JP3550893B2 - How to check the filling status of cast concrete - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for checking the state of filling of cast concrete, and in particular, the state of filling of cast concrete in a stable liquid applied to an underground continuous wall or a cast-in-place pile for building a reinforced cage in an excavation hole. This is related to the confirmation method.
[0002]
[Prior art]
In recent years, the strength of underground continuous walls has been increased from the viewpoint of increasing the depth of underground structures and improving earthquake resistance. In addition, in high-rise buildings and the like, from the viewpoint of using the main body of the underground continuous wall, in addition to increasing the strength, densification of reinforcing bars and the like are also progressing. The casting of concrete under such conditions is usually performed using a tremy tube. The important thing in concrete casting is that the concrete is uniformly filled in the whole area. To improve the filling condition, use high-fluid concrete with excellent fluidity and material separation resistance. Has also been done.
[0003]
By the way, as a method of confirming the filling condition of the poured concrete, conventionally, it is performed by checking the top of the poured concrete by swinging down, or, for a part that is not visible, after hardening, I was digging up. However, such a conventional method for checking the state of filling of cast concrete has the following problems.
[0004]
[Problems to be solved by the invention]
In other words, in the method of confirming the top position by swinging down, the technician's intuition is to confirm the top position of the poured concrete by touch when the weight descends in the stabilizing liquid and reaches the top of the concrete. And there are individual differences. In addition, it is difficult to check the portion where the arrangement of the reinforcing bars is high in density, and even if there is an unfilled portion of the concrete in the high density portion, it cannot be found.
[0005]
Furthermore, when high-strength or high-fluidity concrete is adopted, the change in tension when the weight reaches the top of the concrete is smaller than that of conventional concrete, so that it is difficult to confirm the top itself. On the other hand, the method of checking by digging raises the problem that the quality of the filling condition cannot be known unless concrete is hardened, so that it is not possible to respond promptly when measures are required.
[0006]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to easily and surely fill concrete even in a high-density portion of a reinforcing bar. The purpose is to provide a method by which the situation can be checked during casting.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for confirming the state of filling of concrete, in which a steel cage is erected in a ground excavation hole excavated while filling with a stabilizing solution, and concrete is poured. A plurality of sensors are pre-arranged in the reinforced cage at predetermined intervals along the depth direction of the excavation hole, and the concrete is lifted due to a difference in electrical properties of a substance interposed between electrodes of the sensors. The position is detected.
According to the confirmation method configured as described above, since the sensor is pre-arranged in the reinforcing bar cage, even in the high-density portion of the reinforcing bar arrangement, due to the difference in the electrical properties of the substance interposed between the electrodes of the sensor, The concrete filling status can be confirmed.
In this case, the electrical property measured by the sensor may be a residual voltage between the electrodes after a low voltage is applied between the electrodes for a short time.
According to this configuration, the stabilizing liquid, the stabilizing liquid in contact with the concrete, and the concrete can be clearly identified from the state of the residual voltage.
Further, in the method for checking the filling state of the cast concrete according to the present invention, the point at which the residual voltage decreases and then stabilizes after rising can be regarded as the top end position of the cast concrete.
If this determination method is adopted, the top end position of the cast concrete can be accurately known.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 to FIG. 5 show one embodiment of a method for checking the filling condition of cast concrete according to the present invention. The embodiment shown in the figure applies the present invention to the construction of an underground continuous wall. In the construction of an underground continuous wall, first, as shown in FIG. An excavation hole 12 is formed in the ground while being filled with the liquid 10.
[0009]
In the example shown in FIG. 1 (A), an excavation hole 12 having a substantially rectangular horizontal section is excavated and formed to a predetermined depth in the ground using a kelly excavator 14. When the formation of the excavation hole 12 is completed, as shown in FIG. 1 (B), the rebar cage 16 is built in the excavation hole 12 using the crane 18. The rebar basket 16 is assembled in advance in a shape corresponding to the shape of the excavation hole 12.
[0010]
A member indicated by reference numeral 17 shown in FIGS. 1 (B) and 1 (C) is a locking pipe inserted and installed at the end of the excavation hole 12 in order to secure the connection of the underground continuous wall panel to the side. It is.
When the rebar basket 16 is erected at a predetermined position in the excavation hole 12, as shown in FIG. The casting of the concrete C is performed so as to replace the concrete C with the stabilizing liquid 10 filled in the excavation hole 12.
[0011]
The process of constructing such underground continuous wall is the same as a conventionally well-known method, but in the present embodiment, in particular, the following description will be given in order to confirm the filling state of the poured concrete C. The method is adopted.
That is, a plurality of sensors 20 are arranged at predetermined intervals along the depth direction of the excavation hole 12 in the rebar cage 16 built in the excavation hole 12. The sensors 20 are arranged along the longitudinal direction of the reinforcing bar cage 16 at the center and the end portions in the left-right direction. Although only one surface is shown in FIG. Are arranged in the same manner on the back side of the camera.
[0012]
FIG. 2 shows details of the mounting state of the sensor 20. The sensor 20 includes a flat insulating substrate 20a, a pair of electrodes 20b opposed to each other at a predetermined interval on the substrate 20a, a lead wire 20c connected to each electrode 20b, and a lead wire connected to the electrode 20b. And an insulating cover 20d that covers the connection portion of 20c. The pair of electrodes 20b is formed in a plate shape or a rod shape made of a metal such as copper having good electric conductivity. In each sensor 20, an insulating substrate 20a is fixed to a portion of the vertical bar 16a of the reinforcing bar cage 16 by bonding or the like.
[0013]
Each lead wire 20c is extended to the upper end side along the longitudinal direction of the reinforcing rod cage 16 and connected to a measuring device 22 installed on the ground. The measurement device 22 supplies a low DC voltage, for example, a voltage of about 6 V, between the electrodes 22 b of each sensor 20 for a short time, for example, about several meters to several tens of seconds, and measures the residual voltage between the electrodes 20 b. I do.
[0014]
The residual voltage at this time differs depending on the electrical properties of the substance interposed between the electrodes 20b. By measuring the residual voltage, the substance interposed between the electrodes 20b can be known. 3 to 5 show the state and results of a test in which it was confirmed that the substance was identified by measuring the electrical characteristics of the substance interposed between the electrodes 20b with the sensor 20 having the above-described configuration.
[0015]
In this test, as shown in FIG. 3, a sensor s is suspended and supported in a container, a stable liquid is filled in the container, concrete is filled from below the container, and the sensor is gradually moved up the top end surface of the concrete. The residual voltage during s was measured. A stainless steel rod having a diameter of 2 mm was used as an electrode of the sensor s, and a DC voltage of 6 V was supplied between the electrodes for 20 msec. After a lapse of 40 msec, a switch was switched to measure a residual voltage between the electrodes.
[0016]
The measurement pitch at this time was 5 seconds. 4 and 5 show the measurement results at this time. As is clear from the figure, when only the stabilizing liquid is used, the residual voltage is about 1200 mv, and when it comes into contact with concrete, the voltage temporarily rises to about 1500 mv. And in concrete, residual voltage falls to about 1300-1400mv.
[0017]
In other words, the magnitude of the residual voltage is in the order of the stabilizing liquid in contact with the concrete> the concrete> the stabilizing liquid, and there is a difference of 100 mv or more between them, and the residual voltage once rises and thereafter decreases. The distinction between concrete and concrete is quite possible. In this test, concrete having a high fluidity with a slump value of about 24 cm was used.
[0018]
FIG. 5 shows the result of measuring the residual voltage between the electrodes 20b by attaching the sensor 20 to the reinforcing bar 16 at an actual construction site based on the above experiment, and a reference value (a value obtained by the above test). Is shown. As is clear from the results shown in the figure, the behavior of the residual voltage in the actual panel and the reference voltage show almost the same tendency, which indicates that the filling condition during concrete placement in the actual panel is good. You can check.
[0019]
Now, when the reinforced cage 16 on which the sensors 20 are arranged as described above is built in the excavation hole 12 and concrete is cast by the tremy tube 19, the respective sensors 20 arranged on the reinforced basket 16 are driven by concrete C. Until just before setting, all the sensors 20 are present in the stabilizing solution 10.
Therefore, in this state, when a low voltage is supplied to the electrode 20b of each sensor 20 via the measuring device 22 for a short time and the measurement of the residual voltage between the electrodes 20b is measured, the measured value of each sensor 20 becomes stable. The residual voltage of the liquid 10 becomes almost the same measured value in all the sensors 20.
[0020]
Such measurement of the residual voltage is performed at predetermined time intervals from the measuring device 22. When the position of the top end of the concrete C is gradually increased by placing the concrete C, the residual voltage is disposed below the reinforcing bar cage 16. It will be buried in the concrete C that has been sequentially cast from the sensor 20.
In the sensor 20 buried in the concrete C, since the magnitude of the residual voltage is smaller than that in the case of the stabilizing liquid 10, it is confirmed in real time that the concrete C has been launched to the position of the sensor 20 and has been filled.
[0021]
In such a method of checking the state of filling, accurate and uniform results can be obtained because the method does not rely on the intuition of a technician. Further, in the sensor 20 of the present embodiment, the residual voltage when a low voltage is applied for a short period of time rises once the stabilizing liquid 10 comes into contact with the concrete C, and then falls, so that the residual voltage is simply reduced. The state can be clearly recognized as compared with the case where the concrete C is lowered, and a stable position after the descent of the residual voltage is stopped can be set as the top end position of the concrete C that has been cast. Can be measured.
[0022]
When measuring the top position of the concrete C, the measurement can be performed, for example, even if the sensor s is installed in a down swing without depending on the configuration of the above embodiment. Further, the sensor 20 of the present embodiment has a pair of electrodes 20b formed on the insulating substrate 20a and has a small thickness, so that it is possible to easily attach even a high-density reinforcing bar arrangement portion.
[0023]
In the above embodiment, the case where the present invention is applied when constructing an underground continuous wall is exemplified. However, the present invention is not limited to this. It can also be applied to the construction of cast-in-place piles in which to build.
Further, in the above-described embodiment, the sensor 20 that detects a substance interposed between the electrodes 20b based on a difference in residual voltage is illustrated. However, the embodiment of the present invention is not limited to the case where such a sensor 20 is used. Instead, for example, a sensor that detects an intervening substance from the difference in electric resistance of the substance interposed between the electrodes may be used.
[0024]
【The invention's effect】
As described above in detail in the examples, according to the method for checking the filling condition of cast concrete according to the present invention, the filling condition can be confirmed in real time during concrete placing, so that there is an inconvenience. , Can respond quickly. Further, in the present invention, since the filling status is confirmed by the sensor, a uniform result can be obtained without individual differences, and it can be arranged also in the high-density portion of the bar arrangement.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional explanatory view sequentially showing steps in a case where a method for checking a filling state of cast concrete according to the present invention is applied to construction of an underground continuous wall.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is an explanatory diagram of a test state of a sensor used in the confirmation method of the present invention.
FIG. 4 is a graph showing test results obtained in the test of FIG.
FIG. 5 is a graph showing measurement results of a verification experiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 Stabilizing liquid 12 Drilling hole 16 Reinforcing cage 19 Ptolemy tube 20 Sensor 20a Insulating substrate 20b Electrode 20c Lead wire 22 Measuring device

Claims (3)

Reinforcing a reinforcing steel cage in a ground excavation hole excavated while filling the stable liquid, when casting concrete, in the method of checking the filling state of the concrete,
A plurality of sensors are pre-arranged in the reinforced cage at predetermined intervals along the depth direction of the excavation hole, and the concrete is lifted due to a difference in electrical properties of a substance interposed between electrodes of the sensors. A method for confirming a filling state of cast concrete, characterized by detecting a position. The method according to claim 1, wherein the electrical property is a residual voltage between the electrodes after a low voltage is applied between the electrodes for a short time. 3. The method according to claim 2, wherein the point at which the residual voltage rises and then decreases and stabilizes is the top position of the poured concrete. Confirmation method.

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