Application Of Electrical Resistivity Method Research Articles

Application of Electrical Resistivity Method in Building Foundation Study around Ansarudeen Primary School Adehun Area of Ado-Ekiti, Southwestern Nigeria.

The study evaluated the structural competency of the subsurface geological materials around Ansarudeen Primary school in Bolorunduro community, Adehun area of Ado Ekiti, Ekiti State, Nigeria to delineate the area that is suitable for building development. The ABEM SAS 1000 was employed for transmitting current and recording the resistivity value of the subsurface layers across the two traverses using the dipole-dipole and the Schlumberger arrays for horizontal profiling and vertical electrical sounding of the survey area respectively. Five VES points were occupied along traverses 1 and 2 with AB/2 of 150m. The field resistivity data were processed using Win RESIST and the Dipro software to generate the geoelectric sections of the survey area. The sounding curves generated were HK, KHA, and A, with HK having the highest number of occurrences. The interpreted result showed that the geoelectric section consist of five layers which are the topsoil, weathered layer, fractured basement layer, partly fractured layer and the fresh basement rock. The resistivity value and subsurface layer thickness for the top soil varied from 115.3 - 752.7 Ωm and 0.3 - 2.1 m respectively. The general overburden thicknesses were estimated at 11m and 23m respectively for traverse 1 and 2. The pseudo section of the horizontal profiling and the geoelectric section of the Vertical electrical sounding revealed similar subsurface lithology along traverse 1 and 2. The result however suggested foundation placement on traverse 1along VES 3 and VES 2 of the geoelectric section or point 16-19 of the horizontal profiling pseudo section.

A geophysical assessment for engineering performance of subgrade soils: a case study of the Ago-Iwoye/Ilishan road, South-Western Nigeria

Geophysical application of electrical resistivity method has been employed to differentiate subsurface target of interest from the encompassing strata along the Ago-Iwoye/Ilishan road in South-western Nigeria. However, a geological model which links variation in lithological characteristics of subgrade soils to the engineering performance of the road is yet to be a research subject. This research is a special geotechnical application of geophysics for revealing the subsurface disposition and predicting the stability state of subgrade materials. Field assessment of rock types, and their relationship was followed by electrical resistivity measurement along the road. Schlumberger and dipole – dipole arrays were adopted for fifty-eight (58) Vertical Electrical Sounding (VES) and 2-D resistivity imaging involving Dipole-Dipole profiling technique was adopted in the sedimentary segment. Field data were inverted to 2-D resistivity structures inferentially delineated contour colorations using ‘DIPRO for Windows’ software. Geo-electric layers revealed Sedimentary Basin (SB) between Ilishan and Irolu, between Irolu and Ijesha-Ijebu, Transitional Zone (TR) with abrupt contrast along the plane of an unconformity and crystalline Basement Complex (BC) towards Ago-Iwoye. The 2-D resistivity structures across the different geological terrains revealed with 50Ωm - 3289Ωm at SB,233Ωm - 8028Ωm at TZ and 8Ωm - 3009Ωm at BC. From geotechnical view, subgrade materials underlying the SB and TZ segments can be adjudged competent to sand and clayey sand units with minor occurrences of incompetent clay and sandy clay lenses. The occurrence of subsurface discontinuities at the BC end of TZof the road would adversely affect the pavement stability.

Application of Electrical Resistivity Method to Decipher Groundwater Occurrence Status at Isikuku, Southern Nigeria

Electrical resistivity method is a type of geophysical survey employed for groundwater investigation, conducted in Isikuku Community in Benin City, Edo state with the aim of delineating groundwater occurrence. Schlumberger electrode array configuration was employed in this study. Six (6) VES points were surveyed with linearised inversion technique used for the interpretation of sounding taken at various locations in the area. The data collected were interpreted by curved matching and computer iteration using Interpex Ix1D v 2 software. From the geoelectric section, VES 1 possess the AK curve with four layers ρ1˂ρ2˂ρ3˃ρ4, VES 2 possess the KQ curve with four layers ρ1˂ρ2˃ρ3˃ρ4, VES 3 possess the A curve with three layers ρ1˂ρ2˂ρ3, VES 4 possess the AK curve with four layers ρ1˂ρ2˂ρ3˃ρ4, VES 5 possess the A curve with three layers ρ1˂ρ2˂ρ3, VES 6 possess the K curve with three layers ρ1˂ρ2˃ρ3. Geo-electrical layers identified in the study area included topsoil, sandy clay, clay basement and sandstone. The VES study revealed the layer which constitute the productive water-bearing zones referred to as good groundwater potential aquifers. The analysis of the interpretation of the field data showed that the area under investigation delineated four layers earth in each of the vertical electrical sounding point. Generally, the geoelectric survey conducted in the study area revealed the subsurface lithologies: Clay, Clayey Sandstone, Sand stone, Coarse Sand, Lateritic soil and Top soil. Thus, vertical electrical sounding techniques employed in this study has proved useful and successful in delineating subsurface lithology in the study area.

Application of Electrical Resistivity Method to Site Characterisation for Construction Purposes at Institute of Agriculture Research and Training Moor Plantation Ibadan

This research was carried out within Institute of Agriculture Research and Training Moor Plantation Ibadan, Southwestern Nigeria, with the aim to ascertain suitability of the proposed site for building construction and usage. The geophysical investigation involved three electrical resistivity techniques; Vertical Electrical Sounding (VES) using the Schlumberger configuration, 2D ERT and 2-D electrical imaging using Dipole-dipole electrode configuration. Two traverses were established E–W direction cutting across geologic strike with a distance of 80 m and of varying inter-traverse spacing. Eight (8) VES stations were occupied covering the entire study area for layer stratification and geoelectric parameters. The results were qualitatively and quantitatively interpreted and are presented as sounding curves and geoelectric sections. The 2-D imaging gave information on the subsurface characteristic in the area with generally low apparent resistivity indicating low competence material. The results obtained from the VES delineate three geoelectric units which comprise of the topsoil, weathered layer and fresh basement. The results from the VES were used to determine the second order parameters. The entire results correlate well with one another showing that all the techniques used were complemented. This study has further justified the need for geophysical site investigation as pre-condition before any construction to avoid problems of differential settlement. In determining of foundation material, topography elevation, clay content and the depth of weak zones should be put into consideration, since the depth of the weak zone is appreciably high.

Identification of Water Conservation Zone By Application Of Electrical Resistivity Method In Parts of Osmanabad District, Maharashtra-India

Identification of Water Conservation Zone By Application Of Electrical Resistivity Method In Parts of Osmanabad District, Maharashtra-India

Application of geophysical methods to evaluate soil dynamic properties in Penang Island, Malaysia

Abstract The essential criterion of selecting the site for building foundations is the underlying soil. This vital requirement stems from the associated potential for disaster should the ground condition be unstable. Conventionally, the method of geotechnical drilling is used in soil investigation work. However, this method is limited to providing subsurface information only at one particular point. This research aims to utilise geophysical methods to investigate the soil dynamic properties of various lithology types via application of electrical resistivity method (ERM), seismic refraction (SR), and multichannel analysis of surface wave (MASW) methods. The soil dynamic properties (bulk density, Poisson’s ratio, Young’s modulus, shear modulus, bulk modulus) and material bearing capacity (subgrade reaction coefficient, ultimate and allowable bearing capacity) were computed using a relative formula by using compressional wave (VP) and shear wave velocities (VS). The calculated values of soil dynamic properties and material bearing capacity for the three study areas are capable in determining the competency and stiffness of subsurface layers for building foundation. The results leading to this conclusion can be verified by the values of standard penetration test value (SPT-N) from borehole record. From this study, it is apparent that the soil dynamic properties and material bearing capacity values are essential to determine the competency of soil, in turn aiding in determining the area suitable for the shallow foundation to rest. Thus, geophysical methods are time- and cost-saving, as well as non-intrusive, recommended for site investigation before starting any construction work.

Application of Electrical Resistivity Method in Groundwater Exploration

Vertical Electrical Sounding (VES) was carried out in Alode Community of Eleme Local Government Area in Rivers State, Nigeria to determine the geo-electrical and hydrogeological characteristics of aquifers present in the area, also to delineate the geo-electric stratigraphy of each VES station. A total of three (3) VES were carried out with the ABEM Terrameter SAS 300C, using the Schlumberger Configuration. Maximum half-current electrode spread (AB/2) of 1m up to 150m was used, while the half potential electrode separation (MN/2) was maintained between 0.5m and 7.5m. The VES curves were quantitatively interpreted by partial curve matching and computer iteration techniques, using the IP1 WIN computer software. The results of the interpreted VES data confirm the following stratigraphies: top soil (40.2-65.2Ωm), shale (32.2-86.3Ωm), fine-medium sand (172-204Ωm), medium-coarse sand (532Ωm), and medium sand (417Ωm). Geo-electric sections reveal that the aquiferous units are mostly confined, with depth to aquifer range of 60m (154.2ft) for VES 1 and 63m (206.7ft) for VES 2 and 65m (213.3ft) for VES 3.

Delineation of contaminated aquifers using integrated geophysical methods in Northeast Punjab, Pakistan.

A decline in surface water sources in Pakistan is continuously causing the over-extraction of groundwater resources which is in turn costing the saltwater intrusion in many areas of the country. The saltwater intrusion is a major problem in sustainable groundwater development. The application of electrical resistivity methods is one of the best known geophysical approaches in groundwater study. Considering the accuracy in extraction of freshwater resources, the use of resistivity methods is highly successful to delineate the fresh-saline aquifer boundary. An integrated geophysical study of VES and ERI methods was carried out through the analysis and interpretation of resistivity data using Schlumberger array. The main purpose of this investigation was to delineate the fresh/saline aquifer zones for exploitation and management of fresh water resources in the Upper Bari Doab, northeast Punjab, Pakistan. The results suggest that sudden drop in resistivity values caused by the solute salts indicates the saline aquifer, whereas high resistivity values above a specific range reveal the fresh water. However, the overlapping of fresh/saline aquifers caused by the formation resistivity was delineated through confident solutions of the D-Z parameters computed from the VES data. A four-layered unified model of the subsurface geologic formation was constrained by the calibration between formation resistivity and borehole lithologs. i.e., sand and gravel-sand containing fresh water, clay-sand with brackish water, and clay having saline water. The aquifer yield contained within the fresh/saline aquifers was measured by the hydraulic parameters. The fresh-saline interface demarcated by the resistivity methods was confirmed by the geochemical method and the local hydrogeological data. The proposed geophysical approach can delineate the fresh-saline boundary with 90% confidence in any homogeneous or heterogeneous aquifer system.

Application of electrical resistivity method in the characterization of 2D desiccation cracking process of clayey soil

Electrical resistivity method (ERM) is an attractive approach in the assessment of soil physical properties (water content, void ratio, density, etc.), which are closely related to electrical resistivity distribution. ERM performance in the detecting and mapping of cracks initiation, propagation, and coalescence processes in the 2D/3D scale needs to be studied to provide the technical support for its field application. An evaporation test of a clayey soil specimen with an integrated experimental configuration is performed to analyze the performance of ERM in the characterization of the 2D desiccation cracking process. The evolutions of ambient temperature, relative humidity, average water content, crack morphology, and apparent electrical resistivity of the studied sample are well captured during continuous drying. Image processing allows the quantitative geometrical description of the crack pattern formation. The consistency between the start-to-increase point of measured electrical resistivity, electrical resistivity anomalies, and the cracks propagations presents the good performance of ERM in crack characterization and reveals its potential to map the cracks before possible visualization. A better understanding of the fundamental mechanisms of desiccation cracking is also obtained based on the experiment results. This study provides an insight to apply ERM for engineering purposes involving crack monitoring and early crack detection.

Exploration for Marble Deposit in Parts of Okpella, South-Southern Nigeria

The ultimate aim of the electrical resistivity survey is to determine the resistivity distribution with depth on the basis of surface measurements of the apparent resistivity and to interpret it in terms of geology. Marble deposit was investigated with the application of electrical resistivity method using Vertical Electrical Sounding (VES) technique with the aim of characterising this deposit in parts of Okpella. Six (6) VES were acquired using the Schlumberger array for data acquisition with current electrode spacing varying from 1.0 to 150.0 m. The VES data obtained were interpreted using ipi2win Software. The results showed three layers indicating subsurface geologic sequence probed 26.4 m and beyond with clay/clayey sand (23.3 – 219.1 Ωm), sand (423 - 2040 Ωm) and marble (12661 - 404498 Ωm). The occurrence of marble deposit was revealed at VES points at 1, 2 and 5 in the studied area. This study concluded that the study area had occurrence of the marble deposits, which would be of economic importance, if exploited.

Application of Electrical Resistivity Method in Mapping Underground River Channels: A Case Study of Kabatini Area in the Kenyan Rift Valley

Kabatini area is in Nakuru County which occurs in Kenya within the great Gregory rift valley. The area is bounded by longitudes 180900-181200 and latitudes 9971050-9971200 in UTM. This research aimed to investigate the possible occurrence of subsurface faults recharging Kabatini aquifer which is the primary source of groundwater for the residents of Nakuru town and its environs. Vertical electrical sounding and geological mapping methods were used to unravel this problem of subsurface fault occurrence in the area of study. Vertical Electrical Sounding data collected were analyzed using the computer-based inversion using EarthImager software, which allows the performance of automatic interpretation of the Schlumberger sounding curves to obtain the equivalent n-layer model from the apparent resistivity curve of each sounding. This procedure was used for all the sounding points collected in the study area, to obtain the equivalent apparent resistivity models of each sounding, their depths as well as thicknesses. The results indicate the occurrence of subsurface faults trending in the north-south direction which is proven by K-H-K, K-H-H, Q-H-A, Q-H-Q. Depth iso-resistivity analysis shows that the fault plane is deeper than 165 meters below the surface.

Application of Electrical Resistivity Method in Site Characterization along Ado – Afao Road, Southwestern Nigeria

A geophysical study was carried out at a proposed location for the construction of a structure along Ado-Afao road, Southwestern Nigeria. The aim of the study is to evaluate the electrical properties of the soil for Founding of Engineering structures. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration with a total of twenty-one (21) VES within the investigated area. The electrode separation varies from 1 to 100 m. The geoelectric sections identified three to five geoelectric/geologic subsurface layers along the traverses. The topsoil comprising of clay, clayey sand and sandy clay with the resistivity values range from 28 to 800 Ω-m with its thickness varying from 0.4 to 1.9 m. The second layer was found to be lateritic with resistivity ranging between 200 to 800 Ω-m and thickness ranges from 1 to 7.5 m while the weathered layer comprising of clay, clayey sand and sandy clay with resistivity varies from 30 to 220 Ω-m and its thickness varies from 1.2 to 54 m. The fractured basement with resistivity value of 763 Ωm and thickness value of 8m while the fresh basement has a resistivity value ranging from 365 to 2964 Ωm with depth to basement ranging from 8 to 58 m. The resistivity values of the topsoil are indicative of clay, sandy clay and clayey sand. This layer may not be of any special interest since topsoil is normally excavated. Hence, foundation of the proposed structures cannot be found on this layer. Based on the investigation, the subsurface of the study area can be generally classified as incompetent. There is a presence of lateral inhomogeneity of the subsurface layers and geologic features such as fractures and faults. The construction in the area should be founded on the lateritic layer or fresh basement layer coupled with pile foundation to ensure the stability of the building. The choice of foundation material, clay content and topography elevation should be put into consideration.

Application of electrical resistivity method in estimating geohydraulic properties of a sandy hydrolithofacies: a case study of Ajali Sandstone in Ninth Mile, Enugu State, Nigeria

Geoelectric investigation using vertical electrical sounding (VES) (Schlumberger electrode configuration) was carried out in 14 locations at Ninth Mile area, southeastern Nigeria to determine the variations and interrelationship of some geoelectric and geohydraulic parameters of a sandstone hydrolithofacies. The measured resistivity data were interpreted using manual and computer software packages, which gave the resistivity, depth, and thickness for each layer within the maximum current electrodes separation. The aquifer resistivity values range from 86.56 to 4753.0 Ωm with 1669.40 Ωm average value. The values of water resistivity from borehole locations close to the sounding points range from 79.49 to 454 .55 Ωm and averaging about 264.7 Ωm. Porosity values of the sandy aquifer range from 30.19 to 34.20%. Fractional porosity values range from 0.3019 to 0.3292, while the tortuosity values vary between 2.91 and 22.85. The geohydraulic parameters estimated vary across the study area. Formation factor ranges from 0.28 to 15.29, hydraulic conductivity ranges from 1.21 to 66.54 m/day which, however, influences the natural flow of water in the aquifer while tortuosity values range from 2.91 to 23.27. The contour maps clearly show the variation of these parameters in the subsurface and the plots show their relationship and high correlation coefficients with one another. The results of this study have revealed the geological characteristics of the subsurface aquifer, established the influence on the amount of groundwater, and proposed a strategy for the management and exploitation of groundwater resources in the area and other aquiferous formations.

Application of Electrical Resistivity Method (ERM) in Groundwater Exploration

The geophysical method which dominant by geophysicists become one of most popular method applied by engineers in civil engineering fields. Electrical Resistivity Method (ERM) is one of geophysical tool that offer very attractive technique for subsurface profile characterization in larger area. Applicable alternative technique in groundwater exploration such as ERM which complement with existing conventional method may produce comprehensive and convincing output thus effective in terms of cost, time, data coverage and sustainable. ERM has been applied by various application in groundwater exploration. Over the years, conventional method such as excavation and test boring are the tools used to obtain information of earth layer especially during site investigation. There are several problems regarding the application of conventional technique as it only provides information at actual drilling point only. This review paper was carried out to expose the application of ERM in groundwater exploration. Results from ERM could be additional information to respective expert for their problem solving such as the information on groundwater pollution, leachate, underground and source of water supply.

Evaluation of Unknown Tube Well Depth Using Electrical Resistivity Method

Electrical resistivity method has increasingly adopted in engineering, environmental, mining and archaeological studies. Systematic and proper studies of unknown civil engineering structure evaluation particularly on tube well depth was rarely being established. Conventionally, camera test or string with weight approach has been used to evaluate unknown tube well depth thus exposed to several restriction due to its expensive and time consuming. Hence, this study focused on evaluation of unknown tube well depth using indirect test with particular reference to electrical resistivity method (ERM).A single spread line of electrical resistivity survey was performed using ABEM SAS 4000 equipment set based on Wenner and Pole-dipole array in line with the tube well position. Electrical resistivity raw data was processed using RES2DINV software producing electrical resistivity tomography (ERT) of the subsurface profile studied. Then, electrical resistivity value (ERV) obtained from RES2DINV analyses (ERT) was extracted and analysed using plotted graph (depth versus ERV) specifically at tube well position based on electrical resistivity spread line performed. It was found that both array have shown some good similarity results in term of tube well depth (20 m) thus able to verify the result interpreted. Both array have shown some good similarity of ERV representing groundwater (ERV = 10 – 100 Ωm) and soil with water (ERV > 100 Ωm) at depth of 0 – 20 m and >20 m respectively. All those interpretation have shown good agreement based on verification thru established ERV of earth materials references, geological map and nearest available boreholes data. Hence, this study has shown that the application of ERM was applicable in evaluation of unknown tube well depth which efficient in term of cost, time and environmental sustainable.

Application of electrical resistivity method for groundwater exploration at the Moghra area, Western Desert, Egypt

Moghra territory is one of the most encouraging regions for watered farming and development in the northern part of Western Desert. To achieve that development groundwater is considered the most favorable tool. Geophysical survey in terms of geoelectrical resistivity sounding has been conducted using the Schlumberger array – eleven vertical electrical soundings (VES’s) were measured on the study area. The aim of this study was to investigate the hydrogeological condition at the area under investigation.Three geoelectric sections are prepared; each of them is composed of four units. The first layer has resistivity ranging from 58 to 2029ohm.m and thicknesses from 0.46 to 10.7m characterizing a gravely sand facies of Quaternary age (Pleistocene to Holocene). The second geoelectrical layer has resistivity values ranging between 188 and 518ohm.m which are comparatively high, with various depths varying between 14.7 and 25.8m from Lower Miocene age. It is formed of sand and gravel. The third geoelectrical layer is considered the aquifer for the area under investigation with moderate electrical resistivity values (17–111ohm.m), and could be recognized sometimes as the most extreme depth of penetration. At the maximum depth of penetration of this area, the lower layer (fourth layer) was recognized with the highest electrical resistivity values (1227–8935ohm.m) of basaltic sheet (Precambrian age).Structurally, the study area is influenced by three faults two of them are geological/geoelectrical faults forming a graben structure at the central part; the third fault is a geoelectrical fault and is located to the west of the graben structure forming a horest structure.

Geoelectric assessment as an aid to geotechnical investigation at a proposed residential development site in Ilubirin, Lagos, Southwestern Nigeria

The study focuses on the application of electrical resistivity methods as a guide for a detailed geotechnical investigation due to the inhomogeneity of the soil materials cum inability of the drilling beyond 38 m from the three initially drilled geotechnical boreholes which did not allow for proper foundation decisions and thus necessitated the research. Two-dimensional (2D) electrical resistivity data were acquired using the Wenner array along ten (10) traverses of about 500 m long, and forty-four (44) vertical electrical sounding (VES) data were acquired along the various traverses using the Schlumberger array with a maximum spread of 620 m. The VES data were interpreted using partial curve matching technique and one-dimensional (1D) computer iteration using WinRESIST software. The 2D dataset were processed using DIPROWin software. The inversion of the 2D resistivity data was constraint by the VES results and available borehole data. The results of the interpretation of the electrical resistivity data reveal that the lithological units underlying the study area compose of clay/peat, clayey sand, sandy clay, and sand. The results of the interpretation of the electrical resistivity data guided by the range of resistivity (ρ) values and knowledge of the geology of the area reveal that the lithological units underlying the study area are composed of peat (ρ ρ ρ ρ 300 Ωm). The various layers are intercalated with each other, and thickness values vary from one location to another up to a maximum depth of 70 m. The VES results show that the clayey material underlies the sand-filled topsoil and there are indications of competent sand layers at depth beneath these clayey layers in the study area. The 2D pseudosections reflect that the different lithological units are intercalated with varying thicknesses across the study area. Thus, the study reveals that the subsoil within the study area is quite inhomogeneous and great care and expertise is required for developing the site. Anonymously low-resistivity areas delineated along each of the traverses are locations recommended for targeted geotechnical investigation prior to construction.

Groundwater Seepage Mapping Using Electrical Resistivity Imaging

In recent years, electrical resistivity method (ERM) has widely being applied as an alternative tool in engineering, environmental and archeological studies. A global image of groundwater seepage problem was difficult to obtained using conventional geotechnical method due to the efficiency of cost, time and result coverage. This study was conducted using electrical resistivity survey in order to investigate the potential of the problematic zone due to the groundwater seepage problem. ABEM SAS 4000 equipment set was used in during the resistivity data acquisition stage. Six (6) resistivity spread lines (SP) were performed across the slopes area using 2-D electrical resistivity imaging. The raw data was processed using RES2DINV and SURFER software for 2-D and 3-D subsurface image. Interpretation of electrical resistivity results was verified using the existing borehole and geochemistry results. Geochemistry results analyses were used Atomic Absorption Spectrometer (AAS) for determining cation and Ion Chromatography (IC) is for anions. Anion elements were studied consists of chloride, bicarbonate, nitrate and sulfate while cation elements consists of sodium, potassium, calcium and magnesium. All the elements were analyzed by using Piper Diagram to determine geochemistry facies in the groundwater. It was found that low resistivity value (ERV) which associated to groundwater (10 ~ 100 Ωm) can be found starts from the ground surface (0 m) to a greater (> 10 m) depth of the subsurface profile. The finding of the study water seepage can be categorized as Ca-HCO that indicator a typical of shallow fresh groundwater. The finding of the study is important to determine source process of water seepage on that area. This study has successfully demonstrates that the application of ERM with supporting borehole and geochemistry data was able to provide a comprehensive results due to the groundwater leakage detection.

Application of Electrical Resistivity Method in Detecting Self-Buried Archaeological Materials

Wenner configuration of electrical resistivity was used to examine self-buried archaeological materials. This configuration was employed because of its sensitivity to vertical changes in the subsurface resistivity below the centre of array.  This method was used to check for the accuracy/ resolution ability of Electrical resistivity in detecting archaeological materials. Five (5) pits were filled up with different materials. Measurements were done at different electrode spacing’s (a). The electrode spacing varied from 5 m up to 25 m in order to cover the formations embedded beneath the survey line at different depths in a comprehensive way. Three profiles of about 120m were made to cut across the five (5) pits that contained the self-buried archaeological materials. Campus Omega Terrameter was used to acquire the resistance data along each profile. Apparent resistivity was obtained by multiplying the geometric factor with the resistance data acquired. The acquired data was interpreted by using Res2D inversion to obtain the Electrical resistivity tomography (ERT).  From the ERT obtained, the buried materials were detected with varying resistivity values in accordance with their points on the profile.

Application of Electrical Resistivity Method to Evaluate the Extent of Mortar Infiltration in Subsurface Cavities

Karst problems often result in unexpected additional building costs and the proper understanding of karst terrains is therefore important for geotechnical engineer. The karst terrain is developed from the dissolution of carbonate rock. Groundwater flow through carbonate rock enhances the dissolution of carbonate minerals which can cause the development of subsurface cavities or voids. The subsurface cavities and uneven depth of bedrock make foundation design very difficult in karst terrain. A subsurface characterization and grouting case study are presented for the Yongweol-ri site, South Korea. In the project area, mortar was injected into subsurface cavities for consolidation and/or grouting purposes. The subsurface cavities were imaged using electrical resistivity and borehole camera (BHTV) before and after mortar injection. In addition, the resistivity changes of mortar specimens were studied in the laboratory simulating various field conditions. The injected mortar was imaged as anomalies exhibiting lower resistivity than the surrounding rocks. A comparison of the pre- and post-grouting resistivity provided detailed information of the subsurface cavities plus the areas which have been occupied by the mortar after consolidation. Also, BHTV field test confirmed the presence of the mortar in the subsurface cavities. The results obtained from this study showed that electrical resistivity imaging can be a useful tool for detecting and evaluating changes in subsurface resistivity due to the injection of the mortar. From the laboratory analysis, it is confirmed that mortar is a good material for grouting and ground stability hazard management.