scholarly journals Investigation of Dimension Stone on the Island Brač—Geophysical Approach to Rock Mass Quality Assessment

Geosciences ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 112 ◽  
Author(s):  
Jasmin Jug ◽  
Kristijan Grabar ◽  
Stjepan Strelec ◽  
Filip Dodigović
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Geophysical Methods ◽  
Dimension Stone ◽  
Seismic Velocities ◽  
Good Tool ◽  
Rock Mass Structure ◽  
Rock Mass Quality ◽  
Refraction Seismic ◽  
Geophysical Investigations

A site located on the island of Brač is known in history for world-famous architectural stone and stone mining, dating all the way back to ancient Greek and Roman times. The most famous building constructed from the stone from Brač is the Diocletian Cesar Palace in the town Split. Prospective new locations for quarries are still required because the demand for the stone from the island is still high. This paper presents a review of undertaken geophysical investigations, as well as engineering geologic site prospection, with the purpose of determining if the rock mass quality is suitable for the mining of massive blocks needed for an architectural purpose—dimension stones. Several surface noninvasive geophysical methods were applied on the site, comprising of two seismic methods, multichannel analysis of surface waves (MASW) and shallow refraction seismic (SRS) electrical methods of electrical resistivity tomography (ERT), as well as electromagnetic exploration with ground penetrating radar (GPR). Results of geophysical investigations were compared to the engineering geologic prospection results, as well to the visible rock mass structure and observed discontinuities on the neighboring existing open mine quarry. Rock mass was classified into three categories according to its suitability for dimension stone exploitation. Each category is defined by compressional and shear seismic velocities as well as electrical resistivity. It has been found that even small changes in moisture content within the large monolithic rock mass can influence measured values of electrical resistivity. In the investigated area, dimension stone quarrying is advisable if the rock mass has values of resistivity higher than 3000 Ωm, as well as compressional seismic velocities higher than 3000 m/s and shear wave velocities higher than 1500 m/s. Georadar was found to be a good tool for the visual determination of fissured systems, and was used to confirm findings from other geophysical methods.

scholarly journals Study of Rock Mass Stability Decrease due to Underground Mining

2020 ◽  
Vol 4 (4) ◽  
pp. 251-261
Author(s):  
V. I. Golik ◽  
S. A. Maslennikov ◽  
Alberto Martin Nunez Rodriguez ◽  
V. I. Anischenko
Keyword(s):  
Rock Mass ◽  
Energy Management ◽  
Underground Mining ◽  
Geophysical Methods ◽  
Electrode System ◽  
Stability Study ◽  
Rock Masses ◽  
Rock Mass Structure ◽  
Rock Mass Stability ◽  
Specific Metal

The optimization of underground mining processes is carried out based on rational use of energy for obtaining preset broken ore size. The effective optimization requires correct assessment of the properties of the rock mass to be broken. Energy management requires assessment of rock mass stability decrease due to impact of natural and technogenic stresses. To make adjustments to the general energy management model, information on the rock mass structure is required to be obtained by geophysical methods. To optimize broken rock/ore size (to minimize oversized or excessively crushed mineral fraction yield during breaking), blasting energy application should be regulated and smart. The study is aimed at assessing the effectiveness of using geophysical methods for the prompt and correct assessment of rock and backfill mass condition during underground mining of mineral deposits. Decreasing stability of rock masses is assessed using the method of electrometric surveys in noncore exploratory boreholes. Rock mass stability study allowed revealing correlation and dependencies between the studied parameters. Effectiveness of using geophysical methods for differentiating natural and technogenic masses by degree of decreasing their stability due to geological and technogenic stresses. To determine the coefficient of decreasing rock mass stability based on rock apparent resistivity data, electrometric logging was used. This allowed to differentiate rock mass by the degree of decreasing rock mass stability based on the revealed dependency. The features of the geophysical survey components are described in details. The methodology and findings of the underground electric sounding using a sequential gradient electrode system at specific metal deposit are presented, including using theoretical curves and determining rock conductivity and the distance to workings. Besides, correctness of the geophysical method findings was assessed differentially. The assessment was prepared for decreasing rock mass stability based on electrometric logging data, and for advance outlining heterogeneity zones in rock masses by electric sounding along working walls. Based on findings of the conducted experimental work on revealing structural boundaries within rock mass, the method of electric sounding along working walls was recommended for application in practice. As for the studied borehole electric sounding application, the convergence of the experimental and theoretical curves is insufficient to recommend the method for practical application.

scholarly journals Improved characterization of alpine permafrost through structurally constrained inversion of refraction seismic data

2019 ◽  
Author(s):  
Matthias Steiner ◽  
Florian M. Wagner ◽  
Adrian Flores Orozco
Keyword(s):  
Seasonal Variations ◽  
Seismic Data ◽  
Velocity Structure ◽  
Numerical Study ◽  
Geophysical Methods ◽  
Structural Constraints ◽  
Seismic Velocities ◽  
Interpretation Errors ◽  
Imaging Results ◽  
Refraction Seismic

Abstract. Geophysical methods are widely used to investigate the influence of climate change on alpine permafrost. Methods sensitive to the electrical properties, such as electrical resistivity tomography (ERT), are the most popular in permafrost investigations. However, the necessity to have a good galvanic contact between the electrodes and the ground in order to inject high current densities is a main limitation of ERT. Several studies have demonstrated the potential of refraction seismic tomography (RST) to overcome the limitations of ERT and to monitor permafrost processes. Seismic methods are sensitive to contrasts in the seismic velocities of unfrozen and frozen media and thus, RST has been successfully applied to monitor seasonal variations in the active layer. However, uncertainties in the resolved models, such as underestimated seismic velocities, and the associated interpretation errors are seldom addressed. To fill this gap, in this study we review existing literature regarding refraction seismic investigations in alpine permafrost permitting to develop conceptual models illustrating different subsurface conditions associated to seasonal variations. We use these models to conduct a careful numerical study aiming at a better understanding of the reconstruction capabilities of standard and constrained RST approaches. Our results demonstrate, that the incorporation of structural constraints in the inversion and the usage of constrained initial models help to better resolve the geometry and the velocity structure of the true models. Moreover, we present the successful application of this extended constrained approach for the inversion of refraction seismic data acquired at Hoher Sonnblick (Austria) by incorporating complementary information obtained from the modelling of ground-penetrating radar (GPR) signatures. In conclusion, our study shows the potential of an extended constrained RST to improve the reconstruction of subsurface units and the associated seismic velocities in a permafrost environment, permitting to reduce the uncertainties in the interpretation of the imaging results.

scholarly journals Resolution capacity of geophysical monitoring regarding permafrost degradation induced by hydrological processes

2017 ◽  
Vol 11 (6) ◽  
pp. 2957-2974 ◽  
Author(s):  
Benjamin Mewes ◽  
Christin Hilbich ◽  
Reynald Delaloye ◽  
Christian Hauck
Keyword(s):  
Electrical Resistivity ◽  
Seismic Tomography ◽  
Field Data ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Phase Model ◽  
Permafrost Degradation ◽  
Resistivity Tomography ◽  
Refraction Seismic ◽  
Ice Content

Abstract. Geophysical methods are often used to characterize and monitor the subsurface composition of permafrost. The resolution capacity of standard methods, i.e. electrical resistivity tomography and refraction seismic tomography, depends not only on static parameters such as measurement geometry, but also on the temporal variability in the contrast of the geophysical target variables (electrical resistivity and P-wave velocity). Our study analyses the resolution capacity of electrical resistivity tomography and refraction seismic tomography for typical processes in the context of permafrost degradation using synthetic and field data sets of mountain permafrost terrain. In addition, we tested the resolution capacity of a petrophysically based quantitative combination of both methods, the so-called 4-phase model, and through this analysed the expected changes in water and ice content upon permafrost thaw. The results from the synthetic data experiments suggest a higher sensitivity regarding an increase in water content compared to a decrease in ice content. A potentially larger uncertainty originates from the individual geophysical methods than from the combined evaluation with the 4-phase model. In the latter, a loss of ground ice can be detected quite reliably, whereas artefacts occur in the case of increased horizontal or vertical water flow. Analysis of field data from a well-investigated rock glacier in the Swiss Alps successfully visualized the seasonal ice loss in summer and the complex spatially variable ice, water and air content changes in an interannual comparison.

scholarly journals Application of electrical resistivity tomography (ERT) for rock mass quality evaluation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Hasan ◽  
Yanjun Shang ◽  
He Meng ◽  
Peng Shao ◽  
Xuetao Yi
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Quality Evaluation ◽  
Electrical Resistivity Tomography ◽  
Geological Model ◽  
Well Test ◽  
Resistivity Tomography ◽  
Entire Area ◽  
Rock Mass Quality ◽  
Geotechnical Investigations

AbstractRock mass quality evaluation is a challenging task in geotechnical investigations given the natural heterogeneity and the limited data. These investigations mainly depend on the traditional drilling tests. However, such tests are expensive and time consuming, provide point measurements, and cannot be conducted in steep topographic areas, and thus cause uncertainties in the geological model. Conversely, geophysical methods such as electrical resistivity tomography (ERT) are non-invasive, user-friendly, and fast. In this work, we establish empirical correlation between ERT and limited drilling data to obtain rock mass integrity coefficient (Kv). The estimated Kv provides 2D/3D imaging of the rock mass quality evaluation via weathered/unweathered rock and faults detection in order to cover the entire area even where no drilling test exists. Compared with the past geotechnical investigations, our work reduce the ambiguities caused by the inadequate well tests and provide more accurate geological model for infrastructures design. Our work proposes that, in case of sparse borehole data, the established empirical equations can be used to determine Kv along different geophysical profiles via 2D/3D insight of the subsurface. Our approach is applicable in any hard rock setting, and the established correlations can be used in areas even where no well test exists.

scholarly journals Engineering geological assessment of the permanent ship lock slope, the Three Gorges Project, China

2000 ◽  
Vol 22 ◽  
Author(s):  
Chen Changyan ◽  
Wang Sijing ◽  
Shen Xiaoke
Keyword(s):  
Rock Mass ◽  
Field Investigation ◽  
Three Gorges Project ◽  
Three Gorges ◽  
Element Analysis ◽  
Rock Mass Structure ◽  
The Three Gorges ◽  
Rock Mass Quality ◽  
The Three Gorges Project ◽  
Ship Lock

The permanent ship lock slope of the Three Gorges Project was excavated through the hill of granite massif with the aspect of SE(106°). Some problems of engineering geology (such as statistical features of rock mass structure) were comprehensively studied based on field investigation and numerical analysis. The numerical modelling techniques including damage variable and finite element analysis were used for the detailed study of the effect of excavation and blasting on rock mass quality and slope stability. The analyses indicate that the rock mass is relatively intact and rock mass quality varies mainly from Class I to Class II. Consequently, the overall stability of slope can be ensured except for some minor local unstable blocks.

Assessing the Condition of the Rock Mass over the Tunnel of Eupalinus in Samos (Greece) using both Conventional Geophysical Methods and Surface to Tunnel Electrical Resistivity Tomography

2014 ◽  
Vol 21 (4) ◽  
pp. 277-291 ◽  
Author(s):  
Gregory N. Tsokas ◽  
Panagiotis I. Tsourlos ◽  
Jung-Ho Kim ◽  
Constantinos B. Papazachos ◽  
George Vargemezis ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Resistivity Tomography

Quantification of ground ice through petrophysical joint inversion of seismic and electrical data applied to alpine permafrost

2020 ◽  
Author(s):  
Coline Mollaret ◽  
Florian M. Wagner ◽  
Christin Hilbich ◽  
Christian Hauck
Keyword(s):  
Electrical Resistivity ◽  
Melting Point ◽  
Joint Inversion ◽  
Geophysical Methods ◽  
Ground Truth ◽  
Ground Ice ◽  
Ground Truth Data ◽  
Water Ice ◽  
Refraction Seismic ◽  
Ice Content

<p>Quantification of ground ice is particularly crucial for understanding permafrost systems. The volumetric ice content is however rarely estimated in permafrost studies, as it is particularly difficult to retrieve. Geophysical methods have become more and more popular for permafrost investigations due to their capacity to distinguish between frozen and unfrozen regions and their complementarity to standard ground temperature data. Geophysical methods offer both a second (or third) spatial dimension and the possibility to gain insights on processes happening near the melting point (ground ice gain or loss at the melting point). Geophysical methods, however, may suffer from potential inversion imperfections and ambiguities (no unique solution). To reduce uncertainties and improve the interpretability, geophysical methods are standardly combined with ground truth data or other independent geophysical methods. We developed an approach of joint inversion to fully exploit the sensitivity of seismic and electrical methods to the phase change of water. We choose apparent resistivities and seismic travel times as input data of a petrophysical joint inversion to directly estimate the volumetric fractions of the pores (liquid water, ice and air) and the rock matrix. This approach was successfully validated with synthetic datasets (Wagner et al., 2019). This joint inversion scheme warrants physically-plausible solutions and provides a porosity estimation in addition to the ground ice estimation of interest. Different petrophysical models are applied to several alpine sites (ice-poor to ice-rich) and their advantages and limitations are discussed. The good correlation of the results with the available ground truth data (thaw depth and ice content data) demonstrates the high potential of the joint inversion approach for the typical landforms of alpine permafrost (Mollaret et al., 2020). The ice content is found to be 5 to 15 % at bedrock sites, 20 to 40 % at talus slopes, and up to 95 % at rock glaciers (in good agreement to the ground truth data from boreholes). Moreover, lateral variations of bedrock depth are correctly identified according to outcrops and borehole data (as the porosity is also an output of the petrophysical joint inversion). A time-lapse version of this petrophysical joint inversion may further reduce the uncertainties and will be beneficial for monitoring and modelling studies upon climate-induced degradation.</p><p> </p><p>References:</p><p>Mollaret, C., Wagner, F. M. Hilbich, C., Scapozza, C., and Hauck, C. Petrophysical joint inversion of electrical resistivity and refraction seismic applied to alpine permafrost to image subsurface ice, water, air, and rock contents. Frontiers in Earth Science, 2020, submitted.</p><p>Wagner, F. M., Mollaret, C., Günther, T., Kemna, A., and Hauck, C. Quantitative imaging of water, ice, and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data. Geophysical Journal International, 219 (3):1866–1875, 2019. doi:10.1093/gji/ggz402.</p>

scholarly journals Resolution capacity of geophysical monitoring regarding permafrost degradation induced by hydrological processes

2016 ◽  
Author(s):  
Benjamin Mewes ◽  
Christin Hilbich ◽  
Reynald Delaloye ◽  
Christian Hauck
Keyword(s):  
Electrical Resistivity ◽  
Seismic Tomography ◽  
Field Data ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Phase Model ◽  
Permafrost Degradation ◽  
Resistivity Tomography ◽  
Refraction Seismic ◽  
Ice Content

Abstract. Geophysical methods are often used to characterise and monitor the subsurface composition of permafrost. The resolution capacity of standard methods, i.e. Electrical Resistivity Tomography and Refraction Seismic Tomography, depends hereby not only on static parameters such as measurement geometry, but also on the temporal variability in the contrast of the geophysical variables (electrical resistivity and P-wave velocity). Our study analyses the resolution capacity of Electrical Resistivity Tomography and Refraction Seismic Tomography for typical processes in the context of permafrost degradation using synthetic and field data sets of mountain permafrost terrain. In addition, we tested especially the resolution capacity of a petrophysically-based quantitative combination of both methods, the so-called 4-phase model, and by this analysed the expected changes in water and ice content upon permafrost thaw. The results from the synthetic data experiments suggest a higher sensitivity regarding increasing water content compared to decreased ice content, and potentially larger uncertainty for the individual geophysical methods than for the combined evaluation with the 4-phase model. In the latter, ground ice loss can be detected quite reliably, whereas artefacts occur in the case of increased horizontal or vertical water flow. Analysis of field data from a well-investigated rock glacier in the Swiss Alps successfully visualised the seasonal ice loss in summer, and the complex spatially variable ice-, water- and air content changes in an interannual comparison.

scholarly journals Geophysical Methods and their Applications in Dam Safety Monitoring

2020 ◽  
pp. 291-345
Author(s):  
Nasrat Adamo ◽  
Nadhir Al-Ansari ◽  
Varoujan Sissakian ◽  
Jan Laue ◽  
Sven Knutsson
Keyword(s):  
Electrical Resistivity ◽  
Early Stage ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Seepage Flow ◽  
Resistivity Tomography ◽  
Embankment Dams ◽  
Refraction Seismic ◽  
Dam Safety Monitoring ◽  
Selection Of

The use of geophysical methods in dam sites investigations and safety monitory has proved their good value and versatility in many earthfill dam sites as early as the 1920s. In the following years great development has occurred in the methods, application procedures and tools used. They may be considered today as good ways for carrying out observation tasks on existing dams in non-intrusive and much faster and cheaper ways than the traditional geotechnical methods. It is possible using them to discover anomalies in the dam body or its foundation at an early stage and allowing quick intervention repair works. These methods seek to register and present variations in the basic geotechnical material properties in dams such as; bulk density, moisture content, elasticity, mechanical properties of rocks, electrical resistivity and mineralogy and magnetic properties and so forth. Such variations can indicate increasing seepage flow, progression in cracks’ sizes, formation of voids, caverns and other instability manifestations. Depending on how any investigation is carried out and the targeted anomaly, there is now selection of these methods such as: Electromagnetic Profiling (EM), Electrical Resistivity Tomography (ERT), SelfPotential (SP), Ground Penetration Radar (GPR), variety of Seismic Methods (SM) which can be applied using such equipment as in Seismic refraction, Seismic Reflection, Multi Analysis of Rayleigh surface waves (MASW) instruments, or using Refraction Micrometer (ReMi), macro-gravity method, and Cross-Hole Seismic Tomography. In addition, Temperature Measurements and other less used methods can be used like Microgravity measurement, Magnetic Profiling and Radio Magnetotelluric methods. An attempt is made here to cover the details of these methods, their advantages and limitations and to prove their usefulness in many dam sites all over the world. One observed issue is their adaptability to embankment dams more than to concrete dams and their popularity for checking seepage related problems and material changes within dam bodies and their foundations such as formation of voids and sinkholes.

Geophysical data fusion by fuzzy logic for imaging the mechanical behaviour of mudslides

2007 ◽  
Vol 178 (2) ◽  
pp. 127-136 ◽  
Author(s):  
Gilles Grandjean ◽  
Jean-Philippe Malet ◽  
Adnand Bitri ◽  
Ombeline Méric
Keyword(s):  
Electrical Resistivity ◽  
Data Fusion ◽  
Cross Sections ◽  
Geophysical Methods ◽  
Geophysical Data ◽  
Physical Parameters ◽  
Seismic Velocities ◽  
S Wave ◽  
S Waves ◽  
Resistivity Data

Abstract Geophysical methods such as seismic surveying or electrical resistivity imaging appear to be well adapted to investigate landslide structure and understand related mechanisms. They allow direct and non-intrusive measurements of acoustic (P), shear (S) waves velocity and electrical resistivity, three physical parameters considered as essential to define the properties of reworked moving materials. Both methods were applied at the “Super-Sauze” site, in the French South Alps, where a typical example of an intra-material mudslide can be observed. Measurements were taken simultaneously along a profile of 325 m in length, perpendicularly to the axis of the mudslide. The P and S-wave velocity fields, as well as the electrical resistivity field, were inverted from recorded data according to suitable algorithms. P and S-wave velocities as well as resistivity tomographies are presented and discussed in term of reliability. Preliminary interpreted results show a correlation between the seismic velocities and electrical resistivity data, confirming that the simultaneous use of both methods gives complementary information on the geomechanical behaviour of the landslide. The seismic data provide information on the variations of fissure density and on the presence of deformed material whereas the electrical resistivity data provide information on the variations of water content within the mudslide. In order to go deeper into the interpretation of the geomechanical behaviour of the mudslide from geophysical data, a data fusion strategy based on fuzzy subsets theory is developed. The computed fuzzy cross-sections show the possibility of geomechanical hypotheses to be realized in specific areas of the tomographic cross-sections highlighting the places where plastic or solid-body deformations could occur. This information is consistent with the geotechnical data and the borehole inclinometer measurements available for the mudslide.

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