Method for designing permeable erosion control dam

Abstract

To provide a method for designing a permeable erosion control dam capable of appropriately setting a cushioning member of a permeable erosion control dam having a dam body and the cushioning member mounted on the dam body.SOLUTION: A method for designing a permeable erosion control dam having a dam body composed of a body steel pipe and a cushioning member mounted on the dam body includes: a body steel pipe setting step of setting an outer diameter D of the body steel pipe, setting a plate thickness t1 of the body steel pipe, on the basis of a static load acting on the dam body, and setting plate thickness t2 of the body steel pipe, on the basis of collision energy E of debris acting on the dam body; and a cushioning steel pipe setting step of setting outer diameter D' and plate thickness t' of the cushioning steel pipe constituting the cushioning member, on the basis of Expressions (1) to (3).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for designing a permeable sabo dam which includes a dam body and a buffer member attached to the dam body. [Background technology]

[0002] As technologies relating to permeable sabo dams that prevent disasters caused by sediment and driftwood, the technologies disclosed in Patent Documents 1 to 3 in which a buffer member is attached to the dam body are disclosed.

[0003] The open-type sand-control dam in Patent Document 1 is characterized in that a buffer means with a closed cross-section for absorbing the collision energy of boulders during floods is attached to the upstream face of the dam body so as to be freely attached and detached from the dam body, and the buffer means is provided with deformation restraint means for restraining deformation of the buffer means due to the collision of boulders, and the deformation restraint means is provided on both ends of the buffer means.

[0004] The open-type sand-control dam of Patent Document 2 is characterized in that a buffer means for absorbing the collision energy of boulders during floods is attached to the upstream face of the dam body via brackets so that it can be freely attached and detached to the dam body, and the dam body consists of steel pillars fixed to the foundation concrete or ground and steel beams fixed between the pillars, the pillars and the beams are connected to each other via polyhedral steel box-type connecting elements, and the axes of the pillars and the beams are concentrated at one point within the steel box-type connecting elements.

[0005] The open-type sand-control dam in Patent Document 3 is characterized in that a buffer means for absorbing the collision energy of boulders during floods is attached to the upstream face of the dam body via a bracket so that it can be freely attached and detached to the dam body, the bracket is attached facing the downstream face of the buffer means and is not exposed on the upstream face, and the buffer means is divided into several pieces vertically. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3270744 [Patent Document 2] Patent No. 3289827 [Patent Document 3] Patent No. 3946028 Summary of the Invention [Problem to be solved by the invention]

[0007] In the techniques disclosed in Patent Documents 1 to 3, a buffer material is placed upstream of the dam body to buffer the impact of gravel. However, a method for designing the outer diameter and plate thickness of the buffer steel pipe that constitutes the buffer material has not yet been established. This means that an appropriate buffer material may not be selected, and the dam body may be damaged by the impact of gravel. Therefore, a design method for a permeable sabo dam that allows appropriate selection of the buffer steel pipe is required.

[0008] Therefore, the present invention has been devised in consideration of the above-mentioned circumstances, and its object is to provide a design method for a permeable sabo dam that can appropriately select the cushioning member of a permeable sabo dam that comprises a dam body and a cushioning member attached to the dam body. [Means for solving the problem]

[0009] The design method for a permeable sabo dam according to the present invention is a method for designing a permeable sabo dam comprising a dam body composed of a main steel pipe and a buffer member attached to the dam body, and is characterized in comprising a main steel pipe setting process for setting the outer diameter D of the main steel pipe, setting the plate thickness t1 of the main steel pipe based on the static load acting on the dam body, and setting the plate thickness t2 of the main steel pipe based on the collision energy E of gravel acting on the dam body, and a buffer steel pipe setting process for setting the outer diameter D' and plate thickness t' of the buffer steel pipe constituting the buffer member based on the following mathematical formulas (1) to (3).

[0010]

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[0011]

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[0012]

number

[0013] According to the present invention, a method for designing a permeable sabo dam can be provided that enables appropriate selection of the buffer member of a permeable sabo dam comprising a dam body and a buffer member attached to the dam body. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of a permeable sabo dam according to an embodiment. [Diagram 2] FIG. 2 is a side view showing an example of a permeable sabo dam in an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of an example of a permeable-type sabo dam in an embodiment, taken along a cross section perpendicular to the axial direction of the first main steel pipe in the vicinity of the first main steel pipe. [Figure 4] FIG. 4 is a flowchart showing a method for designing a permeable sabo dam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a detailed description will be given of an embodiment of a design method for a permeable sabo dam to which the present invention is applied with reference to the drawings. In each drawing, the vertical direction is Z, the direction in which the downstream material flows is called the downstream direction X, and the direction intersecting the vertical direction Z and the downstream direction X is called the width direction Y. The downstream direction X has an upstream side X1 and a downstream side X2.

[0016] (First embodiment) Fig. 1 is a perspective view showing an example of a permeable sabo dam 100 according to the first embodiment. Fig. 2 is a side view showing an example of the permeable sabo dam 100 according to the first embodiment.

[0017] The permeable sabo dam 100 captures washed-out debris such as gravel, earth and sand. The permeable sabo dam 100 comprises a dam main body 8 and a buffer member 1 detachably attached to at least one of the upstream side X1 and the upper side of the dam main body 8. In the example of Fig. 1, the buffer member 1 is detachably attached to the upstream side X1 of the dam main body 8.

[0018] The buffer member 1 absorbs the collision energy when a huge boulder or the like collides with it, and reduces the collision energy transmitted to the dam body 8. Because the buffer member 1 is detachably attached to the dam body 8, even if the buffer member 1 is damaged by a collision with boulders, the damaged buffer member 1 can be easily replaced with a new buffer member 1.

[0019] (Dam body 8) The dam body 8 is erected on a foundation 9 such as a concrete foundation or ground. The dam body 8 has a plurality of main steel pipes 80, and is formed by combining a plurality of main steel pipes 80. The main steel pipes 80 include a first main steel pipe 81, a second main steel pipe 82, and a third main steel pipe 83.

[0020] The first main steel pipe 81 extends in the up-down direction Z, for example, in the vertical direction. The first main steel pipe 81 is arranged at the most upstream side of the dam body 8, and its lower end is buried and fixed in the foundation 9. Multiple first main steel pipes 81 are arranged spaced apart in the width direction Y. The first main steel pipe 81 may be provided with multiple cross members 89 extending in the width direction Y in the up-down direction Z. By having the first main steel pipe 81 have the cross members 89, it is possible to further prevent captured gravel, etc. from flowing downstream of the dam body 8. The cross members 89 are, for example, made of a steel pipe.

[0021] The second main body steel pipe 82 is arranged downstream X2 of the first main body steel pipe 81 in the flow direction X. The second main body steel pipe 82 is arranged along the flow direction X. The second main body steel pipe 82 is a diagonal member that slopes downward toward the downstream side X2. The upper end of the second main body steel pipe 82 is connected to the first main body steel pipe 81 by welding or the like, and the lower end is buried and fixed in the foundation portion 9. Multiple second main body steel pipes 82 are arranged spaced apart in the width direction Y.

[0022] The third main body steel pipe 83 extends in the width direction Y. The third main body steel pipe 83 connects the multiple first main body steel pipes 81 that are spaced apart in the width direction Y. The third main body steel pipe 83 is connected to the first main body steel pipe 81 by welding or the like.

[0023] (Buffer material 1) The buffer member 1 includes a buffer steel pipe 10 and an attachment mechanism 2 .

[0024] FIG. 3 is a cross-sectional view of an example of the permeable sabo dam 100 according to the first embodiment, taken along a cross section perpendicular to the pipe axis direction of the first steel main pipe 81 near the first steel main pipe 81. As shown in FIG. 3, the mounting mechanism 2 detachably mounts the buffer steel pipe 10 to the steel main pipe 80. The mounting mechanism 2 has, for example, a first mounting steel pipe 21 fixed to the steel main pipe 80 and a second mounting steel pipe 22 fixed to the buffer steel pipe 10. The first mounting steel pipe 21 and the second mounting steel pipe 22 have flanges formed at their ends. The first mounting steel pipe 21 and the second mounting steel pipe 22 are joined by contacting their flanges with each other and using fastening hardware 23 such as bolts and nuts. Alternatively, the mounting mechanism 2 may be, for example, a U-bolt.

[0025] The buffer steel pipe 10 is arranged along the main steel pipe 80. The buffer steel pipe 10 is preferably hollow, for example. This can further improve the energy absorption of the buffer steel pipe 10 and further reduce the support reaction force transmitted to the main steel pipe 80.

[0026] The longitudinal length of the buffer steel pipe 10 is preferably, for example, at most about 4.0 m to 6.0 m. This improves the transportability of the buffer steel pipe 10 by vehicle and improves the construction efficiency of the permeable sabo dam 100. The longitudinal length of the buffer steel pipe 10 is, for example, at most about 1.0 m.

[0027] The buffer steel pipe 10 has a first buffer steel pipe 11. The first buffer steel pipe 11 is arranged on the upstream side X1 of the first main steel pipe 81. The lower end of the first buffer steel pipe 11 is separated from the foundation portion 9. For example, two attachment mechanisms 2 are provided on one first buffer steel pipe 11. The outer diameter D' of the first buffer steel pipe 11 is equal to or greater than the outer diameter D of the first main steel pipe 81. The plate thickness t' of the first buffer steel pipe 11 is less than the plate thickness t of the first main steel pipe 81. The lower end of the buffer steel pipe 10 may be separated from the foundation portion 9, or the lower end may be buried in the foundation portion 9.

[0028] In the permeable sabo dam 100, the plate thickness t' of the first buffer steel pipe 11 is less than the plate thickness t of the first main body steel pipe 81. This allows the first buffer steel pipe 11 to undergo dent deformation before the first main body steel pipe 81, reducing the collision energy of the debris flow acting on the dam main body 8. In other words, it is possible to improve the buffering effect, which obtains large absorption energy with a small load. As a result, damage to the dam main body 8 can be suppressed.

[0029] In the permeable-type sabo dam 100, the outer diameter D' of the first buffer steel pipe 11 is, for example, equal to or greater than the outer diameter D of the first main body steel pipe 81. This makes it possible to make the net distance L11 between the outer surfaces of the two first buffer steel pipes 11 equal to or less than the net distance L81 between the outer surfaces of the two first main body steel pipes 81. Therefore, when gravel or the like flows downstream, the gravel or the like can be easily captured by the first buffer steel pipe 11, and collision of the gravel or the like with the first main body steel pipe 81 can be suppressed. As a result, damage to the dam body 8 can be suppressed.

[0030] In the permeable sabo dam 100, the outer diameter D' of the buffer steel pipe 10 is larger than, for example, the outer diameter D of the main steel pipe 80. This makes it possible to increase the absorbed energy of the buffer steel pipe 10 while reducing the fulcrum reaction force transmitted to the main steel pipe 80, compared to when the outer diameter D' of the buffer steel pipe 10 is the same as the outer diameter D of the main steel pipe 80. This makes it possible to further improve the buffering effect, which obtains large absorbed energy with a small load. As a result, damage to the dam main body 8 can be suppressed.

[0031] <Design method for open-type sabo dams> Next, a method for designing a permeable sabo dam will be described. The method for designing a permeable sabo dam involves designing a permeable sabo dam 100 that includes a dam body 8 and a buffer member 1 that is attached to the dam body 8. As shown in Fig. 4, the method for designing a permeable sabo dam includes a main body steel pipe setting process S11 and a buffer steel pipe setting process S12.

[0032] <Main steel pipe setting process S11> In the main steel pipe setting process S11, the outer diameter D and plate thickness t of the main steel pipe 80 constituting the dam body 8 are set. The main steel pipe setting process S11 includes a static load confirmation process S111, a gravel collision confirmation process S112, and a manufacturing feasibility determination process S113. The plate thickness t includes a plate thickness t1 that is set based on the static load, and a plate thickness t2 that is set based on the gravel collision energy E.

[0033] <Static load confirmation process S111> The static load confirmation process S111 sets the plate thickness t1 of the main steel pipe 80 based on the static load acting on the dam main body 8. The static load confirmation process S111 confirms the safety of the dam main body 8 against the static load based on, for example, pp. 110-114 of the "New Steel Erosion Control Structure Design Handbook" (Reiwa 3rd Edition, Erosion Control and Landslide Technology Center, General Incorporated Foundation), and sets the plate thickness t1 of the main steel pipe 80 that can resist the static load acting on the dam main body 8. In addition, the static load confirmation process S111 may confirm the safety of the dam main body 8 against the static load and set the plate thickness t1 using a well-known method.

[0034] In the static load confirmation step S111, for example as shown in the following Table 1, the outer diameter D and plate thickness t1 of the main steel pipe 80 constituting the dam body 8 are set as the outer diameter D and plate thickness t1 of the main steel pipe 80 on the most upstream side, and the outer diameter D and plate thickness t1 of the other main steel pipes 80. In addition, the height of the dam body 8, which is the acting height of the static load, is also set.

[0035] [Table 1]

[0036] In addition, the static load confirmation step S111 sets the fluid force of the debris flow, the water depth of the debris flow, the flow velocity of the debris flow, the unit volume weight of the debris flow, and the unit volume weight of the deposited soil. In the static load confirmation step S111, the fluid force of the debris flow, the water depth of the debris flow, the flow velocity of the debris flow, the unit volume weight of the debris flow, and the unit volume weight of the deposited soil are set, for example, as shown in Table 2 below.

[0037] [Table 2]

[0038] Then, in the static load confirmation process S111, the stress generated in the main steel pipe 80 and the allowable stress are calculated based on the structural calculation method described in the above-mentioned "New Edition Steel Erosion Control Structure Design Handbook," for example. In the static load confirmation process S111, if the stress generated in the main steel pipe 80 is within the allowable stress, it can be confirmed that the dam main body 8 is safe against the static load. In the static load confirmation process S111, if the stress generated in the main steel pipe 80 exceeds the allowable stress, it can be confirmed that the dam main body 8 is not safe against the static load.

[0039] In the static load confirmation process S111, the safety of the dam body 8 is confirmed based on the above-mentioned "New Steel Sand Control Structure Design Handbook." For example, as shown in Table 3 below, if the generated stress level is below the allowable stress level in each of the cases of a debris flow, when the structure is full of sand, and when the temperature changes, then the dam body 8 is deemed safe against static load, and the next gravel collision confirmation process S112 is carried out.

[0040] [Table 3]

[0041] If the result of the static load confirmation step S111 is not safe, the outer diameter D and plate thickness t1 of the main steel pipe 80 are newly set and the static load confirmation step S111 is performed again. If the result of the static load confirmation step S111 is safe, the outer diameter D and plate thickness t1 are set and the next gravel collision confirmation step S112 is performed.

[0042] In the calculation examples of Tables 1 to 3, the outer diameter D can be set to 600 mm and the plate thickness t1 can be set to 22 mm based on the static load acting on the dam body 8.

[0043] <Pebble collision confirmation process S112> In the gravel collision confirmation process S112, the plate thickness t2 of the main steel pipe 80 is set based on the collision energy E of the gravel acting on the dam main body 8. When large gravel flows down from the upstream side of the permeable sabo dam 100, the gravel will collide with the upstreammost side of the permeable sabo dam 100. For this reason, in the gravel collision confirmation process S112, the plate thickness t2 of the main steel pipe 80 located at the upstreammost part of the dam main body 8 is set based on the collision energy E of the gravel acting on the main steel pipe 80 located at the upstreammost part of the dam main body 8.

[0044] In the gravel collision confirmation process S112, the plate thickness t2 of the main steel pipe 80 is set based on the following formula (4). d is equal to or greater than the collision energy E of the gravel, it can be confirmed that the main steel pipe 80 on the most upstream side of the dam body 8 is safe against collision of gravel. d is less than the collision energy E of the gravel, it can be confirmed that the main steel pipe 80 on the most upstream side of the dam body 8 is not safe against collision with gravel. In the gravel collision confirmation step S112, the outer diameter D of the main steel pipe 80 is the one set in the static load confirmation step S111.

[0045]

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[0046] Here, the absorbed energy E of the main steel pipe 80 d is based on the absorbed energy of steel pipes described on page 17 of the "New Steel Erosion Control Structure Design Handbook, Reference Materials" and is expressed by the following formula (5).

[0047]

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[0048] Deformation of the steel tube 80 due to dent δ d When the dent rate of the main steel pipe is q, the following formula (6) is satisfied. Therefore, the dent deformation amount δ of the main steel pipe 80 d can also be set based on the dent rate q of the main steel pipe 80. The (dynamic) yield stress σ of the main steel pipe 80 yd is set appropriately depending on the type of steel pipe, etc.

[0049]

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[0050] The impact energy E of a pebble can be expressed, for example, by the following formula (7). In addition, if ρ is the unit weight of the pebble, g is the gravitational acceleration, W is the weight of the pebble, and r is the radius of the pebble = D0 / 2, then the mass of the pebble m = W / g, and W = 4πr 3 Since ρ / 3, m=4π(D0 / 2) 3 ρ / 3g. Therefore, the impact energy E of the gravel can also be set based on the diameter D0 of the gravel.

[0051]

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[0052] If the result of the gravel collision confirmation process S112 is safety, the main steel pipe 80 located at the most upstream side of the dam body 8 will be able to withstand gravel collisions, and the next manufacturing feasibility determination process S113 will be performed.

[0053] If the result of the gravel collision confirmation process S112 is not safe, the main steel pipe 80 located at the most upstream side of the dam body 8 will not be able to withstand the collision of gravel, so a new plate thickness t2 of the main steel pipe 80 is set so that the plate thickness t2 of the main steel pipe 80 is even larger, and the gravel collision confirmation process S112 is performed again.

[0054] In this way, by performing the static load confirmation process S111 and the gravel collision confirmation process S112, it is possible to narrow down the outer diameter D and plate thickness t of the main body steel pipe 80 that should be candidates for attaching the buffer steel pipe 10. Therefore, the design of the permeable sabo dam 100 can be completed in a shorter time.

[0055] In the gravel collision confirmation step S112, the gravel diameter D0, the gravel collision energy E, and the debris flow velocity are set, for example, as shown in Table 4 below. Also, in the gravel collision confirmation step S112, the dent rate q of the main steel pipe 80 is set to 10%, for example. As a result, the dent deformation amount δ of the main steel pipe 80 is calculated based on the formula (4). d can be set.

[0056] [Table 4]

[0057] In the gravel collision confirmation process S112, for example, as shown in Table 5 below, when the plate thickness t2 is set to the same value as the plate thickness t1, the absorbed energy E of the main steel pipe 80 is calculated based on the values ​​in Table 4 and the formula (5). d Calculate the (dynamic) yield stress σ of the main steel pipe. yd As a result, 315 (N / mm 2 ) was used.

[0058] [Table 5]

[0059] When the plate thickness t2 is set to the same value as the plate thickness t1, as shown in Table 5, in the gravel collision confirmation process S112, the absorbed energy E of the main steel pipe 80 on the most upstream side d The absorption energy E of the main steel pipe 80 is 37.93 kN m, which is less than the impact energy E of the gravel of 382.86 kN m shown in Table 4. d The plate thickness t2 must be made greater than the plate thickness t1 so that the impact energy E of the gravel is greater than or equal to the impact energy E of the gravel.

[0060] As a result, as shown in Table 6 below, when the plate thickness t2 is set to 70 mm, the absorbed energy E of the main steel pipe 80 on the most upstream side is d was 383.99 kN m, which is greater than the gravel collision energy E of 382.86 kN m shown in Table 4. Therefore, in the calculation examples in Tables 4 to 6, the plate thickness t2 is set to 70 mm based on the gravel collision energy E acting on the main steel pipe 80 at the most upstream side of the dam body 8.

[0061] [Table 6]

[0062] <Manufacturability determination process S113> Incidentally, even if the main steel pipe 80 is determined to be safe against collision with gravel in the gravel collision confirmation step S112, if the plate thickness t1 or plate thickness t2 is extremely too thick for the outer diameter D of the main steel pipe 80 or if the manufacturing cost is too high, it may be difficult to actually manufacture the main steel pipe 80. Therefore, in the manufacturing feasibility determination step S113, it is determined whether the main steel pipe 80 can be manufactured based on the set plate thickness t1 and plate thickness t2.

[0063] In the manufacturing feasibility determination step S113, a manufacturing limit is set in advance for the outer diameter D of the main steel pipe 80, and the manufacturing feasibility of the main steel pipe 80 is determined based on the manufacturing limit. The manufacturing limit is, for example, a plate thickness t max Set the manufacturing limit plate thickness t maxcan be set appropriately by the factory that manufactures the steel pipe, for example, 10% of the outer diameter D of the main steel pipe 80. The manufacturing limit may be any indicator that can determine whether the main steel pipe 80 can be manufactured, and may be set appropriately based on, for example, the relationship between the outer diameter D and the plate thickness t of the main steel pipe 80 and the manufacturing cost of the main steel pipe 80.

[0064] At least one of the plate thickness t1 and the plate thickness t2 is a manufacturing limit plate thickness t max If the manufacturing feasibility determination step S113 determines that the main steel pipe 80 cannot be manufactured, the buffer steel pipe setting step S12 is performed to install the buffer steel pipe 10 on the upstream side of the dam main body 8.

[0065] In addition, the manufacturing feasibility determination process S113 is performed when the plate thickness t1 is the plate thickness t max and the plate thickness t2 is less than the plate thickness t max In the following cases, it will be possible to manufacture the main steel pipe 80, so there is no need to install the buffer steel pipe 10 upstream of the dam main body 8, and the design method for the permeable sabo dam may end here.

[0066] In this way, by performing the manufacturing feasibility determination step S113 for the set outer diameter D, plate thickness t1, and plate thickness t2 of the main steel pipe 80, it is possible to narrow down the outer diameter D and plate thickness t of the main steel pipe 80 that should be candidates for attaching the buffer steel pipe 10. This makes it possible to design the permeable sabo dam 100 in a shorter time.

[0067] In the method for designing a permeable sabo dam, the manufacturing feasibility determination step S113 may be omitted.

[0068] For example, in the manufacturing feasibility determination step S113, the plate thickness t max is preset to 60 mm, which is 10% of the outer diameter D: 600 mm. In this case, the plate thickness t1 of the main steel pipe 80 shown in Table 1 set in the static load confirmation process S111 is 22 mm, and the plate thickness t maxOn the other hand, the thickness t2 of the main steel pipe 80 shown in Table 6, which was set in the gravel collision confirmation step S112, is 70 mm. max Therefore, in the manufacturing feasibility determination step S113, it is determined that the main steel pipe 80 with a plate thickness t2 of 70 mm cannot be manufactured. Therefore, it is necessary to install a buffer steel pipe 10 upstream of the main steel pipe 80, and the next buffer steel pipe setting step S12 is performed.

[0069] <Buffer steel pipe setting process S12> In the buffer steel pipe setting step S12, if the main steel pipe 80 is determined to be unmanufacturable in the manufacturability determining step S113, the outer diameter D' and plate thickness t' of the buffer steel pipe 10 are set based on the above formulas (1) to (3).

[0070] First, we will explain formula (1). As shown in formula (1), the plate thickness t' of the buffer steel pipe 10 is set to be less than the plate thickness t1 set in the static load confirmation process S111. In a calculation example, the plate thickness t' of the buffer steel pipe 10 is set to be less than the plate thickness t: 22 mm (plate thickness t1) shown in Table 5 set in the static load confirmation process S111.

[0071] Next, the formula (2) will be explained. First, the absorbed energy E d ´ is based on the absorbed energy of the steel pipe described on page 17 of the "New Steel Erosion Control Structure Design Handbook, Reference Materials" and is expressed by the following formula (8).

[0072]

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[0073] Deformation amount δ of the buffer steel pipe 10 d When the dent rate of the buffer steel pipe 10 is q', the following formula (9) is satisfied. Therefore, the dent deformation amount δ of the buffer steel pipe 10 d The dent deformation amount δ of the buffer steel pipe 10 can be set based on the dent rate q of the buffer steel pipe 10. d´ is the dent deformation amount δ of the main steel pipe 80 d It is preferable that the value is larger than σ. This allows the buffer steel pipe 10 to tolerate a larger deformation due to the impact of gravel. In addition, the (dynamic) yield stress σ yd ´ can be set appropriately depending on the type of steel pipe, etc.

[0074]

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[0075] Then, based on the formula (5) and the formula (8), the following formula (10) is derived.

[0076]

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[0077] In the formula (10), the (dynamic) yield stress σ yd and the (dynamic) yield stress σ of the buffer steel pipe 10 yd It is assumed that coefficient K is equal to coefficient α′. In addition, coefficient K is a function of gravel diameter D0 and outer diameter D of main steel pipe 80, and coefficient K′ is a function of gravel diameter D0 and outer diameter D′ of buffer steel pipe 10, so (coefficient K / coefficient K′) is set as coefficient α. Therefore, formula (2) is derived from formula (10).

[0078] Furthermore, when the outer diameter D of the main steel pipe 80 and the outer diameter D' of the buffer steel pipe 10 are equal, the coefficient α=1, so formula (2) can be expressed as the following formula (11).

[0079]

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[0080] Next, the formula (3) will be explained. The absorbed energy E of the buffer steel pipe 10 d Since ´ is required to be greater than or equal to the collision energy E of the gravel, formula (3) is derived.

[0081] Thus, in the buffer steel pipe setting process S12, the outer diameter D' and plate thickness t' of the buffer steel pipe 10 are set based on formulas (1) to (3). In the buffer steel pipe setting process S12, the outer diameter D' and plate thickness t' of the buffer steel pipe 10 are set so as to satisfy formulas (1) to (3). Since it is sufficient for the main steel pipe 80 to be able to resist at least static loads, the plate thickness t of the main steel pipe 80 may be set to plate thickness t1.

[0082] The buffer steel pipe setting step S12 will be described with a calculation example with reference to Tables 1 to 6. As shown in Table 7, in the buffer steel pipe setting step S12, for example, the outer diameter D' of the buffer steel pipe 10 is set to 600 mm. Also, the dent rate q' of the buffer steel pipe 10 is set to 50%.

[0083] In formula (1), the plate thickness t' of the buffer steel pipe 10 is less than the plate thickness t1 of the main steel pipe 80, which is 22 mm.

[0084] In formula (2), the outer diameter D' of the buffer steel pipe 10 is equal to the outer diameter D of the main steel pipe 80, so α=1.0. The plate thickness t2 of the main steel pipe 80 is 70 mm, and the dent deformation amount δ of the main steel pipe d is 60mm. The deformation of the buffer steel pipe is δ d From these, the plate thickness t' of the buffer steel pipe 10 is calculated to be 16.5 mm or more from the formula (2).

[0085] Then, based on the formula (1) and the formula (2), 16.5 mm≦plate thickness t'<22 mm is obtained. Therefore, for example, as a steel pipe widely distributed in the market, the plate thickness t' of the buffer steel pipe 10 is set to 19 mm. (Dynamic) yield stress σ of the buffer steel pipe yd ´, 315(N / mm 2 ) is used.

[0086] When the plate thickness t' of the buffer steel pipe is 19 mm, the absorbed energy of the buffer steel pipe 10 is calculated to be 512.60 kN m from the left side of formula (3). The collision energy E of the gravel, which is the right side of formula (3), is 382.86 kN m. This satisfies formula (3).

[0087] As described above, in the buffer steel pipe setting process S12, the outer diameter D' can be set to 600 mm and the plate thickness t' of the buffer steel pipe can be set to 19 mm based on the formulas (1) to (3). In this case, the outer diameter D of the main steel pipe 80 is 600 mm, and the plate thickness t is set to the plate thickness t1 of 22 mm.

[0088] [Table 7]

[0089] Similarly, in the buffer steel pipe setting step S12, the results when the outer diameter D' of the buffer steel pipe 10 is set to 700 mm, for example, are shown in Table 8 below.

[0090] [Table 8]

[0091] According to this embodiment, there is provided a buffer steel pipe setting process S12 for setting the outer diameter D' and plate thickness t' of the buffer steel pipe 10 constituting the buffer member 1 based on formulas (1) to (3). This makes it possible to appropriately select the outer diameter D' and plate thickness t' of the buffer member 1 of the permeable sabo dam 100 comprising the dam body 8 and the buffer member 1. As a result, the permeable sabo dam 100 can be designed effectively and economically.

[0092] According to this embodiment, the main steel pipe setting process S11 includes a manufacturing feasibility determination process S113 for determining whether the main steel pipe 80 can be manufactured, and the buffer steel pipe setting process S12 sets the outer diameter D' and plate thickness t' of the buffer steel pipe 10 if the main steel pipe 80 is determined to be unmanufacturable in the manufacturing feasibility determination process S113. This makes it possible to narrow down the outer diameter D and plate thickness t of the main steel pipe 80 to be considered as candidates. As a result, the design of the permeable sabo dam 100 can be made more effective and economical.

[0093] Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. Furthermore, the present invention can be implemented in various novel forms in addition to the above-mentioned embodiment. Therefore, the above-mentioned embodiment can be variously omitted, replaced, and modified without departing from the gist of the present invention. Such novel forms and modifications are included in the scope and gist of the present invention, and are included in the scope of the invention described in the claims and the equivalents of the invention described in the claims. [Explanation of symbols]

[0094] 100: Permeable sabo dam 1: Cushioning material 2: Mounting mechanism 10:Buffer steel pipe 11: 1st buffer steel pipe 21: First steel pipe 22: Second installation steel pipe 23: Fastening hardware 8: Dam body 80: Main body steel pipe 81: 1st main body steel pipe 82:Second main body steel pipe 83:Third main body steel pipe 89: Horizontal material 9:Foundation part S11: Main body steel pipe setting process S111: Static load confirmation process S112: Gravel collision confirmation process S113: Manufacturability determination process S12: Buffer steel pipe setting process X: Flow direction X1: Upstream side X2: Downstream side Y: width direction Z : Up and down direction

Claims

1. A method for designing a permeable sabo dam comprising a dam body made of a main body steel pipe and a buffer member attached to the dam body, comprising the steps of: The outer diameter D of the main steel pipe is set, The plate thickness t1 of the main body steel pipe is set based on the static load acting on the dam body, A main body steel pipe setting process for setting a plate thickness t2 of the main body steel pipe based on the collision energy E of gravel acting on the dam body; A buffer steel pipe setting process for setting the outer diameter D' and the plate thickness t' of the buffer steel pipe constituting the buffer member based on the following formulas (1) to (3). A design method for a permeable sabo dam characterized by the above. ##EQU00012## ##EQU00013## ##EQU00014##

2. The main body steel pipe setting process includes a manufacturing feasibility determination process for determining whether or not the main body steel pipe can be manufactured based on the set plate thickness t1 and the set plate thickness t2, The buffer steel pipe setting step includes setting the outer diameter D' and the plate thickness t' of the buffer steel pipe when the main steel pipe is determined to be unmanufacturable in the manufacturing feasibility determination step.

2. A method for designing a permeable sabo dam according to claim 1,

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