JP4968695B2 - Ground improvement structure - Google Patents

Description

  The present invention relates to a ground improvement structure for an inhomogeneous ground.

  Generally, when the ground of the planned construction site of a building is soft ground, for example, ground improvement as shown in Patent Documents 1 and 2 below is often performed. Thereby, the rigidity of the ground of the planned construction site can be improved, and the building can be constructed on the stable ground.

  By the way, in some grounds of the planned construction site, there are cases where underground structures such as foundations of existing buildings, underground structures, mines and the like exist. In this case, in the planned construction site, there are a buried region where the buried material is buried and a raw ground region where there is no buried material, and the ground of the planned construction site is heterogeneous. In such an inhomogeneous ground, the rigidity differs between the buried area and the original ground area, so uneven settlement is likely to occur, and the ground response at the time of the earthquake varies depending on the building plane position, making the building design complicated. In addition, building damage is likely to occur during an earthquake.

Therefore, conventionally, if the ground of the planned construction site is inhomogeneous, the buried area is excavated and the buried object is removed, and then the buried area is backfilled with a soil material that is easily compacted, such as sand or gravel. To homogenize the ground of the planned construction site. Then, if necessary, the ground is uniformly improved throughout the planned construction site, and then a building is constructed on the ground.
JP 2001-115444 A JP 11-256563 A

  However, the above-described conventional method has a problem that enormous amount, cost, and construction period are required to remove and backfill underground objects.

  The present invention has been made in consideration of the above-described conventional problems, and an object thereof is to provide a ground improvement structure and a ground improvement method capable of homogenizing a heterogeneous ground, reducing costs and shortening a construction period. It is said.

  The ground improvement structure according to the present invention is a ground improvement structure formed on a heterogeneous ground having an embedded area in which an underground object is embedded and an original ground area in which the underground object is not embedded. The first ground improvement body is formed in the original ground area, and the second ground improvement body different from the first ground improvement body is formed in the buried area, and the first ground improvement body is provided. Further, the distribution of the shear wave velocity in the depth direction is equal between the original ground region and the buried object region provided with the second ground improvement body.

  The buried area where the underground object is embedded has at least one of vertical rigidity and shear rigidity larger than the original ground area where the underground object is not embedded. With the ground improvement structure according to the invention, the vertical rigidity and shear rigidity of the original ground area and the buried object area after the ground improvement are equal without removing the buried object in the buried object area.

  In the ground improvement structure according to the present invention, it is preferable that the improvement rate of the buried object region by the second ground improvement body is smaller than the improvement rate of the original ground region by the first ground improvement body.

  Thereby, the distribution in the depth direction of the shear wave velocity in the original ground region is equivalent to the distribution in the depth direction of the shear wave velocity in the buried object region without changing the material for ground improvement.

  According to the ground improvement structure according to the present invention, since the vertical rigidity and shear rigidity of the original ground area and the buried object area after the ground improvement are equal, the heterogeneous ground can be homogenized. As a result, uneven settlement can be suppressed, and the ground response at the time of the earthquake can be simplified, thereby simplifying the design of the building and reducing the damage to the building at the time of the earthquake. In addition, since the original ground area and the buried object area can be homogenized without removing the buried object in the buried object area, the cost can be reduced and the construction period can be shortened.

Hereinafter, embodiments of the ground improvement structure according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a ground G to be ground improved, and FIG. 2 is a plan view showing a ground improving structure formed on the ground G.

First, the ground G targeted for ground improvement will be described.
As shown in FIGS. 1 and 2, the ground G to be improved in the present embodiment is a planned construction site of a building X, and is a heterogeneous ground in which underground buried objects 10 and 11 are buried. . More specifically, the ground G is a slag buried region 1 in which the slag 10 (corresponding to the underground buried object in the present invention) is buried, and an existing pile 11 (corresponding to the underground buried object in the present invention). Has an existing pile burial area 2 and an original ground area 3 in which underground buried objects such as the slag 10 and the existing pile 11 are not buried.

Next, the ground improvement structure created with respect to the ground G which consists of an above-described structure is demonstrated.
The ground improvement structure in the present embodiment is a structure in which soil is chemically consolidated by stirring and mixing solidified materials such as lime and cement in the ground G by a known consolidation method.
Specifically, as shown in FIG. 2, in the ground G in the original ground region 3 among the ground G, a wall-shaped ground improvement body 12 (corresponding to the first ground improvement body in the present invention). Are formed in a lattice shape in plan view. The ground improvement body 12 is a wall-like ground improvement body formed by continuously stirring and mixing soil and a consolidated material in the lateral direction.

In addition, since the slag buried region 1 has higher rigidity than the original ground region 3 because the slag 10 is embedded, the distribution of shear wave velocity in the depth direction is equivalent to that of the original ground region 3. In addition, the ground is improved at a lower improvement rate than the original ground region 3. More specifically, in the slag embedding area 1, a slag 10 having a certain volume exists, and both the vertical rigidity and the shear rigidity are high. Therefore, in the mine burial area 1, a pile-shaped ground improvement body 13 (corresponding to the second ground improvement body in the present invention) having a high vertical rigidity and a low shear rigidity and a wall-shaped ground improvement body 14 (this) Corresponds to the second ground improvement body in the invention). The pile-shaped ground improvement body 13 is a cylindrical ground improvement body, and the plurality of ground improvement bodies 13 are disposed around the slag 10 in plan view, and are disposed at intervals. . The wall-shaped ground improvement body 14 is formed to have the same width (wall thickness) as the lattice-shaped ground improvement body 12 in the original ground region 3 and the lattice-shaped ground improvement body 12 in the original ground region 3. Are arranged at wider intervals.
Note that the “improvement rate” in the present embodiment is that the volume of the entire target area (for example, the slag buried area 1) is 100, and the ground improvement body (for example, the pile-shaped ground improvement body 13 and the wall-shaped area) It means the ratio (%) of the total volume of the ground improvement body 14).

  Moreover, since the existing pile embedded region 2 has higher rigidity than the original ground region 3 because the existing pile 11 is embedded, the distribution of shear wave velocity in the depth direction is equivalent to that of the original ground region 3. Thus, the ground is improved at a lower improvement rate than the original ground region 3. That is, all the values of the shear wave velocity at the same depth at a plurality of different plane positions in the construction range are set within a range of ± 20% with respect to the average value thereof. For example, assuming that the shear wave velocity at a depth of 10 m at the points A, B, and C of the construction range is 250 m / s, 300 m / s, and 340 m / s, the average value at this time is 297 m / s, Since the range of ± 20% is 237 to 356 m / s, the points A (250 m / s), B (300 m / s), and C (340 m / s) are all within ± 20% of the average value. Will be in. Such a situation should continue from the ground surface to the ground depth to be examined. In addition, “the ground depth to be examined” means a depth at which the formation is uniform and the depth distribution of shear wave velocity can be regarded as equivalent. In addition, the plane range for evaluating the shear wave velocity is the minimum unit of the range surrounded by one span of the planned building (span = distance between the columns and the center of the column), and the range where one side is surrounded by five spans at the maximum. And In general, since one span is around 10 m, the plane range for evaluating the shear wave velocity is 10 m × 10 m to 50 m × 50 m. The construction range is divided into units, and the depth is increased for each range. Evaluate the shear wave velocity distribution in the vertical direction. The plane range is appropriately changed depending on the size of the buried part or obstacle, the distribution range, the distribution shape, and the like.

  More specifically, there are a plurality of existing piles 11 that are pile-like underground buried objects in the existing pile buried area 2, and in the existing pile buried area 2, the vertical rigidity is high and the shear rigidity is low. Therefore, a grid-like ground improvement body 15 (corresponding to the second ground improvement body in the present invention) having a large vertical rigidity and shear rigidity is formed in the existing pile burying region 2. The grid-like ground improvement bodies 15 are arranged at the same intervals as the grid-like ground improvement bodies 12 in the original ground area 3 described above, and are wider than the grid-like ground improvement bodies 12 in the original ground area 3 ( The wall thickness is small.

  According to the ground improvement structure having the above-described configuration, the vertical rigidity and shear of the slag buried area 1, the existing pile buried area 2 and the original ground area 3 after the ground improvement without removing the slag 10 and the existing pile 11 or the like. All of the rigidity is equivalent. Thereby, the heterogeneous ground G can be homogenized and the uneven settlement of the ground G can be suppressed. In addition, the ground response at the time of the earthquake is simplified, thereby making it possible to simplify the design of the building and reduce the damage to the building at the time of the earthquake. Moreover, since the slag burial area 1, the existing stake burial area 2 and the original ground area 3 can be homogenized without removing the slag 10 and the existing pile 11, the cost can be reduced and the construction period can be shortened. .

  Moreover, according to the ground improvement structure which consists of an above-described structure, the improvement rate of the slag embedding area | region 1 by the pile-shaped ground improvement body 13 and the wall-shaped ground improvement body 14 is the original ground area | region by the grid wall-like ground improvement body 12 3 and the improvement rate of the existing pile burying region 2 by the grid-like ground improvement body 15 is smaller than the improvement rate of the original ground region 3 by the grid-wall-like ground improvement body 12. Without changing the improved material, the distribution in the depth direction of the shear wave velocity in the raw ground region 3 is equivalent to the distribution in the depth direction of the shear wave velocity in the slag burial region 1 and the existing pile burial region 2. As a result, the ground improvement for the mine burial area 1 and the existing pile burial area 2 and the ground improvement for the original ground area 3 can be performed using the common equipment at the same time, and the work efficiency can be improved. Cost reduction and construction period reduction can be achieved.

As mentioned above, although embodiment of the ground improvement method which concerns on this invention was described, this invention is not limited to above-described embodiment, In the range which does not deviate from the meaning, it can change suitably.
For example, in the above-described embodiment, the wall-shaped ground improvement body 12 is formed in a lattice shape in the original ground area 3, but the ground improvement body formed in the original ground area in the present invention is the shape of the original ground area. It is possible to appropriately change the shape of the ground improvement body according to the geology, the wall-like ground improvement body may be arranged in a shape other than the lattice shape, or a pile shape, a block shape, etc. It may be a ground improvement body other than a wall shape. Moreover, in above-mentioned embodiment, the pile-shaped ground improvement body 13 and the wall-shaped ground improvement body 14 are created in the mine buried area 1, and the grid-like ground improvement body 15 is created in the existing pile buried area 2. However, the ground improvement body created in the buried object area in the present invention is appropriately changed according to the shape of the buried object area, the shape of the buried object (mineral 10 or existing pile 11), the size of the existence range, and the like. It is possible to use a ground improvement body such as a lattice wall shape, a wall shape other than that, a pile shape, or a block shape.

  Moreover, in above-mentioned embodiment, the depth of the shear wave velocity of each area | region 1-3 is made small by making the improvement rate in the slag embedding area 1 and the existing pile embedding area 2 smaller than the improvement rate in the original ground area 3. Although the distribution in the vertical direction is made equal, the present invention makes the distribution in the depth direction of the shear wave velocity in each region 1 to 3 without changing the improvement rate in each region 1 to 3. You may do it. For example, in the buried object region (mineral buried region 1, existing pile buried region 2), the ground can be improved by using a consolidated material different from the consolidated material used in the ground improvement of the original ground region 3. Specifically, by using a consolidated material having lower strength than the consolidated material used in the ground improvement of the original ground region 3 for the ground improvement of the buried object region, without changing the improvement rate in each region 1-3, The distribution in the depth direction of the shear wave velocity in each of the regions 1 to 3 can be made equal.

  In addition, in the range which does not deviate from the main point of this invention, it is possible to replace suitably the component in above-mentioned embodiment with a well-known component, and you may combine the above-mentioned modification suitably.

It is a perspective view of the heterogeneous ground for demonstrating embodiment of this invention. It is a top view of the ground improvement structure for demonstrating embodiment of this invention.

Explanation of symbols

1 Ore burial area (burial area)
2 Existing pile burial area (buried object area)
3 Original ground area 10 Mineral (burial)
11 Existing pile (buried)
12 Ground improvement body (first ground improvement body)
13 Ground improvement body (second ground improvement body)
14 Ground improvement body (second ground improvement body)
15 Ground improvement body (second ground improvement body)
G ground (heterogeneous ground)

Claims (2)

In the ground improvement structure created in a heterogeneous ground having an embedded area where the underground object is embedded and an original ground area where the underground object is not embedded,
A first ground improvement body is created in the original ground area, and a second ground improvement body different from the first ground improvement body is created in the buried object area,
The original ground region provided with the first ground improvement body and the buried object region provided with the second ground improvement body have the same distribution of shear wave velocity in the depth direction. Improved ground structure. In the ground improvement structure according to claim 1,
The ground improvement structure characterized by the improvement rate of the said embedded area | region by said 2nd ground improvement body being smaller than the improvement rate of the said original ground area | region by said 1st ground improvement body.

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