Pipe joint for underground laying and method of laying underground pipe

Abstract

To impart high bending resistance to piping at a low cost.SOLUTION: An underground laying pipe joint comprising: a cylindrical large-diameter portion extending in an axial direction; a cylindrical small-diameter portion having a diameter smaller than a diameter of the large-diameter portion and extending in the axial direction; and a deformation guiding portion connecting the large-diameter portion and the small-diameter portion, the deformation guiding portion being more deformable than other portions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a pipe joint for underground installation and a method for installing underground piping. [Background technology]

[0002] Patent Document 1 discloses a steel pipe that can absorb fault displacement. Patent Document 2 discloses a pipeline that can absorb fault displacement. Patent Document 3 discloses a pipe body with high deformation absorption capacity that can withstand large-scale earthquakes and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-230107 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-230106 [Patent Document 3] Japanese Patent Application Publication No. 10-332071 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a pipe joint for underground installation and a method for installing underground pipes that can impart high bending resistance to pipes at low cost. [Means for solving the problem]

[0005] [1] A pipe joint for underground installation, comprising: a cylindrical large-diameter portion extending in the axial direction; a cylindrical small-diameter portion extending in the axial direction and having a diameter smaller than that of the large-diameter portion; and a deformation guide portion connecting the large-diameter portion and the small-diameter portion and being more easily deformed than other portions.

[0006] [2] A pipe joint for underground installation as described in [1] above, in which a straight pipe to be laid underground is connected to the small diameter portion, and the diameter of the small diameter portion is approximately the same as the diameter of the straight pipe.

[0007] [3] The deformation guide portion has a first connecting portion connected to the large diameter portion, a second connecting portion connected to the small diameter portion, and an intermediate portion connecting the first connecting portion and the second connecting portion, and in a vertical cross section including the central axis of the large diameter portion, the first connecting portion smoothly connects the large diameter portion and the intermediate portion in a curved line, and the second connecting portion smoothly connects the intermediate portion and the small diameter portion in a curved line, in the pipe joint for underground installation described in [1] or [2] above.

[0008] [4] In the longitudinal cross section, the first connecting portion is curved so as to protrude outward, and the second connecting portion is curved so as to protrude inward, and the first connecting portion and the second connecting portion are located between the outer peripheral surface of the large diameter portion and the inner peripheral surface of the small diameter portion, in the pipe joint for underground installation described in [3] above.

[0009] [5] The pipe joint for underground installation described in [3] above, wherein the radius of curvature of the first connection portion and the radius of curvature of the second connection portion are each 0.15 times or more the difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion.

[0010] [6] The underground pipe joint according to any one of [1] to [5] above, wherein the difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion is 150 mm or more.

[0011] [7] The underground pipe joint according to [6] above, wherein the difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion is 350 mm or less.

[0012] [8] A pipe joint for underground installation as described in any one of [1] to [7] above, comprising a pair of deformation guiding portions, one of the pair of deformation guiding portions being connected to one end of the large diameter portion in the axial direction, and the other of the pair of deformation guiding portions being connected to the other end of the large diameter portion in the axial direction.

[0013] [9] A pipe joint for underground installation according to [1] or [2] above, wherein the deformation guide portion is formed from a material that is more easily deformed than other portions.

[0014]

[10] A method for laying underground piping, comprising an arrangement step of arranging a plurality of pipe fittings to match the underground shape, wherein each of the plurality of pipe fittings has a cylindrical large diameter portion extending in the axial direction, a cylindrical small diameter portion extending in the axial direction and having a diameter smaller than the diameter of the large diameter portion, and a deformation guide portion connecting the large diameter portion and the small diameter portion and being more easily deformed than other portions, and each of the plurality of pipe fittings has a pair of the deformation guide portions, one of the pair of deformation guide portions being connected to one end of the large diameter portion in the axial direction, and the other of the pair of deformation guide portions being connected to the other end of the large diameter portion in the axial direction.

[0015]

[11] The method for laying underground pipes described in

[10] above, further comprising a setting step for determining the length of pipe between adjacent pipe fittings among the plurality of pipe fittings in accordance with the underground shape, and in the placement step, the plurality of pipe fittings are placed in accordance with the results determined in the setting step. [Effects of the Invention]

[0016] According to the present disclosure, there are provided an underground pipe joint and an underground pipe laying method that can impart high bending resistance to pipes at low cost. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of underground piping. [Figure 2] FIG. 2 is a perspective view showing an example of an underground pipe joint. [Figure 3] Fig. 3(a) is a side view showing an example of a pipe joint for underground installation, Fig. 3(b) is a cross-sectional view taken along line BB in Fig. 3(a), and Fig. 3(c) is a front view showing an example of a pipe joint for underground installation. [Figure 4] FIG. 4 is a diagram showing a vertical cross section taken along line IV-IV in FIG. 3(a). [Figure 5] FIG. 5 is an enlarged view of a part of FIG. [Figure 6]FIG. 6 is an enlarged view of a portion of a vertical cross section of a modified underground pipe joint. [Figure 7] Fig. 7(a) is a side view showing a modified pipe joint for underground installation, and Fig. 7(b) is an enlarged view of a portion of a longitudinal cross section of the modified pipe joint for underground installation. [Figure 8] 8(a) and 8(b) are diagrams for explaining the verification by simulation. [Figure 9] FIG. 9 is a diagram for explaining the verification by simulation. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment will be described below with reference to the drawings. In the description, the same elements or elements having the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0019] [Underground piping and pipe fittings] Fig. 1 shows a schematic diagram of an underground pipe according to one embodiment. The underground pipe 1 shown in Fig. 1 is a pipe laid underground below the ground surface G0. The underground pipe 1 constitutes at least a part of a pipeline for transporting a fluid such as water or gas, and forms a conduit through which the fluid flows. The underground pipe 1 is installed according to the underground shape, and is, for example, arranged substantially parallel to the ground surface G0.

[0020] The underground pipe 1 crosses a fault (active fault) that exists underground. The underground pipe 1 crosses a fault plane G1 that exists underground. When the fault moves, that is, when fault displacement occurs, bending deformation occurs in the pipeline near the fault plane G1. The underground pipe 1 is provided with a portion that can absorb bending deformation that may occur due to fault displacement. Regardless of the type of displacement, such as a normal fault, a reverse fault, a right-lateral strike-slip fault, or a left-lateral strike-slip fault, the underground pipe 1 (a specific portion of the underground pipe 1) may be configured to be able to absorb bending deformation.

[0021] The underground piping 1 includes, for example, a straight pipe 10A (first straight pipe), a pipe joint 20A (first pipe joint), a straight pipe 10B (second straight pipe), a pipe joint 20B (second pipe joint), and a straight pipe 10C (third straight pipe). The straight pipe 10A, the pipe joint 20A, the straight pipe 10B, the pipe joint 20B, and the straight pipe 10C are arranged in this order from upstream or downstream. In one example, the straight pipe 10A, the pipe joint 20A, the straight pipe 10B, the pipe joint 20B, and the straight pipe 10C are individually transported to an underground installation position and then welded to form a single pipeline. The following description will be given assuming that the straight pipe 10A is located most upstream among the straight pipe 10A, the pipe joint 20A, the straight pipe 10B, the pipe joint 20B, and the straight pipe 10C.

[0022] The straight pipes 10A, 10B, and 10C are each formed to extend linearly. The straight pipes 10A, 10B, and 10C have the same diameter. The outer diameter of the straight pipe 10A is, for example, 500 mm to 3000 mm, more preferably 700 mm to 2500 mm, and even more preferably 800 mm to 2200 mm.

[0023] Each of the pipe joints 20A and 20B, which will be described in detail later, is a pipe joint for underground installation configured to absorb bending deformation caused by fault displacement. The pipe joints 20A and 20B are arranged with the fault plane G1 sandwiched between them. The pipe joints 20A and 20B may be arranged so that the difference between the distance between the pipe joint 20A and the fault plane G1 and the distance between the pipe joint 20B and the fault plane G1 falls within a predetermined range. The distance between the pipe joint 20A and the fault plane G1 and the distance between the pipe joint 20B and the fault plane G1 may be approximately the same.

[0024] One downstream end of the straight pipe 10A is connected to one upstream end of the pipe fitting 20A, and one upstream end of the straight pipe 10B is connected to one downstream end of the pipe fitting 20A. One downstream end of the straight pipe 10B is connected to one upstream end of the pipe fitting 20B, and one upstream end of the straight pipe 10C is connected to one downstream end of the pipe fitting 20B. The ends of the straight pipes and the pipe fittings are connected by welding. The pipe fittings 20A and 20B may have the same shape. Below, it is assumed that the pipe fittings 20A and 20B have the same shape, and the pipe fitting 20A will be described in detail.

[0025] Fig. 2 shows a perspective view of pipe fitting 20A. Fig. 3(a) shows a side view of pipe fitting 20A, Fig. 3(b) shows a cross section taken along line BB in Fig. 3(a), and Fig. 3(c) shows a front view of pipe fitting 20A.

[0026] As shown in FIG. 2, the pipe fitting 20A is formed in a cylindrical shape. When the pipe fitting 20A is cut and observed along a plane perpendicular to the central axis Ax of the pipe fitting 20A, the cut surface is annular. The central axis Ax is an imaginary axis that passes through the center of the flow path formed by the pipe fitting 20A in a cross section of the pipe fitting 20A (a cross section perpendicular to the flow direction in the flow path). The central axis Ax is sometimes referred to as the pipe axis. The pipe fitting 20A is axisymmetric about the central axis Ax. In the present disclosure, the axial direction in which the central axis Ax extends is referred to as the "direction D1." In some drawings, such as FIG. 2, the direction from upstream to downstream in the direction D1 is indicated by "D11," and the direction from downstream to upstream is indicated by "D12." The pipe fitting 20A may be plane-symmetric with respect to an imaginary plane that passes through the center (center) in the direction D1 and is perpendicular to the direction D1.

[0027] As shown in Figures 2 and 3(a), the pipe fitting 20A includes a large diameter portion 30, a pair of small diameter portions 40, and a pair of deformation guides 50. One small diameter portion 40 is connected to one upstream end of the large diameter portion 30 in the direction D1 via one deformation guide 50, and another small diameter portion 40 is connected to one downstream end of the large diameter portion 30 in the direction D1 via another deformation guide 50. In the pipe fitting 20A, the large diameter portion 30, the pair of small diameter portions 40, and the pair of deformation guides 50 may be connected and integrated by welding. Instead of welding, the large diameter portion 30, the pair of small diameter portions 40, and the pair of deformation guides 50 may be integrated by other methods such as casting.

[0028] The large diameter portion 30, the pair of small diameter portions 40, and the pair of deformation guide portions 50 may be formed of the same material. The pipe fitting 20A, which is configured by integrating the large diameter portion 30, the pair of small diameter portions 40, and the pair of deformation guide portions 50, may be made of steel (steel pipe). The plate thicknesses of the large diameter portion 30, the pair of small diameter portions 40, and the pair of deformation guide portions 50 may be the same.

[0029] Hereinafter, to distinguish between the pair of small diameter portions 40, the small diameter portion 40 arranged on one end side (upstream side) of the large diameter portion 30 may be referred to as the "small diameter portion 40a," and the small diameter portion 40 arranged on the other end side (downstream side) of the large diameter portion 30 may be referred to as the "small diameter portion 40b." Furthermore, to distinguish between the pair of deformation guides 50, the deformation guide portion 50 arranged on the one end side (upstream side) of the large diameter portion 30 may be referred to as the "deformation guide portion 50a," and the deformation guide portion 50 arranged on the other end side (downstream side) of the large diameter portion 30 may be referred to as the "deformation guide portion 50b." When observed along direction D1, the small diameter portion 40a (first small diameter portion), the deformation guide portion 50a (first deformation guide portion), the large diameter portion 30, the deformation guide portion 50b (second deformation guide portion), and the small diameter portion 40b (second small diameter portion) are arranged in this order.

[0030] The large diameter portion 30 is a cylindrical portion extending in direction D1 (axial direction). Being cylindrical and extending in direction D1 means that the cross-sectional shape perpendicular to direction D1 remains constant even if the position in direction D1 changes. As shown in FIG. 3(b), when a cross section of the large diameter portion 30 perpendicular to direction D1 is observed at an arbitrary position in direction D1, the cross-sectional shape of the large diameter portion 30 is annular. The large diameter portion 30 is symmetrical with respect to the central axis Ax. The central axis Ax (the central axis of the pipe fitting 20A) is also the central axis of the large diameter portion 30.

[0031] The diameter of the large diameter portion 30 may be larger than the diameter of the straight pipe 10A. In this disclosure, when the relationship between the "diameter" of one part constituting a pipe and the "diameter" of another part is defined, this relationship applies to both the outer diameter and the inner diameter. The relationship also includes a relationship in which the sizes of the two parts are the same.

[0032] Each of the pair of small diameter portions 40 has a diameter smaller than the diameter of the large diameter portion 30 and is a cylindrical portion extending in direction D1. The inner diameter of the small diameter portion 40 is smaller than the inner diameter of the large diameter portion 30, and the outer diameter of the small diameter portion 40 is smaller than the outer diameter of the large diameter portion 30. As also shown in FIG. 3(c), when a cross section of the small diameter portion 40 perpendicular to direction D1 is observed at an arbitrary position in direction D1, the cross-sectional shape of the small diameter portion 40 is annular. The small diameter portion 40 is axially symmetric with respect to the central axis Ax.

[0033] One end of the small diameter portion 40a in the direction D1 is connected to a straight pipe 10A to be laid underground. The diameter of the small diameter portion 40a may be approximately the same as the diameter of the straight pipe 10A. One end of the small diameter portion 40b in the direction D1 is connected to a straight pipe 10B to be laid underground. The diameter of the small diameter portion 40b may be approximately the same as the diameter of the straight pipe 10B. "The diameters are approximately the same" means that one diameter is 0.95 to 1.05 times the diameter of the other, with respect to both the outer diameter and the inner diameter.

[0034] Each of the pair of deformation guides 50 connects the large diameter portion 30 and the small diameter portion 40, and is more easily deformed than other portions. The deformation guides 50 are more easily deformed than the large diameter portion 30 and the small diameter portion 40, which are the other portions of the pipe fitting 20A. In this case, when an external force acts on the underground pipe 1 including the pipe fitting 20A, the deformation guides 50 deform before the large diameter portion 30 and the small diameter portion 40. The deformation guides 50a connect the large diameter portion 30 and the small diameter portion 40a, and the deformation guides 50b connect the large diameter portion 30 and the small diameter portion 40b.

[0035] The deformation guide 50a connects the end of the small diameter portion 40a opposite to the end to which the straight pipe 10A is connected, and one end of the large diameter portion 30 in the direction D1. The deformation guide 50a and the small diameter portion 40a are connected by welding, and the deformation guide 50a and the large diameter portion 30 are connected by welding. The deformation guide 50b connects the end of the small diameter portion 40b opposite to the end to which the straight pipe 10B is connected, and the other end of the large diameter portion 30 in the direction D1. The deformation guide 50b and the small diameter portion 40b are connected by welding, and the deformation guide 50b and the large diameter portion 30 are connected by welding.

[0036] When observing the deformation inducing portion 50 from the connection point with the small diameter portion 40 toward the connection point with the large diameter portion 30, the diameter of the deformation inducing portion 50 (the size of the flow path formed by the deformation inducing portion 50) gradually increases. Focusing on the shape of the deformation inducing portion 50, the deformation inducing portion 50 can also be referred to as an "expanding diameter portion." The deformation inducing portion 50 is axially symmetric with respect to the central axis Ax. The detailed shape of the deformation inducing portion 50 will be described later.

[0037] 4 shows a cross section (hereinafter simply referred to as a "longitudinal cross section") of the pipe fitting 20A cut along an arbitrary plane including the central axis Ax. In FIG. 4, "r1" represents the outer diameter of the large diameter portion 30, and "r2" represents the outer diameter of the small diameter portion 40. From the viewpoint of reducing the degree of plastic strain when the piping is deformed due to fault displacement, the difference between the outer diameter r1 and the outer diameter r2 (r1-r2) may be 150 mm or more. The difference between the outer diameter r1 and the outer diameter r2 (r1-r2) may be 160 mm or more, 170 mm or more, or 180 mm or more.

[0038] From the viewpoint of reducing the space required for embedding the pipe fitting 20A, the difference (r1-r2) between the outer diameter r1 and the outer diameter r2 may be 350 mm or less. The difference (r1-r2) between the outer diameter r1 and the outer diameter r2 may be 340 mm or less, 330 mm or less, or 320 mm or less. For example, the difference (r1-r2) between the outer diameter r1 and the outer diameter r2 is 150 mm to 350 mm, more preferably 160 mm to 340 mm, and even more preferably 180 mm to 320 mm.

[0039] In FIG. 4, "l1" represents the length of the large diameter portion 30 in the direction D1, "l2" represents the length of the small diameter portion 40 in the direction D1, and "l3" represents the length of the deformation guide portion 50 in the direction D1. The length l1 may be 800 mm to 1200 mm, 850 mm to 1150 mm, or 900 mm to 1100 mm. The length l2 may be approximately the same as the length l1, or may be shorter or longer than the length l1. The length l3 may be 0.05 to 0.2 times the length l1, 0.08 to 0.18 times the length l1, or 0.1 to 0.15 times the length l1.

[0040] Fig. 5 shows an enlarged view of the portion indicated by V in the longitudinal cross section of Fig. 4. As shown in Fig. 5, the deformation guide portion 50b (deformation guide portion 50) may be divided into three portions: a first connecting portion 52, a second connecting portion 54, and an intermediate portion 56. The first connecting portion 52 is a portion connected to the large diameter portion 30 and is cylindrical. The second connecting portion 54 is a portion connected to the small diameter portion 40b (small diameter portion 40) and is cylindrical. The intermediate portion 56 is a portion connecting the first connecting portion 52 and the second connecting portion 54 and is cylindrical.

[0041] Below, we will explain the detailed shapes of the first connecting portion 52, the second connecting portion 54, and the intermediate portion 56 when observing the longitudinal cross section. In the longitudinal cross section (see FIG. 4), two portions sandwiching the central axis Ax are observed as cross-sectional shapes, but the explanation will focus on only one of the two portions. In FIG. 5, "B1" represents the boundary between the first connecting portion 52 and the intermediate portion 56, and "B2" represents the boundary between the second connecting portion 54 and the intermediate portion 56. In the longitudinal cross section, the direction perpendicular to direction D1 is referred to as "direction D2." A direction (direction) approaching the central axis Ax is referred to as "inside" or "inner side," and a direction (direction) moving away from the central axis Ax is referred to as "outside" or "outer side."

[0042] The intermediate portion 56 is inclined in both directions D1 and D2 and extends linearly in one direction. The angle formed between direction D1 and the intermediate portion 56 (the extension direction of the intermediate portion 56) may be 30° to 60°, 35° to 55°, or 40° to 50°. In one example, the angle formed between direction D1 and the extension direction of the intermediate portion 56 is 45°. In direction D2, the entire intermediate portion 56 is located between the inner circumferential surface of the large diameter portion 30 and the outer circumferential surface of the small diameter portion 40b.

[0043] The first connecting portion 52 smoothly connects the large diameter portion 30 and the intermediate portion 56 in a curved shape. The first connecting portion 52 is curved so as to protrude outward. The first connecting portion 52 may be an arc, and its center position (the center position of a circle containing the arc) is located inside the pipe fitting 20A. The radius of curvature of the first connecting portion 52 may be 0.15 or more times the difference (r1-r2) between the outer diameter r1 and the outer diameter r2. In one example, the radius of curvature of the first connecting portion 52 is 40 mm or more, preferably 45 mm or more, and more preferably 50 mm or more. The radius of curvature of the first connecting portion 52 may be 150 mm or less.

[0044] The second connecting portion 54 smoothly connects the intermediate portion 56 and the second connecting portion 54 in a curved manner. The second connecting portion 54 is curved so as to protrude inward. The second connecting portion 54 may be an arc, and its center position (the center position of a circle including the arc) is located outside the pipe fitting 20A. The radius of curvature of the second connecting portion 54 may be 0.15 or more times the difference (r1-r2) between the outer diameter r1 and the outer diameter r2. For example, the radius of curvature of the second connecting portion 54 is 40 mm or more, 45 mm or more, or 50 mm or more. The radius of curvature of the second connecting portion 54 may be 150 mm or less. The radius of curvature of the second connecting portion 54 may be the same as the radius of curvature of the first connecting portion 52.

[0045] The first connecting portion 52 and the second connecting portion 54 are located between the outer peripheral surface of the large diameter portion 30 and the inner peripheral surface of the small diameter portion 40b. In direction D1, the entire first connecting portion 52 is located between the outer peripheral surface of the large diameter portion 30 and the inner peripheral surface of the small diameter portion 40b (or the outer peripheral surface of the small diameter portion 40b). In FIG. 5, the dashed line indicated by "IL1" represents the cross-sectional shape when it is assumed that the connection is made not by the first connecting portion 52 but by an extension portion extending linearly from the large diameter portion 30 and an extension portion extending linearly from the intermediate portion 56. The first connecting portion 52 is curved so as to be located inside the outer edge of the portion indicated by the dashed line IL1.

[0046] In direction D1, the entire second connecting portion 54 is located between the outer peripheral surface of large diameter portion 30 (or the inner peripheral surface of large diameter portion 30) and the inner peripheral surface of small diameter portion 40b. In Fig. 5, the dashed line indicated by "IL2" represents the cross-sectional shape when it is assumed that the connection is made not by second connecting portion 54 but by an extension portion extending linearly from small diameter portion 40b and an extension portion extending linearly from intermediate portion 56. Second connecting portion 54 is curved so as to be located outside the inner edge of the portion indicated by dashed line IL2.

[0047] As described above, when the shape of the pipe fitting 20A is plane-symmetric with respect to an imaginary plane that passes through the center in the direction D1 and is perpendicular to the direction D1, the longitudinal cross section of the pipe fitting 20A is line-symmetric with respect to an imaginary line corresponding to the imaginary plane. In this case, the deformation guide portion 50a has the same shape as the deformation guide portion 50b, although it is inverted with respect to the imaginary plane (imaginary line).

[0048] The pipe fittings described above are just examples. In pipe fitting 20A and pipe fitting 20B, the axial lengths (length l2) of small diameter portions 40a and 40b may be different from each other. The dimensions of a portion of pipe fitting 20A and the dimensions of a portion of pipe fitting 20B may be different from each other.

[0049] Fig. 6 shows a portion of a pipe fitting according to a modified example. The underground piping 1 may be provided with a pipe fitting 20C shown in Fig. 6 instead of each of the pipe fittings 20A and 20B. The pipe fitting 20C (a pipe fitting for underground installation) differs from the pipe fitting 20A in that it is provided with a pair of deformation guides 60 instead of the pair of deformation guides 50. Fig. 6 shows a portion of the longitudinal cross section of the pipe fitting 20C corresponding to the enlarged view in Fig. 5. The deformation guides 60 are axially symmetrical with respect to the central axis Ax, similar to the deformation guides 50.

[0050] The deformation guide portion 60 is divided into five portions: a first straight portion 62, a first convex portion 63, an intermediate portion 66, a second convex portion 65, and a second straight portion 64. When observed from the large diameter portion 30 toward the small diameter portion 40b, the first straight portion 62, the first convex portion 63, the intermediate portion 66, the second convex portion 65, and the second straight portion 64 are arranged in this order. Below, the shapes of these five portions in vertical cross section will be described.

[0051] The intermediate portion 66 is a portion corresponding to the intermediate portion 56 of the deformation guide portion 50. The first straight portion 62 extends linearly in the direction D1, and one end thereof is connected to the large diameter portion 30. The first convex portion 63 connects the first straight portion 62 and the intermediate portion 66. The first convex portion 63 (more specifically, most of the first convex portion 63) is curved so as to protrude inward. The curved portion of the first convex portion 63 protruding inward may be an arc, and the radius of curvature may be 10 mm to 20 mm.

[0052] The second straight portion 64 extends linearly in the direction D1, and one end thereof is connected to the small diameter portion 40b. The second convex portion 65 connects the intermediate portion 66 and the second straight portion 64. The second convex portion 65 (more specifically, most of the second convex portion 65) is curved so as to protrude outward. The curved portion of the second convex portion 65 that protrudes outward may be an arc, and the radius of curvature may be 10 mm to 20 mm.

[0053] FIG. 7(a) shows a pipe fitting according to another modification. The underground piping 1 may include a pipe fitting 20D shown in FIG. 7(a) instead of the pipe fittings 20A and 20B, or instead of each of the pipe fittings 20A and 20B. The pipe fitting 20D (a pipe fitting for underground installation) includes two large diameter portions 30, two sets of deformation guides 50 corresponding to the two large diameter portions 30, a pair of small diameter portions 40, and a connecting portion 48. One small diameter portion 40 is connected to one of the pair of deformation guides 50 connected to both ends of one large diameter portion 30, and the connecting portion 48 is connected to the other of the pair of deformation guides 50. Another small diameter portion 40 is connected to one of the pair of deformation guides 50 connected to both ends of another large diameter portion 30, and the connecting portion 48 is connected to the other of the pair of deformation guides 50. The connecting portion 48 has a shape similar to that of the small diameter portion 40 .

[0054] Fig. 7(b) shows a portion of a pipe fitting according to another modification. The underground piping 1 may be provided with the pipe fitting 20E shown in Fig. 7(b) instead of the pipe fittings 20A and 20B, or instead of each of the pipe fittings 20A and 20B. The pipe fitting 20E (a pipe fitting for underground installation) differs from the pipe fitting 20A in that it is provided with a pair of deformation guides 70 instead of the pair of deformation guides 50. Fig. 7(b) shows a portion of the vertical cross section of the pipe fitting 20E corresponding to the enlarged view in Fig. 5.

[0055] The deformation guide 70, like the deformation guide 50, is axially symmetrical with respect to the central axis Ax. In the pipe fitting 20E, the material forming the deformation guide 70 is different from the material forming the large diameter portion 30 and the small diameter portion 40. Each of the pair of deformation guides 70 is formed from a material that is more easily deformed than the other portions (the large diameter portion 30 and the small diameter portion 40). The material of the deformation guide 70 may be selected so that the hardness of the deformation guide 70 is less than the hardness of the large diameter portion 30 and the small diameter portion 40. The material of the deformation guide 70 may be selected by comparing an index value related to ease of deformation other than hardness (for example, Young's modulus).

[0056] At least one of the pipe fittings 20A and 20B may have a single deformation guide 70 instead of a pair of deformation guides 70. The single deformation guide 70 may be connected to either the upstream or downstream end of the large diameter portion 30. A connecting portion (a connecting portion that does not have the function of guiding deformation) that connects to the small diameter portion 40 or a straight pipe may be provided at one of the two ends of the large diameter portion 30 to which the deformation guide 70 is not connected. Similarly, the pipe fittings 20C and 20E may also have a single deformation guide instead of a pair of deformation guides. In the pipe fitting 20D, when focusing on one large diameter portion 30, a deformation guide 50 may be provided at only one end of the large diameter portion 30, rather than at both ends.

[0057] [Underground piping installation method] Next, an example of a method for laying underground pipe 1 (hereinafter referred to as "laying method") will be described. This laying method includes a placement step. The laying method may further include an integration step. The integration step is a step of preparing a pipe fitting by integrating large diameter portion 30, a pair of small diameter portions 40, and a pair of deformation guide portions 50. In the integration step, two or more pipe fittings (for example, pipe fitting 20A and pipe fitting 20B) are prepared.

[0058] The arranging process is a process of arranging multiple pipe fittings (e.g., pipe fitting 20A and pipe fitting 20B) to match the underground shape. In the arranging process, the pipe fittings are arranged in multiple stages. For example, each of pipe fitting 20A and pipe fitting 20B is transported to the location where it is to be laid and arranged at that location. In addition to the arranging process, each of straight pipe 10A, straight pipe 10B, and straight pipe 10C may be transported to the location where it is to be laid and arranged at that location. Thereafter, the straight pipes and the pipe fittings may be welded to form the underground piping 1.

[0059] The above-mentioned installation method may further include a setting step. The setting step is a step of determining the length of the pipe between adjacent pipe fittings (for example, between pipe fitting 20A and pipe fitting 20B) among the plurality of pipe fittings in accordance with the underground shape. The pipe length means the length on the pipe axis of the underground piping 1. For example, in the setting step, the length on the pipe axis between pipe fitting 20A and pipe fitting 20B is determined according to the position of a fault plane G1 in the underground shape. In the above-mentioned placement step, the plurality of pipe fittings (for example, pipe fitting 20A and pipe fitting 20B) may be placed according to the determination result in the setting step.

[0060] Various examples of pipe fittings, underground piping, and installation methods have been described above, but in one of the various examples described above, at least some of the matters described in other examples may be combined.

[0061] [Verification by simulation] The deformation state of the deformation guide portion of the underground pipe 1 in which the pipe fitting 20A or 20C is installed was confirmed and evaluated using FEM analysis (Finite Element Method analysis). The known software "Abaqus" was used for the simulation using FEM analysis. First, an analytical model M1 shown in FIG. 8(a) was prepared. The analytical model M1 is a model that simulates the underground pipe 1 in which the pipe fitting 20A or 20C is installed. The element type used in the analytical model M1 was "Solid." The number of nodes was 381,350, and the number of elements was 222,412.

[0062] The total length L1 of the analytical model M1 was 10 m, and the pipe fitting 20A or the pipe fitting 20C was placed at the center of the pipe axis. The length l1 of the large diameter portion 30 of the pipe fitting 20A or the pipe fitting 20C was 1000 mm. The outer diameter of the straight pipe such as the straight pipe 10A and the portion corresponding to the small diameter portion 40 (hereinafter referred to as the "main pipe") was 1000 mm. The material of the analytical model M1 was SS400, and the material constants of the analytical model M1, Young's modulus E, Poisson's ratio v, and shear modulus G, were set as follows: Young's modulus E=206,000N / mm 2 Poisson's ratio v=0.3 Shear modulus G = 79,230N / mm 2

[0063] One end of the analytical model M1 in the pipe axis direction was fixed, and a load F was applied to the other end, simulating the load associated with fault displacement. Load F was applied at an angle of 74° to the pipe axis direction, and was large enough to displace the other end of analytical model M1 in the pipe axis direction by 1,440 mm. 1,440 mm is a displacement amount that complies with the guidelines of the Japan Water Steel Pipe Association. Figure 8(b) shows analytical model M1 after being displaced by the application of load F. In Figure 8(b), the displacement distribution is indicated by shading. Colors closer to black indicate smaller displacement from the initial position, and colors closer to white indicate larger displacement from the initial position.

[0064] (Verification examples 1 to 6) In the analytical model M1 after displacement, the equivalent plastic strain was calculated for each element, and the maximum value of the equivalent plastic strain was used as the evaluation index. Verification was carried out in Verification Examples 1 to 6, which varied the type of pipe joint (shape of the deformation guide portion), the outer diameter r1 of the large diameter portion 30, and the radius of curvature of the curved portion in the deformation guide portion. The conditions for each of Verification Examples 1 to 6 and the calculation results of the evaluation index are shown in Table 1 below.

[0065] [Table 1]

[0066] In Table 1, the radius of curvature [mm] refers to the radius of curvature of the first connecting portion 52 and the second connecting portion 54 of the deformation guide portion 50 when the shape of the pipe fitting 20A is modeled, and refers to the radius of curvature of the first convex portion 63 and the second convex portion 65 of the deformation guide portion 60 when the shape of the pipe fitting 20C is modeled. The results shown in Table 2 show that the degree of strain generated is smaller when the shape of the pipe fitting 20A (deformation guide portion 50) is used compared to the shape of the pipe fitting 20C (deformation guide portion 60). It also shows that the degree of strain generated is smaller when the outer diameter r1 of the large diameter portion 30 is increased.

[0067] Based on the results of verification examples 1 to 4, further verification was carried out on the shape of the pipe fitting 20A (deformation guide portion 50). In accordance with the guidelines of the Japan Water Steel Pipe Association, it is necessary to place two pipe fittings with the fault plane G1 between them. Therefore, as shown in Figure 9, an analytical model M2 was prepared that simulates an underground pipe 1 in which pipe fittings 20A and 20B were installed. In analytical model M2, the conditions regarding the elements, material constants, applied load, and outer diameter of the main pipe were set to the same conditions as in analytical model M1.

[0068] The length l1 of the large diameter portion 30 of each of the pipe fittings 20A and 20B was set to 1000 mm, the same as in the analytical model M1. The diameter of the large diameter portion 30 of the pipe fitting 20A and the diameter of the large diameter portion 30 of the pipe fitting 20B were set to be the same size.

[0069] (Verification examples 7 to 18) Verification was performed in Verification Examples 7 to 18, in which the outer diameter r1 of the large diameter portion 30, the spacing between the deformation guides 50 of the pipe fittings 20A and 20B, and the radii of curvature of the first connecting portion 52 and the second connecting portion 54 were varied. The spacing between the deformation guides 50 of the pipe fittings 20A and 20B was determined by the shortest combination of one deformation guide 50 of the pipe fitting 20A and one deformation guide 50 of the pipe fitting 20B in the pipe axial direction. In Verification Examples 7 to 18, the distance between each end of the analysis model M2 and the nearest pipe fitting, either the pipe fitting 20A or the pipe fitting 20B, was kept constant, while the spacing between the deformation guides 50 of the pipe fittings 20A and 20B was varied. The conditions for Verification Examples 7 to 18 and the calculation results of the evaluation indexes are shown in Table 2 below.

[0070] [Table 2]

[0071] The verification results shown in Table 2 above show that by setting the difference between the outer diameter r1 and the outer diameter of the main pipe to 200 mm or 300 mm, the equivalent plastic strain is reduced to less than 37%, and the degree of strain generated is small. When the distance between the deformation guide portions 50 of the pipe fittings 20A and 20B is 2 m and 3 m, setting the difference between the outer diameter r1 and the outer diameter of the main pipe to 200 mm or 300 mm reduces the equivalent plastic strain to less than 30%, and the degree of strain generated is further reduced. It can be seen that by increasing the radius of curvature to 100 mm (i.e., by curving the first connecting portion 52 and the second connecting portion 54 more gently), the degree of strain generated tends to be smaller.

[0072] 9 shows an enlarged longitudinal cross section of the portion of the analytical model M2 after displacement indicated by the dashed line. As shown in the enlarged longitudinal cross section of FIG. 9, in all of Verification Examples 7 to 18, no contact occurred between the plates in the deformation induction section 50.

[0073] Summary of this disclosure The underground pipe joints (20A, 20B, 20C, 20D, 20E) described above comprise a cylindrical large diameter portion (30) extending in the axial direction (D1), a cylindrical small diameter portion (40) extending in the axial direction (D1) and having a diameter smaller than the diameter of the large diameter portion (30), and deformation guide portions (50, 60, 70) that connect the large diameter portion (30) and the small diameter portion (40) and are more easily deformed than other portions.

[0074] In underground pipes installed underground across a fault plane, fault displacement can cause bending deformation and breakage. In contrast, in the underground pipe joints (20A, 20B, 20C, 20D, 20E), the large-diameter section (30) and the small-diameter section (40) are connected by easily deformed deformation guides (50, 60, 70). By providing this pipe joint to an underground pipe (1), even if fault displacement occurs, the deformation guides (50, 60, 70) deform to absorb bending deformation occurring in the underground pipe (1), thereby reducing the possibility of pipe breakage. Because the pipe joint is composed of a cylindrical large-diameter section (30) and a cylindrical small-diameter section (40) with different diameters and a deformation guide (50, 60, 70) connecting these sections, it can be manufactured inexpensively. Therefore, it is possible to impart high bending resistance to the pipe at low cost.

[0075] In the above-described underground pipe joints (20A, 20B, 20C, 20D, 20E), the straight pipes (10A, 10B, 10C) to be laid underground may be connected to the small diameter portion 40. The diameter of the small diameter portion 40 may be approximately the same as the diameter of the straight pipes (10A, 10B, 10C). In this case, it is easy to connect the underground pipe joints to the straight pipes, and it is easy to install the underground pipe joints to form the underground piping 1.

[0076] In the underground pipe joint (20A, 20D) described above, the deformation guide portion (50) may have a first connection portion (52) connected to the large diameter portion (30), a second connection portion (54) connected to the small diameter portion (40), and an intermediate portion (56) connecting the first connection portion (52) and the second connection portion (54). In a vertical cross section including the central axis (Ax) of the large diameter portion (30), the first connection portion (52) may smoothly connect the large diameter portion (30) and the intermediate portion (56) in a curved line, and the second connection portion (54) may smoothly connect the intermediate portion (56) and the small diameter portion (30) in a curved line. As a result of the inventor's investigation, it was found that providing two smooth connecting portions between the large diameter portion 30 and the small diameter portion 40 can cause deformation between the large diameter portion 30 and the small diameter portion 40 and reduce the degree of strain that occurs. By configuring the deformation guide portion 50 as described above, it is possible to reduce the degree of strain while imparting high bending resistance to the piping.

[0077] In the underground pipe joints 20A, 20D described above, in the longitudinal cross section, the first connecting portion 52 may be curved so as to protrude outward, and the second connecting portion 54 may be curved so as to protrude inward, and the first connecting portion 52 and the second connecting portion 56 may be located between the outer circumferential surface of the large diameter portion 30 and the inner circumferential surface of the small diameter portion 40. In this case, it is possible to impart high bending resistance to the pipe while reducing the degree of strain that occurs.

[0078] In the underground pipe joints 20A, 20D described above, the radius of curvature of the first connection portion 52 and the radius of curvature of the second connection portion 54 may each be 0.15 times or more the difference (r1-r2) between the outer diameter (r1) of the large diameter portion 30 and the outer diameter (r2) of the small diameter portion 40. In this case, even if displacement due to fault displacement occurs in the underground pipe 1 in which the pipe joint is installed, the degree of strain that occurs can be reduced.

[0079] In the underground pipe joints (20A, 20B, 20C, 20D, 20E) described above, the difference (r1-r2) between the outer diameter (r1) of the large diameter portion (30) and the outer diameter (r2) of the small diameter portion (40) may be 150 mm or more. In this case, even if displacement due to fault displacement occurs in the underground pipe (1) in which the pipe joint is installed, the degree of strain that occurs can be reduced.

[0080] In the pipe joints for underground installation (20A, 20B, 20C, 20D, 20E) described above, the difference (r1-r2) between the outer diameter (r1) of the large diameter portion (30) and the outer diameter (r2) of the small diameter portion (40) may be 350 mm or less. In this case, the space required for installing the pipe joint provided with the large diameter portion and the deformation guide portion underground can be reduced.

[0081] The underground pipe joints (20A, 20B, 20C, 20E) described above may include a pair of deformation guides (50, 60, 70). One of the pair of deformation guides (50, 60, 70) may be connected to one end of the large diameter portion (30) in the axial direction (D1), and the other of the pair of deformation guides (50, 60, 70) may be connected to the other end of the large diameter portion (30) in the axial direction (D1). In this case, since the deformation guides (50, 60, 70) are provided at both ends of the large diameter portion (30), higher bending resistance can be imparted to the pipe.

[0082] In the underground pipe joint 20E described above, the deformation guide portion 70 may be formed of a material that is more easily deformed than the other portions 30, 40. In this case, even if a fault displacement occurs, the deformation guide portion 70 deforms before the other portions, and can absorb the bending deformation occurring in the underground pipe 1.

[0083] The above-described installation method is a method for installing an underground pipe (1). This installation method includes an arrangement step of arranging a plurality of pipe fittings (20A, 20B) according to the underground shape. Each of the plurality of pipe fittings (20A, 20B) has a cylindrical large-diameter portion (30) extending in the axial direction (D1), a cylindrical small-diameter portion (30) extending in the axial direction (D1) and having a diameter smaller than that of the large-diameter portion (30), and a deformation guide portion (50) connecting the large-diameter portion (30) and the small-diameter portion (40) and being more easily deformed than other portions. Each of the plurality of pipe fittings (20A, 20B) has a pair of deformation guide portions (50), one of which is connected to one end of the large-diameter portion (30) in the axial direction (D1), and the other of which is connected to the other end of the large-diameter portion (30) in the axial direction (D1). In this installation method, the above-mentioned pipe joints are arranged in multiple stages in the underground pipe 1. Therefore, it is possible to impart high bending resistance to the pipe at low cost.

[0084] The above-described installation method may further include a setting step of determining the length of pipe between adjacent pipe fittings among the plurality of pipe fittings (20A, 20B) in accordance with the underground shape. In the placement step, the plurality of pipe fittings (20A, 20B) may be placed in accordance with the determination result in the setting step. In this case, the plurality of pipe fittings (20A, 20B) can be more reliably installed at positions that match the underground shape. [Explanation of symbols]

[0085] 1...underground piping, 10A, 10B, 10C...straight pipe, 20A, 20B, 20C, 20D, 20E...pipe fitting, 30...large diameter section, r1...outer diameter, 40, 40a, 40b...small diameter section, r2...outer diameter, 50, 50a, 50b...deformation guide section, 52...first connection section, 54...second connection section, 56...intermediate section, 60, 70...deformation guide section.

Claims

1. a cylindrical large diameter portion extending in the axial direction; a cylindrical small diameter portion having a diameter smaller than that of the large diameter portion and extending in the axial direction; a deformation guide portion that connects the large diameter portion and the small diameter portion and is more easily deformed than other portions, Pipe joints for underground installation.

2. A straight pipe to be laid underground is connected to the small diameter portion, The diameter of the small diameter portion is approximately the same as the diameter of the straight pipe.

2. The underground pipe joint according to claim 1.

3. the deformation guide portion has a first connection portion connected to the large diameter portion, a second connection portion connected to the small diameter portion, and an intermediate portion connecting the first connection portion and the second connection portion, In a longitudinal section including the central axis of the large diameter portion, the first connecting portion smoothly connects the large diameter portion and the intermediate portion in a curved line, the second connecting portion smoothly connects the intermediate portion and the small diameter portion in a curved line.

3. An underground pipe joint according to claim 1 or 2.

4. In the longitudinal section, The first connection portion is curved so as to protrude outward, The second connection portion is curved so as to protrude inward, the first connecting portion and the second connecting portion are located between an outer circumferential surface of the large diameter portion and an inner circumferential surface of the small diameter portion; 4. The underground pipe joint according to claim 3.

5. Each of the radius of curvature of the first connection portion and the radius of curvature of the second connection portion is 0.15 times or more the difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion.

4. The underground pipe joint according to claim 3.

6. The difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion is 150 mm or more.

3. An underground pipe joint according to claim 1 or 2.

7. The difference between the outer diameter of the large diameter portion and the outer diameter of the small diameter portion is 350 mm or less.

7. The underground pipe joint according to claim 6.

8. A pair of the deformation guide portions is provided, one of the pair of deformation guide portions is connected to one end of the large diameter portion in the axial direction, The other of the pair of deformation guide portions is connected to the other end of the large diameter portion in the axial direction.

3. An underground pipe joint according to claim 1 or 2.

9. The deformation guide portion is formed of a material that is more easily deformed than other portions.

3. An underground pipe joint according to claim 1 or 2.

10. A method for laying underground piping, comprising: An arrangement step of arranging a plurality of pipe joints according to an underground shape, Each of the plurality of pipe fittings comprises: a cylindrical large diameter portion extending in the axial direction; a cylindrical small diameter portion having a diameter smaller than that of the large diameter portion and extending in the axial direction; a deformation guide portion that connects the large diameter portion and the small diameter portion and is more easily deformed than other portions, Each of the plurality of pipe joints has a pair of the deformation guide portions, one of the pair of deformation guide portions is connected to one end of the large diameter portion in the axial direction, The other of the pair of deformation guide portions is connected to the other end of the large diameter portion in the axial direction. How to lay underground pipes.

11. The method further includes a setting step of determining a length of a pipe between adjacent pipe joints among the plurality of pipe joints in accordance with the underground shape, In the arranging step, the plurality of pipe fittings are arranged in accordance with the determination result in the setting step. The method for laying underground pipes according to claim 10.

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