JP6798845B2 - 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 the displacement generated due to the diameter expansion during compaction, and a method for forming a compacted sand pile using the hollow pipe.

Conventionally, as shown in FIGS. 7 and 8, ground improvement sand for improving the ground by placing compacted sand piles 82 in soft ground A such as loose sandy ground or highly hydrous 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. 8) generated by the diameter expansion during compaction is the above-ground structure 92 close to the ground improvement area 95, natural objects such as trees 93. , 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 so as to absorb the displacement Z (91a in FIG. 8).

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 for empty digging for displacement reduction measures require predetermined sizes and shapes 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 cushioning 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 a buffer zone area 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. It is an object of the present invention 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 is stirred at the tip of the hollow pipe body. Provided is a hollow pipe for forming a compacted sand pile, characterized in that a blade and an injection port for injecting jet water around the hollow pipe are formed respectively.

Further, the present invention provides the hollow pipe for forming a compacted sand pile, characterized in that the injection port is formed on the stirring blade.

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 comprises a step of injecting jet water from the injection port while rotating the hollow tube and penetrating to a predetermined depth while loosening or muddying the circumference of the hollow tube and jetting jet water. Is stopped, the hollow pipe is pulled out to an appropriate length, and the step of discharging the sand pile material in the hollow pipe and the step of pushing back the hollow pipe are sequentially repeated until the ground surface is reached, and the sand pile material is tightened in the soft ground. Provided is a method for forming a compacted sand pile, which comprises performing a step of forming a compacted sand pile.

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 embodiment of this invention. It is an enlarged view of the tip part of the hollow pipe for making a 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 embodiment of this invention. It is a figure explaining the compaction process of the compaction sand pile construction method of FIG. 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 embodiment of the present invention will be described with reference to FIGS. 1 to 4. The hollow pipe 1 is a conventional hollow pipe for forming a compacted sand pile, and has a stirring blade 12 at the tip of the hollow pipe main body 11 on the soil penetration side and an injection port 13 for injecting jet water around the hollow pipe. And are formed respectively. 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 stirring blade 12 is not particularly limited as long as it stirs around the hollow tube when the hollow tube 1 penetrates. In this example, the stirring blades 12 are a pair of left and right stirring blades, have a predetermined length, and the surface in the rotation direction at the time of penetration is an inclined surface facing diagonally upward. As a result, the hollow pipe 1 easily penetrates into the ground, and the agitation efficiency of the soil around the hollow pipe is improved. The stirring blade 12 may be single-stage or multi-stage. Further, an excavation bit may be formed at the tip of the stirring blade 12 in the rotation direction at the time of penetration. The total length (blade diameter) l ₁ of the stirring blade 12 may be about 1 to 0.7 times the compaction sand pile diameter l ₂ . If the total length (blade diameter) l ₁ of the stirring blade 12 is the same as the compaction sand pile diameter l ₂ , the compaction sand pile 42 will be formed in the loosening region or the muddy water region around the hollow pipe. , 100% replacement. In this case, the displacement transmission to the existing structure can be made almost zero. On the other hand, if the total length (blade diameter) l _{1 of} the stirring blade 12 is less than 1 of the compacted sand pile diameter l ₂ and 0.7 or more, the loose area around the hollow pipe or the surrounding ground around the muddy water area is slightly removed. The sand pile 42 is formed by pushing it open, and the displacement transmission to the existing structure cannot be set to zero, but it is suppressed as compared with the conventional case. In the present specification, the term "loose state around the hollow pipe" is used for sandy land, and the term "muddy state around the hollow pipe" is used for viscous ground. Is the wording used.

The injection port 13 is an opening for injecting jet water around 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 1, 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 the hollow pipe 1 or the stirring blade 12. The injection direction of the jet water emitted from the injection port 13 may be either a rotation direction or a counter-rotation direction, but it is preferable to inject the jet water in the rotation direction from the viewpoint that a uniform loose state or a muddy water state can be obtained efficiently. .. In this example, the injection port 13 is installed on the surface of the stirring blade 12 located in the rotation direction at the time of penetration of the hollow pipe 1 so as to face in the rotation direction and in the substantially horizontal direction. That is, a pair of injection ports 13 are formed in the pair of stirring blades 12. As a result, when the hollow pipe 1 penetrates, jet water can be sprayed around the hollow pipe and on the earth and sand in front of the stirring blade 12.

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 loosen the soil around the hollow pipe by using it on soft ground of sandy soil system. 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 in the stirring blade 12, and is appropriately determined according to the soil quality of the soft ground, the length of the stirring blade 12, and the like.

The excavation bit 14 is an arbitrary component, and when the hollow pipe 1 penetrates, the earth and sand around the hollow pipe is excavated to facilitate the penetration of the hollow pipe 1. In this example, the excavation bit 14 has a pair of bits formed at the tip of the hollow pipe 1 at a position 90 degrees out of phase with the stirring blade 12 in a plan view.

Next, a method for forming a compacted sand pile using the hollow pipe 10 will be described with reference to FIGS. 5 and 6. First, the hollow tube 1 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 1 in the forward direction, 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. 5A to 5A). C)). 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 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 penetration 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 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 present invention, "relaxing" means that the sandy soil around the hollow pipe is made uniform by the rotation of the stirring blade, in which the friction between the soil particles is reduced by the jet water or the fluidizing agent contained in the jet water. It is said that it has become fluidized. In addition, muddy water means that when the soil around the hollow pipe is viscous, it is similarly agitated uniformly and becomes fluidized. The fluidized state can also be grasped by hand and judged by experience. That is, when the loosened soil is gripped by hand, it has a fluidity that is pushed out from the gripped 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 1, and a step of punching back (re-penetrating) the hollow pipe 1. The steps of forming a compacted sand pile 42 in the soft ground are carried out in sequence until the ground surface is reached (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 32 is the discharged soil at the time of sand pile construction.

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. .. In addition, if the amount of soil discharged during construction 32 is smaller than the amount of soil in the compacted sand pile (expanded diameter), the displacement during construction cannot be 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 ports 13 are installed at two locations in this example, but the present invention is not limited to this, and the injection ports 13 may be installed at one location on one of the pair of stirring blades. 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 into 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.

1 Hollow pipe 10 Compaction sand pile construction device 12 Stirring blade 13 Injection port 14 Excavation bit 15 Rotating device 16 Forced lifting device 17 Hopper 19 Sand pile material 30 Loose or muddy state part 31 Discharged soil at the time of penetration 32 Muddy water discharged during construction

Claims (4)

While rotating a hollow tube in which a stirring blade and an injection port for injecting jet water around the hollow tube are formed at the tip of the hollow tube body, jet water is injected from the injection port to make the hollow tube hollow. Step I that loosens or muddy the area around the pipe and penetrates to a predetermined depth while discharging the soil around the hollow pipe to the ground surface .
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 ground surface is softened. There rows and II processes which construct a compaction Sunakui in ground, in enlarged pressure during the return strike of the step II, compaction, characterized in that discharging the loose or slurried the soil surface Sand pile construction method. The method for creating a compacted sand pile according to claim 1, wherein the injection port is formed on the stirring blade. The compaction sand pile forming method according to claim 1 or 2, wherein the jet water ejected from the injection port is in the rotation direction or the counter-rotation direction of the hollow pipe . The method for creating a compacted sand pile according to any one of claims 1 to 3, wherein the total length (blade diameter) of the stirring blade is less than 1 and 0.7 or more of the compacted sand pile diameter. ..

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