Debris flow countermeasure structure and debris flow countermeasure construction method

Abstract

To provide a debris flow countermeasure structure and a debris flow countermeasure construction method that can ensure long-term durability and high reliability by being resistant to effects of soil changes on quality even in soft ground and effects of obstacles such as boulders on construction.SOLUTION: A debris flow countermeasure structure according to the present invention is provided with a debris flow countermeasure foundation 1 which has a muddy improved ground 11 generated in a foundation hole formed by excavating the ground G, multiple support members 20 inserted and erected into the improved ground 11, and an upper structure 50 disposed on the upper part. On the upper part of the support members, a joint part is formed to connect components of a frame-structured steel erosion control structure made of steel pipes and H-shaped steel.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention relates to a debris flow countermeasure structure and a debris flow countermeasure construction method used on soft ground such as anhydrous streams (small-scale streams). [Background technology]

[0002] In recent years, heavy rain disasters have become more frequent, and the number of debris flow disasters has also increased. In particular, landslides that occur in small streams or streams without running water have been pointed out as a characteristic of landslides that cause human casualties. For example, the "Technical Considerations for Measures for Streams without Running Water (Trial Draft)" issued by the Erosion Control Department of the Water Management and Disaster Management Bureau of the Ministry of Land, Infrastructure, Transport and Tourism in March 2022 lists the following characteristics of streams without running water and small streams that may cause debris flows. 1) A stream with an unclear flow path, no constant flow of water, and no expected sediment movement under normal circumstances 2) Streams with a riverbed gradient of 10° or more and where the entire river basin is a debris flow zone. Furthermore, the commentary states that "although non-running streams have a valley shape, most of the drainage basin is often composed of zero-order valleys or slopes, and the frequency and scale of sediment runoff during small to medium-sized floods is small. "It also points out that non-running streams and small-scale streams "often have residences close to the valley outlets, so if a debris flow occurs, there is a high possibility that it will directly lead to human casualties," and indicates the need for countermeasures.

[0003] Furthermore, because these streams are small in scale, the usual debris flow prevention works (sabo dams) are not only excessively large in scale, but are also restricted by the proximity of dwellings and the need to secure construction roads, making it difficult to construct sabo facilities in the usual way. Therefore, there is a need for a more rational method of constructing facilities from the standpoint of ease of construction and cost reduction. Regarding debris flow countermeasures for non-flowing streams ("small-scale streams") which have many such constraints, structures have been disclosed that use steel materials in a lattice or beam shape on a concrete foundation, as well as structures that use steel pipe piles driven in to connect the steel materials (for example, see Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] https: / / www.proteng.co.jp / product_detail.php?keyno=33 [Non-Patent Document 2] http: / / jw-safety.jp / product / jdfence / index.html Summary of the Invention [Problem to be solved by the invention]

[0005] However, such debris flow prevention works are subject to restrictions due to construction and ground conditions, and it is difficult to say that they are easy to work with. For example, when concrete foundations are required, it may be difficult to transport concrete to the site in narrow streams where construction roads cannot be secured, and when pile foundations are required, large-scale construction machinery may be required or driving piles may be difficult due to gravel or boulders in the ground.

[0006] Furthermore, non-flowing streams (small streams) may be formed from landslide deposits or debris flow deposits, and the ground may be relatively soft. This may make them unsuitable as supporting ground for small-scale debris flow prevention works that require concrete foundations. In the case of pile-type structures, there is an issue that passive resistance to debris flow loads is low. Thus, the condition of the ground can have a significant impact on the reliability of structures.

[0007] The present invention was devised based on this technical background, and its object is to provide a debris flow countermeasure structure and a debris flow countermeasure construction method that are less susceptible to the effects of the ground, even on soft ground, and that can ensure long-term durability and high reliability.

[0008] The present invention relates to The debris flow countermeasure foundation is constructed on a non-flowing stream or a small stream, and comprises an improved ground consisting of a solidified body formed by pouring a base material containing locally generated soil and sand, and cement milk or cement and water into a foundation hole formed by excavating the ground, stirring and kneading the base material to form a muddy improved soil in the foundation hole, and a plurality of support members consisting of steel pipes, H-shaped steel, or channels, which are inserted and erected in the improved ground in a substantially vertical direction and integrated with the improved ground, and on top of which a superstructure is placed. It is characterized by: or The support member has a connecting portion formed at the upper portion thereof for connecting members of a steel erosion control structure having a frame structure made of a steel pipe, an H-shaped steel, or a channel. 2. The debris flow prevention structure according to claim 1. It is characterized by: or The plurality of support members include A plurality of first support members arranged in a width direction when viewed along the flow of the debris flow; A plurality of second support members arranged downstream in the flow direction of the debris flow corresponding to the first support members; Equipped with It is characterized by: or A beam member is provided to connect the first support member and the second support member. It is characterized by: or A member of a steel erosion control structure having a frame structure consisting of a steel pipe, an H-shaped steel, or a channel, which is a superstructure, is connected to the upper part of the support member. It is characterized by: or A method for constructing debris flow countermeasures, comprising the steps of: Excavate the site where the debris flow prevention structure is to be constructed, located in a non-flowing stream or a small stream, to form a foundation hole, A base material containing on-site generated soil and sand and cement milk or cement and water are poured into the foundation hole, and stirred to generate muddy improved soil in the foundation hole; When a predetermined amount of muddy improved soil is generated in the foundation hole, a support member consisting of a plurality of steel pipes, H-shaped steel, or a channel is inserted into the muddy improved soil in a substantially vertical direction and erected to solidify the muddy improved soil, The improved ground, which is made of solidified muddy improved soil, is integrated with the erected support members. Construct foundations for debris flow prevention works, It is characterized by: or The plurality of support members include: A plurality of first support members arranged in a width direction when viewed along the flow of the debris flow; A plurality of second support members corresponding to the first support members and arranged downstream in the direction of the debris flow are inserted and erected to construct a foundation for the debris flow countermeasure work. It is characterized by: or A method for constructing a debris flow countermeasure structure having a plurality of debris flow countermeasure foundation works, comprising: A plurality of sections are set for excavating the foundation hole, A foundation structure for debris flow countermeasures according to claim 6 or claim 7 is formed in any one of the sections, After forming one debris flow countermeasure foundation, a foundation hole is formed in another section, and the debris flow countermeasure foundations are constructed in sequence. It is characterized by: Effect of the Invention

[0009] The debris flow countermeasure structure and debris flow countermeasure construction method of the present invention are less likely to be affected by changes in soil quality, even on soft ground, and construction is less likely to be affected by obstacles such as boulders, and because the superstructure is integrated with the ground, long-term durability and high reliability can be ensured. [Brief description of the drawings]

[0010] [Figure 1] 1 is a front view showing the general configuration of a debris flow countermeasure structure according to one embodiment of the present invention, viewed along the direction of debris flow flow. FIG. [Diagram 2]FIG. 2 is a front view illustrating the configuration of the main parts of a debris flow countermeasure structure according to one embodiment, viewed along the direction of debris flow flow. [Diagram 3] 1A and 1B are diagrams illustrating the configuration of the main components of a debris flow prevention structure according to one embodiment, in which (A) is a side view and (B) is a perspective view. [Figure 4] 1A and 1B are diagrams illustrating the configuration of the main parts of a debris flow countermeasure structure according to a modified embodiment of the present invention, in which (A) is a side view and (B) is a perspective view. [Diagram 5] FIG. 2 is a diagram illustrating an outline of a method for constructing debris flow countermeasures according to one embodiment. [Figure 6] FIG. 2 is a diagram for explaining an outline of constructing a plurality of debris flow countermeasure structures in a debris flow countermeasure construction method according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a debris flow countermeasure structure according to one embodiment of the present invention will be described with reference to Figs. 1 to 3. Figure 1 is a front view seen along the direction of the debris flow flow, explaining the general configuration of a debris flow countermeasure structure in one embodiment of the present invention, Figure 2 is a front view seen along the direction of the debris flow flow, explaining the main configuration of the debris flow countermeasure structure, Figure 3 is a diagram explaining the main configuration, Figure 3(A) is a side view, and Figure 3(B) is an oblique view of a support member. In the figure, reference numeral 1 indicates the debris flow prevention work structure (as a whole), reference numeral 10 indicates the debris flow prevention work foundation formed in a designated area, reference numeral 11 indicates the improved ground, reference numeral 20 indicates a support member, reference numeral 21 indicates the first support member, reference numeral 22 indicates the second support member, and reference numeral 50 indicates a component (superstructure) of the steel erosion control structure having a frame structure made of steel pipes and H-shaped steel.

[0012] The debris-flow control structure 1 is constructed on soft ground, such as a waterless stream (small-scale stream), and as shown in Figure 1, it comprises debris-flow control structures 1A, 1B, 1C, 1D, and 1E corresponding to sections set up in, for example, five ground G, with the debris-flow control structure 1C at the lowest position being replaced by the debris-flow control structure 1B, the debris-flow control structure 1A, the debris-flow control structure 1D, and the debris-flow control structure 1E being arranged in successively higher positions on the left and right. Furthermore, as shown in FIG. 2, each of the debris flow control structures 1 (1A, 1B, 1C, 1D, 1E) includes, for example, a debris flow control foundation work 10, a covering work 12, and a frame-structured steel sand control structure member (column material) (superstructure) 50. The number and arrangement of the debris-flow countermeasure structures constituting the debris-flow countermeasure structure 1 may be set arbitrarily, and for example, the debris-flow countermeasure structure 1 may be constituted by a single debris-flow countermeasure structure.

[0013] The debris flow prevention work foundation 10 includes, for example, improved ground 11 and a plurality of support members 20. The improved ground 11 is formed by first digging out the target soil within the block range, and then mixing and stirring the excavated soil with cement milk or the like while returning it. Specifically, the improved ground 11 is formed in a foundation hole that is individually formed by excavating each set section, and is made of a base material containing on-site soil and cement milk or cement and water, which is mixed and stirred to produce a muddy improved soil, which is then solidified. Here, the base material containing on-site soil may contain, for example, on-site soil plus gravel, crushed stone, steel slag, or other modifying materials. The muddy improved soil 11A has properties roughly equivalent to those of a flowing type soil cement material (erosion control soil cement material), and the solidified improved ground (solidified body) generally has low strength (<3N / mm 2 ) is equivalent to the flow type of soil cement (sand control soil cement).

[0014] The covering work 12 is placed on top of the debris flow prevention work foundation work 10. Since the improved ground 11 may be affected by deterioration when it is exposed to the ground surface, the covering work 12 may be covered with protective concrete, sprayed mortar, soil, sand, etc. The configuration of the covering work 12 and whether or not to place the covering work 12 may be set arbitrarily.

[0015] The support member 20 includes, for example, a first support member 21 and a second support member 22, and a plate (connecting portion) 20A is formed on the upper portion (upper end portion) of the support member 20. The configuration of the first support member 21 and the second support member 22 can be set arbitrarily, but in this embodiment, the first support member 21 and the second support member 22 are made of, for example, H-shaped steel, and are inserted approximately vertically into the pile of improved muddy soil, erected, and buried after the improved muddy soil has solidified and an accumulation body has been formed, but before the improved ground 11 is formed.

[0016] The first support members 21 are arranged in plurality in the width direction when viewed along the flow direction of the debris flow, for example. Furthermore, a plate (connecting portion) 21A is formed on the upper portion of the first supporting member 21 for connecting a member (superstructure) 50 of a steel erosion control structure having a frame structure made of steel pipes or H-shaped steel. The plate 21A is attached by welding or bolts, for example. The configuration of the connecting portion 21A may be set arbitrarily, and it is not limited to the plate 21A, and may be configured by attaching a flange, bracket, fastening structure, etc., or may be configured by a bolt hole formed in the upper portion of the first supporting member 21.

[0017] The second support members 22 are arranged, for example, on the downstream side in the flow direction of the debris flow in correspondence with each of the multiple first support members 21. Moreover, a plate (connecting portion) 22A is formed on the upper portion of the second supporting member 22 for connecting a member (superstructure) 50 of a steel erosion control structure having a frame structure made of steel pipes or H-shaped steel. The plate 22A is attached by welding or bolts, for example. The configuration of the connecting portion 21A may be set arbitrarily, and is not limited to the plate 22A, and may be configured by attaching a flange, bracket, fastening structure, or the like, or may be configured by a bolt hole formed in the upper portion of the first supporting member 21.

[0018] A member (superstructure) 50 of a steel sand control structure having a frame structure made of steel pipes or H-shaped steel is provided with pillar members extending approximately vertically and connected to the upper parts of the first support member 21 and the second support member 22 via connecting parts 21A and 22A, respectively, as shown in Figures 1 and 2. The member 50 of the steel sabo structure with a frame structure made of steel pipes or H-shaped steel may be provided with steel materials or wires for preventing debris flow, forming a permeable sabo dam, which traps driftwood and debris and prevents them from flowing downstream.

[0019] Next, a debris flow countermeasure structure according to a modification of an embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the configuration of the main parts of the debris flow countermeasure structure according to a modification of an embodiment, with Fig. 4(A) showing a side view and Fig. 4(B) showing a perspective view. In Fig. 4, reference numeral 40 denotes a beam member. As shown in FIG. 4, the debris flow control structure 1 (1A, 1B, 1C, 1D, 1E) relating to the modified example includes, for example, a debris flow control foundation work 10, a covering work 12, a beam member 40, and a steel erosion control structure member (superstructure) 50 having a frame structure made of steel pipes or H-shaped steel. The debris-flow countermeasure structure 1 according to the modified example differs from the debris-flow countermeasure structure 1 according to the first embodiment in that the debris-flow countermeasure structure 1 according to the modified example includes a beam member 40, and a bracket (connecting portion) 20B is formed on the upper portion (upper side surface) of the support member 20. As the rest is similar to the first embodiment, the same reference numerals are used and the description will be omitted.

[0020] The first support member 21 and the second support member 22 are arranged in multiples in the width direction when viewed, for example, along the flow direction of the debris flow, and the upper parts (upper side surfaces) of the first support member 21 and the second support member 22 are formed with substantially L-shaped brackets (connecting parts) 21B, 22B for connecting the beam member 40. The brackets (connecting parts) 21B, 22B are attached, for example, by welding or bolts. Note that the connecting parts 21B, 22B are not limited to the brackets (connecting parts) 21B, 22B, and may be arbitrarily set to flanges, plates, fastening structures, or the like.

[0021] The beam member 40 is made, for example, of an H-shaped steel, and connects, in a substantially horizontal direction, connecting portions 21A formed on the upper portions of a plurality of first support members 21 to connecting portions 22A formed on the upper portions of second support members 22 arranged downstream corresponding to each of the first support members 21, so that the first support members 21 and the second support members 22 are integrally formed, thereby improving strength in the upstream and downstream directions.

[0022] Next, a method for constructing debris flow countermeasure works according to one embodiment will be described with reference to Figs. FIG. 5 is a diagram for explaining an outline of a method for constructing debris flow countermeasures according to one embodiment, and FIG. 6 is a diagram for explaining an outline of constructing a plurality of debris flow countermeasure structures.

[0023] First, a method for constructing new debris flow countermeasure works in a set section will be described with reference to FIG. (1) Formation of block-shaped improved ground in the designated area When constructing a debris flow prevention structure on soft ground deposited in a waterless stream (small stream), etc., a section is set for forming the debris flow prevention work foundation, and then, as shown in Figure 5 (A), a backhoe T is used to excavate foundation work holes M in the set section to form block-shaped ground improvement work that is approximately rectangular in plan view. Specifically, the block sections (areas) divided on the construction site plane are excavated to a predetermined depth. It is preferable to excavate to a depth of 0.5 m to 5.0 m in one go.

[0024] (2) Generate muddy improved soil in the foundation hole Next, the base material including the excavated local soil and sand and cement milk or cement and water are poured into the foundation hole M, and the base material and cement milk or cement and water are stirred and mixed using a backhoe T or a backhoe T equipped with a mixing bucket to produce a muddy improved soil 11A. This ground improvement method can be carried out if a backhoe T can enter the site. The cement milk can be supplied to the construction site by a grout pump from a nearby slurry plant, or by transporting cement in bags to the site with a backhoe T and pumping it up from a water tank installed nearby. This makes it possible to carry out construction work even in mountain streams where construction roads cannot be secured. In addition, in the block-shaped ground improvement method involving excavation of a rectangular shape in plan view, the process of temporarily digging up the target area removes underground obstacles such as gravel during the process, making it easier to insert H-shaped steel or steel pipes, and preventing the water from being stuck high due to underground obstacles, making it possible to drive the support members with high precision. The excavated soil is dumped to a thickness of, for example, about 1.0 m to 1.5 m, and then cement milk or cement and water corresponding to the amount of soil is dumped, stirred, and kneaded to form a muddy improved ground 11. The thickness of the soil to be dumped may be set arbitrarily. Then, as shown in Fig. 5(C), this process is repeated to form improved ground 11. The consistency of the muddy improved ground is controlled by cylinder flow, and is preferably in the range of 83mm to 150mm.

[0025] (3) Insertion and plumbing of support members Next, as shown in Figure 5 (D), a predetermined amount of muddy improved soil 11A is generated in the foundation hole M, and an accumulation 11B of the muddy improved soil 11A is formed. Then, multiple support members 20 are inserted into the accumulation 11B of the muddy improved soil 11A, erected, and solidified to form the debris flow prevention work foundation 10. As a result, the improved ground 11 and the H-shaped steel that constitutes the support member 20 are integrated. In addition, when constructing a debris flow prevention work foundation 10 without the support members 20 erected, the insertion and erection of the support members described above is omitted.

[0026] (4) Connection of the superstructure 5(E), it is possible to connect the superstructure 50 by installing a flange or plate on the top (upper end) of the inserted support member 20. The H-shaped steel or steel pipes constituting the support member 20 integrated with the superstructure 50 in this way are integrated with the solidified improved ground 11 to support the load of moving soil and sand, making it possible to build a reliable foundation for a small-scale stream structure even on soft ground. When constructing a plurality of debris flow countermeasure structures 1, the superstructures 50 may be connected together.

[0027] Next, with reference to FIG. 6, an outline of construction of a plurality of debris flow countermeasure structures will be described. (1) Set up multiple sections for excavating foundation holes. (2) Next, construct the foundation for the debris flow prevention work in one of the sections using the above procedure. (3) As shown in FIG. 6(A), for example, a foundation hole M is excavated in a section adjacent to one of the sections constructed in (2). It may be decided at will whether or not the new foundation holes should be adjacent to existing debris flow prevention structures. (4) Next, as shown in FIG. 6(B), muddy improved soil 11A is generated in the foundation hole M. (5) As shown in FIG. 6(C), the procedure shown in (4) above is repeated to form an accumulation 11B by accumulating a predetermined amount of muddy improved soil 11A to form an improved ground in the foundation hole M. (6) Next, as shown in FIG. 6(D), a predetermined amount of improved muddy soil 11A is generated in the foundation hole to form an accumulation mass 11B. Once the soil has solidified to a hardness suitable for inserting and erecting the support members 20, multiple support members 20 are inserted into the improved muddy ground 11, erected, and solidified to form the debris flow prevention work foundation 10.

[0028] According to one embodiment of the debris flow control structure and debris flow control construction method, the quality is less affected by changes in soil quality even in soft ground, and construction is less affected by obstacles such as boulders, ensuring long-term durability and high reliability. In addition, the foundation work 10, which is made up of the improved ground 11, the first support member 21, and the H-shaped steel that constitutes the second support member 22, is connected to a non-flowing stream (small-scale stream) debris flow prevention structure 1, such as a member (superstructure) 50 of a steel sand control structure with a frame structure made of steel pipes or H-shaped steel, and is integrated with the foundation work 10 to resist the external forces of debris flows and collapsing soil.The improved ground 11, whose strength has been increased by being mixed with cement milk or cement and water, reinforces the stress acting on the H-shaped steel or steel pipe and provides long-term durability. Furthermore, the H-shaped steel or steel pipes integrated with the superstructure in this way support the load of moving soil and sand together with the solidified improved ground. This makes it possible to build a highly reliable foundation for debris flow prevention work for small-scale mountain stream structures even on soft ground. Furthermore, as in the modified example, by connecting the first support member 21 and the second support member 22 in the upstream and downstream directions by a beam member 40, it is possible to construct a debris flow prevention work foundation 10 in which the improved ground 11, the first support member 21, and the second support member 22 are further strengthened as a single unit.

[0029] The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above embodiment, a case has been described in which the debris flow countermeasure structure 1 (1A, 1B, 1C, 1D, 1E) is provided with a debris flow countermeasure foundation work 10 having a support member 20, but it is possible to set whether or not to have the support member 20, and the debris flow countermeasure structure 1 may also have no support member 20 inserted. In this case, the component (superstructure) 50 of the steel sand control structure having a frame structure made of steel pipes or H-shaped steel can be fixed to the debris flow prevention work foundation 10 with anchors or the like to prevent rotation (falling) or sliding of the component (superstructure) 50 of the steel sand control structure having a frame structure made of steel pipes or H-shaped steel. Furthermore, when the debris-flow control structure 1 comprises multiple debris-flow control structures, the debris-flow control structures with and without support members 20 may be arranged arbitrarily, and the debris-flow control structure may be constructed from a single improved ground.

[0030] In addition, in the above embodiment, the debris flow control work structure and the debris flow control work construction method have been described as being applied to a non-flowing stream (small-scale stream). However, the debris flow control work structure and the debris flow control work construction method may also be applied to emergency countermeasures in the event of a landslide on soft ground or ground with insufficient bearing capacity, or to erosion control facilities that require stability against support, sliding, and tipping in the ground.

[0031] In the above embodiment, the support members to be driven into the improved ground are composed of the first support member 21 and the second support member 22 made of H-shaped steel. However, the arrangement and configuration of the support members 20 (21, 22) may be set arbitrarily. For example, the configuration may include only the first support member 21, or the second support member 22 and the third and subsequent support members 20 positioned downstream in correspondence with the first support member 21 may be arranged. Furthermore, the support member 20 may be arranged at an arbitrary position not corresponding to the first support member 21 in the width direction when viewed along the flow of the debris flow. In addition, all or part of the first support member 21, the second support member 22, and the additionally arranged support member 20 may be made of other types of shaped steel, including steel pipes and channels.

[0032] In the above embodiment, the second support members 22 are arranged corresponding to all of the first support members 21, and all of the first support members 21 are connected to the corresponding second support members 22 by beam members 40 made of H-shaped steel. However, the arrangement and configuration of the beam members 40 may be set arbitrarily. For example, the configuration may be such that all or some of the first support members 21 are not connected to the second support members 22 by the beam members 40, or the first support members 21 may include beam members 40 arranged to connect to second support members 22 that do not correspond in the downstream direction (for example, in a cross-connected manner). Furthermore, all or some of the beam members 40 may be made of shaped steel other than H-shaped steel, such as steel pipes and channels.

[0033] In addition, in the above embodiment, the case where the backhoe T is used to excavate the foundation work holes and generate the muddy improved soil is described. However, the backhoe T is one example of an excavation means, and it goes without saying that the foundation work holes may be excavated by other excavation means, or the muddy improved soil 11A may be generated by other mixing means, etc. [Explanation of symbols]

[0034] G. Ground M Foundation hole T Backhoe 1, 1A, 1B, 1C, 1D, 1E Debris flow prevention structure 10 Foundation work for debris flow prevention works 11 Improved ground 11A Muddy improved soil 11B (mud-like improved soil) accumulation 20 Support member 21 First support member 22 Second support member 40 Beam member 50 Steel erosion control structure components (superstructure) made of steel pipes and H-shaped steel frames

Claims

1. The dam is constructed on a non-flowing stream or a small stream, and has an improved ground made of a base material containing locally generated soil and sand and a solidified body of improved soil made by mixing cement milk or cement and water in a foundation hole formed by excavating the ground, and is equipped with a debris flow countermeasure foundation on which a superstructure is placed. A debris flow prevention structure characterized by the above.

2. The foundation work for the debris flow countermeasure work is as follows: A plurality of support members are inserted and erected into the improved ground, The support member has a connecting portion formed at the upper portion thereof for connecting members of a steel erosion control structure having a frame structure made of steel pipes or H-shaped steel. The debris flow prevention structure according to claim 1.

3. The plurality of support members include A plurality of first support members arranged in a width direction when viewed along the flow of the debris flow; A plurality of second support members arranged downstream in the flow direction of the debris flow corresponding to the first support members; Equipped with The debris flow prevention structure according to claim 2.

4. A beam member is provided to connect the first support member and the second support member. The debris flow prevention structure according to claim 3.

5. A member of a steel erosion control structure having a frame structure made of steel pipes or H-shaped steel, which is a superstructure, is connected to the upper part of the support member. The debris flow prevention structure according to any one of claims 1 to 4.

6. Excavate the site where the debris flow prevention structure is to be constructed, located in a non-flowing stream or a small stream, to form a foundation hole, A base material containing on-site generated soil and sand and cement milk or cement and water are poured into the foundation hole, and stirred to generate muddy improved soil in the foundation hole; The muddy improved soil is solidified to form an improved ground consisting of a solidified muddy improved soil, and a foundation for a debris flow countermeasure work is constructed. A method for constructing debris flow countermeasures.

7. When a predetermined amount of muddy improved soil is produced in the foundation hole, a plurality of support members are inserted into the muddy improved soil, and then the muddy improved soil is solidified to form an improved ground with the support members erected thereon, thereby constructing the foundation for the debris flow countermeasure work. The method for constructing debris flow prevention works according to claim 6.

8. A method for constructing a debris flow countermeasure structure having a plurality of debris flow countermeasure foundation works, comprising: A plurality of sections are set for excavating the foundation hole, A foundation structure for a debris flow countermeasure construction according to claim 6 or 7 is formed in any one of the sections, After forming one debris flow countermeasure foundation, a foundation hole is formed in another section, and the debris flow countermeasure foundations are constructed in sequence. A method for constructing debris flow countermeasures.

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