Earth retention method

Abstract

This invention provides a retaining wall construction method that offers higher construction efficiency, lower environmental impact, and lower construction costs compared to conventional technologies. [Solution] The earth retaining method of the present invention comprises a pressing step S1 in which a plurality of main piles 10 are rotated and pressed into the ground at predetermined intervals along the excavation line C, an excavation step S3 in which the ground in front of the excavation line C is excavated to the excavation bottom A to expose the excavation wall B, and an earth retaining step S4 in which an earth retaining plate 30 is inserted from above between two adjacent main piles 10 to shield the excavation wall B, wherein the main pile 10 comprises a circular steel pipe 11, four flanges 12 provided along the longitudinal direction on the upper part of the circular steel pipe 11, the four flanges 12 located on two sides of the circular steel pipe 11, with the front and rear two flanges 12 on each side being parallel to each other, and two guide grooves 12a drawn between each front and rear two flanges 12, and in the earth retaining step S4, the side edge of the earth retaining plate 30 is held between the guide grooves 12a of adjacent main piles 10.

Description

Technical Field

[0004] , , , , , , , , ,

[0001] The present invention relates to a soil retaining method, and particularly to a soil retaining method with high construction efficiency, low environmental impact, and low construction cost compared to the prior art.

Background Art

[0002] In new construction of houses, when constructing the foundation of a building, the ground is excavated to dig down the site. When excavating the ground, soil retaining work is carried out to prevent the backfill soil from collapsing towards the construction site side due to soil pressure. As a conventional technique related to soil retaining work, the parent pile cross bracing method of sandwiching a cross bracing such as a cedar board between the flanges of H-shaped steel is widely known (Patent Document 1). In the parent pile cross bracing method, first, the ground is pre-excavated with an earth auger, an H-shaped steel is inserted into the hole, and mortar is filled into the gap to fix the H-shaped steel to the ground. Next, while excavating the ground on the construction site side to form an excavation wall surface, the excavation wall surface is dug deeper on the back side than the H-shaped steel so that the cross bracing can enter between the H-shaped steels. Finally, the cross bracing is dropped into the flange of the H-shaped steel, and sand is backfilled into the gap between the excavation wall surface and the back of the cross bracing to prevent the collapse of the excavation wall surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The prior art of Patent Document 1 has the following problems. <1>Since the H-shaped steel is fixed to the ground with mortar, it is difficult to pull out and remove the H-shaped steel from the ground after the foundation construction of the building, and it takes a large cost and a long construction period for the removal. <2> Because removing H-beams is difficult, they are often left buried and left in place. In this case, the H-beams and mortar remain underground, significantly reducing the economic value of the land. Furthermore, the use of disposable temporary materials creates an environmental burden, and the cost of replacing the temporary materials increases. <3> When H-beams or similar structures are left buried in the ground, the wooden sheet piles may rot in the soil at a depth shallower than the groundwater level, potentially creating a soft, organic soil base that compromises the soundness of the ground. <4> The initial excavation by the earth auger disturbs the ground, which may prevent the H-beams from securing sufficient horizontal force equivalent to the ground's strength. Furthermore, the initial excavation generates excavated soil, increasing disposal costs. <5> If the sand filling behind the sheet piles is insufficient, the excavation wall may bulge outwards towards the sheet piles due to earth pressure, potentially causing differential settlement of neighboring properties. <6> Because all work around the H-beams, such as deep excavation behind the H-beams in the excavation wall, dropping in sheet piles, and filling the back of the sheet piles with sand, is done manually, it places a heavy physical burden on the workers and results in poor construction efficiency. Furthermore, since the work is performed near the excavation wall, there are concerns about the safety of the workers (Figure 15).

[0005] The present invention aims to provide a soil retention method that solves the above-mentioned problems. [Means for solving the problem]

[0006] The earth retention method of the present invention comprises a pressing step of rotating and pressing a plurality of main piles into the ground at predetermined intervals along the excavation line, an excavation step of excavating the ground in front of the excavation line down to the bottom of the excavation to expose the excavation wall, and an earth retention step of inserting an earth retention plate from above between two adjacent main piles to shield the excavation wall. The main pile comprises a circular steel pipe, four flanges provided along the longitudinal direction at the top of the circular steel pipe, located on two sides of the circular steel pipe, with the front and rear two flanges on each side being substantially parallel to each other, and two guide grooves drawn between each front and rear two flanges. In the earth retention step, the side edge of the earth retention plate is held between the guide grooves of adjacent main piles.

[0007] The present invention relates to a method for constructing an earth retaining wall along an excavation line set in the ground, comprising: a pressing step of rotating and pressing a plurality of main piles into the ground at predetermined intervals along the excavation line; an excavation step of excavating the ground in front of the excavation line down to the bottom of the excavation to expose the excavation wall surface; and an earth retaining step of inserting an earth retaining plate from above between two adjacent main piles to shield the excavation wall surface, wherein the main pile comprises a circular steel pipe, an H-beam with its lower part inserted into the circular steel pipe and its upper part protruding above the circular steel pipe, four flanges of the H-beam, and two guide grooves drawn between each pair of flanges, and in the earth retaining step, the side edge of the earth retaining plate is held between the guide grooves of adjacent main piles.

[0008] In the earth retention method of the present invention, the earth retention plate is a rectangular metal plate, and in the earth retention process, the soil protruding in front of the excavation line may be cut off by inserting the earth retention plate.

[0009] In the earth retention method of the present invention, the earth retention plate may be inserted by pressing or striking it from above with heavy machinery during the earth retention process.

[0010] In the earth retention method of the present invention, the lower edge of the earth retention plate may have a single-edged cutting edge with an inclined surface facing the back side.

[0011] The earth retention method of the present invention includes an insertion step between the press-in step and the excavation step, in which a reinforcing core material is inserted into the circular steel pipe from above. The reinforcing core material consists of a rectangular steel plate that is elongated, and in the insertion step, the reinforcing core material may be inserted into the circular steel pipe in a orientation such that the long side of the reinforcing core material is perpendicular to the excavation line when viewed in plan with respect to the circular steel pipe.

[0012] The earth-retaining method of the present invention comprises a main pile equipped with a sheath pipe over a circular steel pipe, the sheath pipe having an opening through which the outer surface of the circular steel pipe is exposed, two front and rear flanges located on one side of the circular steel pipe extending outward from the outer surface of the sheath pipe, and two front and rear flanges located on the other side of the circular steel pipe extending outward from the outer surface of the circular steel pipe through the opening, thereby allowing the angle of the two front and rear flanges on one side to be changed relative to the two front and rear flanges on the other side.

[0013] The earth retention method of the present invention includes a guide jig comprising a cylindrical guide tube that can be divided in the circumferential direction and a fixing pile that fixes the guide tube to the ground, and in the press-in process, the tip of a circular steel pipe may be placed inside the guide tube, and the main pile may be rotated and pressed into the ground while the circular steel pipe is guided by the guide tube. [Effects of the Invention]

[0014] Since the earth retention method of the present invention has the above configuration, it has at least one of the following effects. <1> Because the structure does not use mortar and instead involves pressing circular steel pipes into the ground for embedment, the circular steel pipes can be pulled out after the main structure is completed, and the retaining wall can be dismantled and removed. Therefore, there is no risk of damaging the economic value of the land by leaving temporary materials underground. In addition, by reusing temporary materials, replacement costs and carbon dioxide emissions from steel manufacturing can be reduced. <2> Because the circular steel pipe is driven in by rotation and press to create the foundation, there is no risk of disturbing the ground at the embedment point, unlike conventional earth auger technology, and it can secure horizontal force equivalent to that of the ground. In addition, since preliminary excavation is unnecessary, no excavated soil is generated, and there are no costs associated with disposing of excavated soil. <3> When using metal plates for retaining walls, heavy machinery can be used to push the plates between the flanges and cut away the excavation wall. This eliminates the need to pre-excavate the back of the excavation wall, resulting in high construction efficiency. Furthermore, because gaps are less likely to form between the retaining plates and the excavation wall, there is less risk of causing differential settlement or other problems to neighboring properties. <4>When using a metal plate for the earth retaining plate, almost all processes can be carried out by heavy machinery, so the physical burden on workers is small and the work safety is high.

Brief Description of Drawings

[0015] [Figure 1] Flow Chart of the Earth Retaining Method of the Present Invention [Figure 2] Explanation Diagram of Earth Retaining Wall [Figure 3] Explanation Diagram of Main Piles and Reinforcing Core Materials [Figure 4] Explanation Diagram of Flange [Figure 5] Explanation Diagram of Press-Fitting Process [Figure 6] Explanation Diagram of Excavation Process [Figure 7] Explanation Diagram of Earth Retaining Process [Figure 8] Explanation Diagram of Example 2 [Figure 9] Explanation Diagram of Example 3 (1) [Figure 10] Explanation Diagram of Example 3 (2) [Figure 11] Explanation Diagram of Example 4 [Figure 12] Explanation Diagram of Example 5 [Figure 13] Explanation Diagram of Examples 4 and 5 [Figure 14] Explanation Diagram of Example 6 [Figure 15] Explanation Diagram of Prior Art

Modes for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, "excavation bottom surface" means the bottom surface dug deeper than the adjacent ground by ground excavation, "excavation wall surface" means the side surface exposed by ground excavation, and "excavation line" means the virtual line planned to excavate the ground in plan view. Also, "front" and "front surface" mean the construction site side (i.e., the excavation bottom surface side) for housing foundation work etc. with respect to the excavation line, and "rear" and "back surface" mean the opposite side of the front surface (i.e., the adjacent ground side).

Examples

[0017] <1> Earth retention method (Figure 1) The earth retention method of the present invention is a method for constructing an earth retention wall 1 that covers the excavation wall surface B in construction work in which the ground is excavated to an excavation bottom A that is lower than the adjacent land. The earth retention method comprises at least a press-in step S1, an excavation step S3, and an earth retention step S4. In this example, it further comprises an insertion step S2 and a removal step S5. The earth retention method of the present invention is characterized by a configuration in which a main pile 10, which has a flange 12 on its upper part, is rotated and pressed into the ground, thereby facilitating the excavation of the ground by stirring up the flange 12, while ensuring the vertical bearing capacity of the earth retention wall 1 by the circumferential frictional force of the embedded portion of the main pile 10.

[0018] <2> Retaining wall (Figure 2) Retaining wall 1 is a temporary structure that supports the excavated wall surface B and prevents its collapse. The retaining wall 1 comprises at least a plurality of main piles 10 embedded in the ground along the excavation line C, and retaining plates 30 inserted between the flanges 12 of adjacent main piles 10 to support the front surface of the excavation wall B. In this example, it further comprises reinforcing core materials 20 inserted into the main piles 10.

[0019] <2.1> Main pile (Figure 3) The main pile 10 is a member that is embedded in the ground and supports the retaining wall plate 30. The main pile 10 comprises at least a circular steel pipe 11 and four flanges 12 provided on the upper side of the circular steel pipe 11. In this example, the main pile 10 is formed by connecting two circular steel pipes 11 longitudinally with a joint 13. A mounting bracket (not shown) for a rotary press-fitting device is attached to the top of the circular steel pipe 11. The tip of the circular steel pipe 11 may be provided with a claw-like projection to facilitate excavation. The structure of the main pile 10 is not limited to the above; for example, it may be a single piece without a joint 13.

[0020] <2.1.1> Flange (Figure 4) The flange 12 is a member that guides and holds the side edge of the earth retaining plate 30. Four flanges 12 are provided on the outer surface of the circular steel pipe 11, along the longitudinal direction. The four flanges 12 are positioned on two opposing sides of the outer surface of the circular steel pipe 11, and in this example, the two flanges 12 attached to the same side are approximately parallel to each other (Figure 4(a)). As a result, two flanges 12 are evenly distributed on each side of the outer surface of the circular steel pipe 11. However, the arrangement of the flanges 12 is not limited to this; the two flanges 12 may be connected at any angle, such as an inner angle of 60° (Figure 4(b)) or an inner angle of 90° (Figure 4(c)), to correspond to the curves of the excavation line C. A guide groove 12a is provided between the two nearly parallel flanges 12 to accommodate the side edge of the earth retaining plate 30.

[0021] <2.1.2> Joint The joint 13 is a component for connecting the circular steel pipes 11 in the longitudinal direction. In this example, a ring-shaped joint 13 is used, which has grooves on its outer circumference that can engage with the inside of the end of the circular steel pipe 11. A through hole is provided in the center of the joint 13, through which a reinforcing core material 20 can be passed. However, the structure of joint 13 is not limited to the above, and may be a mechanical joint such as a bolt type, key type, or screw type.

[0022] <2.2> Reinforcement core material (Figure 3) The reinforcing core material 20 is a member that reinforces the main pile 10 from the inside. The reinforcing core material 20 is inserted into the circular steel pipe 11 of the main pile 10, and has an elongated shape that allows it to reinforce the circular steel pipe 11 from the inside. In this example, a rectangular steel plate with a suspension hole at the top is used as the reinforcing core material 20. However, the structure of the reinforcing core material 20 is not limited to the above; it may also be an angle material or steel pipe that can be installed inside the circular steel pipe 11.

[0023] <2.3> Retaining board The retaining plate 30 is a member that supports the earth pressure on the excavation wall B. The retaining plate 30 is held between the flanges 12 of adjacent main piles 10. The retaining wall plate 30 comprises a rectangular plate body 31 with a width corresponding to the spacing between adjacent main piles 10. In this example, the plate body 31 is made of a rectangular, vertically elongated metal plate, and a cut edge 32 is provided at the bottom of the plate body 31. The earth retention method of the present invention is a method that reuses the board body 31 without burying it permanently. By making the board body 31 a metal plate which is more durable than a cedar board, it can be reused repeatedly and can be constructed at a lower cost compared to conventional methods in which cedar boards are permanently buried. Furthermore, the retaining board 30 is not limited to a single piece, but may be a combination of multiple board bodies 31 arranged vertically. Also, the retaining board 30 is not limited to metal, but may be made of wood, resin, or the like.

[0024] <2.3.1> Cutting edge The cutting edge 32 is the part used to scrape away the soil from the excavation wall B. The cutting edge 32 is formed by creating a single-edged shape at the lower edge of the plate body 31. More specifically, at the lower edge of the plate body 31, the corner on one side is formed at an angle to create a single-edged shape with an inclined surface facing that side. Furthermore, if the retaining wall 30 is made up of a combination of multiple plate bodies 31, the cut edge 32 only needs to be provided on the bottom plate body 31.

[0025] <3> Press-fitting process (Figure 5) The pressing-in process S1 is the process of pressing the main pile 10 into the ground. The pressing-in process S1 can be carried out, for example, as follows. The main pile 10 is driven into the ground. A rotary driving device for steel pipe piles is used to drive the main pile 10 into the ground while rotating it around its axis. Since a flange 12 is attached to the outer circumference of the upper part of the main pile 10, the upper part of the ground (shallower than the excavation bottom A) is stirred and disturbed by the rotating flange 12, but since there is no flange 12 in the lower part of the ground (deeper than the excavation bottom A), sufficient circumferential frictional force acts between the ground and the outer surface of the circular steel pipe 11. Following a similar procedure, the main piles 10 are driven into the ground along the excavation line C at predetermined intervals corresponding to the width of the retaining plate 30.

[0026] <4> Insertion process Insertion step S2 is the process of inserting the reinforcing core material 20 into the main pile 10. Insertion step S2 can be carried out, for example, as follows. The reinforcing core material 20 is lifted by a crane and inserted into the main pile 10. At this time, in a plan view of the circular steel pipe 11, the reinforcing core material 20 is inserted so that its long side is perpendicular to the excavation line C. The reinforcing core material 20 is inserted into the main pile 10 to a position that crosses the depth of the excavation bottom A. Using a similar procedure, reinforcing core material 20 is inserted into all of the main piles 10.

[0027] <5> Excavation process (Figure 6) The excavation process S3 is the process of excavating the ground. The excavation process S3 can be carried out, for example, as follows. Using heavy machinery such as a backhoe, excavate the ground in front of the excavation line C to the depth of the excavation bottom A. In the earth retention method of the present invention, the ground around the main pile 10 in the portion shallower than the excavation bottom A is stirred and loosened by the flange 12 during the press-in process S1, making it easier to excavate along the excavation line C and resulting in high work efficiency.

[0028] <6> Earth retention process (Figure 7) The earth retention process S4 is the process of shielding the excavation wall B with earth retention plates 30. The earth retention process S4 can be carried out, for example, as follows. The retaining plate 30 is lifted by a crane and its lower edge is inserted between the guide grooves 12a of adjacent main piles 10. Subsequently, the retaining plate 30 is lowered along the guide grooves 12a to the bottom of the excavation A, thereby shielding the front of the excavation wall B with the retaining plate 30. In this example, since the plate body 31 of the retaining plate 30 is made of metal, the retaining plate 30 can be pushed down from above using heavy machinery such as a backhoe. Therefore, even if the excavation wall B protrudes in front of the excavation line C, the lower edge of the retaining plate 30 can scrape away the protruding soil and push it down to the bottom of the excavation A. Therefore, unlike conventional techniques, there is no need to excavate the excavation wall B deeper behind the excavation line C, resulting in higher work efficiency. In addition, since gaps are less likely to form between the retaining plate 30 and the excavation wall B, there is less risk of causing differential settlement or other effects on nearby ground.

[0029] <6.1> Function of the cutting edge In this example, since the retaining plate 30 is equipped with a cutting edge 32 on the lower edge of the plate body 31, it is easy to remove soil that protrudes in front of the excavation line C. Furthermore, by orienting the inclined surface of the cutting edge 32 toward the back side of the excavation line C, the retaining plate 30 is guided to follow the front flange 12 within the guide groove 12a as it is pushed downward. This makes it easier to position the retaining plate 30 within the guide groove 12a.

[0030] <7> Removal process The removal process S5 is the process of dismantling and removing the retaining wall 1 after constructing a structure on the excavation bottom A. The removal process S5 can be carried out, for example, as follows. The retaining board 30 is lifted by a crane and pulled out from between the main piles 10. The reinforcing core material 20 is lifted by a crane and extracted from inside the main pile 10. The head of the main pile 10 is chucked with a rotary press-in device, and the main pile 10 is rotated in the opposite direction to cut its connection with the ground while being pulled out. Finally, the space between the exposed excavation wall B and the structure is backfilled with good quality soil. Repeat the same procedure along the excavation line C, every two to three main piles 10. However, the order of the removal process S5 is not limited to the above. For example, the reinforcing core material 20 may be removed from inside the main pile 10 first, and then the retaining plate 30 may be removed. [Examples]

[0031] [Example where the main pile is of the H-beam type] In this example, the main pile 10 consists of a combination of a circular steel pipe 11 and an H-beam 15. In detail, the main pile 10 is manufactured by inserting the lower part of the H-beam 15 into the circular steel pipe 11 and welding the two together with the upper part of the H-beam 15 protruding above the circular steel pipe 11. In the press-fitting process S1, the flange 12 of the H-beam 15 is gripped and the main pile 10 is rotated and press-fitted. In the earth retention process S4, the earth retention plate 30 is inserted between the guide grooves 12a of the flange 12 of the H-beam 15 and pushed down from above (Figure 8). In this example, the structure of the main pile 10 is simplified, which reduces the cost of procuring materials. [Examples]

[0032] [Example of a main pile of the adjustable type] In this example, the main pile 10 is of a flexible type in which the angle between the flanges 12 can be arbitrarily changed. The main pile 10 is equipped with a sheath pipe 14 that is fitted over a circular steel pipe 11 (Figure 9). The sheath pipe 14 comprises a plurality of cylindrical portions 14a that cover the outer surface of the circular steel pipe 11, and openings 14b between the plurality of cylindrical portions 14a in which the outer surface of the circular steel pipe 11 is exposed. In detail, the sides of the plurality of cylindrical portions 14a arranged along the longitudinal direction of the circular steel pipe 11 are connected longitudinally by two flanges 12, and openings 14b are provided between adjacent cylindrical portions 14a in the longitudinal direction. From multiple openings 14b arranged in the longitudinal direction, two flanges 12, one at the front and one at the back, are provided on the outer surface of the circular steel pipe 11, extending outward. With the above structure, the angle of the two flanges 12 provided on the cylindrical portion 14a can be changed with respect to the two flanges 12 provided on the outer surface of the circular steel pipe 11 and extending from the opening 14b. In this example, even if the excavation line C is curved to match the shape of the land, it is possible to install the retaining wall 1 along the excavation line C by adjusting the angle between the flanges 12 (Figure 10). [Examples]

[0033] [Example using a guide jig] In this example, a guide jig 40 is used in the press-fitting process S1. The guide jig 40 is a component that guides the driving of the main pile 10 into the ground. The guide jig 40 includes at least one guide cylinder 41 corresponding to the outer diameter of the circular steel pipe 11. In this example, the guide jig 40 consists of a combination of two guide cylinders 41 divided in the circumferential direction, fixing cylinders 42 attached to both ends of each guide cylinder 41, and two fixing stakes 43 that can be inserted into the fixing cylinders 42 (Figure 11). By shifting the positions of the two fixed cylinders 42 of each guide cylinder 41 in the height direction, it becomes possible to construct a guide jig 40 by combining members of the same shape. In the press-in process S1, if the main pile 10 is rotated and pressed in using a device without a leader, such as a pole erection vehicle, there is a risk that the main pile 10 may become misaligned due to underground obstacles or uneven ground conditions. In this example, when the main pile 10 is driven in by rotation, the outer circumference of the circular steel pipe 11 is guided by a guide jig 40 fixed to the ground by a fixed pile 43, thereby preventing misalignment and ensuring the verticality of the main pile 10 (Figure 13). Furthermore, since the guide jig 40 interferes with the flange 12 of the main pile 10, it is disassembled and removed once the tip of the circular steel pipe 11 has been pressed into the ground. [Examples]

[0034] [Example using a linked guide jig] In this example, a linked-type guide jig 40 is used. The guide jig 40 consists of a combination of two guide tubes 41 divided in the circumferential direction, fixing pieces 44 attached to each guide tube 41, a long ruler material 45, and a plurality of fixing stakes 43 (Figure 12). The guide material 45 is, for example, a shaped steel such as an H-beam, and is equipped with bolt holes in the flange through which fixing pieces 44 can be bolted, and through holes in the web through which fixing piles 43 can be inserted. By shifting the position of the fixing pieces 44 attached to each guide cylinder 41 in the height direction, it becomes possible to construct a guide jig 40 by combining members of the same shape. In this example, bolt holes are arranged at predetermined intervals corresponding to the press-in intervals of the main piles 10, and the main piles 10 are pressed in while the guide cylinder 41 is moved along the ruler material 45, making it possible to accurately press-in the main piles 10 along the excavation line C (Figure 13). [Examples]

[0035] [Example using a pressing jig] In this example, a pressing jig 50 for the retaining board 30 is used. The pushing jig 50 consists of a gripping part 51 and a receiving part 52 provided on the upper part of the gripping part 51 (Figure 14). The gripping portion 51 is equipped with a gripping groove at its lower part that can engage with the upper edge of the retaining plate 30. The receiving section 52 is equipped with a receiving hole at its upper part that can be struck with a breaker or the like of heavy machinery. In this example, during the earth retention process S4, the gripping part 51 of the pushing jig 50 is engaged with the upper edge of the earth retention plate 30, and the receiving part 52 is struck with a breaker attached to the bucket of the backhoe, thereby pushing the earth retention plate 30 down from above. This makes it possible to easily push the earth retention plate 30 down even if the soil is protruding in clumps in front of the excavation line C. [Explanation of Symbols]

[0036] 1. Retaining wall 10 Main stake 11 Circular steel pipes 12 flanges 12a Guide groove 13 joints 14 Sheathed tube 14a Cylindrical section 14b opening 15H steel 20 Reinforcement core material 21 Core material body 22 Hanging holes 30 retaining boards 31 Main body 32 Cutting edge 40 Guide fixtures 41 Guide tube 42 Fixed tube 43 Fixed pile 44 Fixed piece 45 Ruler material 50 Pressing jig A. Bottom of the excavation B Excavation wall C Excavation Line S1 Press-fitting process S2 insertion process S3 Excavation Process S4 Earth retaining process S5 Removal process

Claims

1. A retaining wall construction method for building a retaining wall along an excavation line set in the ground, A pressing process in which multiple main piles are rotated and pressed into the ground at predetermined intervals along the aforementioned excavation line, The excavation process involves excavating the ground in front of the aforementioned excavation line down to the bottom of the excavation to expose the excavation wall, The process includes a retaining step of inserting a retaining plate from above between two adjacent main piles to shield the excavated wall surface, The main pile comprises a circular steel pipe, four flanges provided along the longitudinal direction at the upper part of the circular steel pipe, the four flanges located on two sides of the circular steel pipe, with the front and rear two flanges on each side being substantially parallel to each other, and two guide grooves drawn between each of the front and rear two flanges. In the earth retention process, the side edge of the earth retention plate is held between the guide grooves of adjacent main piles, Earth retention method.

2. A retaining wall construction method for building a retaining wall along an excavation line set in the ground, A pressing process in which multiple main piles are rotated and pressed into the ground at predetermined intervals along the aforementioned excavation line, The excavation process involves excavating the ground in front of the aforementioned excavation line down to the bottom of the excavation to expose the excavation wall, The process includes a retaining step of inserting a retaining plate from above between two adjacent main piles to shield the excavated wall surface, The main pile comprises a circular steel pipe, an H-beam with its lower part inserted into the circular steel pipe and its upper part protruding above the circular steel pipe, four flanges of the H-beam, and two guide grooves drawn between each pair of flanges. In the earth retention process, the side edge of the earth retention plate is held between the guide grooves of adjacent main piles, Earth retention method.

3. The earth retaining plate is a rectangular metal plate, In the aforementioned earth retention process, the soil protruding in front of the excavation line is cut off by inserting an earth retention plate. The earth retention method according to claim 1 or 2.

4. In the earth retention process, the earth retention plate is inserted by pressing or striking it from above with heavy machinery. The earth retention method according to claim 3.

5. The lower edge of the earth retaining plate is characterized by having a single-edged cutting edge with an inclined surface facing the back side. The earth retention method according to claim 4.

6. Between the press-in step and the excavation step, there is an insertion step in which a reinforcing core material is inserted into the interior of the circular steel pipe from above. The reinforcing core material consists of a rectangular steel plate that is elongated in shape. In the insertion step, the reinforcing core material is inserted into the circular steel pipe such that, in a plan view of the circular steel pipe, the long side of the reinforcing core material is perpendicular to the excavation line. The earth retention method according to claim 1.

7. The main pile is equipped with a sheath pipe that is attached to the circular steel pipe, The sheath tube has an opening through which the outer surface of the circular steel pipe is exposed. The two front and rear flanges located on one side of the circular steel pipe extend outward from the outer circumferential surface of the sheath pipe, and the two front and rear flanges located on the other side of the circular steel pipe extend outward from the outer circumferential surface of the circular steel pipe through the opening, thereby allowing the angle of one set of front and rear flanges to be changed relative to the other set of front and rear flanges. The earth retention method according to claim 1.

8. The guide jig comprises a cylindrical guide tube that can be divided in the circumferential direction, and a fixing pile for fixing the guide tube to the ground. In the aforementioned press-in process, the tip of the circular steel pipe is placed inside the guide cylinder, and the main pile is rotated and pressed into the ground while the circular steel pipe is guided by the guide cylinder. The earth retention method according to claim 1.

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