JP6401590B2 - Ground improvement structure - Google Patents

Description

  The present invention relates to a ground improvement structure.

  Patent Document 1 discloses a seismic reinforcement structure for a box culvert that improves the seismic performance by reinforcing the box culvert from the outside by a ground improvement body formed by improving the ground around the box culvert.

  In Patent Document 2, the ground improvement material is injected into the outer periphery of the existing tunnel to increase the shear rigidity of the ground, thereby reducing the amount of shear deformation of the ground on the outer periphery of the tunnel during an earthquake and reducing the amount of shear deformation of the tunnel. Thus, an earthquake resistant reinforcement method for an existing tunnel that reduces the cross-sectional force generated during the earthquake of the tunnel is disclosed.

  Here, the underground structure buried in the ground may rise due to liquefaction of the surrounding ground. In addition, the ground horizontal displacement may increase due to liquefaction of the surrounding ground or surface waves may be amplified, which may cause the underground structure to rotate.

Japanese Patent No. 5267879 Patent opening 2001-26922

  An object of the present invention is to suppress the floating of underground structures buried in the ground when the liquefied layer is liquefied.

The ground improvement structure of the first aspect is constructed so as to overlap the lower outer edge portion of the underground structure embedded in the liquefied layer in a plan view and reach the non-liquefied layer below the liquefied layer. An earth pressure adjusting means for increasing the earth pressure acting on the lower portion of the side wall portion by horizontal ground displacement, provided at the upper end portion of the ground improvement wall in contact with the side wall portion of the underground structure. Is provided.

In the ground improvement structure of the first aspect , the ground improvement body formed around the underground structure in the liquefaction layer suppresses the supply of soil to the lower side of the underground structure during liquefaction.

  In addition, the earth pressure adjusting means provided at the upper end of the ground improvement wall in contact with the side wall of the underground structure allows the earth pressure acting on the lower part of the side wall due to horizontal displacement when liquefied to adjust the earth pressure. It is larger than when no means are provided. Therefore, rotation of the underground structure when the liquefied layer is liquefied is suppressed.

  In this way, by providing a ground improvement wall with earth pressure adjusting means at the upper end around the underground structure, the soil is supplied to the lower side of the underground structure during liquefaction during an earthquake. Is suppressed, and the rotation of the underground structure is suppressed, so that the floating of the underground structure is effectively suppressed.

In the ground improvement structure according to the second aspect, the earth pressure adjusting means is a tapered body formed at the upper end portion of the ground improvement wall and having a width narrowing toward the upper side.

In the ground improvement structure of the second aspect, a tapered body whose width becomes narrower toward the upper side is formed at the upper end of the ground improvement wall. Therefore, the earth pressure which acts on the lower part of a side wall part by the ground horizontal displacement at the time of liquefaction becomes large. Therefore, the rotation of the underground structure when the liquefied layer is liquefied is suppressed.

In the ground improvement structure according to the third aspect, the earth pressure adjusting means is a protruding portion that is formed at the upper end portion of the ground improvement wall and protrudes outward.

In the ground improvement structure of the third aspect , a protruding portion that protrudes outward is formed at the upper end portion of the ground improvement wall. Therefore, the earth pressure which acts on the lower side of the side wall portion due to horizontal ground displacement when liquefied is increased. Further, the rotation resistance is increased by the protrusion. Therefore, rotation of the underground structure when the liquefied layer is liquefied is effectively suppressed.

The ground improvement structure of the fourth aspect is constructed so as to overlap the lower outer edge portion of the underground structure embedded in the liquefied layer in a plan view and to reach the non-liquefied layer below the liquefied layer. The ground improvement wall which an upper end part contacts the side wall part of the underground structure, and the wide part provided in the site | part which reaches the said non-liquefaction layer in the said ground improvement wall are provided.

In the ground improvement structure of the fourth aspect , the supply of soil to the lower side of the underground structure is suppressed by the ground improvement body formed around the underground structure in the liquefied layer.

  Further, the pulling resistance force and the pushing resistance force of the ground improvement wall are increased by the wide portion provided in the portion reaching the liquefied layer in the ground improvement wall. Therefore, the restraint force of the ground improvement with respect to the underground structure when the liquefied layer is liquefied increases, and the rotation of the underground structure is suppressed.

  In this way, by providing a ground improvement wall with a wide part at the site that reaches the non-liquefiable layer around the underground structure, it is below the underground structure during liquefaction during an earthquake. Since the supply of soil is suppressed and the rotation of the underground structure is suppressed, the floating of the underground structure is effectively suppressed.

The ground improvement structure according to the fifth aspect includes a ground improvement body formed by injecting a chemical into the liquefaction layer below the underground structure embedded in the liquefaction layer and having a cavity.

In the ground improvement structure of the fifth aspect , liquefaction of the liquefaction layer below the underground structure is suppressed by the ground improvement body formed by injecting the chemical solution below the underground structure in the liquefaction layer. And the supply of soil is suppressed. Moreover, a ground improvement body can be formed at low cost by providing a cavity. Therefore, the floating of the underground structure when the liquefied layer is liquefied is suppressed at low cost.

The ground improvement structure according to the sixth aspect is provided on the outside of the underground structure, provided in a pile embedded in a non-liquefied layer below the liquefied layer, and provided in an upper end portion of the pile. A rotation stop portion that approaches or contacts the side wall portion of the structure.

In the ground improvement structure of the sixth aspect , the pile embedded in the non-liquefied layer below the liquefied layer is provided outside the underground structure, and is close to the side wall of the underground structure at the upper end of the pile. Or the rotation stop part which contacts is provided. Therefore, the rotation of the underground structure when liquefied is suppressed by the pile and the rotation stopper. Therefore, the floating of the underground structure when the liquefied layer is liquefied is further suppressed.

  According to the present invention, it is possible to suppress the floating of underground structures embedded in the ground when the liquefied layer is liquefied.

It is a longitudinal section showing the ground improvement structure of a first embodiment typically. It is a longitudinal cross-sectional view which shows typically the ground improvement structure of the modification of 1st embodiment. It is a longitudinal cross-sectional view which shows typically the ground improvement structure of 2nd embodiment. It is a longitudinal section showing the ground improvement structure of a third embodiment typically. It is a longitudinal cross-sectional view which shows the ground improvement structure of 4th embodiment typically. It is a longitudinal cross-sectional view explaining the behavior of the common groove at the time of an earthquake when the ground improvement structure of this invention is not applied. It is the elements on larger scale explaining the state where the lower horizontal force which acts on the side wall part of a common groove became large by the ground improvement structure of a first embodiment.

<First embodiment>
A first embodiment of the present invention will be described with reference to FIG.

(Construction)
As shown in FIG. 1, the ground 10 is composed of a liquefied layer 12 that may be liquefied during an earthquake and a support layer (non-liquid layer) 14 below the liquefied layer 12. In addition, in order to make an explanation easy to understand, the ground 10 includes a liquefied layer 12 and a support layer (non-liquid layer) 14, but is not limited thereto. It may be composed of three or more layers.

  A common groove 50 as an example of an underground structure is embedded in the liquefied layer 12 of the ground 10. A ground improvement wall 100 is constructed around the common groove 50. In addition, although the joint groove | channel 50 of this embodiment is a product made from reinforced concrete, since the cavity is formed inside, specific gravity is heavier than water, but specific gravity is lighter than the soil of the liquefied layer 12.

  The ground improvement wall 100 of this embodiment is constructed by wrapping an improved pile by a mechanical stirring method or a high-pressure jet stirring method. The mechanical agitation method is a method of constructing a ground improvement wall by creating an improved pile in the ground by mixing and agitating the in-situ soil and the improved material with an agitating blade on the rotating shaft of the construction machine. Note that the mechanical stirring method or the high-pressure jet stirring method is a well-known technique, and a detailed description thereof will be omitted. Moreover, the high-pressure jet agitation method can be suitably implemented even with the existing joint groove 50 (underground structure).

  The ground improvement wall 100 is constructed so as to overlap the lower outer edge portion 52 around the common groove 50 in a plan view. Further, the ground improvement wall 100 has a lower end portion 102 embedded (embedded) or bottomed in the support layer 14.

  In addition, a substantially triangular tapered portion 112 whose width becomes narrower toward the upper side is formed on the upper end portion 110 in contact with the side wall portion 54 of the joint groove 50 in the ground improvement wall 100. That is, the tapered portion 112 in contact with the side wall portion 54 of the common groove 50 is thinner toward the upper side and thicker toward the lower side.

(Function and effect)
Next, the operation and effect of this embodiment will be described.

  First, the behavior of the joint groove 50 during an earthquake (when the liquefied layer 12 is liquefied) when the ground improvement structure of the present invention is not applied will be described.

  As described above, the common groove 50 has a specific gravity heavier than water but lighter than the soil of the liquefied layer 12. Therefore, when the liquefied layer 12 is liquefied at the time of an earthquake, as indicated by an arrow W, buoyancy acts on the joint groove 50 and the joint groove 50 is lifted. In addition, when the common groove | channel 50 floats, as shown by the arrow K, soil (muddy water) is supplied to the lower side of the common groove 50 from the circumference | surroundings.

  Further, a surface wave S and a horizontal displacement H are generated during an earthquake. Since the horizontal displacement H at the time of an earthquake is larger on the upper side (closer to the ground surface 10A), the dynamic earth pressure is larger on the upper side (closer to the ground surface). Therefore, the horizontal force F acting on the side wall portion 54 of the common groove 50 is larger toward the upper side. For this reason, the rotation moment M arises in the common groove 50, and the common groove 50 rotates.

  However, as shown in FIG. 1, by providing the ground improvement wall 100 around the joint groove 50, the supply of soil (muddy water) to the lower side of the joint groove 50 during liquefaction is suppressed (FIG. 6). (See arrow K).

  Here, by providing the ground improvement wall 100 around the joint groove 50, the supply of soil (muddy water) to the lower side of the joint groove 50 is suppressed, and thereby the floating of the joint groove 50 is suppressed. However, as described above, a rotational moment M (see FIG. 6) is generated in the common groove 50 due to the dynamic earth pressure of the horizontal displacement during the earthquake. When the joint groove 50 is rotated by the rotation moment M, there is a possibility that partial lifting occurs.

  However, in the ground improvement wall 100 of the present embodiment, a substantially triangular tapered portion 112 whose width decreases toward the upper side is formed on the upper end portion 110 that is in contact with the side wall portion 54 of the joint groove 50.

  Since the horizontal force F acting on the side wall portion 54 of the joint groove 50 due to the dynamic earth pressure is determined by the ground spring, it depends on the wall thickness, the wall hardness, and the ground displacement. In other words, the ground displacement cannot be controlled because it is an external force, but the horizontal force can be controlled by changing the wall thickness or wall hardness. The tapered portion 112 of the ground improvement wall 100 according to the present embodiment is harder than the liquefied layer 12 and is thinner toward the upper side and thicker toward the lower portion. Therefore, the tapered portion 112 is formed on the side wall portion 54 of the joint groove 50 via the tapered portion 112. The applied horizontal force F is lower than the case where the tapered portion 112 is not interposed (see FIG. 6 and FIG. 7 for comparison). Therefore, the rotational moment M (refer FIG. 6) which arises in the common groove 50 reduces, and rotation of the common groove 50 is suppressed or prevented.

  Thus, by providing the ground improvement wall 100 of this embodiment around the joint groove 50, the supply of soil (muddy water) to the lower side of the joint groove 50 at the time of liquefaction during an earthquake is suppressed. Since the rotation of the common groove 50 is suppressed or prevented, the floating of the common groove 50 is more effectively suppressed or prevented.

[Modification]
Next, a modification of the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the ground improvement wall 150 of the modified example is formed so that it overlaps with the lower outer edge portion 52 in plan view around the joint groove 50, and the lower end portion 152 is rooted or settled in the support layer 14. As described above, it is constructed by a mechanical stirring method or a high-pressure jet stirring method.

  A step-like tapered portion 162 having a narrower width toward the upper side is formed on the upper end portion 160 in contact with the side wall portion 54 of the joint groove 50 of the ground improvement wall 150. Therefore, as in the above-described embodiment, the horizontal force F acting on the side wall portion 54 of the joint groove 50 via the step-like tapered portion 162 of the ground improvement wall 150 is greater than the case where the tapered portion 162 is not interposed. The horizontal force F on the lower side increases. Therefore, the rotational moment M generated in the common groove 50 at the time of the earthquake is reduced, and the rotation of the common groove 50 is suppressed or prevented.

<Second embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the member same as 1st embodiment, and the overlapping description is abbreviate | omitted.

(Construction)
As shown in FIG. 3, the ground improvement wall 200 of the present embodiment has the lower end portion 202 embedded in the support layer 14 around the joint groove 50 so as to overlap the lower outer edge portion 52 in plan view. Thus, it is constructed by a mechanical stirring method.

  A stabilizer 212 protruding outward is formed at the upper end portion 210 of the ground improvement wall 200 in contact with the side wall portion 54 of the common groove 50. The stabilizer 212 is formed so as to be on the lower side of the center position 54 </ b> P in the vertical direction of the side wall portion 54 of the common groove 50.

(Function and effect)
Next, the operation and effect of this embodiment will be described.

  By providing the ground improvement wall 200 around the common groove 50, supply of soil (muddy water) to the lower side of the common groove 50 during liquefaction is suppressed (see FIG. 6).

  Further, the horizontal force F acting on the side wall portion 54 of the joint groove 50 with which the stabilizer 212 formed on the upper end portion 210 of the ground improvement wall 200 contacts is increased by the stabilizer 212. Since the stabilizer 212 is formed so as to be on the lower side of the vertical center position 54P of the side wall 54, the horizontal force F acting on the lower side of the vertical center position 54P of the side wall 54. Becomes larger. Therefore, the rotational moment M generated in the common groove 50 is reduced. Further, the rotational resistance is increased by the stabilizer 212. Therefore, the rotation of the common groove 50 is effectively suppressed or prevented.

  Thus, by providing the ground improvement wall 200 of this embodiment around the joint groove 50, the supply of soil (muddy water) to the lower side of the joint groove 50 during liquefaction during an earthquake is suppressed. Since the rotation of the common groove 50 is suppressed or prevented, the floating of the common groove 50 is effectively suppressed or prevented.

[Modification]
Next, a modification of this embodiment will be described.

  In the stabilizer 212 of the present embodiment, the center position 54P in the vertical direction of the side wall portion 54 of the common groove 50 and the horizontal line GP passing through the center of gravity position G of the common groove 50 match or substantially match. Therefore, the rotational moment M is reduced by forming the stabilizer 212 so as to be below the center position 54P in the vertical direction of the side wall portion 54 of the common groove 50.

  However, when the vertical center position 54P of the side wall portion 54 of the common groove 50 and the horizontal line GP passing through the barycentric position G of the common groove 50 do not coincide or substantially coincide with each other, the horizontal line passing through the barycentric position G of the common groove 50 The stabilizer 212 is formed so that the horizontal force F acting on the lower part than the GP becomes larger.

<Third embodiment>
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the member same as 1st embodiment and 2nd embodiment, and the overlapping description is abbreviate | omitted.

(Construction)
As shown in FIG. 4, the ground improvement wall 300 of the present embodiment has the lower end portion 302 embedded in the support layer 14 around the joint groove 50 so as to overlap the lower outer edge portion 52 in plan view. Thus, it is constructed by a mechanical stirring method.

  A wide anchor portion 304 is formed at the lower end portion 302 of the ground improvement wall 300. In addition, the anchor part 334 and the anchor part 344 shown with the imaginary line (two-dot broken line) of a figure are mentioned later.

(Function and effect)
By providing the ground improvement wall 300 around the common groove 50, supply of soil (muddy water) to the lower side of the common groove 50 during liquefaction is suppressed (see FIG. 6).

  Further, the pulling resistance force and the pushing resistance force of the ground improvement wall 300 are increased by the anchor portion 304 formed at the lower end portion 302 of the ground improvement wall 300. Therefore, the restraint force of the ground improvement wall 300 with respect to the common groove 50 at the time of liquefaction becomes large, and rotation of the common groove 50 is suppressed.

  Thus, by providing the ground improvement wall 300 of the present embodiment around the joint groove 50, the supply of soil (muddy water) to the lower side of the joint groove 50 during liquefaction during an earthquake is suppressed. Since the rotation of the common groove 50 is suppressed or prevented, the floating of the common groove 50 is effectively suppressed or prevented.

[Modification]
Next, a modification of this embodiment will be described.

  In FIG. 4, the anchor portion 304 formed at the lower end portion 302 of the ground improvement wall 300 is completely embedded in the support layer 14, but is not limited to such a structure.

  A structure in which the lower side is embedded in the support layer 14 and the upper side is embedded in the liquefied layer 12 may be used, as in an anchor portion 334 indicated by an imaginary line (two-dot broken line) in FIG. In other words, the anchor portion 334 formed across the support layer 14 and the liquefied layer 12 may be used.

  Alternatively, a structure in which the bottom surface 344A is in contact with the support layer 14 like an anchor portion 344 indicated by an imaginary line (two-dot broken line) in FIG.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the member same as 1st embodiment-3rd embodiment, and the overlapping description is abbreviate | omitted.

(Construction)
As shown in FIG. 5, the ground improvement body 400 is constructed in the liquefied layer 12 below the joint groove 50. The ground improvement body 400 is constructed by injecting a water glass chemical into the liquefied layer 12 by boring or the like. The chemical injection method is a ground improvement method that reduces the water permeability of the ground or strengthens the ground by injecting a chemical into the ground to construct a ground improvement body. Since the chemical injection method is a well-known technique, detailed description thereof is omitted.

  The ground improvement body 400 according to the present embodiment has an inverted U-shape (a shape of a “mon” in Chinese characters) on the lower side, and a hollow portion 402 is formed.

  In addition, a hollow part said here is a site | part in which the ground improvement body is not formed without inject | pouring a chemical | medical solution in the ground. In other words, it is a ground portion that has not been improved with chemical solution, and a cavity (space) is not formed in the ground.

  A cast-in-place pile 420 in which the lower end 422 is embedded in the support layer 14 is provided outside the joint groove 50. A block body 430 made of reinforced concrete or the like is provided at the upper end portion of the pile 420 so as to be close to or in contact with the side wall portion 54 of the common groove 50. FIG. 5 illustrates a state in which the side wall portion 54 of the common groove 50 and the block body 430 are close to each other.

  In the present embodiment, the pile 420 and the block body 430 use an existing building foundation adjacent to the joint groove 50. When the block body 430 constituting the existing building foundation has a large gap with the side wall portion 54 of the common groove 50, concrete or the like may be placed to fill the gap.

(Function and effect)
Next, the operation and effect of this embodiment will be described.

  The ground improvement body 400 formed by injecting the chemical solution below the joint groove 50 suppresses liquefaction of the liquefied layer 12 below the joint groove 50 and suppresses the supply of soil. Moreover, the ground improvement body 400 can be formed at low cost by providing the cavity part 402. FIG. Therefore, the floating of the joint groove 50 when liquefied is suppressed at low cost.

  Further, the rotation of the common groove 50 is stopped by the pile 420 and the block body 430 provided outside the common groove 50.

  Thus, by providing the ground improvement body 400 of this embodiment under the common groove 50, liquefaction at the time of an earthquake is suppressed and supply of soil is suppressed at low cost. Furthermore, since the rotation of the common groove 50 is stopped by the pile 420 and the block body 430, the floating of the common groove 50 is effectively suppressed or prevented.

[Modification]
Next, a modification of this embodiment will be described.

  A structure in which the pile 420 and the block body 430 are not provided, in other words, the floating of the joint groove 50 may be suppressed or prevented only by the ground improvement body 400.

  Moreover, as shown in FIG. 5, the ground improvement body 400 constructed by injecting a chemical solution has an inverted U-shape (a shape of a “kanji” in Chinese characters) having an opening on the lower side, but is not limited thereto. Not.

  For example, a U-shaped (groove-shaped) ground improvement body whose upper side is the opening side may be used. Or the ground improvement body of rectangular frame shape (character shape of a "mouth" of a Chinese character) may be sufficient. Alternatively, it may be a ground improvement body having a structure having a cross in a rectangular frame (a character shape of “kanji” in Chinese characters). In short, it is only necessary that the cavity is formed within a range in which the desired effect of suppressing the floating of the common groove 50 is obtained.

<Others>
The present invention is not limited to the above embodiment.

  For example, in order to reduce the horizontal force F (dynamic earth pressure) acting on the upper side of the side wall portion 54 of the joint groove 50, an improved body (for example, urethane sponge) having a volume compression coefficient smaller (softer) than that of the liquefied layer 12. May be provided beside the upper side of the side wall portion 54 of the common groove 50.

  The above-described plurality of embodiments and modifications can be implemented in combination as appropriate. For example, you may form the anchor part 304 of 2nd embodiment in the lower end part 102 of the ground improvement wall 100 of 1st embodiment.

  Further, for example, an underground structure other than the common groove 50 may be used. It may be a culvert or an underpass.

  Moreover, in the said embodiment, although the ground 10 was comprised with two layers of the liquefied layer 12 and the support layer (non-liquid layer) 14 in order to make an explanation easy to understand, it is not limited to this. Each layer may be composed of a plurality of layers.

  Further, a configuration in which a liquefied layer and a support layer (non-liquid layer) are further provided below the support layer (non-liquid layer) 14 may be employed. In this case, the ground improvement wall may be constructed so as to reach the lower support layer (non-liquid layer). Moreover, when the ground improvement wall is constructed so as to reach the lower support layer (non-liquid layer), the anchor portion (wide portion) of the third embodiment is the upper support layer (non-liquid layer) 14. It may be constructed in a part corresponding to the above, may be constructed in a part corresponding to the lower support layer (non-liquid layer), or may be constructed in both.

  Furthermore, it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.

10 Ground 12 Liquefaction layer 14 Support layer (non-liquefaction layer)
50 Joint ditch (underground structure)
52 Lower outer edge portion 54 Side wall portion 100 Ground improvement wall 112 Tapered shape portion (tapered shape body, earth pressure adjusting means)
150 Ground improvement wall 162 Tapered part (tapered body, earth pressure adjusting means)
200 Ground improvement wall 212 Stabilizer (protruding part, earth pressure adjusting means)
300 Ground improvement wall 304 Anchor part (wide part)
334 Anchor part (wide part)
344 Anchor part (wide part)
400 Ground improvement body 420 Pile 430 Block body (rotation stop)

Claims (3)

A ground improvement wall constructed so as to overlap the lower outer edge of the underground structure embedded in the liquefied layer in a plan view and reach the non-liquefied layer below the liquefied layer;
Earth pressure adjusting means provided at the upper end portion of the ground improvement wall in contact with the side wall portion of the underground structure and increasing the earth pressure acting on the lower portion of the side wall portion due to horizontal ground displacement;
Improved ground structure. The earth pressure adjusting means is
It is formed at the upper end of the ground improvement wall and is a tapered body whose width becomes narrower toward the upper side.
The ground improvement structure according to claim 1. The earth pressure adjusting means is
Formed on the upper end of the ground improvement wall and projecting outward.
The ground improvement structure according to claim 1.