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【FAQ】Electrical product related knowledge
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The double tap has a large current and can be used for IP testing to get more accurate data.
High-density apparent resistivity method is an array prospecting method, also known as automatic apparent resistivity system, which is developed from direct current method. Its function is equivalent to the combination of quadrupole sounding and electrical profiling method. The artificial electric field is formed by supplying electricity to the underground through electrodes. The distribution of the electric field is closely related to the distribution of the resistivity of the underground rock and soil medium. By measuring the artificial electric field at different parts of the surface, the distribution of the apparent resistivity of the underground medium is understood, and the underground geological structure is inferred and interpreted based on the distribution of the apparent resistivity of the rock and soil medium.
The principle of high-density electrical method is the same as that of traditional resistivity method. It is a combination method of multiple devices and multiple pole distances that integrates electrical depth sounding and electrical profiling method, which can obtain the conductivity characteristics of two-dimensional underground media. It has the characteristics of multi-device data acquisition in one pole arrangement, and highlighting abnormal information by obtaining ratio parameters, which greatly increases the amount of collected data, improves work efficiency, and ensures the accuracy and reliability of the pole running process.
This method is particularly sensitive to the water content of the surrounding rock. If the surrounding rock is broken and contains water, its apparent resistivity is significantly reduced. The apparent resistivity of intact and hard rock and soil is significantly higher than that of the surrounding rock in the fault zone or broken zone and water-rich zone. This method has a clear principle and intuitive images. It is a geophysical method with high resolution. In recent years, with the improvement of computer data acquisition technology, the exploration efficiency has been greatly improved, the coverage area and detection depth of the profile have been increased, reliable data can be obtained in a strong interference environment, the signal-to-noise ratio has been greatly improved, and the geological body can be accurately detected. This method has been widely and successfully applied in engineering and hydrogeological exploration and exploration of mineral and water resources.
(1) Application in coalfield and mine goaf detection
(2) Non-destructive detection of termite nests in dam foundations
(3) Karst and foundation surveys of railways, roads and tunnels
(4) Delineation of stratum lithology boundaries
(5) Survey of the leakage range of landfills
(6) Ancient tomb surveys
(7) Detection of sewage pipes
(8) Non-destructive testing of leakage in reservoirs and river dams
(9) Detection of bedrock fracture zones
(10) Soil salinity and water quality surveys
(11) Detection of ancient tunnels, air-raid shelters, metal burial sites, etc.
(1)The high-density resistivity method is based on the resistivity method, so it is suitable for all underground explorations with obvious conductivity differences;
(2)Any medium underground will have a weak polarization potential at the moment of power on and off, which will affect our measurement of the true potential difference. When the electrode distance is small, the loop current is large, which has little effect on the measurement results; when the electrode distance is too large, the interference potential is close to the effective potential, which has a greater impact on the measurement results. Therefore, due to the influence of the power supply electrode distance, the exploration depth cannot be too large, generally within 100m. When the conductivity of the soil medium is good, it can be appropriately increased, and the exploration depth in the soil medium with poor conductivity is appropriately smaller;
(3)It is generally less used in cities, near large transmission lines, etc. due to site restrictions and industrial stray current interference; 4. In areas such as concrete pavements and exposed bedrock surfaces, it is also less used due to the difficulty of electrode layout.
(1) Selection of equipment
There are more than a dozen data observation devices for high-density electrical method. In actual work, due to factors such as time, it is impossible to observe each device. Individual devices must be selected for data collection in a targeted manner. As we all know, the quality of measured data is the key to the success or failure of interpretation. Different arrangement devices should be selected according to different geological tasks to achieve the best exploration effect.
(2) Selection of electrode spacing
The electrode spacing of high-density electrical method includes the power supply electrode spacing and the measurement electrode spacing. The power supply electrode spacing directly affects the detection depth, while the measurement electrode spacing affects the lateral resolution of the detection. Therefore, when designing the electrode spacing, both the detection depth and the lateral resolution must be fully considered. Studies have shown that the dipole-dipole device has the best resolution, followed by the dipole device, and the symmetrical quadrupole is the worst.
(3) Data observation
In actual work, in addition to selecting a suitable observation device, data observation is also an issue that must be considered. Because the power supply current is limited, in order to obtain reliable data, the observed electrode potential cannot be too small. Under the same pole distance, the observed potential difference of the dipole-dipole device is smaller than that of the two-pole device and the symmetrical quadrupole.
(4) Interpretation of results Under the use of reasonable methods, the effective interpretation of data is the key to application. The high-density electrical profile is an apparent resistivity imaging map. The high-resistance area represents dense rock mass, good integrity, and low water content; the low-resistance area represents water-bearing, loose and broken rock mass or fractured water-bearing zone. Karst cavities show high-resistance areas, and caves filled with clay and water show low-resistance areas. Most karst caves and karst fracture zones are partially filled, with cavities in the upper part and loose filling in the lower part. The upper part shows high resistance and the lower part shows low resistance, forming a discontinuous beaded combination abnormal area.
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