High Density Resistivity Method Research Articles

Structural Detection and Stability Monitoring of Deep Strata on a Slope Using High-Density Resistivity Method and FBG Strain Sensors

Under the influence of a variety of unfavorable factors, slope instability may occur, so the stability of the slope needs to be analyzed. In this paper, combined with the geological investigation data, the slope engineering geological profiles are derived based on 2D inversion maps of the high-density resistivity (HDR) method to obtain the overburden layer thickness. Then, a finite element model is established based on the mechanical and geometric parameters of the slope to analyze the displacement and deformation characteristics and obtain information about the potential sliding surface. The above analysis results are combined to determine the effective monitoring field and deploy (Fiber Bragg Grating) FBG strain detection piles for deep strain monitoring. The analysis showed that the shape and location of the potential sliding surface of the slope from the numerical simulation are consistent with those delineated by the HDR profile. The monitoring results show the rock and soil on the north side of the slope are soft and have poor stability, which is consistent with the HDR method detection results. Adopting the HDR method to identify the slope’s overall geological structure combined with FBG strain detection piles to obtain the deep deformation provided an effective monitoring technique for slope stability assessment.

Study on The Influence Law of Side Effect of Two-dimensional ERT

As a traditional exploration method, two-dimensional high density resistivity method has been widely used in various projects. However, when using this method for exploration, three-dimensional geological bodies often affect the two-dimensional detection results, which is the side effect of two-dimensional high density resistivity method. Although the three-dimensional high density resistivity method can effectively remove the side effect of the two-dimensional high density resistivity method, the application of the three-dimensional high density resistivity method is often limited by the performance and cost of the instrument. Therefore, it is of great significance to explore the influence law of the side effect of the two-dimensional high density resistivity method. In this paper, through the method of numerical simulation, by comparing the data of different inversion arrays, the influence of abnormal body size, type, different arrays and other factors on the side effect is discussed.

Application of High-density Resistivity Method in Fine Division of Quaternary Geological Structure in the Starting Area of Xiongan New Area

In the starting area of Xiongan New Area, the high-density resistivity method is used for fine detection of the deep-lying strata 0m ∽ 200m in the study area. The stratigraphic and lithologic framework of 0 m-200 m depth has been established. The results show that the middle and Late Pleistocene strata are rich in fine sand, and no hidden ground fissures have occurred. It is proved that the high-density resistivity method is effective and feasible in urban planning and construction geological exploration, and it can provide data support for the further construction of Xiongan New Area.

Investigation of Landslide by Comprehensive Geophysical Exploration in Northeast Chongqing: Taking Xiawafang Landslide as Example

Aiming at the characteristics of geological structure of Xiawafang landslide in Wuxi County, northeast Chongqing, high density resistivity method and seismic image method are used to comprehensively analyze the differences between conductivity and impedance of rock stratum in this area. At the same time, the geological survey results and drilling data are taken as the basis. With the fusion of geology-geophysics analysis and interpretation, this paper shows the characteristics of geological structure and spatial distribution in the exploration area, and landslides can be analyzed according to their mode of deformation and destruction, which provides a basis of comprehensive geology-geophysics interpretation for the treatment of geological landslide.

Application of High Density Resistivity Method in Karst Exploration: A Case Study

Application of High Density Resistivity Method in Karst Exploration: A Case Study

Distribution Characteristics of the Geoelectric Field in Waste Dump Slopes during the Evolution of Instability Sources under Rainfall Conditions

To study the evolution of geological hazard sources of waste dump slopes under rainfall conditions, a physical model of a rainfall-affected slope was designed. The apparent resistivity of the slope rock and soil mass at different rainfall times was measured via the high-density resistivity method, and the formation process of internal disaster sources of the rainfall-affected slope was obtained. The variation characteristics of the resistivity of the rain-affected slope were analyzed when it had a weak surface and crack development. Based on the three-water model and Maxwell conductivity formula, the evolution process of geological hazard sources of the rainfall-affected slope was summarized. A resistivity response mechanism equation for rainfall-induced slope hazard sources was derived and compared to the Archie formula, verifying the model rationality. The test results showed that the behavior of the rainfall-affected slope conforms to the saturated–unsaturated dynamic cycle process. The apparent resistivity was positively correlated with the development of slope pores and cracks and negatively correlated with the water content in the slope. The apparent resistivity increased during fracture development and decreased during water seepage. In the slope failure and disaster process, the apparent resistivity varies under the coupling effect of crack development and water seepage. During the formation of geological hazard sources, the apparent resistivity abruptly changes and fluctuates. Therefore, according to the abrupt changes and abnormal fluctuations in the apparent resistivity detected, the development of geological hazard sources of slopes can be determined.

Study on Application of Comprehensive Geophysical Prospecting Method in Urban Geological Survey—Taking Concealed Bedrock Detection as an Example in Dingcheng District, Changde City, Hunan Province, China

In order to ascertain the concealed bedrock and its spatial distribution in an urban low-resistance coverage area of a typical lacustrine basin in Hunan Province, a multi-method comprehensive experimental study was carried out in Dingcheng District, Changde City where there are multiple sets of strata and fault structures. In this study, the wide-area electromagnetic method and microtremor survey were utilized on the basis of traditional methods, including the high-density resistivity method and controlled-source audio-frequency magnetotelluric method, to infer the concealed Cambrian limestone, fault structure, and vertical distribution of strata and the results were verified by drilling. The results indicate that the wide-area electromagnetic method is effective to explore the bedrock and concealed structure in urban geological survey. The microtremor method has an obvious effect on the detection of the Cretaceous and Quaternary silty strata within 100 m. The study may provide references for similar projects in this area.

Application of the high-density resistivity method in detecting a mined-out area of a quarry in Xiangtan City, Hunan Province

Goaf ground collapse has great constraints on people’s lives, property safety, and social development within the influence scope because of its concealment and suddenly happening characteristics. The high-density resistivity method is used to explore the goaf of a quarry in Xiangtan City, Hunan Province. The surface subsidence of the goaf is analyzed using the apparent resistivity inversion section diagram and the comprehensive analysis results. The filling water or sediment in the goaf is reflected as a low-resistivity abnormal body, with a resistivity change that is significantly different from the resistivity change of the surrounding bedrock and the contour fluctuation. The morphological characteristics and geological conditions of the underground abnormal body in the goaf are deduced. Based on the geophysical prospecting method, geological disasters such as goaf ground collapse can be explored. From the combined analysis and processing of inversion data, the geological structure and stratum information of goaf can be inferred, which provides a theoretical basis for further disaster prevention.

Evaluation of Compressive Geophysical Prospecting Method for the Identification of the Abandoned Goaf at the Tengzhou Section of China’s Mu Shi Expressway

Subsidence deformation of abandoned goafs can induce cracking, distortion and even collapse of surface buildings (structures), and thus, subsidence deformation poses a great threat. Accurate detection of the abandoned goaf location and overburden morphology is an important prerequisite for stability evaluation and scientific management of surface buildings (structures), and effective detection methods are bottlenecks for accurate detection. Taking the abandoned goaf in the Tengzhou section of China’s Mu Shi expressway as an engineering example, step-by-step detection, traditional detection and combination methods are used to determine the location of the underlying abandoned goaf and overburden morphology. First, we conduct disaster investigation on the expressway and surface within the affected area of the abandoned goaf and initially determine the detection area. Then, according to the principle that the detection range can be examined step-by-step from large to small, the high-density resistivity method is used for detection, and the high-resolution seismic method is further selected to analyze the target area. Then, based on the results of the resistivity method, the position of the abandoned goaf is evaluated with the high-resolution seismic method, and the distributions of the overburden subsidence, the water-filled fractured zone and the caving zone (the three belts) are determined. Finally, boreholes are drilled deep into the bottom of the abandoned goaf at specific locations and the distributions of the abandoned goaf and three belts are verified and corrected with drilling data, acoustic detection and borehole TV imaging technology, thereby providing accurate data on abandoned goafs for highway stability evaluation.

Multi-Step Combined Control Technology for Karst and Fissure Water Inrush Disaster During Shield Tunneling in Spring Areas

Shield tunneling in highly fractured karst water-rich conditions easily results in water inrush disaster or even causes the roof of the karst caves to collapse. Severe water inrush disasters have occurred during the EPB (earth pressure balance) shield machine of the Jinan Metro Line R1 advanced through a karst and fissure groundwater-rich limestone ground in the spring area. To cope with the extreme water inrush risk, a multi-step combined control technology was put forward. First, a detailed geological exploration was carried out by ahead geophysical prospecting using high-density resistivity method, geological radar, etc., and geological borehole drilling was conducted from the ground surface before excavation. As a result, the distribution orientation, size, fissure development degree, and water inflow channel within the surrounding rock of the karst caves were detected. Second, multi-step grouting was performed to reinforce the surrounding rock, including pre-grouting treatment and filling rock blocks to the big karst caves from the ground surface, multiple grouting with a small amount of inert slurry each time inside the tunnel, and secondary circumferential hoop grouting at the shield tail. Third, the tunneling process was optimized, including optimizing the tunneling parameters, making full use of the air-pressurized tunneling technology of the EPB to press bentonite into the fractures around the excavation cabin to seal the fissure water, and using the drainage system of EPB and muck improvement technology to reduce the water inrush disaster. Meanwhile, shield protection slurry technology is applied to cutter inspection and replacement in the pressurized chamber under dynamic water flow environment of the spring terrain. The practice shows that the water inrush on the tunnel face is obviously alleviated after the shield machine advanced into the grouting area. According to statistics, the water inflow on the tunnel face decreases from about 4 m3/h before treatment to less than 0.3 m3/h after the abovementioned control, and the water seepage between the segmental linings reduces to almost zero. The average advance rate increased from 3 m/day without stopping or even zero when the shield machine needs to shut down 2–3 days for drainage to about 6 m/day. In addition, the treatments prevented the shield machine from jamming and the head descending disaster. This study provided a reliable control method for shield tunneling through the karst and fissure water-rich area and played an essential role in protecting the spring water.

Research on intelligent monitoring technology of grouting based on dielectric characteristics

The electromagnetic characteristics of the grouting material can be changed to achieve the electrical difference with the surrounding rock, so as to meet the needs of grouting monitoring. The combination of this principle and the high-density resistivity method can be used to detect whether or not the grout is in the diffusion of an underground space, yet still cannot meet the expected grouting monitoring effect. To monitor the grouting process and detect the grouting effect more clearly, in the present study a theoretical method is proposed, and a high-precision distributed monitoring system based on high-density electrical method technology is independently developed to dynamically monitor the grouting process of non-dispersed materials. The system possesses a stronger ability to identify the resistivity difference of underground materials, and can be used to monitor the entire grouting process through networking technology. The system uploads the collected data to the server in real time through the Internet of Things module, then continuously inverts the uploaded data to obtain the real-time apparent resistivity section diagram. Next, through observation and analysis of the apparent resistivity section diagram and data, it detects the mud diffusion in the underground space. Through the analysis in this study, it is proven that the system can be used for grouting monitoring and that it meets the expected performance requirements.

FDTD numerical simulation and application research of small-loop transient electromagnetic method in shallow water

At present, there are no appropriate exploration methods for the shallow water geophysical surveys with depths less than 100 m. In this paper, the detection feasibility of small-loop transient electromagnetic method (TEM) in shallow water was researched from both theoretical and practical application aspects. Firstly, the propagation characteristics of the multi-turn small-loop electromagnetic field and the magnetic dipole in space were compared. Next, a homogeneous half-space shallow water model and a typical low-resistance abnormal body shallow water model were established by using the finite-difference time-domain (FDTD) method. The research results indicate that the strength of the magnetic field intensity is mainly affected by the depth of water, resistivity, and emission current. The response curve of the low-resistance abnormal body at different times indicates double-peak attenuation law. The response of low-resistance abnormal at different depths of shallow water indicates single-peak, double-peak, and peak-to-valley attenuation laws, and the response of low-resistance abnormal at different resistivity of shallow water indicates single-peak and peak-to-valley attenuation laws. The EA parameters were introduced to analyze the effects of different thicknesses and different resistivity on the response of low-resistance abnormal. Finally, the effectiveness and accuracy of the method were verified when comparing the high-density resistivity method with the results of the transient electromagnetic method on water. The research work provides a theoretical reference for the qualitative analysis of the response characteristics and data processing interpretation of the small-loop transient electromagnetic method in shallow water.

Application of Comprehensive Geophysical Prospecting Method in Water Accumulation Exploration of Multilayer Goaf in Integrated Mine

A coal mine in Datong is an integrated mine. At present, there is goaf in the upper and lower part of the mining coal seam. There is a lot of ponding in the goaf, which has great potential safety hazards for production. In order to find out the scope and location of ponding in goaf, the comprehensive geophysical exploration method combining transient electromagnetic method and high-density resistivity method is used to carry out the research. Firstly, the time-base, turn-off time, receiving delay, current, superposition times, and other parameters of the instrument are tested on the surface of known goaf to obtain the best instrument parameters, and the parameters are used to verify the feasibility of the research scheme; then, the transient electromagnetic method is used for large-area exploration on the surface of the mine, the suspected goaf ponding area is found through comprehensive analysis, and the high-density resistivity exploration is arranged in the suspected goaf ponding area. According to the obtained results, the scope and location of the goaf ponding area are accurately located through comprehensive analysis. The results show that there are two goaf ponding areas in the exploration area, which are located above the 8# coal seam currently mined; the range and location of goaf ponding area can be accurately obtained by using the comprehensive geophysical method of high-density electrical method and transient electromagnetic method. This method can provide reference for mine water prevention and control in Datong area and has great practical significance to ensure coal mine safety production.

Experimental and Numerical Simulation Study of Flow and Solute Transport in Pore-Fractured Media Based on High-Density Resistivity Method

Abstract Pore-fractured media is a ubiquitous phenomenon throughout the world and is a high degree of heterogeneity. The mechanism of water flow and solute transport in the media is still not fully clear. In this study, experiments were conducted in pore-fracture media with various hydraulic gradients to establish the relationship between the hydraulic gradient and specific discharge by using a side guide and to test the resistivity of tracer (sodium chloride) by using a high-density resistivity monitoring system. Quantifying models were, respectively, set up, and results were compared with the traditional methods. Main results are obtained that (1) the phenomenon from Darcian flow to non-Darcian flow was found in pore-fractured media. Both the Forchheimer and Izbash equations can well describe the flow process in the back part of the curve; (2) the phenomenon from non-Fickian to Fickian then to non-Fickian was found in fractured media; (3) good performance of CTRW-TPL has been obtained for both the larger R2 and smaller RMSE values, their counterparts resulting from the ADE model.

Application of high density resistivity method in landslide detection

Landslide geological hazards often occur and are relatively harmful, which seriously threaten the safety of people’s lives and property. Therefore, accurate detection of slope stability is of great interest. Based on the full understanding of the geological conditions of the test area, this paper uses the physical property of the difference in the resistivity of the rock and soil of the landslide mass, and uses the high-density resistivity exploration method to detect the potential sliding surface of the slope in the test area, and finally through inversion. The resistivity profile is calculated, the spatial distribution characteristics of different rock and soil layers in the test site are determined, and the geological interpretation map is formed according to the analysis results, which delineates the potential landslide surface of the slope, and provides an accurate basis for future landslide disaster prevention and control projects.

Research on Comprehensive Exploration Technology of Underground Soil Karst Cave

Underground soi-karst caves are widely developed in China, especially in the southwestern region, and are relatively typical geological structures in limestone areas. It may cause adverse geological disasters such as landslides, ground fissures, ground collapses, mountain collapses, karst leaks, water loss, water inrush and mud out of mine pits, etc., which bring great hidden dangers to the survey and construction of foundation engineering. We analyze the mechanism of bad geological bodies for underground soil-karst caves, discuss the characteristics of several commonly used geophysical prospecting techniques for soil-karst cave exploration, such as high-density resistivity method, five-pole electric sounding method, and geological radar. Through the engineering examples, it is shown that the location and distribution of soil-karst caves can be effectively detected by using the above comprehensive exploration techniques, which take advantage of the differences in the electrical and magnetic properties of soil-karst caves.

FDTD Numerical Simulation and Detection Capability Analysis of Small Loop Transient Electromagnetic Method in Shallow Water

The small loop transient electromagnetic method (TEM) in shallow water has strong adaptability and high resolution and is one of the current research hotspots. In this paper, a shallow-water model of a typical low resistance anomaly is established, which can be obtained through numerical simulation analysis. In the early time, the shallow water layer has large response and the low resistivity abnormal body has small response; In the late time, the shallow water layer has small response induction response and the low resistivity anomaly has larger response, and the response curve shows “double peak” attenuation law; The effects of different thicknesses of shallow water layers on the response of low resistivity abnormal bodies show “single peak”, “double peak”, and “peak wave trough” attenuation laws; However, the effect of different resistivity in shallow water layer on the response of the low resistivity abnormal body only shows the attenuation pattern of “single peak” and “peak wave trough”. Finally, the article takes the highway site selection survey as an example, combined with the high density resistivity method comparison analysis, and verifies the reliability and accuracy of the detection results of the small loop TEM in shallow water. The research work provides a theoretical reference for the qualitative analysis of the response characteristics and data processing interpretation of the small loop TEM in shallow waters.

A new landslide classification method based on electrical differences and relevant examples

A new landslide classification method based on electrical differences is proposed in this paper. The electrical parameters are obtained by the high-density electrical method, which is commonly used in landslide exploration. In this paper, landslides are divided into four categories based on the electrical difference between overburden and bedrock, and on this basis, the landslides are further divided into four categories according to the local electrical difference of landslides, totally eight kinds of landslides. The high-density resistivity method works well for exploration of both type I and type II slides. However, for type III and type IV, other geophysical methods should be supplemented. For type V-VIII landslides, they are simplified into type I-IV landslides in sections according to their electrical characteristics. As for complex landslides caused by multiple factors, more survey lines need to be laid systematically, combined with various methods, as well as information of drilling and trenching for comprehensive prospecting. The landslide classification method proposed in this paper provides some basis and reference for landslide exploration.

Research on slope investigation using high density resistivity method

In this paper, high-density resistivity of the north bank of Huangming Reservoir in Yuyao City was detected by the Wenner device. Through the detection of multiple sections in the longitudinal and transverse sections, the distribution rules of the rock mass of the slope are summarized, and the weathering grade of the rock is judged. The research results will provide a strong basis for the disaster prevention and mitigation work in the later period.

Integrated Treatment Technology of Storage-Mining Inclined Goaf under Expressway

An inclined goaf caused by storage mining is a serious risk to subgrades and pavements. In this paper, effective investigation and detection methods of goafs were discussed considering the project of the Urumqi East Ring Expressway crossing the existing goaf of Zhongxing no. 2 mine. Moreover, by theoretical analysis and a series of field comparative tests, reasonable grouting parameters and the treatment plan were obtained. By comparing the test results of the field and laboratory, the influence of groundwater on the effect of grouting was revealed to reduce the compressive strength of the consolidating objects of the slurry. The high-density resistivity method presented strong anti-interference ability and high accuracy in a depth range of less than 150 m in the investigation of the goaf. The results of the treatment showed that it is necessary to conduct research and analysis from multiple aspects to obtain the best treatment plan of a goaf and ensure the safety of a project.