JP6262041B2 - Buried line protection plate - Google Patents

Description

  The present invention relates to a buried pipeline protection plate, and more particularly to a buried pipeline protection plate that is buried above a buried pipeline in order to protect an existing buried pipeline buried in the ground, for example.

  An example of a conventional buried pipe protection plate is disclosed in Patent Document 1. The buried pipeline protection plate of Patent Document 1 includes a metal plate and a waste plastic resin layer that seals the entire surface of the metal plate with a predetermined thickness, and is formed in a rectangular plate shape. And by being arranged side by side above the existing buried pipeline, the existing buried pipeline is prevented from being damaged by excavation work when constructing a new underground object.

JP 2011-114940 A [H02G 9/02]

  In the buried pipeline protection plate of Patent Document 1, since the entire surface of the metal plate is sealed by the resin layer, due to the difference in thermal expansion coefficient between the metal and the resin, around the peripheral edge of the metal plate Stress concentration occurs, and in some cases, cracks (cracks) may occur in the resin layer particularly at positions above and below the peripheral edge of the metal plate. In order to prevent cracking of the resin layer, it is conceivable to increase the thickness of the resin layer. However, simply increasing the thickness of the entire resin layer has a small effect of preventing cracking. Further, when the thickness of the resin layer is increased, the overall weight of the buried pipe protection plate increases and the material cost also increases.

  Therefore, the main object of the present invention is to provide a novel buried pipe protection plate.

  Another object of the present invention is to provide a buried pipe protection plate that can appropriately prevent cracking of a resin layer.

A first invention is a buried pipe protection plate buried above the buried pipeline in order to protect an existing buried pipeline buried in the ground, the metal plate, and the entire surface of the metal plate comprising a resin layer for sealing the resin layer is in the inner side of the peripheral edge of the metal plate, have a stress dispersion portion formed by reducing the thickness of the resin layer, buried from the outer edge of the stress dispersion portion The length W of the resin layer to the side surface of the pipeline protection plate is 35 mm or more and 100 mm or less, and the length FW of the resin layer from the peripheral edge of the metal plate to the side surface of the buried pipeline protection plate is from 25 mm It is a buried pipe protection plate that is larger than the length W.

In the first invention, the buried pipeline protection plate is a protection plate for protecting the existing buried pipeline, and is buried side by side above the buried pipeline. The buried pipeline protection plate includes a metal plate and a resin layer that seals the entire surface of the metal plate. That is, the buried pipe protection plate has a structure in which the metal plate is embedded in the center of the resin layer so that the metal plate is sandwiched between the resin layers having a predetermined thickness. And the stress dispersion | distribution part is provided in the resin layer in the position inside the peripheral side edge of a metal plate. The stress dispersion part is formed by making the thickness of the resin layer thinner than the thickness at the position of the peripheral edge of the metal plate, and by deliberately providing a portion with reduced strength with respect to the resin layer, the peripheral side of the metal plate It has a function of releasing (dispersing) stress concentrated on the resin layer at the upper and lower positions of the edge. In addition, the length W of the resin layer from the outer edge of the stress distribution portion to the side surface of the buried pipe protection plate is set to a size of 35 mm or more and 100 mm or less, and the side surface of the buried pipe protection plate from the peripheral edge of the metal plate. The length FW of the resin layer is set to a size larger than 25 mm and smaller than the length W.

  According to the first invention, the stress dispersion part is formed in the resin layer, and the stress concentrated on the resin layer is released to the stress dispersion part at the upper and lower positions of the peripheral edge of the metal plate. Can be prevented.

  The second invention is dependent on the first invention, and the surface of the central portion of the resin layer is formed flush with the inner edge in the thickness direction of the stress dispersion portion.

  In the second invention, the surface of the central portion of the resin layer is formed flush with the inner edge in the thickness direction of the stress dispersion portion. That is, the thickness of the central portion of the resin layer is the same as the thickness at the inner edge position of the stress dispersion portion, and the thickness of the central portion of the resin layer is thinner than the peripheral portion via the stress dispersion portion.

  According to the second invention, since the amount of resin forming the resin layer can be reduced, the material cost can be reduced and the protective plate can be reduced in weight.

  According to this invention, since the stress dispersion portion is formed in the resin layer and the stress concentrated on the resin layer is released to the stress dispersion portion at the upper and lower positions of the peripheral side edge of the metal plate, the crack of the resin layer can be appropriately prevented. .

  The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative view schematically showing a state in which an embedded line protection plate according to an embodiment of the present invention is embedded above an embedded line. It is a top view which shows the buried pipe line protection board of FIG. 3A and 3B are cross-sectional views showing the buried pipe protection plate in FIG. 1, where FIG. 3A shows a cross section taken along line IIIa-IIIa in FIG. 2, and FIG. 2B shows a cross section taken along line IIIb-IIIb in FIG. It is an illustration figure which expands and shows the side edge part of the buried pipe line protection board of FIG. It is an illustration figure which shows the manufacturing method of the buried pipe protection board of FIG. 1, Comprising: (a) shows a mode that the lower resin layer has been arrange | positioned to the lower metal mold | die, (b) is on the lower resin layer. A state where the metal plate is arranged is shown, and (a) shows a state where the upper resin layer is arranged on the metal plate and pressed by the upper die. FIG. 2 is an illustrative view schematically showing a state in which the buried pipeline protection plates of FIG. 1 are arranged side by side above the buried pipeline. It is sectional drawing which expands and shows the side edge part of the buried line protection board which is another Example of this invention. It is sectional drawing which expands and shows the side edge part of the buried line protection board which is further another Example of this invention. It is an illustration figure which shows the buried pipe line protection plate which is further another Example of this invention, Comprising: (a) is a top view, (b) is sectional drawing.

  Referring to FIG. 1, an embedded line protection plate 10 (hereinafter simply referred to as “protection plate 10”) according to an embodiment of the present invention includes a cable protection tube, a water pipe, and a gas embedded in the ground. A protection plate for protecting an existing buried pipeline 100 such as a pipe, which is buried in advance above the buried pipeline 100. Then, when constructing a new underground object, etc., the progress of the excavator is stopped, or the operator is made aware of the presence of the protective plate 10 (and hence the buried pipe line 100) by excavation work. The buried pipe line 100 is prevented from being damaged.

  As shown in FIG. 2 to FIG. 4, the protection plate 10 includes a metal plate 12 and a resin layer 14, and the central portion of the upper surface and the lower surface is recessed more than the peripheral portion (that is, the thickness of the central portion is reduced). It is formed in a plate shape. The size of the protection plate 10 is appropriately set according to the pipe diameter of the buried pipeline 100 and the like. As an example, when the pipe diameter of the buried conduit 100 to be protected is 75 to 200 mm, the length of the long side of the protection plate 10 is, for example, 800 mm, and the length of the short side is, for example, 500 mm. Further, the thickness a of the central portion of the protection plate 10 is, for example, 40 mm, and the thickness b of the peripheral portion is, for example, 50 mm.

  The metal plate 12 is formed in a rectangular thin plate shape with a metal that is relatively light and has a certain level of rigidity. In this embodiment, the metal plate 12 is formed of a general structural rolled steel material (SS400) conforming to JIS-G3101, the length of the long side is 740 mm, and the length of the short side is 440 mm. is there. The thickness of the metal plate 12 is appropriately set by taking into consideration the material of the metal plate 12 and the like so that at least perforation by an earth auger-type building pillar machine can be prevented. In the case of this embodiment using SS400, the thickness of the metal plate 12 is, for example, 2.3 mm.

  The resin layer 14 constitutes an outer shell or a main body of the protection plate 10 and is provided so as to seal the entire surface of the metal plate 12. That is, the resin layer 14 is formed in a substantially rectangular plate shape, and the metal plate 12 is embedded in the inner center of the resin layer 14 so that the metal plate 12 is sandwiched between the resin layers 14. By sealing the entire surface of the metal plate 12 with the resin layer 14 in this way, corrosion of the metal plate 12 due to underground components is prevented, so that the function of the protection plate 10 can be maintained for a long time.

  As a material for the resin layer 14, waste plastic (recycled resin) such as polyethylene, polypropylene, vinyl chloride, and polyethylene terephthalate may be used. Waste plastics are blended with several types of materials and are non-uniform materials that are prone to cracking. By forming the resin layer 14 using waste plastics, it is possible to contribute to environmental protection and reduce material costs. You can also However, the resin layer 14 can also be formed using virgin plastic (unused resin). Of the waste plastics, the resin layer 14 is preferably formed using polyolefin waste plastics mainly composed of polyethylene and polypropylene. This is because when polyolefin waste plastic is used, the resin layer 14 becomes more flexible than when waste plastic such as vinyl chloride or polyethylene terephthalate is used, and the tip of the rod of a boring machine, which will be described later, is further blocked. It is because it becomes easy. In this embodiment, the resin layer 14 is formed of polyolefin waste plastic.

  And the stress dispersion | distribution part 20 is provided in the position inside the peripheral side edge 12a of the metal plate 12 in the upper surface and lower surface of the resin layer 14. FIG. The stress dispersion portion 20 is formed by making the thickness (length in the vertical direction) of the resin layer 14 smaller than the thickness at the position of the peripheral edge 12 a of the metal plate 12, and suppresses the strength with respect to the resin layer 14. By deliberately providing the portion, it has a function of releasing (dispersing) stress concentrated on the resin layer 14 at the upper and lower positions of the peripheral edge 12 a of the metal plate 12.

  Specifically, the stress dispersion portion 20 is formed in a rectangular frame shape extending along the peripheral edge 12 a of the metal plate 12 in plan view, and gradually becomes thinner toward the center side of the resin layer 14. That is, the surface of the stress dispersion portion 20 is an inclined surface 20 a that approaches the metal plate 12 toward the center side of the resin layer 14. Although the inclination angle of the inclined surface 20a is not particularly limited, in this embodiment, it is 30 ° with respect to the horizontal direction.

  Further, the surface of the central portion of the resin layer 14, that is, the central portions of the upper surface and the lower surface of the resin layer 14 are formed flush with the inner edge 20 b in the thickness direction (vertical direction) of the stress dispersion portion 20. That is, the thickness of the center portion of the resin layer 14 is the same as the thickness at the position of the inner edge 20b of the stress dispersion portion 20, and the resin layer 14 is thinner at the center portion than the peripheral portion via the stress dispersion portion 20. It is (it is depressed).

  In addition, the resin layer 14 is formed to have a uniform thickness on one side and the other side of the metal plate 12 in the vertical direction, and on one side and the other side of the metal plate 12 in the horizontal direction (left and right direction and front and rear direction). It is formed in a uniform length. That is, the resin layer 14 is formed so as to be symmetric with respect to the metal plate 12 in the vertical and horizontal directions. Thereby, the distortion generated inside the resin layer 14 after the protection plate 10 is molded (after cooling) can be equally borne on one side and the other side in the vertical and horizontal and front-back directions of the metal plate 12, Deformation of the protective plate 10 due to strain can be prevented.

  The thickness a1 of the central portion of the resin layer 14 on the upper side of the metal plate 12 is set to 17 mm or more, which is a thickness that allows the tip of the rod to be blocked by the resin layer 14 when the rod of the boring machine contacts the resin layer 14. It is preferred that In this embodiment, the thickness of the resin layer 14 is made as thin as possible from the viewpoints of weight reduction and material cost reduction, and the thickness of the resin layer 14 may be slightly shifted when the protective plate 10 is molded. Considering this, the thickness a1 is set to about 20 mm (specifically, 18.9 mm). The thickness a2 of the central portion of the resin layer 14 below the metal plate 12 is also set to about 20 mm in accordance with the thickness a1.

  Further, the horizontal length FW of the resin layer 14 from the peripheral edge 12a of the metal plate 12 to the side surface of the protection plate 10 is set to 30 mm, for example. When the length FW is set to 25 mm or less, when the peripheral portions of the lower resin layer 14a and the upper resin layer 14b are fused and integrated by press molding described later (see FIG. 5), This is because the fusion-bonded area becomes small and the resin layer 14 may be peeled up and down. Also, if the length FW is set to 25 mm or less, the stress due to the difference in coefficient of thermal expansion between the metal and the resin increases on the side surface of the resin layer 14, and there is a possibility that the side surface of the resin layer 14 may crack. is there. On the other hand, when the protective plates 10 are arranged side by side in the ground, it is preferable that the distance between the metal plates 12 of the adjacent protective plates 10 (that is, the portion where only the resin layer 14 is provided) be as small as possible. Therefore, the length FW is preferably set to about 30 mm.

  Further, the horizontal length W of the resin layer 14 from the horizontal outer edge of the stress dispersion portion 20 to the side surface of the protective plate 10 is set to 60 mm, for example. Here, the length W is preferably set to about 35-100 mm. This is because when the length W is smaller than 35 mm, that is, the distance from the peripheral edge 12a of the metal plate 12 to the stress dispersing portion 20 (the thickness of the resin layer 14 from the peripheral edge 12a to the inclined surface 20a) When the distance is smaller than the distance from the peripheral edge 12a of the plate 12 to the surface of the resin layer 14 immediately above it (the surface P immediately above), stress is excessively collected in the stress dispersion portion 20, and the resin layer 14 is positioned at the position of the stress dispersion portion 20. This is because cracks may occur. On the other hand, when the length W exceeds 100 mm, the stress dispersion effect by the stress dispersion portion 20 becomes small.

  Table 1 shows the analysis result of the stress generated in the resin layer 14 and the result of the crack test in the actual sample by the inventors. Here, in addition to this example (Example 1), based on the dimensions of Example 1, the length W from the outer edge of the stress dispersion portion 20 to the side surface of the protective plate 10 and the thickness of the peripheral portion of the resin layer 14 b and the result about each Example which changed length FW (refer FIG. 4) from the peripheral edge 12a of the metal plate 12 to the side surface of the protection board 10 is shown. In addition, as a comparative example, a result of a conventional protective plate having a flat surface and having no stress dispersion portion is shown. The protective plate of the comparative example has the same configuration as that of this example except that the resin layer does not have a stress dispersion portion. That is, the protective plate of the comparative example has a configuration in which the entire surface of the metal plate formed of SS400 having a thickness of 2.3 mm is sealed with a resin layer made of polyolefin waste plastic.

  Here, in the stress analysis, the position of the metal plate 12 was fixed, a load of 1500 N was applied to the resin layer 14 in the direction of pulling to the center side, and the stress distribution generated in the resin layer 14 at that time was calculated. In Table 1, the stress of the resin layer 14 on the surface P (see FIG. 4) immediately above the peripheral edge 12a of the metal plate 12 is shown as a representative value. The position of the directly upper surface P is a portion where the resin layer 14 is cracked in the conventional protective plate having no stress dispersion portion. If the stress at this position can be reduced, it can be evaluated that the cracking of the resin layer 14 is prevented. Because. In the crack test, the protective plate 10 was repeatedly heated for 3 hours at 40 ° C. and cooled for 9 hours at −10 ° C. for 3 cycles, and then visually checked for cracks. For each example and each comparative example, the crack test was performed 5 samples at a time, and all samples were found to be acceptable (O), and those that were cracked were rejected (X). did.

  As shown in Table 1, in Comparative Example 1 in which the thickness of the protective plate is 40 mm throughout, the stress on the immediately upper surface P was 1.1 MPa. Further, in Comparative Example 2 in which the thickness of the protective plate is 50 mm over the entire surface, the stress on the surface P immediately above is only 0.9 MPa, although it is smaller than the stress when the thickness is 40 mm. On the other hand, in all of Examples 1-7, the stress of the directly upper surface P was 0.8 MPa or less. From this, it is possible to reduce the stress of the directly upper surface P by providing the stress dispersion portion 20 rather than increasing the thickness of the entire resin layer 14, that is, by releasing (dispersing) the stress to the stress dispersion portion 20. It can be seen that the stress on the directly upper surface P can be effectively reduced.

  Moreover, in the crack test, in both Comparative Examples 1 and 2, cracks occurred in the resin layer. On the other hand, in any of Examples 1-5, the resin layer 14 was not cracked, and abnormalities such as deformation were not confirmed. However, in Examples 6 and 7 in which the length FW was 25 mm or less, the resin layer 14 did not crack on the surface P immediately above, but there was a crack on the side surface of the resin layer 14. In the stress analysis, it is calculated that the stress on the side surface of the resin layer 14 is 1.5 MPa in Example 6 and 0.9 MPa in Example 7, and the stress on the side surface of the resin layer 14 is large. This is considered to be a cause of cracking.

  As described above, the stress distribution portion 20 is provided in the resin layer 14 based on the stress analysis result and the crack test result, whereby the stress on the surface P immediately above the resin layer 14 can be effectively reduced. It was confirmed that the crack of 14 can be prevented appropriately.

  In consideration of the stress analysis result and the crack test result, if the stress generated on the surface of the resin layer 14 is 0.9 MPa or more under the analysis condition in which a load of 1500 N is applied to the resin layer 14, the resin layer 14 is actually cracked. When the stress generated on the surface of the resin layer 14 is 0.8 MPa or less, it can be said that the resin layer 14 is not cracked.

  Next, an example of a method for manufacturing the protection plate 10 will be described with reference to FIG. The protective plate 10 is manufactured using press molding by a press molding machine including a lower mold 30 and an upper mold 32. The press surfaces of the lower mold 30 and the upper mold 32 are provided with projecting portions 30a and 32a for forming the stress dispersion portion 20 and the central recess with respect to the resin layer 14 of the protective plate 10. Yes. However, the protrusions 30a and 32a are not necessarily provided integrally with the lower mold 30 and the upper mold 32, and are provided as separate members on the lower side and the upper side of the protective plate 10 when the protective plate 10 is press-molded. It may be placed. Hereinafter, a method for manufacturing the protection plate 10 will be specifically described.

  First, a recycled resin prepared by pulverizing waste plastic is supplied to a hopper of an extrusion molding machine, heated and melted at a temperature of about 180 to 200 ° C. by an extrusion molding machine, and extruded as, for example, a rod-shaped resin material.

  Next, as shown in FIG. 5A, a resin material that is half the amount of resin that forms the resin layer 14 is placed on the lower mold 30 of the press molding machine. Then, a flat plate for pressing is placed on the resin material, the upper mold 32 is lowered from above, and the resin material is uniformly filled to the lower corners of the lower mold 30 for a predetermined time. Hold. Thereafter, the upper mold 32 is raised and the flat plate for press is removed. As a result, a lower resin layer 14a that covers the lower surface of the metal plate 12 is formed. Moreover, the stress dispersion | distribution part 20 is formed in the surface (lower surface) of the lower resin layer 14a by the protrusion part 30a.

  Subsequently, as shown in FIG. 5B, the metal plate 12 is placed at the center position on the upper surface of the lower resin layer 14a, the upper mold 32 is lowered again, and the lower resin layer 14a is moved downward. After pressing and holding for a predetermined time so that the metal plate 12 bites in, the upper mold 32 is raised. Thereby, the metal plate 12 is covered with the resin layer 14a, and the metal plate 12 is positioned.

  Then, as shown in FIG. 5C, the remaining half of the resin material is placed on the metal plate 12 and the resin layer 14a, and final pressing is performed. That is, the upper mold 32 is lowered and pressed and held for a predetermined time so that the resin material is uniformly filled to the upper corners of the lower mold 30. As a result, the metal plate 12 is covered with the resin layer 14 b, and the resin layer 14 a and the resin layer 14 b are integrated (fused) at the peripheral edge, thereby sealing the entire surface of the metal plate 12. Is formed. Moreover, the stress dispersion | distribution part 20 is formed in the surface (upper surface) of the upper resin layer 14b by the protrusion part 32a.

  Finally, after the press-molded protective plate 10 is taken out from the lower mold 30, the generated burrs are appropriately removed by a cutter or the like, and the protective plate 10 is cooled in a water tank or naturally cooled in the atmosphere, The manufacturing operation of the protection plate 10 is finished.

  As shown in FIG. 6, such a protection plate 10 is embedded side by side in the ground above the embedded pipeline 100 so that the end surfaces on the long side of adjacent protection plates 10 abut each other. As a result, when excavation work is performed in the vicinity of the buried pipeline 100 using, for example, an earth auger-type building pillar machine, the auger head (drilling drill) of the building pillar machine is buried in the buried pipe protection plate 10. Even if the metal plate 12 is touched, the metal plate 12 stops the auger head. Then, the excavation work is interrupted when the operator of the building pillar machine senses an abnormality such as, for example, the building pillar machine floating. For example, when excavation work is performed using a boring machine, even if the tip of the rod of the boring machine comes into contact with the buried duct protection plate 10, the tip of the rod is blocked by the resin layer 14, and a hole is formed. The difficulty of raising the water pressure of the boring machine. The drilling operation is interrupted when the operator of the boring machine feels abnormalities in the increase of the water supply pressure.

  That is, even when excavation work is performed around the buried pipeline 100 in order to construct a new underground object, the excavator (building column) can be obtained by burying the protective plate 10 above the buried pipeline 100. The progress of the machine auger head) can be prevented, or the operator can be made aware of the existence of the buried pipe 100, so that the situation where the buried pipe 100 is damaged can be prevented.

  According to this embodiment, the stress dispersion portion 20 is formed in the resin layer 14, and stress concentrated on the resin layer 14 at the upper and lower positions of the peripheral edge 12 a of the metal plate 12 is released to the stress dispersion portion 20. 14 can be prevented appropriately.

  Further, according to this embodiment, the surface of the central portion of the resin layer 14 is formed flush with the inner edge 20b in the thickness direction of the stress dispersion portion 20, that is, the thickness of the central portion of the resin layer 14 is the peripheral portion. Therefore, the amount of resin forming the resin layer 14 can be reduced. Therefore, the material cost can be reduced and the protective plate 10 can be reduced in weight.

  In the above-described embodiment, the stress dispersion portion 20 is formed in an inclined shape whose surface is the inclined surface 20a. However, the present invention is not limited to this. For example, as shown in FIG. 7, the stress distribution part 20 can also be formed in a step shape. In the embodiment shown in FIG. 7, the stress dispersion portion 20 becomes thin in a step shape toward the center side of the resin layer 14, and the surface of the stress dispersion portion 20 is formed by a vertical surface 20 c and a horizontal surface 20 d. The surface of the central portion of the resin layer 14 is formed flush with the horizontal surface 20d that is the inner edge of the stress dispersion portion 20 in the thickness direction.

  Further, as in the embodiment shown in FIG. 8, the notch portion in which the thickness of the resin layer 14 is smaller than the thickness at the peripheral edge 12 a of the metal plate 12 with respect to the peripheral edge corner portion of the resin layer 14. 22 can also be formed. The notch 22 is formed in, for example, an inclined shape or a step shape that becomes thinner toward the side surface of the resin layer 14. This notch portion 22 functions as a second stress dispersion portion that releases stress concentrated on the resin layer 14 at the upper and lower positions of the peripheral edge 12a of the metal plate 12 to itself. By providing such a notch 22 in the resin layer 14, the stress of the resin layer 14 at the vertical position of the peripheral edge 12 a of the metal plate 12 can be more appropriately dispersed.

  Furthermore, although illustration is omitted, the peripheral portion of the resin layer 14 may be formed in a circular cross section with the peripheral edge 12 a of the metal plate 12 as the center. Thereby, the stress of the resin layer 14 at the vertical position of the peripheral edge 12a of the metal plate 12 can be more appropriately dispersed. When the peripheral portion of the resin layer 14 is formed in a circular cross section, the inner surface portion functions as the stress dispersion portion 20 and the outer surface portion functions as the second stress distribution portion.

  Further, in each of the above-described embodiments, the surface of the central portion of the resin layer 14 is formed flush with the inner edge 20b in the thickness direction of the stress dispersion portion 20, but the present invention is not limited to this. As in the embodiment shown in FIG. 9, a convex portion 24 that is thicker than the inner edge 20 b portion of the stress dispersion portion 20 may be formed in the central portion of the resin layer 14 inside the stress dispersion portion 20. That is, in the embodiment shown in FIG. 9, the resin layer 14 has a rectangular frame-shaped groove portion 26 extending along the peripheral edge 12 a of the metal plate 12 at a position inside the peripheral edge 12 a of the metal plate 12. It is formed. The outer side surface portion of the groove portion 26 functions as the stress dispersion portion 20.

  In the embodiment having the groove portion 24 as shown in FIG. 9, the inventors analyzed the stress generated in the resin layer 14 in the same manner as in the above-described embodiment. Here, except for the thickness of the protective plate 10 at the central portion (the convex portion 24 portion) being 50 mm, the same dimensional conditions as those in the first embodiment shown in Table 1 are used, and the width of the horizontal surface of the groove portion 24 is changed. Analysis was performed.

  As a result, in any of the examples, the stress on the surface P immediately above the peripheral edge 12a of the metal plate 12 was 0.8 MPa or less. Specifically, when the width of the horizontal surface of the groove portion 24 is 0 mm, that is, when the groove portion 24 has a V-shaped cross-sectional shape, the stress on the immediately upper surface P was 0.8 MPa. When the width of the horizontal surface of the groove 24 is 100 mm, the stress on the upper surface P is 0.7 MPa. When the width of the horizontal surface of the groove 24 is 200 mm, the stress of the upper surface P is 0.6 MPa. there were.

  From the above, also in the embodiment shown in FIG. 9, the stress on the surface P can be efficiently reduced by releasing the stress to the stress dispersion portion 20, and the cracking of the resin layer 14 can be appropriately prevented. I understand that. Further, as the width of the horizontal surface of the groove portion 24 is increased, the stress dispersion effect by the stress dispersion portion 20 is increased. Therefore, in order to maximize the stress dispersion effect by the stress dispersion portion 20, FIG. It can be said that it is preferable to form the surface of the central portion of the resin layer 14 flush with the inner edge 20b in the thickness direction of the stress dispersion portion 20 as in the embodiment.

  In the embodiment shown in FIG. 9, the thickness at the central portion (protruding portion 24 portion) of the protective plate 10 and the thickness at the peripheral portion are set to the same size. Further, it can be set smaller than the thickness at the peripheral portion. For example, the thickness of the central portion of the protection plate 10 can be 45 mm, and the thickness of the peripheral portion can be 50 mm.

  Furthermore, in each above-mentioned Example, although the metal plate 12 was formed in the rectangular thin plate shape by the rolled steel material for general structures (SS400) based on JIS-G3101, it does not need to be limited to this. The metal plate 12 may be a metal plate having the same degree of rigidity as the steel material. For example, although not shown, the metal plate 12 having a gap such as a punching metal or an expanded metal can be used. By using the metal plate 12 having a gap, when the protective plate 10 is press-molded, the lower resin layer 14a and the upper resin layer 14b are integrated through the gap, so the protective plate 10 Can be molded more firmly. Further, R may be attached to the corner (corner) of the metal plate 12.

  The waste plastic (or unused resin) forming the resin layer 14 may be mixed with fiber bodies such as glass fibers and carbon fibers. As a result, the thermal expansion coefficient (expansion / contraction amount) of the resin layer 14 is reduced, that is, the difference in thermal expansion coefficient between the metal plate 12 and the resin layer 14 is reduced. Can be prevented more reliably. At this time, when the ratio of mixing the fibrous body with respect to the waste plastic is less than 5% by weight, the effect of reducing the thermal expansion / contraction rate of the resin layer 14 is low, and when it exceeds 20% by weight, the boring machine This makes it difficult to block the tip of the rod and reduces the cost of raw materials. For this reason, it is preferable that the ratio of the fiber body mixed with the waste plastic which forms the resin layer 14 shall be 5 to 20 weight%.

  It should be noted that the specific numerical values such as the dimensions mentioned above are merely examples, and can be appropriately changed according to the needs of product specifications and the like.

DESCRIPTION OF SYMBOLS 10 ... Buried line protection board 12 ... Metal plate 14 ... Resin layer 20 ... Stress distribution part 100 ... Buried pipe line

Claims (2)

A buried pipe protection plate buried above the buried pipe to protect an existing buried pipe buried in the ground,
A metal plate, and a resin layer that seals the entire surface of the metal plate,
The resin layer may possess inside than the peripheral edge of the metal plate, the stress dispersion portion formed by reducing the thickness of the resin layer,
The length W of the resin layer from the outer edge of the stress dispersion portion to the side surface of the buried pipe protection plate is 35 mm or more and 100 mm or less, and the side surface of the buried pipe protection plate from the peripheral edge of the metal plate The buried pipe protection plate having a length FW of the resin layer up to 25 mm and smaller than the length W.   The buried pipe protection plate according to claim 1, wherein a surface of a central portion of the resin layer is formed flush with an inner edge in a thickness direction of the stress dispersion portion.