DE1804310A1 - Process for breaking reinforced concrete, rock or the like. - Google Patents

Description

5918-6ö / Kö / hs

Japan answer no. 42-67505

Registration date: October 21, 1967

1. Fuji Motors Corporation,

No.142-1, Imokubo, Yamato-maehi, Kitatama-gun, Tokyo (Japan)

2. Masatada Kawamura,

No. 8-3, 3-chome, Higash! -Mach !, Hoya-City, Tokyo (Japan)

3. Yoshio Kasai,

No. 80-2, Takidai-eho

Funabashi-City, Chiba-Prefecture (Japan)

Method for breaking up reinforced concrete, rock or the like .

The invention relates to a method for breaking up reinforced concrete, stone or the like by electrical means.

In order to break open and destroy reinforced concrete structures, the usual methods of the Blasting with explosives and / or with compressed air and / or splitting with iron wedges, smashing with iron hammers and the like. With unreinforced concrete, stone structures or natural stone and the like. Similar methods were used. It is also known in this latter context, by high frequency induction heating or the like. To locally generate a strong heat in the body to be exploded and thereby the Breaking open body.

It has already been compared to the conventional Much faster, safer, and cheaper breaking methods have been proposed (Japanese Patent Application No. 13999/1965), in which a from the outset or retrospectively in the body to be broken up made of reinforced concrete, rock or the like. Built-in electrical conductor charged with electrical current is such that the body is ruptured by thermal expansion due to the heat generated by the current.

If, according to this method, for example, an iron rod with a diameter of 9 mm is inserted into a reinforced concrete body with a rectangular profile of 15 χ 20 cm cross-sectional area and 100 cm Built in length about 3 cm from the surface

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is connected to an electrical power source via lead wires and feeds it with a current of 10 V, the reinforced concrete body is broken by splitting.

The temperature of the built-in iron rod increases due to its electrical resistance in a few minutes at 800 to 1000 ⁰ C, so that the rod undergoes a Wärmeaußdehnung in radial and longitudinal direction. Since the thermal expansion of iron is about 0.000013 / 1 ⁰ G, the length of the iron rod 100 increases in the example mentioned cm to approximately 101.3 cm and its diameter of 9 mm to approximately 9 * 12 mm. On the other hand, since the thermal conductivity of concrete is 1.2 - 1.3 kcal / mh ° C when air-dried, which corresponds to approximately 1/30 - 1/40 of the thermal conductivity of iron, the temperature rise in the concrete is on even with a very rapid rise in temperature in the iron the area around and in the immediate vicinity of the iron bar is limited, so that it only has an effect in this area of the concrete and consequently essentially only the built-in iron bar, but not the concrete itself, experiences thermal expansion. Furthermore, since physical and chemical changes in the concrete material occur in the contact area between concrete and iron due to the high temperature, the adhesiveness of the concrete is noticeably reduced or completely eliminated. Then the tensile strength of the concrete is approximately 1/10 - 1/20 of its compressive strength.

Because of these facts and processes, the thermal expansion The consequence of the iron rod is that the concrete is split and largely or completely loses its adhesion to the iron rod.

Because a reinforced concrete body or component through the adhesion between the reinforcing iron rod and the one surrounding it Concrete mass is held together, it is very difficult to the body or the component through the application of mechanical energy such as blow or the like, while on the other hand, if the adhesion between the reinforcement and the concrete is reduced or eliminated and a gap is formed in parts of the concrete breakage is easily possible with the aid of mechanical energy.

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The present invention makes use of this principle. Since in the above-mentioned proposed method with Alternating currents with a technical frequency of 50 to 60 Hz will be used for heating the iron bar or steel reinforcement (hereinafter referred to as "iron and steel ladder") with increasing cross-sectional area of the Elsen rod or the Reinforcement requires correspondingly stronger currents, namely of considerable absolute values. The following result Problems:

1. The power line wires become very thick and therefore difficult to handle.

2. The contact resistance between the lead wire and the iron and steel conductor must be reduced, but it does so difficult and often impossible in practice.

j5. The electromagnetic force in the supply wire increases.

As a result of experiments conducted to solve these problems, the present invention has found that the temperature in the iron and steel conductor that can be achieved with a given amount of current by increasing the frequency of the current can be increased very quickly or strongly. The electric current flows at the appropriate frequencies due to the so-called skin effect (skin effect) close to the surface of the iron and steel conductor, which is a corresponding increase the electrical loss resistance of the conductor and an increase in the ohmic loss (Joule loss) result has, from which it follows that in this case a given temperature rise can be achieved with far less electricity than when using a current with a technical frequency. the Invention is based on these findings and makes use of them accordingly.

One of the main features of the invention is that a before or after in a body made of e.g. reinforced concrete Rock etc. built-in conductor charged with electric current j is to the body by thermal expansion and reduction or Eliminate the adhesion or break it into a breakable one

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To bring state. Thereby it is achieved that the body is broken very easily by the application of mechanical energy which can even be done naturally, i.e. without the use of mechanical energy.

Another feature of the invention is that with a current of higher than the technical frequency of 50 to 6O Hz is worked, so that taking advantage of the above Skin effect of the electric current, greater heating is achieved with less power consumption. This achieves that the difficulties mentioned with regard to the design of the electrical connections do not apply and that the method itself designed more economically.

The invention is described below with reference to the drawings in

individually explained. Show it;

Fig. 1 is a diagram showing the relationship between the frequency and represents the current penetration depth for an iron and steel conductor with a round profile;

2 shows the schematic representation of an exemplary embodiment of the for the experimental testing of the invention Method used arrangement;

3-5 diagrams which show the process according to the invention reproduce achieved results according to an embodiment;

Pig. 6 and 7 are diagrams showing the results obtained in other tests in connection with the method;

Fig. 8 is a graph showing the relationship between temperature change in certain areas of the concrete and the duration of heating when heating a built-in concrete Iron rod with electric current;

9 shows the temperature distribution for the in the diagram according to FIG. Fig. 8 is a diagram showing the assumed case;

Flg. Fig. 10 is a graph showing the temperature distribution in the case where the iron rod is heated faster than in the case presupposed in FIG. 9; and

11 is a diagram showing the mechanical stress distribution

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for the case assumed in FIGS. 9 and 10.

The diagram according to FIG. 1 shows the current penetration depth cf as a function of the frequency f when current flows in an iron and steel conductor with a round profile for various values of the permeability yes . The functional relationship corresponds to the following equation:

κ = 5.92 χ 10

From this it follows that with increasing frequency the current cross-section decreases and consequently the effective one Resistance increases. It will therefore rise for a given temperature the higher the frequency, the smaller the current required, so that it is to be expected that in this way, i. by increasing the frequency, the difficulties and deficiencies that occur in the other case, i.e. when the current is increased can be fixed.

Fig. 2 shows an embodiment of a device which was used in the experimental testing of the method according to the invention. The device contains a direct current motor 1, an induction frequency converter 2, a single-core transformer 3, a heating transformer 4 and an iron rod 5 for the heating experiment. The frequency is converted in the frequency converter 2 and fed into the transformer 3 to control the secondary voltage of the heating transformer 4. The iron and steel conductor 5 was heated in air in a wind-free chamber. The heating temperature was measured by contacting copper with constants. To determine the current flow in the conductor 5, the induction voltage of a probe coil was measured with a tube voltmeter. In order to exclude the change in permeability that occurs at high temperatures, a relatively small current of a fixed value of 120 A was used when carrying out the experiment. To determine the current dependency of the temperature rise for iron and steel conductors of various sizes and types, the frequency was used as

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Parameters used. The results are in the graphs below Fig. 3 to 5 reproduced. Each are on the ordinate the temperature of the iron and steel conductor (in C) and the duration of the current flow (in minutes) on the abscissa. Pig. 3 shows the relationships found for a round steel bar with a nominal diameter of 9 mm and FIG. 4 those for one Round steel bar with a nominal diameter of 19 mm. From the diagrams it turns out that 2 minutes after the onset of the current flow the temperature at 200 Hz in the case of the 9 mm rod is approximately 3.3 times and in the case of the 19 mm rod 5 times as high as at 60 Hz. Fig. 5 shows the relationships for equilateral angle iron with nominal dimensions of 40 χ 40 χ 5 · This results in almost the same conditions as with the round profiles.

Fig. 6 shows the relationship between the current and the alternating current resistance (impedance), the results being obtained by measuring at a frequency of 50 Hz by immersing various iron rods (9 ram, 1.5 mm and 16 mm in diameter) in water to control the temperature rise were obtained. As you can see, the resistance increases with the current. It is believed that this is due to the fact that the increase in the magnetic field due to the increase in current causes a decrease in permeability and affects the skin effect. The dashed straight line labeled "16 Rdc" shows, for comparison purposes, the direct current resistance of the iron rod with a diameter of 16 mm. Compared to this, even at a frequency of 50 Hz, the stated alternating current resistance at 300 A is approximately 4.2 times and at 700 A approximately 3.3 times as great. In addition, the power factor in this case was approximately 0.95.

Fig. 7 shows the results of an experiment under Using a relatively small current at the frequency of 200 Hz was carried out. From the diagram it can be seen that when the frequency is increased, the skin effect becomes even stronger.

Then the iron loss has to be considered as a factor increasing the effective resistance. Given Frequency, the hysteresis losses increase proportionally to the magnetic flux density with the 1. 6th to 2nd power, so that

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■■ »'lisp ίί» τ' ·

this for the explanation of the relationship between current and impedance according to ELg. 6 is not suitable. The impedance characteristic shows in this case suggests that the decrease in permeability due to the increase in current affects the skin effect.

From the test results it follows that in the case of direct current heating of an iron and steel conductor with a large Cross-sectional area a small flow for achieving the desired temperature rise is sufficient if one is taking advantage of it of the skin effect increases the frequency, so that the suitability of the method according to the invention for the solution of the Task is proven.

The diagram according to FIG. 8 shows the dependence of the temperature change in a certain area of the concrete on the heating time for the 5 minute long heating of an Elsen rod built into the concrete with a diameter of 16 mm by means of an electric current of constant power. The temperature was measured with the copper constantan instrument previously built into the concrete. The temperature in the concrete exceeds in this case, not the value of 10O ⁰ C. This can be explained by the fact that the always included in any concrete quality moisture evaporation absorbs heat from the concrete.

The diagram according to FIG. 9 shows the temperature distribution in the concrete at different times, namely 1 minute, 2 minutes and 5 minutes after switching on the electrical current. Of the The high temperature range (over 100 ° C) is represented by an approximation formula.

FIG. 10 shows the temperature distribution in the case where the iron rod is heated faster than in the case of FIG. 9.

The diagram according to FIG. 11 shows the distribution of the mechanical stress in the circumferential direction of a concrete cylinder with a diameter of 20 cm for the case assumed in FIGS. 9 and 10. The mechanical stress was determined from the chip caused by the thermal expansion of the iron bar, taking into account the change in the concrete caused by the thermal expansion, and from the thermal expansion stress of the concrete itself. Curve A gives the voltage distribution 2 minutes after switching on the electrical current, curve B the voltage distribution

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5 minutes after switching on the current, both again for the case according to FIG. 9 , while curve C shows the voltage distribution 2 minutes after switching on the current for the case according to FIG. With a tensile strength of the concrete of 50 kg / cm, the tensile strength or breaking stress is on one. Point 4.7 mm from the center of curve A, while the stress at break reaches the cylinder surface in curve C after the same heating time as in curve A.

It can be seen that in the case of curve B, it takes over 5 minutes to achieve the same effect as in the case of curve C, and it can also be seen that the case of FIG Occurrence of fractures required time is more favorable than the case according to Fig. 9 ·

From the above explanation it can be seen that through the use of an increased frequency of the heating current, as provided in accordance with the invention, utilizing the skin effect the current required to achieve a desired increase in current is reduced. Preferably you work with Frequencies between 100 and 500 Hz. If you increase what with the currently available electrical equipment without further ado is possible, the frequency of the heating current to about 10,000 Hz, the process is even more effective.

Since the heating effect is limited to the area close to the surface due to the skin effect, one can use for the iron and steel rod to be subsequently installed for breaking open a rod with a rod instead of one with a full profile Use a hollow profile or a tubular body for the method according to the invention.

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Claims (4)

Claims 1. A method for breaking reinforced concrete, rock or the like., Characterized in that a An iron and steel conductor built into the body to be broken open an alternating electrical current with a technical frequency from 50 to 60 Hz is supplied so that the conductor is heated and thermally expanded, the adhesion between the conductor and the body is reduced, and the body is ruptured or made frangible will. 2. A method for breaking up reinforced concrete, rock or the like., Characterized in that one in the body to be broken open iron and steel conductor an alternating electrical current with a frequency in the range between a value exceeding the technical frequency and 10,000 Hz, which results in an electrical skin effect is, such that the conductor is heated and thermally expanded, the adhesion between the conductor and the body is reduced and the Body is broken open or made breakable. j5 J5 method for breaking up concrete, stone or the like, characterized in that a hole is made in the body to be broken open that into the hole an iron and steel conductor with a solid profile or hollow profile is inserted, and that the inserted conductor is an electrical one Alternating current is supplied with a frequency in the range between the technical frequency and 10,000 Hz, such that the Conductors are heated and thermally stretched and the body is broken open or made breakable. 4. The method according to claim ~ $, characterized in that the iron and steel conductor in the hole with concrete or the like. Is fixed. 90983 2/0844