Variation Of Soil Resistivity Research Articles

Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain: A Geophysical Method Application in Agricultural Practice

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were done across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One samples each at first and second layer. Result of the resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth good for soil minerals occurrence for optimum agricultural output, soil texture affect soil fertility and geological terrain is responsible for resistivity signature inconsistency with soil fertility.

Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain, Igieduma-Edo State, Nigeria: A Geophysical Method Application in Agricultural Practice

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were conducted across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One sample each at first and second layer. Result of the apparent resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth conducive for soil minerals occurrence for optimum agricultural output.

Three-dimensional migration and resistivity characteristics of crude oil in heterogeneous soil layers

An experimentally induced three-dimensional petroleum seepage flume was used to investigate its migration in heterogeneous soil layers and a method for monitoring resistivity was adopted, under conditions of fluctuating water levels and rainfall. The corresponding mechanisms were then analyzed based on the resistivity characteristics and combined with three-dimensional inversion images. Finally, physical and chemical property analysis was conducted to verify the results of resistivity monitoring. The results demonstrated that: (1) In the process of natural oil leakage, the variation of soil resistivity presents a concave shape in the resistivity profile. Thus, oil migration exhibited the following patterns. At first, circular migration front was dominant in a vertical direction. Subsequently, after vertical migration was impeded, lateral migration was dominant. As the crude oil gradually accumulated, the migration front broke through the limitation of lithologic interface and continued vertically. (2) By comparing the two resistivity monitoring methods, namely the Wenner and Pole-pole methods, it was demonstrated that the inversion resistivity measured by Wenner method was closer to the true resistivity, and the resistivity variations were more distinguishable. (3) The resistivity inversion profile demonstrated that the low resistivity anomaly of the crude oil leakage area was related to the low water content of the soil layer in the test area. (4) Fluctuations in water level increased the diffusion range of crude oil beyond the original pollution source area, especially horizontally. (5) Percolation of rainfall caused the water level to rise, and the crude oil was evenly distributed in the soil layers above the capillary zone. (6) Through sample analysis and verification, it was demonstrated that the resistivity method can accurately and intuitively present the characteristics of crude oil migration. These results provide theoretical support for the rapid determination of the migration range and characteristics of crude oil in heterogeneous soil layers.

Impact of Frequency-Dependent Soil Models on Grounding System Performance for Direct and Indirect Lightning Strikes

The goal of this article is to investigate the effect of frequency-dependent soil models on the performance of grounding electrodes subjected to lightning strikes. Several soil models are examined while accounting for the variation of soil resistivity and permittivity as a function of the lightning current frequency spectrum. The analysis is performed for a homogeneous soil and a two-layer horizontally stratified soil. The impact of the frequency-dependent soil parameters on the ground potential rise (GPR) of simple grounding electrodes subjected to lightning is analyzed and discussed. The analysis is performed in the frequency domain and in the time domain. A wind turbine and its grounding system are also considered in this article. Special attention is given to the case of indirect lightning, rarely mentioned in the literature. The GPR of the grounding electrodes is examined when the frequency dependence of the soil is taken into account and the lightning channel is located at close distances to the electrodes. Indeed, the level of induced electromagnetic fields caused by a nearby lightning channel can still be too high and potentially dangerous. The computations are performed using an efficient Method of Moments (MoM) numerical tool based on surface-wire integral equations for a stratified medium in the frequency range from dc to several MHz. Numerical results demonstrate that the frequency dependency of the soil parameters results in a decrease of the potential rise of the grounding electrodes, with respect to the case where the parameters are assumed constant.

Evaluation of Transient Response of Different Earthing Configurations due to Lightning Impulses

Earthing system is very important in order to protect the electrical equipment as well as the human’s safety against over voltages. The main function of the earthling system is to remove unwanted excessive electrical currents caused by unusual conditions such as fault and lightning or switching over voltages by providing a low resistance path to the earth. Researchers had studied the behaviour of the earthling system to improve its performance for the past few years. There are few factors that influence the performance of the earthling system such as soil resistivity and soil ionization which need to be focused in order to improve the earthling. Thus, this paper evaluates on the factors that affect the behaviour of the earthling system based on simulation works using MATLAB and Safe Grid Software. Some analytical calculations are used to obtain the soil resistivity and resistance as well as the touch and step voltages. The simulation results were validated based on comparison with other studies on the factors that influence the earthling system performance. The results reveal that the variation of soil resistivity, the configuration of electrodes, current magnitude and frequency dependence can result in a change of transient response of the systems.

Three-Dimensional Explicit Dynamic Numerical Method to Simulate a Deep-Sea Pipeline Exhibiting Lateral Global Buckling

Deep-sea pipelines exhibit lateral global buckling under high temperature and pressure differences. Numerical simulations are an effective and easy way to obtain the deformation and stress distribution of a post-buckling pipeline with a low cost. A relatively accurate and convenient simulation model using the explicit dynamic method was developed based on ABAQUS software to analyse pipeline lateral global buckling. In pipeline global buckling analysis, the dynamic variation of soil resistance as the pipeline moves laterally, the optimized computational length and the use of smooth initial imperfection profiles influence the accuracy of the simulation results. These three key factors were discussed here, and calculation methods were proposed. A CEL simulation model with improved boundary conditions that reduce the influence of wave reflection with a low calculation time cost was built to calculate the variation dynamics of soil resistance throughout the buckling process. Different computational lengths for pipelines with different parameters were simulated, and a fitting function to obtain an optimized computational length was proposed. A method to build the profiles of a pipeline with smooth imperfections was developed. Based on these analyses of the three impact factors, a relatively accurate and convenient simulation model for pipeline global lateral buckling analysis was established. Finally, an engineering case was evaluated to show the application of the simulation model and to test the reliability of this model.

Load cycling of underground distribution cables including thermal soil resistivity variation with soil temperature and moisture content

As it is known the load of distribution cables is not constant with respect to the daytime, increasing the current in some hours may lead to an increase of soil surrounding the cable resistivity due to the migration of soil moisture content. Formation of dry zones may cause failure of cable insulation. Also because the soil thermal properties change with time according to the weather conditions of different seasons, the current capacity changes significantly from time to time. This paper studies the effect of dry zone formation during load cycling of underground cables on their temperature rise and the temperature distribution in the surrounding which is not considered by IEC 60853-2. The thermal model of the cables using the thermoelectric equivalent method is modified by including the thermal soil resistivity variation with soil temperature and moisture content. The finite element method is used also in this study to obtain heat map of the cable and surrounding soil. Additionally, experimental work of three soil types was investigated to study the effect of temperature and moisture content variation on the soil thermal resistivity and the dry zone formation of each soil type. Field measurements of temperature distribution surrounding the cables are done.

Development and performance evaluation of an electric-hydraulic control system for subsoiler with flexible tines

Subsoiling is primary practice in conservation tillage fields, as it disrupts compacted soil hardpans that restrict crop root growth and water infiltration. Subsoiler with flexible tines presents effective obstacle avoidance and draft force reduction, but the undesired depths, much less than target value, are observed during tillage operation due to the considerable variation in soil resistance. Therefore, an electric-hydraulic control system for subsoiler with flexible tines was developed and a novel method for detecting tillage depth was described. The performance of the electric-hydraulic control system was evaluated in soil bin experiment by the detecting accuracy of the tillage depth and the operation quality (qualified index, distribution uniformity of tillage depths and draft force reduction). The detecting accuracy of the electric-hydraulic control system was determined at target depths of 25 and 30 cm, by testing tillage depths and comparing with manual measurement. The values obtained by the control system differed from manual measurements by less than 3.2% (3.2% at 25 cm; 1.9% at 30 cm), indicating high accuracy. The operation quality of the electric-hydraulic control system was evaluated for the working speeds of 1.4, 2.0, 2.6 km/h at target depth of 30 cm, by testing the tillage depth, draft force obtained with and without the electric-hydraulic control system. Treatments without the electric-hydraulic control system (CP) were five types of constant hydraulic pressure, respectively 2.0 MPa (CP 2.0), 2.5 MPa (CP 2.5), 3.0 MPa (CP 3.0), 3.5 MPa (CP 3.5) and 15 MPa (CP 15). Treatments with the electric-hydraulic control system (AP) were adjustable hydraulic pressure with the range of 2.0–3.5 MPa. Results indicate that flexible tine with AP created more regular cutting cross-section and acquired relatively consistent tillage depth. The qualified indexes of tillage depth (QI) were respectively 97.5%, 98.2%, and 96.7% at the forward speeds of 1.4, 2.0, 2.6 km/h. And mean tillage depths with AP were respectively 29.54, 29.53, 28.13 cm, closely to target depths. The distribution uniformity of tillage depth with AP was better than CP. Furthermore, draft force increased at the area with high soil resistance, flexible tines with AP experienced a relatively more stable rise and obtained draft force reduction of 18.17%, 18.35%, and 25.89% at three forward speeds. The results demonstrate that the developed system can be used to improving the tillage quality for subsoiler with flexible tines.

New fault location scheme for four-circuit untransposed transmission lines

This paper introduces a new fault location scheme for two-terminal four-circuit untransposed transmission line using synchronized measurements. The current phasors at both line terminals and the voltage phasor at only one terminal are needed to formulate the fault location equation. The proposed scheme is developed based on theory of transmission lines and expansion of Taylor series for the distributed line model parameters. The mutual coupling between all phases and the untransposition of the line are considered to obtain precise results. The faulty phases are determined using Kirchhoff’s current law (KCL) and all fault types including normal shunt and inter-circuit faults can be located. DIgSILENT Power Factory software is used to simulate the power system and the fault location calculations are carried out using MATLAB. The proposed scheme is investigated under different fault locations, fault inception angles, fault types, and fault resistances. The influence of soil resistivity variation, measurement and synchrophasors errors, errors in line parameters, various line lengths, non-linear time-varying arc resistance, and complex fault impedance is also investigated. The simulation results confirm the validity of the fault location scheme for all test cases.

The Calculation of Corrective Coefficient for Grounding Electrode Resistance according to Variation of Soil Resistivity by Field Measurement

The Calculation of Corrective Coefficient for Grounding Electrode Resistance according to Variation of Soil Resistivity by Field Measurement

A Practical Soil Resistivity Electrical Earthing Investigation: Ile-Ife, Nigeria

Electrical earthing design surge protection relies on accurate determination of soil resistivity down the vertical soil profile. The study investigated soil resistivity of a rocky region in Ile-Ife, Nigeria, were wenner method claimed to be failed. Pole-pole and Schlumberger electrode configurations method were deployed and electrical resistivity (ER) methods involving both horizontal profiling (HP) and Vertical Electrical Resistivity (VES) using an intelligent machine – ABM 300 C. Measurements were made along seven traverses to revealed soil resistivity variation in the region. Forty-eight VES stations were occupied along the traverse using the Schlumberger array with electrodes spacing of (AB/2) varying from 1 to 60 m. The vertical electrical sounding data were interpreted quantitatively by partial curve matching and iterative modelling using WinglinkTM software. Geoelectric sections were generated on each of the traverses using the VES interpretation results. The result of this research revealed variation down the layers (profile). The resistivity ranges from 30 Ohms-m to 4893 Ohms-m and the thickness from 0.44 m to 13.7 m within the conductive layers respectively.

Wavelet neural network methodology for ground resistance forecasting

Motivated by the need of engineers for a flexible and reliable tool for estimating and predicting grounding systems behavior, this study developed a model that accurately describes and forecasts the dynamics of ground resistance variation. It is well-known that grounding systems are a key of high importance for the safe operation of electrical facilities, substations, transmission lines and, generally, electric power systems. Yet, in most cases, during the design stage, electrical engineers and researchers have limited information regarding the terrain's soil resistivity variation. Moreover, the periodic measurement of ground resistance is hindered, very often, by the residence and building infrastructure. The model, developed in the present study, consists of a nonlinear, nonparametric wavelet neural network (WNN), trained in field measurements of soil resistivity and rainfall height, observed the past four years. The proposed framework is tested in five (5) different grounding systems with different ground enhancing compounds, so that can be used for the evaluation of the behavior of several ground enhancing compounds, frequently used in grounding practice. The research results indicate that the WNN can constitute an accurate model for ground resistance forecasting and can be a useful tool in the disposal of electrical engineers. Therefore, this paper introduces the wavelet analysis in the field of ground resistance evaluation and endeavors to take advantage of the benefits of computational intelligence.

Temporal variation in soil resistance to flowing water erosion for soil incorporated with plant litters in the Loess Plateau of China

Plant litter can be incorporated into topsoil under natural circumstances by soil splash, sediment deposition, and soil-dwelling animal activities. The incorporated litter can change the mechanical properties of soil and the decomposition of the incorporated litter can improve soil structural stability. Those changes likely influence soil detachment process by overland flow. This study was undertaken to quantify the effects of incorporated plant litters into topsoil on the temporal variation in soil resistance to detachment by overland flow using natural soil samples collected from four different plots (one control and three litter incorporation treatments) and then scoured under six different flow shear stresses in a hydraulic flume. The experiment started from April 19 to October 5, 2015 for 10 times at approximately 20days sampling intervals. Soil properties and environmental parameters were also measured at each sampling time to explain the temporal variations in rill erodibility and critical shear stress. The results showed that the incorporated plant litter was effective to enhance soil resistance to flowing water erosion. Compared to bare soil, rill erodibilities of litter incorporated soils of black locust, sea buckthorn, and green bristle grass decreased by 24.3%, 33.5%, and 34.8%. The temporal variations in rill erodibility of bare and litter incorporated soils were similar. Rill erodibility decreased significantly over time as an exponential function for both bare and litter incorporated soils. The relative rill erodibility of three litter incorporated soils increased over time as a power function. The fitted critical shear stress increased exponentially over time. The temporal variations in rill erodibility could be explained by the temporal variations in soil consolidation, water stable aggregate, and litter decomposition. Rill erodibility could be well estimated by soil bulk density, water stable aggregate, and litter mass density (r2=0.92).

Zbijenost tala vinograda razlicite starosti u Panonskoj Hrvatskoj. II dio. Modeliranje prostorne raspodjele cimbenika zbijenosti tala u vinogradu

Geostatistical modeling with different interpolation methods represents progress in describing and monitoring the spatial variability of soil properties. By choosing the proper interpolation method it is possible to produce distribution maps of investigated soil properties which are characterized by significant accuracy, and thus reduced required number of samples for the soil description and determination. On the example of determined soil penetration resistance and collected undisturbed soil samples from thirty years and seven years vineyards, and with geostatistical data analysis followed by comparison of interpolation models, spatial maps of soil resistance, bulk density and soil moisture are produced. This paper presents the applicability of GIS for characterization the spatial variation of soil resistance, bulk density and soil moisture based on 72 undisturbed samples collected at three depths (0-10 cm, 11-20 cm and 21-30 cm) and 177 measured soil penetration resistance in each of the studied vineyards located in central Croatia. The study points to the usefulness of geostatistical techniques analysis of spatial distribution of some physical soil properties. The results provided in graphical form and their associated variance, indicating the possibility of using geostatistical analysis for the sustainable management of soils in the vineyards and plans for soil conservation in the study area.

Spatial variation in soil resistance to flowing water erosion along a regional transect in the Loess Plateau

AbstractThe factors influencing soil erosion may vary with scale. It remains unclear whether the spatial variation in soil erosion resistance is controlled by regional variables (e.g. precipitation, temperature, and vegetation zone) or by local specific variables (e.g. soil properties, root traits, land use, and farming operations) when the study area enlarges from a hillslope or catchment to the regional scale. This study was performed to quantify the spatial variations in soil erosion resistance to flowing water under three typical land uses along a regional transect on the Loess Plateau and to identify whether regional or local specific variables are responsible for these changes. The results indicated that the measured soil detachment capacities (Dc) of cropland exhibited an irregular trend along the regional transect. The Dc of grassland increased with mean annual precipitation, except for two sites (Yijun and Erdos). The measured Dc of woodland displayed an inverted ‘U’ shape. The changes in rill erodibility (Kr) of three land uses were similar to Dc, whereas no distinguishable trend was found for critical shear stress (τc). No significant correlation was detected between Dc, Kr and τc, and the regional variables. The spatial variation in soil erosion resistance could be explained reasonably by changes in soil properties, root traits, land use, and farming operations, rather than regional variables. The adjustment coefficient of Kr for grassland and woodland could be well simulated by soil cohesion and root mass density (R2 = 0.70, P < 0.01), and the adjustment coefficient of critical shear stress could be estimated with aggregate stability (R2 = 0.57, P < 0.01). The results are helpful for quantifying the spatial variation in soil detachment processes by overland flow and to develop process‐based erosion model at a regional scale. Copyright © 2015 John Wiley & Sons, Ltd.

Application of an In Situ Electrical Resistivity Device to Monitor Water and Salt Transport in Shandong Coastal Saline Soil

In situ monitoring of water and salt transport in saline soil is a valuable tool for the rational exploitation and conservation of water and soil resources in coastal areas. In this paper, an automatic monitoring device was used to monitor the vertical variation of soil resistivity during leaching in laboratory and field experiments. The experimental results showed that the resistivity peak moved downwards and eventually disappeared during leaching. An equation describing the change in leaching speed over time was obtained. It was found that the desalination occurred from top to bottom and that the desalination depth was constant when the same volume of leaching fluid was applied. Resistivity indication and salinity content showed a significant exponential correlation (R (2) > 0.9). The field experiment demonstrated the stability of data transmission, and variations in apparent resistivity in one day and over a longer period were observed. Rainfall resulted in the downward migration of salt from surface soil, whereas evaporation led to migration of salt upward. The temporal and spatial resolution of this monitoring device can be adjusted to achieve dynamic monitoring, providing an easy means to manage soil and water conservation.

The Response of Grounding Electrodes to Lightning Currents: The Effect of Frequency-Dependent Soil Resistivity and Permittivity

A methodology is proposed and applied to determine the variation of soil resistivity and permittivity in the typical range of lightning current frequency components. The response of horizontal electrodes buried in high- and low-resistivity soils subjected to currents with lightning waveform patterns was measured and also simulated, taking this variation into account. The waves of the simulated and measured grounding potential rise are nearly the same but are quite different from the simulated waves considering the conventional assumption of constant values for soil resistivity and permittivity.

Seasonal Variation of Soil Resistivity and Soil Temperature in Bayelsa State

Problem statement: Due to the climatic variation for the year and it's sever harmattan during the month of December to March with the high keraunic level (80-90) in the areas, it was necessary to know the seasonal variation of soil resistivity. The seasonal variation and the nature of soil have considerable influence on electrical characteristics and therefore affect the earthling system performance. Approach: Eighteen sites were chosen from three main soil divisions. The soil resistivity was taken in each of the site at depths of 0.5, 0.8 and 1.2 m using the four point test instrument (Wenner Method). From the selected sites in the three soil divisions the temperature was also taken at depths of 0.2, 0.5, 0.8 and 1.0 m. Results: The coefficient of seasonal variation at the depth of 0.5 m was high and reduced drastically at a depth of 1.2 m. The soil temperature was higher than the ambient temperature at the depth of 0.2 m during the months of December to March. From 0.8 m depth and below the temperature reduced even during the dry seasons. Conclusion: The coefficient of seasonal variation of soil at the depth of 0.8 and 1.2 m was small (1.8-3.0) throughout the year in all soil types. That indicates the high water level and or the permanent moisture table which gives an advantage to low soil resistivity for buried conductors and electrodes in the area.

Two‐Dimensional Spatial and Temporal Variation of Soil Physical Properties in Tillage Systems Using Electrical Resistivity Tomography

The objective of this research was to assess the effects of different tillage systems on the spatial and temporal variation of soil resistivity and soil features related to resistance to penetration and porosity using Electrical Resistivity Tomography (ERT). Two‐dimensional (vertical and horizontal) ERT was performed on long‐term conventional deep tillage (CT), minimum tillage (MT), no‐tillage (NT), and by tilling a no‐till plot (freshly tilled no‐till [FTNT]). The tillage treatments were compared in two different studies with measurements taken at different scale and with two different sampling configurations. The first study consisted of ERT measured on a 5.75 m linear transect with horizontal and vertical high resolution measurements and a second study performed at the field scale using an on‐the‐go automatic resistivity profile. The on‐the‐go equipment collected data simultaneously at three different depths (50, 100, 200 cm) and data were referenced by differential global positioning systems (DGPS). Total variation in soil resistivity was significantly explained by tillage treatment and soil depth and by their interaction. The response of soil resistivity to tillage was able to significantly discern between tilled and untilled soil, and between FTNT and the old tillage. Soil resistance to penetration also allowed to detect highly significant differences between the untilled and other treatments at 5 cm, but did not discriminate between FTNT and the other tilled treatments, due to high variability. The automatic resistivity profiling (ARP) measurements were affected by fresh tillage, given the strong response of resistivity to soil bulk density for the first layer.

Chronostratigraphic study of the Grottaperfetta alluvial valley in the city of Rome (Italy): investigating possible interaction between sedimentary and tectonic processes

We carried out geomorphologic and geological investigations in a south-eastern tributary valley of the Tiber River in Rome, the Grottaperfetta valley, aimed to reconstruct its buried geometry. Since results of the geomorphologic study evidenced anomalies of the stream beds, we performed geoelectric and boreholes prospecting to check whether recent faulting, rather than an inherited structural control, possibly contributed to the evolution of the alluvial valley. Vertical offsets of the stratigraphic horizons across adjacent boreholes were evidenced within the Late Pleistocene-Holocene alluvium and its substratum. In order to rule out the effects of irregular geometry of the alluvial deposits, we focussed on sectors where vertical offsets affected all the stratigraphic horizons (alluvium and pre-Holocene substratum), showing an increasing displacement with depth. We identified a site where repeated displacements occur coupled with a lateral variation of soil resistivity, and we drilled an oblique borehole aimed to cross and sample the possible fault zone affecting the terrain. A 7 cm thick granular layer, inclined 50°÷70° on the horizontal, was recovered 5 m b.g., and it was interpreted as the filling material of a fracture. The convergence of the reported features with independent evidence from geoelectric and geomorphologic investigations leads to hypothesize the presence of a faulting zone within the Holocene alluvial terrains and to propose the excavation of a trench to verify this hypothesis.