JP7440864B2 - Embankment reinforcement method - Google Patents

Description

The present invention relates to an embankment reinforcement structure and an embankment reinforcement method.

Traditionally, when a tsunami or storm surge hits a coastal embankment, and the water level on the sea side rises and overflow occurs, the ground on the land side may be scoured. This leads to the destruction of the entire levee body, causing seawater to flow onto land and causing severe damage. Furthermore, if the earthquake that precedes a tsunami causes the embankment to collapse or the height of the crest to drop, seawater will flow onto land and cause severe damage. In addition, the sea side of the embankment may collapse due to high waves, causing the surrounding ground to disappear or subside.

In order to solve such problems, conventionally, for example, the following measures have been taken.
(1) A method of increasing the height of the top of the levee to prevent overflow, etc. (2) A method of estimating the amount of subsidence due to earthquake motion and raising the top of the levee (3) A method of raising the top of the levee to prevent overflow, etc. A method of strengthening the original ground through ground improvement (4) A method of driving steel pipe sheet piles or double sheet piles inside the embankment body in order to maintain the crown height even when subjected to seismic motion or overflow (for example, a patented method) (See Reference 1)

JP2011-214248A

However, each of the above conventional methods has the following problems.
(1) It is difficult to respond to all large tsunamis, high waves, and storm surges. It is necessary to have embankments that will not collapse even if overflow occurs.
(2) By raising the top, the amount of subsidence increases, making it difficult to set the optimal height. Moreover, it is generally uneconomical.
(3) In order to improve the ground at the bottom of the embankment body, special construction methods are required, which is uneconomical.
(4) It is uneconomical because steel is used.

The present invention has been made in view of the above, and an object of the present invention is to provide an economical embankment reinforcement structure and embankment reinforcement method that can improve the resistance performance and seismic performance against overflow of the embankment. .

In order to solve the above-mentioned problems and achieve the objects, the levee reinforcement structure according to the present invention is a structure for reinforcing an levee consisting of an levee body, and is a structure for reinforcing an levee consisting of an levee body. In order to maintain the height of the crown, a wall is provided inside the embankment body from the crown to a predetermined depth, and is made of a soil improvement body made of a mixture of ground material and cement-based solidification material. The wall can stand on its own even if the ground inside the levee is scoured by overflow, and can maintain its crown height even if the ground around the levee sinks due to seismic motion or water level fluctuations outside the levee. It is characterized by

Further, another embankment reinforcing structure according to the present invention is characterized in that the wall body is a lattice-like structure in the above-described invention.

Further, another embankment reinforcement structure according to the present invention is the above-mentioned invention, and includes a water-blocking layer provided on the surface layer side of the bank body, and this water-blocking layer prevents water from penetrating into the inside of the bank body. , is characterized in that it reduces the external force acting on the wall.

Further, another embankment reinforcement structure according to the present invention is provided with an impermeable wall provided in a wall shape to a predetermined depth inside the embankment body on the outside of the embankment, and this impermeable wall is provided in the embankment body. It is characterized by preventing water from penetrating into the interior of the wall and reducing external forces acting on the wall.

Furthermore, the embankment reinforcement method according to the present invention is a method for reinforcing an embankment consisting of an embankment body. A step is provided inside the embankment to a predetermined depth from the top to a predetermined depth. It is characterized by being able to stand on its own even when the embankment is moved, and also being able to maintain its crown height even when the surrounding ground of the embankment sinks due to seismic motion or fluctuations in the water level outside the embankment.

Further, another embankment reinforcing method according to the present invention is characterized in that the wall body is a lattice-like structure in the above-mentioned invention.

Further, another embankment reinforcement method according to the present invention, in the above-mentioned invention, includes a step of providing an impermeable layer on the surface layer side of the embankment body, and this impermeable layer prevents water from penetrating into the inside of the embankment body. , is characterized in that it reduces the external force acting on the wall.

Further, another embankment reinforcement method according to the present invention, in the above-mentioned invention, includes a step of providing an impermeable wall in the form of a wall to a predetermined depth inside the embankment body on the outside of the embankment, and this impermeable wall is It is characterized by preventing water from penetrating into the interior of the wall and reducing external forces acting on the wall.

According to the embankment reinforcement structure according to the present invention, it is a structure for reinforcing an embankment consisting of an embankment body, and in order to maintain the top height of the embankment body during the action of external forces including earthquakes and during overflow, A wall is installed inside the bank from the top to a predetermined depth, and is made of a ground improvement material made of a mixture of ground material and cement-based solidification material. It can stand on its own even if it is scoured, and the crown height can be maintained even if the ground around the embankment sinks due to seismic motion or fluctuations in the water level outside the embankment, which improves the resistance to overflow of the embankment and its earthquake resistance. This has the effect that performance can be improved economically.

Further, according to another embankment reinforcement structure according to the present invention, since the wall body is a lattice-like structure, shear deformation of the embankment base ground during an earthquake is suppressed, and excessive pore water pressure in the embankment base is suppressed. This has the effect of suppressing the increase in liquefaction and improving the liquefaction strength.

Further, according to another embankment reinforcement structure according to the present invention, the impermeable layer is provided on the surface layer side of the embankment body, and this impermeable layer prevents water from penetrating into the inside of the embankment body, and Since it reduces the external force acting on the wall, it has the effect of making the wall economical.

Further, according to another embankment reinforcement structure according to the present invention, an impermeable wall is provided in the form of a wall to a predetermined depth inside the embankment body on the outside of the embankment, and this impermeable wall extends into the interior of the embankment body. Since it prevents water from penetrating and reduces the external force acting on the wall, it has the effect of making the wall more economical.

Moreover, according to the embankment reinforcement method according to the present invention, it is a method for reinforcing an embankment consisting of an embankment body, and in order to maintain the top height of the embankment body during the action of external forces including earthquakes and during overflow, A step is provided inside the embankment to a predetermined depth from the top to a predetermined depth. It can stand on its own even if it is scoured, and the crown height can be maintained even if the ground around the embankment sinks due to seismic motion or fluctuations in the water level outside the embankment, which improves the resistance to overflow of the embankment and its earthquake resistance. This has the effect that performance can be improved economically.

Furthermore, according to another embankment reinforcement method according to the present invention, since the wall is a lattice-like structure, shear deformation of the embankment ground during an earthquake is suppressed, and excessive pore water pressure in the embankment ground is suppressed. It is possible to suppress the increase in the liquefaction strength and improve the liquefaction strength.

Further, another embankment reinforcement method according to the present invention includes the step of providing an impermeable layer on the surface layer side of the embankment body, and this impermeable layer prevents water from penetrating into the inside of the embankment body, and Since it reduces the external force acting on the wall, it has the effect of making the wall economical.

Further, according to another embankment reinforcement method according to the present invention, the step of providing an impermeable wall in the form of a wall to a predetermined depth inside the embankment body on the outside of the embankment is provided, and the impermeable wall extends into the interior of the embankment body. Since it prevents water from penetrating and reduces the external force acting on the wall, it has the effect of making the wall more economical.

FIG. 1 is a cross-sectional view showing an embodiment of an embankment reinforcement structure and an embankment reinforcement method according to the present invention. FIG. 2 is an external force diagram in the design, where (1) is a general design and (2) is a design that takes into account the water shielding effect. FIG. 3 is a diagram showing experimental results, in which (1) is a comparative example and (2) is an example. FIG. 4 is a comparison diagram between when the unsaturated region remains (t=2s) and when it does not (t=8s). FIG. 5 is a schematic perspective view showing an example of a lattice-shaped wall.

EMBODIMENT OF THE INVENTION Below, embodiment of the embankment reinforcement structure and embankment reinforcement method based on this invention is described in detail based on drawings. Note that the present invention is not limited to this embodiment.

As shown in FIG. 1, an embankment reinforcement structure 10 according to an embodiment of the present invention is a structure that reinforces an embankment 14 consisting of an embankment body 12 built on foundation ground G, and is provided within the embankment body 12. A wall body 16 is provided. The embankment body 12 is a linear structure having a large ratio of length to width B, and has a substantially trapezoidal cross-sectional shape. In Figure 1, HWL is the water level at the time of a tsunami or storm surge, NWL is the water level during normal times, and GL is the ground surface after overflow scouring.

The wall 16 is for maintaining the top height H of the levee body 12 during the action of external forces including earthquakes and overflow, and extends vertically from approximately the center of the crest 18 of the levee body 12 to the foundation ground G. It is installed in the shape of a wall plate in the direction. This wall body 16 is made of a ground improvement body made of a mixture of ground material and cement-based solidifying material. The wall 16 is configured to be able to stand on its own even if the ground G1 on the land side (inner side of the levee) of the levee body 12 is scoured due to overflow during a tsunami or storm surge, and also to be able to stand on its own due to seismic motion or water level fluctuations on the outside of the levee. It is configured such that the crown height H can be maintained even if the ground around the body 12 sinks. Thereby, even if overflow occurs and the ground G1 on the land side is scoured, the crown height H can be maintained. Further, even if the surrounding ground sinks due to earthquake motion, high waves, etc., the crown height H can be maintained. In addition, although the example of FIG. 1 shows the case where the wall body 16 is bottomed on the foundation ground G, the wall body of this invention is not limited to this. For example, the wall body 16 is on the foundation ground G. It may have a structure that does not touch the bottom. The wall 16 can be self-supporting even if the ground G1 on the land side of the levee body 12 is scoured by overflow, and the top height H can be maintained even if the ground around the levee body 12 sinks due to earthquake motion, high waves, etc. Any form may be used as long as it can sustainably support the structure.

The entire outer slope 20 of the embankment body 12 and the upper surface of the wall body 16 at the top end 18 (surface layer side) are continuously protected by a water-blocking layer 22. The impermeable layer 22 prevents water from penetrating into the interior of the embankment body 12 and reduces external force (combined force of earth pressure, water pressure, and air pressure) acting on the wall body 16.

Further, a water-shielding wall 24 is provided directly below the destination of the slope surface 20 on the outside of the embankment. The impermeable wall 24 is in the form of a wall plate that extends in the vertical direction from the tip of the wall to the foundation ground G, and is constructed of, for example, sheet piles or ground improvement bodies. This ground improvement body can be formed by a deep mixing method in which the embankment body ground and cement-based solidification material are mixed and stirred in situ. The impermeable wall 24 prevents water from penetrating into the interior of the embankment body 12 and reduces external force (combined force of earth pressure, water pressure, and air pressure) acting on the wall body 16.

An unsaturated region R is formed between the water-shielding layer 22, the water-shielding wall 24, and the wall body 16 above the normal water level NWL. FIG. 2(1) is an external force diagram for a general design, and FIG. 2(2) is an external force diagram for a design that takes into account the water shielding effect. As shown in FIG. 2(1), when there is no impermeable layer 22 or impermeable wall 24, when water infiltrates into the embankment body 12, a resultant force of effective earth pressure Ps and hydrostatic pressure Pw acts on the wall body 16. . On the other hand, as shown in FIG. 2(2), if water does not enter through the impermeable layer 22 and the impermeable wall 24, only the resultant force of the effective earth pressure Ps and the air pressure Pa acts on the wall body 16.

Therefore, by providing the water-blocking layer 22 and the water-blocking wall 24, the external force acting on the wall 16 can be reduced. When the external force is reduced, the resistance performance (for example, volume, amount of cement, etc.) required of the wall 16 is reduced, and the wall 16 can be made economical. The water-blocking layer 22 is not limited to the outermost layer of the slope surface 20, but may be placed at any position as long as it can prevent water from penetrating into the interior of the embankment body 12 from the outside of the embankment. When provided on the outermost layer, construction is easy. Further, the water shielding wall 24 is not limited to the lower part of the levee tip, but may be provided at any position that can prevent water from penetrating into the levee body 12 from the outside of the levee. Either one or both of the water-blocking layer 22 and the water-blocking wall 24 can be omitted, but it is desirable to provide them in order to reduce the external force acting on the wall 16.

When constructing the above-described embankment reinforcement structure 10, ground improvement is performed from the top end 18 of the embankment body 12 by a well-known cement solidification treatment method, and a wall body 16 with improved ground is formed within the embankment body 12. In addition, a water-shielding wall 24 is constructed at the lower part of the tip of the slope 20 on the outside of the bank 12, and a water-shielding layer 22 is constructed on the slope 20 on the outside of the bank and the top 18. For ground improvement, it is preferable to use a mixing method in which the levee body ground and cement-based solidification material are mixed and stirred in situ. According to this embankment reinforcement structure 10, since steel materials are not used, countermeasures against overflow of the embankment 14 and seismic reinforcement can be carried out economically. Therefore, the resistance performance against overflow of the embankment 14 and the seismic performance can be economically improved.

In the above embodiment, the case where the wall body 16 is plate-shaped has been described as an example, but the wall body of the present invention is not limited to the plate-shape, and various forms can be adopted. For example, the wall 16 may be a grid-like structure. In other words, the ground-improved portion may be a structure that has a lattice shape in plan view as shown in FIG. 5, or may have a lattice shape in side view. Alternatively, a combination of these may be used. If the wall body 16 is made into a lattice-like structure, it is possible to suppress shear deformation of the embankment body ground during an earthquake, suppress an increase in excess pore water pressure within the embankment body ground, and improve liquefaction strength. be able to. Further, in the above embodiment, the case where only one wall body 16 is provided in the transverse direction of the embankment body 12 has been described as an example, but the present invention is not limited to this. Two or more wall bodies 16 may be provided at intervals. Even in this case, the same effects as described above can be achieved.

(Verification of effects of the present invention)
Next, experiments conducted to verify the effects of the present invention and their results will be described.

This experiment investigated the influence of walls using a model of the embankment placed in a water tank. First, overflow was caused by raising the water level on the outside of the embankment model. FIG. 3(1) shows an embankment without walls (comparative example), and FIG. 3(2) shows an embankment with two walls spaced apart in the width direction (an example of the present invention). As shown in this figure, in the comparative example, when overflow occurs and the ground on the land side is scoured, the crown height cannot be maintained. On the other hand, in the embodiment, even if an overflow occurs and the ground on the land side is scoured, the height of the crown can be maintained. Therefore, the present example having the wall body has excellent resistance performance against overflow compared to the comparative example.

Next, using an embankment with walls but no impermeable layer or impermeable wall, we measured the temporal changes in pore water pressure at various locations inside the embankment during overflow, and investigated the effects of unsaturated regions. Examined. FIGS. 4(1) and 4(2) show measurement points. (1) is t=2s, and (2) is t=8s. Measurement points P5 and P8 are located above and below the left side of the wall (outside the embankment), P5 is set below the normal water level, and P8 is set near the top. As shown in (3), at the initial stage of overflow from the start of overflow at t=0 to t=2s, an unsaturated region remains on the left side of the wall and the increase in water pressure is suppressed, but at t=8s No more unsaturated areas remain and the water pressure is rising. (4) to (6) show the bending moment acting on the wall, horizontal load, and displacement of the wall at each time. It can be seen that when no unsaturated region remains, the bending moment, horizontal load, and displacement increase. Therefore, it is effective to provide a water-blocking layer so that an unsaturated region remains outside the embankment of the wall.

As explained above, the embankment reinforcement structure according to the present invention is a structure for reinforcing an embankment consisting of an embankment body, and maintains the top height of the embankment body when external forces are applied, including earthquakes, and when overflowing. In order to prevent overflow, a wall is provided inside the levee body from the top to a predetermined depth, and is made of a ground improvement material made of a mixture of ground material and cement solidification material. It is possible to stand on its own even if the ground on the inside of the levee is scoured, and the crown height can be maintained even if the ground around the levee body sinks due to seismic motion or water level fluctuations on the outside of the levee. It is possible to economically improve resistance performance and seismic performance against earthquakes, etc.

Further, according to another embankment reinforcement structure according to the present invention, since the wall body is a lattice-like structure, shear deformation of the embankment base ground during an earthquake is suppressed, and excessive pore water pressure in the embankment base is suppressed. It is possible to suppress the increase in the liquefaction strength and improve the liquefaction strength.

Further, according to another embankment reinforcement structure according to the present invention, the impermeable layer is provided on the surface layer side of the embankment body, and this impermeable layer prevents water from penetrating into the inside of the embankment body, and Since the external force acting on the wall is reduced, the wall can be made economical.

Further, according to another embankment reinforcement structure according to the present invention, an impermeable wall is provided in the form of a wall to a predetermined depth inside the embankment body on the outside of the embankment, and this impermeable wall extends into the interior of the embankment body. This prevents water from penetrating and reduces the external force acting on the wall, making the wall more economical.

Moreover, according to the embankment reinforcement method according to the present invention, it is a method for reinforcing an embankment consisting of an embankment body, and in order to maintain the top height of the embankment body during the action of external forces including earthquakes and during overflow, A step is provided inside the embankment to a predetermined depth from the top to a predetermined depth. It can stand on its own even if it is scoured, and the crown height can be maintained even if the ground around the embankment sinks due to seismic motion or fluctuations in the water level outside the embankment, which improves the resistance to overflow of the embankment and its earthquake resistance. Performance can be improved economically.

Further, according to another embankment reinforcement method according to the present invention, since the wall body is a lattice-like structure, shear deformation of the embankment base ground during an earthquake is suppressed, and excessive pore water pressure in the embankment base is suppressed. It is possible to suppress the increase in the liquefaction strength and improve the liquefaction strength.

Further, another embankment reinforcement method according to the present invention includes the step of providing an impermeable layer on the surface layer side of the embankment body, and this impermeable layer prevents water from penetrating into the inside of the embankment body, and Since the external force acting on the wall is reduced, the wall can be made economical.

Further, according to another embankment reinforcement method according to the present invention, the step of providing an impermeable wall in the form of a wall to a predetermined depth inside the embankment body on the outside of the embankment is provided, and the impermeable wall extends into the interior of the embankment body. This prevents water from penetrating and reduces the external force acting on the wall, making the wall more economical.

As described above, the embankment reinforcement structure and the embankment reinforcement method according to the present invention are useful for embankments installed on coasts and river banks, and particularly economically improve resistance performance against overflow and seismic performance. It is suitable for

10 Embankment reinforcement structure 12 Embankment body 14 Embankment 16 Wall body 18 Top 20 Slope 22 Impermeable layer 24 Impervious wall B Width G Foundation ground G1 Land side ground GL Ground surface after overflow scour H Crown height HWL Water level during tsunami or storm surge NWL Water level during normal times Pa Pneumatic pressure Ps Effective earth pressure Pw Hydrostatic pressure R Unsaturated area

Claims (4)

A method of reinforcing an embankment consisting of an embankment body,
In order to maintain the height of the crest of the levee body during the action of external forces including earthquakes and overflow, the levee body is provided with ground material and cement-based solidifying material that extends vertically from the crest to a predetermined depth. a step of providing a wall made of a ground improvement material mixed with the above, and providing a water-blocking layer on the outside of the embankment of the wall, and forming an unsaturated region between the wall and the water-blocking layer, reducing an external force that is a resultant of earth pressure, water pressure, and air pressure acting on the wall , and the wall can stand on its own even if the ground inside the embankment is scoured by overflow; A method for reinforcing an embankment, characterized in that the crown height can be maintained even if the surrounding ground of the embankment body sinks due to seismic motion or water level fluctuations outside the embankment. 2. The embankment reinforcing method according to claim 1 , wherein the wall is a structure that has a lattice shape when viewed from above , or a structure that has a lattice shape when viewed from the side . The embankment according to claim 1 or 2 , wherein the impermeable layer is continuously provided on the entire slope of the outer slope of the embankment body and on the upper surface of the wall body at the top end of the embankment body. Reinforcement method. A step of providing a wall-shaped impermeable wall to a predetermined depth inside the embankment body on the outside of the embankment, the impermeable wall prevents water from penetrating from the outside of the embankment into the inside of the embankment body, and The embankment reinforcement method according to any one of claims 1 to 3 , characterized in that the method reduces the external force acting on the embankment.

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