Grounding Electrodes with Internal Resistance: Application to Feasibility Study of the Driven-Rod Method for Modeling the Soil Electrical Resistivity Profile

The paper presents a model to include the internal resistance of the grounding electrodes in the calculation of its electrical features. The semi-analytical expressions for the calculation of the grounding resistance arising from the model are used to study the feasibility of the driven-rod method for the estimation of the soil resistivity profile since, unlike other methods, the internal resistance of the conductors can be of great influence for a correct estimate. From the grounding resistance profile an inverse problem based on the minimization of the quadratic differences between the resistance measured and that calculated from the model is posed. Several synthetic examples are used to assess the limitations of the method in conditions close to real situations. Finally, some real cases involving data measured in the field are analyzed. Whether in synthetic examples or in real soils it is found that the spatial frequency of the driven-rod resistance sampling is a determinant factor in order to study the feasibility of the driven–rod method.

FEATURES OF JOINT INVERSION OF NON-SIMULTANEOUS SIGNALS OF THE RUSSIAN LATERAL SOUNDING AND ELECTROMAGNETIC LOGGING IN CRETACEOUS RESERVOIRS

The article presents the results of the study of the effect of the non-simultaneous measurement of electrical and electromagnetic logging signals on the determination of the parameters of the geoelectric model by joint numerical inversion. The radial profile of the electrical resistivity is calculated for different times after drilling in the program for modeling the process of mud invasion into a porous permeable formation with parameters characteristic of the BS cretaceous reservoir. For this continuous resistivity profile electric log signals are calculated for the reservoir of unlimited thickness.

Appraisal of the Spatial Resolution of 2D Electrical Resistivity Tomography for Geotechnical Investigation

In the past decade, the 2D electrical resistivity tomography (ERT) has been extensively used in the investigation and monitoring of geotechnical engineering and environment engineering, but there are many uncertainties hidden behind its vivid color earth-resistivity profiles. In order to use the 2D ERT in the scale of geotechnical engineering effectively, the accuracy and spatial resolution capability of measurements must be enhanced, or at least these uncertainties should be mastered to avoid overreading the measurement results. There were seven common geological models built in this study to discuss the variance in spatial analysis capability of 2D electrical resistivity profiles under different geologic conditions. The findings show that the resolution capability of 2D electrical resistivity profiles was influenced by depth, and in different strata, it may be influenced by the resistivity ratio, layer depth, covering depth, interlayer thickness, tilt angle, medium size, and noise intensity. Generally speaking, the relatively low resistance stratum had better resolution capability; if the relatively high resistance stratum was located under the relatively low resistance stratum, its resolution capability declined. In different strata, the resolution capability may be degraded under the effect of different factors. In addition, any noise in the course of measurement resulted in a random jump of the electrical resistivity profile, which worsened as the noise increased. These circumstances should be paid special attention to avoid misrecognition of electrical resistivity profile images.

Application of electromagnetic and electrical resistivity methods for foundation studies at Ahmadu Bello University Phase II, Zaria

Very Low-Frequency Electromagnetic (VLF-EM) and 2D electrical resistivity survey were carried out at the Ahmadu Bello University Phase II in order to investigate the suitability of the soil materials for the foundation of super-structures in the study area. The Terra-Plus equipment and ABEM SAS 4000 were used for VLF-EM and resistivity data acquisition respectively. The VLF-EM Data were collected along five (5) profiles at station interval of 10 m along each profile. The data collected from each of the VLF-EM profile were processed and interpreted with the aid of Karous-Hjelt and Fraser filter software. Electrical resistivity profile was laid on the weak zones revealed by the 2D VLF-EM profiles through the aid of dipole-dipole configuration. The data obtained were processed and interpreted with the aid of Res2Dinv software. Borehole log of the study area was used as additional information which serves as a calibration tool. The 2D imaging profile of VLF-EM highly correlates with resistivity profile. The 2D VLF-EM and resistivity profiles revealed the conductive zone and resistive zones. These zones are suspected to be geological features (dyke, faults and fractures). This geological feature such as fracture zones was filled with an earth’s materials which are probably sandy clay and mottled clay, and these materials are highly undesirable for the foundation of building structures due to its characteristics of swelling and contracting during rainy and dry season respectively. Thus, undesirable materials should be excavated and be refilled with suitable materials for the foundation of super-structures and also, geological bodies should be avoided when the foundation of the structures is to be erected. Keyword: VLF-EM, electrical resistivity, foundation of super-structures, geological feature, undesirable materials

PENYELIDIKAN LETAK AKUMULASI LINDI DAN ARAH REMBESAN DENGAN MENGGUNAKAN KONFIGURASI WENNER-SCHLUMBERGER DI TPAS AMPANG KUALO KOTA SOLOK

TPAS Ampang Kualo is a final waste dumping area in Kota Solok of Sumatera Barat. The research at TPAS Ampang Kualo aims to know the distribution of leachate. Geolistrik resistivity method by Wenner - Schlumberger configuration is used for data retrieval Resistivity meter MAE X612 EM. The measurement data is then converted by using Res2dinv software to generate 2D resistivity profile and Voxler 4.0 software for 3D resistivity profile. The results show that leachate seepage at TPAS Ampang Kualo on track one was around a leachate pond stretching from South to North. The leachate was detected at depths between of 2.10 to 5.80 meters. In track two, the presence of leachate was indicated around a leachate pond stretching from east to west. It was detected at depths beetween of 1.50 to 6.35 meters. The trajectory three was taken around the residential population stretching from South to North that cuts out the flow of the leachate ditch. The leachate was detected at a depth of 0.25 to 7.38 meters. It was concluded that the distribution of TPAS Ampang Kualo leachate spread from the South to the Southwest was down in a small ditch flow for leachate disposal that ending at Green Hills Arya Residen. Keywords: TPAS Ampang Kualo, Leachate, Geolistrik Resistivity Method, Wenner-Schlumberger Configuration

A LOW-COST RESISTIVIMETER FOR USE IN PRACTICAL LECTURES OF APPLIED GEOPHYSICS

ABSTRACT. We describe the construction and testing of a simple and efficient low-cost resistivimeter designed for use in practical classes in Applied Geophysics. The equipment was successfully tested in a vertical electrical sounding (VES) performed on sandy terrain within the campus of the Universidade Federal de Sergipe, Brazil. The VES results were in good agreement with the profiles obtained from two boreholes located approximately 500 m from the test area, clearly demonstrating the efficiency of the equipment and the adopted methodology.Keywords: vertical electrical sounding, electrical resistivity, resistivity profile. RESUMO. Neste artigo, descrevemos a construção e o teste de um resistivímetro de baixo custo, simples e eficiente, concebido para ser utilizado em aulas práticas de Geofísica Aplicada. O equipamento foi testado com a realização de uma sondagem elétrica vertical (SEV) em um terreno arenoso localizado no campus da Universidade Federal de Sergipe, Brasil. Os resultados obtidos nesta SEV apresentaram boa concordância com os perfis observados em dois poços de sondagem localizados a 500 m da área de teste, fato que comprovou a eficiência do equipamento e da metodologia adotada.Palavras-chave: sondagem elétrica vertical, resistividade elétrica, perfil de resistividade.

GROUND INVESTIGATION USING 2D RESISTIVITY IMAGING FOR ROAD CONSTRUCTION

This paper présents finding on the ground exploration using 2D resistivity imaging. The study was conducted to verify the borehole result, which shows a conflict between the actual site conditions. The proposed study is to investigate of high topography area for road construction. Electrical resistivity imaging method was used for estimating bedrock at Bandar Sri Sendayan, Negeri Sembilan. The site consist of acid intrusive igneous, which is dominantly covered by granite. Two lines of resistivity survey were conducted to identify ground material of this area. The survey was conducted using ABEM Terrameter equipment, where a two-dimensional resistivity profile has been identified for ground exploration and subsurface profiling. The resistivity images showed the existence of boulders and bedrock in multiple weathering grades with resistivity values ranges from 50 to 10 000 ohm-m along the proposed road alignment. The presence of these boulders and weathered bedrock probably not suitable to be used as domestic supply for road material such as crushed aggregate especially at depth less than 30m from surface. Soil or overburden was discovered 12m from the surface. The finding shows the mismatched between the borehole result and resistivity profile, where the borehole data was interpreted as bedrock however the resistivity result proved that it is a boulder.