JP2020016061A - Construction method of embankment - Google Patents

Abstract

To provide a construction method of an embankment allowing construction of the embankment to be easily carried out with less work processes on a wall facing on water such as a bank protection.SOLUTION: An installation of a precast protection wall 2 is completed in a status that a cut-off material 3 is consecutively placed in a direction where the precast protection wall 2 extends by placing the precast protection wall 2 at a predetermined position through the cut-off material 3 and a slidable resistance material 4 on an upper surface 10a of a wall 10 facing on water. At least a part of wave over the wall 10 facing on water in a case such as a high tide is cut-off with the precast protection wall 2 placed on the upper surface 10a of the wall 10 facing on water. The precast protection wall 2 is well secured on the wall 10 facing on water by the interposed slidable resistance material 4 by preventing leakage with the cut-off material 3 between the upper surface 10a of the wall 10 facing on water and the precast protection wall 2 even when the wave impacts the precast protection wall 2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for constructing a levee, and more particularly to a method for constructing a levee that can easily construct a levee on a water barrier such as a seawall with a small number of steps.

  Due to the effects of rising water levels due to global warming and the enlargement of typhoons, there is an increasing risk of flood damage on waterfront walls (such as seawalls), which had not been affected by storm surge and tsunami. Therefore, as a countermeasure against flood damage, various methods of constructing a dike have been proposed, in which a retaining wall made of concrete or the like is newly added to an existing water wall to raise the water wall (for example, Patent Document 1). reference).

  In the embankment described in Patent Literature 1, a deep groove is provided in a water wall, and a part of a block panel is inserted into the groove to form a retaining wall on the water wall. However, when this dike is used for a water wall, it is necessary to form a deep groove in the water wall, and the construction requires a lot of labor and cost. In addition, there is also a problem that the formation of the deep groove in the water wall lowers the strength of the water wall.

JP-A-2005-31068

  An object of the present invention is to provide a method for constructing a levee that can easily construct a levee with a small number of man-hours on a water barrier such as a seawall.

  In order to achieve the above object, the method for constructing a dike according to the present invention comprises: mounting the precast retaining wall at a predetermined position with a waterproofing material and a sliding resistance material interposed on the upper surface of the watertight wall; The installation of the precast retaining wall is completed in a state where the precast retaining wall is arranged continuously in the extending direction of the precast retaining wall, and at least a part of the wave exceeding the waterfall wall is disposed on the upper surface of the waterfall wall. It is characterized in that it is blocked by.

  In the present invention, since the installation of the precast retaining wall is completed by placing the precast retaining wall at a predetermined position with the water stop material and the sliding resistance material interposed on the upper surface of the waterfall wall, a groove or the like is formed in the waterfall wall. Man-hours and labor can be greatly reduced as compared with the conventional embankment construction method requiring construction. Even if a wave collides with the precast retaining wall, water leakage to the land side is prevented by the water stoppage material interposed between the upper surface of the waterfall wall and the precast retaining wall, and the sliding resistance material intervenes against the waterfall wall. The precast retaining wall can be sufficiently fixed.

It is explanatory drawing which shows typically the process of mounting a precast retaining wall on the upper surface of a waterway wall in side view in embodiment of the embankment construction method of this invention. FIG. 2 is a view on arrow A in FIG. 1. It is explanatory drawing which illustrates typically the state which mounted the precast retaining wall on the upper surface of the waterfall wall of FIG. 1 by side view. FIG. 4 is a view on arrow B in FIG. 3. FIG. 4 is a view taken in the direction of arrow C in FIG. 3. It is explanatory drawing which shows typically the process of mounting a precast retaining wall on the upper surface of a waterway wall in side sectional view in another embodiment of the embankment construction method of this invention. FIG. 7 is an explanatory view schematically exemplifying a state in which a precast retaining wall is placed on the upper surface of a water wall from FIG. 6 in a side sectional view. FIG. 8 is a view on arrow D in FIG. 7. FIG. 8 is a sectional view taken along the line EE in FIG. 7.

  Hereinafter, a method for constructing an embankment of the present invention will be described based on an embodiment shown in the drawings.

  In the present invention, as shown in FIGS. 1 to 5, a dike 1 is constructed by using a precast retaining wall 2, a waterproof material 3, and a sliding resistance material 4 on a waterfall wall 10 facing the sea, a lake, a river, or the like. I do. In the drawings of the present application, the normal direction to the water surface 10b is defined as the X direction, the extending direction of the water surface 10b orthogonal to the X direction in the horizontal direction is defined as the Y direction, and the vertical direction is defined as the Z direction. WL in the drawing of the present application indicates the water level in normal times. Hereinafter, in the X direction, the water area side where the water wall 10 faces is referred to as a water area side, and the opposite side is referred to as a land side.

  The precast retaining wall 2 (hereinafter, referred to as retaining wall 2) is formed of concrete with reinforcing bars. The retaining wall 2 is manufactured in advance in a factory or the like before the construction of the embankment 1 on the water wall 10. In this embodiment, the retaining wall 2 has an L shape in a side view and a rectangular shape in a front view and a plan view. The lower surface 2a of the retaining wall 2 is formed flat. A plurality of connecting jigs 5 capable of connecting hanging tools are driven into the retaining wall 2. As the connection jig 5, a lift anchor or the like can be exemplified. The shape of the retaining wall 2 is not particularly limited. For example, the retaining wall 2 may have a rectangular shape or a T shape in a side view, or an L shape or a Z shape in a front view or a plan view.

  The water stopping material 3 is a water-impermeable member, and is formed of, for example, a bituminous material, a rubber material, a resin material, or the like. Although a liquid water-stopping material 3 that is solidified at the construction site can be used, it is preferable to use the water-stopping material 3 that is formed in a sheet shape in advance. Specifically, as the water-stopping material 3, for example, a bituminous joint plate, a bituminous fibrous joint plate, a rubber sheet, or a vinyl chloride sheet may be used.

  The sliding resistance material 4 is a member for preventing the retaining wall 2 from sliding against the water wall 10 and fixing the retaining wall 2, and is formed of a bituminous material, a rubber material, a resin material, or the like having a high frictional resistance to concrete. Although a liquid sliding resistance material 4 that is solidified at the construction site can be used, it is preferable to use a sliding resistance material 4 that is formed in a sheet shape in advance. Specifically, as the sliding resistance material 4, for example, a bituminous joint plate or a bituminous fibrous joint plate may be used.

  The water blocking material 3 and the sliding resistance material 4 can be made of the same member, or can be made of different types of members. The member having both the function of the water blocking material 3 and the function of the sliding resistance material 4 (water blocking material and sliding resistance material 3, 4) is formed of a bituminous material such as a bituminous joint plate or a bituminous fibrous joint plate. Can be exemplified.

  As shown in FIGS. 1 and 2, in the present invention, first, a waterproof material 3 and a sliding resistance material 4 are laid at predetermined positions on an upper surface 10 a of a water wall 10. This predetermined position is a position where the retaining wall 2 is to be installed. In this embodiment, as the water stopping material 3 and the sliding resistance material 4, the water stopping material and the sliding resistance material 3, 4 having both the function of the water stopping material 3 and the function of the sliding resistance material 4 are provided on the upper surface 10 a of the water barrier wall 10. I'm laying. The sliding resistance material 4 (water blocking material 3) and the upper surface 10a can be joined by an adhesive, or the sliding resistance material 4 can be simply laid without joining.

  Next, the retaining wall 2 is lifted using a heavy machine such as a crane, and the retaining wall 2 is placed on the water-stopping material 3 and the sliding resistance material 4 (water-stopping material and sliding resistance material 3, 4) laid in advance. . A process for providing a groove, a hole, or the like for installing the retaining wall 2 on the upper surface 10a of the waterfall wall 10 is not performed. That is, the processing for reducing the strength of the water wall 10 is not performed. By placing the retaining wall 2, the installation of the retaining wall 2 on the water wall 10 is completed. The lower surface 2a of the retaining wall 2 and the sliding resistance material 4 (water blocking material 3) are not joined, and the retaining wall 2 is simply placed.

  As shown in FIG. 3, in a state where the installation of the retaining wall 2 with respect to the water wall 10 is completed, the retaining wall 2 is arranged to extend in the Y direction, and is located between the upper surface 10 a of the water wall 10 and the lower surface 2 a of the retaining wall 2. And the water blocking material 3 and the sliding resistance material 4 are interposed. The water blocking material 3 is in a state of being continuously arranged in the extending direction (Y direction) of the retaining wall 2. In this embodiment, the waterproofing / sliding resistance material 3, 4, which also serves as the waterproofing material 3 and the sliding resistance material 4, is arranged in the entire range of the lower surface 2 a of the retaining wall 2, and the upper surface 10 a of the water barrier wall 10 and the retaining wall 10. 2 is not in contact with the lower surface 2a.

  The sliding resistance material 4 (water blocking material 3) is compressed by the weight of the retaining wall 2 and is pressed against the lower surface 2 a of the retaining wall 2 and the upper surface 10 a of the water wall 10. Since the sliding resistance member 4 generates frictional resistance between the lower surface 2a of the retaining wall 2 and the upper surface 10a of the water wall 10, the retaining wall 2 is formed on the upper surface 10a of the water wall 10 by the sliding resistance material 4. It will be in a fixed state. The force for fixing the retaining wall 2 to the upper surface 10a of the water wall 10 by the sliding resistance member 4 is greatly affected by the weight of the retaining wall 2 and the contact area between the lower surface 2a of the retaining wall 2 and the sliding resistance member 4. Therefore, it is desirable that the contact area between the lower surface 2a of the retaining wall 2 and the upper surface 10a of the water wall 10 be sufficiently large in order to obtain a strong fixing force. In other words, if a sufficient fixing force can be obtained, it is not necessary to dispose the sliding resistance member 4 over the entire range of the lower surface 2a of the retaining wall 2. On the other hand, the water blocking material 3 extends over the entire length of the retaining wall 2 in the extending direction in order to block water from the water area side. In this embodiment, the waterproof / sliding material 3 and 4 extend over the entire length of the retaining wall 2 in the extending direction.

  As shown in FIGS. 4 and 5, when the embankment 1 is constructed by arranging the plurality of retaining walls 2 in the Y direction, the retaining walls 2 are arranged adjacent to each other with the side surfaces 2 b facing each other, and the opposed retaining walls are arranged. The water-stopping material 6 is interposed between the side surfaces 2b. As the water stopping material 6 interposed between the retaining walls 2, the same member as the water stopping material 3 interposed between the water barrier wall 10 and the retaining wall 2 may be used, or another type of member may be used. You may. Between the side surfaces 2b of the retaining wall 2 extending in the Y direction, a water stopping material and a sliding resistance material having both the function of the water stopping material 6 and the function of the sliding resistance material 4 may be interposed.

  When the embankment 1 is constructed by arranging a plurality of retaining walls 2, after completing the work of laying the waterproof material 3 and the sliding resistance material 4 in all the planned installation areas of the retaining walls 2, the work of installing the retaining walls 2 is performed. The work of laying the waterproof material 3 and the sliding resistance material 4 and the work of installing the retaining wall 2 may be performed alternately. Further, the water blocking material 6 interposed between the side surfaces 2b of the retaining wall 2 can be installed or applied to the side surface 2b of the retaining wall 2 after the retaining wall 2 is placed on the upper surface 10a of the water barrier wall 10. Before placing the retaining wall 2 on the upper surface 10a of the water wall 10, the retaining wall 2 may be joined to the side surface 2b of the retaining wall 2 in advance. After placing the retaining wall 2 on the upper surface 10a of the water wall 10, additional work such as painting the upper surface 10a of the retaining wall 2 or the water wall 10 may be performed as necessary for the purpose of decoration, rust prevention, and the like. However, the processing which reduces the strength of the water wall 10 is not performed.

  In this way, the retaining wall 2 placed on the upper surface 10a of the water wall 10 is used as the embankment 1. At the time of a storm surge or the like, at least a part of the wave exceeding the waterfall wall 10 is blocked by the retaining wall 2 installed on the upper surface 10a of the waterfall wall 10. Even when a wave collides with the retaining wall 2, water leakage to the land side is prevented by the waterproof material 3 interposed between the upper surface 10 a of the water barrier wall 10 and the retaining wall 2, and water is prevented by the sliding resistance material 4 interposed. The retaining wall 2 can be sufficiently fixed to the wall 10.

  As described above, in the present invention, the installation of the retaining wall 2 is completed by placing the retaining wall 2 at a predetermined position with the water blocking material 3 and the sliding resistance material 4 interposed on the upper surface 10a of the water entering wall 10, The number of man-hours and labor can be greatly reduced as compared with a conventional embankment construction method that requires construction work for forming a groove or the like in the watershed wall 10. Since it is not necessary to perform a process of providing a groove, a hole, or the like on the waterfall wall 10, the strength of the waterfall wall 10 does not decrease.

  Further, in the present invention, after the embankment 1 is constructed, the embankment 1 can be easily removed and relocated as needed in a short time. For example, in normal times, the retaining wall 2, the water blocking material 3, and the sliding resistance material 4, or at least the retaining wall 2, is stored in a location different from a predetermined position of the water wall 10, and based on weather information on the typhoon. However, embankments can be built only when storm surges are expected. That is, the present invention can be used as a method of constructing a temporary embankment 1 in a place where it is desired to avoid installing the embankment 1 in normal times, such as a mooring facility, in addition to the method of constructing the permanent embankment 1. In a place where it is desired to avoid setting up the embankment 1 in normal times, if it takes a lot of time to construct and remove the embankment 1, the time required for the place to perform its original function is lost, and the present invention which can avoid this will be extremely effective. It is informative.

  In the present invention, it is not necessary to apply special processing to the waterfall wall 10, but when the upper surface 10a of the waterfall wall 10 is dirty or when the sliding resistance material 4 is coated with a slippery coating or the like on the upper surface 10a. Before constructing the embankment 1 as necessary, it is preferable to wash the upper surface 10a of the waterfall wall 10 and to perform a crepe treatment.

  As in this embodiment, when the waterproof material 3 and the sliding resistance material 4 are laid on the upper surface 10a of the water wall 10 before the retaining wall 2 is placed on the upper surface 10a of the water wall 10, the retaining wall 2 And the water stopping material 3 and the sliding resistance material 4 can be easily separated, so that when the water stopping material 3 and the sliding resistance material 4 deteriorate, they can be easily replaced with new ones.

  In the case where the liquid waterproof material 3 and the sliding resistance material 4 are applied to the upper surface 10a of the water barrier wall 10, it takes time until the waterproof material 3 and the sliding resistance material 4 solidify, but as in this embodiment. The use of the sheet-like waterproof material 3 and the sliding resistance material 4 is advantageous in that the work of laying the waterproof material 3 and the sliding resistance material 4 can be completed in a shorter time.

  When the same member (water-stopping material and sliding resistance material 3, 4) is used for the water-stopping material 3 and the sliding resistance material 4 as in this embodiment, different types of water-stopping material 3 and sliding resistance material 4 are used. Since the waterproof material 3 and the sliding resistance material 4 can be laid on the upper surface 10a of the water wall 10 with less man-hours than in the case where members are used, it is advantageous to shorten the construction period and reduce the labor of the workers. become.

  Furthermore, by using the same member (water-stopping material and sliding-resistance material 3, 4) for the water-stopping material 3 and the sliding-resistance material 4, the sliding-resistance material 4 is arranged over the entire lower surface 2 a of the retaining wall 2. It becomes possible. When the sliding resistance member 4 is arranged in the entire area of the lower surface 2a of the retaining wall 2, a large surface area of the sliding wall 10 and the sliding resisting member 4 in contact with the retaining wall 2 can be ensured. It is advantageous to prevent it.

  As in this embodiment, when the water blocking material 6 is interposed between the side surfaces 2b of the adjacent retaining wall 2, it is advantageous to increase the water blocking of the embankment 1. Therefore, it is not essential to interpose the water stopping material 6 between the side surfaces 2b of the retaining wall 2, but it is preferable to interpose the water stopping material 6. Before the retaining wall 2 is placed on the upper surface 10a of the water wall 10, if the waterproof material 6 is previously bonded to the side surface 2b of the retaining wall 2 at a factory or the like, the stop against the side surface 2b of the retaining wall 2 at the construction site. There is no need to position the water material 6 or the like.

  As shown in the embodiment illustrated in FIG. 6, before placing the retaining wall 2 on the upper surface 10 a of the water barrier wall 10, the waterproof material 3 and the sliding resistance material 4 are joined to the lower surface 2 a of the retaining wall 2 in advance. You can also. In this case, using a heavy machine such as a crane, the retaining wall 2 in which the water blocking material 3 and the sliding resistance material 4 are integrated in advance is lifted, and the retaining wall 2 is placed at a predetermined position on the upper surface 10 a of the water entering wall 10. Place. Thereby, the installation of the retaining wall 2 with respect to the water wall 10 is completed, and the embankment 1 is constructed on the water wall 10.

  In this embodiment, different types of members are used for the waterproof material 3 and the sliding resistance material 4. Further, a groove is formed in a lower portion of the retaining wall 2, and a water blocking material 3 and a sliding resistance material 4 are arranged in the groove. The water blocking material 3 and the sliding resistance material 4 project downward from the lower surface 2 a of the retaining wall 2 in anticipation of the amount of compression when the retaining wall 2 is placed on the upper surface 10 a of the water wall 10. The lower surface 2a of the retaining wall 2 may be flat as in the previous embodiment. However, when the range in which the water blocking material 3 and the sliding resistance material 4 are arranged is limited, the groove is formed as in this embodiment. The water stopping material 3 and the sliding resistance material 4 can also be provided.

  As shown in FIG. 7, when the retaining wall 2 is placed on the upper surface 10 a of the water wall 10, the water stopping material is provided between a part of the lower surface 2 a of the retaining wall 2 in which the groove is formed and the upper surface 10 a of the water wall 10. 3 and the sliding resistance material 4 are interposed, and the lower surface 2 a of the retaining wall 2 where the groove is not formed is in contact with the upper surface 10 a of the water wall 10.

  As shown in FIG. 8, in this embodiment, the embankment 1 is constructed by combining two types of retaining walls 2 of an L-shaped retaining wall 2 and a Z-shaped retaining wall 2 in plan view. A central portion of the embankment 1 in the extending direction (Y direction) is constructed by a Z-shaped retaining wall 2, and an end in the extending direction of the embankment 1 is constructed by an L-shaped retaining wall 2. The protruding portions of the retaining wall 2 and the notches of the retaining wall 2 adjacent to the retaining wall 2 are fitted to each other, and the retaining walls 2 are arranged adjacent to each other so that the protruding portions of the retaining wall 2 overlap in the X direction. are doing. The side surfaces 2b of the retaining wall 2 extending in the X direction are in contact with each other, and the waterproof material 6 is interposed between the side surfaces 2b of the retaining wall 2 extending in the Y direction.

  As shown in FIG. 9, in this embodiment, the water-stopping material 3 is disposed on the entire outer peripheral edge of the lower surface 2 a of each retaining wall 2, and a water area side of an inner region surrounded by the water-stopping material 3 is provided. Sliding resistance members 4 are arranged at two places on the land side. The central portion of the lower surface 2a of the retaining wall 2 where no groove is formed is in contact with the upper surface 10a of the water wall 10. Other configurations are the same as those of the embankment 1 of the previous embodiment illustrated in FIGS. 1 to 5.

  When the retaining material 3 and the sliding resistance material 4 are previously joined to the lower surface 2a of the retaining wall 2 before placing the retaining wall 2 on the upper surface 10a of the water wall 10 as in this embodiment, At the construction site, there is no need to lay the waterproof material 3 and the sliding resistance material 4 and to align the waterproof material 3 and the sliding prevention member 4 with the retaining wall 2. It becomes more and more advantageous to reduce the labor.

  When different types of members are used for the water stopping material 3 and the sliding resistance material 4, the water stopping material 3 having a small frictional resistance to concrete and the sliding resistance material 4 having no water impermeability can be used. The choice of the water material 3 and the sliding resistance material 4 increases. That is, there is a merit that a water stopping material 3 having more excellent water stopping properties and a sliding resistance material 4 having a larger friction resistance to concrete can be employed.

  When different types of members are used for the water blocking member 3 and the sliding resistance member 4, the water stopping member 3 may be arranged closer to the water area than the sliding resistance member 4 as in this embodiment. By arranging the water stopping material 3 on the water area side of the sliding resistance member 4, the possibility of water entering the sliding resistance member 4 can be reduced even when a wave collides with the retaining wall 2. Therefore, it is advantageous to stably maintain the frictional resistance of the sliding resistance material 4 high. As in this embodiment, it is preferable to provide the waterproof material 3 at the end of the retaining wall 2 on the water area side. However, even when the waterproof material 3 is provided at the center portion of the retaining wall 2, the sliding resistance material 4 can be used. The same effect can be obtained by arranging it closer to the land than the water blocking material 3.

  More preferably, as in this embodiment, the waterproof material 3 is arranged on the entire outer periphery of the lower surface 2 a of the retaining wall 2, and the sliding resistance material 4 is arranged in an inner region surrounded by the waterproof material 3. Good to do. By arranging the waterproof material 3 on all sides of the sliding resistance member 4, it is possible to more reliably prevent rainwater or the like from entering the sliding resistance member 4. Therefore, it is more and more advantageous to stably maintain the frictional resistance of the sliding resistance material 4 high.

  The same member (waterproof material and sliding resistance material 3, 4) can be used for the waterstop material 3 and the sliding resistance material 4 as in the previous embodiment. Also, in the above embodiment, different types of members can be used for the water blocking material 3 and the sliding resistance material 4 as in this embodiment.

  When the embankment 1 is constructed by combining the L-shaped retaining wall 2 and the Z-shaped retaining wall 2 in plan view as in this embodiment, the gap between the side surfaces 2b of the fitted retaining wall 2 is reduced. Since it does not communicate in a straight line in the X direction, even when a wave collides with the retaining wall 2, it becomes more difficult for water to pass between the adjacent retaining walls 2. Therefore, it is advantageous to increase the water shielding of the embankment 1. In addition, by arranging the L-shaped or Z-shaped projections of the retaining wall 2 in the X direction and arranging the projections adjacent to each other in a plan view, the water pressure applied to the retaining wall 2 having the projections in the water area side is reduced. Since the structure is also supported by the retaining wall 2 on the land side, each retaining wall 2 is less likely to slide with respect to the water wall 10. Therefore, it is more advantageous to enhance the stability of the embankment 1.

  When the embankment 1 is constructed by combining the L-shaped retaining wall 2 and the Z-shaped retaining wall 2 in plan view, the embankment 1 is stopped between the side surfaces 2 b extending in the X direction of the adjacent retaining walls 2. Although the water material 6 can be interposed, as in this embodiment, when the water stopping material 6 is interposed between the side surfaces 2b extending in the Y direction of the adjacent retaining walls 2, the minimum water stopping is achieved. The material 6 can effectively increase the water shielding of the embankment 1. In this embodiment, the embankment 1 is constructed by combining the L-shaped retaining wall 2 and the Z-shaped retaining wall 2 in plan view, but only the L-shaped retaining wall 2 in plan view is used. The embankment 1 can be constructed in combination, or the embankment 1 can be constructed by combining only the Z-shaped retaining walls 2 in plan view.

  In this embodiment, one sheet-like waterproof material 6 is interposed between the side surfaces 2b of the retaining wall 2, but before placing the retaining wall 2 on the upper surface 10a of the water-incoming wall 10, The water-stopping material 6 is joined to the side surface 2b of the retaining wall 2 in advance, and the water-stopping material 6 joined to the side surface 2b of the retaining wall 2 is brought into contact when the retaining walls 2 are arranged adjacent to each other. Thus, two waterproof materials 6 can be interposed between the side surfaces 2b of the retaining wall 2.

  In addition, in the embodiment exemplified above, the case where the linear embankment 1 extending in the extending direction (Y direction) of the waterfront wall surface 10 in plan view is illustrated, but in the present invention, the retaining wall 2 By changing the shape and arrangement, it is also possible to construct the embankment 1 having a bent shape or a curved embankment 1 in a plan view.

DESCRIPTION OF SYMBOLS 1 Embankment 2 Precast retaining wall 2a Lower surface of precast retaining wall 2b Side surface of precast retaining wall 3 Waterproofing material 4 Sliding resistance material 5 Connection jig 6 Waterproofing material 10 (interposed between sides of precast retaining wall) 10 Water barrier wall 10a Upper surface of water wall 10b Water surface

Claims (6)

  By placing the precast retaining wall at a predetermined position with a water blocking material and a sliding resistance material interposed on the upper surface of the water wall, the water blocking material is arranged continuously in the extending direction of the precast retaining wall. A method of constructing a dike, wherein the installation of the precast retaining wall is completed by using the precast retaining wall, and at least a part of the waves exceeding the watertight wall is blocked by the precast retaining wall installed on the upper surface of the watertight wall.   2. The embankment construction method according to claim 1, wherein before mounting the precast retaining wall on the upper surface of the waterfall wall, the waterproof material and the sliding resistance material are joined to the lower surface of the precast retaining wall in advance.   2. The embankment construction method according to claim 1, wherein before mounting the precast retaining wall on the upper surface of the water wall, the water blocking material and the sliding resistance material are laid in advance on the upper surface of the water wall. 3.   The embankment construction method according to any one of claims 1 to 3, wherein the same member is used for the water-stopping material and the sliding resistance material.   The embankment construction method according to any one of claims 1 to 3, wherein different types of members are used for the waterproof material and the sliding resistance material.   The embankment construction method according to claim 5, wherein the water-stopping material is disposed on a water area side of the water-resistant wall facing the sliding resistance material.

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