Methods for reinforcing soft ground

Abstract

To provide a soft ground reinforcing device which uses wood so that no curing period is required until solidification, allowing for quick construction and immediate use of structures such as embankments after construction, which is lightweight so that the structures can be easily removed when no longer needed without promoting deformation or subsidence of the soft ground, and furthermore, which uses lightweight reinforcing materials so that a large amount of material can be transported at once, thereby reducing transportation costs, and which is easy to design while improving adhesion and flatness during construction, and a reinforcing method therefor.SOLUTION: In the reinforcing device, a first structure 4 formed by laying a plurality of first base plate materials 6 arranged in the same direction on a soft ground 2 at any interval (spacing≥0), and a second structure 5 formed by laying a plurality of second base plate materials 8 approximately perpendicular to a longitudinal direction of the first base plate materials 6 at any interval (spacing≥0) are formed, and the formed second structure 5 is stacked on the first structure 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a soft ground reinforcement device and a reinforcement method thereof used for liquefaction countermeasures and soft cohesive ground countermeasures when constructing structures such as roads, parking lots, grounds, sidewalks, evacuation passages, railways, and streetcars.

Background Art

[0002] In recent years, efforts have been made to create forests underground while promoting construction projects, contributing to climate change mitigation by reducing greenhouse gas emissions (carbon stock technology). Here, trees absorb carbon dioxide in the atmosphere through photosynthesis and generate oxygen and carbon. The generated oxygen is released into the atmosphere, and the carbon is taken in and stored for the growth of the trees. Thus, forests play a role in reducing carbon dioxide, the main cause of global warming, and fixing it without releasing it into the atmosphere.

[0003] Carbon stock technology is characterized by performing construction projects such as liquefaction countermeasures and soft cohesive ground countermeasures using a ground improvement technology that uses a large amount of wood over a long period, and at the same time, reducing greenhouse gas emissions through material substitution energy-saving effects and carbon storage effects by using wood, and constructing a climate change mitigation, forestry regeneration, and safe and secure society.

[0004] Conventional liquefaction countermeasures and soft cohesive ground countermeasures used a construction method of solidifying and improving using a cement-based solidifying material such as cement when the improvement depth of the ground was up to the middle layer of about GL-2m. Also, temporarily, there were construction methods such as spreading steel plates or suppressing ground deformation with geotextiles. Furthermore, in order to reduce the load, there were cases such as spreading expanded polystyrene (EPS) or spreading logs vertically and horizontally on a raft and driving logs outside (Japanese Patent No. 3939320).

[0005] However, using cement-based solidification materials presented several challenges, including: (1) the need for a curing period before solidification; (2) contamination of the groundwater level due to the release of hexavalent chromium and the resulting alkalinity of the soil; (3) the increased mass of the solidified material itself, which promotes settlement; (4) the generation of greenhouse gases during cement production; and (5) the inability to remove the material once it is no longer needed.

[0006] Furthermore, when laying down steel plates or similar materials, there were several challenges: (1) they were only for temporary use, (2) they were heavy and difficult to handle, making large-scale transportation impossible, (3) their weight promoted subsidence, and (4) greenhouse gases were generated during the manufacturing of the steel plates.

[0007] When using geotextiles to suppress ground deformation, there were several challenges: (1) the geotextiles themselves deform, so a certain degree of deformation must be tolerated; (2) the manufacturing process uses a large amount of fossil fuels, resulting in a significant environmental impact; and (3) the materials are expensive.

[0008] When using expanded polystyrene (EPS) as a base layer, there were several challenges: (1) it was difficult to fix the EPS pieces together; (2) it was lightweight and therefore floated during floods; (3) it required a lot of fossil fuels, resulting in a high environmental impact; (4) it required a lot of energy to manufacture, and the EPS turned into microplastics, which also had a high environmental impact; and (5) the material was expensive.

[0009] When laying logs on a raft, there were several challenges: (1) it was difficult to construct the desired shape because the logs had an unstable shape; (2) laying the logs was time-consuming; (3) gaps formed between the logs, making them susceptible to decay; and (4) securing the logs to vertically driven piles and using tie rods was expensive. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 3939320 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Thus, the present invention was devised to address the aforementioned conventional problems, and aims to provide a soft ground reinforcement device and method that uses wood for the board material, eliminating the need for a curing period until solidification, thus enabling faster construction, ensuring immediate trafficability, allowing immediate use of structures such as embankments after construction, not contaminating groundwater, being lightweight so as not to promote deformation or settlement of soft ground, not generating greenhouse gases during the manufacture of the board material, being easily removed when the structure is no longer needed, and furthermore, because the reinforcing material is lightweight, large quantities of material can be transported at once, thereby reducing transportation costs and minimizing environmental impact, while also allowing long-term storage of carbon fixed in the wood underground, significantly reducing costs compared to conventional materials, and providing a soft ground reinforcement device and method that enhances adhesion and flatness during construction, is resistant to freezing, and is easy to design. [Means for solving the problem]

[0012] The present invention A first structure is formed by a plurality of first foundation plates made of wood arranged in the same direction and laid at arbitrary intervals (interval ≥ 0), and the interval between adjacent first foundation plates is set to an interval that ensures sliding safety. The second structure is formed by a plurality of second base plates made of wood laid approximately perpendicular to the longitudinal direction of the first base plate and at arbitrary intervals (interval ≥ 0), and the intervals between adjacent second base plates are also set to an interval that ensures sliding safety. A second structure is stacked on top of the first structure to form a reinforcing device, the formed reinforcing device is placed between the soft ground and the embankment, and the buoyancy of the reinforcing device is set to the value obtained by subtracting the dry mass of the reinforcing device from the saturated mass of the soft ground, and a load having a load greater than or equal to the buoyancy is placed on the reinforcing device. The depth from the groundwater level to the ground surface of the soft ground was measured, and the height from the groundwater level to the saturated volumetric water content of the embankment was measured to be the height of the capillary head. Based on these measurement results, when the reinforcing device is laid on the soft ground, and when embankment is piled on the surface on which the reinforcing device is laid, the height from the groundwater level to the top of the reinforcing device is made smaller than the height of the capillary head to the saturated volumetric water content of the embankment, so that the reinforcing device is below the groundwater level, and the aim is to prevent decay of the reinforcing device made of wood. It is characterized by the following: or Multiple first foundation slabs made of wood arranged in the same direction and laid at arbitrary intervals (interval ≥ 0), and a smooth surface formed by embedding and compacting sand or gravel between the first foundation slabs and the soft ground. 1st structure In addition to forming this, the distance between each of the adjacent first base plate materials is set to a distance that ensures sliding safety, The second structure is formed by a plurality of second base plates made of wood laid approximately perpendicular to the longitudinal direction of the first base plate and at arbitrary intervals (interval ≥ 0), and the intervals between adjacent second base plates are also set to an interval that ensures sliding safety. A second structure is stacked on top of the first structure to form a reinforcing device, the formed reinforcing device is placed between the soft ground and the embankment, and the buoyancy of the reinforcing device is set to the value obtained by subtracting the dry mass of the reinforcing device from the saturated mass of the soft ground, and a load having a load greater than or equal to the buoyancy is placed on the reinforcing device. The depth from the groundwater level to the ground surface of the soft ground is measured, and the height from the groundwater level when the volumetric water content of the embankment is saturated is measured to be the height of the capillary water head. Based on these measurement results, when the reinforcing device is laid on the soft ground, and when the embankment is piled on the surface on which the reinforcing device is laid, the height from the groundwater level to the top of the reinforcing device is made smaller than the height of the capillary water head when the volumetric water content of the embankment is saturated. In addition, the gaps between the sand and gravel materials embedded to create the smooth surface are raised by capillary action, raising the groundwater level so that the reinforcing device is below the groundwater level, thereby preventing decay of the reinforcing device made of wood. characterized in that or said First structure and second structure is formed by stacking three or more stages alternately and is characterized by the above.

Advantages of the Invention

[0013] According to the present invention, by using wood for the plate material, no curing period is required until solidification. Therefore, the construction is fast, and trafficability can be ensured immediately. Structures such as embankments after the construction can be used immediately. Without polluting groundwater, being lightweight, it does not promote the deformation or settlement of soft ground. Also, no greenhouse gas is generated during the manufacture of the plate material. When the structure becomes unnecessary, it can be easily removed. Furthermore, since the reinforcing material is lightweight, a large amount of materials can be transported at one time, thereby reducing the transportation cost, minimizing the environmental load, and storing the carbon fixed in the wood in the ground for a long time. It can suppress the cost much more than the conventional material cost. While enhancing the adhesion and flatness during construction, it is also resistant to freezing and has the effect that the design can be easily carried out.

Brief Description of the Drawings

[0014] [Figure 1] It is an explanatory drawing (1) explaining the schematic configuration of the reinforcing device of the present invention. [Figure 2] It is an explanatory drawing (2) explaining the schematic configuration of the reinforcing device of the present invention. [Figure 3] It is an explanatory drawing explaining the calculation formula for calculating the slip safety factor. [Figure 4] It is an explanatory drawing (1) explaining the method for reinforcing soft ground using the reinforcing device of the present invention. [Figure 5] It is an explanatory drawing (2) explaining the method for reinforcing soft ground using the reinforcing device of the present invention. [Figure 6] It is an explanatory drawing (3) explaining the method for reinforcing soft ground using the reinforcing device of the present invention.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. FIG. 1 and FIG. 2 are diagrams showing the schematic configuration of the reinforcing device 1 of the present invention. As is clear from the cross-sectional views of FIG. 1 and FIG. 2, the reinforcing device 1 is laid between a soft ground 2 and a structure such as an embankment 3.

[0016] The reinforcing device 1 of the present invention is basically configured such that a first structure 4 laid on the soft ground 2 is the first stage, and a second structure 5 laid on the first structure 4 is the second stage. Note that sand or gravel material 10 may be laid between the first structure 4 and the soft ground 2, and the first structure 4 may be installed on the sand or gravel material 10.

[0017] As understood from FIG. 1, the first structure 4 is composed of a plurality of first base plates 6. And the first base plates 6 are formed by continuously joining a plurality of plate units 7 in the longitudinal direction of the plate units 7. Here, the joint portion between the plate units 7 becomes a joint 9.

[0018] And, similarly to the first structure 4, the second structure 5 is composed of a plurality of second base plates 8, and the second base plates 8 are formed by continuously joining a plurality of plate units 7 in the longitudinal direction of the plate units 7. Here too, the joint portion between the plate units 7 becomes a joint 9.

[0019] Here, the plate unit 7 is, for example, a wood or a woody material having a longitudinal length of about 2 m or more, and having the same thickness and lateral width. The thickness of the plate unit 7 is about several cm to 20 cm, and in this embodiment, the thickness of the plate unit 7 is about 9 cm.

[0020] Therefore, depending on the scale of the construction site, multiple board units 7 are joined together to adjust the length in the longitudinal and transverse directions. During construction, using long, board-shaped materials of uniform thickness made of wood or wood-based material makes handling easier, improves adhesion between boards, enhances flatness, simplifies design, allows for large-scale transportation, facilitates on-site processing, reduces carbon dioxide emissions, and enables carbon sequestration.

[0021] Furthermore, it is preferable to use a single sheet of material with a large surface area that has sufficient thickness to ensure bending rigidity and shear resistance against vertical loads when the sheet material unit 7 is laid out. Examples include sheet materials made by sawing logs into planks, and CLT (cross-laminated timber).

[0022] Next, an embodiment of the reinforcement device 1 of the present invention will be described based on Figure 1. The first structure 4 is constructed by arranging multiple first base plate materials 6 facing the same direction and laying them at predetermined intervals, for example, at equal intervals. While it is conceivable to lay the multiple first base plate materials 6 at equal intervals, it is not necessarily required to do so. They can be laid at any interval (interval > 0) that ensures sliding stability in the design. In the embodiment shown in Figure 1, the first base plate materials 6 are arranged laterally, and the intervals between the first base plate materials 6 are such that sliding stability is ensured in the design.

[0023] Furthermore, the second structure 5 is laid with a plurality of second base plate materials 8 positioned substantially perpendicular to the longitudinal direction of the first base plate material 6 that constitutes the first structure 4, and at predetermined intervals, for example, at equal intervals. Similarly to the above, the laying of the plurality of second base plate materials 8 could be done by laying multiple second base plate materials 8 at equal intervals, but it is not necessarily required to lay them at equal intervals, and they can be laid at any interval (interval > 0) that ensures sliding stability in the design. In the embodiment shown in Figure 1, the second base plate materials 8 are arranged in a direction substantially perpendicular to the first base plate material 6, i.e., in the vertical direction, and the plurality of second base plate materials 8 are laid at any interval (interval > 0) that ensures sliding stability in the design.

[0024] The overlapping state of the first structure 4 and the second structure 5 is formed to be roughly in the shape of a grid. In this case, it is preferable to lay the second foundation plate material 8 so that the joint portion 9 of the first foundation plate material 6 does not overlap with the joint portion 9 of the first foundation plate material 6. That is, the basic principle is to overlap the laying plane of the second foundation plate material 8 from above with the joint portion 9 of the first foundation plate material 6 that constitutes the first structure 4. However, this is not required if there is a margin in the design.

[0025] By overlapping them in this way, the strength of the reinforcing structure is maintained while the flat surface of one plate material is superimposed on the joint 9 of the other, resulting in a structure where steps are less likely to occur at the joint 9.

[0026] Next, an embodiment of the reinforcing device 1 of the present invention will be described based on Figure 2. Figure 2 shows the state in which the spacing between the plate materials is shortest (arbitrary spacing = 0) according to the design. In the embodiment shown in Figure 2, multiple first base plate materials 6 are laid in contact with each other in the width direction to form the first layer of the first structure 4. In this case, it is preferable that the contact state of the multiple first base plate materials 6 in the width direction be arranged such that the joint portions 9 of the first base plate materials 6 that are in contact with each other do not lie on the same straight line. This is because it increases strength and rigidity while also improving the adhesion between the plate materials.

[0027] Then, a plurality of second foundation plates 8 are laid on the first structure 4, approximately perpendicular to the longitudinal direction of the first foundation plate 6. When laying them, the plurality of second foundation plates 8 are laid in contact with each other in the width direction to form the second structure 5. In this case as well, it is preferable that the contact state of the plurality of second foundation plates 8 in the width direction is arranged such that the joint portions 9 of the second foundation plates 8 that are in contact with each other do not lie on the same straight line.

[0028] As with the embodiment in Figure 1, the first structure 4 is formed as described above, and when stacking the second structure 5, which is the second layer, on top of the formed first structure 4, the second base plate 8 is laid so that the joint 9 of the first base plate 6 does not overlap with the joint 9 of the second base plate 8. As explained above, this maintains the strength of the reinforcing structure, and since the flat surface of the other plate overlaps the joint 9 of one plate, it is less likely to create a step at the other joint 9.

[0029] In the embodiment shown in Figure 2, compared to the embodiment shown in Figure 1, the first foundation plate material 6 is laid over the entire surface of the soft ground 2 to form the first structure 4, and then the second foundation plate material 8 is laid over the entire surface of the first structure 4 to form the second structure 5. Therefore, the strength is higher than when the reinforcing device 1 is arranged in a roughly grid pattern as in the embodiment shown in Figure 1, and the way in which the first structure 4 and the second structure 5 are assembled will be appropriately determined according to the construction site.

[0030] Incidentally, one of the features of the present invention is that the reinforcing device 1 is designed so as not to float up due to the buoyancy of the reinforcing device 1, and also so as not to cause sliding failure of the structure installed on the reinforcing device 1.

[0031] The reinforcement device 1 of the present invention has a structure that combines the first structure 4 and the second structure 5 using wood or wood-based material. Therefore, it is necessary to consider the buoyancy of the wood in the vertical one-dimensional direction (depth direction) and design the structure so that the superimposed load, i.e., the structure is loaded, is greater than or equal to the buoyancy of [saturated mass of soft ground - dry mass of reinforcement device 1]. The reason for using the dry mass of the reinforcement device 1 here is that the design is carried out assuming the most dangerous conditions.

[0032] Here, we will explain how to calculate the safety factor for slippage based on Figure 3. In this embodiment, the cohesion c of the soil (in this case, the embankment) is replaced with the shear resistance of the plate material, i.e., the thickness of the plate material (plate material unit 7) used in the present invention, and the calculation is performed assuming that only the plate material in the direction parallel to the expected sliding failure of the embankment and the portion that has been sliding failed is present in the embankment, and that the plate material present in the embankment affects the cohesion c of the soil, and the sliding safety factor is calculated. Using this calculation method, the reinforcement device 1 is designed to satisfy a predetermined sliding safety factor.

[0033] Incidentally, the reinforcing device 1 of the present invention uses wood (or wood-based material) as the main material for the boards. By using wood, as described above, the reinforcing device 1 is not only lightweight, but also capable of carbon storage and easy to process on site. These are the effects obtained by using wood as the main material, but in this case, wood decay and insect damage become problems.

[0034] In response to this problem, the inventors have invented and patented a method for preventing wood decay using capillary hydrohead (Patent No. 5261839). This decay prevention method also helps prevent insect damage. This method is also applied to the present invention, and by placing wooden boards below the groundwater level, decay of the boards can be prevented.

[0035] Here, we will briefly explain the method for preventing wood decay using capillary hydrohead according to the present invention. The depth from the groundwater level to the ground surface of the soft ground 2 is measured in advance, for example, by boring the ground. Then, the height from the groundwater level to the saturated volumetric water content of the embankment material 10, consisting of sand and gravel, is measured as the capillary head height. The groundwater level refers to the surface where the atmosphere and groundwater come into contact when a hole is formed in the ground by boring or other means.

[0036] Based on the measurement results, when the reinforcement device 1 of the present invention is laid on soft ground 2, and embankment material is piled on the ground surface on which the reinforcement device 1 is laid, the height from the groundwater level to the upper end of the reinforcement device 1 is set to be less than the height of the capillary water head when the volumetric water content of the embankment material is saturated. This utilizes the fact that groundwater rises through the gaps in the embankment material by capillary action and fills with capillary water up to the height of the capillary water head. As a result, the reinforcement device 1 of the present invention is below the groundwater level, and decay of wooden boards can be prevented.

[0037] Furthermore, as previously explained, sand or gravel 10 may be laid between the first structure 4 constituting the reinforcement device 1 of the present invention and the soft ground 2. The laid sand or gravel 10 can also raise the groundwater level. This is because when the sand or gravel 10 comes into contact with the groundwater surface of the soft ground 2, groundwater rises through the gaps in the sand or gravel 10 by capillary action. Then, when embankment material is piled up in the same manner as described above, the risen groundwater rises further through the gaps in the embankment material by capillary action, causing the reinforcement device 1 of the present invention to be below the groundwater level and preventing decay of the wooden board material.

[0038] Next, a method for reinforcing soft ground 2 using the reinforcing device 1 of the present invention will be explained with reference to Figures 4 to 6. First, a first foundation plate 6 is laid on the soft ground 2, and then another first foundation plate 6 is laid at a predetermined interval from the first one. In this way, multiple first foundation plate 6 are laid at predetermined intervals, for example, at equal intervals, in the area where the ground is to be reinforced, thereby forming the first structure 4 (see Figures 4(a) and (b)).

[0039] Then, multiple first foundation plates 6 are laid at predetermined intervals, for example, at equal intervals, to form the first structure 4. After that, sand or gravel 10 is placed between the laid first foundation plates 6 and filled (see Figure 4(b)). The sand or gravel 10 is an embankment material, etc.

[0040] Next, the filled sand and gravel material 10 is compacted using a compaction machine such as a tamper (see Figure 5(a)). At this time, it is preferable to finish the upper surface of the first structure 4 and the upper surface of the filled and compacted sand and gravel material 10 so that they are smooth.

[0041] Then, the sand and gravel material 10 is compacted, and the second foundation plate material 8 is laid on top of the upper end surface and smooth surface of the first structure 4. In this case, it is positioned approximately perpendicular to the longitudinal direction of the first foundation plate material 6 (see Figure 5(b)). Multiple second foundation plate materials 8 are laid at predetermined intervals to constitute the second structure 5.

[0042] In this case, the portion of the second base plate 8 that comes into contact with the first base plate 6 is laid so that the second base plate 8 and the first base plate 6 are in close contact. This allows the joint portion 9 of the first base plate 6 to be overlapped from above on the laying surface of the second base plate 8, resulting in a structure that is less likely to create a step at the joint portion 9, and also allows the second structure 5, which will be described later, to be securely fixed to the first structure 4.

[0043] Here, the length of the first foundation plate 6 and the second foundation plate 8 can be appropriately adjusted in the longitudinal and transverse directions according to the construction site. In this case, the lengths can be easily adjusted by devising a way to join the plate unit 7 that forms the first foundation plate 6 and the second foundation plate 8. Since the plate unit 7 is made of wood or wood-based material, it is easy to process and also has the characteristic of being resistant to freezing.

[0044] Furthermore, the joining of the plate material units 7 can be done by, for example, forming the first base plate material 6 and the second base plate material 8 in advance at a manufacturing site, and then transporting the formed first base plate material 6 and the second base plate material 8 to the construction site using a transport truck or the like.

[0045] In this case as well, since the first base plate 6 and the second base plate 8 are made of wood or wood-based material, they are lightweight and can be transported in large quantities at once. Therefore, transportation costs can be reduced, and energy-saving effects can also be expected.

[0046] After assembling the first structure 4 and the second structure 5 in a roughly grid-like shape using the procedure described above, the intersections (contact surfaces) of the first base plate 6 constituting the first structure 4 and the second base plate 8 constituting the second structure 5 are temporarily fastened using bolts such as lag screws (see Figure 6(a)). Then, through holes are drilled at the intersections, and pins such as round steel bars or wooden dowels are driven into the through holes with a hammer to secure them.

[0047] This securely fixes the first structure 4 and the second structure 5, thus forming the reinforcing device 1 of the present invention. However, the fixing method is not limited to the pinning method described above, as long as the first structure 4 and the second structure 5 do not shift or move.

[0048] Incidentally, depending on the conditions of the soft ground 2, a new first structure 4 may be formed on top of the second structure 5, which will be the second layer, and laid as the third layer. In this case, it is necessary to finish the upper surface of the second structure 5 and the upper surface of the filled and compacted sand or gravel material 10 so that they are smooth.

[0049] Then, the first foundation plate 6 is laid on top of the upper end surface and rough surface of the second structure 5, which have been compacted by the sand and gravel material 10. In this case as well, multiple first foundation plate 6 are arranged at equal intervals, approximately perpendicular to the longitudinal direction of the second foundation plate 8, and the first foundation plate 6 are fixed in place using the method described above. This constitutes the third stage, the first structure 4.

[0050] In this way, the first structure 4 and the second structure 5 are stacked alternately in multiple layers, such as the fourth, fifth, and so on, to form the reinforcing device 1 according to the conditions of the soft ground 2.

[0051] The reinforcement device 1 of the present invention has the effect of reducing embankment load because it uses lightweight wood material, does not contaminate groundwater like conventional cement-based solidification materials or geotextile materials, and is also expected to have the effect of fixing a large amount of carbon in the ground. Furthermore, it can distribute the superimposed load and transmit it to the soft ground 2, equalizing the deformation of the soft ground 2 and also has the effect of suppressing differential settlement. It is particularly effective when the thickness of structures such as embankments is thin.

[0052] Furthermore, because the first foundation plate material 6 and the second foundation plate material 8 are laid to form the first structure 4 and the second structure 5, construction is quick and no curing is required. Therefore, one of its features is that structures such as embankments can be used immediately after the reinforcement device 1 is installed.

[0053] Furthermore, unlike conventional ground reinforcement technologies such as those using cement-based solidification materials, this device is constructed using materials that reliably possess strength and rigidity, eliminating the need for preliminary tests such as raw material mix design tests, thus ensuring reliable performance. In addition, because it is constructed by combining boards made of wood or wood-based materials, it can be used for temporary embankments, and has the excellent advantage of being removable when no longer needed. [Explanation of Symbols]

[0054] 1. Reinforcement device 2 Soft ground 3. Embankment 4 First structure 5 Second structure 6 1st foundation plate 7. Board Unit 8 Second foundation plate material 9. Joint 10 Sand and gravel

Claims

1. A first structure is formed by a plurality of first foundation plates made of wood arranged in the same direction and laid at arbitrary intervals (interval ≥ 0), and the interval between adjacent first foundation plates is set to an interval that ensures sliding safety. The second structure is formed by a plurality of second base plates made of wood laid approximately perpendicular to the longitudinal direction of the first base plate and at arbitrary intervals (interval ≥ 0), and the intervals between adjacent second base plates are also set to ensure sliding safety. A second structure is stacked on top of the first structure to form a reinforcing device, the formed reinforcing device is placed between the soft ground and the embankment, and the buoyancy of the reinforcing device is set to the value obtained by subtracting the dry mass of the reinforcing device from the saturated mass of the soft ground, and a load having a load greater than or equal to the buoyancy is placed on the reinforcing device. The depth from the groundwater level to the ground surface of the soft ground was measured, and the height from the groundwater level to the saturated volumetric water content of the embankment was measured to be the height of the capillary head. Based on these measurement results, when the reinforcing device is laid on the soft ground, and when embankment is piled on the surface on which the reinforcing device is laid, the height from the groundwater level to the top of the reinforcing device is made smaller than the height of the capillary head to the saturated volumetric water content of the embankment, so that the reinforcing device is below the groundwater level, and the aim is to prevent decay of the reinforcing device made of wood. A method for reinforcing soft ground characterized by the following:

2. A first structure is formed by a plurality of first foundation slabs made of wood arranged in the same direction and laid at arbitrary intervals (interval ≥ 0), and a smooth surface formed by embedding and compacting sand or gravel between the first foundation slabs and the soft ground, and the interval between adjacent first foundation slabs is set to an interval that ensures sliding safety. The second structure is formed by a plurality of second base plates made of wood laid approximately perpendicular to the longitudinal direction of the first base plate and at arbitrary intervals (interval ≥ 0), and the intervals between adjacent second base plates are also set to ensure sliding safety. A second structure is stacked on top of the first structure to form a reinforcing device, the formed reinforcing device is placed between the soft ground and the embankment, and the buoyancy of the reinforcing device is set to the value obtained by subtracting the dry mass of the reinforcing device from the saturated mass of the soft ground, and a load having a load greater than or equal to the buoyancy is placed on the reinforcing device. The depth from the groundwater level to the ground surface of the soft ground is measured, and the height from the groundwater level when the volumetric water content of the embankment is saturated is measured to be the height of the capillary water head. Based on these measurement results, when the reinforcing device is laid on the soft ground, and when the embankment is piled on the surface on which the reinforcing device is laid, the height from the groundwater level to the top of the reinforcing device is made smaller than the height of the capillary water head when the volumetric water content of the embankment is saturated. In addition, the gaps between the sand and gravel materials embedded to create the smooth surface are raised by capillary action, raising the groundwater level so that the reinforcing device is below the groundwater level, thereby preventing decay of the reinforcing device made of wood. A method for reinforcing soft ground characterized by the following:

3. The first and second structures are formed by stacking them alternately in three or more layers. A method for reinforcing soft ground according to claim 1 or 2, characterized by the features described above.

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