JP2017166291A - Composite banking structure having reinforced soil structure and overlaid fill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite banking structure which can reduce a construction cost of a reinforced soil structure, which has high safety, and which can suppress slip of economical and workable overlaid soil.SOLUTION: A composite banking structure comprises a reinforced soil structure 10 and overlaid fill 20, and a crown reinforcement layer 30 is formed in a crown part of the overlaid fill 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite embankment structure applicable to roads, railways, embankments and the like, and more particularly to a composite embankment structure having a reinforced soil structure and an upper embankment suitable when the upper embankment is a high embankment.

Reinforced soil structures are roughly classified as “reinforced soil walls” where the slope of the slope (wall slope) is steeper than 1: 0.6, and “reinforced embankments” where the slope is 1: 0.6 or less. Yes.
Many methods are proposed for the construction of reinforced earth structures, such as reinforced embankment method using geotextile, reinforced earth wall method using strip steel, or anchor type reinforced embankment wall method using bar steel with bearing plate. (Patent Documents 1 to 5), and a construction method is appropriately selected in consideration of the on-site surrounding environment, design strength, construction cost, construction period, and the like.
Although these methods differ in the type of reinforcement by the reinforcing material, the stability of the embankment is compensated by the frictional resistance or bearing resistance between the reinforcing material laid inside the embankment and the slope of the slope is kept steeper than the standard gradient. In common.
Generally, based on a simple design method, a reinforced soil structure is designed by checking the following evaluation items.
The evaluation items are “internal stability” in which the slip of the part through which the reinforcing material passes is set, the density, strength, and total length of the reinforcing material are selected to check the stability of the reinforcing region itself, and the reinforcing region "External stability" that checks the stability of the entire virtual retaining wall surrounding it (falling, sliding, supporting force), and the reinforced area itself has a predetermined safety against the surrounding ground It is three evaluation items of “total stability” to check whether the rate (slip failure across the outside of the reinforced soil structure and the reinforced area, subsidence of foundation ground, liquefaction during earthquake) can be secured.

  In addition, as shown in FIG. 6, when the upper embankment (lifting embankment) b of the high embankment is present at the upper part of the reinforced soil structure a, the impact at the time of collapse is greater than that of the medium-scale embankment. There is a need for more careful and detailed examination of multiple evaluation items.

Japanese Patent Laid-Open No. 57-140424 (FIGS. 1 and 2) JP-A-9-279580 (FIG. 1) JP-A-6-322769 (FIG. 1) Japanese Patent Laid-Open No. 6-220855 (FIG. 1) Japanese Patent Laying-Open No. 2001-182065 (FIG. 1)

When the upper embankment of the high embankment is located above the reinforced soil structure a, there are the following problems to be solved in designing the reinforced soil structure a.
<1> The design method of the reinforced soil structure a in the case of high embankment is not clearly established.
Therefore, although the reinforced soil structure a is designed based on the simple design method which is a conventional design method, much time and labor are required for the design.
<2> When designing the reinforced soil structure a, it is necessary to check the arc slip line (surface) generated in the upper embankment b.
When only the road surface c exists at the top end of the upper embankment b, in order to obtain the height H ₁ and the depth L ₁ of the reinforced soil structure a, an arc slip line s is placed at the step position or the shoulder position of the upper embankment b. Not only ₁ and s ₂ but also arc slip lines s ₃ and s ₄ reaching the top must be assumed.
<3> When arc slip lines s ₃ and s ₄ reaching the top end are assumed, in order to deal with these arc slip lines s ₃ and s ₄ , the depth L ₁ (reinforcing material) of the reinforced earth structure a The total length).
<4> Effect and the increase of the high embankment than the middle embankment fill collapse, from the viewpoint of enhancing the safety factor of the soil structure, depth L ₁ of the reinforced soil structure a is an extra long dimension than normal The actual situation is estimated.
When easily be described to understand the design length of the regular depth L ₁ of the reinforced soil structure a is, even for example reinforced soil structure height 1.5 times the length of an H ₁ of a, eventually reinforcement It has been estimated to excessive to a height 2-3 times the length of an H ₁ of the soil structure a.
<5> As described above, conventionally, because the depth L ₁ of reinforced soil structures a estimated longer than necessary, has become a very expensive design.
That is, the dimension of depth L ₁ of the reinforcing region, have a significant impact on walking hanging of reinforced soil structures a, the depth L ₁ of the reinforcing region is even slightly longer, only increase the construction cost of reinforced soil structures a In addition, the construction period is prolonged and the yield gets worse.
In a site where the supporting capacity of the supporting ground is insufficient, additional work for reinforcing the supporting ground is required, and the yield is further deteriorated.
<6> At present, more than 30 types of construction methods have been proposed for the reinforced earth wall construction method alone depending on the wall material and the reinforcing material, and the performance (safety and durability), the construction unit price, etc. are different for each construction method.
From the viewpoint of public structures, it is most important to select a performance-priority construction method suitable for the site, but the construction cost, which is an important construction method selection criterion, becomes an obstacle, and a performance-priority construction method. Selection is hindered.
Therefore, if the construction cost of the reinforced soil structure a can be reduced even with the existing construction method, the feasibility of selecting a performance-priority construction method suitable for the local area will be high, so it is desirable to propose a technique for improving construction cost reduction. ing.
<7> Earth structures such as road embankments and railroad embankments suffered damage such as slippage collapse due to the recent large earthquakes, and the main transportation network was severed everywhere, and securing emergency transportation routes remained a major issue.
In particular, it is possible to reinforce the existing earth structure and increase the vibration resistance, but it is possible to reinforce the entire cross section of the earth structure over a long distance because the economic burden is extremely large. Poor sex.
<8> In the conventional earth structure, when the earthquake motion exceeding the assumption is repeatedly received, the upper embankment b collapses along the primary slip line, and further, the upper embankment b collapses along the secondary and tertiary slip lines on the back side. Progresses.
To secure the road network in the event of an earthquake disaster, it is highly safe and economical to break the chain of slips such as secondary and tertiary slips and leave a width that allows emergency vehicles to pass on the road surface c. Proposal of a slip suppression technology for top embankment that is effective and effective is highly desired.

  The present invention has been made in view of the above-described points, and the object of the present invention is to realize the construction cost of the reinforced earth structure even in the existing construction method in order to realize the construction method having the performance suitable for the site. It is an object of the present invention to provide a composite embankment structure having a reinforced soil structure and an upper embankment that can reduce the slippage of the upper embankment, which is low in safety, is economical, and that is economical and effective.

The present invention relates to a reinforced soil structure in which a reinforcing material is embedded in the embankment, and a composite embankment structure in which an upper embankment is positioned above the reinforced earth structure, and the embankment material is provided at a top end portion of the upper embankment. It is characterized by having a top end reinforcing layer having a predetermined layer thickness which is held and restrained by a planar reinforcing material, and the arc slip line starting from the top end of the upper embankment is eliminated.
In another embodiment of the present invention, the elongation rate of the planar reinforcing material of the top end reinforcing layer is less than or equal to the elongation rate of the reinforcing material of the reinforced soil structure.
In another embodiment of the present invention, the top end reinforcing layer may have a uniform thickness or a non-uniform thickness.
In another embodiment of the present invention, the top end reinforcing layer is constituted by a constrained soil mat in which one or more laminated layers are formed by holding a banking material with a planar reinforcing material.
In another embodiment of the present invention, the reinforced soil structure located at the top of the upper embankment is either a reinforced embankment or a reinforced soil wall.
In another embodiment of the present invention, when the upper embankment is a high embankment, a small-stage reinforcing material may be embedded in the small-stage position.
In another embodiment of the present invention, the upper embankment may be a road embankment, and may include a top end reinforcing layer that is wrapped with a planar reinforcing material including a roadbed or a roadbed directly below the road surface.

  The present invention can reduce the construction cost of the reinforced soil structure even with an existing construction method, and can suppress slipping of the overfill with high safety, economy, and effectiveness.

Model diagram of composite embankment structure according to the present invention Model diagram of reinforced embankment Model of multi-anchor reinforced earth wall Model of tail arme reinforced earth wall Geotextile reinforced earth wall model Model diagram of double wall type reinforced earth wall An enlarged model of the top edge of the top embankment with a uniform thickness top reinforcement layer Magnified model of the top edge of the top embankment with a non-uniform thickness top layer reinforcement layer Model diagram of conventional earth structure to explain the design method of reinforced earth structure in high embankment

  Hereinafter, the present invention will be described with reference to the drawings.

<1> Outline of Composite Embankment Structure With reference to FIG. 1, the composite embankment structure according to the present invention is located at a reinforcing earth structure 10 located at the heel and an upper part of the reinforcing earth structure 10. The upper embankment 20 and the top end reinforcing layer 30 obtained by reinforcing the embankment material of the top end of the upper embankment 20 with a predetermined layer thickness are configured.
A road surface 40 is formed on the upper surface of the top end reinforcing layer 30, and an automobile or a train can travel through the road surface 40.

The composite embankment structure according to the present invention eliminates the arc slip line (surface) starting from the top end of the upper embankment 20 by combining the top end reinforcing layer 30 with the reinforced earth structure 10, and limiting the generation position outside the position of the top end reinforcement layer 30 (slope face a range of overburden embankment 20), the depth L ₂ is a reinforced region of the final reinforced soil structure 10 significantly reduced as compared to conventional It ’s what you get.
As a result, it is possible to economically design the reinforced soil structure 10 in order to select a construction method with performance suitable for the site, and to prevent the road surface 40 from being slipped by suppressing the slip of the overfill in the event of an earthquake. It is possible to avoid emergency damage and secure emergency transportation routes.

<2> Reinforced soil structure The reinforced soil structure 10 is a soil structure in which a reinforcing material is embedded in the embankment.
Although illustrated about the reinforced earth structure 10 below, the reinforced earth structure 10 is not limited to these illustrations, and contains various well-known earth structures.

<2.1> Reinforced Embankment FIG. 2 shows a model diagram when the reinforced earth structure 10 is a reinforced embankment 10A.
The reinforcing embankment 10 </ b> A uses a steel net, a lattice-like or planar geotextile made of a polymer material as the reinforcing material 12, and both the plurality of reinforcing materials 12 embedded in the plurality of embankment layers 11 and the embankment material. It is a soil structure that is integrated by the frictional force of the soil so as to exhibit the earth retaining effect.

<2.2> Reinforced earth wall (FIGS. 3A to 3E)
The reinforced soil structure 10 (10A to 10D) is a reinforced soil including a wall surface material 15 for protecting a slope, a reinforcing material 12 connected to the back side of the wall surface material 15, and an embankment layer 11 in which the reinforcing material 12 is embedded. It may be a wall.
The wall surface material 15 is appropriately selected from, for example, a concrete panel, a concrete block, a steel frame (welded wire mesh, expanded metal), cast-in-place concrete, and the like.
The reinforcing material 12 includes, for example, a steel bar with an anchor plate, a strip-shaped steel material, a grid or planar geotextile made of a steel net or a polymer material, a geogrid, or the like.
The typical reinforced earth wall is illustrated below.

<2.2.1> Multi-anchor reinforced earth wall (Fig. 3A)
The multi-anchor reinforced earth wall 10B uses a concrete panel or a concrete block for the wall surface material 15 and uses a steel bar with an anchor plate 16 as the reinforcing material 12, and a plurality of reinforcing materials connected to the back surface of the wall surface material 15. This is a soil structure that exerts the earth retaining effect by utilizing the pulling resistance force of the twelve anchor plates 16.
As the embankment reinforcement mechanism, the embankment material sandwiched between the wall surface material 15 and the anchor plate 16 is restrained and reinforced to increase the strength of the earth structure.

<2.2.2> Tail Arme reinforced earth wall (Fig. 3B)
The tail arme type reinforced earth wall 10C uses a concrete panel or a concrete block for the wall surface material 15 and uses a strip-shaped steel material for the reinforcing material 12, and includes a band-shaped reinforcing material 12 embedded in the embankment layer 11 and the embankment material. It is a soil structure that exerts the earth retaining effect by pulling resistance force by frictional force.
As the embankment reinforcement mechanism, the strength of the earth structure is increased by a pseudo adhesive force by a plurality of steel strip reinforcements 12 embedded in the embankment.

<2.2.3> Geotextile reinforced earth wall (Fig. 3C)
The geotextile reinforced earth wall 10D uses a steel net or a lattice-like or planar geotextile as the reinforcing material 12, and a frictional force between the planar reinforcing material 12 embedded in the embankment layer 11 and the embankment material. It is a soil structure in which the earth retaining effect is exhibited by the pulling-out resistance force and the interlocking effect.
As the wall surface material 15, a steel frame (welded wire mesh, expanded metal) having a gradient or a concrete block for a straight wall is selectively used according to the slope of the slope.
Although not shown, a non-woven reinforcing material having a drainage function is used in combination as necessary.

<2.2.4> Double wall reinforced earth wall (Fig. 3D)
The double wall type reinforced earth wall 10E represented by an adem wall uses a concrete panel or a concrete block for the wall material 15, and uses a steel net or a lattice or planar geotextile for the reinforcing material 12. It is a soil structure of a double wall structure in which a space 16 for deformation absorption is formed between an embankment body reinforced by embedding a planar reinforcing material 12 in the embankment layer 11 and a wall surface material 15. 13 and the embankment body are connected by a belt-like connecting material.
Since the space 16 filled with the fine aggregate or coarse aggregate exhibits the deformation absorbing action on the front surface of the embankment body, the compaction near the wall surface material 15 is sufficiently performed without affecting the wall material 15 with the rolling load of the embankment. It is possible to build a high quality embankment.

<3> Upper embankment The upper embankment 20 is a road embankment, a railway embankment, a bank, etc. with a standard gradient (35 ° or less).
In this example, although the case where the upper embankment 20 is a high embankment in which one or more small steps 21 are formed in the middle of the slope is shown, the height of the upper embankment 20 is not limited in principle.
The "high embankment", the ratio of the height H ₂ of the height H ₁ and the upper mounting embankment b of reinforced soil structure 10 was 1: 1 or greater, embankment height H (reinforced soil structure a the sum of the height _{H 2} of the height _{H 1} and the upper mounting embankment b) refers to a more soil structure 15-20 meters.

<4> Top edge reinforcing layer (Figs. 4 and 5)
The top end reinforcing layer 30 is a high shear strength reinforcing layer having a predetermined layer thickness in which the embankment material 22 at the top end including the roadbed and roadbed immediately below the road surface 40 is held and restrained by the planar reinforcing material 31. is there.
In other words, the top end reinforcing layer 30 is a reinforcing layer in which the top end portion of the upper embankment 20 on which the greatest acceleration acts during an earthquake is efficiently reinforced with the planar reinforcing material 31, and is formed on the top end portion of the upper embankment 20. It is a structure in which the embankment slope surface is wound by the laid planar reinforcing material 31, and the integration effect of the top of the embankment is exhibited by the restraining effect of the planar reinforcing material 31.
For the planar reinforcing material 31, for example, a lattice-shaped or planar geotextile made of a polymer material or a geogrid can be used.

<4.1> Reason for reinforcing the top edge The reason why the top edge reinforcing layer 30 is formed on the top edge of the upper embankment 20 is not only to increase the effect of preventing the collapse of the shoulder of the upper embankment 20 during an earthquake. This is for the purpose of designing the depth of the reinforcing soil structure 10 of the hoshijiri by eliminating the arc slip line starting from the top edge of the upper embankment 20.
Although several top end reinforcement layers 30 are illustrated below, the top end reinforcement layer 30 is not limited to the illustrated form, and a known reinforcement structure can be applied.

<4.2> Top end reinforcement layer formed with uniform thickness FIG. 4 (A) shows a form in which the top end portion of the upper embankment 20 on which the greatest acceleration acts during an earthquake is composed of a top thickness reinforcement layer 30 of uniform thickness. .
The top end reinforcing layer 30 is a laminated structure of a plurality of constrained soil mats 35 formed by holding the embankment material 22 with a planar reinforcing material 31 and has a width that can cross the top end of the upper embankment 20.
In the case where a plurality of constrained soil mats 35 are stacked and connected, the upper and lower sides of adjacent constrained soil mats 35 are connected to each other by a known connector 34, so that the integrity of the constrained soil mats 35 is increased and the horizontal movement is suppressed. The effect and overall bending rigidity can be increased.

<4.2.1> Restraint Mat An example of the restraint soil mat 35 is shown in FIGS.
The constrained soil mat 35 shown in FIG. 4 (B) has the embankment material 22 spread out in layers on the upper surface of a horizontally laid planar reinforcing material 31 and compacted, and covers the entire circumference including the slope of the embankment material 22. It is formed in a mat shape by being wound with a reinforcing material 31.
Since the planar reinforcing material 31 restrains the embankment material 22, the restraint soil mat 35 has a strong structure, and the collapse displacement of the embankment material 22 during an earthquake can be effectively prevented.
If the upper and lower surfaces of the constraining soil mat 35 are connected to each other by a connecting material such as a bar or a belt as necessary, the bending strength (rigidity) of the constraining soil mat 35 is further increased.

<4.2.2> Restraint Mat with Double Structure The restraint soil mat 35 shown in FIG. 4C includes a plurality of sandbags 33 in which the embankment material 22 is packed in a sandbag 32 and a planar reinforcing material 31. A constrained soil mat 35 is formed by laying a plurality of sandbags 33 on the top surface of the planar reinforcing material 31 and winding the sandbag 33 so as to wrap the periphery of the plurality of sandbags 33 with the planar reinforcing material 31. .
The embankment material 22 is partitioned and restrained by a plurality of sandbags 32 and has a double restraint structure with the sandbag 32 and the planar reinforcing material 31. Therefore, even if a low-quality material is used for the embankment material 22, the restraint soil is used. High bending strength can be imparted to the mat 35.

<4.2.3> Number of laying of restraint mats In this example, a case where a plurality of restraint soil mats 35 are laminated to form the top end reinforcing layer 30 having a uniform thickness is shown. You may comprise the restraint soil mat 35.

<4.3> Top End Reinforcement Layer Formed with Uneven Thickness FIG. 5 shows another form in which the top end portion of the upper embankment 20 is configured with a top end reinforcement layer 30 with a nonuniform thickness.
The crest reinforcing layer 30 has a central portion 36 located immediately below the road surface 40, consists Law surface 37. which is integrally connected to the end of the central portion 36, the layer thickness t ₁ of the central portion 36 is legal surface Compared with the layer thickness t _{2 of} 37, the layer thickness is non-uniform so as to have a relatively thin relationship.
A downward constraining recess 38 is formed at the center of the lower surface of the top end reinforcing layer 30, and the constraining recess 38 and the central peak portion 23 of the upper embankment 20 are in close contact with each other.
Equivalent to that central peak portion 23 of the upper mounting embankment 20 to be embraced by restrained by three sides of the high rigidity constraint recess 38, forming a top end reinforcement layer 30 with a uniform thickness of layer thickness t ₂ of the law face 37 The seismic effect is obtained.
The top end reinforcing layer 30 of this example can be constructed by, for example, laminating a plurality of the above-mentioned restrained soil mats 35 having different lengths (widths).

[Characteristics of composite embankment structure]
Next, the main characteristics of the composite embankment structure will be described.

<1> Reason why an arc slip line starting from the top end does not occur In the present invention, the top end portion of the upper embankment 20 is reinforced with an appropriate layer thickness as shown in FIG. By forming the top embankment reinforcement layer 30 made of high embankment, the occurrence of arc slip lines starting from the top reinforcement layer 30 is eliminated.
The reason why the arc slip line starting from the top end reinforcing layer 30 does not occur is that the elongation rate of the planar reinforcing material 31 that is the reinforcing material of the top end reinforcing layer 30 is the extension rate of the reinforcing material 12 of the reinforced earth structure 10. This is because the relationship is smaller or equal.
That is, when the elongation rate of the planar reinforcing material 31 of the top end reinforcing layer 30 is larger than the elongation rate of the reinforcing material 12 of the reinforced soil structure 10, the shear force (strength) of the earth and sand on the top end side with respect to the tail end side. Therefore, the earth and sand on the top end side of the upper embankment 20 can easily move during an earthquake, and an arc slip line starting from the top end is easily generated.
In the present invention, paying attention to the relationship between the elongation rates of the planar reinforcing material 31 and the reinforcing material 12, the planar reinforcing material 31 and the reinforcing material 12 are connected to each other in order not to generate an arc slip line starting from the top reinforcing layer 30. The growth rate relationship.

<2> Number of Arc Slip Lines of Overlay Embankment When the top edge reinforcing layer 30 does not exist, a large number of arc slip lines s ₃ and s ₄ passing through the top edge of the top embankment b as shown in FIG. It was necessary to design the reinforced soil structure a for the Houshiri, assuming.
On the other hand, since the top end reinforcing layer 30 is formed at the top end portion of the upper embankment 20, it is not necessary to consider the arc slip line starting from the top end reinforcing layer 30. The number of arc slip lines can be greatly reduced.
<3> Depth of Reinforced Earth Structure As described above, the top edge reinforcing layer 30 is formed at the top edge of the upper embankment 20 shown in FIG. As a result, the generation position of the arc slip line can be limited to the outer position of the top end reinforcing layer 30 (the arc slip lines S ₁ and S _{2 in the} range of the slope of the upper embankment 20). .
Therefore, in designing the reinforced soil structure 10, since it is not necessary to consider the arc slip line starting from the top end reinforcing layer 30, the depth which is the reinforced region (the length of the reinforced material) of the reinforced soil structure 10 is eliminated. L ₂ a greatly reduced as compared with the conventional depth L _1, can be reduced construction costs only reinforced soil structure 10 meet shorter portion of the reinforcing region.

<4> Degree of freedom of method selection As described above, by forming the top end reinforcing layer 30 at the top end portion of the upper embankment 20, the construction cost of the reinforcing soil structure 10 is reduced by the shortening of the reinforcing region of the buttock. Can be reduced.
This does not depend on changing to an inexpensive construction method, but means that the construction cost is reduced with the same construction method.
Therefore, it is possible to select a construction method that considers the performance (safety, durability, etc.) most suitable for the site without placing the highest priority on the construction cost that has been an obstacle to the selection of the construction method.
In other words, there is a high possibility that a construction method that has previously been a bottleneck in construction costs will be adopted, and the degree of freedom in selecting a construction method will increase from the viewpoint of public structures. The most suitable method can be selected with priority.

<5> About design method of reinforced soil structure Conventionally, when high embankment exists in the upper part of a reinforced soil structure, much time and effort were required for the design of the reinforced soil structure.
On the other hand, in the composite embankment structure of the present invention, it is not necessary to assume an arc slip line starting from the top edge of the upper embankment 20, so that the design of the reinforced soil structure using the conventional simple design method can be shortened. Can be done easily and accurately in time.

<6> Seismic resistance of composite embankment structure The reinforced soil structure 10 greatly contributes to the stability of the slope and slope of the upper embankment 20.
In the case where the upper embankment 20 is a high embankment and there is one or a plurality of small steps 21, if the small step reinforcing material 24 is embedded horizontally at the position where the small steps 21 are formed, the starting point of the arc slip line S ₁ is set as the small step 21. It can be changed to the surface position from the back side.
As described above, by forming the top end reinforcing layer 30 at the top end portion of the upper embankment 20, the generation position of the arc slip lines S ₁ and S ₂ can be limited to the outer position of the top end reinforcing layer 30.
Accordingly, the collapse of the upper embankment 20 can be suppressed even if a small-scale earthquake occurs.
When a huge earthquake occurs, the upper embankment 20 is expected to collapse. However, the top edge reinforcement layer 30 is located at the top edge of the upper embankment 20, so that the top embankment 20 slides from the top edge. Is unlikely to occur, and secondary and tertiary slips are unlikely to occur.
Even if a part of the top shoulder portion of the top embankment 20 in contact with the lower surface of the top end reinforcing layer 30 collapses, the road surface 40 can be continuously supported by the bending strength of the top end reinforcing layer 30.
Since the upper embankment 20 and the top end reinforcement layer 30 can support the road surface 40 in cooperation, it is possible to pass emergency vehicles and the like, which can contribute to securing a road network in the event of an earthquake.

DESCRIPTION OF SYMBOLS 10 ... Reinforced earth structure 11 ... Embankment layer 12 of reinforced earth structure ... Reinforcement material 20 of reinforced earth structure ... Upper embankment (lifting embankment)
21 ... Upper embankment small step 22 ... Embankment material 23 ... Central embankment 24 of upper embankment ... Small step reinforcement 30 ... Top end reinforcement layer 31 ... Planar reinforcement 32 ..Bag 33 ... Soil pad 35 ... Restricted soil mat

Claims (8)

A reinforced soil structure in which a reinforcing material is embedded in the embankment, and a composite embankment structure in which an upper embankment is located above the reinforced soil structure,
The top embankment of the upper embankment has a top end reinforcing layer having a predetermined layer thickness in which the embankment material is held and restrained by a planar reinforcing material, and an arc slip line starting from the top end of the upper embankment is provided. Characterized by the loss
Composite embankment structure.   2. The composite embankment structure according to claim 1, wherein an elongation rate of the planar reinforcing material of the top end reinforcing layer is smaller than or equal to an elongation rate of the reinforcing material of the reinforced soil structure.   The composite embankment structure according to claim 1 or 2, wherein the top end reinforcing layer has a uniform thickness.   The composite embankment structure according to claim 1 or 2, wherein the top end reinforcing layer has a non-uniform thickness.   5. The composite embankment according to claim 3, wherein the top end reinforcing layer is constituted by a constrained soil mat formed by laminating an embankment material with a planar reinforcement material and laminating one or a plurality thereof. Structure.   The composite embankment structure according to any one of claims 1 to 5, wherein the reinforced earth structure located on the top of the upper embankment is a reinforced embankment or a reinforced earth wall.   The composite embankment structure according to any one of claims 1 to 6, wherein the upper embankment is a high embankment, and a reinforcing material for a small step is embedded at a small step position.   The top embankment is a road embankment, and has a top end reinforcing layer that is wrapped with a planar reinforcing material including a roadbed or a roadbed directly under a road surface. The composite embankment structure as described in the item.

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