JP2022062469A - Dam reinforcement structure, and construction method of the same - Google Patents

Abstract

To provide a dam reinforcement structure of an existing dam body for suppressing dam breakage due to a typhoon, a concentrated torrential rainfall, a tsunami, etc.SOLUTION: An outside slope face of a dam body 1 is constructed by first improved soil 3 comprising a mixture of field soil that constitutes the dam body 1 or a surrounding ground of the dam body 1, a cement material, short fiber materials, bentonite, and water. An inside slope face of the dam body 1 is constructed by second improved soil 4 comprising a mixture of the field soil, a cement material, short fiber materials, and water. Thus, breakage of the dam body 1 due to a typhoon, a concentrated torrential rainfall, a tsunami, etc. is suppressed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a bank reinforcement structure for reinforcing an existing bank body and a method of constructing the bank reinforcement structure.

In recent years, due to huge typhoons and torrential rains, river embankments in various places have collapsed, causing enormous damage. Most of the river embankments have been built from ancient times using embankments made of various soil materials, and there have been many reports of cases of embankment breaking due to overflow, infiltration into the embankment, or erosion during floods. In the renovation work of the river embankment so far, earthquake resistance by improving the ground of the consolidated ground, erosion countermeasures by covering the surface slope on the river side (outside of the embankment), rainfall infiltration countermeasures by asphalt pavement at the top, land Piping measures are being implemented by reinforcing the slope of the back slope on the side (inside the embankment).

Therefore, Patent Document 1 describes the above-mentioned prior art for piping countermeasures as follows.
(1) Reinforce the existing embankment by embankment with fiber-mixed reinforced soil on the upper surface of the existing embankment so as to cover the lower part of the inner slope and the subsequent part of the surrounding foundation ground surface.
(2) Even if the water level is applied to the embankment, if the embankment is made of earth and sand, it passes through the embankment and the foundation ground, and the lower part of the inner slope of the embankment and this. An osmotic flow of water to the surrounding foundation ground surface is generated.
(3) A water path (hereinafter referred to as a pipeline) from the outside of the embankment to the lower part of the inner slope of the embankment or the surrounding foundation ground surface that follows it, passing through the inside of the embankment or the foundation ground by the infiltration flow. ) Is formed and grows, but since the presser embankment made of fiber-mixed reinforced soil is strong against scouring, the growth of the pipeline is suppressed in the presser embankment until the pipeline communicates inside and outside the embankment. It is difficult to reach.

Japanese Patent No. 3357319

In the invention of the piping breakage prevention reinforcing structure of the existing embankment described in Patent Document 1 described above, although the formation of the pipeline communicating with the inside and outside of the embankment is suppressed, the slope of the embankment on the river side is scoured. It is easily eroded, and as a result, the stability of the embankment is lost and there is a risk of bank breakage. In addition, in recent years, the slope of the embankment on the land side has begun to collapse due to the overflow of the embankment due to floods, etc., leading to the breakage of the embankment.

The present invention has been made in view of this point, and an object of the present invention is to provide a bank reinforcement structure and a construction method thereof for suppressing a bank breakage due to a typhoon, torrential rain, tsunami, etc. in an existing bank body. do.

The present invention is a means for solving the above-mentioned problems, and the invention relating to the embankment reinforcing structure according to claim 1 is a embankment reinforcing structure for reinforcing an existing embankment body, and the surface of the embankment body is covered with the embankment. It is characterized by being constructed of improved soil made by mixing local earth and sand, cement material, short fiber material, impermeable material and water that make up the body or the ground around the embankment. be.
In the invention of claim 1, the improved soil is mixed with a water-impervious material, and the surface of the existing embankment is created by the improved soil, so that inundation into the embankment (permeation of a large amount of water) is suppressed. This can lead to the stabilization of the embankment body consisting of the embankment. Further, since the cement material and the short fiber material are mixed in the improved soil, the strength and toughness of the surface of the embankment can be improved. By creating the surface of the existing embankment with the improved soil, it is possible to suppress the erosion of the embankment due to the flow of water, and by extension, the bank breakage in the event of an emergency such as a typhoon, torrential rain or tsunami. It can be suppressed.

The invention according to claim 2 is characterized in that, in the invention of claim 1, the slope outside the levee body is created by the improved soil.
In the invention of claim 2, since the outer slope of the existing embankment body is created by the improved soil, the infiltration of water from the outer slope of the embankment body into the embankment body is suppressed and the strength of the outer slope is suppressed. , Toughness can be improved.

The invention according to claim 3 is characterized in that, in the invention of claim 1 or 2, the slope inside the embankment body is created by the improved soil excluding the impermeable material. Is.
In the invention of claim 3, since the slope inside the embankment is made of improved soil excluding the impermeable material, the water inside the embankment can be easily discharged from the slope inside the embankment. , It is possible to suppress the rise in water level in the embankment due to the accumulation of a large amount of water in the embankment. As a result, the soil particles constituting the embankment body are suppressed from being saturated with water, the shear friction resistance between the soil particles is maintained, and the slope collapse can be prevented. In addition, since the improved soil created on the inner slope of the embankment contains cement material and short fiber material, the strength and toughness of the inner slope can be improved, and as a result, from the embankment. It is possible to suppress the erosion of the inner slope due to the overflow of the soil. The outer slope of the existing embankment is the slope on the river, lake or sea side, while the inner slope is on the opposite side of the river, lake or sea side and on the land side. be.

The invention according to claim 4 is the invention according to claim 1, wherein in the embankment body, each of the outer and inner slopes is created by the improved soil, and the improved surface is created on the outer slope. It is characterized in that the weight per unit volume of the impermeable material constituting the soil is larger than the weight per unit volume of the impermeable material constituting the improved soil formed on the inner slope.
In the invention of claim 4, when the inner slope and the outer slope of the embankment body are created by the improved soil, the unit volume of the impermeable material constituting the improved soil created on the outer slope. By setting the hit weight to be larger than the weight per unit volume of the impermeable material constituting the improved soil created on the inner slope, the infiltration of water from the outer slope is suppressed and It is possible to allow some water to be discharged from the inner slope, suppress the infiltration of water into the embankment as much as possible, and maximize the rise in the water level in the embankment due to the accumulation of a large amount of water in the embankment. It can be suppressed.

According to the invention of claim 5, in the invention of claim 4, the improved soil formed on the slope inside the embankment has a drainage hole for discharging water in the embankment to the outside. It is characterized by being formed.
In the invention of claim 5, since the improved soil created on the slope inside the embankment contains a water-impervious material even in a small amount, a slight water-impervious effect appears on the inside. By providing a drainage hole in the improved soil created on the slope of, the water that has penetrated into the embankment can be actively drained from the inner slope. In addition, it is better to arrange a suction prevention material made of non-woven fabric inside the drain hole. The suction prevention material allows drainage from the drainage hole, while preventing leakage of earth and sand constituting the embankment body from the drainage hole.

The invention according to claim 6 is characterized in that, in the invention of any one of claims 1 to 5, the staple fiber material is a natural material.
The fiber material of the existing technology is a polymer material, and in the unlikely event that the improved soil erodes and flows out into the surrounding rivers, lakes, marshes, seas, etc., there is a risk of microplastic problems. In view of this, in the invention of claim 6, since the staple fiber material is composed of a natural material such as hemp or straw, there is no possibility of causing a problem of polluting the water environment even at the time of spillage.

The invention according to claim 7 is characterized in that, in any of the inventions of claims 1 to 6, the water-impervious material contains bentonite.
In the invention of claim 7, the water-impervious material may have a small water permeability coefficient due to its fine particle size, and may be dredged cohesive soil or fly ash (coal ash) containing bentonite, which can be applied as a water-impervious material. Bentonite alone may be used. By mixing bentonite, bentonite absorbs water and expands, the permeability coefficient as a water-impervious material can be reduced, and the amount of water infiltrated from the slope can be further reduced.

The invention according to the method of constructing the embankment reinforcing structure according to claim 8 is a method of constructing the embankment reinforcing structure for reinforcing the existing embankment body, which comprises a mixture of cement material, short fiber material, impermeable material and water. The slope is formed by a pressure feeding step of pumping the mixed slurry to the slope of the embankment and an improved soil obtained by stirring the local sediment and the mixed slurry while digging up the local sediment constituting the slope. It is characterized by comprising a stirring step to be created.
In the invention of claim 8, at least by performing a pressure feeding step and a stirring step, the slope of the existing embankment can be easily and inexpensively formed on the improved soil. As a result, the existing embankment body can be reinforced and stabilized without much effort, and the embankment can be suppressed in the event of an emergency such as a typhoon, torrential rain or tsunami.

According to the present invention, it is possible to suppress a bank breakage due to a typhoon, torrential rain, tsunami, etc. in an existing bank body.

FIG. 1 is a schematic cross-sectional view showing a bank reinforcement structure according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view showing a state in which the slope outside the embankment body is created by the first improved soil in the first embodiment from the vicinity of the slope. FIG. 3 is a diagram showing a state in which the slope outside the embankment body is created by the first improved soil in the compartment bucket in the first embodiment. FIG. 4 is a plan view showing a state in which the slopes of the embankment body are partially overlapped with each other when the slope of the embankment body is constructed with the first or second improved soil in the first embodiment. FIG. 5 is a schematic cross-sectional view showing a bank reinforcement structure according to a second embodiment of the present invention. FIG. 6 is a diagram showing a drainage hole provided in the first improved soil created on the inner slope in the second embodiment and including a suction prevention material. FIG. 7 is a diagram showing a drainage hole including a suction prevention material provided in the first improved soil formed on the outer slope and provided with a check valve in the second embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS. 1 to 7.
Hereinafter, the bank reinforcement structure according to the first and second embodiments of the present invention will be described. The embankment 1 is an existing one, and is composed of an embankment having a substantially trapezoidal cross section or a small step on the slope. The outer slope of the embankment 1 is the slope on the river, lake or sea side, while the inner slope of the embankment 1 is on the opposite side of the river, lake or sea side and on the land side. It is a face. The embankment body 1 includes not only a river embankment body but also a coastal embankment body and the like. It can be applied to all of the existing embankment bodies 1 that have been created.

First, the bank reinforcement structure according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. In the first embodiment, as shown in FIG. 1, the bank body 1 is formed by the first improved soil 3 whose outer slope is described later, and the second improved soil whose inner slope is described later. It is constructed and configured by 4. The first improved soil 3 is composed of a mixture of a short fiber material, bentonite as an impermeable material, a cement material, and water with the local earth and sand constituting the slope. In the present embodiment, the short fiber material is a natural material such as hemp or straw, and a material having a length of 10 to 30 mm and a fiber diameter of 10 to 400 μm is adopted. Bentonite is a clay whose main component is montmorillonite. As the cement material, for example, ordinary Portland cement material is adopted in this embodiment.

In the first improved soil 3, the mixed amount of bentonite is appropriately set within the range of 0 to 60 kg / m ³ . The mixing amount of the cement material is appropriately set within the range of 60 to 80 kg / m ³ . The staple fiber material is appropriately set so that the volume ratio in the mixed soil (first improved soil 3) is in the range of 0.6 to 1.0%. The amount of water is set according to the amount of local earth and sand, and is set to such an amount that these particulate materials can be constructed with appropriate viscosity without material separation. That is, the amount of water added to the first improved soil 3 is set so as to be in a state where bleeding is not performed or the workability is within an allowable range.

In this way, the mixed amount of cement material, bentonite, and staple fiber material is constant regardless of the amount of local earth and sand. The composition is designed by setting the amount of water with respect to the amount of sediment so that the amount increases and conversely the amount of sediment decreases when the amount of sediment increases. On the other hand, the second improved soil 4 is formed by removing bentonite from the first improved soil 3 described above, and mixing short fiber material, cement material and water with the local earth and sand constituting the slope.

The above-mentioned first improved soil 3 and second improved soil 4 are subjected to a strength test, that is, a uniaxial compressive strength test (JIS A 1216), and the strength _quo is 1000 kN / m ² or more and the strain is 10%. It has been confirmed that the strength does not yield and the toughness is obtained. In addition, the first improved soil 3 has bentonite, and a permeability test (triaxial permeability test with higher test accuracy than JIS A 1218) was carried out, and satisfactory results (for example, permeability coefficient k = 1 ×) were carried out. ^{About 10-7} m / s) is obtained.

Next, a construction method for creating an outer slope of the embankment body 1 with the first improved soil 3 will be described. Since the construction method for creating the inside of the embankment 1 with the second improved soil 4 is basically the same as the construction method for creating the outer slope of the embankment 1 with the first improved soil 3. The description here will be omitted.

First, the equipment required for constructing the slope outside the embankment body 1 with the first improved soil 3 will be described below.
As shown in FIG. 2, for example, a bentonite tank 11 in which bentonite is stored, a cement tank 12 in which cement material is stored, a water tank 13 in which water is stored, and a staple fiber material are placed on a loading platform 10 such as a trailer. A tank 14 for a short fiber material is mounted. Further, the loading platform 10 is equipped with a stirring device 16 that communicates with the bentonite tank 11, the cement tank 12, the water tank 13, and the staple fiber tank 14. Further, the loading platform 10 is equipped with a pressure feeding pump 17 that communicates with the stirring device 16 and pumps the mixed slurry from the stirring device 16 onto the slope. Then, the loading platform 10 such as a trailer is stopped at the top end surface of the bank body 1.

The backhoe 23 is arranged on the top surface of the embankment 1 in the vicinity of the loading platform 10. A compartment bucket 27 is connected to the tip of the arm 24 of the backhoe 23. The bottom surface of the compartment bucket 27 is opened while being connected to the tip of the arm 24 of the backhoe 23. The compartment bucket 27 is formed in a rhombus shape in a plan view. In the compartment 27, one of the adjacent side wall portions 28A and 28A is made of steel, and the other adjacent side wall portions 28B and 28B are made of flexible elastic rubber, respectively. The top wall portion 28C of the compartment bucket 27 is made of steel.

The tip of the pumping hose 18 extending from the pumping pump 17 is connected to the top wall portion 28C of the compartment bucket 27. As shown in FIG. 3, a plurality of excavation agitation devices 32 are provided inside the partition bucket 27. The excavation agitation device 32 includes a rotation shaft 33 rotatably supported by the partition bucket 27, and a plurality of excavation agitation blades 34 extending from the outer peripheral surface of the rotation shaft 33 at intervals in the circumferential direction and the axial direction. It is equipped with. A drive source (not shown) such as an electric motor is connected to the rotating shaft 33 of each excavation agitator 32.

Then, as shown in FIG. 2, first, by operating the backhoe 23, the partition bucket 27 connected to the tip of the arm 24 is positioned at an arbitrary position on the slope of the embankment body 1. At this time, the backhoe 23 is operated to arrange the partition bucket 27 at an arbitrary position on the slope, and as shown in FIG. 3, the steel side wall portions 28A and 28A are pierced from the slope to the inside. To. At that time, the elastic rubber side wall portions 28B and 28B are gently bent outward from the partition bucket 27 so that the tips thereof are along the slope.

Further, on the loading platform 10 such as the trailer shown in FIG. 2, a predetermined amount of bentonite is supplied from the bentonite tank 11 to the stirring device 16, a predetermined amount of cement material is supplied from the cement material tank 12, and water is further supplied. A predetermined amount of water is supplied from the tank 13, and a predetermined amount of short fiber material is further supplied from the short fiber material tank 14. Subsequently, bentonite, cement material, staple material and water are stirred in the stirring device 16 shown in FIG. 2 to generate a mixed slurry. Then, as a pumping step, the mixed slurry in the stirring device 16 is pumped into the compartment bucket 27 by the pumping pump 17 via the pumping hose 18.

Therefore, referring to FIG. 3, in the compartment bucket 27, the rotation shaft 33 of each excavation stirring device 32 is rotationally driven by the drive source, and each excavation stirring blade 34 rotates, so that the compartment bucket on the slope surface is rotated. The area partitioned by 27 is slightly dug up. Then, in this situation, as a stirring step, the mixed slurry pumped into the compartment bucket 27 is stirred with the local earth and sand dug up by the rotation of each excavation stirring blade 34 of each excavation stirring device 32. Then, while maintaining this state, the arm 24 of the backhoe 23 is operated, and the compartment bucket 27 is gradually pushed toward the slope together with the excavation agitation device 32, whereby each excavation agitation device 32 is agitated. By the rotation of the wing 34, the local earth and sand are further dug up and pushed in while being stirred with the pumped mixed slurry, and the area partitioned by the partition bucket 27 is created by the predetermined depth first improved soil 3.

The height of each side wall portion 28A, 28A of the compartment bucket 27 is set to an appropriate value within the range of 20 to 50 cm, and the depth of piercing the slope is set to an appropriate value within the range of 10 to 30 cm. .. Therefore, as an economical construction, in the present embodiment, the heights of the side wall portions 28A and 28A of the compartment bucket 27 are 20 cm, the piercing depth is 10 cm, and the space between the slope and the top end portion 28C of the compartment bucket 27 is set. In the initial state where the distance is 10 cm, the slope is dug up by the operation of each excavation and stirring device 32, and the mixed slurry from the stirring device 16 is stirred with the excavated local earth and sand by the operation of each excavation and stirring device 32. To. After that, by pushing the partition bucket 27 together with each excavation agitator 32 toward the slope by about 10 cm, a range of about 20 cm in depth from the slope is created by the first improved soil 3.

Therefore, when the partition bucket 27 is gradually pushed toward the slope, the elastic rubber side wall portions 28B and 28B are bent outward, so that there is no need for insertion hole marks or the like in the created portion. The mode does not remain. After that, when the work of one range by the compartment bucket 27 is completed, the backhoe 23 is operated again to move the compartment bucket 27 to the next position, and then the above-mentioned steps are repeated to cover the entire slope with the first improved soil 3. Will be created by.

In addition, by the above-mentioned step, the area surrounded by the section bucket 27 is sequentially created by the first improved soil 3 on the slope outside the embankment body 1, and as shown in FIGS. 3 and 4, the section bucket 27 is formed. When moving from the created location to the next work location, make sure that the elastic rubber side walls 28B and 28B of the compartment bucket 27 overlap (wrap) with the created location by a predetermined width. The compartment bucket 27 is placed at the next work location. In this way, the work is carried out sequentially so that the areas created by the compartment bucket 27 partially overlap each other, so that undeveloped parts can be eliminated as much as possible. Also on the inner slope of the embankment 1, the area surrounded by the compartment bucket 27 is sequentially created by the second improved soil 4, but as shown in FIG. 4, the first slope created on the outer slope. Similar to the construction method of the improved soil 3, the construction is sequentially carried out so that the construction areas of the compartment bucket 27 partially overlap.

Therefore, most of the existing embankment 1 is an embankment, and it should be avoided that a large amount of water permeates and accumulates in the embankment (generation of seepage flow). That is, when a large amount of water permeates and accumulates in the embankment body 1, the frictional force (shear friction resistance force) between soil particles and the suction effect are reduced, so that the slope on the outside of the embankment body 1 is washed. It can be inferred that the embankment is easily eroded, and as a result, the stability of the embankment 1 is lost and the embankment breaks. In view of such circumstances, in the above-mentioned first embodiment, the slope outside the existing embankment 1 is formed by the first improved soil 3 (including bentonite). As a result, the infiltration of water from the outer slope of the embankment 1 into the embankment 1 is suppressed, a large amount of water is suppressed from penetrating into the embankment 1, and the strength and toughness of the outer slope are improved. Can be improved. Then, it is possible to suppress erosion of the embankment body 1 due to the flow of water, and by extension, it is possible to suppress embankment breakage in the event of an emergency such as a typhoon, torrential rain or tsunami.

Further, according to the first embodiment, the slope inside the embankment body 1 is created by the second improved soil 4 composed of a mixture of local earth and sand, short fiber material, cement material and water, excluding bentonite. Therefore, the water in the embankment 1 can be easily discharged from the slope inside the embankment 1, and the rise in the water level in the embankment 1 due to the accumulation of a large amount of water in the embankment 1 can be suppressed. can. As a result, the soil particles constituting the embankment 1 are suppressed from being saturated with water, the shear friction resistance between the soil particles is maintained, and the slope collapse can be suppressed. Further, since the first improved soil 3 formed on the inner slope of the embankment body 1 contains a cement material and a short fiber material, the strength and toughness of the inner slope can be improved, and as a result, the strength and toughness of the inner slope can be improved. , It is possible to suppress the erosion of the inner slope due to the overflow from the embankment body 1. As a result, the embankment body 1 can be sufficiently reinforced, which leads to its stabilization, which in turn is sufficient as a measure for suppressing the bank breakage in the event of an emergency such as a typhoon, torrential rain or tsunami.

Further, according to the first embodiment, a pressure feeding step of pumping a mixed slurry formed by mixing cement material, short fiber material, bentonite and water onto the slope of the embankment body 1 and a site constituting the slope are formed. It is provided with a stirring step of creating a slope with the first improved soil 3 formed by stirring the local soil and the mixed slurry while digging up the soil. As a result, while making effective use of the local earth and sand, there is no need to carry in and temporarily store a large amount of earth and sand from the outside, and the slope on the outside of the embankment 1 is easily and inexpensively constructed. It can be created from the first improved soil 3 containing the local earth and sand. Further, in the stirring step, the slope is formed by using a plan-viewing diamond-shaped partition bucket 27 connected to the tip of the arm 24 of the backhoe 23 and a plurality of excavation stirring devices 32 provided in the partition bucket 27. Since it is created from the first improved soil 3 or the second improved soil 4, it is not necessary to newly equip a large-scale facility for mixing earth and sand, and the total cost such as the facility cost and the construction cost can be reduced.

Next, the bank reinforcement structure according to the second embodiment will be described with reference to FIGS. 5 to 7. As shown in FIG. 5, in the second embodiment, the outer slope of the embankment 1 is formed by the first improved soil 3, and the inner slope thereof is also created by the first improved soil 3. It is composed. The weight per unit volume of bentonite in the first improved soil 3 formed on the outer slope is set to be larger than the weight per unit volume of bentonite in the first improved soil 3 formed on the inner slope. ..

Specifically, in the first improved soil 3 created on the slope outside the embankment body 1, the mixed amount of bentonite is set to a value close to a maximum of 60 kg / m ³ . On the other hand, in the first improved soil 3 formed on the slope inside the embankment body 1, the mixed amount of bentonite is set to a value as close as possible to 0 kg / m ³ . As a result, the water impermeability is higher on the outer slope than on the inner slope of the embankment 1. In other words, inundation from the outer slope of the embankment 1 into the embankment 1 is not allowed, and drainage from the inner slope of the embankment 1 to the outside is allowed to some extent.

As shown in FIG. 6, in the first improved soil 3 formed on the slope inside the embankment body 1, a plurality of drainage holes 40 for discharging the water in the embankment body 1 to the outside are formed at intervals. .. The drainage hole 40 penetrates the inside of the first improved soil 3 along the horizontal direction. Each drainage hole 40 communicates the outside of the land side with the inside of the embankment 1 (a portion not created by the first improved soil 3). These drainage holes 40 are formed by hollowing out the installation portion of the drainage holes 40 by boring or the like after constructing the first improved soil 3 and before solidifying, and inserting a pipe member or the like. Inside each drainage hole 40, a suction prevention material 41 made of a non-woven fabric is arranged on the inner side of the embankment body 1. By providing the suction preventing material 41, it is possible to allow drainage from the drainage hole 40, while preventing leakage of earth and sand constituting the embankment body 1 from the drainage hole 40.

As shown in FIG. 7, even if a plurality of drainage holes 40 including a suction prevention material 41 are formed inside in the first improved soil 3 formed on the slope outside the embankment body 1 at intervals. good. In that case, the check valve 42 is arranged at the end opening on the opposite side of the drainage hole 40 from the bank body 1 side. The check valve 42 regulates inundation from the outside (river or the like) into the embankment body 1 and allows drainage from the inside of the embankment body 1 to the outside. Therefore, in the above-mentioned first embodiment, a plurality of drainage holes 40 with a check valve may be provided in the first improved soil 3 formed on the slope outside the embankment body 1.

Further, since the construction method of the bank reinforcement structure according to the second embodiment is the same as the construction method of the bank reinforcement structure according to the first embodiment, the description thereof is omitted here.

As described above, in the second embodiment, the outer slope of the embankment 1 is formed by the first improved soil 3, and the inner slope thereof is also formed by the first improved soil 3. However, the weight per unit volume of bentonite constituting the first improved soil 3 formed on the outer slope is per unit volume of bentonite constituting the first improved soil 3 formed on the inner slope. Is set to be greater than the weight of. As a result, the infiltration of water from the outer slope of the embankment 1 into the embankment 1 is suppressed, and the drainage from the inner slope into the embankment 1 is allowed to some extent, as in the first embodiment. In addition, it is possible to suppress the rise in water level in the embankment body 1 as much as possible due to the accumulation of a large amount of water in the embankment body 1. As a result, the soil particles constituting the embankment 1 are suppressed from being saturated with water, the shear friction resistance between the soil particles is maintained, and the slope collapse can be suppressed. Moreover, since the first improved soil 3 contains a cement material and a short fiber material, the strength and toughness of the entire embankment 1 can be improved. As a result, the embankment body 1 can be sufficiently reinforced, leading to its stabilization, and eventually, it is possible to suppress the bank breakage in the event of an emergency such as a typhoon, torrential rain or tsunami.

Further, in the second embodiment, the first improved soil 3 formed on the slope inside the embankment 1 is formed with a plurality of drain holes 40 for draining the water in the embankment 1, so that the embankment 1 is formed. The water that permeates and accumulates inside can be actively drained from the inner slope.

Further, in the first and second embodiments, the short fiber material mixed as the first improved soil 3 and the second improved soil 4 is a natural material such as hemp or straw, so that the method of embankment 1 is used. Even if the surface is created with the first improved soil 3 or the second improved soil 4, there is no risk of causing microplastic problems in the surrounding rivers, lakes, marshes, the sea, and the like.

In the present embodiment, bentonite is used as the impermeable material in the first improved soil 3, but the water permeability coefficient is small due to the fine particle size, and the dredging cohesive soil or fly that can be applied as the impermeable material. Ash (coal ash) may be used, or these dredged cohesive soils or fly ash (coal ash) containing bentonite may be used.

Further, in the present embodiment, the slope of the embankment body 1 is formed by the first improved soil 3 and the second improved soil 4, but the top surface of the embankment body 1 is also particularly the first improved soil 3 (bentonite). Included). In short, the entire surface of the embankment body 1 may be created by the first improved soil 3 or the second improved soil 4.

1 Embankment, 3 1st improved soil, 4 2nd improved soil, 40 drainage hole

Claims (8)

It is a bank reinforcement structure for reinforcing the existing bank body.
The surface of the embankment is constructed by constructing the embankment or improved soil made by mixing local earth and sand, cement material, staple fiber material, impermeable material and water constituting the embankment body or the surrounding ground of the embankment body. Embankment reinforcement structure characterized by being done. The levee reinforcement structure according to claim 1, wherein the slope outside the levee body is created by the improved soil. The levee reinforcement structure according to claim 1 or 2, wherein the slope inside the levee body is formed by the improved soil excluding the impermeable material. In the embankment, each of the outer and inner slopes is created by the improved soil.
The weight per unit volume of the impermeable material forming the improved soil formed on the outer slope is larger than the weight per unit volume of the impermeable material forming the improved soil formed on the inner slope. The bank reinforcement structure according to claim 1, which is characterized by being large. The levee reinforcement structure according to claim 4, wherein the improved soil formed on the slope inside the levee body is formed with a drainage hole for discharging water in the levee body to the outside. The embankment reinforcing structure according to any one of claims 1 to 5, wherein the staple fiber material is a natural material. The bank reinforcement structure according to any one of claims 1 to 6, wherein the impermeable material contains bentonite. It is a construction method of the embankment reinforcement structure to reinforce the existing embankment body.
A pumping step of pumping a mixed slurry made by mixing cement material, staple fiber material, impermeable material and water to the slope of the embankment body, and
A stirring step of creating the slope with improved soil obtained by stirring the local soil and the mixed slurry while digging up the local soil constituting the slope.
A method of constructing a bank reinforcement structure, which is characterized by being provided with.

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