JPS59136016A - Low heat resistance buried material for underground cable - 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 The present invention relates to a material for backfilling underground power transmission lines, which is used for backfilling around underground cable conduits, backfilling tunnels, or filling inside tunnels.

Conventionally, sand has been mainly used for backfilling around underground cable conduits and backfilling around cables and pipes installed in tunnels. The basting sand dries due to the heat generated by the cable, and its thermal resistance increases four to five times that when it is wet, creating a heat insulating effect. For this reason,
There is a danger that the temperature of the cable will rise rapidly, causing so-called thermal runaway. In addition, when sand is blown into the cavity between the sheath pipe in the tunnel and filled, it is done from the above-ground hole, but in this case, the fluidity of sand is low, so the distance that can be pumped is 2.
Because it is short at about 9 m and the amount of pumping is small, the workability is extremely poor. Therefore, in recent years, as a method of improving this pumping characteristic, aerated milk containing cement alone containing 50 to 70% by volume of air has been used. However, since this aerated milk contains 50 to 70% by volume of air, it has a large thermal resistance and cannot efficiently dissipate the heat generated by the cable. As a result, the power transmission capacity of the cable will be reduced and the temperature will rise excessively.

The purpose of the present invention is to eliminate the drawbacks of these conventional backfilling materials, to provide a backfilling material for underground power transmission lines that maintains low thermal resistance even when dry, can be pumped over long distances, and has excellent workability. It's about doing.

Next, the present invention will be explained in detail.

The gist of the present invention is cement and sand? By mixing air bubbles created by a foaming material into the mixed mortar to create a foam mortar, it improves fluidity and enables long-distance pumping using conventional pumps, greatly improving workability. =, the purpose is to increase the density by further adding an admixture to realize low thermal resistance.

The admixture used in the present invention is a fine particle that can fill the voids between sand or cement particles, and when combined with sand and cement, creates a dense mortar, which is the core of the backfilling material that achieves low thermal resistance. Examples of admixtures that can be used include fly ash, sludge, bentonite, china clay, young pine, and stone powder, but there are no particular restrictions as long as they are made from fine powder.

Bubbles are also created using a foaming agent. The foaming agent is mainly a protein hydrolyzate, such as Marl P liquid (manufactured by Marl Chemical Co., USA), but various protein-based and surfactant-based products can also be used. can.

In order to create bubbles using these foaming agents, a pre-foaming method is preferable, and it is desirable to regulate the bubble diameter to 0.2 to 0.5 mm. By mixing a small amount of air bubbles into the dense mortar made of cement, admixtures, and sand, this group of air bubbles gives appropriate fluidity and viscosity to the mortar without increasing thermal resistance, allowing the separation of each material. In addition to eliminating pleading (volume reduction), each bubble and inanimate object acts like a ball bearing when pumping, which makes it 100% lower than sand or sand mortar.
This makes it possible to pump long distances more than 0 times longer.

In addition, this invention: Cement that can be used can be used alone or in combination, but examples of cement that can be used include Portland, blast furnace, kerosene, flyanyu cement, mixed cement, special cement, cement solidifying agent, and others. cement. These cements are appropriately selected depending on the situation, taking into consideration hardening time, strength development, etc.

Sand that can be used in the present invention is fine aggregate for concrete and mortar, natural sand such as river sand and mountain sand, screening, young pine, stone powder, etc., and these include cement,
Together with the admixture, it forms the backbone of the backfill material. Furthermore, the water that can be used in the present invention is clean water that does not contain oil, acids, salts, or organic substances. Next, examples of the present invention will be described.

Examples As shown in Table 1 as examples, per 10 of the cellular mortar, which is the backfilling material of the present invention, 25 ml of Pogeltland cement and 10° of sand with a coarse grain ratio of 182 were added.
Kri, water 3.0Kp and fly ash 25 as an admixture.
Add Ky and knead to make mortar. Using a 25-fold dilution of the foaming agent Marl P solution, the bubbles created by the foaming machine were 1.21! It got mixed in. Then, the unit volume weight and air content flow value of this backfilling material were measured. Thereafter, the strength and specific heat resistance values were measured at 28 days of age.

Example As shown in Table 1 as the implementation side port, a mortar is prepared by using the same amount of fly ash as an admixture in the Example beating as granulated blast furnace sludge, and then air bubbles are added to the mortar using a 25 times diluted Marl P solution. 1.21 was mixed in, and the air content, specific thermal resistance value at 28 days of age, etc. were measured.

As is clear from comparing the results of these examples and the attached conventional filling materials A and B in Table 1, the air content of the conventional product is 50 to 60 by mixing the admixture.
%, it is reduced to 10 to 20%, and it can be seen that both unit volume weight and compressive strength are better than the conventional product. Furthermore, the specific thermal resistance of the conventional product is 219 to 263℃.
/ cx w, in the case of the present invention, it is reduced to 70~b~%, which shows that the power transmission capacity can be increased by 20~30% by using the backfilling material of the present invention. It is also expected to increase power transmission capacity by approximately 10% compared to the conventionally used refill sand. Furthermore, since the thermal resistance of the backfilling material of the present invention when dry is only about 15 times that when wet, drying may occur due to heat generation from the cable. Mi0
It can be seen that it is much smaller than in the case.

Next, an example of a method for filling a tunnel using the backfilling material of the present invention will be explained with reference to the drawings. A mixer (2) and a pressure pump (3) (
For example, a ground plant (4) equipped with a screw type), a foaming machine (not shown), etc. is installed. Also, pressure pump (
A pressure feed hose (5) is connected to 3), and the tip of the pressure feed pipe (6) (for example, made of hard vinyl chloride pipe) is connected to the weir forming the filling section (8) in the tunnel (7). It is set through the insertion hole of the stop plate (9) so that it is located at the innermost part of the filling section (8).

Immediately before pumping, a predetermined amount of air bubbles is mixed into the mortar of the present invention kneaded by the mixer (2), and then the mortar is pumped by the pressure pump (3). Also at this time, the pressure feed pipe (
6) from the back of the filling section (8).
) side, filling with the backfilling material 0ω of the present invention is carried out from the deep part of the filling section (8) to the damming plate (
9). As a result, the air vent pipe αυ (for example, made of a hard vinyl chloride pipe with a length of 1 m) provided on the upper part of the dam plate (9) allows the filling to be performed without creating an unfilled space while expelling the air within the filling section. When the backfilling material α0 leaks from the air vent pipe aυ, filling is completed by stopping pressure feeding.

As is clear from the above explanation, the present invention has lower thermal resistance than conventional backfilling materials even when the cable dries due to heat generation, and can be pumped over long distances, improving workability. This provides a reburial site for underground cables with excellent advantages, and its practical effects are great.

[Brief explanation of the drawing]

The figure is a sectional view showing an example of a method for filling a tunnel with the backfilling material of the present invention. (1)...Starting shaft, (2)...Mixer,
(3)...Pressure pump, (4)...Ground plant, (5)...Pressure hose, (6)...Pressure pipe, (7)...Tonnenobe ( 8)... Filling section, (9)... Dam plate, α0... Backfilling material of the present invention, U... Air vent pipe. Patent applicant Written amendment by one person outside the Central Research Institute of Electric Power Industry (voluntary) February 24, 1981 Director of the Patent Office Kazuo Wakasugi 1 Indication of the case Patent application No. 1986-8694 2 Title of the invention Low heat resistance backfilling material for cables 3 Relationship with the case of the person making the amendment Applicant Foundation 1 person outside the Central Research Institute of Electric Power Industry 4, Agent 1-23-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 5. Details subject to amendment 1 Column 6 of ``Detailed Description of the Invention'', Self-Answer for Amendment (1) Correct [backfill] in line 10 of page 1 of the specification to [backfill]. (2) Correct the 10th line of the first page to ``C'', etc.). (3) Page 2] 1) [cause] the line [cause]
Correct. (4) Page 2, line 20 (last line) [foaming agent]
Correct. (5) Correct page 3, line 7, “satisfies” to “satisfies”. (6) Correct page 3, line 12 [fine powder] to [fine particles]0 (7) Change page 3, line 13 [if it is a material] to [if it is an inorganic material] correct. (8) On page 7, line 15, correct ``happen'' to ``happen''. (9) Correct page 7, line 17 [middle filling] to [middle filling].

Claims (1)

[Claims] Fine powder is added to the mortar mixed with cement and sand.