SOLUTION

Large depth exploration

Cave detection

Cave exploration

Hollow road surface

Highway inspection

Tunnel lining

Disaster emergency response

Slope monitoring

Reservoir monitoring

Flash flood discharge

Structural defects

Geological karst cave

Water conservancy anti-seepage wall quality inspection

Related plans：

Using radar center frequency: GPR100MHz Shielding antenna detection

1. Water conservancy anti-seepage wall detection

An anti-seepage wall is a continuous wall built in a loose, permeable layer or in an earth and stone dam (weir) to prevent seepage. Commonly used plastic in engineering Concrete anti-seepage wall The technology has been widely used in the risk prevention and reinforcement of embankment projects, achieving good results. However, the strength and impermeability of plastic concrete anti-seepage walls are low, and their durability is poor. 。

Generally, anti-seepage walls are vertical structures on dams, with thin walls and complex boundary conditions. The working surface available for quality inspection is narrow. Ground penetrating radar (GPR) is a non-destructive testing technology with the characteristics of fast detection speed, high detection accuracy, and the ability to obtain continuous detection results. It has good detection effects in detecting whether the anti-seepage wall is continuous, whether there are cracks, fissures, and voids in the wall, etc., and has broad application prospects in the quality inspection of anti-seepage walls in hydraulic structures.

2. Principle of geological radar detection

The ground penetrating radar method uses high-frequency electromagnetic waves in the form of wideband short pulses to be sent into the ground directionally through a transmitting antenna. The electromagnetic wave signals propagate in the underground medium. When encountering underground media or target bodies with significant differences in dielectric properties, the electromagnetic waves will be reflected, transmitted, and refracted. The greater the difference in dielectric constant between the two media, the greater the energy of the reflected electromagnetic waves. The reflected electromagnetic waves are received by the receiving antenna that moves synchronously with the transmitting antenna, and the motion characteristics of the reflected electromagnetic waves are precisely recorded by the radar host. When the transmitting and receiving antennas move continuously, a radar image or waveform diagram can be formed. By analyzing and processing the image or waveform, and based on its waveform, intensity, and geometric morphology, the burial depth and distribution characteristics of underground objects can be judged.

Electromagnetic wave propagation schematic diagram

3. Important parameters

Dielectric constant: Describes the ability of a material to store and release electromagnetic energy. It is usually expressed as a dimensionless relative dielectric constant, where:

The dielectric constant of free space is 。

Relative Dielectric constant table

Reflection coefficient:

The reflection coefficient is represented by R where is the upper relative dielectric constant, is the lower relative dielectric constant.

The intensity of the reflected signal mainly depends on the electrical difference between the upper and Lower layers of the medium ， The greater the electrical difference, the stronger the reflected signal . The larger the difference in electromagnetic properties between the media on both sides of the interface, the stronger the reflected wave and the greater the reflection amplitude. The properties of the media on both sides can be determined from the reflection amplitude.

The polarity of the reflected wave: When the wave enters a medium with a higher dielectric constant from a medium with a lower dielectric constant, the reflection coefficient is negative, that is, the amplitude of the reflected wave is reversed, and the reflected wave is in the opposite direction to the incident wave; when entering a high-speed medium from a low-speed medium, the amplitude of the reflected wave is in the same direction as the incident wave.

Determine the material of the pile detected based on the amplitude and polarity. After confirming the material, the distance from the pile head to the pile bottom can be calculated according to the corresponding two-way travel time.

4. Detection method

The profile method, also known as the continuous profile scanning measurement method, is the most commonly used method for geological radar in practical engineering detection. Its working principle is: the transmitting antenna and the receiving antenna maintain a fixed distance and move along the survey line at the same speed, while the reflected signal is continuously read and stored in the radar instrument in the form of data. This detection method has advantages such as speed, continuity, and relatively simple operation, and is suitable for carrying out detection work in a larger range.