JP2010230107A - Buckling mode steel pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipeline crossing a fault with a steel pipe having large ability for withstanding fault displacement, considerably reducing risk of breakage and water leakage as compared with a conventional steel pipe even when the fault displacement occurs, being low in cost and giving high deformation performance. <P>SOLUTION: As a structure for absorbing the fault displacement with a buckling mode steel pipe having a buckling mode portion, the pipe (buckling mode pipe) is formed with a buckling mode shape. The pipe is arranged in a buried pipeline or the like in a predetermined number, so that when displacement is caused in the pipeline or the like by earthquake or the like, the displacement is concentrated in crest portions of the buckling mode and absorbed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a steel pipe used for various uses such as water supply, gas, and electric power, and particularly relates to a steel pipe capable of absorbing fault displacement.

  Conventionally, as a structure that absorbs the displacement of a steel pipe that is used for supplying water, gas, electric power, etc. and buried in the ground, a bellows-type telescopic flexible tube that absorbs the displacement as a bellows type (Patent Documents 1 and 2) In addition, there is a sliding-type telescopic flexible tube that absorbs displacement by sliding as a mechanical structure using rubber.

Japanese Patent Laid-Open No. 11-304057 JP-A-11-311378

  In the displacement absorption using the bellows type expansion / contraction flexible tube, the bellows part has a bellows shape and is very thin compared to the straight pipe. However, the tube thickness is insufficient for constant loads such as earth pressure.

  In displacement absorption using a sliding telescopic flexible tube, when a large deformation such as fault displacement occurs, the sliding part is a chain structure that is only connected by bolts, so that bending is concentrated in one place. There is a danger of water leakage beyond the limit bending angle.

  In order to absorb ground displacement of buried pipes, it is common to use bellows type expansion and contraction flexible pipes and sliding type expansion and contraction flexible pipes. It is impossible to add the rigidity (equivalent to a straight pipe) to a bellows type expansion / contraction flexible pipe or a sliding type expansion / contraction flexible pipe, and it is also difficult to follow deformation. Therefore, it is desired to develop a structure that has the same rigidity as a straight pipe and can absorb fault displacement.

  Further, the method of continuously disposing a bellows-type expansion / contraction flexible tube or a sliding-type expansion / contraction flexible tube with respect to a fault displacement of several meters can be applied when the fault plane is clear and pinpoint. However, it is unclear where the fault plane appears in pipes that are buried with a relatively shallow cover, and it is very uneconomical because it must be laid continuously over several hundred meters.

  An object of the present invention is to provide a steel pipe that can be used for a pipe crossing a fault and has high-performance deformation performance at low cost.

  The present invention provides a steel pipe that solves the above-mentioned problems, taking advantage of the deformation performance and buckling performance of commonly used mild steel, and even when large deformation such as faults occur in the pipe. The present invention relates to a pipe having a shape capable of absorbing displacement by the steel pipe itself.

The present invention is a tube (buckled corrugated tube) in which a buckling corrugated shape is formed as a structure that absorbs fault displacement, and by arranging a predetermined number of these in an embedded conduit or the like, the conduit or the like due to an earthquake or the like When the displacement occurs, the displacement is concentrated and absorbed in the peak portion of the buckling waveform, and the following effects are exhibited.
a At the time of ground deformation, only the buckled corrugated pipe will stretch (compress) and absorb the deformation.
b The deformation of the pipe body is greater than the thickness of the buckling waveform compared to the straight pipe, so even if the buckling waveform part is fully extended, the deformation does not concentrate and moves to the next buckling waveform pipe. Moreover, since it is more than the same pipe thickness as a straight pipe, even if it extends fully, it has sufficient pipe thickness with respect to earth pressure.

  The buckled corrugated steel pipe of the present invention has a large force to withstand a fault displacement, and even if a fault displacement occurs, the risk of breakage and water leakage can be greatly reduced compared to conventional steel pipes. Moreover, the cost is low.

It is a figure explaining the buckling waveform of the steel pipe of this invention. It is sectional drawing which shows the state which embed | buried the buckling corrugated steel pipe of this invention in the ground. It is a side view which shows the state which this steel pipe deform | transformed.

The steel pipe to which the present invention is applied needs to be able to be deformed without breaking the buckling waveform portion according to the fault displacement, and mild steel (SS400) is preferable in this respect. Here, the mild steel has a carbon content of 0.13 to 0.20% and a tensile strength of 330 to 430 N / mm ² . The pipe diameter and plate thickness of the steel pipe are determined depending on the application and the like, but the pipe diameter is about 600 A to 3000 mm in diameter (nominal diameter).

  The buckling corrugated portion provided in this steel pipe absorbs compression due to fault deformation, and it is easy to absorb deformation by giving an initial deformation similar to the waveform generated by the straight pipe causing compression local buckling. is doing.

  The buckling waveform takes into account fault displacement and ground conditions from the compression local buckling wavelength (L = 1.72√ (r · t), r: pipe radius, t: pipe thickness) and peak height (n times the plate thickness). FEM analysis is performed to determine the optimum shape.

  The buckled corrugated steel pipe of the present invention can be manufactured, for example, by manufacturing a buckled corrugated mold in advance and applying a water pressure to the steel pipe from the inside according to the mold.

  Table 1 shows an example in which FEM analysis was performed on steel pipes having different outer diameters and pipe thicknesses, and the shape of the buckling waveform portion was obtained.

これらの座屈波形鋼管は、管路中に配設された後、地中に埋設され、断面変位が起こると図３に示すように変形して管路の破壊を免れる。

These buckled corrugated steel pipes are disposed in the pipe and then buried in the ground. When a cross-sectional displacement occurs, the buckled corrugated steel pipe is deformed as shown in FIG. 3 to avoid breaking the pipe.

  The steel pipe of the present invention can be widely used as a pipe for a fault portion because it resists fault deformation and is not easily destroyed.

a Buckling wavelength
b Mountain height
c Straight pipe
d Fault plane
e Buckling waveform

Claims (1)

  Buckling corrugated steel pipe with buckling corrugation

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