JPS5850224A - Slime detector - Google Patents

Abstract

PURPOSE:To prevent the lowering of the bearing force of concrete due to the generation of slime by a method in which a slime sensor is integrally provided to the tip of a tremie tube, the presence of settled slime is detected, and then concrete is placed through the tremie tube. CONSTITUTION:A pit is excavated by an excavator in the ground and then a stabilizing liquid 2 is filled in the pit 1 to stabilize the wall of the pit, where slime 3 is settled on the bottom of the pit. An iron bar cage 4 is inserted into the pit 1, a tremie tube 5 having a slime sensor 6 on its tip is penetrated, and when the presence of slime is detected, the harmful slime is removed by an air lift method or a suction pump. After the slime removing operation is finished by using the sensor 6, fresh concrete is placed through the tremie tube 5 for concreting work.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting slime, particularly harmful slime, in mechanical excavation methods.

There are various types of mechanical excavation methods, called cast-in-place concrete piles, but the basic method is to dig a deep hole at the construction site while filling the soil with a stabilizing liquid to stabilize the hole wall. The key point is to erect reinforcing bars and pour concrete from tremie pipes to form the foundation piles.

In this mechanical excavation method, slime is deposited at the bottom of the excavation hole. Slime is the result of sediment scraped from the hole wall during excavation or reinforcing, or sediment suspended in some form in the stabilizing liquid at the bottom of the hole.

There are various types of slime, ranging from small to large densities, but slimes with particularly high densities must be completely removed before concrete placement, otherwise they will have the following negative effects.

(1) A soft slime layer is interposed between the concrete pile and the supporting ground, reducing the supporting capacity of the pile.

(2) Slime gets mixed into the concrete, degrading the quality of the concrete itself, and forming spots in the concrete piles.

(3) Decrease the adhesion between concrete and reinforcing cage.

Today, as buildings become larger and taller, it is no longer acceptable for even one of the many foundation piles to be defective as described above.

Therefore, in the mechanical excavation method, a major challenge is to establish a method for removing slime, especially harmful slime, that is, a series of methods to detect the presence of harmful slime, remove it, and confirm that it has been removed. .

Conventional methods for removing slime include the air lift bottom giri method, in which compressed air is ejected from the tip of the tremie tube and the slime is discharged together with a stabilizing liquid, or the slime is removed by injecting clean water from the injection holes placed around the tip of the tremie tube. A well-known method is the jet bottom roughening method, in which concrete is poured into the air before it sinks again.

However, conventionally, most of these methods rely only on the experience and intuition of field workers, and they do not detect the presence or absence of residual slime after slime removal work, so the type of drilling method, the soil quality of the hole wall, These removal methods alone are not sufficient to completely remove slime, especially harmful slime, whose production amount varies greatly depending on the stabilizer liquid components, underground water level, etc.

In addition, as a conventional method for detecting the presence of slime, -
A scaled cable with a weight embedded in the lamp electrode at the tip is lowered to the bottom of the excavation hole before concrete pouring, and the electrical conductivity or electrical resistance between the electrodes is observed on the ground. Attempts have been made to detect the interface between slime and slime. This method is based on the phenomenon that electrical conductivity differs between the slime part and the muddy water part. After pulling up the cable, a slime removal pipe is inserted into the excavation hole to remove slime.

In this case, in order to confirm whether the slime had been completely removed, it was necessary to pull up the slime removal pipe from the excavation hole, then lower the cable again and measure the electrical conductivity. . Therefore, since there is a considerable amount of time between slime removal and concrete pouring, there is a possibility that slime deposition will progress again during that time, and if the above detection method is applied to all of the many excavated holes at a single work site, work efficiency will be reduced. There is a problem of a significant decrease. Therefore, this method has not become widespread to date due to the effects obtained.

The present invention has been made to solve the above problems, and includes integrally providing a slime detection sensor at least at the tip of the tremie tube.

When harmful slime is detected by the signal of the sensor, the slime can be removed by the slime removal means, or the presence or absence of residual slime can be checked afterwards, and concrete can be poured from the tremie pipe immediately after the residual slime is gone. The purpose of the present invention is to achieve the above object by configuring the system so that it is possible to do so.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an underground sectional view of an excavation hole showing a state in which an embodiment of the present invention is applied. 1 is a hole excavated by an excavator, the hole is filled with a stabilizing liquid 2 for stabilizing the hole wall, and slime 3 is deposited on the bottom of the hole. 4 is probably a reinforcing bar, and 5 is a tremie tube. The tremie tube 5 is made up of a necessary number of sections of appropriate length such as 5a, 5b, and 5c that are spliced together to obtain a predetermined length. Although not shown, the tremie pipe 5 is equipped with a known slime removal device inside or outside, and has an open bottom end, so that concrete is poured into the pipe from the top end and pulled up. A slime detection sensor 6 is provided at the tip of the tremie tube 5, and its signal line and power line are embedded in the wall of the lowest part of the tremie tube 5 and rise to an appropriate height, where the slime detection sensor 6 is installed. It is connected to a cable 8 through a waterproof connector 7, and the cable 8 is led to the ground surface and connected to a signal processing circuit 9. Further, a sensor 10 having the same characteristics as the sensor 6 provided at the distal end is also provided at the upper part of the tremie tube 5.

As the sensor 6.10, a plurality of types of sensors such as the pair of electrodes for measuring the electrical conductivity or electrical resistance value described above are used to increase the reliability of determining the harmfulness of the deposited slime.

The sensor 6 at the tip can be mounted on the outside or inside of the tip of the tremie tube 5, or on the thick part of the tube. It is preferable that two paired sensors such as electrodes are placed side by side at the same horizontal position.

FIG. 2 is a block diagram showing one embodiment of the signal processing circuit 9, and shows a case where two types of sensors are used.

Reference numeral 11 denotes an operation panel consisting of an input section 12 and an output section 13 including a suitable interface circuit. A memory 15 includes RAM and ROM, and a microprocessor 14 connects to the input section 13.
It stores the coefficients for converting the signal from the computer into digital output, calculations, and other program execution procedures. 16-1 and 16-2 are D/A converters that convert digital signals from the microprocessor 14 into analog signals, and two or more D/At converters are also provided so that two or more types of sensors can be used. There is. 17 is a power supply circuit, which connects the sensors 6, 1 to the power supply line 8-1 in the cable 8 via the connector 18.
0 and other sensors. 8-2 and 8-3 are signal lines from the sensors, and the sensor currently connected to the signal line 8-2 is an electrode for measuring electrical resistance, and as shown in FIG. One pair (A, B) and one pair (C.

D) is provided, and the sensor connected to the signal line 8-3 is a sensor based on another principle, such as a sensor provided at the position of the sensor 6 and using color or light. 19 is a bridge circuit for the outputs of the electrical resistance measurement sensors 6 and 10, as shown in FIG. 4, which will be described later;
20-1 is an amplifier circuit that amplifies the output of the bridge circuit 19. 4-1 is a comparator that inputs the output signal of the D/A converter 16-1 and the output signal of the width amplification circuit 19-1 and compares the magnitude thereof; and 7 outputs the result to the microprocessor 14. be. 20-241 Amplification circuit used when a sensor is also connected to signal line 8-3, 2l-2
The output signal of the amplifier circuit 20-2 of t'i-t and the output signal of the D/A converter 16-2 are inputted and compared in magnitude,
It is a comparator that outputs the result to the microprocessor 1.4'.

No. 4- is the bridge circuit 19, RAB is the resistance value between the electrodes ^ and B of the sensor 6 arranged as shown in FIG. 3, RcD is the resistance value between the electrodes C and D of the sensor 10, and 22 .23 is each reference resistance. Output is terminal 2
Obtained from 4.

In order to construct a concrete pile using the slime removal apparatus configured as described above and set as shown in FIG. The microprocessor 14 inputs the signal from the input section 12, converts the input signal into a digital signal according to the conversion coefficient stored in the memory 15, and outputs the digital signal to the D/A converters 16-1 and 16-2. D/A converter 16-1
and 16-2 provide reference level signals to comparators 21-1 and 21-2, respectively. In other words, the microprocessor 14 has given the comparator 21-1, 21-2 a threshold level to determine whether the slime is harmful.

First, the case of a sensor for measuring electrical resistance will be described. Assuming that slime is not deposited or is not harmful even if it is deposited, sensor 6 (AIB)
Since the sensor to(C, D) is placed under the same conditions, the bridge circuit 19 in FIG. 4 is balanced and no output is generated at the terminal 24. Therefore, the amplifier circuit 20
Since the output signal of -1 is smaller than the reference level signal from the D/A converter 16-1, the signal of the comparison result from the comparator 21-1 causes the microprocessor 14 to detect harmful slides and remove harmful slides according to the information stored in the memory 15. It is determined that this does not exist, and the result is displayed from the output unit 13.

Next, there is harmful slime, and as shown in Figure 1 or Figure 3, the lower sensor 6 (A, B) is inside the slime 3, and the upper sensor 1o (C, D) is outside the slime 3. shall be taken as a thing. At this time, the resistance value between the electrodes of each sensor is
The distance between electrodes A and B is larger than that between electrodes C and D, and the fourth
The balance of the bridge circuit shown in the figure is lost and a potential is generated between the terminals 24. When this output potential is amplified by the amplifier circuit 20-1, it becomes higher than the reference level signal from the D/A converter 16-1, so the microprocessor 14 determines that slime is present and sends the result to the output section 13. Display from.

When the presence of slime is detected, while looking at the output unit 13, work to remove harmful slime is started using a known slime removal means (not shown) attached, such as the air lift method, Sankushi, Yon pump, etc. do. When the display on the output section 13 changes from the presence of harmful slime to the absence of harmful slime, the slime removal work is stopped, and fresh concrete is immediately poured from the tremie pipe 5 and concrete is placed.

When a sensor is also connected to signal line 8-3,
A comparator 21-2 connects the amplified signal from this sensor with the D/A
Since the comparison is to be made with the reference level signal from converter 16-2, microprocessor 14 uses comparators 21-1 and 21
It is also possible to determine the presence or absence of harmful slime from both output signals of -2.

In this case, the reliability of determining the presence or absence of harmful slime increases.

In this example, a pair of electrical resistance measurement sensors were installed at two locations, one at the tip of the tremie tube and the other at the top, forming a bridge configuration, making it easy to identify harmful slime. By installing a sensor only at the tip of the tremie tube and comparing the absolute value of electrical resistance or electrical conductivity between the sensor electrodes with the electrical resistance or absolute value of electrical conductivity set by the microprocessor 14, It may be configured to determine the presence or absence of harmful slime. Moreover, conversely, the sensor connected to the signal line 8-3 also has two
It is also clear that it may be reinstalled at a certain location to form a bridge configuration.

In this embodiment, the operator only needs to set the conditions on the input section 12, and the signal processing circuit determines the presence or absence of harmful slime and displays the result on the output section 13, making it easier to work at the site. has advantages. However, it is also possible to use a signal processing circuit that simply displays sensor signals, and for the operator to determine the presence or absence of harmful slime by taking into account surrounding conditions. Therefore, the present invention also includes a device equipped with such a simple signal processing circuit.

FIG. 5 is an underground sectional view of an excavation hole showing a state in which another embodiment of the present invention is applied.

This embodiment differs from the embodiment shown in FIG. 1 in the method of arranging the cable 8 that accommodates the signal line and power line of the sensor. That is, in the embodiment shown in FIG. 1, the cable 8 is disposed outside the tremie tube 5 as separate from the tremie tube 5, whereas in this embodiment, the signal line and the power line are connected to the tremie tube 5. The sensor 6 is completely embedded or integrated into each section 5a, 5b, 5C, etc. of the tremie tube 5.
The cable 8 is connected from the top of the tremie tube 5 to the signal processing circuit 9 via the connector 25. The tremie tube 5 is constructed so that a cable can also be connected by connecting each part between the parts.

In this embodiment as well, as shown in FIG. 1, the same sensor 10 may be installed above, and the sensors 6 and 10 may form a bridge configuration.

In this embodiment, since the cape is made of &)-IPt reasonable pipe 5δ→, there will be no disconnection accident of the cable 8, and the mechanical connection of the tremie tube and the electrical connection of the cable can be achieved at the same time, so it can be done at the site. This has the advantage of making the work easier.

As described in detail above, the present invention has a small number of tremie tubes (one at the tip and a slime detection sensor is integrally provided).
This makes the work of detecting harmful slime much easier, and there is no time lag between removing harmful slime and placing concrete, which eliminates the problem of harmful slime depositing again between removing harmful slime and placing concrete. There is no problem with the process, and the predetermined shape of the tip can be confirmed, making it possible to create stable cast-in-place concrete piles of good quality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an application state of an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a signal processing circuit, FIG. 3 is a schematic front view showing an example of a sensor installation state, and FIG. The figure is a circuit diagram showing a bridge configuration of a sensor, and FIG. 5 is a sectional view showing an application state of another embodiment of the present invention. 1... Excavation hole, 3... Slime, 5... Tremy tube, 6... Slime sensor, 8... Cable, 9
-Signal processing circuit. Patent Applicant Kajima Corporation Sharp Corporation Agent Patent Attorney Aohaku Aogai 2 people Figure 3 Figure 94 Figure 25 No. 511

Claims (1)

[Claims] (1) In the mechanical excavation method, one or more types of slime detection sensors are installed at least at the tip of the tremie pipe, and a signal processing circuit is installed on the ground to process the signals from the sensors, and the deposited slime is harmful. This slime detection device is characterized by determining the sex and checking the shape of the tip of the excavated part.