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Groundwater environment is closely related to the protection and restoration of surface ecological environment, and the detection of groundwater resources is an important content to master the characteristics of groundwater environment. In the setting of the ecological restoration of Hongshaquan Open-pit Mining Area, four different geoelectric models are constructed on the basis of geological column and its resistivity logging curves obtained by a borehole. Based on one-dimensional forward theory, the transient electromagnetic induced voltage and its apparent resistivity response curves with a small coil device are obtained. Comparative analysis for these curves shows that induced voltage and its apparent resistivity under different aquifer geoelectric model conditions are sensitive to aquifer water-bearing response, and there are obvious differences between them in 0.01-50 ms, which reflects the feasibility of using small coil transient electromagnetic method to detect groundwater resources in the study area in theory. Combined with the field detection test data and drilling exposure, the effectiveness and reliability of small coil transient electromagnetic technology in the detection of groundwater resources are verified.

Water accumulation detection in mining areas is the primary technical means for preventing mine water disasters. To study the distribution of water accumulation in the goafs of the Xingnong coal mine in Jixi, the present paper systematically analysed the water accumulation regularities in the goafs based on the applied and theoretical studies using transient electromagnetic (TEM) methods for the detection of goaf water accumulation characteristics. Because of the high sensitivity of transient electromagnets to low resistance and water, the water body distribution in the goafs is determined by the exhibition of low resistance by the water bodies. Furthermore, the water-bearing anomalies are located depending on the conductivity difference among media. The analysis of the in situ measurements for the Xingwang coal mine revealed four water-rich goaf anomalous zones within the detection area, of which one was located in the shallower part and three were located in the deeper part. The water-retention capacity of the fault zones was analysed, with more reliable degree of control attained by analysing a fault with a large throw. A broad area of highly distinct low-resistance anomalies appeared in the vicinity of the fault. The suspicious water-containing anomalies were verified through field drilling experiment, proving the reliability of TEM in detecting the water distribution in the coal mine goafs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multiturn coils is an effective transmitter for transient electromagnetic method (TEM) used in narrow space and complex terrain at presently. However, its high mutual inductance coupling and long turn-off time affect the quality of later data processing and interpretation. Compared with multiturn coils, the new conical source has low mutual inductance and short turn-off time. Based on the superposition principle, we use Hankel transform and numerical filtering method for forward modelling of the conical source field in the layered-media and explore TEM characteristics excited by this source. We apply improved damped least square inversion to integrated transient electromagnetic (TEM) data. We first invert the induced voltage into similar resistivity and apparent depth, and then use the inverted results as input parameters in the initial model and transform the apparent resistivity data into the frequency domain. Then, damped least square inversion is performed in the frequency domain using the initial model. Subsequently, we use automated model building to search for the extremes and inflection points in the resistivity-depth data that are treated as critical layer parameters. The inversion of theoretical and observed data suggests that the method modifies the resistivity and depth and yields a model of the underground layers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Small multi-turn coil devices are used with the transient electromagnetic method (TEM) in areas with limited space, particularly in underground environments such as coal mines roadways and engineering tunnels, and for detecting shallow geological targets in environmental and engineering fields. However, the equipment involved has strong mutual inductance coupling, which causes a lengthy turn-offtime and a deep 'blind zone'. This study proposes a new transmitter device with a conical-shape source and derives the radius formula of each coil and the mutual inductance coefficient of the cone. According to primary field characteristics, results of the two fields created, calculation of the conical-shaped source in a uniform medium using theoretical analysis, and a comparison of the inductance of the new device with that of the multi-turn coil, show that inductance of the multi-turn coil is nine times greater than that of the conical source with the same equivalent magnetic moment of 926.1 A·m. This indicates that the new source leads to a much shallower 'blind zone.' Furthermore, increasing the bottom radius and turn of the cone creates a larger mutual inductance but increasing the cone height results in a lower mutual inductance. Using the superposition principle, the primary and secondary magnetic fields for a conical source in a homogeneous medium are calculated; results indicate that the magnetic behavior of the cone is the same as that of the multi-turn coils, but the transient responses of the secondary field and the total field are more stronger than those of the multi-turn coils. To study the transient response characteristics using a cone-shaped source in a layered earth, a numerical filtering algorithm is then developed using the fast Hankel transform and the improved cosine transform, again using the superposition principle. During development, an average apparent resistivity inverted from the induced electromotive force using each coil is defined to represent the comprehensive resistivity of the conical source. To verify the forward calculation method, the transient responses of H type models and KH type models are calculated, and data are inverted using a 'smoke ring' inversion. The results of inversion have good agreement with original models and show that the forward calculation method is effective. The results of this study provide an option for solving the problem of a deep 'blind zone' and also provide a theoretical indicator for further research. [ABSTRACT FROM AUTHOR]

To diagnose breakpoints and corrosion situation of grounding grids in the case of no power outages and digging，the paper proposes an idea based on transient electromagnetic method. It gets transient electromagnetic response of the grounding grids model driven by step waves，using COMSOL Multiphysics to simulate. It uses MATLAB programming to calculate the apparent resistivity of grounding grids model. And the profile of apparent resistivity is obtained by the mapping function of surfer. The paper takes the shape of Chinese character ri as an example， comparing the profiles of apparent resistivity measured in different conditions of the grounding grids, including in good condition，half the middle width and with left or middle breakpoints，the result verifies the correctness of the method applied in fault diagnosis of grounding grids. [ABSTRACT FROM AUTHOR]

Detecting the location of coal mine fire zone accurately is a hot subject today in coal mine safety discipline. Based on the transient electromagnetic method, the apparent resistivity of the roadway ahead were calculated, and advanced detection and cross-section detection were studied. The results show that the mine transient electromagnetic method is a fast, efficient and convenient detection technology which can locate underground coal mine fire area accurately. It can also provide a scientific basis for the subsequent mine fire prevention project of this coal mine. [ABSTRACT FROM AUTHOR]

The corrosion of buried metal pipelines can result in potentially fatal personal injuries and economic losses. In this paper, a transient electromagnetic method is used for the non-destructive testing of in-service buried metal pipelines in a trenchless state. We solve the implicit function equation to obtain the time domain apparent resistivity, which is time-depth transferred based on the smoke ring inversion theory. We then obtain a profile map of the apparent resistivity distribution of the buried medium to display the corrosion positions and the corresponding degree. The test results for the corrosion positions are verified as being generally consistent with the actual corrosion situation, only producing errors with regard to the corrosion boundary positioning. The results demonstrate that the transient electromagnetic method is a valid and practical method for testing of the corrosion of buried metal pipelines. [ABSTRACT FROM AUTHOR]

In order to study dynamic propagation characteristics of coal reservoir water system during drainage process of coalbed methane well, based on different electrical conductivity of different lithology and water content of coal strata, a CBM production well in Qinnan area was chosen to conduct transient electromagnetic dynamic detections of coal reservoir water system before drainage and after half a year respectively. A rectangular survey grid of 400 m x 300 m was set up with 16 survey lines perpendicular to the strata strike and 400 survey points distributed in each line, resulting in an observation coordinate network of 20 m x 10 m within the survey grid. By means of data acquisition, data processing and quantitative interpretation, apparent resistivity bedding slice chart, comparison diagram of coal apparent resistivity and apparent resistivity section of each survey line and point were available before drainage and after half a year. The analysis results show that, distribution of coal reservoir water system is relatively uniform before drainage, while its anisotropy becomes very obvious after half a year. In the poor connectivity regions, apparent resistivity of coal seam and roof sandstone increases in different degrees because static water reserves of coal reservoir water system are partly dewatered, to the contrary, that of coal seam and roof sandstone in the preferable connectivity regions decreases in a certain range because of hydraulic dynamic supply. [ABSTRACT FROM AUTHOR]