JP2019127793A - Sinkage suppression structure for sinkage suppression object - Google Patents

Abstract

To provide a sinkage suppression structure for sinkage suppression objects that is particularly superior in versatility by using a frame-like (grid-like) ground improvement wall and a partial ground improvement body at the same time as a configuration in which they are independent from each other.SOLUTION: The sinkage suppression structure for sinkage suppression objects is composed of a sinkage suppression object 1 supported on the ground 10, a frame-like ground improvement wall 2 built in the ground 10 so as to surround the sinkage suppression object 1 in plan view, and a partial ground improvement body 3 that is formed by partially improving, in a plate shape, the ground 10 between the outer surface of the sinkage suppression object 1 and the inner surface of the frame-like ground improvement wall 2 in plan view. The depth of the partial ground improvement body 3 is formed more shallowly than that of the frame-like ground improvement wall 2, and the partial ground improvement body 3 is provided away from the frame-like ground improvement wall 2. The partial ground improvement body 3 is formed rectangularly along the frame-like ground improvement wall 2 in plan view.SELECTED DRAWING: Figure 1

Description

  In the present invention, countermeasures for liquefaction are applied to the surrounding ground of a subsidence suppression object (in particular, a transport container such as a container, a detached house, a building structure such as a building, or a civil engineering structure such as embankment). , Belongs to the technical field of the sinking suppression structure of the sinking suppression object.

  If a building structure such as a detached house is constructed on the ground that is likely to liquefy (soft ground), or if it is planned to be constructed in the future, the ground will be liquefied during an earthquake disaster Therefore, the importance of realizing a liquefaction prevention structure (subsidence suppression structure) for ground treatment in advance so as to prevent damage such as settlement of a building structure or to reduce damage has already been known.

By the way, as the liquefaction preventing structure, a well known liquefaction preventing structure (the TFT method (registered trademark), etc.) is well known, in which a frame-like (grid) ground improvement wall is created to enclose the liquefaction preventing ground. It is about to
This frame-like (grid-like) ground improvement wall can improve the liquefaction preventing effect by narrowing the grid interval or enhancing the rigidity of the ground improvement wall. However, it has already been found that the effect is limited even if the rigidity of the ground improvement wall is increased, and if the lattice spacing is narrowed, the amount of improved soil increases and it becomes uneconomical, above all, the building structure Depending on the form of the (subsidence suppression object), there is a limit to the implementation of the frame-shaped (lattice-like) ground improvement wall alone.

  Therefore, for example, Patent Documents 1 and 2 disclose a technique in which a liquefaction countermeasure work that is based on a frame-like (lattice-like) ground improvement wall as described above and added various measures to this is added. .

  Specifically, in Patent Document 1, as shown in FIG. 1 and the like, the vertical solidified wall (10) having a height reaching from the upper end to the lower end of the liquefied layer is in a lattice shape in plan view. The vertical solidification wall is embedded in the non-liquefied layer (C) below the liquefied layer (S), and is formed into a general part (11) and a general part. The wall thickness of the upper part of the vertical solidified wall is constituted by the thickened part (12) formed in the upper part, and the wall thickness of the lower part is formed by the rectangular frame-like wall formed in plan view along the vertical solidified wall. A liquefaction countermeasure structure is disclosed which is characterized by being thicker than that (see claim 1 and the like).

  In Patent Document 2, as shown in FIG. 1 and the like, jet nozzles (31, 32) are inserted into a plurality of locations on the outer ground of the existing building (40), and the jet nozzle provided at the tip of the jet pipe A ground improvement body (10) formed by injecting a ground improvement material into an underground part of an existing building, and an outer peripheral wall portion (11) formed in the ground surrounding the existing building, and each outer peripheral wall The ground improvement body is characterized by comprising a buttress part (12) projecting from each outer peripheral wall part toward the substantially central part of the existing building continuously with the part (see claim 1 etc.). .

Japanese Patent No. 5698754 JP, 2013-189804, A

Since the technology according to Patent Document 1 can be implemented avoiding the settlement suppression object, the settlement suppression object on soft ground can be applied regardless of real estate (structure) and movable property (container), and new construction, It can be applied regardless of existing facilities.
However, since the thickened portion is integrally rigidly mounted on the frame-shaped ground improvement wall (corresponding to the general part of the vertical solidified wall) serving as the base described above, the thickened portion When the subsidence occurs, the general part of the main body deforms or subsides following this, and as a result, the entire vertical solidified wall (ground improvement wall) consisting of the general part and the thickened part is out of plane. The deformation may be increased, and the shear deformation suppressing effect may be reduced.
Further, since the vertically solidified wall is a so-called irregularly shaped ground improvement wall in which the general portion and the thickened portion are integrally formed, it is complicated in operation as well as in image analysis and structural design.

Since the technology according to Patent Document 2 can also be carried out while avoiding the object of subsidence suppression, the object of subsidence suppression on soft ground is a real estate (structure), 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 the buttress portion is integrally rigidly mounted on the frame-shaped ground improvement wall (corresponding to the outer peripheral wall portion) serving as the base described above, the technique according to the patent document 1 and Similarly, when the buttress portion sinks, the outer peripheral wall portion, which is the main body, deforms or sinks following this, resulting in the entire ground improvement body comprising the outer peripheral wall portion and the buttress portion. There was a possibility that the out-of-plane deformation increased and the shear deformation suppressing effect was lowered.
Further, since the ground improvement body is a so-called irregular ground improvement wall formed by integrating the outer peripheral wall portion and the buttress portion, it is complicated in operation as well as image analysis and structural design.

  The present invention has been devised in view of the problems of the background art described above, and the object of the present invention is to provide a frame-like (lattice-like) ground improvement wall and a plate-like partial ground improvement body, respectively. It is to provide a settlement restraining structure for a settlement restraining object that is particularly excellent in versatility, as well as being able to eliminate all of the problems related to Patent Documents 1 and 2 by using them together in an independent configuration.

  As means for solving the problems of the background art, a settlement restraining structure for a settlement restraining target object according to the invention described in claim 1 is a plan view of the settlement restraining target object supported on the ground and the ground. A frame-like ground improvement wall formed so as to surround the object of subsidence suppression, and a ground between the outer side surface of the object of subsidence suppression and the inner side surface of the frame-like ground improvement wall in plan view The partial ground improvement body is formed with a depth shallower than the frame-shaped ground improvement wall, and the partial ground improvement body is formed by partially improving the frame-like ground improvement wall. And spaced apart from each other.

  A second aspect of the present invention is the subsidence suppression structure for a subsidence suppression object according to the first aspect, wherein the partial ground improvement body is at least two of the frame-shaped ground improvement walls in plan view. It is characterized in that it is formed in a shape along the ground improvement wall.

  The invention described in claim 3 is the subsidence suppression structure of the subsidence suppression object according to claim 1 or 2, wherein the partial ground improvement body has an inner edge in plan view, the subsidence suppression object. It is formed by one or a combination of two or more of proximity, separation from the settlement suppression target object, and the settlement suppression target object and wrap.

  According to a fourth aspect of the present invention, in the subsidence suppression structure for a subsidence suppression object according to any one of the first to third aspects, the frame-shaped ground improvement wall has a depth that does not reach the non-liquefied layer. Is set in the following manner.

The subsidence suppression structure for a subsidence suppression object according to the present invention has the following effects.
(1) The effect of reducing the amount of subsidence of the subsidence suppression object by combining the frame-shaped ground improvement wall and the partial ground improvement body in an independent configuration is based on the experimental results and analysis results explained below. As is apparent, it was found that the frame-shaped ground improvement wall was improved as compared with the single construction. Furthermore, it was found that the amount of settlement can be reduced to 60% or less when no countermeasure is taken.
(2) Since the partial ground improvement body can be carried out without being joined to the settlement suppression object at all, the settlement suppression object is applicable not only to real estate such as housing but also, for example, storage for transportation of containers etc. It can be applied to container yards where the body is loaded.
(3) Since the partial ground improvement body is based on the concept that it is created by avoiding the settlement suppressing object in a plan view, the construction is suitably carried out not only for the existing structure but also for the construction of a new structure. it can.
(4) Since the partial ground improvement body is built (built) in an independent configuration separated from the frame-like ground improvement wall, the problems relating to the Patent Documents 1 and 2 do not occur either. That is, even if the partial ground improvement body sinks, there is no adverse effect such as deformation or sinking of the frame-shaped ground improvement wall. Therefore, the problem that the out-of-plane deformation of the entire frame-shaped ground improvement wall increases or the shear deformation suppressing effect is reduced does not occur.
(5) Since the partial ground improvement body and the frame-like ground improvement wall are independently constructed separately inside and outside, the image analysis and the structural design as well as the Patent Documents 1 and 2 are not limited. It is simple and easy, as the creation work can be clearly shared. In addition, the creation work of the partial ground improvement body and the frame-shaped ground improvement wall is excellent in flexibility, such as allowing a certain amount of time lag. In addition, renovation and repair work can be performed separately, so it has excellent flexibility.
(6) In summary, the present invention eliminates all the problems related to Patent Documents 1 and 2 by using a frame-like (lattice-like) ground improvement wall and a partial ground improvement body together in an independent configuration. Not only can it be done, but it is possible to realize the sinking suppression structure of the sinking suppression object which is particularly excellent in versatility.

A is the top view which showed Example 1 of the subsidence suppression structure of the subsidence suppression target object (illustration example is an aggregate | assembly of a container) which concerns on this invention, B is A BB arrow sectional drawing of A. is there. A is a plan view showing a variation of the first embodiment, and B is a cross-sectional view taken along the line B-B of A. A is the top view which showed the non-measures state which did not introduce the subsidence suppression means only by installing the subsidence suppression object on the ground (soft ground), and B is an elevational view. A is a plan view showing a state in which a frame-like (lattice-like) ground improvement wall is constructed from the state of FIG. 3, and B is a cross-sectional view taken along the line B-B of A. FIG. A is a table showing an experimental case (Case-A to C) of a centrifugal model vibration experiment, and B shows a time history of horizontal response acceleration measured by a Case-B shaking table in the experimental case. It is a graph, C is the table which showed the amount of settlement of the settlement control object (container) of the above-mentioned experiment case. AC is a meter arrangement | positioning figure which showed the said experimental case (Case-AC). A is an analysis model diagram, and B is an elevation cross-sectional view schematically showing each implementation of Case-1, 2 and 3 in the table of FIG. The symbol ▽ in the QQ sectional view of A indicates the groundwater level. It is the table | surface which put together the analysis result of the variation (Case-1-13) of the settlement suppression structure of the settlement suppression object which concerns on this invention. A to D are elevation sectional views schematically showing the implementation states of Case-9, 11, 12, and 13 in order in the table of FIG. It is a shear stress contour figure in the above-mentioned non-measure initial stress state. A to C are plan views schematically showing further variations of the settlement suppressing structure of the settlement suppressing object according to the present invention.

  Next, an embodiment of the settlement suppressing structure of the settlement suppressing object according to the present invention will be described based on the drawings.

  As shown in FIGS. 1A and 1B, the settlement restraining structure for a settlement restraining object according to the present invention includes the settlement restraining object 1 supported on the ground 10, and the settlement restraining in plan view in the ground 10. A frame-like ground improvement wall 2 formed so as to surround the object 1, and a ground 10 between the outer side surface of the subsidence suppression target object 1 and the inner side surface of the frame-like ground improvement wall 2 in plan view. The partial ground improvement body 3 is formed with a depth smaller than that of the frame-shaped ground improvement wall 2 and is partially improved. It is provided separately from the ground improvement wall 2.

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

  The settlement control target object 1 forms a plurality of containers 1a stacked and stacked in line in a container yard on the ground 10 as one assembly. Usually, the container 1a is continuously installed in the traveling direction of the portal container crane (usually the vertical direction in FIG. 1A). Subsidence suppression object for a set of 24 containers of 4m in depth, 12.2m in height and 2.6m in height, gathered in a total of 24 rows in 6 rows and 4 steps in the height direction at appropriate intervals in the width direction 1 is assumed.

The frame-shaped ground improvement wall 2 is continuously arranged in a grid shape in a state in which a columnar improvement body constructed by mixing and stirring a cement-based solidifying material in the ground (soft ground) 10 is overlapped between adjacent portions. It is constructed with the TOFT method (registered trademark).
The frame-shaped ground improvement wall 2 according to the illustrated example has a lattice spacing (lattice center spacing) L of 25 m in both length and width, a wall thickness of 1.0 m, and a height of 20.0 m (GL-1) which is the same as that of the liquefied layer S. 0.5m to GL-21.5m).

In the present embodiment, the partial ground improvement body 3 is formed in a rectangular shape (see hatched lines) along the frame-like ground improvement wall 2 in a plan view.
Further, the partial ground improvement body 3 is formed such that an outer surface 3a thereof is separated from the frame-like ground improvement wall 2 (inner side surface) by 0.3 m, and an inner side surface 3b thereof is viewed in plan view. In this case, it is formed close to (approximately flush with) the extent to which the object 1 for settlement control is in contact.
Furthermore, as shown in FIG. 1B, the partial ground improvement body 3 has a height dimension of 2.5 m (GL-1.5 m to GL-4.0 m), and the ground improvement of the frame-like ground improvement It is constructed with the same setting as wall 2 (groundwater level).
In addition, for the construction of the partial ground improvement body 3 having the above-described form, a known ground improvement method by mechanical stirring or jet stirring, or a method by chemical solution injection is appropriately adopted depending on the construction space or the like. Ru.

In summary, the present invention, as described above, in addition to creating a frame-like (lattice-like) ground improvement wall 2 by a known TOFT method (registered trademark) or the like on the ground surrounding the subsidence suppression object 1, This time, it is characterized in that a partial ground improvement body 3 of the above-mentioned form is introduced as a new auxiliary liquefaction countermeasure work.
The reason why the liquefaction countermeasure work for the partial ground improvement body 3 is newly added is, for example, the “shear stress contour diagram” shown in FIG.
This is because the initial stress state (see Fig. 3A and B) of the initial stress state (liquefied layer) is not established (refer to Figs. 3A and 3B) without setting the settlement suppressing means only by installing the settlement suppressing object (1) on the ground (10). FIG. 2 is a shear stress contour diagram (unit: kPa) in FIG. The groundwater level is GL-2.8m.
In FIG. 10, the initial shear stress is large from the end of the settlement suppression object (1) to the middle of the position where the frame-like ground improvement wall (2) enters (A part). On the other hand, the initial shear stress is small at the central portion (B portion) directly under the object of subsidence suppression. This indicates that the ground of the part A is in a state closer to the fracture surface in the initial state than the ground of the part B, since the initial shear stress by the self-weight of the object of settlement control is applied. .
Therefore, the present applicants have little influence on the settlement suppression effect even if an unimproved portion is left in the ground of the B portion that is far from the fracture surface in the initial state, and conversely, the location is close to the fracture surface. Partial improvement of the surface part of the ground of the part A significantly affects the settlement suppressing effect, and focusing on the fact that high effects can be obtained when used together with the frame-shaped ground improvement wall 2, the present proposal It is

  Applicants conducted a centrifugal model vibration experiment (60 G field) according to the configuration of Example 1 in order to confirm the operation and effect of the configuration of the invention described above. The details will be described below.

<Outline of centrifugal model vibration experiment>
FIG. 5A shows an experimental outline of five types (Case-A, Case-B (1), (2), Case-C (1), (2)). FIG. 6 shows a measurement device layout (scale: 1/60) corresponding to the five types.
Unless otherwise specified, the subsidence suppression object 1 is “container 1”, the frame-shaped ground improvement wall 2 is “lattice wall 2”, and the partial ground improvement body 3 is “plate-like improvement body 3”. It is written as The uniaxial compressive strength of the frame-shaped ground improvement wall 2 is 1500 kPa.
In FIG. 6, the lattice wall 2 has a horizontally long rectangular shape for convenience of illustration.

Specifically, the Case-A is a case in which no countermeasure is taken in that the subsidence suppression means is not introduced just by installing the container 1 on the ground 10 (see FIG. 3).
The Case-B (1) is a case in which the lattice wall 2 of the configuration according to the first embodiment is formed around the container 1 according to the Case-A (see FIG. 4).
The Case-B (2) has a plate-like shape on the inside of the lattice wall 2 according to the Case-B (1) with a height twice as high as that of the plate-like improved body 3 according to the first embodiment. This is a case where the partial ground improvement body 13 improved to (1) is created (see FIG. 2). The uniaxial compressive strength of the partial ground improvement body 13 is 150 kPa.
The Case-C (1) is a case in which the plate-like improved body 3 having the configuration according to the Example 1 is formed inside the lattice wall 2 according to the Case-B (1) (see FIG. 1). . The uniaxial compression strength of the plate-like modified body 3 is 800 kPa.
The Case-C (2) has the same outer shape (shape and dimensions) as the Case-B (2) (see FIG. 2), but the uniaxial compressive strength of the plate-like improved body 3 is 800 kPa. .

For the input ground motion in the experiment, seismic waves assuming the Nankai Trough were used.
FIG. 5B shows a time history of horizontal response acceleration measured with a Case-B shaking table. The maximum acceleration was 227 Gal.
As the container 1, the configuration according to Example 1 described above, that is, the container (width 2.4m, depth 12.2m, height 2.6m) is separated by 6 in the horizontal direction with appropriate intervals (0.3m in two places). A container model was created that models the state of four rows stacked in a row and height direction. The width of the container in the direction of vibration is 15.0 m, the width in the direction perpendicular to vibration is 12.2 m, and the height is 10.4 m. The container ground pressure is 42.89 kPa.
The groundwater level was set to GL-1.5 m as in Example 1. In the same manner 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 result and consideration>
FIG. 5C shows the amount of subsidence 1 (container) subsidence of the five types of Case-A, B, and C.
In addition, the settlement suppression effect at the time of using the lattice wall 2 and the plate-like modified body 3 according to the present invention in combination may be higher than the settlement suppression effect of only the lattice wall 2 alone, more preferably, the settlement amount without measures If it can be reduced to 60% or less, it can be said that there is a sufficient effect.

Based on the above, referring to the experimental results in FIG. 5C, the average unsettled amount of Case-A (see FIG. 3) is 0.641 m, whereas Case-B (1) (see FIG. 4). ) Has an effect of reducing the container settlement amount to 62% in the case of no countermeasure.
Furthermore, as in the configuration of the present invention, when using the lattice wall 2 according to Case-B (2) (see FIG. 2) and the plate-like modified body 3 in combination, the average amount of settlement is 0.252 m. The effect of reducing the amount to 39% in the case of no measures was recognized. That is, the effect of suppressing the amount of container settlement is enhanced by using the plate-like improved body 3 in combination.
Next, the average subsidence amount of Case-C (1) (see FIG. 1), which is the configuration of Example 1, is 0.255 m, and the effect of reducing the container subsidence amount to 40% in the case of no countermeasures. is there.
Next, the average amount of subsidence applied to Case-C (2) (see FIG. 2) is 0.178 m, and there is an effect of reducing the amount of container subsidence to 28% when no countermeasure is taken.

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

  Next, although the present inventors are a simple method compared with the said centrifugal model vibration experiment, they analyzed various about the form variation of the said partial ground improvement body 3. As shown in FIG.

<Overview of analysis>
(1)
FIG. 7A shows an analysis model used in a countermeasure study on a lattice wall 2 having a lattice interval of 25 m as a settlement suppression measure for the settlement suppression target 1 (container).
The groundwater level is GL-2.8m. The depth of the liquefied layer is 17.2 m (GL-2.8 m to GL-20.0 m). A non-liquefied layer (sand gravel layer) is provided immediately below the liquefied layer S.
In addition, the periphery of the container 1 having a contact pressure of 41.8 kPa is surrounded by the lattice wall 2 having a lattice spacing of 25 m. The improvement depth of the lattice wall 2 is 17.2 m (GL-2.8 m to GL-20.0 m), which is the same as that of the liquefied layer. The width of the lattice wall 2 is 0.9 m. The shear rigidity of the lattice wall 2 is 700,000 (kPa). The shear rigidity of the plate-like modified body 3 was set to 140,000 (kPa) which is 1/5 of the lattice wall 2.
FIG. 7B is an elevational cross-sectional view schematically showing implementation states of Cases 1 to 3 in analysis cases (Case-1 to 13) described later.
(Part 2)
FIG. 8 is a table summarizing examination results of analysis cases (Case-1 to Case 13) performed using the analysis model.
In the table of FIG. 8, “lattice interval” indicates the lattice center interval of the lattice wall 2. “Unmodified part (0.1 m in width)” or “Unmodified part (0.5 m in width)” is the distance between the inner surface of the lattice wall 2 and the outer surface of the plate-like improved body 3 (Do ) Is 0.1 m or 0.5 m (by the way, in Example 1, 0.3 m).
Further, “all in the lattice” indicates that the plate-like improved body 3 is formed in a plate shape covering the entire surface of the soft ground surrounded by the lattice wall 2 (see the right figure in FIG. 7B). As shown in FIG. 9B, “not applied to the container” is formed so that the inner side surface 3b of the plate-like improvement body 3 is close enough to be in contact with the container 1 in a plan view (substantially flush). Show that. “It takes 1 m under the container” indicates that the plate-like improvement body 3 is formed so as to overlap with the container 1 in a plan view as shown in FIG. 9A. Here, this lap is represented by a symbol L, and a separation distance (space) between a container 1 and a plate-like improvement body 3 described later is represented by a symbol Di.
(3)
In this analysis method for examining the settlement suppression measures effect, the shear rigidity of the liquefaction layer is reduced at a constant rate from the initial shear rigidity and the self weight analysis is performed, and the settlement suppression object 1 obtained from the self weight analysis result ( A simple method was used to evaluate the effect of subsidence suppression measures based on the amount of subsidence.
In the examination, the shear stiffness of the liquefaction layer was reduced to 1/300 of the initial shear stiffness. The liquefaction layer performs elasto-plastic analysis modeled by Mohr-Coulomb model.

<Discussion>
(Case-1)
A case is shown in which the container 1 is simply installed on the ground 10 and no countermeasures against settlement are introduced (see the left figure in FIG. 7B).
The amount of unsettled container settlement was 0.40 m as shown in the rightmost column of FIG.
(Case-2)
The case where the countermeasure of the lattice wall 2 of 25 m of lattice intervals is taken is shown from the said non-measure state (refer the center figure of FIG. 7B). The container subsidence amount was 0.30 m, and a reduction effect of 0.1 m was recognized compared with no countermeasures.
(Case-3)
For reference, a case where measures are taken together with the lattice wall 2 and a plate-shaped improved body (height dimension: 1.0 m: GL-2.8 m to GL-3.8 m) formed to cover the entire surface of the soft ground (See the right figure in FIG. 7B). The container subsidence amount was 0.15 m, and a reduction effect of 0.25 m was recognized compared with no countermeasure.
(Case-4)
For reference, the lattice wall 2 and the plate-like improvement body 3 (height dimension 2.2 m: GL-2.8 m to GL-5.0 m) are used in combination and rigidly connected to each other. The body 3 and the container 1 show a case where measures are taken so as to be substantially flush (see FIG. 9B) in plan view. The container subsidence amount was 0.16 m, and a reduction effect of 0.24 m was recognized compared with no countermeasure.

Case-5 to 13 described below each show a variation of the first embodiment according to the present invention.
As in the case of the above-mentioned centrifugal model vibration experiment, the container settlement amount of each variation may be higher than the settlement suppression effect (0.3 m of Case-2) of only the lattice wall 2 alone, and more preferably, no countermeasure If it can be reduced to 60% or less compared to the amount of settlement (0.4 m of Case-1), it is considered to be sufficiently effective.

(Case-5)
While the lattice wall 2 and the plate-like improvement body 3 (height dimension: 1.0 m: GL-2.8 m to GL-3.8 m) are used in combination and separated from each other by 0.1 m, the plate-like improvement body 3 And the container 1 has shown the case where the measure made into a substantially flush state (refer FIG. 9B) in planar view was performed.
The container subsidence amount was 0.18 m, and an effect of reducing it to 45% in the case of no measures was recognized. Therefore, it turned out that it is the structure applicable enough to this invention.
(Case-6)
The case where the height dimension of the plate-shaped improvement body 3 which concerns on said Case-5 was formed high from 1.0 m to 2.2 m (GL-2.8m-GL-5.0m) is shown.
The amount of container subsidence was 0.16 m, and an effect of reducing it to 40% when no countermeasure was taken was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
In addition, Case-6 and Case-4 only differ in whether they are rigid or not, and then the container settlement amount hardly changes from 0.16 m to the second decimal place, so the lattice wall It was found that there was no difference in the liquefaction countermeasure effect even if 2 and the plate-like improved body 3 were rigidly connected or separated by 0.1 m.
(Case-7)
The case where the height dimension of the plate-like improved body 3 which concerns on said Case-5 was formed high in 1.0 m-7.2 m (GL-2.8 m-GL-10.0 m) is shown.
The amount of container subsidence was 0.12 m, and an effect of reducing it to 30% when no countermeasure was taken was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
Moreover, Case-5, 6, 7 has only the difference whether the height dimension (improved thickness) of the plate-like modified body 3 is low or high, and in that case, the effect of reducing the amount of container settlement when the height dimension becomes high. Was found to be large.
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 body formed in a plate shape covering the entire soft ground with a height dimension of 1.0 m. (0.15 m) is almost equivalent to the lattice wall 2, when the plate-like improvement body 3 is used together, if the improvement depth (height dimension) of the plate-like improvement body 3 is appropriately set, the lattice wall It was found that the same effect as that obtained by constructing a plate-like improved body over the entire soft ground in No. 2 was obtained.

(Case-8 to Case-10)
The Case-8 to Case-10 are compared with the Case-5 to Case-7, and as shown in FIG. 9A, the partial ground improvement body 3 and the settlement suppression target object 1 in plan view It is different in that it is formed to be 1 m wrap L.
The amount of subsidence of each container is 0.17 m, 0.14 m, and 0.11 m in order, and the depth of the partial ground improvement body 3 is the same, and the flat improvement range is narrow. Case-5, Case-6, Case-7 It can be seen that the amount of subsidence of the containers is smaller by 0.1 to 0.2 m than in order.
From this, it can be seen that the subsidence suppression effect is higher than the case where the planar construction range of the partial ground improvement body 3 extends below the subsidence suppression object 1 and partially wraps it. In addition, the said lap | wrap part of the partial ground improvement body 3 is suitable for the ground improvement construction method by jet type stirring.

(Case-11)
Compared with the case 6 above, by increasing the separation distance (space) Do between the lattice wall 2 and the plate-like reformed body 3 from 0.1 m to 0.5 m, measures were taken to greatly reduce the improvement volume. The case is shown.
The amount of container subsidence was 0.16 m, and an effect of reducing it to 40% when no countermeasure was taken was recognized. Therefore, it turned out that it is the structure applicable enough to this invention.
In addition, as described above, Case-11 and Case-6 only differ from each other in that the separation distance is expanded from 0.1 m to 0.5 m, and in this case, the container settlement amount is 0. 0 for both decimal places. Since it hardly changed with 16 m, it turned out that the influence which it has on container settlement amount is small, even if the separation distance of the plate-shaped modifier 3 and the lattice wall 2 is extended to some extent.
(Case-12)
Compared with the case 6 above, the separation distance (space) Di between the container 1 and the plate-like improved body 3 is expanded from 0 (zero) to 0.5 m, and the improvement volume is largely reduced accordingly. Case is shown.
The container subsidence amount was 0.18 m, and an effect of reducing it to 45% in the case of no measures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
(Case-13)
Compared with Case-12, the case where the space Do is expanded from 0.1 m to 0.5 m, and a measure for greatly reducing the improved volume is shown.
The container subsidence amount was 0.18 m, and an effect of reducing it to 45% in the case of no measures was recognized. Therefore, it was found that the configuration is sufficiently applicable to the present invention.
Although the partial ground improvement body 3 according to Case 13 is separated by 0.5 m from the frame-shaped ground improvement wall 2 and by 0.5 m from the object 1 for suppressing settlement, Because it is much smaller than the container settlement amount (0.30 m) of this grid-like ground improvement alone, even if each of the above three has space Do and Di, they are used together with grid-like ground improvement (sinking suppression) It turned out that an effect could be obtained.

<Summary of added analysis>
Applicants then performed further analysis of the example variation.
(Additional analysis 1)
The additional analysis 1 is different from Case 6 in that the lower end of the lattice wall 2 is a short type not reaching the non-liquefied layer, and the other conditions are the same.
Specifically, the improvement depth of the lattice wall 2 according to the Case-6 is 17.2 m (GL-2.8 m to GL-20.0 m), which is the same as that of the liquefied layer. Although illustration is omitted, the improvement depth is set to 12.2 m (GL-2.8 m to GL-15.0 m).
As a result, it was found that the amount of container settlement was 0.162 m, which was almost the same as 0.16 m of Case-6.
Therefore, it has been found that the lattice wall 2 can obtain a good settlement suppression effect even when implemented at a depth that does not reach the liquefied layer.
(Additional analysis 2)
Subsequently, when the improvement depth of the lattice wall 2 is set to 7.2 m (GL-2.8 m to GL-10.0 m) under the same conditions as the additional analysis 1, as a result, the container settlement amount is 0. 0. 169 m, which was found to be almost the same as the case-6 0.16 m.
Therefore, it has been found that the grid wall 2 can obtain a good settlement suppressing effect even if the depth does not reach the liquefaction layer as well as about half the distance to the liquefaction layer.

(Additional analysis 3)
In this additional analysis 3, as shown in FIG. 11A, the plate-like improvement body 3 is not rectangular, but is parallel to two opposite ground improvement walls of the lattice wall 2 as shown in FIG. 11A. The only difference is that it is formed into a shape, and the other conditions are the same.
The amount of container settlement is 0.225 m, which is larger than the above Cases 5 to 13, but it is higher than the settlement suppressing effect of only the lattice wall 2 (0.3 m of Case 2), and no countermeasure Compared with the amount of subsidence (Case-1 0.4 m), it was found to have a subsidence suppression effect because it was reduced to 56% and 60% or less.
Thus, embankment is mentioned as a suitable application example at the time of forming plate-like improvement object 3 in parallel shape. Since the embankment has a shape characteristic that the load applied to the central part is larger than the both ends (the fore end part), the embankment (the object of settlement suppression 1) is not less than 1 m in plan view. It is preferable to form and implement a wrap (wider than in the case of a container).
(Additional analysis 4)
This additional analysis 4 is compared with the case 6 and, as shown in FIG. 11B, the plate-like improved body 3 is not rectangular, and ground improvement in two orthogonal directions of the lattice wall 2 in plan view Only the point which is formed in the substantially L shape along a wall differs, and others are the same conditions.
The amount of container settlement is 0.203 m, which is larger than the above Cases 5 to 13, but it is higher than the settlement suppressing effect of only the lattice wall 2 (0.3 m of Case 2), and no countermeasure Compared to the amount of subsidence (Case-1 0.4 m), it was found to have a subsidence suppressing effect because it was reduced to 51% and 60% or less.
In addition, although analysis is omitted, as shown in FIG. 11C, even if the plate-like 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 settlement suppression effect as in FIGS. 11A and 11B.

The embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to the illustrated examples, and variations of design changes and application that a person skilled in the art normally performs without departing from the technical idea thereof. Note that it includes the range.
By the way, when the subsidence suppression object 1 is composed of a container 1a, the container 1a is normally installed continuously in the traveling direction of the portal container crane (usually the vertical direction in FIG. 1A). In that case, temporary removal of the container 1a is required at a key place (the interference site between the container 1a and the frame-shaped ground improvement wall 2 and the partial improvement unit 3).

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

Claims (4)

A subsidence suppression object supported on the ground,
A frame-like ground improvement wall constructed so as to surround the settlement suppressing object in plan view in the ground;
It consists of a partial ground improvement body formed by partially improving the ground between the outer side surface of the settlement control object and the inner side surface of the frame-like ground improvement wall in plan view,
The partial ground improvement body is formed to be shallower than the frame-like ground improvement wall, and is provided apart from the frame-like ground improvement wall, the settlement of the settlement suppressing object Suppression structure.   2. The settlement suppression according to claim 1, wherein the partial ground improvement body is formed in a shape along at least two ground improvement walls among the frame-shaped ground improvement walls in a plan view. Structure that suppresses settlement of objects.   The partial ground improvement body is close to the extent that the inner edge of the partial ground improvement body is in contact with the subsidence suppression object in plan view, separated from the subsidence suppression object, and any of the subsidence suppression object and lap The sinking suppression structure of the sinking suppression object according to claim 1 or 2, characterized in that it is formed of one or two or more combinations.   The said frame-shaped ground improvement wall is set to the depth which does not reach a non-liquefaction layer, The settlement suppression of the settlement suppression target object of any one of Claims 1-3 characterized by the above-mentioned. Construction.