Large Language Model Based Prediction of SPT N value from Electrical Resistivity Correlations

Soil is considered by the engineer as a complex material produced by weathering of the solid rock. Soil is the most important material, which is used for construction of civil engineering structures. Among all parameters, the bearing capacity of soil to support the load coming over its unit area is very important. There are various methods for calculation of bearing capacity of soil put forth by scientists like Prandtl, Terzaghi, Meyerhoff, Hansen, Vesic, and others. Principal factors that influence ultimate bearing capacities are type of soil, width of foundation, soil weight in shear zone, and surcharge. Structural rigidity and the contact stress distribution do not greatly influence bearing capacity. Bearing capacity analysis assumes a uniform contact pressure between the foundation and underlying soil. With other factors unchanged, the type of failure of soil, depth of foundation, and effect of water table also govern the bearing capacity of soil. Field tests are very important in knowing the actual performance of soil after loading. Commonly used field tests are plate load test and standard penetration test. In the present study, standard penetration tests are conducted at site. Pit was excavated for different depths, i.e., 1.5, 2.0, 2.5, and 3.0 m, and the soil samples from these depths were collected for determination of its geotechnical properties. Based on these properties, safe bearing capacities were determined by IS code method. At each depth, standard penetration tests were conducted to know the number of blow count “N.” Based on the blow count “N,” safe bearing capacities were determined by empirical equation. The values of safe bearing capacities obtained at different depths by both methods are compared. They show the fairly good agreement at lesser depth of foundation, but as depth of foundation increases, the safe bearing capacity based on blow count “N” is found to be higher.KeywordsStandard penetration testDepthMoisture contentDensityCohesion

The performance of subgrade soil can decay during long-term service. The moisture content and compaction degree are important control indicators for subgrade construction. Therefore,soil moisture content control and compaction quality are the key factors in the performance evaluation of subgrade. The research results can provide a theoretical basis for the detection and evaluation of the engineering properties of subgrade soil. In order to make up for the deficiencies of the existing detection methods,we developed a rapid indoor test device for soil physical parameters based on the quadrupole electric measurement method,while we changed the water content between the different compactions. We carried out a series of laboratory tests on the resistivity and polarizability of soil samples and obtained the correlation and change trend. We analyzed the influence of water content and compaction on electrical parameters and proposed the soil moisture content and compaction degree. We calculated the calculation formula of resistivity and polarizability and discussed the feasibility of the test method. The results show that the resistivity of soil in different regions decreases with the increase of water content and compaction. The polarizability of soil increases with the increase of water content and compaction. Under different compaction degrees,the resistivity and polarity of soil shows a similar index and logarithmic characteristics with the change of water content. For the loam of Wangqingtuo area in Tianjin,when the compaction degree ranged from 84.47% to 94.41% and the water content changed from 15% to 20%,the resistivity falls to original 1/3~1/2 times and the polarizability falls to 1.4~2.3 times. And we obtain the indoor fitting formula. In practical engineering,the resistivity method is more suitable for soil moisture detection,and the polarizability method is more suitable for soil compaction detection. The comprehensive resistivity and polarizability index have good prospects for roadbed engineering. The research results can provide a theoretical basis for the detection and evaluation of the engineering properties of subgrade soil.

Abstract. The bearing capacity of soil changes owing to the mechanical properties of the soil and influences on structural stability. In most of the geotechnical engineering projects, there are several soil mechanic experiments, they need interpretation before application. The mechanical properties of soil interaction make complex predict of soil bearing capacity. However, to enhancement safety of construction project need to the interpretation of soil experiments and design results for proper application in a geotechnical engineering project. In this study, artificial neural networking is proposed for the evaluation of the mixed soil characteristics to forecast the safe bearing capacity of soil because of the mechanical properties of the soil interaction phenomenon. The results reveal for prediction of the safe bearing capacity, the R2 and RMSE for all mechanical properties effects on safe bearing capacity are 0.98 and 0.02, these values can provide a suitable accuracy for prediction safe bearing capacity of the mixed soil. The higher inaccuracy obtained when only the influence of single mechanical property on the mixed soil considered in prediction of the safe bearing capacity. This study supports the enhancement of geotechnical engineering design quality through prediction safe bearing capacity from characterized mechanical properties of the soil.

Vertical electrical soundings (VES) and standard penetration test (SPT) were carried out at Ahmadu Bello University Phase II, Zaria, Nigeria, with the aim of correlating between transverse resistance (T) and number of blows per counts (N-value) for foundation studies. Two (2) SPT and VES using Schlumberger electrodes array, were conducted within the study area. The VES data acquired from the field were processed and interpreted using AGI earth imager 1D software. Borehole data of exact point, where the VES was carried out were used for calibration. The results obtained from the VES depicts that the depth to basement values ranges between 6.5 and 8.0 m which agree with the borehole data obtained from the SPT results. The results of resistivities and thickness obtained from the VES curve were used to compute transverse resistance. The transverse resistance was used to correlate with the N-values obtained from SPT data. It was observed that the correlation of transverse resistance and N-value was linear and highly positive. The linear relationship that was established between the two parameters can be used to determine the soil strength at any point within the area of study.

The soil characterization is one of the major prerequisites in grounding system studies. Along with an adequate measurement procedure and a reliable field data processing, they are responsible for the success in the design and the installation of grounding grids in electrical power systems. In this frame of reference, the purpose of this work is to present an embracing investigation combining <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> measuring data from soil resistivity and geological survey, supported by the Wenner method and standard penetration test (SPT). The study is focused on investigating the differences in the apparent soil resistivity interpretation, provided by distinct approaches, identifying the one that better correlates with SPT. Furthermore, a geoelectrical and geotechnical soil characterization is in-depth evaluated, culminating in the derivations among soil resistivity, moisture content, and its mechanical properties. The study has a particular application, but not restricted, to electrical substations design, in which a proper soil modeling and representation are mandatory. The obtained results are promising serving as a foundation for further investigation.

This study has been carried out to assess the competence and suitability of the soil stratum so that the foundation and soil underneath can safely bear the incoming load of the court building without the risk of shear failure and undesirable settlements. Standard penetration tests (SPT) were carried out at the proposed site in Sikandra Rao, District Hathras, Uttar Pradesh, and thirty-five soil samples were collected at 1.5 m depth of interval up to 10.5 m depth from the five bore holes and brought to the laboratory for further geotechnical investigations. Laboratory tests conducted on collected disturbed/undisturbed soil samples include sieve analysis, hydrometer analysis, liquid limit and plastic limit, natural moisture content, bulk and dry density, specific gravity and tri-axial shear tests. The soil bearing capacity was determined by settlement and shear criteria according to the procedure laid down by the relevant IS codes. The explorations up to significant depth helped in deciding the minimum depth and type of foundation best suited in the existing situation and the safe bearing capacity of the soil. The investigations also helped in detecting the filled-up stretch or the presence of discontinuities, cavities or zones of weakness beneath the proposed foundation within the zone of pressure bulb. These were taken into account while making recommendations for safe bearing capacity and the type of foundation suitable under the prevailing soil conditions.KeywordsBore holesSoil investigationSafe bearing capacityFoundation

This paper presents the results of an investigation into the interaction between the various electrical factors pertaining to resistivity tests in Perth sandy soil (specifically AC input voltage and frequency) and those controlling the soil characteristics, specifically water content and relative density of the soil, and the type of water employed in the tests, whether distilled or tap water. The experimental apparatus was developed as per Australian standard AS 1289.4.4.1-1997 and was used for the electrical resistivity measurements. The test results indicate that the resistivity of the sandy soil is almost independent of both AC input voltage and frequency within the ranges used, while the choice of electrode material has an insignificant effect on the outcome of tests using this method. It was observed that the resistivity of sandy soil decreased rapidly with an increase in water content, but the rate of decrease reduced considerably for water contents over 12% in the case of distilled water and 10% for tap water, irrespective of the relative density. The resistivity was found to decrease almost linearly with an increase in relative density. However, the effect of relative density on the electrical resistivity of the soil was found to be negligible at higher water contents. Correlations between electrical resistivity, water content and relative density, which are applicable to the soil and water used in the study, are also presented.

Spatial information about soils generally results from local observations which are destructive and time consuming. Geophysical techniques could help soil mapping since they are non-destructive and fast. Electrical resistivity is interesting for soil studies due to a wide range of values and as it depends on soil characteristics. This work aims to study soil spatial variability using electrical resistivity. GPS defined grid points of 40X40 m were installed in the experimental western farm (EWF) in the Faculty of Agriculture of Cairo University in Giza. Electrical resistivity was measured at 40 points using 4-electrodes Wenner array in a line perpendicular to the path direction. Soil resistivity data from 2-depths profiling mode was considered to produce two apparent resistivity maps and geostatistically tested. Soil resistivity taxa were sampled and analyzed for soil moisture, EC and bulk density. Krigged soil resistivity maps were produced for depths (i.e. 30 and 60 cm). Kriging and Semivariogram interpretation was conducted, and the spatial dependency of top and subsoil resistivity were moderate (48.4% and 68.6% respectively). Highly significant negative correlations were recorded in the topsoil between apparent or true resistivity and soil moisture, EC or bulk density. The obtained models were used to produce conjugated moisture and EC maps and geostatistically investigated. The spatial dependency of the top and subsoil moisture or salinity were moderate. Soil moisture and EC are the most significant factors for controlling soil electrical resistivity. The method used opens the way to the development of semi-automatic soil mapping from electrical resistivity data.

This paper shows the performance of multi-layer soil electric resistivity model comparing with two-layer characterizations in geotechnical investigations. In conventional model, there are inter-relationships between soil apparent electrical resistivity (ρ) and several soil physical or chemical properties. These empirical relationships show limitations to obtain specific soil characterizations of different layers with. Multi-layer true resistivity model is the improvement of conventional two-layer earth model including the criteria of four points probe method. Multi-layer soil resistivity profile shows more accuracy to obtain near surface soil characteristics including the types of soil and rocks, and to detect anomalous materials in soil profile. Alternatively, apparent resistivity in two-layer model can be used to obtain deeper profile of soil characteristics. In this multi-layer soil model, the soil resistivity and resistivity ratio corresponding to the depth in soil medium are considered for geotechnical investigations. Two-layer model includes soil apparent resistivity according to probe distances in depth corresponding resistivity profile. This paper is important for including criteria and performance of multi-layer soil resistivity model and conventional two-layer model for geotechnical characterizations.

Recently in China, the deep mixing method has been widely used for soft ground improvement. Standard penetration tests and the unconfined compression tests of samples are combined to check and control the quality of soil-cement columns. However, these tests cause destruction of soil-cement columns and consume both time and cost. The electrical resistivity method is an alternative which has the advantage of being non-destructive and time-effective. The present research aims to quantify the influence of salt concentrations on the electrical resistivity of cement-treated soils. Clay was mixed with different quantities of sodium chloride salt and cement to evaluate the influence of additional salt on the electrical resistivity. The electrical resistivity of cement treated soil was measured after 28 days curing period. The results indicate that the electrical resistivity of cement treated soil decreases with the increase of salt concentrations and that the increase of cement content results in an increase of electrical resistivity. The results show that a unique exponential function well adapts electrical resistivity values with cement content and salt concentration. The porosity-salt concentration/cement content ratio is an appropriate parameter to assess the electrical resistivity of the cement-water-soil mixtures investigated.

This study evaluated whether electrical resistivity monitoring could be used as a tool to detect the activation of macropores in soils. Experiments were performed where soil resistivity was measured using a Wenner array while individual soil macropores were sequentially saturated to simulate changes in macropore activation in a hydrologically active soil. The measured apparent resistivity was found to be highly dependent on the activated macropore porosity. An increase in macropore porosity from 0 to 4% decreased the apparent resistivity of the soil by up to 30%. A simple two‐domain model was developed to evaluate the controls on apparent resistivity in a macroporous soil by conceptualizing the macropores as fluid‐filled tubes embedded within a homogeneous soil matrix. The model qualitatively reproduced the trends of the observed data and provided reasonable bounds on the expected response of soils, suggesting that it captures first‐order influences of macropores on apparent resistivity measurements. The model indicates that the magnitude of the reduction in apparent resistivity is strongly dependent on the contrast in resistivity between the soil ( r o ) and macropores ( r m ), which can be readily estimated in field monitoring scenarios. The r o / r m ratio is therefore suggested as a useful diagnostic for evaluating conditions where changes recorded in resistivity monitoring data might be used to detect the onset of macropore flow in field‐based studies.

Borehole samples drilled up to a depth of 10 m provide a clear understanding whether a foundation is safe for any structure. The main objective of the present study reconnoitered the soil bearing capacity and foundation settlement characteristics using the standard penetration test (SPT) data obtained from 3 boreholes at 1 m, 2 m, and 3 m depths to correlate soil properties and deterrents, if any, created by groundwater. The methodology of the research is to collect soil samples, and ensuing subsoil analysis was performed in order to obtain concrete information to optimize the foundation system within the safe bearing capacity of soil and its allowable settlement. The scope of the work encompasses conducting detailed soil investigation from drilling logs, laboratory testing, and conducting and estimating safe bearing capacity. The result of the research aims at providing safety to the foundation from the investigations of conclusive recommendation to be adopted which would be economically feasible and structurally secured.

With increasing engineering projects carried out in cold regions, the analysis and evaluation of the thermal conductivity and electrical resistivity of frozen soil have become important considerations in engineering construction and theoretical research. Through experiments performed on silty clay, the effects of the initial water content and soil temperature on the thermal conductivity and electrical resistivity of silty clay soil were analyzed. Theoretical models were also formulated for the soil thermal conductivity and electrical resistivity. The results showed that the variations in the thermal conductivity and electrical resistivity can be discussed as three stages: the freezing prophase, freezing metaphase and freezing anaphase. The electrical resistivity increases rapidly in the temperature range − 2 °C to −6 °C. The thermal conductivity increases rapidly from −2 °C to −4 °C and then decreases slightly from −4 °C to −6 °C due to the development of frost heave cracks in samples with higher water contents (15%, 18% and 20%). However, the thermal conductivity of samples with a water content of 10% continues to increase under these conditions. At the same temperature, the thermal conductivity increases linearly with water content in general. The electrical resistivity decreases approximate linearly with water content from 10 °C to −4 °C and increases with increasing water content from −4 °C to −20 °C. The thermal conductivity is inversely proportional to electrical resistivity from 10 °C to −4 °C and is proportional to electrical resistivity from −10 °C to −20 °C. The results of the experiments performed on silty clay soil verify the soundness of the proposed model for the thermal conductivity and electrical resistivity of unfrozen and frozen soil.

Apparent resistivity images of thin sheet like models having a complicated geometry are studied in a wide period-range by means of three-dimensional (3D) numerical modelling. Fifteen different definitions of the apparent resistivity are calculated using five different functions [¦f(Z)¦, Re f(Z), Im f(Z), f(ReZ), and f(ImZ)] of three rotational invariants f of the magnetotelluric impedance tensor [f(Z) = Z12 = (Zxy − Zxy)2/4; f(Z) = det(Z) = Zxx · Zyy − Zxy · Zyx; f(Z) = ssq(Z) = Zxx2 + Zxy2 + Zyx2 + Zyy2]. A simple visual analysis of apparent resistivity maps and of sounding curves averaged over and around a conductive (and a resistive) heterogeneity embedded in a homogeneous half space is presented. The imaging properties appear to depend much more on the apparent resistivity definition than on the rotational invariant itself. Except for the very short period range corresponding to the oscillating section of the sounding curves, a robust and regular behaviour of the imaging parameters is observed. In this so called “normal” period range the 3D imaging properties seem to be the best if the apparent resistivity is derived when using the function ReZ, i.e. when computing the rotational invariant with the real parts of the four impedance tensor elements. For apparent resistivities derived from ReZ, a rapid convergence over lateral resistivity contrasts and oscillations with small amplitude over homogeneous areas are actually observed in the apparent resistivity maps. In the period domain, they are characterised by a maximum rate of convergence to the underlying resistivity at longer periods and by a reasonably small standard deviation, even in presence of a near-surface disturbing body.

Flood defense structures are becoming increasingly vulnerable to failure from escalating threats of climate change. This challenge is evident in the network of agricultural earthen dykes along the Bay of Fundy coastline in Atlantic Canada, which safeguard economically critical infrastructure in the region. Addressing these vulnerabilities requires assessment methods to guide engineering interventions ranging from rehabilitation to reconstruction. Non-invasive geophysical techniques, such as electrical resistivity imaging (ERI), are gaining prominence for assessing flood embankments. ERI can detect subsurface electrical resistivity anomalies that are potentially indicative of internal zones of weakness.This study investigates the application of ERI in evaluating and guiding dyke rehabilitation strategies in the Upper Bay of Fundy. The objectives are to: 1) develop a rapid screening approach capable of imaging potential internal weak zones; 2) assess the effectiveness of ERI in identifying structural vulnerabilities; 3) examine the primary factors influencing resistivity variations, including grain size distribution and pore water salinity; and 4) evaluate the impact of tidal level fluctuations on ERI imaging. A series of geophysical field investigations were conducted at Shepody dykelands in southern New Brunswick, between 2022 and 2024. This included a shallow EM apparent conductivity mapping, 2D ERI and a time-lapse 3D ERI survey. The latter was carried out over a period of 3.5 hours during which time the megatidal Bay of Fundy rose about 3 m, advancing approximately 100 m over tidal mudflat and grassland before rising up against the side of the roughly 2.5 m high dykes. The increasing tide level was anticipated to influence resistivity measurements. The timelapse 3D ERI survey utilized a novel electrode array configuration to enhance sensitivity without severely compromising survey efficiency. Furthermore, complementary geotechnical data were collected in 2024 through Standard Penetration Tests (SPT) using a split spoon sampler. Laboratory analysis of the samples measured resistivity, grain size distribution and pore water conductivity.The 2D ERI inversion results reveal significant subsurface resistivity anomalies within the dyke, highlighting localized zones of elevated conductivity within the dyke. The correlation of various laboratory measurements indicates a stronger relationship between soil resistivity and pore water conductivity than grain size distribution. We conclude that the increased conductivity observed by 2D ERI is primarily caused by the presence of highly conductive saline water that has intruded into the dyke in areas of higher hydraulic conductivity during high tide. Such regions could be at risk from seepage-induced internal erosion, piping, or other anomalous geotechnical conditions. Time-lapse 3D ERI inversion results demonstrated the real-time effects of tidal variations on resistivity profiles, providing insights into measurement deviations caused by tidal influences. These findings underscore the effectiveness of ERI in assessing coastal flood embankments by identifying critical regions within flood dykes that should be prioritized for monitoring or further sampling to determine their potential impact on structural integrity. The results of this study demonstrate the capability of ERI to provide valuable insights that can enhance the resiliency strategies of flood defense structures.