that adversely affects the existing structure and to construct the existing structure without providing a buffer zone such as a hole or a groove for empty digging between the ground improvement area and the existing structure. An object of the present invention is to provide a hollow pipe for forming a compacted sand pile with high efficiency, and another object of the present invention is to create a compacted sand pile having excellent construction efficiency without giving displacement to an existing structure. It is to provide a construction method.

That is, the present invention solves the above-mentioned conventional problems, and is a hollow pipe used in a method of forming a compacted sand pile in soft ground, and has inclined blades on the outer peripheral surface of the hollow pipe main body. Provided is a hollow pipe for forming a compacted sand pile, which is characterized by forming the above.

The present invention also provides the hollow pipe for forming a compacted sand pile, characterized in that an injection port for injecting jet water is formed around the hollow pipe at the tip of the hollow pipe main body. To do.

Further, the present invention provides the hollow pipe for forming a compacted sand pile, wherein the injection port is formed in the hollow pipe main body.

Further, the present invention further provides the hollow pipe for forming a compacted sand pile, which is characterized in that an excavation bit is formed.

Further, the present invention includes a step of penetrating the hollow pipe to a predetermined depth while rotating the hollow pipe and discharging the soil around the hollow pipe to the ground surface, and pulling out the hollow pipe to an appropriate length in the hollow pipe. The step of discharging the sand pile material and the step of pushing back the hollow pipe are sequentially repeated up to the ground surface, and the step of forming a compaction sand pile in the soft soil is performed. It provides a method for creating sand piles.

Further, the present invention comprises a step of injecting jet water from the injection port while rotating the hollow pipe and penetrating to a predetermined depth while loosening or muddying the circumference of the hollow pipe.
The process of stopping the injection of jet water, pulling out the hollow pipe to an appropriate length, discharging the sand pile material in the hollow pipe, and pushing back the hollow pipe are repeated in sequence until the surface of the ground is softened. Provided is a method for forming a compacted sand pile, which comprises performing a step of forming a compacted sand pile in the ground.

According to the present invention, before the compaction step, a step of making the circumference of the hollow pipe into a loosened state or a muddy state is performed. For this reason, the soil in the loosened or muddy part is discharged to the ground surface due to the diameter-expanding pressure at the time of impacting, and a compacted sand pile with an expanded diameter is created in the loosened or muddy area. .. Therefore, it is possible to greatly suppress the transmission of displacement to the existing structure without providing a buffer zone between the ground improvement area and the existing structure.

It is the schematic of the compaction sand pile construction apparatus provided with the hollow pipe in the 1st Embodiment of this invention. It is an enlarged view of the tip part of the hollow pipe for making compaction sand pile of FIG. It is a side view of FIG. It is a top view of FIG. It is a figure explaining the penetration process of the compaction sand pile construction method in 1st Embodiment of this invention. It is a figure explaining the compaction process of the compaction sand pile construction method of FIG. It is an enlarged view of the tip part of the hollow pipe for making a compaction sand pile in the 2nd Embodiment of this invention. It is a side view of FIG. FIG. 7 is a plan view of FIG. 7. It is a figure explaining the conventional compaction sand pile construction method. It is another figure explaining the conventional compaction sand pile construction method.

Next, the hollow pipe for forming a compacted sand pile (hereinafter, also simply referred to as “hollow pipe”) according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. The hollow pipe 10 is a conventional hollow pipe for forming a compacted sand pile, in which inclined blades 12 are formed on the outer peripheral surface of the hollow pipe main body 11. The upper portion of the hollow pipe main body 11 has, for example, a hopper 17 connected to a rotating device 15 and a forced lifting device 16 and further loaded with a sand pile material 19.

The inclined blade 12 mainly discharges the soil in the stirring area around the hollow pipe to the ground surface at the time of penetrating and compacting the hollow pipe 1. The inclined blade 12 may be any blade excluding horizontal blades and vertical blades, and examples thereof include spiral blades, partial spiral blades in which the middle of the spiral blades is missing, and plate-shaped inclined blades having a rectangular cross section. In the case of the spiral blade, the forming position may be any of substantially the entire length of the hollow tube main body 11 and a part of the total length of the hollow tube main body 11. Further, the pitch (p) of the spiral blades is appropriately determined in consideration of the stirring efficiency and the soil removal efficiency. By forming the spiral blade on the outer peripheral surface of the hollow pipe main body 11, the hollow pipe main body 11 can be easily penetrated into the ground, and the soil around the hollow pipe can be discharged to the ground surface. Further, the winding direction of the spiral blade may be any of right-handed winding, left-handed winding, and composite winding having both right-handed winding and left-handed winding. The radial length (blade diameter) l ₁ of the spiral blade may be about 1 to 0.7 times the compaction sand pile _{diameter l 2.} If the radial length (blade diameter) l _{1 of the spiral blade is the same as the compaction sand pile diameter l 2} , the compaction sand pile 42 is formed in the stirring region or the loosening region around the hollow pipe. Therefore, it becomes 100% replacement. In this case, the displacement transmission to the existing structure can be made almost zero. On the other hand, if the radial length (blade diameter) l _{1 of} the spiral blade is less than 1 of the compacted sand pile _{diameter l 2} and 0.7 or more, the surrounding ground around the stirring region or the loosening region is slightly expanded. The sand pile 42 will be formed, and the displacement transmission to the existing structure cannot be set to zero, but it will be suppressed as compared with the conventional case.

The excavation bit 14 is an arbitrary component, and when the hollow pipe 10 is penetrated, the earth and sand around the hollow pipe is excavated to facilitate the penetration of the hollow pipe 10. In this example, the excavation bit 14 has a pair of bits formed at the tip of the hollow pipe main body 11 at positions (both sides) that are 180 degrees out of phase in a plan view.

Next, a method for forming a compacted sand pile using the hollow pipe 10 of the first embodiment will be described with reference to FIGS. 5 and 6. First, the hollow tube 10 is set at a predetermined position. At this time, the sand pile material 19 is loaded in the hollow pipe main body 11. While rotating the hollow pipe 10, the step of penetrating the soil around the hollow pipe to a predetermined depth H while discharging the soil to the ground surface is performed (FIGS. 5A to 5C). When the rotation of the hollow pipe 10 is a forward rotation, if the penetration speed is within 1 pitch of the blades per rotation of the hollow pipe 10, the soil around the hollow pipe is affected by the pushing force of the inclined blades. It will be discharged to the surface of the earth. The penetration speed of the hollow pipe 10 is preferably a constant speed. In the intrusion step of the hollow pipe 10, the soil around the hollow pipe is discharged to the ground surface, and a loose state 30 is formed around the hollow pipe. As a result, the displacement at the time of penetration becomes almost zero. Further, it is preferable that the volume of the soil discharged to the ground surface is substantially the same as the volume of the hollow pipe intrusion and the volume of the soil discharged to the ground surface from the viewpoint of reducing the influence of displacement to the periphery at the time of penetration. As the sand pile material 19, a known material similar to the conventional compaction sand pile construction method can be used. In the process of penetrating the hollow pipe 10, the penetration of the hollow pipe 10 may be temporarily stopped in the process of penetrating the hollow pipe 10 from the ground surface into the ground, and the hollow pipe 10 may be pulled up. You may. Thereby, the amount of soil discharged can be controlled.

Next, the step of pulling out the hollow pipe 10 to an appropriate length, discharging the sand pile material 19 in the hollow pipe 10, and the step of punching back (re-penetrating) the hollow pipe 10 are sequentially performed up to the ground surface. Repeatedly, a step of forming a compaction sand pile 42 in the soft ground is performed (FIGS. 6A to 6D). The compaction sand pile construction process is the same as the conventional compaction sand pile construction process, and the backing may be performed by backing up the length according to the amount of the removed sand pile material by the control instrument. Further, in the compaction sand pile construction process, the soil in the loosened portion is discharged to the ground surface due to the diameter-expanding pressure at the time of backing. In FIG. 6, reference numeral 32 is the discharged soil at the time of sand pile construction. In the step of discharging the sand pile material 19 in the hollow pipe 10, the hollow pipe 10 may be either non-rotating or rotating. Further, also in the step of punching back (re-penetrating) the hollow tube 10, the hollow tube 10 may be either non-rotating or rotating. In both the sand pile material discharge step and the backing step, the amount of discharged soil can be adjusted by rotating the hollow pipe 10. When the amount of soil discharged is not as expected, such as when the amount of soil discharged is too large or too small, the amount of soil discharged can be adjusted by changing the rotation method of the hollow pipe 10.

In the compaction sand pile construction process, if the amount of soil discharged at the time of construction 32 and the amount of soil of the compaction sand pile (expanded diameter) are almost the same, the displacement at the time of construction can be made almost zero. .. Further, when the amount of soil discharged at the time of construction 32 is smaller than the amount of soil of the compacted sand pile (expanded diameter), the displacement at the time of construction cannot be set to zero, but the conventional compacted sand pile is constructed. It can be reduced as compared with the process.

Next, the hollow tube in the second embodiment will be described with reference to FIGS. 7 to 9. In FIGS. 7 to 9, the same components as those in FIGS. 1 to 4 are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described. That is, in the hollow pipe 10a of FIGS. 7 to 9, the difference from the hollow pipe 10 of FIGS. 1 to 4 is that the jet water is jet water around the hollow pipe or below the hollow pipe at the tip of the hollow pipe main body 11. Is further formed as an injection port 13 for injecting.

The injection port 13 is an opening for injecting jet water around the hollow pipe or below the hollow pipe, and is one tip of the jet water injection pipe 21. The jet water injection pipe 21 passes through the hollow portion of the hollow pipe 10a, and the other tip is connected to a jet water supply pump (not shown) on the ground surface. The installation position of the injection port 13 is near the tip of the hollow tube main body 11. The injection direction of the jet water emitted from the injection port 13 may be any of the rotation direction, the counter-rotation direction, the radial direction, and the penetration direction of the hollow pipe 10a, but it is efficient and uniform loosening state to inject in the penetration direction. Alternatively, it is preferable in that a muddy water state can be obtained. In this example, a pair of left and right injection ports 13 are installed on the outer peripheral surface of the hollow tube main body 11 so as to project in the radial direction and the openings face in the penetration direction. As a result, when the hollow pipe 10a penetrates, jet water can be sprayed onto the earth and sand around the hollow pipe.

Examples of the jet water include low-pressure water, water such as medium-pressure water or high-pressure water, high-pressure air accompanied by water, and water containing a fluidizing agent. The fluidizing agent can be used on soft ground of sandy soil to loosen the soil around the hollow pipe. Examples of the fluidizing agent include a water-absorbing polymer and a polymer flocculant. Examples of the water-absorbent polymer include a partially crosslinked product of a sodium acrylate polymer and a crosslinked product of a sodium acrylate polymer. Examples of the polymer flocculant include a nonionic polymer flocculant, an anionic polymer flocculant, a cationic polymer flocculant and an amphoteric polymer flocculant. The blending ratio of the fluidizing agent is appropriately determined. The jet water injection may be a pressure that loosens the soil through which the inclined blades 12 pass, and is appropriately determined according to the soil quality of the soft ground and the length of the inclined blades 12.

Next, a method for forming a compacted sand pile using the hollow pipe 10a of the second embodiment will be described with reference to FIGS. 5 and 6. 5 and 6 are explanatory views of a method for forming a compacted sand pile using the hollow pipe 10 of the first embodiment, but the hollow pipe 10a of the second embodiment is shown. Since the compaction sand pile construction method used is the same except that the soil condition around the hollow pipe is different, it is also used for the explanation of the second sand pile construction method. First, the hollow tube 10a is set at a predetermined position. At this time, the sand pile material 19 is loaded in the hollow pipe main body 11. While rotating the hollow pipe 10a, jet water is injected from the injection port 13 to loosen the circumference of the hollow pipe or make it muddy, and perform a step of penetrating to a predetermined depth H (FIGS. 5 (A) to 5 (C)). )). When the rotation of the hollow pipe 10a is forward rotation, if the penetration speed is within 1 pitch of the blades per rotation of the hollow pipe 10a, the soil around the hollow pipe is affected by the pushing force of the inclined blades. It will be discharged to the surface of the earth. The penetration speed of the hollow tube 1 is preferably a constant speed. In the intrusion step of the hollow pipe 1, the soil around the hollow pipe is discharged to the ground surface, and a loose state or a muddy state 30a is formed around the hollow pipe. As a result, the displacement at the time of penetration becomes almost zero. Further, it is preferable that the volume of the soil 31a discharged to the ground surface is substantially the same as the volume of the hollow pipe intrusion and the volume of the soil discharged to the ground surface from the viewpoint of reducing the influence of displacement to the periphery at the time of penetration. In the process of penetrating the hollow pipe 1, the penetration of the hollow pipe 1 may be temporarily stopped in the process of penetrating the hollow pipe 1 from the ground surface into the ground, and the hollow pipe 1 may be pulled up. You may. Thereby, the amount of soil discharged can be controlled.

In the second embodiment, "relaxing" means that the sandy soil around the hollow pipe is inclined by the jet water or the fluidizing agent contained in the jet water to reduce the friction between the soil particles. It is the one that becomes uniform by the rotation of the blades and becomes fluidized. In addition, when the soil around the hollow pipe is viscous, the muddy water is similarly agitated uniformly and becomes a fluidized state. The fluidized state can also be grasped by hand and judged by experience. That is, when the loosened soil is grasped by hand, it has a fluidity such that it is pushed out from the grasped hand.

Next, a step of stopping the injection of jet water, pulling out the hollow pipe 1 to an appropriate length, discharging the sand pile material 19 in the hollow pipe 10a, and a step of punching back (re-penetrating) the hollow pipe 10a. The process of forming a compacted sand pile 42 in the soft ground is performed by repeating the above steps up to the ground surface (FIGS. 6A to 6D). The compaction sand pile construction process is the same as the conventional compaction sand pile construction process, and the backing may be performed by backing up the length according to the amount of the removed sand pile material by the control instrument. Further, in the compaction sand pile construction process, the soil in the loosened portion or the muddy portion is discharged to the ground surface due to the diameter-expanding pressure at the time of backing. In FIG. 6, reference numeral 32a is the discharged soil at the time of sand pile construction. In the step of discharging the sand pile material 19 in the hollow pipe 10a, the hollow pipe 1 may be either non-rotating or rotating. Further, also in the step of punching back (re-penetrating) the hollow tube 10a, the hollow tube 10a may be either non-rotating or rotating. In both the sand pile material discharge step and the backing step, the amount of discharged soil can be adjusted by rotating the hollow pipe 10a. If the amount of soil discharged is not as expected, such as when the amount of soil discharged is too large or too small, the amount of soil discharged can be adjusted by changing the rotation method of the hollow pipe 10a.

In the compaction sand pile construction step in the second embodiment, if the amount of soil discharged at the time of construction 32 and the amount of soil of the compaction sand pile (expanded diameter) are substantially the same, the displacement at the time of construction is , Can be almost zero. Further, when the amount of soil discharged at the time of construction 32 is smaller than the amount of soil of the compacted sand pile (expanded diameter), the displacement at the time of construction cannot be set to zero, but the conventional compacted sand pile is constructed. It can be reduced as compared with the process.

In the present invention, various modifications can be taken without being limited to the above-described embodiment. For example, the injection port 13 is installed at two locations in this example, but the present invention is not limited to this, and the injection port 13 may be installed at one location. Further, in the present invention, the "injection port" does not mean only an opening, but also means a short pipe having an opening at one end or a tip portion of a jet water injection pipe.

According to the present invention, the soil in the loosened portion or the muddy portion is discharged to the ground surface due to the diameter-expanding pressure at the time of impacting, and the diameter-expanded compacted sand is discharged to the loosened or muddy region. A pile is created. Therefore, it is possible to greatly suppress the transmission of displacement to the existing structure without providing a buffer zone between the ground improvement area and the existing structure.

10, 10a Hollow pipe for compaction sand pile construction 11 Hollow pipe body 12 Inclined blade 13 Injection port 14 Excavation bit 15 Rotating device 16 Forced lifting device 17 Hopper 19 Sand pile material 30, 30a Loose or muddy state Part 31, 31a Discharged soil at the time of intrusion 32, 32a Discharged muddy water at the time of construction

Claims (4)

Predetermined while rotating a hollow pipe filled with a sand pile material in which a spiral blade or an inclined blade having an inclined surface is formed on the outer peripheral surface of the hollow pipe body, and discharging the soil around the hollow pipe to the ground surface. Step I that penetrates to the depth of
The process of pulling out the hollow pipe to an appropriate length and discharging the sand pile material in the hollow pipe and the process of pushing back the hollow pipe are repeated in sequence until the ground surface is reached, and the sand pile is compacted in the soft ground. It is the process of creating II,
The step II is Ri step der to be carried out after said Step I,
Further, a method for creating a compacted sand pile, characterized in that the soil around the hollow pipe is discharged to the ground surface by the diameter-expanding pressure at the time of backing in the step of backing up the hollow pipe. The method for creating a compacted sand pile according to claim 1, further comprising forming an injection port for injecting jet water on the outer periphery of the hollow pipe or below the hollow pipe at the tip of the hollow pipe body. The method for creating a compacted sand pile according to claim 2, wherein the injection port is formed in the hollow pipe main body. The method for creating a compacted sand pile according to claim 1, wherein the radial length (blade diameter) of the spiral blade or the inclined blade is 1 to 0.7 times the diameter of the compacted sand pile.

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