JP7108416B2 - Subsidence control structure for subsidence control object - Google Patents

Description

The present invention applies liquefaction countermeasures to the surrounding ground of subsidence suppression objects (particularly, transport containers such as containers, detached houses, architectural structures such as buildings, or civil engineering structures such as embankments). , belongs to the technical field of subsidence control structures for subsidence control objects.

If building structures such as detached houses are built on ground that may liquefy (soft ground), or if there are plans to build them in the future, the ground will liquefy in the event of an earthquake. The importance of realizing a liquefaction prevention structure (subsidence control structure) that treats the ground in advance is already known, so that the building structure will not suffer damage such as subsidence due to rain or the damage can be reduced.

By the way, as the liquefaction prevention structure, a well-known liquefaction prevention structure (TOFT construction method (registered trademark), etc.) in which a frame-shaped (lattice-shaped) ground improvement wall is created to enclose the ground to be liquefied prevention is well known. I'm in the middle of the day.
This frame-shaped (grid-shaped) ground improvement wall can improve the liquefaction prevention effect by narrowing the grid spacing or increasing the rigidity of the ground improvement wall. However, it is already known that even if the rigidity of the soil improvement wall is increased, the effect is limited. There was a limit to the implementation of the frame-shaped (lattice-shaped) soil improvement wall alone, such as the possibility that it could not be implemented depending on the form of the (subsidence suppression object).

Therefore, for example, Patent Documents 1 and 2 disclose techniques based on the frame-shaped (lattice-shaped) ground improvement wall as described above, and adding various devised liquefaction countermeasures to it. .

Specifically, in Patent Document 1, as shown in FIG. The vertical solidification wall is embedded in the non-liquefaction layer (C) under the liquefaction layer (S), and the general section (11) and the general section The wall thickness of the upper part of the vertical solidified wall is increased by the wall thickness of the lower part due to the rectangular frame-shaped wall formed along the vertical solidified wall. A liquefaction countermeasure structure is disclosed, which is characterized in that it is thicker than the liquefaction prevention structure (see claim 1, etc.).

In patent document 2, as shown in FIG. Therefore, a soil improvement body (10) formed by injecting a soil improvement material into the underground portion of an existing building, the outer peripheral wall portion (11) formed in the ground surrounding the existing building, and each outer peripheral wall A ground improvement body characterized by comprising a buttress part (12) continuously protruding from each outer peripheral wall part toward a substantially central part of the existing building (see claim 1 etc.) .

Japanese Patent No. 5697854 JP 2013-189804 A

Since the technology according to Patent Document 1 can be implemented while avoiding the subsidence control object, it can be applied regardless of whether the subsidence control object on soft ground is real estate (structure) or movable property (container). Applicable regardless of existing facilities.
However, since it is a configuration in which the thickened part is integrally rigidly connected to the frame-shaped ground improvement wall (corresponding to the general part of the vertical solidified wall) that serves as the base, the thickened part When the subsides, the general part, which is the main body, also deforms or subsides, and as a result, the entire vertical solidified wall (soil improvement wall) consisting of the general part and the thickened part is out of plane There is a risk that the deformation will increase and the effect of suppressing shear deformation will decrease.
In addition, since the vertical solidified wall is a deformed ground improvement wall that integrates the general portion and the thickened portion, image analysis, structural design, and work are complicated.

Since the technique according to Patent Document 2 can also be implemented while avoiding the subsidence suppression target object, the subsidence suppression target object on soft ground is real estate (structure) or movable property (container), as in the technology according to Patent Document 1. It can be applied regardless of whether it is new or existing.
However, since it is a configuration in which the buttress portion is integrally and rigidly connected to the frame-shaped ground improvement wall (corresponding to the outer peripheral wall portion) that serves as the base, the technology according to Patent Document 1 and Similarly, when the buttress part sinks, the outer peripheral wall part, which is the main body, also deforms or sinks following this, and as a result, the whole soil improvement body consisting of the outer peripheral wall part and the buttress part Out-of-plane deformation may increase, and the effect of suppressing shear deformation may decrease.
In addition, since the soil improvement body is a deformed soil improvement wall formed by integrating the outer peripheral wall portion and the buttress portion, image analysis and structural design as well as work are complicated.

The present invention has been devised in view of the above-mentioned problems of the background art, and the purpose thereof is to provide a frame-shaped (grid-shaped) soil improvement wall and a plate-shaped partial soil improvement body, respectively. It is an object of the present invention to provide a subsidence suppressing structure for a subsidence suppressing object that is particularly excellent in versatility, as well as being able to solve all the problems related to Patent Documents 1 and 2 by using them together in an independent configuration.

As a means for solving the problems of the background art, the settlement suppression structure for a settlement suppression object according to the invention described in claim 1 comprises a settlement suppression object supported on the ground and a plan view in the ground. A frame-shaped ground improvement wall constructed so as to surround the subsidence suppression target, and the ground between the outer surface of the subsidence suppression target and the inner surface of the frame-shaped ground improvement wall in plan view is partially improved into a plate shape, and is provided apart from the partial soil improvement body, and the partial ground improvement body is the frame-shaped It is characterized in that it is formed shallower in depth than the ground improvement wall of , and is provided apart from the frame-shaped ground improvement wall.

The invention recited in claim 2 is the settlement suppression structure for the settlement suppression target object recited in claim 1, wherein the partial ground improvement body is, in plan view, at least two of the frame-shaped ground improvement walls. It is characterized by being formed in a shape along the ground improvement wall.

The invention described in claim 3 is the settlement suppression structure for the settlement suppression object according to claim 1 or 2, wherein the partial ground improvement body has an inner edge that is, in plan view, the settlement suppression object It is characterized by being formed by any one or a combination of two or more of: close enough to contact with the object, separated from the object to be subsidence, and the object to be subsidence and the wrap.

The invention according to claim 4 is the subsidence control structure of the subsidence control object according to any one of claims 1 to 3, wherein the frame-shaped soil improvement wall is deep enough not to reach the non-liquefaction layer. It is characterized in that it is set to

ADVANTAGE OF THE INVENTION According to the subsidence suppression structure of the subsidence suppression target object which concerns on this invention, there exist the following effects.
(1) By using the frame-shaped ground improvement wall and the partial ground improvement body together in an independent configuration, the effect of reducing the amount of settlement of the settlement suppression target is based on the experimental results and analysis results described below. As is clear, it was found to be improved compared to the independent construction of the frame-shaped ground improvement wall. Furthermore, it was found that the amount of subsidence could be reduced to 60% or less of the amount without countermeasures.
(2) Since the partial ground improvement body can be implemented without joining the subsidence control object at all, the subsidence control object can be applied to real estate such as houses, as well as transportation accommodation such as containers It is also fully applicable in container yards where bodies are loaded.
(3) The partial ground improvement body is based on the concept of creating it while avoiding the subsidence control object in plan view, so it is suitable for existing structures as well as new structures. can.
(4) Since the partial soil improvement body is created (constructed) in an independent configuration separated from the frame-shaped soil improvement wall, the problems related to Patent Documents 1 and 2 do not occur. That is, even if the partial soil improvement body subsides, the frame-shaped soil improvement wall is not affected by any adverse effects such as deformation or subsidence. Therefore, problems such as an increase in out-of-plane deformation of the entire frame-shaped ground improvement wall and a decrease in the effect of suppressing shear deformation do not occur.
(5) Since the partial ground improvement body and the frame-shaped ground improvement wall are constructed independently inside and outside, compared to Patent Documents 1 and 2, not only image analysis and structural design It is simple and easy, such as clear division of construction work. In addition, the construction work of the partial soil improvement body and the frame-shaped soil improvement wall is excellent in flexibility, such as allowing a certain amount of time lag. In addition, repair work and repair work can be done separately, so it is highly flexible.
(6) In summary, the present invention solves all the problems related to Patent Documents 1 and 2 by using a frame-shaped (lattice-shaped) ground improvement wall and a partial ground improvement body in an independent configuration. It is possible to realize a subsidence control structure for a subsidence control object that is particularly excellent in general versatility.

1 is a plan view showing Example 1 of a subsidence suppression structure for a subsidence suppression target object (an assembly of containers in the illustrated example) according to the present invention, and B is a cross-sectional view taken along the line BB of A. FIG. be. A is a plan view showing a variation of the first embodiment, and B is a cross-sectional view taken along line BB of A. FIG. A is a plan view showing a non-measured state in which a subsidence suppression target is only installed on the ground (soft ground) and no subsidence suppression means is introduced, and B is an elevation view of the same. A is a plan view showing a state in which a frame-shaped (lattice-shaped) ground improvement wall is created from the state of FIG. A is a table showing the experimental cases (Case-A to C) of the centrifugal model vibration experiment, and B shows the time history of the horizontal response acceleration measured on the shaking table of Case-B among the experimental cases. It is a graph and C is the table|surface which showed the subsidence amount of the subsidence suppression target object (container) of the said experiment case. A to C are measuring instrument layout diagrams showing the experimental cases (Case-A to C). A is an analysis model diagram, and B is a cross-sectional elevational view schematically showing the implementation status of Case-1, 2, and 3 in the table of FIG. The symbol ▽ in the QQ sectional view of A indicates the groundwater level. 4 is a table summarizing analysis results of variations (Case-1 to Case-13) of subsidence suppression structures of subsidence suppression objects according to the present invention. 8A to 8D are vertical cross-sectional views schematically showing the implementation status of Case-9, 11, 12 and 13 in order in the table of FIG. It is a shear stress contour diagram in the initial stress state without countermeasures. 7A to 7C are plan views schematically showing further variations of the subsidence suppression structure of the subsidence suppression target object according to the present invention.

Next, an embodiment of a subsidence suppression structure for a subsidence suppression target object according to the present invention will be described with reference to the drawings.

As shown in FIGS. 1A and 1B, the subsidence suppression structure for a subsidence suppression object according to the present invention includes a subsidence suppression object 1 supported on the ground 10 and the subsidence suppression structure in the ground 10 in plan view. A frame-shaped ground improvement wall 2 constructed so as to surround the object 1, and the ground 10 between the outer surface of the subsidence suppression object 1 and the inner surface of the frame-shaped ground improvement wall 2 in plan view. is partially improved into a plate shape, and the subsidence suppression object 1 and the partial soil improvement body 3 are provided apart from each other, and the part The target ground improvement body 3 is formed to have a shallower depth than the frame-shaped ground improvement wall 2 and is provided apart from the frame-shaped ground improvement wall 2 .

The ground 10 has a groundwater level of GL-1.5m, a depth of the liquefaction layer S of 20.0m (GL-1.5m to GL-21.5m), and a non-liquid It is a soft ground with a layer (for example, a crushed stone layer) T.

The object 1 for subsidence suppression is an aggregate of a plurality of containers 1a arranged and stacked in a container yard on the ground 10. As shown in FIG. Normally, the containers 1a are continuously installed in the traveling direction of a gate-type container crane (generally, the vertical direction in FIG. 1A). A total of 24 containers 1a with a size of 4m, 12.2m in depth, and 2.6m in height are gathered in 6 rows with appropriate intervals in the width direction and 4 stages in the height direction. 1.

The frame-shaped ground improvement wall 2 is constructed by mixing and stirring a cement-based solidification material in the ground (soft ground) 10, and the column-shaped improvement bodies are continuously arranged in a grid-like state in an overlapping state between adjacent ones. It is built with the TOFT construction method (registered trademark).
The frame-shaped ground improvement wall 2 according to the illustrated example has a grid spacing (grid center spacing) L of 25 m both vertically and horizontally, a wall thickness of 1.0 m, and a height of 20.0 m, which is the same as the liquefaction layer S (GL-1 .5m to GL-21.5m).

In this embodiment, the partial soil improvement body 3 is constructed in a rectangular shape (see oblique lines) along the frame-shaped soil improvement wall 2 in plan view.
In addition, the partial soil improvement body 3 has an outer surface 3a formed with a distance of 0.3 m from (the inner surface of) the frame-shaped soil improvement wall 2, and an inner surface 3b that is formed in a plan view. , it is constructed close to the object 1 for subsidence suppression (substantially flush).
Furthermore, the partial ground improvement body 3 has a height dimension of 2.5 m (GL-1.5 m to GL-4.0 m), as shown in FIG. It is constructed at the same level as the wall 2 (groundwater level).
In addition, for the construction of the partial soil improvement body 3 of the above-described form, a ground improvement method by known mechanical stirring or injection stirring, or a method by chemical injection is appropriately adopted and carried out according to the construction space. be.

In summary, as described above, in the present invention, in addition to creating a frame-shaped (lattice-shaped) ground improvement wall 2 by a known TOFT construction method (registered trademark) or the like on the ground around the subsidence suppression target 1, It is characterized by newly introducing the partial soil improvement body 3 of the above form as a new auxiliary liquefaction countermeasure work.
The basis for newly adding the liquefaction countermeasure work of the partial soil improvement body 3 is, for example, the "shear stress contour diagram" shown in FIG.
This is the initial stress state (shear stiffness of the liquefaction layer is reduced to 1/300) is a shear stress contour diagram (unit: kPa). The groundwater level is GL-2.8m.
In FIG. 10, the initial shear stress is large from the end of the subsidence control object (1) to the middle of the position where the frame-shaped ground improvement wall (2) enters (A part). Conversely, the initial shear stress is small at the central portion (B portion) immediately below the subsidence suppression object. This indicates that the ground of the A section is in a state closer to the fracture surface than the ground of the B section in the initial state, because the initial shear stress due to the weight of the subsidence suppression target is acting. .
Therefore, the present applicants have found that even if an unimproved portion is left in the ground of the B section, which is located far from the fracture surface in the initial state, it has little effect on the subsidence suppression effect, and conversely, it is located close to the fracture surface. Partially improving the surface layer of the ground in the A part has a large effect on the effect of suppressing settlement, and when used in combination with the frame-shaped ground improvement wall 2, a high effect can be obtained, leading to this proposal. It was.

The present applicants conducted a centrifugal model vibration experiment (60G field) in accordance with the configuration of Example 1 in order to confirm the effects of the configuration of the invention described above. A specific description will be given below.

<Overview of centrifugal model vibration test>
FIG. 5A shows an outline of the experiment for five types (Case-A, Case-B (1), (2), Case-C (1), (2)). FIG. 6 shows a measuring instrument arrangement diagram (scale: 1/60) corresponding to the five types.
Hereinafter, unless otherwise specified, the subsidence control object 1 is the "container 1", the frame-shaped ground improvement wall 2 is the "lattice wall 2", and the partial ground improvement body 3 is the "plate-shaped improvement body 3". is written as The uniaxial compressive strength of the frame-shaped soil improvement wall 2 is 1500 kPa.
Also, in FIG. 6, for convenience of illustration, the grid wall 2 has a laterally long rectangular shape.

Specifically, Case-A is a case where the container 1 is simply placed on the ground 10 and no subsidence control means is introduced (see FIG. 3).
Case-B(1) is a case in which the lattice wall 2 having the configuration according to the first embodiment is formed around the container 1 of Case-A (see FIG. 4).
The Case-B(2) has a plate-like shape with a height twice as high as that of the plate-like improved body 3 having the configuration according to the first embodiment, inside the lattice wall 2 of the Case-B(1). This is a case in which a partial ground improvement body 13 that has been improved is created (see FIG. 2). The uniaxial compressive strength of the partial soil improvement body 13 is 150 kPa.
Case-C(1) is a case in which the plate-shaped improved body 3 having the configuration according to Example 1 is formed inside the lattice wall 2 of Case-B(1) (see FIG. 1). . The uniaxial compressive strength of the plate-shaped improved body 3 is 800 kPa.
Case-C (2) has the same external shape (form and dimensions) as Case-B (2) (see FIG. 2), but the plate-shaped improved body 3 has a uniaxial compressive strength of 800 kPa. .

For the input seismic motion of the experiment, we used the seismic wave that assumed the Nankai Trough.
FIG. 5B shows the time history of the horizontal response acceleration measured by the shaking table of Case-B. Maximum acceleration was 227 Gal.
As the container 1, the configuration according to the first embodiment, that is, 6 containers (width 2.4 m, depth 12.2 m, height 2.6 m) are arranged in the horizontal direction at appropriate intervals (2 places of 0.3 m). We made a container model that modeled the state of stacking four layers in the row and height direction. The width of the container portion in the excitation direction is 15.0 m, the width in the orthogonal direction to the excitation direction is 12.2 m, and the height is 10.4 m. Moreover, the container ground pressure is 42.89 kPa.
The groundwater level was set at GL-1.5m as in Example 1 above. As in Example 1, the liquefied layer was GL-1.5 m to GL-21.5 m, and a model ground was prepared with Dr (relative density) = 70%.

<Experimental results and discussion>
FIG. 5C shows the amount of subsidence of subsidence suppression object 1 (container) in the five types of Case-A, B, and C.
The effect of suppressing settlement when the grid wall 2 and the plate-shaped improved body 3 according to the present invention are used in combination should be higher than the effect of suppressing settlement of the grid wall 2 alone, and more preferably, the amount of settlement without countermeasures. If it can be reduced to 60% or less, it can be said that it is sufficiently effective.

Based on the above, referring to the experimental results in FIG. 5C, the average settlement amount without countermeasures for Case-A (see FIG. 3) is 0.641 m, while Case-B (1) (see FIG. 4 ) is 0.396 m, which is effective in reducing the container settlement amount to 62% of the case without countermeasures.
Furthermore, as in the configuration of the present invention, when the lattice wall 2 and the plate-shaped improved body 3 of Case-B (2) (see FIG. 2) are used together, the average settlement amount is 0.252 m, and the container settlement The effect of reducing the amount to 39% of the case of no measures was recognized. That is, by using the plate-shaped improved body 3 together, the effect of suppressing the amount of container subsidence is enhanced.
Next, the average amount of settlement of Case-C (1) (see FIG. 1), which is the configuration of Example 1, is 0.255 m, and the effect of reducing the amount of container settlement to 40% of the case without countermeasures is achieved. be.
Next, the average settlement amount for Case-C (2) (see Fig. 2) is 0.178 m, which is effective in reducing the settlement amount of containers to 28% of the amount without countermeasures.

In addition, since the uniaxial compressive strength of the plate-shaped improved body 3 of Case-C is higher than that of Case-B, when the improvement depth of the plate-shaped improved body 3 is the same, the higher the strength of the plate-shaped improved body 3, The subsidence suppression effect of the subsidence suppression object 1 (container) is high.
Since the uniaxial compressive strength of the plate-shaped improved body 3 of Case-C is the same, the deeper the improvement depth of the plate-shaped improved body 3, the higher the settlement suppression effect of the subsidence suppression object 1 (container).

Next, the applicants conducted various analyzes on the morphological variations of the partial soil improvement body 3, although the method was simpler than the centrifugal model vibration experiment.

<Overview of analysis>
(Part 1)
FIG. 7A shows an analysis model used in examining countermeasures for a grid wall 2 with a grid interval of 25 m as subsidence control measures for a subsidence control object 1 (container).
The groundwater level is GL-2.8m. The depth of the liquefaction layer is 17.2m (GL-2.8m to GL-20.0m). There is a non-liquefaction layer (gravel layer) immediately below the liquefaction layer S.
The container 1 with a ground pressure of 41.8 kPa is surrounded by a grid wall 2 with a grid spacing of 25 m. The improvement depth of the grid wall 2 is 17.2m (GL-2.8m to GL-20.0m), which is the same as the liquefaction layer. The width of the grid wall 2 is 0.9 m. The shear stiffness of the lattice wall 2 is 700,000 (kPa). The shear rigidity of the plate-shaped improved body 3 was 1/5 of that of the grid wall 2, ie, 140,000 (kPa).
FIG. 7B is a cross-sectional elevational view schematically showing the implementation status of each of Case-1 to Case-3 among analysis cases (Case-1 to 13) to be described later.
(Part 2)
FIG. 8 is a table summarizing the examination results of analysis cases (Case-1 to 13) performed using the analysis model.
In the table of FIG. 8, "lattice interval" indicates the lattice center interval of the lattice wall 2. In FIG. “With unimproved portion (width 0.1 m)” or “with unimproved portion (width 0.5 m)” is the separation distance (Do ) is 0.1 m or 0.5 m (0.3 m in Example 1).
Further, "all inside the grid" indicates that the plate-shaped improved body 3 is formed in a plate shape covering the entire surface of the soft ground surrounded by the grid wall 2 (see the right figure in FIG. 7B). "Does not cover the container" means that the inner surface 3b of the plate-shaped improved body 3 is formed close enough to touch the container 1 (substantially flush) in a plan view, as shown in FIG. 9B. indicates that there is "1 m below the container" indicates that the plate-shaped improved body 3 is formed so as to overlap the container 1 by 1 m in plan view, as shown in FIG. 9A. Here, this wrap is denoted by L, and the separation distance (space) between the container 1 and the plate-shaped improved body 3, which will be described later, is denoted by Di.
(Part 3)
In this analysis method for examining the effect of subsidence control measures, the shear stiffness of the liquefaction layer is reduced at a constant rate from the initial shear stiffness, and the self-weight analysis is performed. A simple method was used to evaluate the effect of subsidence control measures based on the amount of subsidence of containers).
In the study, the shear stiffness of the liquefied layer was reduced to 1/300 of the initial shear stiffness. The liquefaction layer is subjected to elastoplastic analysis modeled by the Mohr-Coulomb model.

<Discussion>
(Case-1)
It shows a case where the container 1 is only installed on the ground 10 and no countermeasures are taken (see the left diagram of FIG. 7B).
The amount of container subsidence without countermeasures was 0.40 m, as shown in the rightmost column of FIG.
(Case-2)
A case is shown in which countermeasures are taken for the lattice wall 2 with a lattice interval of 25 m from the non-measured state (see the center diagram of FIG. 7B). The sinking amount of the container was 0.30m, and a reduction effect of 0.1m was recognized compared to no measures.
(Case-3)
For reference, a case where countermeasures were taken in combination with lattice wall 2 and a plate-shaped improved body (height dimension 1.0m: GL-2.8m to GL-3.8m) that covers the entire surface of the soft ground. (see right diagram in FIG. 7B). The sinking amount of the container was 0.15m, and a reduction effect of 0.25m was recognized compared to no measures.
(Case-4)
For reference, the lattice wall 2 and the plate-shaped improvement body 3 (height: 2.2 m: GL-2.8 m to GL-5.0 m) are used together, and both are rigidly connected, while the plate-shaped improvement The body 3 and the container 1 show a case in which countermeasures are taken to make them substantially flush with each other in plan view (see FIG. 9B). The sinking amount of the container was 0.16m, and a reduction effect of 0.24m was recognized compared to no countermeasures.

Cases-5 to 13 described below each show a variation of the first embodiment according to the present invention.
The container subsidence amount of each variation should be higher than the subsidence suppressing effect of the lattice wall 2 alone (0.3 m of Case-2), as in the case of the centrifugal model vibration experiment, and more preferably, no countermeasures are taken. Compared to the amount of settlement (0.4m in Case-1), if it can be reduced to 60% or less, it is considered to be sufficiently effective.

(Case-5)
A lattice wall 2 and a plate-shaped improved body 3 (height: 1.0 m: GL-2.8 m to GL-3.8 m) are used together, and the two are separated by 0.1 m, while the plate-shaped improved body 3 and the container 1 show a case in which countermeasures are taken to make them approximately flush with each other in plan view (see FIG. 9B).
The sinking amount of the container was 0.18m, and the effect of reducing it to 45% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
(Case-6)
This shows a case in which the plate-shaped improved body 3 according to Case-5 is formed as high as 1.0 m to 2.2 m (GL-2.8 m to GL-5.0 m).
The sinking amount of the container was 0.16m, and the effect of reducing it to 40% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
In addition, the only difference between Case-6 and Case-4 is whether or not they are rigidly connected. It was found that there is no difference in the anti-liquefaction effect between 2 and plate-shaped improved body 3, whether they are rigidly connected or separated by 0.1 m.
(Case-7)
This shows a case in which the plate-shaped improved body 3 according to Case-5 is formed as high as 1.0 m to 7.2 m (GL-2.8 m to GL-10.0 m).
The sinking amount of the container was 0.12m, and the effect of reducing it to 30% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
In Case-5, 6, and 7, the only difference is whether the height dimension (improved thickness) of the plate-shaped improved body 3 is low or high, and if the height dimension is increased, the effect of reducing the container settlement amount was found to grow.
Furthermore, the container settlement amount (0.16 m) of Case-6 with a height dimension of 2.2 m is the container settlement amount of the improved plate-shaped container that covers the entire surface of the soft ground with a height dimension of 1.0 m. (0.15 m). It was found that an effect equivalent to that of constructing a plate-shaped improvement body on the entire surface of the soft ground in 2 can be obtained.

(Case-8 to Case-10)
Compared to Case-5 to Case-7, Case-8 to Case-10 are compared with the above-mentioned Case-5 to Case-7, and as shown in FIG. The difference is that they are formed so as to be 1 m lap L.
The settlement amount of each container is 0.17m, 0.14m, 0.11m in order, Case-5, Case-6, Case-7 where the depth of the partial soil improvement body 3 is the same and the planar improvement range is narrow. It can be seen that the amount of settlement of the container is 0.1 to 0.2 m smaller than in the order.
From this, it can be seen that the subsidence suppression effect is higher when the planar construction range of the partial soil improvement body 3 extends below the subsidence suppression object 1 and partially lapped than when not lapped. It should be noted that the lap portion of the partial soil improvement body 3 is preferably a ground improvement method using jet stirring.

(Case-11)
Compared to Case-6, the separation distance (space) Do between the lattice wall 2 and the plate-shaped improved body 3 was increased from 0.1 m to 0.5 m, thereby greatly reducing the improved volume. showing the case.
The sinking amount of the container was 0.16m, and the effect of reducing it to 40% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
In addition, as mentioned above, the only difference between Case-11 and Case-6 is that the separation distance is increased from 0.1m to 0.5m. Since the distance is almost the same as 16 m, it was found that even if the separation distance between the plate-shaped improved body 3 and the grid wall 2 is widened to some extent, the influence on the amount of container settlement is small.
(Case-12)
Compared to Case-6, the distance (space) Di between the container 1 and the plate-shaped improved body 3 was expanded from 0 (zero) to 0.5 m, and measures were taken to greatly reduce the improved volume accordingly. case.
The sinking amount of the container was 0.18m, and the effect of reducing it to 45% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
(Case-13)
Compared to Case-12, the space Do is expanded from 0.1 m to 0.5 m, and the improvement volume is greatly reduced accordingly.
The sinking amount of the container was 0.18m, and the effect of reducing it to 45% of the case without countermeasures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
The partial ground improvement body 3 related to this Case-13 is separated from the frame-shaped ground improvement wall 2 by 0.5 m, and the subsidence control object 1 is also separated by 0.5 m. Since it is much smaller than the settlement amount (0.30 m) of the container for the grid-like ground improvement alone, even if the three parties have spaces Do and Di, it is used in combination with the grid-like ground improvement (settlement suppression). It was found to be effective.

<Overview of added analysis>
Applicants then performed additional analyzes of further example variations.
(Additional analysis 1)
This additional analysis 1 differs from Case-6 in that the lower end of the lattice wall 2 is a short type that does not reach the non-liquefied layer, and the other conditions are the same.
Specifically, the improvement depth of the lattice wall 2 for Case-6 is 17.2 m (GL-2.8 m to GL-20.0 m), which is the same as the liquefaction layer, whereas in the additional analysis, Although not shown, the improved depth was set at 12.2m (GL-2.8m to GL-15.0m).
As a result, it was found that the amount of settlement of the container was 0.162m, which is almost the same as the Case-6 of 0.16m.
Therefore, it was found that even if the grid wall 2 is set to a depth that does not reach the liquefaction layer, a good effect of suppressing subsidence can be obtained.
(Additional analysis 2)
Subsequently, under the same conditions as in the additional analysis 1, when the improvement depth of the grid wall 2 is set to 7.2m (GL-2.8m to GL-10.0m), the container subsidence amount is 0.2m. It is 169m, which is almost the same as 0.16m for Case-6.
Therefore, it was found that the grating wall 2 can obtain a good subsidence suppressing effect not only at a depth that does not reach the liquefaction layer, but also at a depth that is about half the distance to the liquefaction layer.

(Additional analysis 3)
In this additional analysis 3, compared to Case-6, as shown in FIG. The only difference is that they are shaped, and the other conditions are the same.
The amount of settlement of the container is 0.225m, which is larger than Cases 5 to 13, but it is higher than the effect of suppressing the settlement of the lattice wall 2 alone (0.3m of Case-2). Compared with the amount of settlement (0.4m of Case-1), it was 56%, which is less than 60%, so it was found that there is an effect of suppressing settlement.
An embankment is a suitable example of application when the plate-shaped improved bodies 3 are formed in a parallel shape in this way. The embankment has a shape characteristic that the load applied to the central portion is larger than that of both ends (bottom of the slope). It is preferably formed and implemented as a wrap (wider than in a container).
(Additional analysis 4)
In this additional analysis 4, compared with Case-6, as shown in FIG. The only difference is that they are formed in a substantially L shape along the wall, and the other conditions are the same.
The amount of settlement of the container is 0.203m, which is larger than Cases 5 to 13, but is higher than the effect of suppressing the settlement of the grid wall 2 alone (0.3m of Case-2). Compared to the amount of settlement (0.4 m in Case-1), it was found to be 51%, which is less than 60%, and thus has an effect of suppressing settlement.
In addition, although the analysis is omitted, as shown in FIG. 11C, even if the plate-shaped improved body 3 is formed in a U shape in plan view and implemented, the improved volume is larger than that in FIGS. 11A and 11B. Therefore, it can be easily inferred that there is at least the same degree of subsidence suppression effect as that shown in FIGS. 11A and 11B.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the illustrated examples, and is subject to design changes and application variations that are normally made by those skilled in the art without departing from the technical idea of the present invention. Just a reminder to include ranges.
Incidentally, when the subsidence suppression target object 1 is composed of a container 1a, the container 1a is usually installed continuously in the traveling direction of a gate-type container crane (normally, the vertical direction in FIG. 1A). In that case, it is necessary to temporarily remove the container 1a at important points (interference between the container 1a and the improvement part of the frame-shaped soil improvement wall 2 and the partial soil improvement body 3).

1 Subsidence control object (container)
1a Container 2 Frame-shaped ground improvement wall (lattice wall)
3 Partial soil improvement body (plate-shaped improvement body)
13 Partial soil improvement body (plate-shaped improvement body)
10 ground

Claims (4)

a subsidence suppression object supported on the ground;
a frame-shaped ground improvement wall constructed in the ground so as to surround the subsidence suppression target in plan view;
A partial ground improvement body formed by partially improving the ground between the outer surface of the subsidence suppression object and the inner surface of the frame-shaped ground improvement wall in a plan view,
The subsidence suppression object and the partial soil improvement body are provided apart, and the partial soil improvement body is formed shallower than the frame-shaped ground improvement wall, and the frame A subsidence control structure for a subsidence control object, characterized in that the subsidence control structure is provided at a distance from a ground improvement wall having a shape. The subsidence suppression according to claim 1, wherein the partial soil improvement body is formed in a shape along at least two soil improvement walls of the frame-shaped soil improvement wall in plan view. Subsidence control structure of the object. The partial ground improvement body, in a plan view, has an inner edge that is close enough to touch the subsidence control object, separated from the subsidence control object, or wrapped around the subsidence control object. 3. The subsidence suppression structure for a subsidence suppression object according to claim 1, wherein the subsidence suppression structure is formed by one or a combination of two or more. The frame-shaped ground improvement wall is set to a depth that does not reach the non-liquefaction layer, settling suppression of the settlement suppression object according to any one of claims 1 to 3 structure.

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