Reinforcement structure for embankment

Abstract

To provide a reinforcement structure for an embankment capable of effectively retaining a dam body against external forces generated during both overtopping and flood conditions.SOLUTION: A reinforcement structure for an embankment 1 comprises a concrete wall body 3 placed on a dam body 2. The plurality of concrete wall bodies 3 are formed in a front-back symmetrical prestressed concrete structure, and are arranged adjacently in a length direction of the dam body 2 so as to form a self-supporting earth retaining structure 8.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reinforcing structure for an embankment that reinforces an existing embankment. [Background technology]

[0002] In river embankments, there is concern that the embankment body may collapse due to rising water levels or overflowing. To address this, a reinforcement structure has been disclosed in which a single row of steel sheet pile walls or two rows of steel sheet pile walls connected by tie rods are embedded continuously along the length of the embankment body to reinforce the embankment against external forces that could cause the embankment to collapse during floods, etc. (See, for example, Patent Document 1).

[0003] Also, a bank reinforcement structure using prestressed concrete sheet piles (so-called PC sheet piles) has been disclosed (see, for example, Patent Document 2).

[0004] Also, a reinforcement structure has been disclosed in which a row of steel sheet piles is reinforced with steel pipes or H-shaped steel to provide rigidity and prevent the collapse of the bank (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-13451 [Patent Document 2] Japanese Patent Publication No. 2022-18314 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-132169 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been an increase in river flooding and levee breaches due to heavy rain, and there is a demand for technology to reinforce existing levees. Specifically, there is a demand for technology to reinforce levees that will not collapse even when the levee breaches or the original ground is scoured due to overflowing water on the opposite side of the river (hereinafter referred to as the "back side"), or when the levee is eroded by rising water on the river side (hereinafter referred to as the "front side").

[0007] In the structure described in Patent Document 1, in which a steel sheet pile wall is provided in a single row, or in the structure described in Patent Document 2, in which a single row of PC sheet piles is provided, the rigidity (cross-sectional performance) of the sheet pile wall is low, so if the embankment on the back side of the river is eroded during overflow and an external force is applied, the steel sheet piles may not be able to withstand the force and the embankment may collapse. Also, the structure described in Patent Document 1, in which two rows of steel sheet pile walls are connected by tie rods, requires a special construction method, which results in a longer construction period and increased costs.

[0008] Furthermore, in the structure described in Patent Document 3 above, which reinforces a row of steel sheet pile walls, the reinforcing material is located either on the river front side or the river back side, and can only withstand external forces from one side, so it cannot cope with both cases where the embankment on the river back side is eroded by overflowing water, and where the embankment on the river front side is eroded by rising water.

[0009] The present invention has been made in consideration of these points, and aims to provide a reinforcing structure for a levee that can effectively hold the levee body against external forces that occur during both overflow and flooding. [Means for solving the problem]

[0010] The embankment reinforcement structure described in claim 1 comprises a concrete wall body poured into the embankment body, the concrete wall body being a prestressed concrete structure symmetrical from front to back, and multiple concrete walls being arranged adjacent to each other along the length of the embankment body to form a self-supporting earth retaining structure.

[0011] The reinforcing structure for a levee according to claim 2 is the reinforcing structure for a levee according to claim 1, further comprising a closing portion for closing the joint between adjacent concrete walls.

[0012] The embankment reinforcement structure described in claim 3 is the embankment reinforcement structure described in claim 1 or 2, which is provided with a soil cement wall formed around the area between adjacent concrete walls and integrating the wall surface of the concrete wall with the soil of the embankment. [Effects of the Invention]

[0013] According to the present invention, it is possible to effectively hold the embankment against external forces that occur during both overflow and flooding. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically showing a reinforcement structure of an embankment according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view schematically showing the reinforcing structure. [Figure 3] 1A and 1B show a concrete wall used in the reinforced structure, in which (a) is a side view and (b) is a plan view. [Figure 4] 1A and 1B are plan views showing the construction state of a concrete wall in the same reinforced structure, where FIG. 1A shows one example and FIG. 1B shows another example. [Figure 5] This is an explanatory diagram showing the design method of the above reinforcement structure (calculation model for overflow). DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] In Figures 1 and 2, 1 indicates a levee. The levee 1 is a reinforced structure in which a levee body 2 formed by earthworks is reinforced with multiple concrete walls 3 poured into it. In this embodiment, the levee 1 is a river levee, and is formed with its length direction aligned with the water flow direction of a river 4. In other words, the length direction of the levee 1 (levee body 2) is perpendicular to the plane of the paper in Figure 1.

[0017] The embankment body 2 is exemplified as having slopes that slope downward from the tops of the slopes at both ends of the crest 5 to both the river front and river back sides. In this embodiment, the embankment body 2 is formed by rising from the original ground surface G at the foot of the slope. In other words, the original ground surface G is the lower end of the embankment body 2, and in the illustrated example, it is flush or nearly flush with the riverbed of the river 4.

[0018] The concrete wall 3 is a precast concrete member (column) with a straight, longitudinal shape known as a PC wall. In this embodiment, it has a rectangular (including square) cross-sectional shape. The concrete wall 3 is a prestressed concrete structure with front and back symmetry, and has the same rigidity (cross-sectional performance) in either direction. The concrete wall 3 is embedded in the embankment body 2 from the top 5 of the embankment body 2, with its longitudinal direction extending vertically. Adjacent concrete wall 3 are arranged in succession along the length of the embankment body 2, and their upper ends are connected to each other by a cast-in-place concrete cap 6, forming a diaphragm wall. The concrete wall 3 is embedded in the embankment body 2 so that its lower end is located below the original ground surface G, forming a free-standing earth-retaining structure 8. The free-standing earth-retaining structure 8 is a single-layer structure in which the concrete wall 3 is formed in a row along the length of the embankment body 2 and can be installed anywhere within the crest 5. The cast-in-place concrete cap 6 is located at the upper end of the concrete wall 3.

[0019] Examples of a concrete wall 3 according to this embodiment are shown in Figures 3(a) and 3(b). In the illustrated example, the concrete wall 3 is formed in a rectangular shape (including a square shape). The concrete wall 3 has a circular hollow portion 11 formed in the center of a main body 10 made of concrete. The main body 10 is formed with prestressing steel members 12 that apply tension and reinforcing spiral reinforcement 13 embedded therein, and both ends of the prestressing steel members 12 are held by seat plates 14 located at the ends of the main body 10.

[0020] Preferably, each concrete wall 3 has a groove-shaped grout hole 16, which is a semicircular or semielliptical joint filling hole for filling the joints between adjacent concrete wall 3, formed in one of the pair of opposing side surfaces 10a, 10a of the main body 10. The multiple concrete wall 3 are arranged adjacent to each other with their side surfaces 10a facing each other. That is, the concrete wall 3 is arranged so that their side surfaces 10a are aligned along the length of the embankment body 2. As shown in FIG. 4(a) or 4(b), mortar M or soil cement is filled into the grout hole 16 between adjacent concrete wall 3 and hardened, forming a blocking portion 17 and a soil cement wall 18 that watertightly block the joints between the adjacent concrete wall 3. In other words, the multiple concrete wall 3 are configured to function as a watertight wall by the blocking portion 17.

[0021] 3(a) and 3(b), the concrete wall 3 is formed in a longitudinal shape by welding an upper member 20 and a lower member 21 at the position of the end seat plate 14. The lower member 21 is buried below the original ground surface G.

[0022] Next, a design method for the reinforcement structure of the levee 1 (a calculation model for when water overflows) will be explained.

[0023] As shown in the calculation model in Figure 5, the design method for overflowing is based on the assumption that the levee on the back side of the river is eroded by the overflow and completely washed away, and furthermore, considering the effect of scouring of the original ground, the design reference surface G1 is set lower than the original ground surface G. Also, it is assumed that the river water penetrates into the levee on the front side of the river and becomes completely saturated, and the hydrostatic pressure p according to the overflow water level L is calculated. w is applied to the concrete wall 3 from the river side. In addition, in the figure, q is the superimposed load, p a is earth pressure, k H indicates the ground spring (horizontal ground reaction coefficient).

[0024] The construction method for the concrete wall 3 in the present invention can be selected arbitrarily depending on the ground conditions and construction conditions, for example, the inner excavation press-in method, pre-boring method, TRD method, self-propelled press-in method, and the like.

[0025] For example, in the central excavation press-in method, a ruler is placed on the top 5 of the embankment body 2 along the centerline of the concrete wall body 3, and the lower member 21 of the concrete wall body 3, with an auger screw inserted into the hollow portion 11, is lifted by an auxiliary crane and placed at the casting position defined by the ruler. Compressed air is then discharged from the auger head to excavate and remove soil while the lower member 21 is pressed into the embankment body 2 and sunk. Next, the upper member 20 of the concrete wall body 3, with an auger screw inserted into the hollow portion 11, is erected by the auxiliary crane. The lower end of the upper member 20 is welded to the upper end of the lower member 21, and the upper member 20 is pressed into the embankment body 2 and sunk in the same way as the lower member 21, and the auger screw is then withdrawn. After sunk in this manner, multiple concrete wall bodies 3 are successively placed adjacent to each other and connected to each other with connecting plates. Then, the inside of the grout hole 16 shown in Figure 4(a) is washed to the required depth with high-pressure jet water, and after removing the soil and sand from the grout hole 16, a mortar filling bag is inserted into the grout hole 16, and mortar M is pumped into the mortar filling bag to fill it and harden, thereby forming a blocking portion 17.

[0026] In the pre-boring method, similar to the central excavation and press-in method, a ruler is placed on the top 5 of the embankment body 2 along the centerline of the concrete wall 3, and a borehole is drilled from the top 5 of the embankment body 2 at the position determined by the ruler. To drill the borehole, air is discharged from the auger head, and the auger drive device is moved up and down while injecting cement milk into the borehole to the desired depth. Next, the upper and lower members 20 and 21 are welded together, and the concrete wall 3 is lifted by an auxiliary crane and lowered into the borehole. After multiple concrete wall bodies 3 are lowered adjacent to each other in this manner, adjacent concrete wall bodies 3 are connected with connecting plates. As a result, as shown in Figure 4(b), adjacent grout holes 16 in the concrete wall 3 are filled with soil cement S, which is a mixture of cement milk and the soil and sand of the embankment body 2, forming a soil cement wall 18 and a blockage section 17.

[0027] The upper ends of adjacent concrete walls 3 are connected by integrally forming a cast-in-place cap concrete 6.

[0028] The reinforcement structure constructed in this way is designed to meet the strict conditions that assume that when the river 4 overflows, the embankment 2 on the back side of the river will be completely washed away, scouring the original ground, and the river water will penetrate the embankment 2 on the front side of the river and become completely saturated. Therefore, the self-supporting earth retaining structure 8 will remain independent even when the river overflows.

[0029] That is, according to one embodiment, a plurality of concrete walls 3, each having a high bending rigidity and a front-to-back symmetrical prestressed concrete structure, are arranged adjacently along the length of the embankment body 2 to form a self-supporting earth-retaining structure 8. This effectively protects the embankment body 2 against external forces generated by erosion of the embankment body 2 on the backside during overflow and against external forces generated by erosion of the embankment body 2 on the frontside during flooding, thereby constructing a strong embankment 1 that maintains the height of the embankment body 2's crest 5. In other words, conventional steel sheet piles require special construction methods (such as two rows), and methods that reinforce a single row of steel sheet piles can only reinforce the embankment body 2 against external forces from either the front or backside of the river. In contrast, the concrete wall 3 of this embodiment is symmetrical from the front to the back and has the same rigidity (cross-sectional performance) in either direction. Therefore, even with a single row of construction, the embankment body 2 can be sufficiently reinforced against external forces from both the front and backside of the river.

[0030] The above-mentioned reinforcement structure can be formed by burying a row of concrete walls 3 from the top of the embankment body 2 of the existing embankment 1, so it can be easily constructed while maintaining the functionality of the existing embankment 1. In addition, because the construction process is simple, it is possible to shorten the construction period and carry out construction at low cost.

[0031] Furthermore, since the concrete wall 3 can have welded joints at its upper end, it can easily be raised in the future.

[0032] The self-supporting earth retaining structure 8 made up of concrete walls 3 functions as a watertight wall because the joints between adjacent concrete walls 3 are closed with closing sections 17, making it possible to prevent seepage even when the embankment body 2 is made of sandy ground. In particular, when constructed using the pre-boring method, a soil cement wall 18 is formed around the concrete wall 3, so the wall surface of the concrete wall 3 and the soil of the embankment body 2 become one, resulting in a structure that prevents water seepage from the top 5.

[0033] Furthermore, because the reinforcement structure is designed to meet the above-mentioned strict conditions, it exhibits sufficient stability against erosion and infiltration caused by the normal action of flowing water from the river 4 below the crest height, as well as infiltration caused by rainfall. [Explanation of symbols]

[0034] 1. Embankment 2 Embankment body 3 Concrete wall 8 Freestanding earth retaining structure 17 Occlusion 18 Soil cement wall

Claims

1. It is equipped with a concrete wall that is poured into the embankment, The concrete wall is a prestressed concrete structure with front and back symmetry, and a plurality of walls are arranged adjacent to each other in the longitudinal direction of the embankment to form a self-supporting earth retaining structure. A reinforced embankment structure characterized by:

2. Equipped with a sealing part that seals the joints between adjacent concrete walls 2. The reinforcing structure for embankments according to claim 1.

3. A soil cement wall is formed around the periphery of adjacent concrete walls, integrating the wall surface of the concrete wall with the soil of the embankment.

3. The reinforcing structure for embankments according to claim 1 or 2.

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