CN110568029A

CN110568029A - nondestructive detector for internal defects of building

Info

Publication number: CN110568029A
Application number: CN201910881595.9A
Authority: CN
Inventors: 何书耕; 李启成
Original assignee: Liaoning Technical University
Current assignee: Liaoning Technical University
Priority date: 2019-09-18
Filing date: 2019-09-18
Publication date: 2019-12-13

Abstract

A nondestructive detector for internal defects of buildings is a construction engineering quality detection device which is simple and convenient and can accurately position the internal defects of the buildings. The direct current power supply, the switch, the ammeter and the power supply electrodes A and B are connected together by a lead to form a power supply circuit; the measuring electrodes M and N and the voltmeter are connected together by a lead to form a measuring circuit. During detection, measuring points with equal intervals are established on the surface of a detected building, and the electrode intervals are set. When the nondestructive detector in the building is moved along the measuring points, the voltmeter and the ammeter representation are recorded, the device coefficient is recorded, and the apparent resistivity of each measuring point is calculated by a formula. The electrode spacing is adjusted to carry out multiple measurements, thereby achieving the purpose of measuring different depths. If the apparent resistivity in the building is uniform, the building is free of defects; if not, it is indicated to be defective. If the program control electrodes are installed at each measuring point and connected with a computer through a multi-core cable, the automation of data storage and processing can be realized.

Description

Nondestructive detector for internal defects of building

Technical Field

The invention relates to an engineering quality detecting instrument for accurately positioning internal defects of a completed building.

background

the method for detecting the internal defects of the building is clear in principle and simple to operate, and the method utilizes the ultrasonic detection principle that sound waves are transmitted at one end of the building suspected to have the defects and received at the other end of the building, and the sound waves are generally 20 ~ 150KHz ultrasonic waves, so that whether the defects exist in the building or not is determined by measuring the wave speed^[1]. But the steel pipes need to be embedded, so that the method is troublesome, high in cost and difficult to popularize, and the integrity of the building, especially the pile foundation, cannot be detected; when the wave velocity is measured, the distance between the receiving end and the transmitting end is far relative to the size of a building, so that the position of the defect cannot be determined more accurately. So that the nondestructive inspection of the internal defects of the buildings, which can be accurately positioned and conveniently used, is required to be manufactured by engineering practiceand (5) measuring an instrument.

[1] Li Shifeng, gold eye Queen, Zhoujunjie, Chapter [ M ] third chapter of resources and engineering geophysical prospecting, chemical industry Press, Beijing: 2007.

Disclosure of Invention

Since ultrasonic exploration from the point of wave emission to the point of wave reception may be a defect point inside a building, it is difficult to accurately locate the defect using ultrasonic exploration. The invention adopts electrical prospecting, and four electrodes (two power supply electrodes and two measuring electrodes) are moved on a building to be measured, so that the apparent resistivity of each depth in the building is measured. If the measured apparent resistivity of all the positions in the building is uniform, the building is free of defects, otherwise, the apparent resistivity abnormal points are the points of defects in the building. Compared with ultrasonic exploration, its beneficial effect is: the position of the defect in the building is more accurately positioned, and a large-range measurement can be carried out at one time.

Theoretically, assuming that the potential at infinity is zero, the potential generated by a point source at a point is:

（1）

In the formula (1), U is the potential of a measuring point, I is the current intensity of a point power supply,The apparent resistivity of the medium, r, is the distance from the measurement point to the point power supply.

If A, B, M, N are in a straight line. The two electrodes A and B are powered simultaneously and are called as power supply electrodes; measuring the potential at two measuring electrodes M and N, M and N being called measuring electrodes, then:

（2）

The potential difference generated between the measurement electrodes M and N is:

（3）

From equation (3), we can obtain:

（4）

In equation (4):

（5）

Equations (4) and (5) are theoretical equations for calculating apparent resistivity.

In actual measurement, a series of electrodes are arranged on the surface of a measured building at equal intervals, and the electrodes are fixed on the surface of the building by conductive glue. Supplying power to the building with two power supply electrodes A and B, measuring the supply current with an ammeter, and measuring the voltage between the electrodes M and N with a voltmeter; and calculating a device coefficient K according to the distance between the power supply electrode and the measuring electrode, and calculating the apparent resistivity of the measured point according to the formulas (4) and (5). And moving the power supply electrode and the measuring electrode to change the measured point, so that the apparent resistivity of a series of measured points can be obtained. If the apparent resistivity of each point is relatively uniform, the interior of the building is free from defects, otherwise, the defects exist.

If the measured apparent resistivity data is stored and processed by a computer, a profile of the apparent resistivity is obtained, and the defect distribution in the building is clear.

the invention can mainly detect the engineering quality in the following aspects.

Firstly, nondestructive testing of internal defects of the building after the completion of the building engineering.

And secondly, quality inspection after engineering grouting.

thirdly, the safety of the buildings which are repaired for a long time and the buildings after the earthquake are evaluated.

According to the current electrical instrument manufacturing level, the power supply voltage between the power supply electrodes can reach 900V, and the maximum power supply current can reach 5A. In practice, in buildings, especially buildings with small construction scale, the supply voltage and current can be greatly reduced from the practical point of view of safety.

Drawings

FIG. 1 is a schematic view of a nondestructive detector for internal defects of a building.

FIG. 2 is a schematic view of wiring of the measuring points of the nondestructive testing apparatus for the internal defects of the building.

Claims

1. A nondestructive detector for internal defects of buildings is an engineering quality detector for conveniently and accurately positioning the internal defects of the buildings, and is a four-electrode device mainly composed of two power supply electrodes, two measuring electrodes, a direct-current power supply, a voltmeter, an ammeter, a switch and a lead.

2. During measurement, measurement points are arranged at equal intervals along a measuring line of a measured building.

3. After the electrode spacing is set and the device coefficient is calculated, the quadrupole device moves along the measuring line for measurement, the ammeter and the voltmeter representation number are recorded, and the apparent resistivity of each measuring point is obtained through calculation.

4. The method is characterized in that: if the apparent resistivity is uniform, the interior of the building is free of defects; if the apparent resistivity is not uniform, it indicates that there is a defect inside the building.

5. The position where the unevenness of the apparent resistivity occurs is a defect position.

6. the nondestructive detector for internal defects of buildings according to claim 1, wherein: during measurement, the distance between the two measuring electrodes is fixed, and the distance between the two power supply electrodes can be changed.

7. the nondestructive detector for internal defects of buildings according to claim 1, wherein: the wire is connected with a direct current power supply, a power supply electrode, a switch and an ammeter to form a power supply system; the wire is connected with the measuring electrode and the voltmeter to form a measuring system.

8. The nondestructive detector for internal defects of buildings according to claim 1, wherein: before the test is performed, the power supply system and the measuring system are disconnected.