JP2004190374A - Soft ground improving method and soft ground improving unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft ground improving method and a soft ground improving unit applicable to the soft ground improving method facilitating ground improvement under the bottom of water without leaving remaining materials such as drain materials in the ground after improved. <P>SOLUTION: In this soft ground improving method, a unit 10 integrally composed of a columnar member 12 with a drainage function, and a cover member 11 with a water permeating function at the inner surface upper part is installed so that the columnar member is positioned almost vertically in the ground 70 and that the cover member faces the ground surface 71, and negative pressure is applied to the ground surface from the cover member by a vacuum pump 81 connected to the unit, to eject water and air in the ground. The unit is removed after the improvement of the ground. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soft ground improvement method and a soft ground improvement unit for improving soft ground such as soft viscous ground.
[0002]
[Prior art]
Conventionally, when trying to reduce the volume and increase the strength of soft viscous ground, a vertical drain material is poured into the ground, a drainage path is secured with horizontal drainage material, etc. A method of promoting consolidation is often used. In this method, a plastic drain is often used as the drain material, and the drain material remains on the ground after the improvement, and thus there is a problem that it becomes an obstacle when excavating later.
[0003]
In addition, when consolidating the ground under the water bottom such as the seabed, lake bottom, and riverbed, a conventional vacuum consolidation method, for example, a method of covering the improved area with a sealing sheet after placing a vertical drain, is used. Under the bottom, it is very difficult work to secure a horizontal drainage path and apply a sealing sheet.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the related art, and has a soft ground improvement method capable of easily performing ground improvement under water without leaving residual materials such as drain materials on the ground after the improvement. And a soft ground improvement unit applicable to the soft ground improvement method.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the soft ground improvement method according to the present invention provides a unit in which a columnar member having a drainage function and a lid member having a water-permeable function on an inner surface are integrally formed with the columnar member in the ground. A step of installing the lid member so as to be substantially vertical and facing the ground surface, and applying a negative pressure to the ground surface from the lid member by a vacuum pump connected to the unit, thereby forming water in the ground. Discharging the air, and removing the unit after the ground has been improved.
[0006]
According to this soft ground improvement method, the unit is integrally provided with a columnar member having a drainage function and a lid member having a water-permeability function. ), And the ground can be easily improved even under the water. Further, since the integrated unit is removed by lifting or the like after the ground improvement, no residual material remains on the ground.
[0007]
In addition, a drainage pump may be installed in the vicinity of the underwater ground in a river, a lake, or a sea area instead of the vacuum pump, so that the pressure caused by the head difference caused by the drainage pump acts on the ground surface from the lid member. Thereby, the pressure due to the head difference caused by the drain pump acts on the ground surface, so that the consolidation of the ground can be promoted and the ground can be easily improved particularly at the original position under the water bottom.
[0008]
In this case, by further installing a vacuum pump so that the differential pressure between the reduced pressure by the vacuum pump and the atmospheric pressure acts on the ground surface from the lid member, it is possible to further promote the consolidation of the ground. It should be noted that the vacuum pump and the drainage pump can be operated simultaneously, or the drainage pump alone can be operated so as to be appropriately selected according to the situation of the ground improvement work.
[0009]
In addition, when the unit is removed, the unit is easily removed by injecting air from outside into the unit. In this case, air from the outside is pressed into the ground surface and the ground through the cover member and the columnar member of the unit.
[0010]
Further, the columnar member may be a steel pipe to which a drain material is attached, and the columnar member may be a pipe having a water collecting hole or a pipe having a mesh structure.
[0011]
The lid member may include a steel lid and a skirt, and the unit may be installed such that the skirt is positioned in the ground when the unit is installed. Further, since the lid member includes a steel frame member and a resin-based material or a sealing sheet material attached to the frame member, a structure having a higher sealing effect can be achieved.
[0012]
In addition, it is preferable that the columnar member has a structure capable of expanding and contracting, whereby the columnar member can expand and contract to follow the settlement of the ground, and the settlement following ability can be improved. In addition, it is preferable that the unit includes a plurality of the columnar members, and a horizontal drain member is arranged in a horizontal direction near the lid member of the plurality of columnar members. Thereby, a horizontal drainage path can be easily secured even under the water bottom.
[0013]
The soft ground improvement unit according to the present invention is configured such that a columnar member having a drainage function and a lid member having a water permeable function are integrally formed at an upper portion of the inner surface, and the columnar member is located substantially vertically in the ground, and an inner surface of the lid member is provided. Can be installed so as to face the ground surface and can be integrally removed after the ground is improved.
[0014]
According to this soft ground improvement unit, the columnar member and the cover member are integrally formed, so that the unit can be easily installed on the ground and can be easily removed, and the unit can be removed after the ground has been improved. No wood remains. In addition, the unit after removal can be reused, and the unit can be used efficiently. Preferably, a plurality of columnar members are provided.
[0015]
It is preferable that the unit has a suction port that can be connected to a pipe in which the lid member is connected to an external vacuum pump or a drain pump. Decompression and drainage by a vacuum pump or a drainage pump can be performed through the suction port. In addition, as described above, air can be injected from outside when the unit is removed through the suction port.
[0016]
The columnar member may include a steel pipe having a drain material attached to an outer peripheral surface thereof. Further, the columnar member may include a pipe having a water collecting hole or a pipe having a mesh structure.
[0017]
Preferably, the lid member includes a steel lid and a skirt. When the unit is installed, the skirt is located in the ground. In addition, since the lid member includes a steel frame member and a resin-based plate member or a sealing sheet member attached to the frame member, the weight of the unit can be reduced. In addition, it is preferable that the columnar member has a structure capable of expanding and contracting, whereby the columnar member can expand and contract to follow the settlement of the ground, and the settlement following ability can be improved.
[0018]
The soft ground improvement unit can be used as a unit in the soft ground improvement method described above.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the soft ground improvement unit according to the present embodiment and the installation process thereof will be described with reference to the drawings.
[0020]
<Soft ground improvement unit>
[0021]
FIG. 1 is a side view of a soft ground improvement unit according to an embodiment of the present invention, FIG. 2 is a partial side sectional view of the soft ground improvement unit of FIG. 1, and FIG. 3 is a view of the soft ground improvement unit of FIG. It is a top view. FIG. 4 is a longitudinal sectional view (a) and an enlarged transverse sectional view (b) of the steel pipe pile of FIG. 1.
[0022]
As shown in FIGS. 1 to 3, a soft ground improvement unit (hereinafter, “unit”) 10 includes a plurality of steel pipe piles 12 each having a drain member 12 a attached to an outer peripheral surface thereof, and each steel pipe pile 12 being attached. And a cover member 11 configured integrally with each steel pipe pile 12.
[0023]
As shown in FIG. 3, the lid member 11 has a substantially square square planar shape, and is provided so as to protrude downward from the outer periphery of the lid portion 13, which is made of a steel plate member having a substantially square shape. And a skirt portion 14 made of steel, and an upper portion of the lid portion 13 is made of a structural steel such as an H-shaped steel. As shown in FIG. 3, the steel pipe piles 12 are attached to the lid 13 at substantially equal intervals so as to be arranged in three rows and three rows in a plane, and an external vacuum pump or the like is provided near the diagonal center. Is provided with a pipe-shaped suction port 16 which can be connected to a pipe connected to the pipe. The suction port 16 penetrates through the lid 13 and opens on the inner surface 13 a of the lid 13.
[0024]
As shown in FIGS. 4 (a) and 4 (b), the steel pipe pile 12 has a plurality of plastic board drain members 12a formed of a long plate material on the outer peripheral surface of a long cylindrical steel pipe so as to extend in the longitudinal direction of the steel pipe. Installed. As shown in FIG. 4B, a plurality of plastic board drain members 12a are attached to the outer peripheral surface of the steel pipe at substantially equal intervals. The tip 12b of each steel pipe pile 12 is pointed in a conical shape so that the unit 10 can be easily installed on the ground.
[0025]
As shown in FIGS. 1 and 2, a nonwoven fabric 15 is disposed as a horizontal drain material on the inner surface 13 a of the lid 13 of the unit 10, and the plastic board drain materials 12 a of the plurality of steel pipe piles 12 are horizontally positioned at the top. It is connected so that it can be drained.
[0026]
<Unit installation and removal process on land>
[0027]
Next, with reference to FIG. 5, a process until the soft ground improvement unit is installed on the ground on the ground to be improved and removed is described with reference to FIGS. 1 to 4. FIG. 5 is a diagram showing each of the steps (a) to (d) when the ground on land is an object of improvement.
[0028]
First, using the crane 80, the unit 10 of FIGS. 1 to 3 described above (however, the number of the steel pipe piles 12 is increased) is lifted and placed on the soft ground 70 such as the soft viscous ground to be ground improved. After being moved, the steel pipe pile 12 of the unit 10 is pressed into the ground surface 71 of the soft ground 70 by its own weight from the tip and installed (a). In this manner, the required number of units 10 are installed, and the respective steel pipe piles 12 are vertically positioned in the ground 70, so that a vertical drainage path is formed in the ground 70. At this time, after the inner surface 13a of the lid portion 13 of the unit 10 is grounded, the following steps (b) and (c) may be performed, and the lid member 11 may be press-fitted together with suction. In addition, since the nonwoven fabric 15 of the horizontal drain material is attached to the unit 10 side as shown in FIGS. 1 and 2, a horizontal drainage path is formed by installing the unit 10.
[0029]
Next, a water distribution pipe 82 is connected to the suction port 16 of the lid member 11 of each unit 10, and the water distribution pipe 82 is connected to a vacuum pump 81 and a drainage tank (not shown) (b).
[0030]
Next, when the vacuum pump 81 is operated, water and air in the ground 70 discharged to the inner surface 13a of the lid 13 of the unit 10 through the plastic board drain material 12a of each steel pipe pile 12 and the nonwoven fabric 15 of the horizontal drain material are discharged. The water is discharged to an external drain tank via the suction port 16 and the water distribution pipe 82. Thereby, the consolidation of the ground 70 is promoted, and the ground in the ground 70 is improved (c). Since the skirt portion 14 of the lid member 11 is located between the upper part of the steel pipe pile 12 and the ground surface 71, it is possible to prevent air from being sucked from the surrounding ground surface during compaction by vacuum suction.
After this ground improvement, the entire unit 10 is removed from the improved ground 72 by lifting the unit 10 using the crane 80 (d). When the unit 10 is removed, a compressor (not shown) or the like is connected to the water distribution pipe 82, and air is press-fitted from the suction port 16 of each unit 10 to the inner surface 13a of the lid 13 and the drain material 12a. 10 can be easily removed.
[0032]
As described above, according to the soft ground improvement method of FIG. 5, the unit 10 includes the steel pipe pile 12 and the cover member 11 integrally, and there is no need to separately install the steel pipe pile and the cover member. Since it can be installed integrally as 10, there is no need to cover the improved area with a sealing sheet, and installation on the land 70 on land to be improved can be easily performed. Further, the integrated unit 10 is removed by lifting after the ground improvement, and no residual material such as drain material remains on the ground 72 after the improvement, so that there is no obstacle to performing excavation or the like later. Also, since the horizontal drain material (nonwoven fabric 15) can be attached to the unit 10 and integrated therewith, the installation is easy, the horizontal drainage path can be easily secured, and the removal can also be integrated, so that the nonwoven fabric 15 is also attached to the ground surface 71. Will not remain.
[0033]
<Installation and removal process of units on the ground where water drops>
[0034]
Next, referring to FIG. 6, a process until the soft ground improvement unit is installed on the soft ground such as the soft viscous ground to be ground-improved under the seabed, the lake bottom, and the riverbed such as a seabed, a lake bottom, and a riverbed and removed is shown in FIGS. 1 to 4. It will be described with reference to FIG. FIG. 6 is a diagram showing each of the steps (a) to (d) when the ground under the water bottom is targeted for improvement.
[0035]
First, using the hoist ship 90, the unit 10 of FIGS. 1 to 3 described above (however, the number of the steel pipe piles 12 is increased) is lifted and immersed in water 75, and the steel pipe piles 12 of the unit 10 are removed. The tip of the unit 10 is press-fitted into the ground surface 77 of the soft ground 76 with its own weight and installed (a). In this way, a required number of units 10 are installed, and each steel pipe pile 12 is vertically positioned in the ground 76, so that a vertical drainage path is formed in the ground 76. At this time, after the inner surface 13a of the lid portion 13 of the unit 10 is grounded, the following steps (b) and (c) may be performed, and the lid member 11 may be press-fitted together with suction. In addition, since the nonwoven fabric 15 of the horizontal drain material is attached to the unit 10 side as shown in FIGS. 1 and 2, a horizontal drainage path is formed by installing the unit 10.
[0036]
After installing the unit 10 on the soft ground 76 under the water bottom as described above, the underwater vacuum pump 85 is installed by the hoist ship 90, and the water distribution pipe 86 to the suction port 16 of each unit 10 is provided by diving work. (B).
[0037]
Next, when the underwater vacuum pump 85 is operated, water and air in the ground 76 discharged to the inner surface 13a of the cover 13 of the unit 10 through the plastic board drain material 12a of each steel pipe pile 12 and the nonwoven fabric 15 of the horizontal drain material are discharged. It is discharged through each suction port 16 and the water pipe 86. Thereby, the consolidation of the ground 76 is promoted, and the ground is improved in the ground 76 (c).
[0038]
After the ground improvement, the entire unit 10 is removed from the improved ground 78 by lifting the unit 10 using the hoist ship 90 (d). When the unit 10 is removed, a compressor (not shown) or the like is connected to the water distribution pipe 86, and air is press-fitted from the suction port 16 of each unit 10 to the inner surface 13a of the lid 13 and the drain material 12a. 10 can be easily removed.
[0039]
As described above, according to the soft ground improvement method of FIG. 6, the unit 10 integrally includes the steel pipe pile 12 and the cover member 11, and separates the steel pipe pile and the cover member from the underwater ground to be improved. And the unit 10 can be installed integrally as a unit 10. Therefore, there is no need to cover the improved area under the water bottom with a sealing sheet, and installation on the ground under the water bottom can be easily performed. In addition, the integrated unit 10 is removed by lifting after the ground improvement, and no residual material such as a drain material remains on the ground 78 after the improvement, so that there is no obstacle to performing excavation or the like later. In addition, since the horizontal drain material (nonwoven fabric 15) can also be integrally attached to the unit 10, it can be easily installed under the water bottom, and a horizontal drainage path can be easily secured. It does not remain on the ground surface 77.
[0040]
Next, a modified example of the method of improving the ground under the water will be described with reference to FIG. FIG. 7 is a diagram for explaining another example of the ground improvement process under the water floor.
[0041]
The subsurface improvement process of FIG. 7 is such that both the pressure due to the pressure difference from the atmospheric pressure due to the decompression of the vacuum pump and the pressure due to the head difference due to the lowering of the water level act as a load on the subsurface underground to be improved. It was done.
[0042]
That is, as shown in FIG. 7, a pumping well 87 composed of a sealed tank is installed on a ground surface 77 below the water bottom, and a submersible drainage pump 79 connected to a water distribution pipe 86 connected to the suction port 16 of each unit 10. Is installed at the bottom of the pumping well 87, and a vacuum pump 88 is connected to the top. By discharging the water inside the pumping well 87 to the outside through the water distribution pipe 89 by the submersible drainage pump 79 and lowering the water level in the pumping well 87, the pressure due to the head difference Δh due to the lowering of the water level causes the pressure from the lid 13 of the unit 10 to reach the ground. Join 76. Further, by reducing the pressure inside the pumping well 87 by the vacuum pump 88, a differential pressure between the atmospheric pressure and the pressure in the pumping well 87 is applied to the ground 76 from the lid 13. As described above, both the pressure due to the pressure difference from the atmospheric pressure and the pressure due to the head difference due to the decrease in the water level are applied to the ground 76 as a load, whereby a greater consolidation promoting effect can be obtained.
[0043]
In FIG. 7, by opening the upper end 87 a of the pumping well 87 and lowering the water level in the pumping well 87 by the submersible drainage pump 79, only the pressure due to the head difference due to the lowering of the water level moves from the cover 13 of the unit 10 to the ground. 76 may be added. In this case, as shown in FIG. 7, the vacuum pump 88 and the drainage pump 79 are simultaneously operated, or the upper end 87a is opened to switch only the drainage pump 79 to operate, so that the construction can be changed according to the construction conditions. Thus, two operation states can be appropriately selected.
[0044]
<Stretchable structure in the ground of steel pipe pile>
[0045]
Next, a structure in which a steel pipe pile of a unit installed on the ground is expandable and contractable so as to follow the settlement of the ground will be described with reference to FIGS. FIG. 8 is a partial side sectional view showing a telescopic structure of a steel pipe pile provided in the unit shown in FIGS. 1 to 3, and FIG. 9 is a diagram showing each step of construction and following settlement of the unit having the telescopic structure of FIG. It is process drawing which shows (a) thru | or (g).
[0046]
As shown in FIG. 8, the unit 10 has a sheath pipe 17 which is installed so as to penetrate the lid 13 and has a flange 17 a at an upper part and an external thread part at a lower end side for each position of each steel pipe pile 12. It further comprises a spacer tube 18 having a blind flange 18a at the top and a blind flange 19. In this case, each of the steel pipe piles 12 has an outer diameter smaller than the inner diameter of the sheath pipe 17, and has an inner thread portion that engages with the thread portion of the spacer tube 18 at the upper portion.
[0047]
The installation process of the unit 10 as shown in FIG. 8 will be described with reference to FIG. First, the spacer pipe 18 is screwed into the inner thread portion on the upper part of the steel pipe pile 12, the steel pipe pile 12 is inserted into the sheath pipe 17, and the three flanges 17a, 18a, 19 are bolted (a).
[0048]
5 or 6, the steel pipe pile 12 penetrates from the ground surface 71 into the ground in the same manner as in the unit 10 having the above-described structure (b).
[0049]
Next, the spacer tube 18 is removed, and a blind flange 19 is attached to the flange 17a of the sheath tube 17 (c).
[0050]
When negative pressure loading is started from the ground surface 71 as shown in FIGS. 5 to 7, the unit 10 sinks with the lid 13 and the like as the surrounding ground sinks. At this time, the steel pipe pile 12 is attached to the spacer pipe. Since the unit 10 moves upward by the removed stroke 18 and moves as if it contracts, the unit 10 can follow the settlement of the ground, and the settlement followability is improved (d). Further, since the steel pipe pile 12 is moved by the stroke of the spacer pipe 18, the drainage can be performed in the same manner.
[0051]
After the completion of the negative pressure loading, the blind flange 19 is removed, and the spacer pipe 18 is screwed into the upper portion of the steel pipe pile 12 again (e).
[0052]
Next, when the unit 10 is lifted upward for removal, the steel pipe pile 12 is likely to be left due to peripheral resistance in the ground, but the flange 17a of the sheath 17 of the unit 10 is integrated with the steel pipe pile 12. The flange 18a of the spacer tube 18 contacts the flange 18a, and the flange 18a serves as a stopper, and is lifted integrally with the unit 10 (f).
[0053]
When the unit 10 is further lifted, the unit 10 is separated from the ground surface 71 together with the steel pipe pile 12 to be collected and removed (g).
[0054]
<Modified example of unit>
[0055]
Next, modified examples of the units shown in FIGS. 1 to 3 will be described with reference to FIGS. FIG. 10 is a perspective view showing the appearance of a frame member and the like of the unit 20 of the modification, FIG. 11 is a plan view, FIG. 12 is a side view, and FIG. 13 is a partial cross-sectional view.
[0056]
As shown in FIGS. 10 to 13, the unit 20 includes a steel frame member 21 having a framework structure. The frame member 21 is arranged on a plurality of beam members 21a made of an I-beam or the like, a plurality of beam members 21b made of an I-beam or the like arranged so as to be orthogonal to the plurality of beam members 21a, and an upper peripheral side surface. An upper frame 21c, a lower frame 21d disposed on the lower peripheral side surface, and legs 21e connecting the upper frame 21c and the lower frame 21d at four corners are provided.
[0057]
The unit 20 further includes a plurality of steel pipe piles 23 arranged at the intersections of the beams 21a and 21b, and a resin-based plate material 22 attached to the inner surface side of the frame member 21 so as to cover the entire frame member 21. And. The frame member 21 as shown in FIG. 10 forms a lid member similar to FIGS. 1 to 3 by attaching the resin-based plate member 22.
[0058]
A plastic board drain material 23a is attached to the steel pipe pile 23 as in FIGS. In order to connect the drain members 23a of the steel pipe piles 23 in the horizontal direction, a non-woven fabric 15 of a horizontal drain member is arranged in the same manner as in FIGS. Also, a steel plate 27 is attached to a part of the resin-based plate 22 on the upper surface side instead of the resin-based plate 22, and the steel plate 27 is provided with a suction port 26 connected to a vacuum pump or the like. The consolidation of the ground can be similarly promoted by installing the unit 20 on the ground to be improved and performing vacuum suction or the like from the suction port 26.
[0059]
According to the unit 20 of FIG. 10, the same effects as those of the units of FIGS. 1 to 3 can be obtained, and since the resin-based plate 22 is attached to the frame member 21, the unit is configured to be lighter. Yes, it is preferable. Note that a sheet material may be attached instead of the resin-based plate material 22. Further, as shown in FIG. 13, the resin-based plate or sheet material adhered between the upper frame 21c and the lower frame 21d around the side surface of the frame member 21 is adhered to the inner surfaces of the upper frame 21c and the lower frame 21d. However, it may be attached to the outer surface side.
[0060]
<Modified example of steel pipe pile (drain material)>
[0061]
Next, a modified example of the steel pipe pile having the drain function in FIG. 4 will be described with reference to FIGS. FIG. 14A is a diagram illustrating a steel pipe pile having a plurality of water collecting holes formed on an outer peripheral surface, and FIG. 14B is a diagram illustrating a steel pipe pile having an outer peripheral surface having a mesh structure.
[0062]
The steel pipe pile 24 of FIG. 14A has a large number of holes 24a formed from the upper end to the lower end on the entire outer peripheral surface thereof, and these holes 24a are used as water collecting holes. The steel pipe pile 25 of FIG. 14B has a mesh structure from the upper end to the lower end on the entire outer peripheral surface.
[0063]
The steel pipe piles 24 and 25 are provided with a fiber drain material using a natural fiber and a nonwoven fabric inside the steel pipe in order to further guide water guided through a water collecting hole or a mesh when installed in the ground to the upper end of the steel pipe. It is filled with a known drainage material such as a drain material having a combined water permeability function. In addition, when the water level inside the steel pipe piles 24 and 25 rises when installed on the ground, these drainage materials may be omitted.
[0064]
As described above, according to the soft ground improvement method of the present embodiment, a plurality of steel pipe piles having a drainage function and a water-permeable function are provided on the upper inner surface in improving soft viscous ground on land or below the water floor. Install the unit with the lid member on the ground to be improved, promote the consolidation by the action of negative pressure by the vacuum pump, etc., and remove the unit after the improvement, so that drain etc. It is possible to easily improve the ground without leaving any residue and under the water.
[0065]
As described above, the present invention has been described with the embodiments, but the present invention is not limited to these, and various modifications can be made within the technical idea of the present invention. For example, it is a matter of course that the number and arrangement of the steel pipe piles 12 and 23 in the unit 10 of FIGS. 1 to 3 and the unit 20 of FIG. 10 can be appropriately changed. Further, each of the steel pipe piles 12, 23, 24 and 25 is not limited to a circular cross section, but may be a polygon such as a quadrangle.
[0066]
【The invention's effect】
According to the present invention, it is applied to a soft ground improvement method capable of easily performing soil improvement under the water bottom without leaving residual materials such as drain materials on the improved ground, and a soft ground improvement method thereof. A possible soft ground improvement unit can be provided.
[Brief description of the drawings]
FIG. 1 is a side view of a soft ground improvement unit according to the present embodiment.
FIG. 2 is a partial side sectional view of the soft ground improvement unit of FIG.
FIG. 3 is a plan view of the soft ground improvement unit of FIG. 1;
FIG. 4 is a longitudinal sectional view (a) and an enlarged transverse sectional view (b) of the steel pipe pile of FIG.
FIG. 5 is a diagram showing each step (a) to (d) in a case where land on the ground is to be improved in the soft ground improvement method according to the present embodiment.
FIG. 6 is a view showing each step (a) to (d) when the ground under the water bottom is targeted for improvement in the soft ground improvement method according to the present embodiment.
FIG. 7 is a view for explaining another example of the ground improvement process under the water floor in FIG. 6 (c).
FIG. 8 is a partial side sectional view showing a telescopic structure of a steel pipe pile provided in the unit shown in FIGS.
FIG. 9 is a process diagram showing each of the steps (a) to (g) of construction and settlement following of the unit having the elastic structure of FIG.
FIG. 10 is a perspective view showing an appearance of a frame member and the like of a unit 20 of a modified example of FIGS.
FIG. 11 is a plan view of the unit of FIG. 10;
FIG. 12 is a side view of the unit of FIG. 10;
FIG. 13 is a partial cross-sectional view taken along line XIII-XIII shown by a broken line in FIG.
FIG. 14 (a) is a diagram showing a steel pipe pile having a large number of water collecting holes formed on an outer peripheral surface, and FIG. 14 (b) is a diagram showing a steel pipe pile having an outer peripheral surface having a mesh structure.
[Explanation of symbols]
10, 20 units, soft ground improvement unit 11 lid member 12, 23 steel pipe pile (columnar member)
24,25 steel pipe pile (columnar member)
12a Drain material 13 Lid portion 14 Skirt portion 15 Non-woven fabric, horizontal drain material 16 Suction port 17 Sheath tube 18 Spacer tube 19 Blind flange 21 Frame member 22 Resin-based plate material 23 Steel pipe pile 70, 76 Ground 71, 77 Ground surface 81 Vacuum pump 82 Water distribution pipe 85 Submersible vacuum pump 86 Water distribution pipe 79 Submersible drainage pump 87 Pumping well 88 Vacuum pump

Claims (18)

A unit in which a columnar member having a drainage function and a lid member having a water-permeability function are integrally formed at the upper part of the inner surface is arranged such that the columnar member is located almost vertically in the ground, and the inner surface of the lid member faces the ground surface. The process of installing the
Draining water and air in the ground by applying a negative pressure to the ground surface from the lid member by a vacuum pump connected to the unit;
Removing the unit after the ground is improved. A drain pump is installed instead of the vacuum pump in the vicinity of the bottom of the water in a river, a lake or a sea area, and the pressure caused by the head difference caused by the drain pump acts on the ground surface from the lid member. The soft ground improvement method according to claim 1. The soft ground improvement method according to claim 2, wherein a vacuum pump is further provided, and a differential pressure between the reduced pressure by the vacuum pump and the atmospheric pressure is applied to the ground surface from the lid member. The soft ground improvement method according to claim 1, 2, or 3, wherein air is externally injected into the unit when the unit is removed. The soft ground improvement method according to any one of claims 1 to 4, wherein the columnar member is a steel pipe having a drain material attached to an outer peripheral surface thereof. The soft ground improvement method according to any one of claims 1 to 4, wherein the columnar member is a pipe having a water collecting hole or a pipe having a mesh structure. The soft member according to any one of claims 1 to 6, wherein the cover member includes a steel cover portion and a skirt portion, and the skirt portion is located in the ground when the unit is installed. Ground improvement method. The soft ground improvement method according to any one of claims 1 to 6, wherein the lid member includes a steel frame member and a resin-based plate material or a sealing sheet material attached to the frame member. . The soft ground improvement method according to any one of claims 1 to 8, wherein the unit has a structure in which the columnar member can expand and contract. The soft unit according to any one of claims 1 to 9, wherein the unit includes a plurality of the columnar members, and a horizontal drain member is arranged in a horizontal direction near the lid member of the plurality of columnar members. Ground improvement method. A columnar member having a drainage function and a lid member having a water-permeability function are integrally formed at the upper part of the inner surface, and the columnar member is located substantially vertically in the ground, and is installed such that the inner surface of the lid member faces the ground surface. A soft ground improvement unit characterized in that it is possible and can be integrally removed after the ground improvement. The soft ground improvement unit according to claim 11, wherein the lid member has a suction port that can be connected to a pipe connected to an external vacuum pump or a drain pump. The soft ground improvement unit according to claim 11, wherein the columnar member includes a steel pipe having a drain material attached to an outer peripheral surface thereof. The soft ground improvement unit according to claim 11, wherein the columnar member includes a pipe having a water collecting hole or a pipe having a mesh structure. The soft ground improvement unit according to any one of claims 11 to 14, wherein the lid member includes a steel lid and a skirt. The soft ground improvement unit according to any one of claims 11 to 15, wherein the lid member includes a frame member made of steel and a resin-based plate member or a sealing sheet member attached to the frame member. . The soft ground improvement unit according to any one of claims 11 to 16, wherein the columnar member has a structure capable of expanding and contracting. The soft ground improvement method according to any one of claims 1 to 10, wherein the soft ground improvement unit according to any one of claims 11 to 17 is used.

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