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Accelerated climate warming is causing significant reductions in the volume of Arctic glaciers, such that previously ice‐capped bare ground is uncovered, harboring soil development. Monitoring the thermal and hydrologic characteristics of soils, which strongly affect microbial activity, is important to understand the evolution of emerging terrestrial landscapes. We instrumented two sites on the forefield of a retreating Svalbard glacier, representing sediment ages of approximately 5 and 60 years since exposure. Our instrumentation included an ERT array complemented by adjacent point sensor measurements of subsurface temperature and water content. Sediments were sampled at each location and at two more additional sites (120 and 2000 years old) along a chronosequence aligned with the direction of glacial retreat. Analysis suggests older sediments have a lower bulk density and contain fewer large minerals, which we interpret to be indicative of sediment reworking over time. Two months of monitoring data recorded during summer 2021 indicate that the 60‐year‐old sediments are stratified showing more spatially consistent changes in electrical resistivity, whereas the younger sediments show a more irregular structure, with consequences on heat and moisture conductibility. Furthermore, our sensors reveal that young sediments have a higher moisture content, but a lower moisture content variability. [ABSTRACT FROM AUTHOR]

Subsurface formations with low compaction, often, due to the presence of underlying cavities, are potential sources of hazards. Thus, understanding the occurrence, properties, and extension of these weak zones poses a major concern in engineering geophysics. In this study, we examine the ability of geophysical methods to map weak areas over carbonates in Northern Oman. The weak zones are known to cause surface depression in many areas. The geophysical methods examined involve Ground-Penetrating Radar (GPR), Seismic Refraction Tomography (SRT), and Electrical Resistivity Tomography (ERT). This integrated geophysical survey was conducted near the Bimmah sinkhole, in the Quriya area, Northern Oman. The survey covers both an area with ground truth (low compaction sediments overlaying a cave) and a part with unknown subsurface properties. GPR velocity analysis using selected diffraction's fitting helped to identify high-velocity anomalies that were attributed to the cavity. The GPR interpretation was calibrated with SRT and ERT. The former showed a clear drop in P-wave velocity and low ray coverage at the cavity zone, while the latter demonstrated high resistivity anomalies caused by the air filling the cavity. The scope was to examine the geophysical methods response, especially the GPR, and utilize the results of this preliminary approach for a wider exploration investigation in the area. The results from the study indicated that the GPR is capable to serve as a pioneer method in detecting the cavities. Hence, the GPR will cover large area in the site and the other two methods will be used as complementary for the final subsurface conditions' evaluation. [ABSTRACT FROM AUTHOR]

Ground improvement by permeation grouting is widely utilized for improving engineering properties of soil. The accurate evaluation of a region improved by grouting is a critical issue to ensure the performance of grouting; nevertheless, current methods to evaluate the area of grouted bulbs under the ground are not well-documented. This study aims to use cross-hole electrical resistivity tomography (CHERT) to evaluate a grouted bulb region by considering the effect of electrode configuration at laboratory scale using a cylindrical container filled with saturated sand. Curing time monitoring was also conducted on grouted bulbs with various recovered Carbon Black (rCB) concentrations. Based on the inverted result, the predicted area of the grouted bulb was addressed, and then the error value between the actual and predicted areas was examined. The results of this study show that CHERT can be employed to assess the location and area of a grouted bulb. Also, it was observed that electrode spacing, damping factor, and curing time had significant influences on the image resolution and error value. Unlike the above-mentioned factors, change of rCB concentration ratio had only a slight effect on the image resolution. Thus, the use of a small amount of rCB as an additive material to enhance the grout strength can also provide a distinct contrast of measured resistivity between the grouted bulb and surrounding soil. In this study, a grouted bulb containing 3% of rCB is recommended based on the test results on strength characteristics. In addition, CHERT measuring can be conducted even in early stages of curing, during which it exhibits a better electrical resistivity contrast between the objective area and the surrounding soil. [ABSTRACT FROM AUTHOR]

A geoelectrical survey was carried out outside the walls of the ancient Egnazia (Puglia, Italy) with the aim of enriching the knowledge about its defense system. Nine Electrical Resistivity Tomographies (ERTs) were realized using the dipole-dipole (DD) electrode array, approximately transversal to the walls and equally spaced. The new Extended data-adaptive Probability-based Electrical Resistivity Tomography Inversion Method (E-PERTI) was applied, for the first time, to model the resistivity distribution of a large dataset. Considering some peculiar aspects of the general theory of probability, an optimization of results was reached giving major emphasis to one dataset portion rather than another and inspecting selectively vertical or lateral resistivity variations. In this way, sets of aligned resistivity lows attributable to the trace of an ancient ditch were found. [ABSTRACT FROM AUTHOR]

Subsurface formations with low compaction, often, due to the presence of underlying cavities, are potential sources of hazards. Thus, understanding the occurrence, properties, and extension of these weak zones poses a major concern in engineering geophysics. In this study, we examine the ability of geophysical methods to map weak areas over carbonates in Northern Oman. The weak zones are known to cause surface depression in many areas. The geophysical methods examined involve Ground-Penetrating Radar (GPR), Seismic Refraction Tomography (SRT), and Electrical Resistivity Tomography (ERT). This integrated geophysical survey was conducted near the Bimmah sinkhole, in the Quriya area, Northern Oman. The survey covers both an area with ground truth (low compaction sediments overlaying a cave) and a part with unknown subsurface properties. GPR velocity analysis using selected diffraction’s fitting helped to identify high-velocity anomalies that were attributed to the cavity. The GPR interpretation was calibrated with SRT and ERT. The former showed a clear drop in P-wave velocity and low ray coverage at the cavity zone, while the latter demonstrated high resistivity anomalies caused by the air filling the cavity. The scope was to examine the geophysical methods response, especially the GPR, and utilize the results of this preliminary approach for a wider exploration investigation in the area. The results from the study indicated that the GPR is capable to serve as a pioneer method in detecting the cavities. Hence, the GPR will cover large area in the site and the other two methods will be used as complementary for the final subsurface conditions’ evaluation.

A geoelectrical survey was carried out outside the walls of the ancient Egnazia (Puglia, Italy) with the aim of enriching the knowledge about its defense system. Nine Electrical Resistivity Tomographies (ERTs) were realized using the dipole-dipole (DD) electrode array, approximately transversal to the walls and equally spaced. The new Extended data-adaptive Probability-based Electrical Resistivity Tomography Inversion Method (E-PERTI) was applied, for the first time, to model the resistivity distribution of a large dataset. Considering some peculiar aspects of the general theory of probability, an optimization of results was reached giving major emphasis to one dataset portion rather than another and inspecting selectively vertical or lateral resistivity variations. In this way, sets of aligned resistivity lows attributable to the trace of an ancient ditch were found.

Tailings dams are traditionally monitored by routine visual inspections combined with the use of instruments such as piezometers, topographical landmarks, and water level indicators. As they are structures that have high potential damage associated, the use of robust investigation methods is essential to ensure the operational safety of these dams. Geoelectrical methods have been successful in mapping humid zones inside the tailings dam structures, using the proper acquisition parameters and data sampling that these methods allow. This is a promising approach to investigating a tailings dam with a heterogeneous embankment made of limestone tailings, that has been in operation for 50 years in São Paulo state, Brazil. Considering its structural complexity, electrical resistivity sections were acquired with a tight profile spacing – of 10 to 15 m, processed, and modeled by applying a specific workflow. The Electrical Resistivity Tomography (ERT) operational workflow applied to the dataset obtained from two field campaigns, conducted in the embankment and the right abutment of the dam, performed well in mapping possible high water content zones inside the structure, defining a relevant element for the risk assessment. For this purpose, compartmentalization of the resistivity ranges, and three-dimensional modeling techniques were used, both constrained by the geotechnical instruments of the structure. The embankment campaign mapped zones of attention in the right abutment driving the decision to perform a follow-up survey dedicated to this region. The right abutment campaign mapped zones of high resistivity, associated with the natural terrain, composed of sandy soils, saprolite, and rock, as well as zones of low resistivity related to high moisture content regions. The geometry of these conductive zones made it possible to infer the depth of the water table in the region between the direct measurements from the instrumentation and to model zones with low resistivity values. The 3D modeling revealed that part of the conductive zones, present in the right abutment and extending to the embankment indicate a possible contribution of moisture from the natural terrain towards the embankment of the dam. Thus, the achieved results demonstrated that 3D modeling applied to the combination of the geotechnical and geophysical datasets contributes to expanding the knowledge of the internal structure of the dam and consequently the safety of the operations, especially where there is no instrumentation, improving the tailings dam risk management. • Three-dimensional model, correlating geoelectric and geotechnical information • Numerical model for modeling high moisture zones • Volumetric investigation in correlation with located geotechnical data [ABSTRACT FROM AUTHOR]

Identification of undercover karst areas can be essential for engineering or hydrogeological studies. Geological reconnaissance of karst areas can be challenging due to their complex and highly heterogeneous internal structure. Herein, we present a case study carried out at the carbonate coastal Montgrí Massif in Costa Brava (Spain), which, in the study area, is characterized by a well-developed karst system covered by Quaternary sediments. The objectives of the work are to delineate and characterize karst structures using geophysical techniques and to produce a subsurface geological model that goes beyond the individual physical properties determined independently by each geophysical method. We acquired electrical resistivity and seismic datasets for five collocated profiles. We analyzed the seismic datasets to retrieve P-wave (V p) and S-wave (V s) velocity models. Clay-filled karst formations may produce seismic and electrical signatures that are difficult to interpret due to the wide range of values that can be present depending on the properties of the karst's infill. In this type of environment, the Fuzzy c-means (FCM) data clustering approach is a way of producing an integrated model that can help to constrain the lithological interpretation. In this study, FCM is first applied to an electrical resistivity-V s dataspace in order to characterize near surface sediments. Four different groups are recognized corresponding to different lithologies, fluid conductivities, and saturations in the unconsolidated sediments. Secondly, FCM analysis of the resistivity-V p datasets provides integrated models that help to delineate the karst areas. The interpretive constraints used derive from the results of the first FCM application and the lithological description of a single borehole that reaches the karst below the Quaternary sediments. In this way, karst is identified in all five profiles. This study shows that the integration of seismic and electrical resistivity information using the FCM approach can extend borehole information throughout the study area and thus provide comprehensive geological models in karst environments. • Fuzzy-c means data clustering provides comprehensive subsurface models in karst environment. • Vs and electrical resistivity integration delineates fine/coarse sediments distribution. • Vp and electrical resistivity zonal models image karst zones. • Membership degree higher than 70% has been used as reliability criterion of the models. • Zones with lower resistivity in shallow sediments and in karst delineate saline intrusion paths. [ABSTRACT FROM AUTHOR]