JP2007278008A - Improving method for soft ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improving method for a soft ground capable of freely controlling a loading pressure on the ground, capable of efficiently discharging water and air contained in the soft ground surely and being effectively used even as a measure against residual-settlement in place of a bank for increasing the bearing capacity of the ground after soil improving. <P>SOLUTION: In the improving method for the soft ground, the top face of improving soil A is covered with airtight sheets 21 fixing sheet terminals into the peripheral sections B of the improved soil, and a decompression region separated from the improved-soil peripheral section B is made in the improving soil A by loading a vacuum pressure under the airtight sheets 21, and pore water in the improving soil A is discharged to improve the improving soil A to a hard ground. In the improving method for the soft ground, the airtight sheets 21 have a double structure composed of upper sheets 22 and lower sheets 23. In the improving method for the soft ground, a fluid is injected into openings 24 among the upper sheets 22 and lower sheets 23 under the state, in which the bulging of the upper sheets 22 of the airtight sheets 21 are suppressed, and only the lower sheets 23 are made to bulge and the improving soil A is pressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a soft ground improvement method suitable for soft ground such as a landfill construction area around a lake. In detail, it is related with the improvement method of the soft ground which can suppress effectively the fall of the groundwater around the improved ground accompanying the improvement of the soft ground.

  Conventionally, as an improved construction method for soft ground, the upper surface of soft ground to be improved (hereinafter referred to as improved ground) is covered with an airtight sheet, and a vacuum pressure is applied to the improved ground. There is one in which a soft ground is improved to a hard ground by creating an isolated pressure-reduced region and embankment on the soft ground and applying a compacted load of the embankment.

  Specifically, as shown in FIG. 5, the vertical drain material 1 is placed in the improved ground A at a predetermined interval, and then horizontally so as to contact the upper end portion 1 a of each vertical drain material 1. A drain 2 is disposed, and then a water collecting pipe 3 connected to a vacuum pump 5 is connected to the horizontal drain material 2 via a vacuum tank 4, and the upper surface 1 a of the vertical drain material 1 is further extended to the upper surface of the improved ground A. The material 2 and the water collecting pipe 3 are covered with an airtight sheet 7. Thereafter, the vacuum pump 5 connected to the water collecting pipe 3 through the vacuum tank 4 is operated.

  As a result, the vacuum pressure from the vacuum pump 5 propagates to the improved ground A via the horizontal drain material 2 and the vertical drain material 1, and the surrounding ground around the vertical drain material 1 is in a reduced pressure region (hereinafter referred to as “the lower ground”). Referred to as a reduced pressure region).

  The vacuum pressure propagates from the ground around the vertical drain material 1 that has become the decompression region to the ground around the outside, and as a result, the ground pressure (water pressure, earth pressure) toward the vertical drain material 1 is increased. appear.

  In accordance with this ground pressurization, pore water contained in the ground around the vertical drain material 1 is sucked out toward the vertical drain material 1 and drained by using the vertical drain material 1, the horizontal drain material 2 and the water collecting pipe 3 as a drainage path, Along with this, the ground around the outside of the ground around the vertical drain material 1 also becomes a decompression region.

  Thus, the decompression region spreads around the vertical drain material 1 and the surrounding ground extends, and the entire improved ground A eventually becomes the decompression region. At the same time, the consolidation and strength increase proceed with the vertical drain material 1 as the center. The whole area is consolidated and the strength is increased.

  As described above, while the hard ground is improved, the embankment 6 is applied on the airtight sheet 7, so that the improved ground A is consolidated and dewatered by the compacting load of the embankment 6. The consolidation settlement of the improved ground A is promoted in cooperation with the suction by (see Patent Document 1).

Structures such as buildings, factories, and roads are constructed on the soft ground after the improvement in this way, but by constructing these structures on the improved ground, the improved ground is improved by the load of the structure. Since the subsidence proceeds (residual subsidence), a load (banking) higher than the load of the structure is loaded on the improved ground to increase the supporting force of the improved ground.
Japanese Patent No. 3270968 (refer to claims 1 and 2 and FIG. 7)

  However, in order to apply the embankment to load the load on the improved ground, much labor and cost are required for bringing in and taking out the earth and sand as the material for loading. In addition, it is difficult to accurately apply the embankment that corresponds to the load of the structure constructed on the improved ground, and it is also possible to apply the embankment that is more than necessary to greatly exceed the load of the structure constructed on the improved ground. Yes, it was very uneconomical.

  The present invention has been made in view of such technical problems, can freely control the loading pressure on the ground, and can efficiently and reliably discharge water and air contained in the soft ground. The purpose of the present invention is to provide a soft ground improvement method that is also effective as a countermeasure for residual subsidence in place of embankment in order to increase the bearing capacity of the ground after ground improvement.

In order to achieve the above object, the invention according to claim 1 is characterized in that the upper surface of the improved ground is covered with an airtight sheet in which the seat terminal is fixed in the periphery of the improved ground, and a vacuum pressure is applied under the airtight sheet to thereby improve the improved ground. In the improvement method of the soft ground to improve the improved ground to the hard ground by creating a decompression area isolated from the improved ground periphery, thereby draining the pore water in the improved ground,
The hermetic sheet has a double structure composed of an upper sheet and a lower sheet, and fluid is introduced into the gap between the upper sheet and the lower sheet in a state where swelling of the upper sheet of the hermetic sheet is suppressed. The gist is an improved construction method for soft ground, in which only the lower sheet is poured to pressurize the improved ground.

  The invention according to claim 2 is characterized in that bulging of the upper sheet is suppressed by using a tensile resistance sheet in which a tensile resistance material is integrated with the upper sheet of the airtight sheet. The gist of the improvement method of soft ground was.

  According to a third aspect of the present invention, a tensile resistance material selected from a net, a rope, and a tensile resistance belt-like sheet fixed to the improved ground peripheral portion is stretched on the upper surface of the upper sheet of the airtight sheet, thereby expanding the upper sheet. The gist of the improvement method for soft ground according to claim 1 or 2, characterized in that it is intended to suppress the outage.

  According to a fourth aspect of the present invention, an upper end of a vertical drain that is placed in the improved ground and forms a vertical supply path is connected to the upper sheet through the lower sheet of the airtight sheet, thereby bulging the upper sheet. The gist of the improvement method of the soft ground according to any one of claims 1 to 3, characterized in that is suppressed.

  The gist of the invention described in claim 5 is the improvement method for soft ground according to any one of claims 1 to 4, wherein the fluid is air or water.

  The gist of the invention described in claim 6 is the improvement method for soft ground according to any one of claims 1 to 5, wherein the airtight sheet is made of a biodegradable material.

  In the improvement method of the soft ground of the present invention, the lower sheet constituting the hermetic sheet is bulged by injecting fluid into the hermetic sheet to pressurize the improved ground, and the lower sheet is bulged. Since the consolidation pressure of the improved ground is promoted by the loading pressure, the optimum loading pressure can be easily applied to the ground simply by adjusting the amount of fluid injected into the airtight sheet. it can. For this reason, it is much easier to control the load pressure on the ground compared to conventional embankment loads that require work such as bringing in and taking out earth and sand, and the water and air contained in the soft ground are efficiently and reliably discharged. can do. In addition, the labor and cost required for this can be greatly reduced. Moreover, according to this soft ground improvement method, it is extremely effective as a countermeasure for residual settlement in place of embankment to increase the bearing capacity of the ground after ground improvement.

  Hereinafter, an improved construction method for soft ground according to the present invention will be described according to an embodiment shown in the drawings. The soft ground improvement method of the present invention (hereinafter simply referred to as improvement method) is to create a decompression area isolated from the periphery of the improved ground using vacuum pressure on the soft ground, and drain the pore water in the soft ground. Then, the soft ground is improved to a hard ground.

  There is no particular limitation on the method of creating a reduced pressure region isolated from the periphery of the improved ground using the vacuum pressure in the improved ground. For example, the improved method described in Japanese Patent No. 3270968 and Japanese Patent Application Laid-Open No. 2003-55951 proposed by the present inventor is more efficient than the conventional method using a conventional sand mat. The pressure can be applied to the improved ground, which is preferable in that a more effective improvement can be realized.

  In the improved construction method described in Japanese Patent No. 3270968, the improved ground is improved by covering the upper surface of the improved ground with an airtight sheet fixed in the periphery of the improved ground and applying a vacuum pressure under the airtight sheet. This is a method of creating a decompression region isolated from the ground periphery, and as shown in FIG. 1, improved by placing the vertical drain material 11 at a predetermined interval leaving the upper end in the improved ground A. A step of creating a vertical drainage wall in the ground A, a step of horizontally arranging the horizontal drain 12 connected to the vacuum pump P so as to contact the upper end of the vertical drain 11, and a vertical drain on the improved ground A A step of covering the upper end of the material 11 with the airtight sheet 21 together with the horizontal drain material 12 and the water collecting pipe 14 and fixing the sheet terminal in the improved ground peripheral part B, and the horizontal drain 12 and the water collecting pipe 4 and vacuum pressure at its periphery about a vertical drain 11 in improvements not operate the vacuum pump P connected through a vacuum tank 15 Soil A state is made of a (vacuum region) produce step.

  The vacuum pressure propagates from the ground around the vertical drain material 11 that has become the decompression region to the ground around the outside, and as a result, the ground pressure (water pressure, earth pressure) toward the vertical drain material 11 is increased. appear.

  In accordance with this ground pressurization, pore water contained in the ground around the vertical drain material 11 is sucked out toward the vertical drain material 11 and drained by using the vertical drain material 11, the horizontal drain material 12 and the water collecting pipe 14 as a drainage path, Along with this, the ground around the outside of the ground around the vertical drain material 11 also becomes a decompression region.

  In this way, the decompression area spreads around the vertical drain material 11 and the ground around it, and the entire improved ground A eventually becomes the decompression area, and at the same time, consolidation and strength increase proceed with the vertical drain material 11 as the center. The whole area is consolidated and the strength is increased.

  In addition, as shown in Japanese Patent Application Laid-Open No. 2003-55951, when the ground is improved, a vacuum pressure is applied to create a reduced pressure region in the improved ground, so that the pore water sucked out from the improved ground is reduced to the vacuum pressure. You may make it discharge | emit through the drainage path different from a propagation path.

  Specifically, as shown in FIG. 1, in the improved ground A below the water collecting pipe 14 connected to each vertical drain material 11 installed at a predetermined interval in the improved ground A through a horizontal drain material 12. A drainage tank 16 that leads to the outside of the improved ground A is disposed, and the pore water collected in the water collection pipe 14 is separated from air by using gravity and drained to the drainage tank 16.

  In this case, as shown in FIG. 1, a drain pipe 17 connected to a main drain tank 19 with a built-in drain pump 18 is connected to the drain tank 16, and the interstitial water in the drain tank 16 passes through the drain pipe 17. The water is drained to the tank 19 and is forcibly discharged to the vacuum tank 15 by the drain pump 18 in the main drain tank 19.

  The present invention proposes a new ground loading method, which becomes a compacted load in place of the embankment that promotes the consolidation settlement of the conventional improved ground A in the improved construction method described above, and includes an upper sheet, a lower sheet, The improved ground is formed by injecting a fluid into a gap between the upper sheet and the lower sheet in a state where the upper sheet of the airtight sheet having a double structure is prevented from bulging, and bulging only the lower sheet. This is characterized by pressurizing.

  As shown in FIGS. 1 and 2, the airtight sheet 21 is a feature of the present invention. As described above, the airtight sheet 21 in which the seat terminal is embedded and fixed in the peripheral portion B of the improved ground is the improved ground. By covering the upper surface of A with the upper end of the vertical drain material 11, the horizontal drain 12, and the water collecting pipe 14, the vacuum pressure from the vacuum pump P is improved in the improved ground A through the water collecting pipe 14, the horizontal drain 12, and the vertical drain 11. Therefore, highly efficient vacuum consolidation can be realized.

  The airtight sheet 21 has a double structure including an upper sheet 22 and a lower sheet 23. In the upper sheet 22, the pressure inside the airtight sheet 21 due to the fluid injection is transmitted to the lower sheet 23 as it is, and only the lower sheet 23 swells. Specifically, a tensile resistance sheet in which a tensile resistance material such as a wire net, a net, or a wire is integrated with a synthetic resin sheet is preferable.

  On the other hand, the lower sheet 23 is desirably a sheet that is airtight and has the ability to expand by the pressure inside the airtight sheet 21 by fluid injection. Specifically, the lower sheet 23 is formed on a synthetic resin sheet or the surface of the synthetic resin sheet. Non-breathable sheets or the like, which are fiber base materials such as woven fabrics, knitted fabrics, and non-woven fabrics and are laminated with extensibility to prevent the generation of pinholes, are suitable.

  Further, as shown in FIG. 2, the airtight sheet 21 has an upper sheet 22 and a lower sheet 23 bonded to each other at a constant interval, and the adhesive portion 25 forms a bulging form of the airtight sheet 21. It has become.

  Then, when a fluid such as water or air is injected into the gap 24 between the upper sheet 22 and the lower sheet 23 of the airtight sheet 21 via a pump (not shown), the upper sheet 22 is moved into the airtight sheet 21 by fluid injection. It does not stretch against the pressure (swelling output) of this, or stays slightly stretched to suppress bulging.

  On the other hand, the lower sheet 23 swells with an internal pressure (swelling output) due to fluid injection and presses the improved ground A. Since the loading pressure due to the bulging of the lower sheet 23 propagates to the improved ground A and pressurizes, the improved ground A that has been depressurized (vacuum load) is pressurized to promote consolidation settlement of the improved ground A.

  The airtight sheet 21 is preferably made of a biodegradable material such as a biodegradable plastic so as to be naturally decomposed when it is buried after being improved in the ground.

  Next, another embodiment of the improved construction method of the present invention will be described. In the form shown in FIG. 3, the airtight sheet 21 shown in FIGS. 1 and 2 is used. Then, a tensile resistance material 30 selected from a net, a rope, and a tensile resistance belt-like sheet fixed to the improved ground peripheral portion is stretched on the upper surface of the upper sheet 22 of the airtight sheet 21.

  Thereby, the tensile resistance force of the tensile resistance material 30 stretched on the upper surface of the upper sheet 22 of the hermetic sheet 21 suppresses the pressure (expansion output) inside the hermetic sheet 21 due to fluid injection, and the expansion of the upper sheet 22 is suppressed. It is supposed to be.

  In addition, in the form shown in FIG. 3, what consists of a tension resistance sheet | seat which integrated the tension resistance material with the upper sheet | seat 22 of the airtight sheet | seat 21 can also be used. In this case, bulging due to fluid injection pressure is more effectively suppressed by the tensile resistance of the tensile resistance material 30 and the tensile resistance of the upper sheet 22 itself.

  As for the tensile resistance material 30 in the form shown in FIG. 3, it is desirable to use a material made of a biodegradable material such as a biodegradable plastic like the airtight sheet 21.

    Next, still another embodiment of the improved construction method of the present invention will be described. In the form shown in FIG. 4, the upper end of the vertical drain 11 that is placed in the improved ground A and forms the vertical supply path passes through the lower sheet 23 of the airtight sheet 21, and is sewn and bonded to the inner surface of the upper sheet 22. The upper sheet is prevented from bulging by being connected by a method such as heat fusion.

  The vertical drain 11 placed in the improved ground A is connected to the inner surface of the upper sheet 22, and in this state, a fluid such as water or air is injected into the gap 24 between the upper sheet 22 and the lower sheet 23 of the airtight sheet 21. Then, a force is exerted on the upper sheet 22 to bulge upward by internal pressure (bulging output) due to fluid injection. For this reason, a pulling force acts on the vertical drain 11 connected to the upper sheet 22. However, since a frictional force acts on the vertical drain 11 with the surrounding ground, the vertical drain 11 connected to the upper seat 22 serves as an anchor so as to suppress the bulging of the upper seat 22. Become.

  Note that it is desirable that the vertical drain 11 used in this embodiment be combined with a tensile resistance material such as a piano wire, a wire net, and a net so as to be able to resist the pulling force.

  In the embodiment shown in FIG. 4, it is also possible to use a sheet composed of a tensile resistance sheet in which a tensile resistance material is integrated with the upper sheet 22 of the airtight sheet 21. In this case, the vertical drain 11 connected to the upper sheet 22 functions as an anchor, and the bulging due to the pressure of fluid injection is more effectively suppressed by the tensile resistance force of the upper sheet 22 itself. .

The cross-sectional schematic diagram which showed the example of application of the improved construction method of this invention. The top view of FIG. 1 similarly. The cross-sectional schematic diagram which showed another form of the improved construction method of this invention. The cross-sectional schematic diagram which showed another form of the improved construction method of this invention. The schematic diagram which showed the example of application of the conventional improved construction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Vertical drain material 12 ... Horizontal drain material 14 ... Water collecting pipe 15 ... Vacuum pump 21 ... Airtight sheet 22 ... Upper sheet 23 ... Lower sheet 24 ... Gap 30 ... Tensile resistance material A ... Improved ground B ... Peripheral ground

Claims (6)

Covering the upper surface of the improved ground with an airtight sheet fixed in the periphery of soft ground for improving the seat terminal (hereinafter referred to as improved ground), and applying a vacuum pressure to the improved ground, In the improved construction method of the soft ground that creates an isolated decompression area and drains the pore water in the improved ground, thereby improving the improved ground to a hard ground,
The hermetic sheet has a double structure composed of an upper sheet and a lower sheet, and fluid is introduced into the gap between the upper sheet and the lower sheet in a state where swelling of the upper sheet of the hermetic sheet is suppressed. An improved construction method for soft ground, wherein only the lower sheet is injected to bulge and the improved ground is pressurized.   2. The soft ground improvement method according to claim 1, wherein a bulge of the upper sheet is suppressed by using a tensile resistance sheet in which a tensile resistance material is integrated with the upper sheet of the airtight sheet.   The expansion of the upper sheet was suppressed by stretching a tensile resistance material selected from the net, rope, and tension-resistant belt-like sheet fixed to the peripheral area of the improved ground on the upper surface of the upper sheet of the airtight sheet. The improvement method of the soft ground according to any one of claims 1 and 2.   The upper end of the vertical drain that is placed in the improved ground and forms the vertical supply path passes through the lower sheet of the airtight sheet and is connected to the upper sheet, thereby suppressing the swelling of the upper sheet. The improvement construction method of the soft ground in any one of Claims 1-3.   The improvement method for soft ground according to any one of claims 1 to 4, wherein the fluid is air or water.   The method for improving soft ground according to any one of claims 1 to 5, wherein the airtight sheet is made of a biodegradable material.

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