JP5525843B2 - Ground reinforcement structure and ground reinforcement method - Google Patents

Description

  The present invention relates to a ground reinforcing structure and a reinforcing method for which occurrence of a liquefaction phenomenon due to an earthquake or the like is predicted.

  Conventionally, when existing structures exist on soft ground that may be liquefied in the event of an earthquake, the existing structure should be surrounded to prevent deformation of the ground due to the liquefaction phenomenon. He was building an underground wall.

  For example, Patent Document 1 discloses a structure in which a steel sheet pile is driven so as to surround an existing structure and its upper end is connected in the circumferential direction with steel, concrete, or the like. This structure prevents the upper end of the steel sheet pile from deforming outward during an earthquake by connecting the upper ends of the steel sheet piles. That is, the earth and sand in the ground surrounded by the steel sheet pile is prevented from flowing out of the steel sheet pile.

JP 2002-167778 A

  However, in the structure described in Patent Document 1, since only the upper end of the steel sheet pile is connected, the rigidity and strength of the ground cannot be increased. Therefore, there is a problem that the ground surrounded by the steel sheet pile is liquefied.

  Then, this invention is made | formed in view of the above conventional problems, Comprising: It aims at providing the reinforcement structure and reinforcement method of a ground which can prevent liquefaction of the ground at the time of an earthquake. Is.

To achieve the above object, the reinforcing structure of the ground of the present invention, the gap a reinforcing target zone with planar shape surrounds as a rectangular, reaches its lower end to the supporting ground, and a corner portion of the rectangular And a load applying means for applying a load toward the inside of the area to be reinforced to the constraint material.
Further, the ground reinforcing structure of the present invention is such that the C-shaped member in plan view has its both ends overlapped in the circumferential direction so as to surround the entire circumference of the area to be reinforced, and the lower end thereof reaches the supporting ground. A restraint material installed inside,
A load applying means for applying a load toward the inside of the area to be reinforced to the binding material;
The load applying means includes a connecting member that is in an annular shape so as to contact an outer peripheral surface of the restricting member and surround the area to be reinforced, and by applying a tensile force to the connecting member, It is characterized by applying a load to the material.

  According to the ground reinforcement structure of the present invention, by applying a load to the restraint material by the load imparting means, prestress can be applied to the ground in the area to be reinforced to increase the lateral restraint pressure. Furthermore, since the lateral restraint pressure increases, the rigidity and strength of the ground increase, so that liquefaction of the ground during an earthquake can be prevented and deformation of the ground can be prevented.

  Further, in the present invention, the load applying means includes a rod-like or wire-like connecting material that connects the restraining materials installed at opposing positions, and the restraining force is applied to the connecting material by applying a tensile force. If a load is applied to the material, prestress can be easily applied to the area to be reinforced.

Also, the prior SL restraining member, since it is arranged to surround the reinforcing target zone, the tensile force acting on the connecting member due to stress relaxation due creep connecting member is reduced, the ground deformation due to an earthquake A tensile force can be applied to the connecting material. Therefore, even if the tensile force acting on the connecting material is reduced, the tensile force can be applied to the connecting material due to ground fluctuation, so that the lateral restraint pressure can be increased.

Further, in the present invention, the load applying means has a connecting material that is arranged in an annular shape so as to be in contact with the outer peripheral surface of the restraining material and surround the area to be reinforced, and exert a tensile force on the connecting material. Thus, if a load is applied to the restraint material, prestress can be easily applied to the area to be reinforced.
Furthermore, since the connecting material is arranged so as to surround the area to be reinforced, even if the tensile force acting on the connecting material decreases due to stress relaxation due to the creep of the connecting material, the tensile force is applied to the connecting material due to ground fluctuation due to the earthquake. Can act. Therefore, even if the tensile force acting on the connecting material is reduced, the tensile force can be applied to the connecting material due to ground fluctuation, so that the lateral restraint pressure can be increased.

  Further, in the present invention, when the tensile force acting on the connecting material is reduced, the tensile force acting on the connecting material is assumed to have a self-repairing property in which the tensile force of the connecting material increases due to ground deformation due to an earthquake. Even if the force is reduced, a tensile force can be applied to the connecting material due to ground fluctuation, so that the lateral restraint pressure can be reliably recovered.

  Further, in the present invention, if at least one of the load applying means is provided above and below the groundwater level, an optimum large prestress to prevent liquefaction is applied from the groundwater level. Can also be accurately applied to the upper and lower layers, respectively.

Retrofit for ground of the present invention, a groove constructing step of reinforcing the area of interest planar shape to construct a groove taken enclose Jo Tokoro depth as a rectangular, the reinforcing target zone planar shape a rectangular It surrounds is taken as to reach the lower end thereof to the supporting ground and an installation step of installing a rectangular shape in plan view of the restraining member so that a gap is provided in the groove in the corners of the rectangular shape, the constraining And a load applying step for applying a load toward the inside of the area to be reinforced to the material.
Further, the ground reinforcing method of the present invention comprises a groove construction step of constructing a groove having a predetermined depth so as to surround the entire circumference of the area to be reinforced, and a plurality of C-shaped members in plan view in the circumferential direction. The installation process of installing as a restraining material in the groove so that the lower end reaches the supporting ground by overlapping each other, and the load toward the inside of the reinforcing target area And applying a tensile force to the connecting material arranged in an annular shape so as to contact the outer peripheral surface of the restraining material and surround the area to be reinforced. The load is applied to the restraining material.

  According to the ground reinforcement method of the present invention, a load toward the inside of the area to be reinforced is applied to the restraint material, so that the side restraint pressure can be increased by applying prestress to the ground in the area to be reinforced. Furthermore, since the lateral restraint pressure increases, the rigidity and strength of the ground increase, so that liquefaction of the ground during an earthquake can be prevented and deformation of the ground can be prevented.

  Further, in the present invention, the load applying step is performed by connecting the restraining materials installed at the opposing positions with a rod-like or wire-like connecting material and applying a tensile force to the connecting material. If a load is applied to the area, prestress can be easily applied to the area to be reinforced.

  Moreover, in the present invention, the load applying step is performed by arranging a connecting material in an annular shape so as to surround the area to be reinforced while contacting the outer peripheral surface of the restraining material, and applying a tensile force to the connecting material. If a load is applied to the restraint material, prestress can be easily applied to the area to be reinforced.

  According to the present invention, the lateral restraint pressure increases, and the rigidity and strength of the ground can be increased. Therefore, liquefaction of the ground in the area to be reinforced can be prevented during an earthquake.

It is sectional drawing which shows the reinforcement structure of the ground which concerns on 1st embodiment of this invention. It is a top view which shows the reinforcement structure of the ground which concerns on 1st embodiment of this invention. It is sectional drawing which shows the action state of the side restraint pressure by the ground reinforcement structure which concerns on this embodiment. It is a top view which shows the other Example of the reinforcement structure of the ground which concerns on this embodiment. It is sectional drawing which shows the reinforcement structure of the ground which concerns on 2nd embodiment of this invention. It is a top view which shows the reinforcement structure of the ground which concerns on 2nd embodiment of this invention. It is a perspective sectional view showing the ground reinforcement structure concerning a third embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG.1 and FIG.2 is sectional drawing and the top view which show the reinforcement structure 1 of the ground E which concerns on 1st embodiment of this invention.

  As shown in FIG. 1 and FIG. 2, the reinforcing structure 1 of the ground E includes a restraining material 4 installed in the ground E so as to surround the entire area to be reinforced 2, and an inner side of the reinforcing material area 2 on the restraining material 4. Load applying means 5 for applying a load toward the head. An existing structure 3 exists on the ground E in the reinforcement target area 2.

  The constraining material 4 passes through the liquefied layer E1 that may be liquefied when an earthquake occurs, and the lower end thereof is installed so as to reach a predetermined depth of the solid support ground of the non-liquefied layer E2. .

  In the present embodiment, a sheet pile is used as the restraining material 4. A plurality of sheet piles, for example, are installed so as to surround the existing structure 3 of a prismatic building and have a rectangular planar shape. Among the restraining members 4 arranged in a rectangular shape, the sheet piles arranged at positions corresponding to the sides 4a of the rectangle are connected and connected so as to be continuous. On the other hand, a gap 4c is provided between adjacent and adjacent sheet piles that are arranged at positions corresponding to the corners 4b so as not to be continuous.

  In the present embodiment, a sheet pile is used as the restraining material 4, but the present invention is not limited to this, and an underground wall made of concrete or the like may be used. In this case as well, the gap 4 c is formed in the corner 4 b. Provide.

  The constraining material 4 surrounds the entire area to be reinforced 2 in a groove 6 having a predetermined depth that is drilled so as to surround the area to be reinforced 2 and the lower end reaches the non-liquefied layer E2. Installed.

  The load applying means 5 is installed in the liquefied layer E1, and has rod-shaped anchor bolts 5a that connect the restraining members 4 installed at the opposing positions, and nuts 5b that are screwed to both ends of the anchor bolts 5a. By tightening both the nuts 5b and applying a tensile force to the anchor bolt 5a, a load directed to the reinforcement target area 2 is applied to the restraint material 4. Then, a prestress (that is, a compressive force) is applied to the ground E surrounded by the restraining material 4 by the load toward the reinforcement target area 2.

  When the opposing restraint members 4 are connected to each other, as shown in a dotted circle A in FIG. 2, the anchor bolt 5a installed in the horizontal direction with respect to FIG. 2 and the vertical direction with respect to FIG. Since the anchor bolt 5a intersects in the liquefied layer E1, for example, the anchor bolt 5a installed in the left-right direction is disposed at a depth shallower by several cm than the anchor bolt 5a installed in the up-down direction. Therefore, a plurality of anchor bolts 5a are installed at almost the same depth.

  Further, the load applying means 5 is provided in one stage above and below the groundwater level. That is, a plurality of stages are provided in the depth direction.

  The anchor bolt 5a of the load applying means 5 is installed in the ground E by being inserted into the horizontal hole drilled from the groove 6 by horizontal boring. Then, when the nut 5b is screwed to both ends of the anchor bolt 5a and the nut 5b is tightened, the lower end portion of the restraint material 4 is deeply rooted and fixed in the non-liquefaction layer E2, and is shown in FIG. As described above, the liquefied layer E1 and the non-liquefied layer E2 (that is, the ground E) under the existing structure 3 which is the area 2 to be reinforced are compressed by an inward load acting on the upper end portion of the restraint material 4. To do. Moreover, although the restraint material 4 is arrange | positioned so that a planar shape may become a rectangle, the clearance gap 4c is provided in the corner | angular 4b, and since the restraint material 4 is not continuing, the restraint material 4 can deform | transform toward an inner side. is there. In order to apply a load inward to the restraint 4 and to apply prestress to the ground E efficiently, it is desirable to install the load applying means 5 on the restraint 4 as much as possible. Here, the pre-stress is set so as to prevent the ground E in the reinforcement target area 2 from swelling.

  Since stress relaxation due to creep of the anchor bolt 5a and loosening of the nut 5b may reduce prestress acting on the ground E, the groove 6 is opened so that the nut 5b can be tightened again. And it is desirable to maintain prestress by performing regular maintenance.

  However, even if an earthquake occurs when the prestress is lowered, it has a self-repairing property that increases the lateral restraint pressure by applying a tensile force to the anchor bolt 5a. Can be made.

  That is, in the case of the ground E in which liquefaction does not occur during an earthquake, the volume expands due to soil dilatency when a horizontal load due to the earthquake acts. As a result, the soil in the area to be reinforced 2 tends to swell outward, but is restrained by the restraining material 4, and hence the tensile force acts on the anchor bolt 5 a via the restraining material 4 due to the expansion force. become. Further, when the ground E is liquefied due to the earthquake and excessive pore water pressure is generated, the soil strength is reduced, but the soil pressure including muddy water acts on the side, so that the restraint 4 is similar to the above. Thus, a tensile force acts on the anchor bolt 5a.

  According to the reinforcing structure 1 of the ground E having the above-described configuration, the constraining material 4 that surrounds the entire area to be reinforced 2 and that has its lower end reaching the non-liquefied layer E2 is installed at the opposite position. Since the load applying means 5 for connecting the restrained materials 4 to each other is provided, it is possible to apply prestress to the ground E in the reinforcement target area 2 by tightening the load applying means 5. Then, by applying prestress, the lateral restraint pressure increases, so the rigidity and strength of the ground E can be increased. Therefore, liquefaction of the ground E during an earthquake can be prevented, and deformation of the ground E can be prevented.

  Further, the load applying means 5 includes an anchor bolt 5a that penetrates the ground E in the reinforcement target area 2 and the restraining members 4 that are installed at opposing positions, and nuts 5b that are screwed to both ends of the anchor bolt 5a. Therefore, prestress can be applied to the ground E in the area 2 to be reinforced by tightening the nut 5b and applying a tensile force to the anchor bolt 5a. Since the tightening operation of the nut 5b is easy, this operation can be performed in a short time.

  In addition, since the load applying means 5 is provided above and below the groundwater level in the reinforcement target area 2, respectively, a large prestress optimum for preventing liquefaction is applied to the liquefied layer E1 and It can be accurately applied to the non-liquefied layer E2.

  In addition, since the restraining material 4 is arranged so as to surround the entire area 2 to be reinforced, even if the tensile force acting on the anchor bolt 5a decreases, the tensile force acts on the anchor bolt 5a due to the ground fluctuation at the time of the earthquake. Thus, the lateral restraint pressure can be increased. Therefore, even if the tensile force of the anchor bolt 5a is reduced at the time of an earthquake, it is possible to prevent the deformation of the ground E that causes damage to the existing structure 3 due to an increase in the restraining pressure due to the earthquake.

  In the present embodiment, the case has been described in which the restraining material 4 is installed in a rectangular shape, and all the sheet piles arranged at positions corresponding to the sides 4a of the rectangular shape are connected and continuous, but the present invention is not limited thereto. For example, as shown in FIG. 4, sheet piles may be arranged discretely to form a portion corresponding to the rectangular side 4a. Here, the degree of discreteness of the sheet pile is appropriately determined by design or the like.

  Moreover, in this embodiment, although the case where the anchor bolt 5a was used as a connection material of the load provision means 5 was demonstrated, it is not limited to this, For example, you may use a wire rope, In this case Is connected to a jack, a turnbuckle or the like for applying a tensile force by winding the wire rope around one end of the wire rope.

  Moreover, in this embodiment, when the anchor bolts 5a of the load applying means 5 intersect in the ground E, the case where the installation depth of one anchor bolt 5a is moved in the vertical direction by several cm has been described. However, the present invention is not limited to this. A cross turn buckle having a gap through which the anchor bolt 5a can be inserted is attached to the intersecting portion, and the anchor bolt 5a that intersects the gap is inserted. You may install in the same depth.

  In the present embodiment, the case where the restraint member 4 is installed so that the planar shape thereof is rectangular has been described. However, the present invention is not limited to this and is installed so as to have other polygonal shapes. May be.

  Next, another embodiment of the present invention will be described. In the following description, portions corresponding to the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described.

  5 and 6 are a sectional view and a plan view showing the reinforcing structure 21 of the ground E according to the second embodiment of the present invention.

  As shown in FIG. 5 and FIG. 6, the reinforcing structure 21 of the ground E has a restraining material 24 installed in the ground E so as to surround the reinforcing target area 22, and the restraining material 24 to the inside of the reinforcing target area 22. Load applying means 25 for applying a load to be directed. An existing structure 23 exists on the ground E in the reinforcement target area 22.

  As in the first embodiment, a sheet pile was used as the restraining material 24. A plurality of sheet piles are installed so as to surround the entire circumference of the existing structure 23 that is, for example, a cylindrical oil tank and to have a C-shaped planar shape. A plurality of sheet piles arranged in a C-shape are connected and installed so as to be continuous, but both ends thereof are displaced in the radial direction so as not to interfere with each other and are installed so as to overlap in the circumferential direction. Yes.

  In addition, in this embodiment, although the case where the notch part of the restraint material 24 was provided in one place was demonstrated, it is not limited to this, You may provide in multiple places.

  As in the first embodiment, the restraint member 24 is in contact with the outer peripheral surface of the reinforcement target area 22 in the groove 6 having a predetermined depth drilled so as to surround the reinforcement target area 22, and the lower end thereof is non-liquid. It is placed and installed so as to reach the formation layer E2.

  The load applying means 25 is in contact with the outer periphery of the constraining material 24 arranged in a C-shape, and has a reinforcing bar 25a arranged in an annular shape so as to surround the reinforcement target area 22, and a turnbuckle 25b screwed to both ends thereof. Have. By tightening the turnbuckle 25b and applying a tensile force to the reinforcing bar 25a, a load directed inward in the radial direction of the reinforcing bar 25a arranged in an annular shape is applied to the restricting member 24, thereby being surrounded by the restricting member 24. Prestress is applied in the reinforced object area 22. Specifically, when the turnbuckle 25b is tightened, both ends of the restraint member 24 slide in different circumferential directions, so that the restraint member 4 is deformed inward. At this time, since the lower end portion of the restraint material 24 is deeply embedded and fixed in the non-liquefaction layer E2, an inward load acts on the upper end portion of the restraint material 24 to form the reinforcement target area 22. The liquefied layer E1 and the non-liquefied layer E2 (that is, the ground E) under the structure 23 are compressed.

  As with the first embodiment, the load applying means 25 is provided one step above and below the groundwater level.

  The load applying means 25 is installed in the liquefied layer E1, and prestress is applied. Like the first embodiment, the groove 6 used when installing the load applying means 25 or the like may reduce prestress acting on the ground E due to stress relaxation due to creep of the reinforcing bars 25a or loosening of the turnbuckle 25b. Therefore, the turnbuckle 25b is opened again so that the turnbuckle 25b can be tightened. And it is desirable to maintain prestress by performing regular maintenance.

  However, even if an earthquake occurs when the prestress is lowered, it has a self-repairing property that increases the lateral restraint pressure by applying a tensile force to the reinforcing bar 25a, so that the prestress is recovered by the occurrence of the earthquake. be able to.

  That is, in the case of the ground E in which liquefaction does not occur during an earthquake, the volume expands due to soil dilatency when a horizontal load due to the earthquake acts. As a result, the soil in the region 22 to be reinforced tends to bulge outward, but is restrained by the restraining material 24, so that a tensile force acts on the reinforcing bar 25 a via the restraining material 24 by the expansion force. Become. In addition, when the ground E is liquefied due to the earthquake and excessive pore water pressure is generated, the soil strength is reduced, but the soil pressure including muddy water acts on the side, so that the restraint material 24 is similar to the above. A tensile force acts on the reinforcing bar 25a through the wire.

  According to the reinforcing structure 21 of the ground E having the above-described configuration, the restraining material 24 that surrounds the entire area 22 to be reinforced and has a lower end that reaches the non-liquefaction layer E2, and the restraining material 24 Since the ring-shaped load applying means 25 is provided so as to be in contact with the outer periphery, prestress can be applied to the ground E in the area 2 to be reinforced by tightening the load applying means 25. Furthermore, since the lateral restraint pressure is increased by applying prestress, the rigidity and strength of the ground E can be increased. Therefore, liquefaction of the ground E during an earthquake can be prevented, and deformation of the ground E can be prevented.

  Moreover, since the restraint material 24 is arrange | positioned so that the surrounding area 22 to be reinforced may be surrounded, even if the tensile force which acts on the reinforcing bar 25a falls, the tensile force is made to act on the reinforcing bar 25a by the ground fluctuation at the time of an earthquake. The lateral restraint pressure can be increased. Therefore, it is possible to prevent the deformation of the ground E that causes damage to the existing structure 23 during an earthquake.

  In the present embodiment, the connecting material composed of the reinforcing bar 25a and the turnbuckle 25b is used as the load applying means 25. However, the present invention is not limited to this. It may be used.

  Next, a third embodiment will be described. In the third embodiment, the ground E which is the basis of a linear structure constructed long in one direction is used as the reinforcement target area 32.

  FIG. 7 is a perspective sectional view showing a reinforcing structure 31 for the ground E according to the third embodiment of the present invention.

  As shown in FIG. 7, the reinforcement structure 31 of the ground E is directed to the inside of the reinforcement target area 32 by the restraint material 4 installed in the ground E so as to sandwich the reinforcement target area 32 from both sides, and the restraint material 4. Load applying means 5 for applying a load. An existing structure 33 exists on the ground E in the reinforcement target area 32.

  The restraint material 4 is installed along the longitudinal direction on both sides of an existing structure 33 in which a plurality of sheet piles are, for example, viaducts. The plurality of sheet piles are connected so as to be continuous.

  The restraint member 4 is placed and installed in the groove 6 having a predetermined depth drilled on both sides of the reinforcement target area 32 so that the lower end reaches the non-liquefied layer E2.

  As in the first embodiment, when the nut 5b is screwed to both ends of the anchor bolt 5a of the load loading means 5 and the nut 5b is tightened, the lower end portion of the restraining material 4 is deeply rooted in the non-liquefied layer E2. Since it is inserted and fixed, a load toward the inside acts on the upper end portion of the restraint material 4 and the liquefied layer E1 and the non-liquefied layer E2 under the existing structure 33 that is the reinforcement target area 32 (that is, the liquefied layer E2) Compress the ground E) and apply prestress.

  According to the reinforcing structure 31 of the ground E having the above-described configuration, the reinforcing material area 32 is sandwiched and the lower end of the reinforcing material area 32 reaches the non-liquefied layer E2, and the constraining material 4 is installed at the opposite position. Since the load applying means 5 for connecting the restraining members 4 to each other is provided, prestress can be applied to the ground E in the reinforcement target area 32 by tightening the load applying means 5. Then, by applying prestress, the lateral restraint pressure increases, so the rigidity and strength of the ground E can be increased. Therefore, liquefaction of the ground E during an earthquake can be prevented, and deformation of the ground E can be prevented.

DESCRIPTION OF SYMBOLS 1 Ground reinforcement structure 2 Reinforcement target area 3 Existing structure 4 Restraint material 4a Side 4b Corner 4c Clearance 5 Load applying means 5a Anchor bolt 5b Nut 6 Groove 21 Ground reinforcement structure 22 Reinforcement target area 23 Existing structure 24 Restraint material 25 Load applying means 25a Reinforcing bar 25b Turnbuckle 31 Ground reinforcement structure 32 Reinforcement target area 33 Existing structure E Ground E1 Liquefaction layer E2 Non-liquefaction layer

Claims (8)

It is a ground reinforcement structure,
With a reinforcing target zone planar shape surrounds as a rectangular, a restraining member to which the lower end reaches the supporting ground, and a gap is installed in the ground to be provided at the corners of the rectangular,
A ground reinforcement structure comprising load imparting means for imparting a load toward the inside of the area to be reinforced to the restraining material. It is a ground reinforcement structure,
A C-shaped member in plan view, the both ends of which are overlapped in the circumferential direction to surround the entire circumference of the area to be reinforced, and a restraining material that is installed in the ground so that its lower end reaches the support ground,
A load applying means for applying a load toward the inside of the area to be reinforced to the binding material;
The load applying means includes a connecting member that is in an annular shape so as to contact an outer peripheral surface of the restricting member and surround the area to be reinforced, and by applying a tensile force to the connecting member, A ground reinforcement structure characterized by applying a load to a material.   The load applying means has a rod-like or wire-like connecting material that connects the constraining materials installed at opposing positions, and applies a tensile force to the connecting material to apply a load to the constraining material. The ground reinforcing structure according to claim 1, wherein: The ground reinforcing structure according to any one of claims 1 to 3 , wherein a groove is provided so as to surround the area to be reinforced, and the restraining material is driven into the groove . 4. The ground reinforcing structure according to claim 2, wherein when the tensile force acting on the connecting material is reduced, the ground reinforcing structure has a self-repairing property in which the tensile force of the connecting material increases due to ground change due to an earthquake. .   The ground reinforcing structure according to any one of claims 1 to 5, wherein at least one load applying means is provided above and below the groundwater level. In the ground reinforcement method,
A groove constructing step of reinforcing the area of interest planar shape to construct a groove taken enclose Jo Tokoro depth as a rectangular,
Together with the reinforcing target zone planar shape surrounds as a rectangular, it reaches its lower end to the supporting ground, and said rectangular shape in plan view of the restraining member so that a gap is provided at a corner of the rectangular shape Installation process to install in the groove;
A ground reinforcement method comprising a load application step of applying a load toward the inside of the area to be reinforced to the restraint material. In the ground reinforcement method,
A groove constructing step of constructing the groove of Jo Tokoro depth to surround the entire periphery of the reinforcement area of interest,
An installation step of installing a plurality of C-shaped members in plan view as a restraining material in the groove so as to partially overlap in the circumferential direction so as to surround the entire circumference of the area to be reinforced and to have a lower end reaching the support ground ; ,
A load application step for applying a load toward the inside of the area to be reinforced to the restraint material ,
In the load application step, a load is applied to the restraint material by applying a tensile force to a connecting material arranged in an annular shape so as to contact the outer peripheral surface of the restraint material and surround the area to be reinforced. A ground reinforcement method characterized by

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