JPH09279554A - Construction method for culvert - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce earth pressure to a top plate of a culvert by a gland arch formed in the upper banking ground of the culvert and maintain this earth pressure reducing effect for a long period of time. SOLUTION: An upper side pressure receiving plate 1 and a lower side pressure receiving plate 2 are laid in a laminated state on a top plate 11 of a culvert 10, and banking material is filled up thereon to construct the upper banking ground G of the culvert 10. The pressure receiving plates 1, 2 are smaller in yeild strength than additional load due to construction height up to the upper face of the upper banking ground G after construction, and the lower side pressure receiving plate 2 is larger in yeild strength than the upper side pressure receiving plate 1. Accordingly, even in case of a ground arch GA1 formed in the upper banking ground G collapses due to the yeild deformation of the upper side pressure receiving plate 1 relatively small in yeild strength, the lower side pressure receiving plate 2 relatively high in yield strength is yield-deformed so as to form a ground arch again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reducing earth pressure on a culvert under an embankment used for a waterway or a road.

[0002]

2. Description of the Related Art A culvert is a concrete sewer buried in an embankment such as a road or embankment for water, drainage, or a waterway. As shown in FIG. 12, this type of culvert (box culvert) 10 extends in a direction orthogonal to the illustrated cross section, is made of cast-in-place concrete or precast concrete, and is embedded in the embankment G. . When the overburden height of the embankment material on the culvert 10, that is, the formation height of the upper embankment G above the culvert 10 is large, the culvert 10 is used.
For the purpose of reducing the earth pressure acting on the top plate 11, the pressure receiving plate 20 having a required thickness made of a flexible material such as expanded polystyrene is laid on the top plate 11 and then the embankment material is piled up. I'm working.

According to the above-mentioned method, the embankment material is sequentially compacted and compacted every time it is piled up by a predetermined layer thickness, but the overlaid load by the upper embankment G of the culvert 10 causes the yield stress of the pressure receiving plate 20. When the pressure is exceeded, this pressure receiving plate 20
However, due to abrupt plastic deformation in the compression direction from the original state indicated by the alternate long and short dash line in the figure, a cavity is temporarily generated in the upper embankment G, and stress redistribution of the ground occurs,
As indicated by a broken line in the figure, a ground arch GA is formed of an underground discontinuous surface that is upwardly protruding and rises from both widthwise edges of the top plate 11. Therefore, the upper land plate G
The upper load due to the construction height of No. 1 will be supported by the sufficiently compacted ground region G ′ outside the grand arch GA, and the earth pressure acting on the top plate 11 of the culvert 10 will be effectively reduced. is there.

[0004]

According to the culvert embedding structure in the above conventional example, the earth pressure acting on the top plate 11 of the culvert 10 is effectively reduced as long as the soundness of the grand arch GA is maintained. However, it has been pointed out that such a Grand Arch GA has a problem in long-term stability. That is, due to, for example, occurrence of an earthquake, loosening due to increase in permeated water due to heavy rain, vibration transmitted from above the embankment, rolling load in the process of constructing the upper embankment G, etc., as shown in FIG. May collapse and the insulating property against the top load may be impaired. In such a case, the effect of reducing the earth pressure acting on the top plate 11 cannot be obtained.

The present invention has been made under the circumstances described above, and its technical problem is that earth pressure applied to the top plate of the culvert is caused by the ground arch formed in the upper embankment of the culvert. The purpose is to reduce the soil pressure, maintain this earth pressure reduction effect for a long time, and improve its reliability.

[0006]

In order to effectively solve the above-mentioned technical problems, according to the culvert embedding structure of the present invention, the top plate of this culvert and the upper embankment piled up thereon are In between, a plurality of pressure plates of a required thickness made of flexible materials with a yield strength smaller than the overburden load due to the overburden height of the culvert by the upper embankment and different in yield strength are interposed in a laminated state. It In this case, the flexible material is typically, for example, foamed plastic or the like, and when the load applied by the upper embankment piled up thereon is increased to a predetermined amount, the flexible material is rapidly yield-deformed in the compression direction. As a result, a ground arch is formed in the upper embankment.

According to the present invention, since a plurality of pressure receiving plates having a yield strength smaller than the overburden load due to the final burial height of the culvert and different yield strengths are laid in a laminated state, the upper embankment board When the loading load on the culvert increases due to the rise of, the pressure receiving plate having a relatively small yield strength among the plurality of pressure receiving plates is yield-deformed and the thickness thereof is rapidly reduced. A grand arch is formed in the upper embankment. After that, the upper embankment is further piled up to the required height, but the overburden that increases with it is insulated by the ground arch, so the earth pressure acting on the top plate of the culvert is effectively reduced. To be done.

In addition, when the ground arch once formed in the above-mentioned construction process collapses due to an increase in infiltration water due to the occurrence of an earthquake or heavy rain, transmission of vibrations from the embankment ground, rolling load in the embankment formation process, etc. The earth pressure reduction effect is lost, and the top loading by the upper embankment acting on the top plate of the culvert increases, but due to this top loading, the other yield strength is relatively higher than that of the pressure receiving plate that was yield-deformed previously. The undeformed pressure plate is yield-deformed and its thickness is rapidly reduced, thereby forming a ground arch again in the upper embankment. Therefore, the earth pressure reducing effect on the top plate of the culvert is maintained.

The yield strength difference between the pressure receiving plates can be given, for example, by forming standing holes in the pressure receiving plate at predetermined intervals. In this case, if the pressure receiving plate with the vertical hole is set to the uppermost side, the pressure receiving plate will not be yield-deformed by filling the vertical hole with earth and sand, and the function of forming the ground arch will be lost. It is necessary to stack so that it is on the uppermost side.

A similar effect is obtained in that, between the top plate of the culvert and the upper embankment piled up on it, the yield strength is smaller than the top load due to the overburden height of the culvert by this upper embankment, and the lower side. It can also be realized by interposing a single pressure receiving plate in which blind holes having a required depth are formed at predetermined intervals.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a process of constructing an embankment in a first embodiment of a culvert embedding structure according to the present invention. In FIG. 1, reference numeral 10 is a culvert which is a concrete pipe with a substantially rectangular or square cross section, 1 and 2 are pressure receiving plates laid in a laminated state on a top plate 11 of this culvert 10, and G is a culvert 10
Is an upper embankment ground piled up in a buried state, all extending in a direction orthogonal to the illustrated cross section.

The lower pressure-receiving plate 2 is made of expanded polystyrene whose yield strength is smaller than the loading load due to the final construction height from the upper surface of the upper pressure-receiving plate 1 to the upper surface of the upper embankment G. The lower pressure receiving plate 2 is made of expanded polystyrene having a yield strength smaller than that of the lower pressure receiving plate 2. Therefore, FIG.
As shown in the stress-strain diagram of Fig. 2, when both pressure receiving plates 1 and 2 are pressed in the thickness direction, the compressive strain of the pressure receiving plates 1 and 2 is small while the resulting compressive stress σ is small. In Although,
When the compressive stress σ exceeds σ ₁ , first the upper pressure receiving plate 1
Yields, and the amount of compressive strain increases rapidly. Also,
When the compressive stress σ further increases and exceeds σ ₂ , the lower pressure receiving plate 2 is yield-deformed this time, and the amount of compressive strain increases sharply.

Therefore, in this embodiment, first, a precast concrete product, which has been molded into the cross-sectional shape shown in the figure in advance by casting the concrete at a predetermined position, is placed in the longitudinal direction (the cross-section shown in the figure). The culvert 10 is constructed by connecting in the orthogonal direction). After the construction of this culvert 10, the embankment material is sprinkled out on both sides of the culvert 10 and compacted by a compactor to form a embankment. Before the top plate 11 of the culvert 10 is covered with the embankment material, this top plate is covered. The pressure receiving plates 1 and 2 are laid on the surface 11 in advance so as to overlap each other.

After the pressure receiving plates 1 and 2 have been laid, the embankment material is also sprinkled on the pressure receiving plates 1 and 2 and the pressure is applied to the upper embankment ground G.
I will build up and build. Then, in the process of constructing the upper embankment G, the top load acting on both the pressure receiving plates 1 and 2 increases with the increase of the overburden height h on the upper pressure receiving plate 1, but eventually the compressive stress due to this top loading is increased. When σ exceeds the yield stress σ ₁ of the upper pressure receiving plate 1, as shown in FIG.
Since the thickness of the upper pressure receiving plate 1 is rapidly reduced by the yield deformation, as described in the above-mentioned conventional technique, a cavity is temporarily generated in the upper embankment G on the top plate 11 of the culvert 10 to cause the formation of the ground. Due to the stress redistribution,
A ground arch GA ₁ is formed of an underground discontinuous surface protruding upward from both widthwise edges of the top plate 11 and protruding upward.

Therefore, even if the upper mounting load is increased by raising the upper embankment G further higher thereafter, the upper mounting load is supported by the ground region G ₁ outside the ground arch GA ₁ , and the ground arch G ₁ is supported. Since the load on the ground area G ₂ inside GA ₁ is effectively insulated,
Earth pressure acting on the top plate 11 of the culvert 10 is reduced. Further, the lower pressure receiving plate 2 has a higher yield strength than the upper pressure receiving plate 1, and since the compressive load is reduced by the grand arch GA ₁ , the amount of compressive strain is small at this point and the original shape is maintained. ing.

The ground arch GA ₁ formed in the upper embankment G as described above has the following occurrence of earthquake, increase in seepage water due to heavy rainfall, various vibrations propagated in the upper embankment G, It may collapse due to a compaction load in the process of constructing the upper embankment G. In such a case, since the ground discontinuity due to the grand arch GA ₁ is eliminated, as shown in FIG. 4, the top plate 1 of the culvert 10 is removed.
A large loading load F due to the earth cover height above acts on 1 through the upper pressure receiving plate 1 and the lower pressure receiving plate 2. This upper loading F is the undeformed lower pressure receiving force. Board 2
Since it is larger than the yield stress σ _{2 of} the lower pressure-receiving plate 2, the lower pressure-receiving plate 2 is yield-deformed by the upper loading F and the thickness thereof is rapidly reduced. Therefore, as shown in FIG. 5, the ground arch GA ₂ is formed again in the upper embankment G, and the earth pressure acting on the top plate 11 is reduced.

FIG. 6 shows a process of embankment construction in a second embodiment of the culvert burying structure according to the present invention. In this embodiment, the upper pressure-receiving plate 1 is made of expanded polystyrene whose yield strength is smaller than the loading load due to the final construction height from the upper surface to the upper surface of the upper embankment G, and the lower pressure-receiving plate 2 is the upper side. As shown in FIG. 7, which is a cross-sectional view taken along line VII-VII ′ of FIG. 6, in the polystyrene foam of the same material as the pressure receiving plate 1, as shown in FIG. 2a was established. Therefore, contrary to the above-described first embodiment, the yield strength of the lower pressure receiving plate 2 is smaller than that of the upper pressure receiving plate 1.

In this embodiment, as in the first embodiment, after construction of the culvert 10, the embankment material is sprinkled out on both sides of the culvert 10 and compacted by a compacting machine to form the embankment. In the process, the culvert 10 is formed. The pressure plates 1 and 2 are laid on top of each other on the top plate 11, and the upper embankment ground G is piled up. Then, in the process of forming the upper embankment G, as the earth cover height h on the upper pressure receiving plate 1 increases, the upper loading acting on both pressure receiving plates 1 and 2 increases, so that the compressive stress due to this upper loading eventually comes. σ exceeds the yield stress of the lower pressure-receiving plate 2, and as shown in FIG. 8, the lower pressure-receiving plate 2 yield-deforms and its thickness rapidly decreases, so that the upper platen G on the top plate 11 is The ground arch GA ₁ is formed by a temporary cavity and a redistribution of the ground stress. For this reason, even if the above-mentioned load is increased by raising the upper embankment G further higher thereafter, the earth pressure acting on the top plate 11 of the culvert 10 is reduced by the grand arch GA ₁ . Also,
At this point, the upper pressure-receiving plate 1 having a yield strength higher than that of the lower pressure-receiving plate 2 is maintained in a substantially original state.

In addition, the ground arch GA ₁ formed in the upper embankment G as described above is transmitted to the upper embankment G due to the occurrence of subsequent earthquakes, the increase of seepage water due to heavy rain, and various types of propagation. If the ground arch GA ₁ collapses due to vibration, rolling load, etc. during the process of constructing the upper ground G
However, the upper pressure receiving plate 1 is yield-deformed by a large top load due to the height of the earth covering above the upper pressure receiving plate 1 and the thickness thereof is rapidly reduced. Therefore, similarly to FIG. 5 described above, the ground arch GA ₂ is formed again in the upper embankment G, and the earth pressure acting on the top plate 11 is reduced.

In this embodiment, the pressure receiving plate 1 having no standing hole is set to the upper side and the pressure receiving plate 2 having the standing hole 2a is set to the lower side. This is because when the plate is placed on the upper side, the vertical holes are filled with the intrusion of earth and sand, and even if the overload is increased, the yield deformation of the upper pressure-receiving plate and the formation of the ground arch are not performed, and the effect of the present invention cannot be realized. .

In the first and second embodiments, two pressure receiving plates having different yield strengths are laminated, but if a triple or more laminated structure having different yield strengths is used, the number of times the grand arch can be regenerated is increased. The safety of the culvert 10 can be further enhanced. FIG. 9 shows a process of constructing an embankment ground in a third embodiment of the culvert embedding structure according to the present invention. In this embodiment, the pressure receiving plate has a triple laminated structure.

That is, in this embodiment, the three pressure receiving plates 1 to 3 are laid in a laminated state on the top plate 11 of the culvert 10. Of these, the upper pressure-receiving plate 1 is made of expanded polystyrene whose yield strength is smaller than the load applied by the final building height from the upper surface to the upper surface of the upper embankment G, and the lower pressure-receiving plate 2 is the upper pressure-receiving plate 1 and the upper pressure-receiving plate 1. Similar to FIG. 7 described above, a large number of vertical holes 2 arranged on the styrofoam of the same material so as to be located at the diamond-shaped regular triangular lattice points.
a is opened, and the intermediate pressure receiving plate 3 is a rectangular cross-section as shown in FIG. 10, which is a cross-sectional view taken along the line XX ′ of FIG. 9 in the styrofoam of the same material as the upper pressure receiving plate 1. A large number of standing holes 3a arranged so as to be located at the square lattice points of are opened.

Here, the interval p between the diamond-shaped lattice points at which the vertical holes 2a are opened in the lower pressure receiving plate 2 and the intermediate pressure receiving plate 3 are formed.
The intervals p between the grid-like lattice points at which the vertical holes 3a are opened are 100 mm, the diameter φ ₁ of the vertical holes 2a is 70 mm,
If the diameter φ ₂ of the upright holes 3a is 50 mm, and the plane shapes of the lower pressure receiving plate 2 and the intermediate pressure receiving plate 3 are 600 mm × 600 mm squares, the lower pressure receiving plate 2 has the number of upright holes 2a as shown in FIG. 39 pieces,
While the opening area is 150085 mm ² and the opening ratio is 0.41%, the intermediate pressure receiving plate 3 has 36 vertical holes 3a as shown in FIG.
The opening area is 70683 mm ² , and the opening ratio is 0.19%. Therefore, the intermediate pressure receiving plate 3 has a higher yield strength than the lower pressure receiving plate 2 and a lower yield strength than the upper pressure receiving plate 1. Further, by using the pressure receiving plate 1 having no vertical holes as the uppermost layer, the intrusion of earth and sand into the vertical holes 2a, 3a of the pressure receiving plates 2, 3 having a low yield strength can be prevented as in the second embodiment. To prevent.

Therefore, according to this embodiment, in the process of laying the pressure receiving plates 1 to 3 on the top plate 11 of the culvert 10 and superimposing the upper embankment G on the top plate 11, the pressure receiving plates 1 to 3 are formed. Due to the increase in the top load of the upper embankment G acting on, the lower pressure receiving plate 2 is first yield-deformed and the ground arch GA ₁ is formed as in FIG.
Earth pressure acting on the top plate 11 of the culvert 10 is reduced. At this point, the upper pressure-receiving plate 1 and the intermediate pressure-receiving plate 3 having a yield strength higher than that of the lower pressure-receiving plate 2 are maintained in the substantially original state.

Further, the ground arch GA _{1 is} caused by the occurrence of an earthquake thereafter, the increase of seepage water due to heavy rain, various vibrations propagated in the upper embankment G, and the compaction load in the process of constructing the upper embankment G. In case of collapse, the intermediate pressure receiving plate 3 is yield-deformed and the thickness thereof is rapidly reduced due to the top loading of the upper embankment G, which causes the ground arch to be formed again in the upper embankment G. Earth pressure acting on the top plate 11 of the culvert 10 is reduced. At this point, the upper pressure-receiving plate 1 having a yield strength higher than that of the intermediate pressure-receiving plate 3 is maintained in a substantially original state. Therefore, even if the ground arch collapses afterwards due to the earthquake or the like, the ground arch is formed again in the upper embankment G by the yield deformation of the upper pressure receiving plate 1.

In each of the second and third embodiments, the pressure receiving plate whose yield strength is lowered by forming the vertical holes is laminated on the lower side, and the pressure receiving plate not having the vertical holes is laminated on the upper side. However, even if a single pressure receiving plate having an integrated shape is used, the same effect as described above can be realized. FIG. 11 is a diagram showing a process of building a land surface in a fourth embodiment of the culvert buried structure according to the present invention,
The single pressure receiving plate as described above is used.

That is, in this embodiment, one pressure receiving plate 4 is laid on the top plate 11 of the culvert 10. Similar to each of the above-described embodiments, the pressure receiving plate 4 is made of expanded polystyrene whose yield strength is smaller than the load applied by the final building height from the upper surface to the upper surface of the upper embankment G. A large number of blind holes 4a are formed in a lower half portion 4'up to a substantially central portion in the vertical direction so as to be located at a lattice point of a rhombic shape or a grid shape. The upper half portion 4 ″ where the blind hole 4a does not exist is, for example, a region corresponding to the upper pressure receiving plate 1 in the second embodiment.
The lower half portion 4'forming a is an area corresponding to the lower pressure receiving plate 2 in the second embodiment, that is, the pressure receiving plate 4
Has a thickness corresponding to the sum of the thickness of the upper pressure receiving plate 1 and the thickness of the lower pressure receiving plate 2.

Therefore, according to this embodiment, since the lower half portion 4'of the pressure receiving plate 4 has a lower yield strength than the upper half portion 4 "due to the presence of a large number of blind holes 4a, the lower half portion 4'on the top plate 11 of the culvert 10 is reduced. In the process of laying the pressure receiving plate 4 on the upper surface and then building up and forming the upper embankment G, the lower half portion 4'of the pressure receiving plate 4 is first yield-deformed and ground arch GA ₁ as in FIG. Is formed, and the earth pressure acting on the top plate 11 of the culvert 10 is reduced, and the occurrence of subsequent earthquakes, the increase of infiltration water due to heavy rain, various vibrations propagated in the upper embankment G, and the upper embankment. When the ground arch GA ₁ collapses due to a compaction load or the like in the process of forming the ground G, the upper loading 4 G where the blind hole 4 a does not exist is yield-deformed by the top loading of the upper ground G that acts by this. Suddenly Of reduced thickness, again ground arch in the upper fill soil G is formed, Calvert 10
The earth pressure acting on the top plate 11 of the is reduced.

The present invention is not limited to the illustrated embodiment. For example, as the pressure receiving plate, any flexible material having required yield strength and compressibility may be used, and foamed plastic other than polystyrene foam may be adopted. Further, in the fourth embodiment, a plurality of types of blind holes 4a having different depths are formed in the pressure receiving plate 4 at appropriate intervals, so that a yield deformation function of three steps or more can be provided as in the third embodiment. it can.

[0030]

According to the embedded structure of the culvert according to the present invention, among the plurality of pressure receiving plates laid in a laminated state on the top plate of the culvert, the yield deformation of the pressure receiving plate having a relatively low yield strength causes Even if the ground arch formed on the upper ground collapses due to rainfall, vibration, etc., another pressure receiving plate with a higher yield strength than the pressure receiving plate is yielded and deformed to form a new ground arch. The effect of reducing the earth pressure on the culvert top plate by the arch can be maintained for a long time. For this reason, the reliability of the effect of reducing the earth pressure is improved, the thickness of the culvert can be reduced, and the burying of the culvert is facilitated and the construction cost is expected to be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of constructing an embankment ground in a first embodiment of a culvert embedding structure according to the present invention.

FIG. 2 is a stress-strain diagram showing the yield strength of the upper pressure receiving plate and the lower pressure receiving plate in the first embodiment.

FIG. 3 is a sectional view showing a state in which a ground arch is formed by plastic deformation of an upper pressure receiving plate in the first embodiment.

FIG. 4 is a cross-sectional view showing a collapsed state of the grand arch in the first embodiment.

FIG. 5 is a cross-sectional view showing a state in which a ground arch is formed by plastic deformation of the lower pressure receiving plate in the first embodiment.

FIG. 6 is a cross-sectional view showing a process of constructing an embankment ground in a second embodiment of the culvert embedding structure according to the present invention.

FIG. 7 is a cross-sectional view of the lower pressure receiving plate taken along line VII-VII ′ in FIG.

FIG. 8 is a cross-sectional view showing a state in which a ground arch is formed by plastic deformation of a lower pressure receiving plate in the second embodiment.

FIG. 9 is a cross-sectional view showing a process of constructing an embankment ground in a third embodiment of the culvert embedding structure according to the present invention.

10 is a cross-sectional view of the intermediate pressure receiving plate taken along line XX 'in FIG.

FIG. 11 is a cross-sectional view showing a process of creating a bank in a fourth embodiment of the culvert embedding structure according to the present invention.

FIG. 12 is a cross-sectional view showing a state in which a ground arch is formed by plastic deformation of a pressure receiving plate in a culvert embedded structure according to a conventional technique.

FIG. 13 is a cross-sectional view showing a collapsed state of the ground arch in the above-mentioned conventional technique.

[Explanation of symbols]

1 Upper pressure receiving plate 2 Lower pressure receiving plate 3 Intermediate pressure receiving plate 4 Pressure receiving plate 2a, 3a Vertical hole 4a Blind hole 10 Culvert 11 Top plate G Filled plate GA ₁ , GA ₂ Grand arch

Claims (3)

[Claims] 1. A culvert is embedded in an embankment, and between the top plate of this culvert and the upper embankment built up on the culvert, the load applied due to the overburden height of the culvert by the upper embankment is higher than that. An embedded structure of a culvert, characterized in that a plurality of pressure plates of a required thickness made of flexible materials having a small yield strength and different yield strengths are interposed in a laminated state. 2. The pressure-difference plate according to claim 1, wherein the yield strength difference between the pressure-receiving plates is set by forming standing holes at predetermined intervals in the pressure-receiving plate, and the pressure-receiving plate having no standing hole is the uppermost one. The buried structure of the culvert, which is characterized by being overlapped so that 3. A culvert is buried in the embankment, and between the top plate of this culvert and the upper embankment built up on the culvert, the load applied by the overburden height of the culvert by the upper embankment is higher than that. An embedded structure of a culvert characterized by having a low yield strength and having a pressure receiving plate having blind holes of a required depth formed at predetermined intervals on the lower side.