JPS62215736A - Method for preventing freezing of embedded pipeing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the vertical direction due to freezing heave, thawing and subsidence of the soil that the rising portion of buried gas and water pipes (hereinafter referred to as riser) in cold regions is subjected to. This invention relates to a method for preventing frost damage based on shear force.

[Conventional technology]

Buried piping in cold regions is horizontal piping 1 as shown in Figure 5.
is placed below the maximum freezing depth H to prevent frost heaving and subsidence.

In this case, when the soil 3 freezes in winter, it freezes up by h, and at this time, the freezing heave blade acts on the riser pipe 2, creating a drag force on the joints 4 and 5.

This force varies depending on soil quality, temperature, freezing depth, etc.
Many cases have been reported in which the joint portion 4.5 is damaged.

Conventional countermeasures to prevent this include [1]
A method of backfilling with sand slurry, etc. that has low frost heaving properties (2) A method of using the L-back method to suppress the bending moment at the top and bottom of the riser pipe (3) A method of using a mixture of oil and wax between the pipe and the soil There are methods such as filling the pipe and cutting the adhesion between the pipe and frozen soil.

[Problem that the invention seeks to solve]

However, the conventional countermeasure methods (1) to (3) have the following problems in preventing frost damage.

First of all, (11) is a method that prevents the ground near the piping from frost heaving by not backfilling with sand slurry, etc., which has a small frost heaving property, around the piping standpipe 2 or upright W2 and horizontal piping 1. However, not only is a sand slurry and the like specially required, but the absolute effect of reducing frost heave is not very great.

Furthermore, in the long term, since the contamination of surrounding soil is unavoidable, the reduction effect is not permanent, and backfilling with earth and sand must be performed frequently.

The following (21) absorbs the stress and displacement caused by frost heave by providing mechanical joints at the upper and lower parts of the riser pipe 2 during piping construction, and by providing joints with joint functions in the horizontal piping 1. However, due to its structure, it can only be applied when the amount of frost heave is relatively small, and it is not only difficult to use in areas where the amount of frost heave is large, but also extremely difficult to apply to existing piping in terms of workability and economic efficiency. Have difficulty.

The last step (3) is to fill the area around the riser g2 with an antifreeze mixture such as oil and wax, or backfill it, and in some cases use a double pipe system to prevent adhesion between the riser pipe 2 and the frozen soil. It is something to cut.

This method requires construction on-site even for new piping, and since the above-mentioned antifreeze mixture has a certain degree of fluidity in terms of ease of construction, it may cause damage to the surrounding soil. There are drawbacks such as increased penetration or dispersion, which necessitates refilling.

In addition to these construction methods, heat-retaining tube wrapping methods have been considered, but they have the disadvantages of being difficult to construct and requiring additional maintenance, resulting in a loss of thermal balance with the surrounding soil and environmental concerns. may have no adverse effect.

As mentioned above, conventional countermeasures are: ■ Difficult to apply to existing pipes, ■ Requires maintenance, ■ Not durable, and ■ Not suitable for areas with large amounts of frost heaving. It has one or more of the following drawbacks:

Measures to solve problem C] Under the circumstances described above, as a result of various studies on how to prevent freezing damage to underground piping, we decided to install a Over the years, we have achieved a method for preventing frost damage to buried piping by attaching and integrating heat-shrinkable plastic to reduce frost heaving force and negative friction.

[For production]

The description will be given below based on the drawings.

FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention, in which a standpipe 2 rising from a horizontal pipe 1 has an outer surface 6 extending over a length of 8 or more at the maximum freezing depth of the soil. A heat-shrinkable member 7 made of fluororesin is tightly coated with an adhesive 8 to reduce the shearing force generated between the soil and the pipe body.It is constructed as follows.

+11 When applying to existing pipes First, dig the soil around the standpipe 2 to a depth of 8 or more, the maximum freezing depth, expose the pipe, and remove surface earth and sand.

'Next, if a tube is used, remove the joint 4 or 5 of the riser pipe, and insert the tube having a length of 8 or more at the maximum freezing depth into the standpipe 2 which has a length of 8 or more at the maximum freezing depth. It is fitted onto a portion corresponding to the outer surface 6, or if a sheet is used, it is wrapped around a portion corresponding to the outer surface 6.

At this time, the surface of the riser pipe 2 or the fluorine V! Apply an adhesive to the inner surface of the heat-shrinkable member 7 made of 4Ill, and then heat the covering member 7 from the outside or from the outside and the inside of the tube to shrink the covering member 7 and bring it into close contact with the tube. and backfill with earth and sand.

(2) When applied to newly installed piping, a heat-shrinkable member 7 made of fluororesin is provided at a predetermined part by fitting a tube from one end of the pipe body of the riser pipe 2 or by wrapping a sheet around it, and After shrinking this and bringing it into close contact with the pipe body of the riser pipe 2, normal piping construction is carried out.

At that time, is the covering material in close contact? 22 can be made either on-site or in a factory and then cut to an appropriate length on-site.

The covering materials used for the above construction include polyvinylidene fluoride, polyethylene trifluoride,
For fluorine fM fats such as polytetrafluoroethylene, polyhexafluoropropylene, polyfluorinated alkoxyethylene, polyfluorinated ethylene propylene ether, tetrafluoroethylene-67fluoropylene copolymers, or compositions containing these as main components. Use tube-shaped, sheet-shaped, or molded products with heat-shrinkable properties.

These resins have low surface energy, very low wettability of water or soil on the surface, and have a large friction reduction effect, so they are suitable for the purpose of the present invention, and the use of sheet-shaped molded products is This is because it has superior surface smoothness and long-term durability compared to paint coatings.

In addition, the heat-shrinkable function is provided when the outer diameter of the riser pipe 2 is slightly different or when the riser pipe 2 is stray).
・This is because it can be easily followed when not in use, and it can be easily brought into close contact with the pipe body.

Further, as the pipe body of the riser pipe 2, a plated pipe with bare pipe fittings, a painted pipe, or a plastic coated pipe can be used.

Fluorine-based resins do not adhere to other parts, so adhesives mainly composed of silicone resin, epoxy resin, polyester, polyurethane, or acrylic resin are used between the pipe body and the covering member. It is preferable to intervene.

A gas burner, an infrared tubular furnace, an oven, a band heater, etc. can be used as a means for heating the heat-shrinkable member 7 after it is fitted or wrapped.

Integration with the riser pipe 2 is achieved by applying the adhesive 8 and heating shrinking the heat shrinkable member 7, but at this time, the WLPJ force generated between the soil and the covering member due to freezing heave or thawing and subsidence of the soil Large shear adhesion, specifically 2
Adhesive strength of ~3 kg/ci or more is required.

If this condition is not satisfied and the adhesive force is smaller than the frictional force between the soil and the heat-shrinkable member 7, the covering member will fluctuate as the soil changes, resulting in repeated freezing and thawing for a long period of time. Over time, the tube will shift upwards and the frost heave cutting effect will decrease, making it difficult to use it stably for a long period of time.

〔Example〕

EXAMPLES Hereinafter, the structure and effects of the present invention will be explained in more detail by specifically showing examples.

Example 1 A 1 m long WI pipe of 25A (outer diameter 34 cm) was prepared as the pipe body of the riser pipe 2, and after removing rust from the outer surface with a grinder, it was wiped with thinner to give an inner diameter of 43III 111 and a thickness of 0°50+n.
A 400++ m length of heat-shrinkable tubing made of 400 m tetrafluoroethylene-67 fluorinated propylene copolymer was fitted.

After that, the tube was heated from the outside with a propane gas burner to shrink it, and after about 5 minutes, the tube and the tube body were integrated, forming a smooth coating with no wrinkles or scratches of M'A50, G 3ma. did it.

Example 2 A tube body was prepared in the same manner as in Example 1, and after wiping it with thinner,
An adhesive made of silicone resin was applied to a length of about 20 μm over a length of 400 μm on the tube surface using a spatula.

Next, the same tube as in Example 1 was fitted so as to match the adhesive applied area, and the tube was shrunk while being heated with a propane gas burner.

After about 5 minutes, the tube and body become tightly integrated and the membrane J! X0
．． A smooth coating of 63+w without wrinkles or blemishes was formed.

Example 3 The coated pipe obtained in Example 1.2 and the uncoated steel pipe were prepared, and the freezing heave was measured using the experimental apparatus shown in FIG.

This device has a reaction frame 11 bridged between frames 10 and 10 erected on a substrate 9, and an earthen tank surrounded by a heat insulating material 12 with a thickness of 100 mm on the substrate 9 and filled with soil 14 inside. 13, a test specimen 15 is built into this ±14, a load cell 16 is interposed between the test specimen 15 and the reaction frame 11, and the displacement of the surface of the soil 14 in the soil tank 13 is measured. A displacement meter 17 is provided.

After installing the frost damage prevention pipe according to the present invention and the conventional steel pipe into the experimental equipment constructed in this way, the entire equipment was installed in a freezing room and cooled starting from room temperature to -40°C. This state was continued for 24 hours.

During this period, changes over time in the frozen upper blade were measured using a load cell 16, and the results are shown in FIG.

Additionally, the frost heave fi (displacement) during this period was approximately 15 for each specimen.
- There was no change.

As is clear from FIG. 4, the weight of the freezing heave blade in Example 1 is around 2,400 kg, while that of the uncoated steel pipe is around 2,400 kg.
The coated steel pipes obtained in step 2 have a weight of 250 to 300k.
g, and it can be confirmed that the freezing force is significantly reduced.

Furthermore, in order to investigate the permanence of the effect of reducing the upper edge of the freezing method, the above freezing phenomenon was repeated on the same test specimen, and the maximum freezing force was determined each time, and the results are shown in FIG.

As is clear from the results, there was no major change in the coated steel pipe obtained in Example 1.2 even after 10 repeated tests, confirming that the effect of reducing the top edge of the freezing method continues. Ta.

The reason why the force of the test specimen based on Example 1 is larger than that of Example 2 is due to water entering between the pipe body and the covering member from the end of the covering. Embodiment 2, which uses an adhesive material that prevents this, is more desirable from the viewpoint of durability of the effect.

〔Effect of the invention〕

According to the present invention, the following remarkable effects can be achieved.

(Since the freezing of the soil to the pipe body can be significantly reduced, the piping start-up part in a cold region can be sufficiently protected from frost damage.

(2) It can be easily applied not only to new piping but also to existing piping, and is maintenance-free because the effect of reducing the upper blade of the freezing method is maintained over a long period of time.

(3) Since the covering member formed on the pipe body does not move, it is suitable for areas with large frost heaving.

(4) It can be used in combination with conventional frost damage prevention methods, such as backfilling with sand slurry that has low frost heaving properties.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the present invention, Fig. 2 is an experimental device, and Fig. 3 is a graph showing changes in freezing force over time.
FIG. 4 is a graph showing changes in the freezing appearance force depending on the number of repetitions, and FIG. 5 is a sectional view showing a conventional buried pipe. 1. Horizontal piping, 2. Standpipe, 3. Soil, 4.
5-Joint, 6-Outer surface, 7-Fluororesin heat shrinkable member, 8-Adhesive, 9-Substrate, 10-Frame, 11-Reaction force frame, 12- insulation material, 13
- Soil tank, 14... Soil, 15... Test specimen, 16 - Load cell, 17... Displacement meter, H... Maximum freezing depth distance, h... Frost heave line.

Claims (2)

[Claims] (1) Underground piping made by attaching and integrating heat-shrinkable plastic over a length corresponding to the freezing depth to the rising part of the underground piping to reduce freezing heave force and negative friction. How to prevent frost damage. (2) The method for preventing frost damage according to claim 1, wherein a fluororesin or a plastic containing this as a main component is used as the heat-shrinkable plastic.