Installation structure of driftwood capture body and driftwood capture work

Abstract

To provide a driftwood capture body which is excellent in workability, economy and versatility and which does not require large construction machinery and can be attached and detached to a pile foundation and a driftwood capture pillar member on the mountain side of a conservation target in order to reduce damage caused by driftwood flowing out from mountainous areas, and which can be arbitrarily arranged in an optimal planar arrangement in a location where measures are required, and said driftwood capture body. [Solution] This driftwood trap is installed on the mountain side of a river or roadside of a conservation target, and is composed of a pile foundation that rotates autonomously and is fixed in the ground when the pile head is struck or pressed in the penetration direction, and a driftwood trap post member that is joined to the pile foundation. The driftwood trap post member is connected in a series with an insertion joint provided in the pile foundation and stands up. By installing the driftwood capture works in an optimal planar layout, the driftwood generated in mountainous areas and the like can be captured and preserved.

Description

[Technical field]

[0001] This invention relates to a driftwood capture body that captures driftwood flowing down from mountain slopes or rivers, etc., for the purpose of erosion control, forestry conservation, road disaster prevention, etc., and reduces or protects damage caused by driftwood to protected objects such as roads and houses, and to an installation structure for a driftwood capture work in which multiple such driftwood capture bodies are installed. [Background technology]

[0002] In recent years, the construction of driftwood capture countermeasures has been progressing, and there is a demand for more efficient prevention of disasters caused by driftwood flowing from mountainous areas, etc., within limited land area. To date, driftwood capture works have been proposed that have multiple pillars and cross beams supported by the pillars (Patent Document 1), a driftwood capture work that combines a concrete foundation with multiple pillars (Patent Document 2), and a driftwood capture work that combines a frame and pillars, eliminating the need to pour concrete on-site (Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 04-007405 (Driftwood retaining work) [Patent Document 2] JP2009-127280 (Driftwood capture structure) [Patent Document 3] Patent Publication 2022-85121 (driftwood capture device) Summary of the Invention [Problem to be solved by the invention]

[0004] However, these methods have the following drawbacks: In the event of a driftwood collision, it is necessary to ensure the stability of the driftwood capture work, so that multiple supports or combinations of the supports are used to resist horizontal external forces, which results in a large structure, and as a result, there is concern that the installation location will be limited (Patent Document 1). In addition, when combining and arranging the supports and underground foundation structures (concrete or framework), there is concern that the installation location will be limited in order to secure space for carrying in and out large construction machinery required for installation and earthwork excavation (Patent Documents 2 and 3). In addition, since the driftwood capture works in Patent Documents 1 to 3 are integrated with multiple supports and underground foundation structures, there are issues such as the need to replace only the support parts due to deterioration of components, and the difficulty of first removing the support parts when vehicles are driven into them when they are installed on the side of a road. Therefore, the present invention has been devised in consideration of the above-mentioned problems, and an object of the present invention is to provide a driftwood capture body and an installation structure for a driftwood capture work in which a plurality of driftwood capture bodies are installed, which has a structure that does not require a large-scale underground foundation structure to stabilize the driftwood capture work in the event of a collision with driftwood, and which allows the underground foundation structure and the support section to be easily attached and detached, and which can be optimally arranged in a plan view in areas where measures are required, and which is excellent in workability, economy, and versatility. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a driftwood capture device that is installed along the side of a river or road on the mountain side of the conservation target, characterized in that the driftwood capture device comprises a pile foundation that rotates autonomously and is fixed in the ground when the pile head is struck or pressed in the penetration direction, and a driftwood capture pillar member that is fixed to the pile foundation. It is also preferable that the driftwood capture body is characterized in that the pile foundation and the driftwood capture column member are connected in series with a detachable joint. In addition, it is preferable that the pile foundation is a driftwood capture body characterized by comprising a rod-shaped pile main body having a tapered pile tip that gradually reduces in diameter in the penetration direction, and a spiral portion that is formed in a spiral shape along the outer circumferential surface of at least a part or all of the outer circumferential surface of the pile main body, and has a spiral blade surface that converts a reaction force from the ground when the pile main body penetrates the ground into a rotational force of the pile main body. It is also preferable that the driftwood capture post member comprises a cylindrical body and an elongated reinforcing device provided within the cylindrical body, the reinforcing device having an outer cylindrical body consisting of a square cylindrical body having four corners and four sides, and an inner cylindrical body inserted into the outer cylindrical body and consisting of a square cylindrical body having four corners and four sides, and each corner of the inner cylindrical body abuts against a corresponding surface of the outer cylindrical body, making it a driftwood capture body having this feature. This is an installation structure for driftwood capture work which is composed of any of the driftwood capture bodies described above, and which is characterized in that the multiple driftwood capture bodies are installed with the horizontal spacing between the driftwood capture post members being within approximately half of the expected maximum driftwood length.

[0006] In addition, it is preferable that the driftwood capture work installation structure has the characteristic that the plurality of driftwood capture bodies are installed spaced apart in a substantially straight line in the river crossing direction in a plan view.

[0007] In addition, it is preferable that the driftwood capture work installation structure has the characteristic that the multiple driftwood capture bodies are installed at a distance from each other in a substantially fan-shaped or substantially inverted fan-shaped configuration when viewed from above.

[0008] In addition, it is preferable that the driftwood capture work installation structure has the characteristic that the multiple driftwood capture bodies are installed at a distance from each other along the meandering river crossing direction in a plan view.

[0009] In addition, it is preferable that the driftwood capture work installation structure has the characteristic that the multiple driftwood capture bodies are installed at a distance from each other along the road in a substantially straight line in a plan view. Effect of the Invention

[0010] According to the present invention, a driftwood capture body consisting of a pile foundation that is fixed in the ground while autonomously rotating when the pile head is struck or pressed in the penetration direction, and a driftwood capture pole member fixed to the pile foundation is installed in a river or flat land on the mountain side of the conservation target, eliminating the need for construction using large construction machinery. In addition, the driftwood capture pole member is connected in a series with an insertable, detachable joint provided at the vertical upper part of the pile foundation, so that the pile foundation and the driftwood capture pole member can be easily attached and detached or replaced as needed. Furthermore, by optimally arranging a plurality of these driftwood capture bodies at locations where measures are required on the river or roadside, driftwood generated from mountains can be effectively captured, so that the driftwood capture work can be installed with excellent workability, economy, and versatility. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an installation structure (driftwood capture work) composed of a driftwood capture body of the present invention and a plurality (two or more) of said driftwood capture bodies, where A is an elevation view from the side and B is an elevation view of the same from the front. [Diagram 2] FIG. 1 is a perspective view showing a driftwood capture device according to the present invention. [Diagram 3] FIG. 2 is a side view showing the pile foundation according to the present invention. [Figure 4] 1A is a perspective view showing a driftwood capturing post member according to the present invention, and FIG. 1B is a top view showing a reinforcing device according to the present invention. [Diagram 5] FIG. 2 is a side view of the driftwood capture device according to the embodiment. [Figure 6] FIG. 1 is a schematic diagram illustrating an outline of an experiment on load-bearing strength according to the present embodiment. [Figure 7] 1 is a table showing conditions of an experiment regarding load-bearing capacity according to the present embodiment. [Figure 8] 1 is a schematic diagram showing a rotation mechanism of driftwood in water according to an embodiment of the present invention. FIG. [Figure 9] FIG. 1 is a schematic diagram showing an overview of an experiment on the effect that differences in the installation structure of the driftwood capture structure according to this embodiment have on the driftwood capture function. [Figure 10]FIG. 13 is a schematic diagram showing a definition regarding the evaluation of the control effect of driftwood rotation in an experiment regarding the influence that differences in the installation structure of the driftwood capture work according to this embodiment have on the driftwood capture function. [Figure 11] 1 is a table showing the conditions of an experiment regarding the effect that differences in the installation structure of the driftwood capture structure according to this embodiment have on the driftwood capture function. [Figure 12] FIG. 13 is a diagram showing the results of an experiment on the influence of differences in the installation structure of the driftwood capture work according to this embodiment on the driftwood capture function (changes in driftwood rotation effect due to differences in supply flow rate). [Figure 13] FIG. 13 is a diagram showing the results of an experiment on the effect of differences in the installation structure of the driftwood capture work according to this embodiment on the driftwood capture function (changes in driftwood rotation effect due to differences in driftwood diameter and water depth). [Figure 14] FIG. 13 is a diagram showing the results of an experiment on the influence of differences in the installation structure of the driftwood capture work according to this embodiment on the driftwood capture function (changes in driftwood rotation effect due to differences in riverbed gradient changes). [Figure 15] FIG. 13 is a diagram showing the results of an experiment on the effect of differences in the installation structure of the driftwood capture work according to this embodiment on the driftwood capture function (changes in the driftwood rotation effect due to differences in the downstream length of the driftwood). [Figure 16] 1A and 1B are schematic diagrams showing variations in the installation structure of the driftwood capture work according to this embodiment, in which FIG. 1A is an elevation view from the side, and FIG. 1B is an elevation view of the same work from the front. [Figure 17] 1A and 1B are schematic diagrams showing variations in the installation structure of the driftwood capture work according to this embodiment, in which FIG. 1A is an elevation view from the side, and FIG. 1B is an elevation view of the same work from the front. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example, and various other forms are possible within the scope of the present invention.

[0013] FIG. 1 is a schematic diagram showing a driftwood capture body 4 according to the present invention and an installation structure (driftwood capture work 5) composed of a plurality (two or more) of driftwood capture bodies 4, in which A is an elevation view from the side and B is an elevation view from the front. The driftwood capture work 5 according to the embodiment has an installation structure in which a plurality (two or more) driftwood capture bodies 4 are arranged at intervals in a substantially linear manner in a cross direction of the river 6 on the mountain side of the conservation target 3 such as a road or a house in a plan view in order to prevent the driftwood 2 flowing down the river 6 together with the flowing water 7 from the mountain area 1 where trees that are the source of driftwood 2 grow. The driftwood capture body 4 is equipped with a cylindrical driftwood capture pole member 12 for passing the flowing water 7 to capture the driftwood 2, and a pile foundation 11 for stabilizing against an external force (load-bearing capacity) caused by a collision caused by the driftwood 2 flowing down the river 6. In addition, during maintenance, in order to respond to deterioration and damage to the driftwood capture body 4 over time, a concave insertion joint 13 is provided to join the driftwood capture pillar member 12 and the pile foundation 11 vertically and fix them in the horizontal direction. The horizontal installation interval of the driftwood capture bodies 4 constituting the driftwood capture work 5 according to this embodiment is set to within half the maximum length of the driftwood 2 specified in the explanation of the Debris Flow and Driftwood Countermeasures Design Technology Guidelines (p. 72) specified by the Ministry of Land, Infrastructure, Transport and Tourism, relative to the maximum length of the driftwood 2 specified in the explanation of the Guidelines for the Formulation of Basic Plans for Erosion Control (Debris Flow and Driftwood Countermeasures) (p. 36) specified by the Ministry of Land, Infrastructure, Transport and Tourism. The driftwood capture body 5 according to the embodiment is installed alone vertically to the ground 14, and it is desirable in terms of maintenance to install it as widely as possible to avoid clogging other than with the driftwood 2. The material constituting the driftwood capture body 4 can be selected from metal, wood, composite plastic, etc. in terms of strength and durability. In maintaining the driftwood capture work 5 according to the embodiment, periodic on-site inspections after installation are conducted to grasp the status of the driftwood capture work 5, such as its driftwood capture function and load-bearing capacity, and if it is blocked, the obstruction is removed as necessary to restore its function.

[0014] 2 is a perspective view showing a driftwood capture body 4 according to the present invention. The driftwood capture body 4 according to the embodiment includes a driftwood capture pole member 12 and a pile foundation 11, and the driftwood capture pole member 12 is inserted in the vertical axis direction into an insertion joint 13 at the top of the pile foundation 11 to join, and is fixed against external forces, particularly from the horizontal direction. In addition, in maintenance after installation of the driftwood capture body 4, the driftwood capture pole member 12 is replaced as necessary by attaching and detaching in the vertical axis direction. In addition, when the pile foundation 11 is struck or pressed in the penetration direction, it can penetrate into the ground 14 while automatically rotating.

[0015] FIG. 3 is a diagram showing a pile foundation 11 according to the present invention. The pile foundation 11 according to this embodiment is an underground foundation structure used as the foundation of a structure, and includes a pile body main portion 21 and an insertion joint 13. The pile body main portion 21 is a rod-shaped portion having a tapered pile tip portion 22 that gradually reduces in diameter toward the penetration direction and a pile base portion 23 with a constant shaft diameter, and a pile head 26 of the pile foundation 11 is struck or pressed in the penetration direction. In addition, the spiral portion 24 is formed in a spiral shape along the outer circumferential surface of the pile body main portion 21, and has a spiral blade surface 25 that converts a reaction force from the ground 14 when the pile body main portion 21 penetrates the ground 14 into a rotation force of the pile body main portion 21.

[0016] Since the pile tip 22 has a tapered shape that gradually reduces in diameter in the penetration direction, when the pile head 26 of the pile foundation 11 is struck or pressed, the pile body main body 21 can advance through the ground 14 while pushing aside the soil that constitutes the ground 14 in the penetration direction without undermining the surrounding ground. Although it depends on the properties of the ground 14 into which the pile foundation 11 is driven and the type of material of the pile foundation 11, for example, if the pile body main body 21 gradually reduces in diameter in the penetration direction so that the outer peripheral surface of the pile tip 22 has an inclination angle of 10 degrees or less with respect to the central axis of the pile body main body 21, in the case of the ground 14 composed of soil and sand, it can advance through the ground 14 while pushing aside the soil in the penetration direction without undermining the surrounding ground, regardless of the properties of the ground 14.

[0017] The spiral portion 24 rotates the pile foundation 11 by converting the reaction force from the ground 14 received by the spiral blade surface 25, which receives the reaction force when the pile head 26 of the pile foundation 11 is struck or pressed, into a rotational force of the pile body main body 21. In addition, the spiral portion 24 exerts a bearing force and a pull-out resistance force in the penetration direction when penetrated. Therefore, the spiral portion 24 has a strength sufficient to prevent plastic deformation even when it receives a reaction force from the ground 14 when the pile head 26 of the pile foundation 11 is struck. In addition, the spiral portion 24 has a number of turns sufficient to rotate the pile body main body 21. The strength of the spiral portion 24 is governed by the thickness, shape, material, etc. of the spiral portion 24. Therefore, for example, the thickness of the spiral portion 24 is appropriately determined taking into consideration the magnitude of the force striking or pressing the pile head 26 of the pile foundation 11, the material of the pile foundation 11, the properties of the ground 14, the length from the outer circumferential surface of the pile main body 21 to the outer edge of the spiral blade surface 25, the pitch of the spiral portion 24, the ratio of the number of turns of the spiral portion 24 to the total length of the pile main body 21, and various other factors. In addition, the number of turns of the spiral portion 24 depends on the properties of the ground 14, the length from the outer circumferential surface of the pile main body 21 to the outer edge of the spiral blade surface 25, etc., but it is considered that the performance of the pile can be efficiently exhibited by making the number of turns at least two turns.

[0018] The length of the spiral portion 24 from the outer circumferential surface of the pile main body 21 to the outer edge of the spiral blade surface 25 gradually increases from the upper end side to the lower end side of the pile main body 21, and the outer diameter of the spiral blade surface 25 is constant. Also, at the lower end portion of the pile main body 21, the length from the outer circumferential surface of the pile main body 21 to the outer edge of the spiral blade surface 25 gradually decreases in the penetration direction so that the spiral portion 24 can easily penetrate into the ground.

[0019] The pile foundation 11 according to this embodiment can be penetrated into the ground 14 by striking or pressing the pile head 26 of the pile foundation 11 by various construction methods such as striking, vibro-pressure, and pressing. In the early stage of penetration when the pile foundation 11 is almost not buried, the spiral part 24 at the tip, whose diameter gradually decreases as it approaches the penetration direction, gradually sinks into the ground, and the spiral part 24, which receives a reaction force from the ground 14 when the pile head 26 of the pile foundation 11 is struck or pressed, gradually begins to exert a rotational force to rotate the pile foundation 11. Then, the spiral part 24 begins to sink into the ground. As the spiral part 24 receives a reaction force from the ground, a sufficient rotational force to rotate the pile body main part 21 is obtained, and the pile body main part 21 can be sufficiently rotated by being buried in the ground 14.

[0020] With the pile foundation 11 according to this embodiment, if the pile head 26 of the pile foundation 11 is struck or pressed by various construction methods such as striking, vibro-pressure, and pressing, the pile will penetrate into the ground 14 while rotating autonomously, so there is no need to use a rotary penetration machine that penetrates the pile into the ground 14 while pressing and rotating it. In other words, with the pile foundation 11 according to this embodiment, there is no need to use a large-scale rotary penetration machine, so it is possible to improve workability and reduce costs.

[0021] In addition, the pile foundation 11 according to this embodiment has a tapered shape at the pile tip 21, which gradually reduces in diameter in the penetration direction, and therefore has high penetration properties. Therefore, compared to a pile that does not have a tapered tip, the impact force or pressing force applied to the pile can be relatively small. Therefore, for example, with the pile foundation 11 according to this embodiment, the pile foundation 11 can easily reach the supporting layer in the ground 14 even if the supporting layer is located slightly deep below the ground surface.

[0022] As shown in Fig. 3, the spiral portion 24 is formed in a spiral shape at a uniform pitch along the central axis of the pile main body 21. If the spiral portion 24 is formed in a spiral shape at a uniform pitch along the central axis of the pile main body 21, the spiral portion 24 can easily penetrate the ground 14 in a spiral shape without undermining the surrounding ground when the pile foundation 11 is penetrated into the ground 14. However, the spiral portion 24 is not limited to being formed at a completely uniform pitch along the central axis of the pile main body 21, and for example, the pitch near the tip may be slightly different from other portions.

[0023] 3 shows the pile body main portion 21 having the pile base portion 23 with a constant shaft diameter, the pile foundation 11 according to the present embodiment is not limited to having the pile base portion 23. In the pile foundation 11, most of the pile body main portion 21 gradually reduces in diameter in the penetration direction, and the pile base portion 23 may be omitted.

[0024] 3 shows the spiral portion 24 formed in a spiral shape along the outer circumferential surface of the pile tip portion 21 and the outer circumferential surface of the pile base portion 23, but the pile foundation 11 according to this embodiment is not limited to this form. The spiral portion 24 may be formed only on the whole or part of the outer circumferential surface of the pile tip portion 21, and may be omitted on the outer circumferential surface of the pile base portion 23.

[0025] 4a is a perspective view showing the driftwood capture pole member 12 according to the present invention. The driftwood capture pole member 12 according to this embodiment includes a cylindrical body 41 that is inserted into and fixed to an insertion joint 13 installed in the ground 14, and an elongated reinforcing device 42 provided in the cylindrical body 41.

[0026] 4b is a top view showing an elongated reinforcing device 42 provided in the cylindrical body 41 of the driftwood capturing post member 12 according to the present invention. The reinforcing device according to this embodiment has an outer cylindrical body 43 made of a regular square cylinder having four corners 43a and four faces 43b, and an inner cylindrical body 44 made of a regular square cylinder having four corners 44a and four corners 44b, which is attached to the outer cylindrical body 43. Each corner 44a of the inner cylindrical body 44 abuts against a face 43b corresponding to the outer cylindrical body 43. Each corner portion 44a of the internal cylinder body 44 according to this embodiment is fixed to a center portion 43c of a corresponding surface 43b of the external cylinder body 43 by welding. Central portion 43c of corresponding surface 43b of external cylindrical body 43 according to this embodiment is a central portion of surface 43b between corner portions 43a of external cylindrical body 43. Since each corner portion 44a of internal cylindrical body 44 abuts against central portion 43c of corresponding surface 43b of external cylindrical body 43, external cylindrical body 43 formed of a regular square cylinder and internal cylindrical body 44 formed of a regular square cylinder are arranged in shapes obtained by rotating similar shapes by 45° each other. The reinforcing device 42 according to this embodiment is composed of an outer cylindrical body 43 and an inner cylindrical body 44 which have similar shapes and are rotated by 45° each other, and as a result, the reinforcing device 42 itself has high bending rigidity. A central portion 43c of the corresponding surface 43b of the cylindrical body 43 is a central portion of the surface 43b between the corners 43a of the external cylindrical body 43. Since each corner 44a of the internal cylindrical body 44 abuts against a central portion 43c of the corresponding surface 43b of the external cylindrical body 43, the side cylindrical body 43 made of a regular square cylinder and the internal cylindrical body 44 made of a regular square cylinder are arranged in shapes similar to each other but rotated by 45°.

[0027] 5 is a side view showing an example of a driftwood capture body 4 according to the embodiment. A part of the lower part of the cylinder 41 and the reinforcing device 42 constituting the driftwood capture pole member 12 according to the present embodiment is inserted into the concave insertion joint 13 at the upper part of the pile foundation 11 and embedded in the ground 14. The lower part of the cylinder 43 and the reinforcing device 42 is excavated by manual work using a shovel or a simple rock drill, etc., and is surrounded by mortar 31 filled in the space in the ground 14 to be reinforced in the space secured in the ground 14. Note that concrete or quarried stone may be used instead of the mortar 31. The standard lengths and structures of the driftwood capture body 4 according to this embodiment are as shown in Fig. 5, and can be changed according to the installation conditions. The length L1 from the surface of the ground 14 to the top end of the driftwood capture body 4 is the length required to capture the driftwood 2, and the length L2 from the surface of the ground 14 to the bottom end is determined based on the load expected when the driftwood 2 collides and the strength of the ground 14. Other lengths are also determined to be the necessary lengths. <Example 1> Next, we will explain an example of an experiment on the load-bearing performance of the driftwood capture body 4. We created a 1 / 1 scale model of the driftwood capture body 4 consisting of the pile foundation 11 and the driftwood capture pillar member 12, and investigated the stability performance of the driftwood capture body 4 due to the action at the time of collision with driftwood 2 assumed to be carried down by a debris flow. Fig. 6 is a schematic diagram showing an outline of the load-bearing capacity experiment carried out in accordance with the present invention, and Fig. 7 is a table showing the conditions of the load-bearing capacity experiment carried out in accordance with the present invention. As shown in Fig. 6 and Fig. 7, the stability was evaluated assuming that an iron block 51 weighing 1805 kg was collided with the driftwood catcher 4 at a height of 200 mm in the horizontal direction at the maximum speed of 47.1 km / h that is generally assumed for debris flow. The total length of the driftwood catcher pillar member 12 was 850 mm, and the total length of the pile foundation was 850 mm. As a result of this collision test, it was found that the driftwood catcher 4 was able to sufficiently resist external forces, even though some parts were deformed. As described above, the proposed driftwood capture pile 4 is considered to be a useful structure that is fully capable of capturing driftwood 2 that typically flows down with debris flows. <Example 2> Next, an example of an experiment on the capture function of driftwood capture works 5 will be described. With reference to past disaster cases caused by driftwood 2, the effects on the capture function of differences in the placement conditions of driftwood countermeasure works 5 proposed in mountainous areas 1 watersheds and forest areas will be examined. When installing driftwood capture works 2 in rivers 6, there are generally concerns about the effects of blockages caused by not only driftwood 5 but also garbage and the like. It is also necessary to take note of the need to secure additional land when capturing driftwood 2 and of daily maintenance (inspection, maintenance and repair). In this case, the effects of changes in the flow immediately upstream of the driftwood capture works 5 can be considered. Figure 8 is a schematic diagram showing the rotation mechanism of driftwood 2 in water expected in the present invention. When affected by a sudden change from a gentle gradient section to a steep gradient, the driftwood 2 rotates in the direction of flow (for example, the difference in flow speed Vn±1 shown in Figure 8 affects the rotation force +ωn of the driftwood 2), and there is a concern that the pile installation interval of the driftwood catcher 4 commonly used (half the maximum length of driftwood that may flow down, as indicated in the explanation of the debris flow and driftwood countermeasures design technical guidelines by the Ministry of Land, Infrastructure, Transport and Tourism) will not function sufficiently and the driftwood 2 will pass through between the driftwood catchers 4 as it is. On the other hand, if the interval between the driftwood catchers 4 is significantly narrowed, a lot of additional maintenance will be required to prevent daily blockage by garbage, etc. Therefore, in order to effectively capture driftwood 2 even when driftwood capture bodies 4 are spaced apart relatively widely, we propose an installation structure for driftwood control works 5 that rotates the driftwood 2 in a direction in which the driftwood capture works 5 are advantageous (as shown in Figure 8, the direction perpendicular to the flow: θn+1 is large) and focuses on installation on flat ground such as debris flow deposits and roadside areas where the flow is generally thought to change significantly (from rapid to slow: +ωn). Here, we consider the rotation of the driftwood 2 (FIG. 8) expected when it flows down from a steep channel to a flat area with a gentle slope. FIG. 9 is a schematic diagram showing an outline of an experiment on the influence of the difference in the installation structure of the driftwood capture work 5 carried out in the present invention on the capture function of the driftwood 2. As shown in FIG. 9, assuming a scale of about 1 / 100 of the actual scale, water 61 (qin) and driftwood 2 (however, circular material, driftwood length 8 cm, specific gravity in dry state: about 0.75, manually thrown in: throwing speed about 1 piece per hour / 0.5 seconds) were supplied from the upstream of an inclined straight waterway 62 (width 10 cm), and the axial direction θn of the driftwood 2 was measured immediately before the driftwood 2 was captured on a flat flooding platform 63 downstream. FIG. 10 is a schematic diagram showing the definition of the evaluation of the driftwood rotation control effect in the experiment on the influence of the difference in the installation structure of the driftwood capture work 5 implemented in the present invention on the driftwood capture function. Regarding the input of driftwood 2, it is known that driftwood 2 flowing down in a group is easy to capture, and in order to reduce this influence, driftwood 2 is input individually. In addition, in order to take into consideration that the difference in the supply conditions of driftwood 2 (initial input direction) does not affect the rotation control effect of driftwood 2 (FIG. 8), the direction of driftwood 2 is input so that it is approximately the same in all directions in the horizontal plane of the flow. The inclination angle of the straight waterway 62 is based on the debris flow flow section (general debris flow flow section of 10 degrees or more as indicated in the commentary on the guidelines for formulating the basic plan for erosion control). In addition, the input position Lw of driftwood 2 and the evaluation position (capture work position) Lp of the driftwood 2 direction on the flat flood bed 63 are changed (FIG. 9). In addition, in preliminary experiments, the effects of differences in the mixing of sediment into the water 61, the addition of branches to the driftwood 2, the speed at which the driftwood 2 is introduced, etc., are understood in advance. In order to understand the effect of differences in each experimental condition on the rotation of the driftwood 2, the flow rate (qin) of the water 61, the waterway gradient (straight waterway 62: θw, flat flooding table 63: θp), the diameter φ1 of the driftwood 2, etc. are changed to compare the effect of the rotation of the driftwood 2 (control: Figure 10) under each condition. In addition, in order to reduce the effect of manually inserting the driftwood 2, the experiment is carried out three times under the same conditions to average the results. Fig. 11 is a table showing the conditions of an experiment regarding the effect of differences in the installation structure of the driftwood capture work 5 implemented in the present invention on the driftwood capture function. Regarding the rotation of the driftwood 2 in the experimental results, the rotation effect of the driftwood 2 accompanying the change in flow at the time of evaluation (driftwood rotation rate) fc is the ratio obtained by dividing n0 by nw. Here, n0 is the number of driftwood 2 pieces placed at the measurement position Lp on the flat flood table 63 with θn of 45 degrees or more (Fig. 10), and nw is the number of driftwood 2 supplies (Fig. 9). Below, we will consider the effect of differences in the experimental conditions on the rotation effect of the driftwood 2. Fig. 12 is a diagram showing the results of an experiment on the influence of differences in the installation structure of the driftwood capture work 5 according to this embodiment on the capture function of the driftwood 2 (changes in driftwood rotation effect due to differences in the supply flow rate of water 61). As shown in Fig. 12, as the flow rate of the water 61 increased, the rotation effect of the driftwood 2 became more prominent. According to observations during the experiment, when the driftwood 2 was transported from the straight waterway 62 to the flat flooding table 63, the driftwood 2 rotated due to the effect of the difference in flow speed occurring upstream and downstream (Fig. 8), and this difference in flow speed upstream and downstream became more prominent as the flow rate of the water 61 increased. Fig. 13 is a diagram showing the results of an experiment on the influence of differences in the installation structure of the driftwood capture work 5 according to this embodiment on the capture function of the driftwood 2 (changes in the rotation effect of the driftwood 2 due to differences in the diameter of the driftwood 2 and the depth of the water 61). As shown in Fig. 13, the rotation effect became more pronounced as the diameter of the driftwood 2 became smaller and the depth of the water 61 became greater. According to observations during the experiment, it is believed that this is because the difference in flow speed between the upstream and downstream became more pronounced as the water 61 (flow rate) became larger, and the driftwood 2 became more susceptible to the influence of the current as its weight became smaller. For this reason, it is believed that the driftwood 2 is particularly susceptible to the influence of the current in the upstream area where the width of the river 6 is narrow and the size of the driftwood 2 flowing downstream is small. Fig. 14 is a diagram showing the results of an experiment on the influence of differences in the installation structure of the driftwood capture work 5 according to this embodiment on the capture function of the driftwood 2 (changes in the rotation effect of the driftwood 2 due to differences in the riverbed gradient). As shown in Fig. 14, it was confirmed that changes in flow speed influenced by the riverbed gradient affect the rotation effect of the driftwood 2 (Fig. 8). FIG. 15 is a diagram showing the results of an experiment on the influence of the difference in the installation structure of the driftwood capture work 5 according to this embodiment on the capture function of the driftwood 2 (change in the rotation effect of the driftwood 2 due to the difference in the flow length of the driftwood 2). As shown in FIG. 15, it was confirmed that the flow length of the driftwood 2 has almost no effect on the rotation effect of the driftwood 2. According to the observation during the experiment, as described above, it is considered that the rotation of the driftwood 2 mainly occurs near the change in the flow speed of the water 61. From these results, by utilizing the topography and the accompanying flow changes seen in the flat land between the valley along the road and the sand deposit area of ​​the existing dam, it is possible to economically arrange the driftwood capture bodies 4 of the driftwood capture work 5 at relatively wide intervals, which is considered to be rational in terms of maintenance, management, land use, etc. <Example 3> This shows an example of installation of driftwood capture works 5 of the present invention in a sandy area 72 immediately upstream of a dam 71. Figure 16 is a schematic diagram showing variations in the installation structure of driftwood capture works 5 of the present invention, where A is a side elevation and B is the same elevation from the front. As shown in Figure 16, the dam 71 is the confluence of two upstream rivers 6 (mountain area 1), and the flow is concentrated in the center of the river channel by a tailrace (water passage) sleeve about 1 m high, and it is considered effective to capture driftwood by arranging driftwood capture works 5 in a roughly fan-shaped configuration in plan view immediately upstream of this tailrace. If it is desired to avoid capturing driftwood 2 in the driftwood capture works 5 due to the conditions of cooperation, the driftwood capture works 5 are installed at intervals in a roughly inverted fan shape in the opposite direction to the flow in order to transport part of the driftwood 2 outside the transverse direction of the dam 71 in plan view. Also, if the river 6 flows downstream in a meandering rather than straight line due to the surrounding topographical conditions in plan view, the driftwood capture works 5 are installed at intervals in the transverse direction of the river 6, taking into account the meandering topographical conditions. On the other hand, since the basin is an upstream basin, the drainage area is small and the depth of the flowing water 7 passing through the spillway is thought to be shallow. Therefore, as an alternative to conventional driftwood capture piles (minimum total length: 2 m), a new small driftwood capture body (total length of driftwood capture pole member 12: 850 mm) is provided. <Example 4> An example of installation of the driftwood capture work 5 of the present invention on flat ground 82 beside a road 81 is shown in Fig. 17. Fig. 17 is a schematic diagram showing a variation of the installation structure of the driftwood capture work 5 of the present invention, where A is a side elevation view and B is the same elevation view from the front. As shown in Fig. 17, taking advantage of the topographical conditions of the flat ground 82 existing between the road 81 and the river 6 in the mountainous area 1, the driftwood capture works 5 are installed at intervals in a substantially straight line along the road 81 beside the road 81 in a plan view. Similarly, the driftwood capture bodies 4 are small (total length of the driftwood capture pole members 12: 850 mm). [Explanation of symbols]

[0028] 1 Mountain area 2. Driftwood 3. Roads, houses, etc. to be protected 4. Driftwood trap 5. Driftwood capture works 6. Rivers 7 Running water 11 Pile foundation 12 Driftwood capture pole components 13 Insertion type coupling 14 Ground 21 Pile Headquarters 22 Pile tip 23 Pile base 24 Spiral Section 25 Spiral blade surface 26 Pile head 31 Mortar 41 Cylinder 42 Reinforcement Device 43 Outer cylinder 44 Inner tube 45 Cap 43a Corner 43b side 43c central part 44a Corner 44b side 51 Iron Lump 61 water 62 straight waterway 63 Flat flood platform 64 Pump 71 Dam 72 Sediment land 81 Road 82 Flat

Claims

1. A driftwood capture device to be installed in rivers and flat areas on the mountain side of the conservation target, The driftwood capture body is a pile foundation that rotates autonomously and is fixed in the ground when the pile head is struck or pressed in the penetration direction; A driftwood capture pole member fixed to the pile foundation, The driftwood capture pole member comprises a cylindrical body and an elongated reinforcing device provided within the cylindrical body, The reinforcing device includes an outer cylindrical body made of a rectangular cylinder having four corners and four faces, and an inner cylindrical body made of a rectangular cylinder having four corners and four faces and inserted into the outer cylindrical body, A driftwood capture device, characterized in that each corner of the inner cylindrical body abuts against a corresponding surface of the outer cylindrical body.

2. 2. The driftwood capture device according to claim 1, wherein the pile foundation and the driftwood capture pole member are connected in series by a detachable joint.

3. The pile foundation includes a rod-shaped pile main body having a tapered pile tip portion that gradually reduces in diameter toward the penetration direction, The driftwood capture device described in claim 1, further comprising a spiral portion having a spiral blade surface that is formed in a spiral shape along at least a part or all of the outer peripheral surface of the tip of the pile main body, and that converts a reaction force from the ground when the pile main body penetrates the ground into a rotational force of the pile main body.

4. A plurality of driftwood traps according to any one of claims 1 to 3, This driftwood capture structure is characterized in that the multiple driftwood capture bodies are installed with the horizontal spacing between the driftwood capture post members being within approximately 1 / 2 of the expected maximum driftwood length.

5. 2. The driftwood capture work installation structure according to claim 1, wherein the driftwood capture bodies are installed spaced apart in a substantially linear manner in the river crossing direction in a plan view.

6. 2. The driftwood capture structure according to claim 1, wherein the driftwood capture bodies are installed spaced apart in a generally fan-shaped or generally inverted fan-shaped configuration in plan view.

7. 2. The driftwood capture work installation structure according to claim 1, wherein the driftwood capture bodies are installed spaced apart in a cross direction of the meandering river in a plan view.

8. 2. The driftwood capture work installation structure according to claim 1, wherein the driftwood capture bodies are installed at intervals along the road at the edge of the road in a substantially straight line in a plan view.

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