Bottom reinforcement structure of open channel, and construction method for bottom reinforcement structure of open channel

Abstract

To improve the strength of the bottom ground in an open channel constructed by casting wall bodies and excavating the bottom portion, while enhancing workability and contributing to CO2 reduction.SOLUTION: A bottom reinforcement structure of an open channel is provided, the structure comprising: first and second wall bodies cast into the ground on both sides of the open channel; and logs cast into the bottom ground of the open channel between the first and second wall bodies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bottom reinforcement structure for an open channel and a construction method for the bottom reinforcement structure for an open channel. [Background technology]

[0002] In recent years, heavy rain disasters have become frequent, raising concerns about flooding caused by overflowing water and breaches or collapses of river levees due to scouring of the levee body. As a countermeasure against such disasters, for example, Patent Document 1 proposes a technology in which the bottom ground of an open channel such as a river is excavated and dug down, and the excavated soil is reused as embankment materials. With this technology, by digging down the bottom ground of the open channel, the maximum water retention capacity within the levee can be increased, and the occurrence of overflow during floods can be suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-9481 Summary of the Invention [Problem to be solved by the invention]

[0004] When excavating the bottom of an open channel, steel sheet pile walls or other structures are first cast on both sides to stabilize the channel, and then excavation is performed between the walls. In this case, the walls must be cast deep enough to withstand sufficient passive earth pressure from the bottom of the excavated channel, which tends to increase the casting depth and the amount of material required. Furthermore, in the case of rivers, for example, maintaining a constant gradient in the direction of the excavated bottom of the open channel is desirable for flood control purposes. However, erosion by water flow or earthquakes can change the shape of the bottom ground, resulting in an inconsistent gradient. For example, cement-based ground improvement methods can improve the strength of the bottom ground, but because these methods are difficult to perform underwater, they require drying, exposing the bottom ground to air by diverting water flow, and require large construction yards for cement plants and heavy construction equipment, making construction difficult. Furthermore, reducing CO2 emissions as a measure against global warming is also an important issue in the construction industry, and there is particularly great room for improvement in ground improvement methods, which emit large amounts of CO2 due to the fuel consumption of large heavy machinery.

[0005] Therefore, the present invention aims to provide a bottom reinforcement structure for an open channel, and a construction method for a bottom reinforcement structure for an open channel, which can improve workability and contribute to reducing CO2 emissions when improving the strength of the bottom ground in an open channel where construction has been done by pouring walls and digging down the bottom. [Means for solving the problem]

[0006] [1] A bottom reinforcement structure for an open channel comprising first and second walls driven into the ground on both sides of the open channel, and logs driven into the bottom ground of the open channel between the first and second walls. [2] A bottom reinforcement structure for an open channel described in [1], in which at least some of the logs are driven into recesses formed by the first or second wall body when arranged in a plan view. [3] The bottom reinforcement structure of an open channel described in [1], wherein at least one of the first and second walls or at least a portion of the logs is driven down to the supporting layer of the bottom ground. [4] A bottom reinforcement structure for an open channel described in [1], in which at least some of the logs are driven deeper than the passive collapse line of the bottom ground drawn from the lower end of the first wall toward the second wall. [5] The logs include, in relation to a first passive collapse line of the bottom ground drawn from the lower end of the first wall toward the second wall and a second passive collapse line of the bottom ground drawn from the lower end of the second wall toward the first wall, a first log that is driven deeper than the first passive collapse line between the first wall and the intersection of the first passive collapse line and the second passive collapse line, and a second log that is driven deeper than the second passive collapse line between the intersection and the second wall. [1] The bottom reinforcement structure of an open channel described in [1]. [6] The bottom reinforcement structure for an open channel described in [1], further comprising a cross member connecting the head of the first or second wall body to at least a portion of the log. [7] A bottom reinforcement structure for an open channel described in [1], in which the carbon storage amount of the logs per unit length in the extension direction of the open channel is equal to or greater than the carbon emission amount caused by heavy machinery when casting the first and second walls. [8] A construction method for a bottom reinforcement structure for an open channel described in any one of [1] to [7], comprising the steps of digging out the bottom of the open channel between the first and second wall bodies, and driving the logs into the bottom of the dug-out open channel. [9] A construction method for the bottom reinforcement structure of an open channel described in [8], in which the logs are cast underwater. [Effects of the Invention]

[0007] According to the above configuration, by driving logs into the ground at the bottom of the open channel, erosion caused by water flow can be suppressed. Furthermore, the resistance of the structure consisting of the bottom ground and the first and second walls to sliding and shearing is increased, which also helps to suppress changes in the shape of the bottom ground due to earthquakes and other events. Because the method using logs can be easily carried out underwater, it does not require the drying process required for ground improvement methods using cement, for example. It also reduces the construction space and shortens the construction period, making it highly workable. Furthermore, the carbon storage capacity of the logs, which are made of wood, can contribute to CO2 reduction. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view showing a bottom reinforcement structure for an open channel according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic plan view showing the bottom reinforcement structure of the open channel of FIG. 1. [Figure 3] FIG. 10 is a diagram showing an example of the relationship between the log driving depth and the passive collapse line of the bottom ground of an open channel in an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing an example of the relationship between the log driving depth and the passive collapse line of the bottom ground of an open channel in an embodiment of the present invention. [Figure 5] 10A and 10B are diagrams illustrating examples of further reinforcing structures in embodiments of the present invention. [Figure 6] 10A and 10B are diagrams illustrating examples of further reinforcing structures in embodiments of the present invention. [Figure 7] 10A and 10B are diagrams illustrating examples of further reinforcing structures in embodiments of the present invention. [Figure 8] FIG. 10 is a diagram for explaining the definition of an improvement rate. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0010] FIG. 1 is a schematic cross-sectional view showing an open channel bottom reinforcement structure according to one embodiment of the present invention, and FIG. 2 is a schematic plan view taken along line II-II in FIG. 1 , i.e., a schematic plan view showing the open channel bottom reinforcement structure. In this embodiment, the bottom reinforcement structure 10 includes steel sheet pile walls 11 and 12 driven into the ground on both sides of the open channel CL, and logs 13 driven into the bottom of the open channel CL between the steel sheet pile walls 11 and 12. The steel sheet pile walls 11 and 12 are examples of first and second walls, and in other embodiments, they may be concrete walls or the like. The logs 13 may be made by joining pieces of wood together with nails or adhesive.

[0011] The open channel bottom reinforcement structure 10 as described above is constructed, for example, by driving steel sheet pile walls 11, 12 on both sides of the open channel CL, excavating the bottom of the open channel CL between the steel sheet pile walls 11, 12, and driving logs 13 into the bottom of the excavated open channel CL. The logs 13 may be driven underwater while water is flowing through the open channel CL. The driving of the steel sheet pile walls 11, 12 and the excavation of the bottom may already have been completed, and only the driving of the logs 13 may be carried out as the construction of the open channel CL bottom reinforcement structure.

[0012] In the open channel bottom reinforcement structure 10 according to this embodiment, logs 13 are driven into the ground at the bottom of the open channel CL, thereby suppressing erosion caused by water flow. Furthermore, the resistance of the structure composed of the bottom ground and the steel sheet pile walls 11, 12 to sliding and shear is increased, thereby suppressing deformation of the bottom ground due to earthquakes and other events. More specifically, the bottom ground of the open channel CL is sandwiched between the steel sheet pile walls 11, 12, making ground movement toward the steel sheet pile walls 11, 12 easily restricted. By driving the logs 13 into the bottom ground and spreading the surrounding ground, the density of the ground between the logs 13 and the steel sheet pile walls 11, 12 is increased, thereby improving the strength of the bottom ground. Furthermore, the logs 13 increase the ground strength near the steel sheet pile walls 11, 12, thereby enhancing the ground resistance at the embedded portions of the steel sheet pile walls 11, 12. Furthermore, because the shear stiffness and shear resistance of the soil where the density has increased are increased, the overall stability of the structure can be improved, or the cross-sectional performance required for the steel sheet pile walls 11, 12, which are supported by the resistance of the soil, can be reduced. Thus, the present invention simplifies the structure by shortening the embedded length of walls such as the steel sheet pile walls 11, 12, or by using materials with lower stiffness, which means that the wall specifications can be set lower, leading to reduced costs for wall materials. From this perspective, the planar arrangement of the logs 13 does not necessarily need to be uniform; it is more effective to arrange the logs 13 more densely in areas close to the steel sheet pile walls 11, 12.

[0013] The above-mentioned effects make it possible to maintain a constant gradient at the bottom of the open channel CL. Similar effects can be achieved by ground improvement methods, but the method of this embodiment using logs can be carried out underwater, eliminating the need for drying up, which exposes the bottom of the open channel CL to the air, as required in ground improvement methods. It also reduces the construction space and shortens the construction period, making it highly workable. Another advantage of this embodiment is that logs and other log materials are easy to stockpile, making it easy to respond to urgent reinforcement work, such as disaster recovery work.

[0014] Furthermore, the logs 13 are driven into the bottom ground between the steel sheet pile walls 11, 12, which also has the effect of compacting the ground. This increases the passive earth pressure that the steel sheet pile walls 11, 12 receive at their embedded portions, allowing the steel sheet pile walls 11, 12 to be constructed using steel sheet piles with lower specifications, i.e., relatively smaller cross-sectional areas. This not only reduces costs but also carbon emissions during steel sheet pile manufacturing. As shown in Figure 2, by driving at least a portion of the logs 13 into the recesses formed by the steel sheet pile walls 11, 12 in their planar arrangement, the frictional force acting on the logs 13 as a reaction force to the compaction of the ground increases, improving resistance to the logs 13 being pulled out by, for example, water currents.

[0015] Furthermore, in this embodiment, the carbon offset effect can be achieved by utilizing the carbon storage capacity of the logs, which are made of wood. For example, the diameter and spacing of the logs 13 may be set so that the carbon storage capacity of the logs 13 per unit length in the extension direction of the open channel of the bottom reinforcement structure 10 is equal to or greater than the carbon emissions from the heavy machinery used to install the steel sheet pile walls 11, 12. It may also be possible to make the bottom reinforcement structure carbon-neutral, including the manufacturing process of the steel sheet piles used in the steel sheet pile walls 11, 12. Even if this is not possible, it is possible to significantly reduce carbon emissions throughout the entire embankment reinforcement construction project, including emissions during the manufacturing of wall materials and from heavy construction machinery.

[0016] The driving depth of the logs in this embodiment is not particularly limited, and the logs 13 may be driven shallower than the steel sheet pile walls 11, 12, as in the example of Fig. 1, for example, or may be driven deeper than the steel sheet pile walls 11, 12 in another example. Alternatively, logs 13 driven shallower than the steel sheet pile walls 11, 12 and logs 13 driven deeper than the steel sheet pile walls 11, 12 may be mixed. As an example of a guideline for driving depth, at least one of the steel sheet pile walls 11, 12 and at least a part of the logs 13 may be driven down to the bearing layer of the bottom ground of the open channel CL.

[0017] 3 and 4 are diagrams showing examples of the relationship between the log driving depth and the passive collapse line of the bottom ground of the open channel in an embodiment of the present invention. From the viewpoint of increasing the resistance to sliding and shear of the structure formed by the bottom ground of the open channel CL and the steel sheet pile walls 11 and 12 by driving the logs 13, at least a part of the logs 13 may be driven deeper than the passive collapse line PL of the bottom ground drawn from the lower end of the steel sheet pile wall 11 toward the steel sheet pile wall 12, as in the example of FIG. 4. Furthermore, at least a part of the logs 13 may be driven deeper than the passive collapse lines PL1 and PL2 of the bottom ground drawn from the lower ends of the steel sheet pile walls 11 and 12, respectively. 4 shows a passive collapse line PL1 drawn from the lower end of the steel sheet pile wall 11 toward the steel sheet pile wall 12, a passive collapse line PL2 drawn from the lower end of the steel sheet pile wall 12 toward the steel sheet pile wall 11, and an intersection CP of the passive collapse lines PL1 and PL2. The logs 13 include a first log 13A driven deeper than the passive collapse line PL1 between the steel sheet pile wall 11 and the intersection CP, and a second log 13B driven deeper than the passive collapse line PL2 between the intersection CP and the steel sheet pile wall 12. This can increase resistance to passive collapse in both directions due to, for example, earthquake forces.

[0018] 5 to 7 are diagrams illustrating further examples of reinforcement structures according to an embodiment of the present invention. In the example of FIG. 5, a cross member 14 is provided to connect the steel sheet pile wall 11 and the head of the log 13. The cross member 14 may be, for example, a wooden member similar to the log 13, or a steel or resin member. The steel sheet pile wall 11 and the cross member 14 may be connected by, for example, welding an angle iron 15 drilled into the steel sheet pile wall 11 and fastening the cross member 14 to the angle iron 15 with a wire, as in the example of FIG. 6, or by drilling holes directly in the steel sheet pile wall 11 and threading a wire through the hole, as in the example of FIG. 7. On the other hand, the cross member 14 and the log 13 are connected by, for example, drilling holes and threading a wire through the hole. The provision of the cross member 14 can prevent the log 13 from floating up or being washed away. A similar cross member may also be provided on the steel sheet pile wall 12 side. In addition, the cross member 14 may be spanned from the steel sheet pile wall 11 to the steel sheet pile wall 12.

[0019] Below, we will explain the results of verifying the carbon offset effect of constructing a bottom reinforcement structure for an open channel using logs. The improvement rate α S =πD 2 / 4B 2 Calculate the improvement rate α S The relationship between the distance between steel sheet pile walls and the amount of carbon stored was calculated. Table 1 shows the results of calculating the amount of carbon stored per 10m of open channel length when logs were driven at various driving intervals B into the bottom ground of a 30m wide open channel. The logs driven were larch logs with a length of 6m and a diameter of 0.2m (air-dry density 0.50g / cm). 3 ), and the carbon stock equivalent in CO2 was calculated by multiplying the log mass by the carbon content of lumber (0.5), and then multiplying it by 44 / 12 to convert the carbon mass to CO2 mass. In contrast, the CO2 emissions when driving two rows of steel sheet pile walls per 10m of open channel length are calculated by multiplying the amount of diesel fuel used by the injection machine and crawler crane (412.8L) by the diesel emission coefficient of 2.62kg-CO2 / L, resulting in 1.08t. Therefore, when using logs to construct a bottom reinforcement structure for an open channel, even with a relatively low improvement rate, it is possible to achieve a carbon stock amount greater than the carbon emissions from heavy machinery when driving steel sheet pile walls. On the other hand, when the steel sheet piles (13m long, total weight 32.76t) used for two rows of steel sheet pile walls per 10m of open channel length are manufactured using an electric furnace steelmaking process and rolling process (emission coefficient 1.507kg-CO2), the CO2 emissions are 1.08t. 2 / kg) is about 49.4t of CO2 emissions. S When the improvement rate α is high, it is possible to achieve a carbon storage amount greater than the carbon emissions during the manufacturing of the steel sheet pile and the installation of the steel sheet pile wall (in this example, 1.08 + 49.4 ≒ 50.0 t). S If this is further increased, it will be possible to achieve a carbon storage amount that exceeds the CO2 emissions of steel sheet pile walls manufactured in the steelmaking process using a blast furnace.

[0020] [Table 1] [Explanation of symbols]

[0021] CL...open channel, 10...bottom reinforcement structure, 11, 12...steel sheet pile wall, 13...logs, 14...cross members, 15...angle members.

Claims

1. first and second walls cast into the ground on either side of the open channel; A log driven into the bottom ground of the open channel between the first and second walls; A bottom reinforcement structure for an open channel comprising:

2. The bottom reinforcement structure for an open channel according to claim 1 , wherein at least some of the logs are driven into recesses formed by the first or second wall body when arranged in a plan view.

3. The bottom reinforcement structure for an open channel according to claim 1 , wherein at least one of the first and second walls and at least a portion of the logs is driven down to a bearing layer of the bottom ground.

4. The bottom reinforcement structure of an open channel described in claim 1, wherein at least some of the logs are driven deeper than a passive collapse line of the bottom ground drawn from the lower end of the first wall toward the second wall.

5. 2. The bottom reinforcement structure of claim 1, wherein the logs include, in relation to a first passive collapse line of the bottom ground drawn from the lower end of the first wall toward the second wall and a second passive collapse line of the bottom ground drawn from the lower end of the second wall toward the first wall, a first log that is driven deeper than the first passive collapse line between the first wall and the intersection of the first passive collapse line and the second passive collapse line, and a second log that is driven deeper than the second passive collapse line between the intersection and the second wall.

6. The bottom reinforcement structure for an open channel according to claim 1 , further comprising a cross member connecting a head portion of the first or second wall body to at least a portion of the log.

7. The bottom reinforcement structure of an open channel as described in claim 1, wherein the carbon storage amount of the logs per unit length in the extension direction of the open channel is equal to or greater than the carbon emission amount caused by heavy machinery when casting the first and second wall bodies.

8. A construction method for the bottom reinforcement structure of an open channel according to any one of claims 1 to 7, digging a bottom of the open channel between the first and second walls; a step of driving the logs into the bottom of the excavated open channel; A construction method for a bottom reinforcement structure of an open channel, including:

9. 9. The construction method for a bottom reinforcement structure of an open channel according to claim 8, wherein the logs are cast underwater.

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