3D Geological Mapping Research Articles

Engineering geological and geotechnical evaluation of Sathya Sai Prasanthi Nilayam railway tunnel, Andhra Pradesh, India

Detailed engineering geological investigations were carried out for a railway tunnel which was constructed more than two decades ago. 3D engineering geological mapping was carried out using Brunton Compass and Total Station Surveying instruments in 1:100 scale. Coarse-grained pink and grey granite, hornblende-biotite gneiss and dolerite dyke of Archaean age and Lower Proterozoic age were mapped. Rock mass was intersected by sub-horizontal, inclined, and vertical joint sets, which were continuous and persistent, smooth, and planar with thick filling of decomposed and crushed sheared material or with thin coating of clay material. Based on the Q-system, rock mass was classified into different classes. On the basis of large-scale engineering geological mapping and Norwegian Method of Tunnelling, a support system was recommended which includes rock bolt, fibre reinforced shotcrete, grouting and reinforced ribs of sprayed concrete and the same is implemented by the agency. As per the best knowledge of the authors, reinforced ribs of sprayed concrete are first time used for transportation tunnels in India and it will be more effective if it will be compared with ISMB or Lattice Girder.

Integrating mining software, CAD, and GIS technologies for enhanced 3D geological mapping and visualization

This research provides a comprehensive overview of the methods and technologies applied for the mapping and visualization of three-dimensional (3D) mining and geological data, highlighting both mining-specific software and general-purpose engineering CAD and GIS tools. The study begins by addressing the challenges associated with the implementation of GIS-type spatial information systems within the mining industry, emphasizing their role in building robust information systems for mine technical departments. It then explores the application of spatial information systems in the environmental protection of mining and post-mining areas, where these technologies have found significant use. The final section delves into modern technologies for acquiring and visualizing spatial data, focusing on 3D data relevant to both surface and underground mining operations. The article underscores the growing importance of advanced visualization techniques in enhancing the accuracy and efficiency of mining operations and environmental management.

Structural setting of the Zoujiashan-Julong’an region, Xiangshan volcanic basin, China, interpreted from modern CSAMT data

The Zoujiashan-Julong’an area is situated on the western side of the Xiangshan volcanic basin. The basin represents the central part of the Jiangxi Province and it is well endowed with uranium deposits. Ongoing brownfield exploration requires a better understanding of the deep-seated geological structures of the region so as to discover additional, but concealed, deposits at depth. Aiming at elucidating the deep structural and geological framework, 14 parallel controlled-source audio-frequency magnetotelluric (CSAMT) survey lines were conducted to document the relationships between lithological contacts, faults and uranium mineralization with a penetration depth of about 2 kms. By integrating the interpreted geological profiles with geological surface maps and drilling data, a 3D geological model was constructed by using GOCAD software. The 3D model illustrated the major lithological units, faults and concealed uranium mineralization, respectively. The obtained data show that: (1) The Ehuling Formation as well as the underlying metamorphic basement displays a medium-to-high resistivity, whereas the Daguding Formation has a low-resistivity. The unconformity surface between volcanic rocks and the metamorphic basement is represented by a distinct low-resistivity zone which is locally intersected by faults. The fault structure in the CSAMT inversed sections appears as a low resistivity zone or a high-low resistivity variation gradient zone cutting through different interfaces. (2) As is documented by the 3D geological model, the favorable sites for uranium mineralization are distributed in the depressions of the metamorphic rock basement, at the boundary of volcanic rock formations, and in the transitional zones between the depressions and uplifts, where the thickness of the strata increases (or decreases) and the composite faults exist. (3) The location and spatial distribution of the unexposed structures delineated by the 2D resistivity inversion results are consistent with the geological mapping results. The delineated interface between porphyritic lava and rhyodacite is basically consistent with the drilling data. The CSAMT detection results can provide reliable deep geological structure information for 3D geological mapping and deep metallogenic prediction in Xiangshan area.

Virtual outcrop models: Digital techniques and an inventory of structural models from North-Northwest Iberia (Cantabrian Zone and Asturian Basin)

The first steps to study natural structures are data collection, their representation and their geological interpretation. There is no doubt that the development of digital techniques in recent times has facilitated these tasks. Here we present an inventory of virtual outcrop models from the Cantabrian Zone and Asturian Basin, North-Northwest Iberian Peninsula, and the procedure employed to obtain the data, construct the models and interpret them geologically. These models correspond to contractional folds and faults of Palaeozoic age, and to Mesozoic extensional structures affected by Cenozoic tectonic inversion in the form of folds and thrusts. The digital techniques and data employed are fieldwork, as well as Google Earth images, orthophotographs, stereoscopical pairs of photographs and virtual outcrop models, constructed using Structure from Motion photogrammetry based on images extracted from Google Earth or from photographs taken in the field using a tripod or unmanned aerial vehicles. The analysis of these models has provided us with geological information that would have been difficult to obtain using traditional techniques. Apart from their scientific interest, the examples shown may be helpful for structural geologists who wish to obtain 3D geological models, maps and sections, and additional structural information from field examples, as well as elements to prepare a virtual fieldtrip and/or for educational purposes.

LEONARDO DA VINCI’S AND NICOLAUS STENO’S GEOLOGY

Anniversaries for the two founding fathers of geology occurring in the same year prompted a comparative evaluation of how the two contributed to establishing the basic principles of the discipline. To do so, passages from their publications, codices and manuscripts have been quoted directly. The Stenonian principles (‘original horizontality’, ‘original continuity’, and ‘superposition of individual strata’) are present in Leonardo’s notebooks amazingly formulated, using similar wording when studying the same area more than 150 years earlier. Also, Stenonian priority in naming and explaining geological concepts and processes (e.g., faulting, folding, angular unconformity, relative chronology) are mirrored in Leonardo’s writings and pictorial works. While Steno enjoys priority in stepwise restoration of the geological history of a given region, Leonardo was the first to construct a 3D geological profile representation and geomorphologic maps. Lastly, the paper focuses on diverging stances of the two savants about the Noachian Deluge and the age of the Earth. Already 500 years ago, Leonardo had solved the question of marine fossil remains of organic origin found in the mountains implying the possibility of deep geologic time in a statement of ‘eternalism’. 350 years ago, Steno solved the same question in a different way in which he retained a basic role for the Deluge and assumed a short age for the Earth by focusing mainly on short-lived sedimentary and geomorphologic processes.

3D computer-assisted geological mapping: testing WinGeol's FaultTrace for semi-automatic structural geological assessment

3D computer-assisted geological mapping: testing WinGeol's FaultTrace for semi-automatic structural geological assessment

3D Computer-Assisted Geological Mapping: Testing WinGeol's FaultTrace for semi-automatic structural geological assessment

3D Computer-Assisted Geological Mapping: Testing WinGeol's FaultTrace for semi-automatic structural geological assessment

Geo-environmental monitoring and 3D finite elements stability analysis for site investigation of underground monuments. Horemheb tomb (KV57), Luxor, Egypt

The Valley of the Kings (KV) is a UNESCO world heritage site with more than thirty opened tombs. Since the first tombs were constructed, at least 24 historical flash flood events has been identified, each of which has been contributed to the destruction and deterioration of the tombs. Recently, most of these tombs have been damaged and inundated after 1994 flood. In order to understand the Geo-environmental impact mainly the past flash floods due to the intensive rainfall storm on the valley of kings and the long-term rock mass behavior under geostatic stresses in selected Horemheb tomb (KV57) and its impact on past failures and current stability, Remote sensing, GIS, LIDAR, 3D finite element stability analysis and rock mass quality assessments had been carried out using advanced methods and codes. Our work provides environmental satellite space views via landviewer Erath Observation System (EOS) Platform with passive and active sensors which include the Normalized Difference Vegetation Index (NDVI), Soil-Adjusted Vegetation Index (SAVI), Atmospherically resistant vegetation index (ARVI), Green Chlorophyll Index (GCI), Normalized Burn Ratio (NBR), Normalized Difference Snow Index (NDSI), Light Detection And Ranging (LIDAR) images, Terrain (DEM) Digital Elevation Models, 3D geological maps. In other hand experimental and numerical geotechnical evaluations and modeling of the rock mass of these underground structures and their surroundings have been executed. We estimated the rock mass quality of the different members within the Thebes limestone and Esna shale formations using the mechanical testing and Rock Mass Rating (RMR), rock quality system (Q-system) and Geological Strength Index (GSI) systems. Our recent analyses show that the KV57 rock- cut tomb at Luxor has been cut into poor to very poor quality marl shale masses due to the impact of flash foods. Rock failures of ceilings and pillars were frequently facilitated by local, unfavorably oriented persistent discontinuities, such as tension cracks and faults. Other failures were related to the disintegration of the marl limestone and Esna shale Formations into individual nodules upon weathering. Our data suggest that, in ancient Egypt monumental tomb construction, low-strength rock masses rarely resulted in modifications of the planned tomb design in order to minimise the risk of rock falls and to prevent collapses. The current flood protection measures are not enough. For this two following measures are proposed 1—to rise the current wall by 50 cm. 2—to fill the depression by reshaping bathymetry.

Two-dimensional inversion of CSAMT data and three-dimensional geological mapping for groundwater exploration in Tongkeng Area, Hunan Province, China

Controlled source audio-magnetotelluric (CSAMT) is an indirect and effective geophysical prospecting method in subsurface prospecting. Although CSAMT investigation tools are equipped with new techniques, it must be noted that the models obtained still do not automatically decipher the reality of groundwater in bedrock with very high resistivity contrasts. Our study proposed a new CSAMT data processing scheme, which combined the 2D modeling and 3D visualization for groundwater exploration in Tongkeng area, Hunan Province, China. To directly highlight exploitable groundwater, we used the open-source and the OCCAM2D inversion software, coupled with the geological information of the area to define the 3D imaging with emphasizing on the network of producing fractures. We deployed three CSAMT profiles with transverse magnetic (TM) mode recorded on 21 frequencies (8192 Hz to 8 Hz). The data were filtered, pre-processed and carefully analyzed from station to station. Analysis of the apparent resistivity and phase maps show the conductive zones (<150 Ωm) and resistive zones (> 500 Ωm) separated by transition zones (150 to 500 Ωm). The 2D models and stacked sections show discontinuities of fractures marked by two major faults and a main fracture in the zone interconnected by minor fractures. A 3D geological map was obtained from the result of the best models of the different lines. The ITER2DAT function was used to export the data from OCCAM2D inversion and then display it to array and depth channels data for each station. Geological and borehole ZK01 data were used to build pseudo stratigraphic drillholes based on the range of very low (<10 Ωm) to high values resistivity structures (>1500 Ωm). The 3D view shows stratigraphic discontinuity that is between carbonaceous formation and the metamorphic granites. The intruded Devonian limestone layer, which is the potential water tank, and the carbonate vein layer are constantly heated by the geothermal gradient of the area.

Unsupervised geochemical classification and automatic 3D mapping of the Bolshetroitskoe high-grade iron ore deposit (Belgorod Region, Russia)

We stated and solved three successive problems concerning automatization of geological mapping using the case of the Bolshetroitskoe high-grade iron ore deposit in weathered crust of Banded Iron Formation (Kursk Magnetic Anomaly, Belgorod Region, Russia). (1) Selecting a classification (clustering) method of geochemical data without reference sampling, i.e., solution of an “unsupervised clustering task”. We developed 5 rock classifications based on different principles, i.e., classification by visual description, by distribution of economic component (Fe2O3), by cluster analysis of raw data and centered log-ratio transformation of the raw data, and by artificial neural network (Kohonnen’s self-organized map). (2) Non-parametric comparison of quality of the classifications and revealing the best one. (3) Automatic 3D geological mapping in accordance with the best classification. The developed approach of automatic 3D geological mapping seems to be rather simple and plausible.

Rock Mass Characterization for the Underground Surge Pool Cavern – A Case Study, India

Abstract Underground surge pool cavern for the storage and lifting of water is being constructed in the part of Telangana State of India. For better rock mass characterization and support design, 3D engineering geological mapping was carried for the heading portion of the surge pool. 3D geologic mapping of heading portion is very important for large underground cavern to know about the cavern behavior during benching down. The direction of the longest axis of the cavern was finalized based on the in-situ hydrofracturing testing inside the deep borehole. The assessment of tunnel quality index ‘Q’ for the exposed granitic rock mass was done based on the information available of the rock joints and their nature, 3D geological mapping and in-situ stress measurement. Roof support and wall support pressure was estimatedbased on Q-values, and in this case applicable for the non-squeezing ground condition. For structural stability of crown and walls, rock support arrangement was recommended based on NMT technology and geological conditions of site, which includes steel fibre reinforced shotcrete, grouting, rock bolt and drainage hole provisions. The capacity of support system is determined to evaluate the efficacy of the proposed support system.

The application of audio magnetotelluric for 3D geological mapping in the Gobi Desert area

Constructing the strata and bedrocks beneath the overburden for three‐dimensional (3D) geological mapping in the Gobi Desert area is challenging but necessary. Rock resistivity is a key parameter to research the underground media. In the Gobi Desert area, the overburden has low resistivity, while the underlying strata and bedrocks have much higher resistivity in general. These features provide the basic conditions for distinguishing the rocks by their resistivities. The audio magnetotelluric (AMT) method is effective for investigating the electrical structure of most upper crust. Due to minor anthropogenic electromagnetic interference, good data can be easily acquired by reducing the ground resistance and by placing a remote reference station in the Gobi Desert area. WAL analysis and phase tensor method, derived from impedance tensors, can indicate the dimension of a structure, which in turn suggests whether a two‐dimensional or 3D inversion needs to be used. The resistivity distribution obtained via inversion can be translated to lithological units associated with rock resistivity measurement. Combined with borehole constraint, the strata and bedrocks beneath the overburden could be explicitly described. By application of AMT, the Quaternary and Tertiary strata could be divided in the Barkol Basin by a low‐resistivity layer, which was attributed to saturation with salty water. The Eocene and Jurassic strata were distinguished in the Hami Basin by 10‐ and 50‐Ωm contour lines, respectively. In both areas, high‐resistivity bedrocks were clearly depicted.

3D Reservoir Modeling Based on Mobile Platform and OpenGL ES

This paper discusses 3D petroleum reservoir modeling based on android platform and development of relavite graphical software system for reservoir models on the mobile terminal. Using OpenGL ES graphical library to perform graphics processing and realize 3D rendering of the mobile reservoir models. Making use of the Kriging algorithm and Choleskly method to accomplish the interpolation calculation, it is the core of all grid vertexes algorithm and cutting operation for the reservoir models. On the basis of 3D reservoir modeling, complete several 3D reservoir geological model maps, and a serial of functional maps such as rotation, translation, scaling and grid displays, peeling, axis slicing, arbitrary slicing, well connected section, etc. The software system successfully passed the tests of some oil field data. The 3D reservoir modeling based on mobile platform enables the professional persons to analyse the reservoir distribution and direct the oil well drilling feasibly and easily, which will bring great convenience for technical exchanges of oil and gas exploration.

3D geological map modeling technology based on a geological route and geological object wireframe model

3D geological map modeling technology based on a geological route and geological object wireframe model

Remote geological mapping using 3D photogrammetry: an example from Karrat, West Greenland

The geology of the Paleoproterozoic Karrat Group in West Greenland (71°–74°50´N) was investigated during the field seasons 2015–2017, using a combination of digital photogrammetry and traditional field work in a collaboration between the Geological Survey of Denmark and Greenland and the Ministry of Minerals Resources of Greenland. The area is characterised by steep alpine terrain with more than 2000 m of relief that in many places is completely inaccessible, which makes field work extremely difficult. Therefore 3D mapping using digital photogrammetry is an invaluable tool in the investigation of the region. Early geological investigations of the area involved the first use of photogrammetry in Greenland (Henderson &amp; Pulvertaft 1987). This contribution serves as an example of the present-day use of photogrammetry in geological interpretation, following the workflow outlined in Sørensen &amp; Dueholm (2018). During the last three years, more than 50 000 stereo images have been collected using handheld, calibrated digital cameras while conducting field work in the area (Rosa et al. 2016, 2017, 2018). The images, which cover large parts of the steep cliff sections in which the geology is superbly exposed, are essential to the ongoing revision of the geological map sheets covering the area. Here we present a small subset of the data from the island of Karrat (Fig. 1), showcasing the potential of 3D geological mapping in Greenland as well as presenting new insights into the geology of the Karrat Group.

A methodology for 3D geological mapping and implementation

Using 3D visualization models to exhibit geological structure has become a trend in geological studies. Compared to 2D geological mapping, 3D geological mapping is dependent on more geological sampling information. Geophysical methods (e.g., gravity, seismic, and electric) thus become the major tools in 3D geological mapping. In traditional works, people must extract the geological information from various data grids acquired through different geophysical methods and subsequently integrate the information to manually construct a 3D geological model. This approach usually causes inconvenience and inefficiencies in practice. Therefore, we propose a methodology of 3D geological mapping. It first constructs visualization models from different geophysical data grids and subsequently integrates these models for interpretation and finally converts to a 3D geological model. Based on this methodology, we implement the corresponding system which can accomplish the above process automatically. As an example, we gave a detail description for constructing the 3D lithological model by the methodology mentioned above with the geological survey data acquired in the western Jungger, Xinjiang of China. The demonstration show us that the methodology can effectively solve the matter of 3D geological modeling in case of enriched in geophysical data but in lack of sufficient geological sampling information.

Hypertension artérielle du sujet noir

Controlled source audio-magnetotelluric (CSAMT) is an indirect and effective geophysical prospecting method in subsurface prospecting. Although CSAMT investigation tools are equipped with new techniques, it must be noted that the models obtained still do not automatically decipher the reality of groundwater in bedrock with very high resistivity contrasts. Our study proposed a new CSAMT data processing scheme, which combined the 2D modeling and 3D visualization for groundwater exploration in Tongkeng area, Hunan Province, China. To directly highlight exploitable groundwater, we used the open-source and the OCCAM2D inversion software, coupled with the geological information of the area to define the 3D imaging with emphasizing on the network of producing fractures. We deployed three CSAMT profiles with transverse magnetic (TM) mode recorded on 21 frequencies (8192 Hz to 8 Hz). The data were filtered, pre-processed and carefully analyzed from station to station. Analysis of the apparent resistivity and phase maps show the conductive zones (<150 Ωm) and resistive zones (> 500 Ωm) separated by transition zones (150 to 500 Ωm). The 2D models and stacked sections show discontinuities of fractures marked by two major faults and a main fracture in the zone interconnected by minor fractures. A 3D geological map was obtained from the result of the best models of the different lines. The ITER2DAT function was used to export the data from OCCAM2D inversion and then display it to array and depth channels data for each station. Geological and borehole ZK01 data were used to build pseudo stratigraphic drillholes based on the range of very low (<10 Ωm) to high values resistivity structures (>1500 Ωm). The 3D view shows stratigraphic discontinuity that is between carbonaceous formation and the metamorphic granites. The intruded Devonian limestone layer, which is the potential water tank, and the carbonate vein layer are constantly heated by the geothermal gradient of the area.

Approach of automatic 3D geological mapping: the case of the Kovdor phoscorite-carbonatite complex, NW Russia

We have developed an approach for automatic 3D geological mapping based on conversion of chemical composition of rocks to mineral composition by logical computation. It allows to calculate mineral composition based on bulk rock chemistry, interpolate the mineral composition in the same way as chemical composition, and, finally, build a 3D geological model. The approach was developed for the Kovdor phoscorite-carbonatite complex containing the Kovdor baddeleyite-apatite-magnetite deposit. We used 4 bulk rock chemistry analyses – Femagn, P2O5, CO2 and SiO2. We used four techniques for prediction of rock types – calculation of normative mineral compositions (norms), multiple regression, artificial neural network and developed by logical evaluation. The two latter became the best. As a result, we distinguished 14 types of phoscorites (forsterite-apatite-magnetite-carbonate rock), carbonatite and host rocks. The results show good convergence with our petrographical studies of the deposit, and recent manually built maps. The proposed approach can be used as a tool of a deposit genesis reconstruction and preliminary geometallurgical modelling.

Large scale magnetotelluric sounding at the periphery of the Songliao Basin, NE China

Recently, China Geological Survey (CGS) has launched 3D geological mapping programs from regional to local scales. The project Deep geological survey at the periphery of the Songliao Basin funded by CGS was implemented from 2012 to 2014. Its main goals are to reveal the tectonic framework of the Jarud Basin (JB) as well as to identify the strata distribution of Permian Linxi Formation by integrating new electromagnetic data with existing geophysical and geological data since black mudstones in the Linxi Formation have shown the potential of shale gas. The study area is situated in Jarud Banner and Ar Horqin Banner, Inner Mongolia, China. It is covered dominantly with Cretaceous-Jurassic igneous rocks with exception of the small southeastern part. It is tectonically located in the southern Great Khingan Range, western margin of the Songliao Basin, north of Xar Moron Fault. Over years of 2012 to 2014, a magnetotelluric survey was carried out at the west of the Songliao Basin. A total of 1559 stations including existing MT data on eight NW and five NE profiles were obtained, covering area that exceeds 10,000 km2. After dimensionality analysis and static shift removal, the nonlinear conjugate algorithm was used to conduct 2D inversion for TM and TE modes. Inversion results revealed numerous large faults, some of which constitute the boundaries of the Jarud Basin, and modified the tectonic framework. Integrated with well logging and geological data, two Paleozoic fault depressions (Gadasu and Hunnitu) and one Mesozoic depression was discovered. Two Paleozoic sag were inferred to be presence of Linxi Fms. One Mesozoic sag was inferred to be hydrocarbon potential. Attention should be paid to Gadasu sag with area of around 500 km2 since it contains reasonably thick conductive sediments exceeding 4 km in depth which might be black mudstones pertaining to shale gas.

Improved Structural Mapping and Conductive Targeting Delivered by a new 2.5D AEM Inversion Solver

The advantages of 2.5D (2D geology, 3D source) airborne electromagnetic inversion in 3D geological mapping applications and the identification of conductive drilling targets compared to the more commonly used CDI transforms or simple 1D inversions are demonstrated using examples from different geological settings.The 2.5D inversion application used in this work and described in Silic et al, 2015 is a substantially changed version of ArjunAir, Wilson et al., 2006, a product of CSIRO/AMIRA project P223F. The changes include a new forward model algorithm and a new inversion solver. The application enables the accurate simulation of 3D source excitation for full domain models inclusive of topography, non-conforming boundaries and very high resistivity contrasts. Solution is accurate for a geoelectrical cross-section which is relatively constant along a strike length that exceeds the AEM system footprint.The major innovation includes a new inversion solver with adaptive regularisation which allows the incorporation of a misfit to the reference model and the model smoothness function. The regularisation parameter is chosen automatically and changed adaptively at each iteration, as the model, the sensitivity and the roughness matrices are changing, Silic et al, 2015.Memory usage has been dramatically reduced and provides a usage estimate prior to execution. For speed the software has been parallelised using Intel MPI and can be used on standard computing hardware or computing clusters. Data from survey lines with lengths exceeding 30 kilometres can be inverted on high end laptop computers. The integrated software design allows the user to prepare a full survey inversion then execute this simply in a batch process. The user can visualise inversion progress at any time during process execution.We allow flexibility in the selection of components and in the estimation of noise. A non-specialist can obtain a high value result from our 2.5D AEM inversion in terms of it achieving a more realistic geological section.We show inversion examples from groundwater, minerals (VMS) and geological mapping AEM surveys projects and compare the results with known geology and drilling. We demonstrate the much improved mapping and target definition delivered by this inversion method when compared with the other more common transforms or inversion methods used on these projects.