geotechnical structures

Abstract

The present invention provides an earthwork structure in which the panel members are less likely to detach from the main piles even when subjected to external forces. [Solution] A retaining wall structure 1 (a type of earthwork structure) comprising a retaining wall panel 3 (a type of panel member) made of a core material composed of a plate-shaped member made of foamed resin and a urea layer made of urea resin that covers the surface of the core material, and main piles 2 driven into the ground and supporting the left and right ends of the retaining wall panel 3, wherein the retaining wall panel 3 is plate-shaped with an arc curve between the left and right ends, and is supported by the main piles 2 such that the left and right central parts bulge out more towards the slope SL side (the side on which external forces act) than the left and right ends.

Description

Technical Field

[0001] The present invention relates to geotechnical structures such as earth retaining structures, rockfall protection fences, and temporary protection fences.

Background Art

[0002] Geotechnical structures are known that are provided on protected areas such as mountain slopes, slopes, and excavated areas of the ground in order to suppress the collapse and outflow of earth and sand and to receive rockfalls. As a geotechnical structure, for example, one is known that is composed of a parent pile made of H-shaped steel or the like and driven into the ground at a predetermined interval, and a rectangular plate-shaped panel member whose left and right ends are supported by the parent pile.

[0003] Patent Document 1 discloses a plate-like body for civil engineering and architecture that can be used as a panel member, in which the surface of a core material made of a foamed resin is coated with a cement-based liquid and non-woven paper. Patent Document 2 discloses a waterproof sheet that can be used as a panel member for preventing water from flowing into a building or underground, etc., in which the surface of a core material made of a foamed resin is coated with a polyurethane resin.

[0004] [[ID=A]] By combining the technologies described in Patent Document 1 and Patent Document 2, a panel member in which the surface of a core material composed of a flat plate made of a foamed resin is coated with a polyurethane resin is envisioned. This panel member is installed on a protected area using, for example, a parent pile made of H-shaped steel. However, when a geotechnical structure is constituted by this panel member and the parent pile, when the panel member receives earth pressure from the protected area or receives a rockfall, the panel member may bend due to an external force (impact due to earth pressure or rock collision) and come off the parent pile.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] This invention has been made in view of the above circumstances, and aims to provide an earthwork structure in which the panel members are less likely to detach from the main piles even when subjected to external forces. [Means for solving the problem]

[0007] To solve the above problems, the invention described in claim 1 is an earthwork structure comprising a core material made of a plate-shaped member made of foamed resin, and a panel member having a urea layer made of a resin containing urea bonds that covers the surface of the core material, and main piles that are driven into the ground and support the left and right ends of the earth retaining panel, wherein the panel member is plate-shaped with an arc curve between the left and right ends, and is supported by the main piles such that the left and right central portions bulge out towards the surface of external force application more than the left and right ends. [Effects of the Invention]

[0008] According to this invention, it is possible to provide an earthwork structure in which the panel members are less likely to detach from the main piles even when subjected to external forces. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a retaining wall structure according to the first embodiment, installed on a sloping site. [Figure 2] (a) is a perspective view of the earth retaining panel according to the first embodiment, (b) is an enlarged view showing a partially cut-out corner of the earth retaining panel according to the first embodiment, and (c) is a front view of the earth retaining structure according to the first embodiment. [Figure 3] (a) is a view from above of a part of the earth retaining structure according to the first embodiment, and (b) is an enlarged view of the area near the main pile. [Figure 4](a) is a diagram schematically illustrating the deformation of the retaining wall panel, (b) is a diagram illustrating the gap formed between the groove of the main pile and the retaining wall panel due to the deformation, and (c) is a diagram illustrating the state in which some of the soil has flowed into the formed gap. [Figure 5] (a) is a diagram illustrating the spraying process of spraying urea resin onto the surface of the core material, and (b) is a diagram illustrating the urea resin spraying apparatus. [Figure 6] Figures (a) through (h) show modified examples of earth retaining panels with different thicknesses and curvatures. [Figure 7] (a) is a perspective view showing a retaining wall panel according to the second embodiment, (b) is a view from above of a part of the retaining wall structure according to the second embodiment, and (c) is a diagram illustrating the gap formed between the groove of the main pile and the retaining wall panel due to the deformation of the retaining wall panel according to the second embodiment. [Figure 8] (a) is a perspective view showing a retaining wall panel according to the third embodiment, (b) is a view from above of a part of the retaining wall structure according to the third embodiment, and (c) is a diagram illustrating the gap formed between the groove of the main pile and the retaining wall panel due to the deformation of the retaining wall panel according to the third embodiment. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below using the embodiments shown in the figures. However, unless otherwise specified, the components, types, combinations, shapes, and relative arrangements described in these embodiments are not intended to limit the scope of the present invention to these specific examples, but are merely illustrative examples.

[0011] [Summary of the present invention] First, I will explain the gist of the earthwork structure according to this invention. Figure 1 is a perspective view showing a retaining wall structure 1 according to the first embodiment, installed on a sloping site. Here, the retaining wall structure 1 is a type of earthwork structure according to the present invention. Earthwork structures include not only the retaining wall structure 1, but also rockfall protection fences, temporary protection fences, and the like. Fig. 2(a) is a perspective view of the retaining panel 3 according to the first embodiment, Fig. 2(b) is an enlarged view showing a partially cut-away corner portion of the retaining panel 3 indicated by reference numeral A in Fig. 2(a), and Fig. 2(c) is a front view of the retaining structure 1 according to the first embodiment. Here, the retaining panel 3 is a kind of panel member constituting a geotechnical structure. The panel members include, in addition to the retaining panel 3, rockfall protection panels and the like.

[0012] Fig. 3(a) is a view of a part of the retaining structure 1 according to the first embodiment as seen from above, and Fig. 3(b) is an enlarged view near the parent pile 2. Fig. 4(a) is a diagram schematically explaining the deformation of the retaining panel 3, Fig. 4(b) is a diagram explaining the gap SP formed between the groove portion 2RS of the parent pile 2 and the retaining panel 3 due to the deformation, and Fig. 4(c) is a diagram explaining the state in which a part of the earth and sand has flowed into the formed gap SP.

[0013] The retaining structure 1 illustrated in Fig. 1 is installed on the slope SL for the purpose of preventing the collapse and outflow of earth and sand. The slope SL is, for example, a mountain slope or a slope of a cliff, and is a kind of protected area where the collapse and outflow are suppressed by the retaining structure 1. The retaining structure 1 includes parent piles 2 arranged at predetermined intervals and driven into the ground G at the lower part, and retaining panels 3 supported at both left and right end portions by the parent piles 2. As shown in Fig. 2(a), the retaining panel 3 is configured in a plate shape with the left and right ends curved in an arc shape. And as shown in Fig. 2(b), the retaining panel 3 includes a core material 31 formed of a plate-like member made of foamed resin, and a urethane layer 32 formed of a resin containing urethane bonding (urethane resin) and covering the surface of the core material 31. As shown in Figs. 1 and 2(c), both left and right end portions of the retaining panel 3 are supported by a pair of parent piles 2, and are supported in a state where a plurality (for example, four) of retaining panels 3 are stacked. Also, as shown in Fig. 3(a), the retaining panel 3 is supported by the parent piles 2 such that the left and right central portions of the retaining panel 3 are located above the left and right end portions on the slope SL (that is, bulge toward the mountain side which is the side of the acting surface of the external force).

[0014] According to the earth retaining structure 1 having the above configuration, as shown in Fig. 4(a), when the earth retaining panel 3 receives the earth pressure EP (external force) from the sloping ground SL (the ground to be protected), the earth retaining panel 3 is compressed and deformed so as to approach a flat plate shape. Along with the compression and deformation of the earth retaining panel 3, the strength of the earth retaining panel 3 is improved, and it becomes difficult to bend below the sloping ground SL beyond the main pile 2. As a result, the earth retaining panel 3 is difficult to come off from the main pile 2. Similarly, in a rockfall protection fence using a rockfall protection panel having the same configuration as the earth retaining panel 3, when the rockfall protection panel receives a rockfall, the strength of the rockfall protection panel is improved, and it becomes difficult to bend below the sloping ground SL (valley side) beyond the main pile 2. As a result, the rockfall protection panel is difficult to come off from the main pile 2.

[0015] 〔First Embodiment〕 The earth retaining structure 1 according to the first embodiment of the present invention will be described in detail. As described above, the earth retaining structure 1 according to the first embodiment includes an earth retaining panel 3 and a main pile 2. Hereinafter, each member will be described.

[0016] <Earth Retaining Panel 3> The earth retaining panel 3 illustrated in Fig. 2(a) is a plate-like member having a horizontally long rectangular shape in a front view, and is curved in an arc shape between the left end and the right end in a plan view.

[0017] In the illustrated earth retaining panel 3, for example, the length in the left-right direction on the outer curved surface indicated by the reference sign W3 is about 2000 mm, the height H3 is about 500 mm, and the thickness D3 is about 100 mm, but is not limited to these dimensions. In the illustrated example, on the outer curved surface, the central point of the arc bulges about 100 mm outside the arc from both end points in the left-right direction (that is, the distance (curvature) indicated by the reference sign X3 is about 100 mm). As will be described later, the dimensions and curvature of each part of the earth retaining panel 3 can be appropriately determined according to the sloping ground SL where the earth retaining structure 1 is installed.

[0018] As shown in Figure 2(b), the retaining wall panel 3 comprises a foamed resin core material 31 and a urea layer 32 that completely covers the entire surface of the core material 31 without any gaps. The urea layer 32 is a resin layer composed of a resin containing urea bonds (urea resin).

[0019] The core material 31, like the retaining wall panel 3, is a plate-like structure with an arc-shaped curve between its left and right ends. The core material 31 is made of a foamed resin that has sufficient strength to withstand the pressure exerted by the soil on the sloping ground SL. For example, the core material 31 can be made of low-expansion polystyrene foam (for example, polystyrene foam with an expansion ratio of 5 to 40 times), rigid polyurethane foam, phenolic foam, expanded polyvinyl chloride foam, expanded polypropylene, or high-density polyethylene foam. In the example earth retaining panel 3, low-expansion polystyrene foam is used as the core material 31. The expansion ratio of this polystyrene foam is appropriately determined according to the slope SL on which the earth retaining structure 1 is installed. The core material 31 may be formed into a curved plate shape by foaming it within the mold, or it may be cut into a curved plate shape from a block of foamed resin.

[0020] The urea resin constituting the urea layer 32 includes polyurea resin formed by the reaction of isocyanate and amine compounds, and composite resins of polyurea resin and polyurethane resin. Polyurethane resin is a resin obtained by the reaction of isocyanate and polyol. Therefore, a composite resin of polyurea resin and polyurethane resin is obtained by reacting isocyanate with a mixture of an amine compound and a polyol. Here, the ratio of the amine compound to the polyol in the mixture is determined so that the amine compound is more abundant than the polyol. As a result, the resulting composite resin possesses the waterproof and chemical resistance properties characteristic of polyurea.

[0021] The urea layer 32 uses a urea resin whose elongation rate is greater than that of the foamed resin that makes up the core material 31. By using such a urea resin, even if the retaining wall panel 3 deforms, the urea layer 32 expands and contracts, suppressing cracking of the core material 31. As a result, the retaining wall panel 3 becomes less susceptible to damage even when deformed. The urea layer 32 is formed by spraying urea resin onto the surface of the core material 31 (as described later). The thickness of the urea layer 32 is appropriately determined according to the slope SL on which the retaining structure 1 is installed, and can be, for example, 2 to 5 mm. However, the thickness of the urea layer 32 is not limited to the example thickness.

[0022] <Main stake 2> As shown in Figures 1 and 3, for example, H-shaped steel is preferably used for the main pile 2. As shown in Figure 3(b), the H-shaped steel has a pair of flanges 21 (21o, 21i) and a web 22 provided between the flanges 21, and the flanges 21 and web 22 form a groove 2RS. The groove 2RS is the part into which the left and right ends 3L, 3R of the earth retaining panel 3 are inserted. The main pile 2 is driven into the ground G with one flange 21o positioned on the upper side (mountain side) of the sloping ground SL and the other flange 21i positioned on the lower side (valley side) of the sloping ground SL. For the sake of explanation, the flange 21o positioned on the upper side of the sloping ground SL is referred to as the upper flange 21o, and the flange 21i positioned on the lower side of the sloping ground SL is referred to as the lower flange 21i.

[0023] The type of H-shaped steel that makes up the main pile 2 can be appropriately determined according to the slope SL on which the earth retaining structure 1 is installed. For example, using the wide H-shaped steel shown in Figure 3(b), for example, a beam depth (height of the H-shaped steel) indicated by symbol 2H is 150 mm, a flange width indicated by symbol 21B is 150 mm, a web thickness indicated by symbol t1 is 7 mm, and a flange thickness indicated by symbol t2 is 10 mm can be used. If this H-shaped steel is used for the main pile 2, the distance 21H between the inner surfaces of the flanges 21 (i.e., the width of the groove 2RS) will be 130 mm, which is wider than the thickness D3 (100 mm) of the earth retaining panel 3. The length of the main pile 2 is determined according to the height of the above-ground portion of the retaining wall structure 1 and the length of the portion buried underground in the sloping ground SL.

[0024] Note that the H-shaped steel that can be used for the main pile 2 is not limited to these dimensions. For example, an H-shaped steel with a beam depth 2H of 200 mm, a flange width 21B of 200 mm, a web thickness t1 of 8 mm, and a flange thickness t2 of 12 mm may be used. When an H-shaped steel of these dimensions is used as the main pile 2, the thickness D3 of the retaining wall panel 3 is set to be thinner than the width 21H (176 mm) of the groove 2RS. For example, the thickness D3 of the retaining wall panel 3 can be set to 150 mm. Furthermore, H-shaped steel of other dimensions can be used for the main pile 2. In addition, the main pile 2 may be made of a member other than H-shaped steel, as long as it is configured to support the left and right ends 3L and 3R of the retaining wall panel 3.

[0025] <Support bracket 4> A support bracket 4 is attached to the main pile 2. As shown in Figure 3(b), the support bracket 4 comprises a fastening portion 41 that is fastened to the lower flange 21i of the main pile 2, contact pieces 42 that abut against the inner surfaces 3i (inner surfaces of the arc) of each left and right end of the retaining wall panel 3 to suppress rattling of the retaining wall panel 3, and fixing screws 43 for fixing the support bracket 4 to the main pile 2.

[0026] The fastening portion 41 is made of, for example, a steel plate that is roughly U-shaped in plan view. The fastening portion 41 may be made by welding together multiple rectangular steel plates, or by bending a single steel plate into a roughly U-shape. The fastening portion 41 is provided with a female thread into which the male thread of the fixing screw 43 is tightened. The contact piece 42 is a tongue-shaped member, and is made of, for example, a curved steel plate. The contact piece 42 is provided integrally with the fastening portion 41. Therefore, the contact piece 42 can be provided integrally with the fastening portion 41 by bending a single steel plate. Alternatively, the fastening portion 41 and the contact piece 42 may be manufactured separately and joined together by welding. The fixing screw 43 can be made of, for example, a hexagonal bolt. When the fastening part 41 is attached to the lower flange 21i and the male thread of the fixing screw 43 is tightened into the female thread of the fastening part 41, the support bracket 4 (fastening part 41) is fixed to the main pile 2.

[0027] <Earth retaining structure 1> As shown in Figure 1, multiple main piles 2 are installed on the sloping ground SL at intervals corresponding to the width W3 of the retaining wall panel 3. As shown in Figure 3(a), the retaining wall panel 3 is supported by the main piles 2 such that its left and right central portions are located higher on the sloping ground SL than its left and right ends (i.e., it bulges out towards the area to be protected). This earth retaining structure 1 can be constructed, for example, by driving multiple main piles 2 into the ground G of a sloping area SL at intervals indicated by the symbol SP2 in Figure 2(c), then installing earth retaining panels 3 between pairs of main piles 2,2, and finally attaching support fittings 4 to the main piles 2 after the earth retaining panels 3 have been installed. In the example earth retaining structure 1, as shown in Figures 1 and 2(c), four earth retaining panels 3 are stacked between a pair of main piles 2, 2. This creates a wall with a spacing SP2 of approximately 2000 mm between the main piles 2 and a height H1 of approximately 2000 mm.

[0028] As shown in Figure 3(b), the left and right ends 3L and 3R of the retaining wall panel 3 are inserted into the grooves 2RS of the main pile 2, which is made of H-shaped steel. Within the grooves 2RS, the contact piece 42 of the support fitting 4 is in contact with the inner surface 3i (the inner surface of the arc) of the retaining wall panel 3. Therefore, the left and right ends 3L and 3R of the retaining wall panel 3 are sandwiched between the upper flange 21o of the main pile 2 and the contact piece 42 of the support fitting 4, thereby suppressing rattling of the retaining wall panel 3 in the installed state.

[0029] With the earth retaining structure 1 having the above configuration, as shown in Figure 4(a), when the earth pressure EP from the sloping ground SL acts on the outer surface 3o (the surface on which the external force acts) of the earth retaining panel 3, a compressive force is generated in the earth retaining panel 3. This is because the left and right ends 3L and 3R of the earth retaining panel 3 are supported (fixed) by the main piles 2. When the earth pressure EP presses the retaining wall panel 3 against the lower side of the sloping ground SL, the retaining wall panel 3 deforms so that its shape approaches that of a flat plate. The closer the shape of the retaining wall panel 3 approaches that of a flat plate, the greater the degree of compression of the retaining wall panel 3, and the stronger the retaining wall panel 3 becomes. As a result, the retaining wall panel 3 becomes less likely to curve beyond the main pile 2 and towards the lower side of the sloping ground SL (i.e., the bearing capacity of the retaining wall panel 3 is improved), and the retaining wall panel 3 becomes less likely to detach from the main pile 2. As described above, the urea layer 32 of the retaining wall panel 3 is made of a resin whose elongation rate is greater than that of the foamed resin that makes up the core material 31. Therefore, even if the retaining wall panel 3 deforms, the urea layer 32 expands and contracts, suppressing cracking of the core material 31. As a result, damage to the retaining wall panel 3 can be suppressed.

[0030] As shown in Figures 4(b) and 4(c), when the retaining wall panel 3 is pressed against the lower side of the sloping ground SL by the earth pressure EP, and when the retaining wall panel 3 deforms to become closer to a flat plate shape, the contact piece 42 of the support fitting 4 elastically deforms in accordance with the movement of the retaining wall panel 3, generating a reaction force that pushes the retaining wall panel 3 back towards the upper side of the sloping ground SL. Since the retaining wall panel 3 is also supported by the reaction force generated by the contact piece 42, this also makes it difficult for the retaining wall panel 3 to come off the main pile 2.

[0031] Furthermore, when the earth pressure EP presses the retaining panel 3 against the lower side of the sloping ground SL, a gap SP is formed between the upper flange 21o of the main pile 2 and the outer surface 3o (the outer surface of the arc) of the retaining panel 3. Soil from the sloping ground SL can flow into this gap SP. When soil flows into the gap SP, the left and right ends of the retaining panel 3 are strongly pressed toward the lower flange 21i of the main pile 2 by this soil. As described above, the contact piece 42 of the support bracket 4 attempts to push the retaining wall panel 3 back towards the upper side of the sloping ground SL due to the reaction force. As a result, both the left and right ends of the retaining wall panel 3 are firmly fixed within the groove of the main pile 2, effectively preventing the retaining wall panel 3 from coming off the main pile 2.

[0032] <Manufacturing method for retaining wall panel 3> Next, the manufacturing method of the earth retaining panel 3 will be described. Figure 5(a) is a diagram illustrating the spraying process in which urea resin 32' is sprayed onto the surface of the core material 31, and Figure 5(b) is a diagram illustrating the urea resin 32' spraying apparatus 50.

[0033] The retaining wall panel 3 is manufactured by spraying urea resin 32' onto the surface of the core material 31. For example, as shown in Figure 5(a), the retaining wall panel 3 is manufactured by adhering a mist of urea resin 32' sprayed from a spray gun 58 to the surface of the core material 31. In this case, the urea resin 32' is produced by a chemical reaction caused by a collision mixing of a polyisocyanate compound (main component) and an amine compound having active hydrogen or a mixture of an amine compound and a polyol (curing agent) using a spray gun 58. Here, the thickness of the urea resin film formed on the surface of the core material 31 in a single spraying operation is approximately 0.3 mm. As mentioned above, the thickness of the urea layer 32 is generally 2 to 5 mm. Therefore, in the spraying process, the urea resin 32' is repeatedly sprayed onto the entire surface of the core material 31 to form a urea layer 32 of the desired thickness.

[0034] In the spraying apparatus 50 shown in Figure 5(b), a main agent LQ1 containing a polyisocyanate compound and a curing agent LQ2 containing an amine compound, or a mixture of an amine compound and a polyol, are mixed by impact using a spray gun 58 and sprayed as a mist.

[0035] Therefore, the spraying device 50 includes a first tank 51 containing the main agent LQ1, a second tank 52 containing the hardener LQ2, a first pump 53 for dispensing the main agent LQ1 from the first tank 51, a second pump 54 for dispensing the hardener LQ2 from the second tank 52, a high-pressure metering pump 55 for dispensing a predetermined amount of each of the main agent LQ1 and hardener LQ2 under sufficient pressure, a heater 56 for heating the main agent LQ1 and hardener LQ2 being transported, a heater-equipped hose 57 for maintaining the temperatures of the main agent LQ1 and hardener LQ2, and a spray gun 58 for mixing the main agent LQ1 and hardener LQ2 by collision and spraying them in a mist state. Furthermore, the spraying device 50 is equipped with a reaction control device that controls a high-pressure metering pump 55 to adjust the mixing ratio of the main agent LQ1 and the hardener LQ2 to an appropriate ratio, and also controls a heater 56 to vary the heating temperature, etc.

[0036] As can be understood from the above explanation, the earth retaining panel 3 of this embodiment can be manufactured by spraying a mist-like urea resin 32' onto the core material 31, and therefore can be manufactured easily.

[0037] Figures 6(a) to 6(h) show modified examples of the retaining wall panel 3 with different thicknesses and curvatures. As described above, the dimensions and curvature of each part of the retaining wall panel 3 can be appropriately determined according to the slope SL on which the retaining wall structure 1 is installed. Figures 6(a) to 6(d) show modified examples of retaining wall panels 3 with a thickness D3 of 100 mm. In Figure 6(a), the retaining wall panel 3 has a curvature X3 of 50 mm. In Figure 6(b), the retaining wall panel 3 has a curvature X3 of 100 mm. In Figure 6(c), the retaining wall panel 3 has a curvature X3 of 150 mm. In Figure 6(d), the retaining wall panel 3 has a curvature X3 of 200 mm. Figures 6(e) to (h) show modified examples of the retaining wall panel 3 with a thickness D3 of 150 mm. The retaining wall panel 3 in Figure 6(e) has a curvature X3 of 50 mm, the retaining wall panel 3 in Figure 6(f) has a curvature X3 of 100 mm, the retaining wall panel 3 in Figure 6(g) has a curvature X3 of 150 mm, and the retaining wall panel 3 in Figure 6(h) has a curvature X3 of 200 mm.

[0038] [Second Embodiment] In the earth retaining structure 1 according to the first embodiment, the earth retaining panel 3 is provided in a substantially rectangular shape that is curved in an arc shape when viewed from above, and the thickness of the earth retaining panel 3 is substantially constant. However, the earth retaining panel is not limited to this form. The earth retaining panel 3A according to the second embodiment will be described below. Figure 7(a) is a perspective view showing the earth retaining panel 3A according to the second embodiment, Figure 7(b) is a view from above of a part of the earth retaining structure 1A according to the second embodiment, and Figure 7(c) is a diagram illustrating the gap SP formed between the groove 2RS of the main pile 2 and the earth retaining panel 3A due to the deformation of the earth retaining panel 3A according to the second embodiment.

[0039] As shown in Figures 7(a) and 7(b), the retaining wall panel 3A according to the second embodiment is characterized in that the thickness of the panel body portion 3C1 that is not inserted into the groove portion 2RS of the main pile 2 is greater than the thickness of the left and right ends 3L, 3R that are inserted into the groove portion 2RS of the main pile 2, and that a soil guide surface 3G1 is provided on the outer surface 3o of the retaining wall panel 3A between the panel body portion 3C1 and the left and right ends 3L, 3R. In the retaining wall panel 3A according to the second embodiment, the panel body 3C1 is made thicker than the left and right ends 3L and 3R, thereby improving the rigidity of the retaining wall panel 3A and improving its ability to withstand soil and sand on the sloping ground SL (protected area).

[0040] The guide surface 3G1 is a plane connecting the outer surface 3o of the panel body 3C1 and the outer surfaces 3o of the left and right ends 3L and 3R of the retaining wall panel 3. As shown in Figure 7(c), when the retaining wall panel 3A is pressed to the lower side of the slope SL by the earth pressure EP from the slope SL, the guide surface 3G1 guides the soil towards the gap SP formed between the upper flange 21o of the main pile 2 and the outer surfaces 3o of the left and right ends 3L and 3R. Therefore, soil and sand from the sloping ground SL can easily flow into the gap SP, and the left and right ends of the retaining wall panel 3 are firmly fixed within the groove 2RS of the main pile 2, which can more effectively suppress the inconvenience of the retaining wall panel 3A coming off the main pile 2.

[0041] [Third Embodiment] In the earth retaining panel 3A according to the second embodiment, the thickness of the panel body portion 3C1 was substantially constant. However, the earth retaining panel is not limited to this form. The earth retaining panel 3B according to the third embodiment will be described below. Figure 8(a) is a perspective view showing the earth retaining panel 3B according to the third embodiment, Figure 8(b) is a view from above of a part of the earth retaining structure 1B according to the third embodiment, and Figure 8(c) is a diagram illustrating the gap SP formed between the groove portion 2RS of the main pile 2 and the earth retaining panel 3B due to the deformation of the earth retaining panel 3B according to the third embodiment.

[0042] As shown in Figures 8(a) and 8(b), the retaining wall panel 3B according to the third embodiment is characterized in that the thickness of the panel body portion 3C2 that is not inserted into the groove portion 2RS of the main pile 2 is greater than the thickness of the left and right ends 3L, 3R that are inserted into the groove portion 2RS of the main pile 2, the thickness of the panel body portion 3C2 is greatest in the center in the left-right direction and gradually becomes thinner towards both the left and right sides, and the outer surface 3o of the panel body portion 3C2 is a curved surface that functions as a guide surface 3G2 for soil and sand. In the retaining wall panel 3B according to the third embodiment, the rigidity of the retaining wall panel 3B is increased by making the panel body portion 3C2 thicker than both the left and right ends, thereby improving its resistance to soil and sand on the sloping ground SL. Furthermore, since the outer surface 3o of the panel body portion 3C2 functions as a soil and sand guide surface 3G2, the left and right ends 3L, 3R of the retaining wall panel 3B are firmly fixed within the groove portion 2RS of the main pile 2, and the inconvenience of the retaining wall panel 3B coming off the main pile 2 can be suppressed even more effectively.

[0043] [Variation] In the embodiments described above, earth retention structures 1, 1A, and 1B were exemplified as earthwork structures, but earthwork structures are not limited to earth retention structures 1, 1A, and 1B. For example, earthwork structures also include rockfall protection fences. In the rockfall protection fence, rockfall protection panels are used instead of earth retention panels 3, and the rockfall protection panels are supported at both ends by main piles 2. The rockfall protection panels are a type of panel member provided in earthwork structures, and their structure is the same as that of earth retention panels 3. Therefore, a detailed explanation is omitted. In the rockfall protection fence, the outer surface of the rockfall protection panel (the surface on which external forces act; corresponding to the outer surface 3o of the retaining wall panel 3) is not in contact with soil, and the rockfall is absorbed by the rockfall protection panel. When the rockfall protection panel receives the impact force (external force) of a rockfall, the rockfall protection panel is compressed and deforms to become closer to a flat plate shape. As the rockfall protection panel is compressed and deformed, its strength is increased, and it becomes less likely to bend beyond the main pile 2 to the lower side of the slope SL. As a result, the retaining wall panel 3 becomes less likely to detach from the main pile 2. Furthermore, earthwork structures are not limited to earth retention structures 1, 1A, 1B or rockfall protection fences. Any structure equipped with main piles and panel members is acceptable. For example, a temporary protective fence may also be used.

[0044] Regarding the protected area protected by the earth retaining structures 1, 1A, and 1B, the above embodiments exemplified a sloping area SL, but the protected area is not limited to a sloping area SL. For example, earth retaining structures 1, 1A, and 1B may be provided along the excavated surface created by the excavation of the ground.

[0045] In the embodiments described above, the urea resin 32' constituting the urea layer 32 was exemplified as having an elongation rate greater than that of the foamed resin constituting the core material 31, but the configuration is not limited to this. The elongation rate of the urea resin 32' may be equal to that of the foamed resin constituting the core material 31.

[0046] In the embodiments described above, the support bracket 4 was attached to the main pile 2, but the support bracket 4 can be attached only as needed.

[0047] In the embodiments described above, the earth pressure EP from the sloping ground SL (protected area) formed a gap SP into which soil and sand could flow between the groove 2RS of the main pile 2 and the outer surface 3o of the retaining panel 3, but the configuration is not limited to this. For example, in the rockfall protection fence described above, even if rocks collide with the rockfall protection panel, no gaps are formed through which soil can flow in. Thus, the earthwork structure according to the present invention may be configured in such a way that no gaps are formed by external forces.

[0048] [Summary of Embodiments, Functions, and Effects of the Present Invention] <First Embodiment> This embodiment is a retaining structure 1, 1A, 1B (a type of earthwork structure) comprising retaining panels 3, 3A, 3B (a type of panel member) having a core material 31 made of a plate-shaped member made of foamed resin and a urea layer 32 made of urea resin 32' that covers the surface of the core material 31, and main piles 2 that are driven into the ground G and support the left and right ends 3L, 3R of the retaining panels 3, 3A, 3B, characterized in that the retaining panels 3, 3A, 3B are plate-shaped with an arc shape between the left and right ends, and are supported by the main piles 2 such that the left and right central parts bulge out towards the sloping ground SL (protected area) than the left and right ends.

[0049] According to the earth retaining structures 1, 1A, and 1B of this embodiment, when the earth retaining panels 3, 3A, and 3B receive earth pressure EP from the sloping ground SL (protected area), the earth retaining panels 3, 3A, and 3B are compressed by this earth pressure EP. As the earth retaining panels 3, 3A, and 3B are compressed, their strength is improved, and they become less likely to bend on the lower side of the sloping ground SL. As a result, the earth retaining panels 3, 3A, and 3B become less likely to detach from the main piles 2.

[0050] <Second Embodiment> The earth retaining structures 1, 1A, and 1B according to this embodiment are characterized in that the elongation rate of the resin constituting the urea layer 32 is greater than the elongation rate of the foamed resin constituting the core material 31. According to the earth retaining structures 1, 1A, and 1B of this embodiment, even if the earth retaining panels 3, 3A, and 3B deform, the urea layer 32 expands and contracts, suppressing cracking of the core material 31. As a result, damage to the earth retaining panels 3, 3A, and 3B can be suppressed.

[0051] <Third Embodiment> In the earth retaining structures 1, 1A, and 1B according to this embodiment, the main pile 2 has a groove 2RS into which the left end portion 3L or the right end portion 3R of the earth retaining panels 3, 3A, and 3B is inserted. Furthermore, the earth retaining structures 1, 1A, and 1B are characterized by being equipped with a support fitting 4 that is attached to the main pile 2 and supports the left end portion 3L or the right end portion 3R of the earth retaining panel 3, which is inserted into the groove 2RS, from the inner surface 3i side of the earth retaining panels 3, 3A, and 3B. According to the earth retaining structures 1, 1A, and 1B of this embodiment, the earth retaining panel 3 is also supported by the support fittings 4, making it difficult for the earth retaining panels 3, 3A, and 3B to detach from the main piles 2.

[0052] <Fourth Embodiment> In the earth retaining structures 1, 1A, and 1B according to this embodiment, the main pile 2 has a groove 2RS into which the left end 3L and right end 3R of the earth retaining panels 3, 3A, and 3B are inserted, and the thickness of the left end 3L and right end 3R of the earth retaining panels 3, 3A, and 3B is thinner than the width of the groove 2RS. Furthermore, when the earth retaining panels 3, 3A, and 3B receive earth pressure EP from the sloping ground SL (protected area), a gap SP is formed between the main pile 2 (upper flange 21o) and the outer surface 3o of the earth retaining panels 3, 3A, and 3B, into which a portion of the soil from the sloping ground SL can flow. According to the earth retaining structures 1, 1A, and 1B of this embodiment, when soil flows into the gap SP formed between the main pile 2 and the earth retaining panels 3, 3A, and 3B, each end 3L and 3R of the earth retaining panels 3, 3A, and 3B is strongly pressed toward the lower flange 21i of the main pile 2. As a result, the left and right ends 3L and 3R of the earth retaining panel 3 are firmly fixed within the groove 2RS of the main pile 2, effectively suppressing the inconvenience of the earth retaining panels 3, 3A, and 3B coming off the main pile 2.

[0053] <Fifth Embodiment> In the earth retaining structures 1A and 1B according to this embodiment, the panel body portions 3C1 and 3C2 (left and right central portions) of the earth retaining panels 3A and 3B are thicker than the left and right ends, and guide surfaces 3G1 and 3G2 are provided between the panel body portions 3C1 and 3C2 and the left and right ends 3L and 3R to guide soil towards the gap SP formed between the main pile 2 and the earth retaining panels 3A and 3B. According to the earth retaining structures 1A and 1B of this embodiment, the guide surfaces 3G1 and 3G2 provided by the earth retaining panels 3A and 3B guide the soil towards the gap SP formed between the upper flange 21o of the main pile 2 and the outer surface of the earth retaining panel 3. Therefore, soil from the sloping ground SL can easily flow into the gap SP, and the left and right ends 3L and 3R of the retaining panels 3A and 3B are firmly fixed within the groove 2RS of the main pile 2, which can more effectively suppress the inconvenience of the retaining panels 3A and 3B coming off the main pile 2. [Explanation of Symbols]

[0054] 1, 1A, 1B... Retaining wall structure (a type of earthwork structure); 2... Main pile, 2RS... Groove of the main pile; 21... Flange of the main pile; 21o... Upper flange; 21i... Lower flange; 21H... Spacing between the inner surfaces of the flanges (width of the groove); 22... Web of the main pile; 3, 3A, 3B... Retaining wall panel (a type of panel member); 3C1, 3C2... Panel body; 3G1, 3G2... Guide surface for soil and sand; 3o... Outer surface of the retaining wall panel; 3i... Inner surface of the retaining wall panel; 3L... Left end of the retaining wall panel; 3R... Right end of the retaining wall panel; 31... Core material; 32... Urea layer ;32'...Urea resin;W3...Width of retaining wall panel;H3...Height of retaining wall panel;D3...Thickness of retaining wall panel;4...Support bracket;41...Fastening part;42...Contact piece;43...Fixing screw;50...Spraying device;51...First tank;52...Second tank;53...First pump;54...Second pump;55...High-pressure metering pump;56...Heater;57...Heater hose;58...Spray gun;LQ1...Main agent;LQ2...Hardening agent;SP...Gap formed between the upper flange and the outer surface of the retaining wall panel;SL...Sloping ground (protected area);G...Ground;EP...Earth pressure

Claims

1. A panel member comprising a core material composed of a plate-shaped member made of foamed resin, and a urea layer made of a resin containing urea bonds that covers the surface of the core material, An earthwork structure comprising main piles driven into the ground and supporting the left and right ends of the earth retaining panel, The aforementioned panel member is a plate-like shape curved in an arc shape between its left and right ends, and is supported by the main pile such that the left and right central portions bulge out towards the surface where external forces are applied compared to the left and right ends, making it an earthwork structure.

2. The earthwork structure according to claim 1, characterized in that the elongation rate of the resin constituting the urea layer is greater than the elongation rate of the foamed resin constituting the core material.

3. The main pile has a groove into which the left end or right end of the panel member is inserted. The earthwork structure according to claim 1, characterized in that it is provided with a support fitting that is attached to the main pile and supports the left end or right end of the panel member, which is inserted into the groove, from the inner surface side of the panel member.

4. The main pile has grooves into which the left end and right end of the panel member are inserted. The thickness of the left end and the right end of the panel member is thinner than the width of the groove. The earthwork structure according to claim 1, wherein the panel member is an earth retaining panel, and when the panel member is subjected to earth pressure from the area to be protected, a gap is formed between the main pile and the outer surface of the panel member, into which a portion of the soil from the area to be protected can flow.

5. The earthwork structure according to claim 4, characterized in that the left and right central portions of the panel member are thicker than the left and right ends, and a guide surface is provided between the left and right central portions and the left and right ends to guide the soil towards the gap.

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