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Colegial-Gutiérrez, Juan Diego, María Camila Forero-Quintero, María Alejandra Fuentes-Rueda, and Sully Gomez Isidro. "Characterization of weathering profiles of the crystal rocks of eastern Bucaramanga and definition of hydrogeological properties." Boletín de Ciencias de la Tierra, no. 41 (January 1, 2017): 16–30. http://dx.doi.org/10.15446/rbct.n41.59347.
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In the process of improving the knowledge of the hydrogeological potential of weathered zones in crystalline rocks and compounds that can behave as aquifers, this article is performed whose area of study is located east of the metropolitan area of Bucaramanga, Santander Massif consists of two main lithological units; the Neis of Bucaramanga and Santander Group plutonic (diorite, granodiorite-tonalite gray quartz monzonite and monzogranite). These rocks have undergone brittle deformation, physico-chemical weathering mainly influenced by the tropical atmosphere of the area also are jointed and fractured creating conditions that facilitate the flow of water and in turn be optimized weathering processes in the region. He appealed to the identification and location of field weathering profiles made a detailed study of outcrops, presenting a thickness of 90.4 m for the profile of the Gneisic rock weathering and 68.5 m for the profile of granodiorite rock, made up 6 steps weathering of which samples each were taken and carry out macroscopic analysis, petrographic and geochemical using thin films, determining the percentage of porosity, humidity, dry unit weight, X-ray fluorescence, electron microscopy Sweeping and Grading; base characterizing weathering profiles and properties, highlighting the potential hydrogeological found in the Range II: Slightly weathered rock and interval V: Completely weathered rock profile of granodiorite rock and Rock Gneisic profile, the interval III : Moderately weathered rock and the range V: Completely weathered rock, since these stages of weathering, moisture peaks present, regular micro fractures and high porosities.
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Hasan, Muhammad, Yanjun Shang, Weijun Jin, and Gulraiz Akhter. "Assessment of Aquifer Vulnerability Using Integrated Geophysical Approach in Weathered Terrains of South China." Open Geosciences 11, no. 1 (December 31, 2019): 1129–50. http://dx.doi.org/10.1515/geo-2019-0087.
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Abstract Despite being rich in groundwater resources, assessment of hard-rock aquifers in many areas of Asia is difficult given their strong heterogeneity. However, delineation of such aquifers is essential for estimation of the groundwater reserves. In addition, the vulnerability of hard-rock aquifers is controlled by the weathered/fractured zones because it is the place where most of the groundwater reserves are contained. In this work, an integrated approach of the electrical resistivity tomography (ERT), high precision magnetic, X-ray Diffraction (XRD), physicochemical analysis and pumping test data was performed to investigate the hard-rock aquifers occurring in the weathered terrains. This approach reveals seven fractures/faults (F1 to F7) and four discrete layers such as the topsoil cover, highly weathered, partly weathered and unweathered rock. The groundwater resources are estimated as a function of different parameters i.e., aquifer resistivity (ρo), transverse unit resistance (Tr), hydraulic conductivity (K), transmissivity (T), rock formation factor (F) and rock porosity (Φ). These parameters divide the groundwater resources into four aquifer potential zones with specific ranges of ρo, Tr, K, T, F and Φ i.e., high, medium, poor, and negligible potential aquifers. The results suggest that the high potential aquifer reserves are contained within the weathered/fractured and fault zones. The X-ray diffraction (XRD) technique analyzes quartz as the major mineral (>50%). The physicochemical and geophysical analysis suggests good groundwater quality in the investigated area. The integrated results are highly satisfied with the available borehole information. This integrated geophysical approach for the estimation of groundwater resources is not only applicable in the weathered terrains of South China, but also in many other areas of the weathered/fractured aquifer in Asia and beyond.
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Salami, A. S., and E. M. Babafemi. "Delineation of Near-Surface Structural Features Suitable for Groundwater Accommodation Using 1-D and 2-D Resistivity Methods in Igarra, Akoko-Edo, Southwestern Nigeria." Journal of Applied Sciences and Environmental Management 24, no. 7 (August 7, 2020): 1209–15. http://dx.doi.org/10.4314/jasem.v24i7.13.
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Electrical resistivity methods using dipole-dipole and Schlumberger configurations of Vertical Electrical Sounding (VES) were carried out to evaluate the near-surface structural and lithological features suitable for groundwater development in parts of Igarra, Southwestern Nigeria. Two profiles with lengths of greater than 350m were carried out. A total of fifteen sounding locations along the profile lines were occupied. Dipole-dipole data were interpreted using DiprofWin software while interpretation of the VES data followed two stages of qualitative and quantitative data interpretation using Resist software. Dipole-dipole interpretation results indicate the occurrence of local fractures while VES interpretation results reveal the typical basement rock profile ranging from topsoil, lateritic sand, weathered front, fractured to fresh basement. The significant variations in terms of persistence and thicknesses of these basement vertical rock profiles were revealed by the geoelectrical correlation panels, which indicate typical basement inhomogeneities over short distances. The local structural domains, the weathered front (where thick) and the fractured basement are demonstrably potential sources of groundwater, at least for domestic and small scale enterprises in this part of Igarra.
Keywords: 2-D Pseudosection, Dipole-dipole, Fracture Basement, Vertical Electrical Sounding
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Mahi, Shuaibu, Abubakar Yusuf, and Garba Lawal. "Geoelectrical Assessment of Groundwater Potential within Zamfara and its Environs, Northwestern Nigeria." Caliphate Journal of Science and Technology 4, no. 1 (February 10, 2022): 54–70. http://dx.doi.org/10.4314/cajost.v4i1.8.
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Groundwater potential assessment was carried out within Zamfara environs, Northwestern Nigeria using geoelectrical technique with a view of solving the problem of incessant failure of boreholes in the study area. A total of one hundred and eighty-three (183) vertical electrical soundings (VES) were used to identify potential groundwater bearing zones capable of sustaining economic development of the study area. Two hydrogeological units were investigated (basement rock units and sedimentary rock unit), using Omega resistivity meter Model No. 122, to measure and record the resistance of the subsurface by Schlumberger configuration. The data obtained were interpreted quantitatively and qualitatively using the partial curve matching and computer iteration techniques to generate the first order geoelectric parameters. Generally, the VES result from the basement rock units revealed, four geoelectric layers which correspond to lateritic top soil, weathered basement (clay), partially fractured layer/fractured layer and fresh basement. The weathered/fractured layer was identified as the water bearing layer, within the basement rock units of the study area. From geospatial analysis of both weathered thickness/fracture thickness layers, South and Northeastern part tends to be the most prospective area with the best hydrogeologic conditions for borehole siting within the basement rock units. Consequently, three geo-electric layers were delineated from VES result obtained from Gundumi formation, which correspond to sandy clayey top/gravelly sandy top soil, second layer are mostly silty-clay/compacted sandstone/sandy gravel layers, the third layer were majorly saturated sandstone in some instances silty clay. However, the aquiferous layer is saturated sandstone/sandy gravel layer. The Dar Zarrouk result revealed excellent groundwater potential within the Gundumi formation. The values of coefficient anisotropy obtained from Gundumi rock units range from 0.44 to 3.79, which implies moderate saturation of groundwater. This is an indication that the aquifers of the Gundumi formation is more promising and it can be tap for both domestic and agricultural uses.
Keywords: Vertical electrical sounding; Fractured layer; Saturated Sandstone; Basement rock units; Gundumi formation
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Briški, Maja, Andrej Stroj, Ivan Kosović, and Staša Borović. "Characterization of Aquifers in Metamorphic Rocks by Combined Use of Electrical Resistivity Tomography and Monitoring of Spring Hydrodynamics." Geosciences 10, no. 4 (April 10, 2020): 137. http://dx.doi.org/10.3390/geosciences10040137.
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Crystalline rocks are generally characterized by negligible porosity and permeability in terms of groundwater exploitability. However, alteration processes can greatly increase their fracture permeability and induce formation of modest, but locally important aquifers. Therefore, subsurface characteristics of alteration zones are of major importance for hydrogeological evaluation of crystalline terrains. Alteration processes greatly affect rock total porosity and water content, causing contrasting electrical resistivity of rocks affected by varying degrees of weathering. This makes electrical resistivity tomography (ERT) a preferable geophysical method for the exploration of alteration zones in crystalline rocks. In our research, we used an integrated approach, combining the ERT method with monitoring of spring discharge and hydrochemistry to characterize metamorphic aquifers on slopes of the Medvednica Mountain (Croatia). Significant fracture flow aquifers are found to be formed in intensely fractured but not highly weathered rock masses (medium to high resistivity values), while highly weathered masses (low resistivity values) form local barriers for fracture flows. Subsurface structure of the alteration zone proved to be highly irregular, with sharp contacts between more and less weathered rocks. Decrease of permeability below the alteration zone keeps the water level near the surface and enables spring occurrence on the mountain slopes. Studied aquifers have relatively limited extent, resulting in typical capacity of major springs of a few l/s. More frequent but less productive springs are attributed to the draining of the shallow part of the alteration zone (mostly saprolite). Combination of the ERT method with spring monitoring proved to be very effective as a first and relatively inexpensive methodology for hydrogeological characterization of crystalline terrains, both in local and catchment scales.
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Thi Luan, Bui, and Lieu Kim Phuong. "Petrographic characterization and petroleum potential of Mesozoic carbonate rock in Block 106, Northern Red river basin." Science and Technology Development Journal - Natural Sciences 2, no. 6 (January 26, 2020): 146–64. http://dx.doi.org/10.32508/stdjns.v2i6.876.
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Petroleum exploration and exploitation in Red River basin has been carried since the early 1960s of the 20th century, however until now its effectiveness has been still limited. Recently, the oil price is constantly changing so the efficiency of petroleum exploration and exploitation is particularly considered. Therefore, the assessment of petroleum potential and the direction of exploration are not only scientific research but also economic problem for developing countries in which there is Vietnam. The article considers that characteristic of carbonate petrography is along with intergration of interpreted seismic –stratigraphy and well logs, geochemistry analytic results of source rocks and related literatures as well. The purpose is to predict the petroleum potential of carbonate rock in block 106 and serve effectively in Petroleum exploration and exploitation in Red River basin Based on the analytic results, carbonate rock in the study area was impacted by tectonic activities such as mechanic compaction; dissolution forming fractures, stylolites; and post-depositional processes as recrystallization of minerals, creating vuggy, mouldic and intraparticle pores and dolomitization as well. Carbonate rock contains fossils as foraminifera, coral, algae, echinoderm with subordinate brachiopod, bryozoa. Most of them are mudstone, wackestone with mud-supported and packstone is made up of abundant fossils. Locally, carbonate rock was fractured and filled up by calcite and silic. Oil and gas traces have been discovered in Mesozoic carbonate rock, block 106, northern Red River basin. Fractured carbonate rock and weathered carbonate rock in the structures as A, C and E are oil fields. Oil migrates into traps that were early formed in fractured carbonate basement rock masses that were buried in pre-Kainozoi.
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Chang, Seeun, Wooyong Um, Won-Seok Kim, and HyunJu Kim. "Effect of seawater intrusion on radioactive strontium (90Sr) sorption and transport at nuclear power plants." Radiochimica Acta 106, no. 2 (January 26, 2018): 147–60. http://dx.doi.org/10.1515/ract-2016-2724.
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Abstract Batch sorption and column experiments were conducted to investigate and compare sorption and transport behavior of 90Sr on the assumption of seawater intrusion at nuclear power plants. Batch sorption experiments were carried out on fractured rocks and bedrocks using synthetic groundwater and seawater both spiked with 90Sr. In general, higher 90Sr sorption occurred on fractured rock samples than on bedrocks, because of the presence of weathered secondary minerals (iron oxide and clay) on fractured rock surfaces. However, one particular bedrock sample (WSP-B) which has higher porosity and carbon amount than fractured rock samples also showed the higher 90Sr sorption than its comparable fractured rocks. For all batch sorption studies, 90Sr sorption distribution coefficient, Kd decreased from groundwater to seawater environment due to the higher ionic strength of seawater (6.4×10−1–7.7×10−1 M) compared to groundwater (4.0×10−3–6.0×10−3 M). The three different ionic strength solutions were used in column experiments, and the results showed that transport behavior of Sr through a fractured rock had similar sorption trend to batch sorption results. The highest mobility (or least retardation) for Sr was found for 100% seawater solution compared to the highest retardation (or least mobility) for 100% groundwater solution. These sorption and transport data of Sr on solid materials contacted with various ionic strength solutions corroborate empirically defensible information for assessment of radioactive contamination in groundwater below the NPP sites located nearby shores. In addition, the experimental data will be incorporated to improve transport models of 90Sr in the subsurface environment for severe nuclear accidents.
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Zhang, Qian, Shu Cai Li, Li Ping Li, and Qian Qing Zhang. "Experimental Study on Creep of Highly-Weathered Breccia." Applied Mechanics and Materials 477-478 (December 2013): 588–91. http://dx.doi.org/10.4028/www.scientific.net/amm.477-478.588.
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Mechanical property of rock is the main research object of rock mechanics. In order to further learn the rheological characteristics of soft fractured rock mass, the creep test of highly-weathered breccia with different water content of 0.65%, 1.88%, 4.03% using low-intensity uniaxial creepmeter developed by Shandong University is processed, and the strain-time curves under different water conditions and the corresponding variation of creep curves with different stress levels and moisture states are obtained. The experimental results show that the higher water content is, the larger creep deformation is and the longer time of creep deformation reaching stable is, in other words, the influence of water content on the rheological characteristics of rock mass is also significant. Finally, the conclusion that softening critical load (long-term strength) and softening critical depth of soft rock are greatly reduced due to the effect of water on rock structure and mechanical parameters is obtained to provide the fundamental reference for the follow-up tests and similar engineering.
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Vafidis, A., A. Andronikidis, H. Hamdan, G. Kritikakis, N. Economou, G. Panagopoulos, S. Zanettidis, et al. "Rock characterization for the foundation of two water reservoirs using geophysical and borehole data." Bulletin of the Geological Society of Greece 47, no. 3 (December 21, 2016): 1345. http://dx.doi.org/10.12681/bgsg.10919.
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In this work, we present the results of a geophysical survey at Malia, Crete, Greece. This survey combines VES, electrical tomography and seismic refraction at two sites where equal number of water reservoirs is planned to be constructed for the needs of a hybrid power station using wind-hydro pumping renewable energy. The geophysical sections are interpreted using geological and borehole data. This survey determines the thickness of the overburden, defines the quality of the carbonate bedrock, detects faults and weathered zones in carbonates. One major very low resistivity anomaly was detected at the northern investigated area, which corresponds to completely fractured or weathered limestone, while a 25m deep fracture zone, was detected at the southern investigated area.
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OLICHWER, Tomasz. "HYDROGEOLOGICAL CHARACTERIZATION OF LOCAL GROUNDWATER RESERVOIRS IN THE KŁODZKO LAND (SUDETES - SW POLAND) BASED ON AN ANALYSIS OF THE DISCHARGES OF SPRINGS." Carpathian Journal of Earth and Environmental Sciences 18, no. 1 (February 7, 2023): 171–82. http://dx.doi.org/10.26471/cjees/2023/018/249.
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The hydrogeological characteristics of the two types of local groundwater reservoirs found in the Kłodzko Land (Sudetes) have been made based on the analysis of the discharge of springs in Szczytna and Różanka. In the first of these spring discharge points, water flows out of Upper Cretaceous sandstones and mudstones. The other spring is associated with fractured and weathered mica schists and gneisses. The Różanka spring characterized by greater discharge variability than the fissured porous outflow in Szczytna. The latter one, due to the slower rate of water filtration in the rock medium, belongs to stable springs in terms of discharge. The local groundwater reservoir located in sedimentary rocks characterized by a much higher value of the groundwater volume stored (264,000 m3) than the reservoir consisting of weathered and fractured crystalline rocks (1,918 m3). In the case of the reservoir draining by Szczytna spring, the rate of groundwater exchange in the active zones is about 66 weeks. A distinctly shorter time (12 weeks) is necessary to exchange water in the fractured crystalline bedrock. The hydraulic conductivity for the aquifers in Szczytna and Różanka, calculated based on the recession coefficient, differ substantially from each other. They are 4.64 and 24.9 m/d, respectively.
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McKOWN, A. F. "Perimeter Control Blasting for Underground Excavations in Fractured and Weathered Rock." Environmental & Engineering Geoscience xxiii, no. 4 (November 1, 1986): 461–78. http://dx.doi.org/10.2113/gseegeosci.xxiii.4.461.
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Afolabi, O., B. M. Salami, T. M. Olapade, and O. A. Alao. "Geophysical and geotechnical investigations of the site of a collapsed two-storey building in Modomo, Ile-Ife, Southwestern Nigeria." Ife Journal of Science 25, no. 3 (January 7, 2024): 471–82. http://dx.doi.org/10.4314/ijs.v25i3.11.
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Geophysical and the geotechnical methods were used to study the site of a collapsed two-storey building in orderto determine the sequence and competence of the subsurface layers and determine the cause of the collapse of the building. The geophysical method employed the electrical resistivity method involving one dimensional (1D) Vertical Electrical Sounding (VES) and the two dimensional (2D) imaging techniques. Three VES stations were occupied using Schlumberger electrode configuration. 2D imaging data were acquired along four traverses using dipole-dipole electrode configuration. The geotechnical method involved Cone Penetration Test (CPT). CPT data was acquired at two points with the aid of 2.5 ton Dutch CPT machine. The results showed four subsurface layers based on the 1D VES results and 2D imaging results namely: topsoil, weathered layer, fractured basement rock and fresh basement rock. The topsoil resistivity varied from 116 Ωm to 191 Ωm and has thickness of about 1.5 m. It was classified as moderately competent. The second layer is weathered rock with resistivity varying between 92 Ωm and 327 Ωm and of about 8 m to 13 m thickness. This layer is also moderately competent. The third layer is fractured basement rock. It underlies the weathered rock and have resistivity varying from 391 Ωm to 405 Ωm. Its thickness varied from about 2 m to 20 m. This layer is competent. The fourth layer is the fresh basement rock having resistivity varying from 1365 Ωm to 12348 Ωm and is highly competent. The subsurface materials in the area are competent and can sustain the foundation of the building. Hence, the study concluded that the building collapse did not result from incompetent subsurface materials. Factors other than incompetent subsoil material that is human factors are believed to be responsible. This study has demonstrated the effectiveness of geophysical and geotechnical investigations in determining the competence of subsurface materials at engineering sites.
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Ajayi, O., K. A. Adekoya, O. P. Egwuatu, and C. I. Konwea. "GEOTECHNICAL INVESTIGATION OF THE PROPOSED IFE DAM SITE AT KAJOLA VILLAGE, ILE-IFE, SOUTHWESTERN NIGERIA." GEOLOGICAL BEHAVIOR 5, no. 2 (December 4, 2021): 28–33. http://dx.doi.org/10.26480/gbr.02.2021.28.33.
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Geological and geophysical investigations were conducted to assess the competence and structural integrity of the foundation site of the proposed Ife-dam at Kajola Village, Ile-Ife, Southwestern Nigeria. Geological investigation along the two (2) proposed dam axes revealed that the overburden material is loose to dense with angular shearing resistance (ɸ) of 27o to 41o. The soils are predominantly elastic silts; cohesive with considerable strength and stability. Geophysical investigation involving the Schlumberger Vertical Electrical Sounding delineated four (4) lithologies namely: topsoil with resistivity of 69 – 558 Ωm and thickness between 1.5 and 4.0 m; weathered sandy layer with resistivity from 123 – 586 Ωm and thickness between 6.5 and 20.4 m; partially weathered/ fractured basement with resistivity from 60 – 220 Ωm and thickness between 6.5 and 14.0 m; and the fresh basement rock with resistivity from 1337 – 10683 Ωm. There are indications of fractures at a depth of 32 m beneath Axis B extending to Axis A at a depth of 35 m. The subsurface materials are suitable to host a dam. Axis B is more appropriate for the dam axis, although the fracture zone should be factored into the design of the dam to prevent water seepage.
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Steelman, Colby M., Celia S. Kennedy, Donovan C. Capes, and Beth L. Parker. "Electrical resistivity dynamics beneath a fractured sedimentary bedrock riverbed in response to temperature and groundwater–surface water exchange." Hydrology and Earth System Sciences 21, no. 6 (June 29, 2017): 3105–23. http://dx.doi.org/10.5194/hess-21-3105-2017.
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Abstract. Bedrock rivers occur where surface water flows along an exposed rock surface. Fractured sedimentary bedrock can exhibit variable groundwater residence times, anisotropic flow paths, and heterogeneity, along with diffusive exchange between fractures and rock matrix. These properties of the rock will affect thermal transients in the riverbed and groundwater–surface water exchange. In this study, surface electrical methods were used as a non-invasive technique to assess the scale and temporal variability of riverbed temperature and groundwater–surface water interaction beneath a sedimentary bedrock riverbed. Conditions were monitored at a semi-daily to semi-weekly interval over a full annual period that included a seasonal freeze–thaw cycle. Surface electromagnetic induction (EMI) and electrical resistivity tomography (ERT) methods captured conditions beneath the riverbed along a pool–riffle sequence of the Eramosa River in Canada. Geophysical datasets were accompanied by continuous measurements of aqueous specific conductance, temperature, and river stage. Time-lapse vertical temperature trolling within a lined borehole adjacent to the river revealed active groundwater flow zones along fracture networks within the upper 10 m of rock. EMI measurements collected during cooler high-flow and warmer low-flow periods identified a spatiotemporal riverbed response that was largely dependent upon riverbed morphology and seasonal groundwater temperature. Time-lapse ERT profiles across the pool and riffle sequence identified seasonal transients within the upper 2 and 3 m of rock, respectively, with spatial variations controlled by riverbed morphology (pool versus riffle) and dominant surficial rock properties (competent versus weathered rock rubble surface). While the pool and riffle both exhibited a dynamic resistivity through seasonal cooling and warming cycles, conditions beneath the pool were more variable, largely due to the formation of river ice during the winter season. We show that surface electrical resistivity methods have the capacity to detect and resolve electrical resistivity transience beneath a fractured bedrock riverbed in response to porewater temperature and specific conductance fluctuations over a complete annual cycle.
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Roslee, Rodeano. "GEOLOGICAL ASSISTED ON WATER RESOURCES PLANNING IN MOUNTAINOUS CATCHMENTS IN KUNDASANG, SABAH, MALAYSIA." Malaysian Journal of Geosciences 4, no. 1 (February 28, 2020): 26–31. http://dx.doi.org/10.26480/mjg.01.2020.26.31.
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Based on geological mapping and geohydrologic data, water resources planning in mountainous catchment areas in Kundasang are outlined. The area is underlain by thick Paleogene clastic sediment and old Quaternary gravels. These rock units are carved by numerous lineaments with complex structural styles developed during series of regional Tertiary tectonic activities. The tectonic complexities reduced the physical and mechanical properties of the rock units and produced intensive displacements and discontinuities among the strata, resulting in high degree of weathering process and instability. The weathered materials are unstable and may cause subsidence and sliding induced by high pore pressure subjected by both shallow and deep hydrodynamic processes. Evaluation of 60 boreholes data in the study area reveals that the depth of the groundwater table ranges from 1.90 m (6 feet) to 11.20 m (35 feet) deep. The groundwater level in the study area fluctuates even within a short period of any instability of climatic change. The Quaternary sand and gravel layers with variable thickness defined the major shallow aquifers within the underlying weathered materials while the highly fractured sedimentary rocks defined the major deep aquifers. Most of the aquifers within the top unconsolidated weathered clastic material are under unconfined condition. The sedimentary formations are coarse-grained clastic materials generally contain fractured porosity and exhibit higher permeability. However, below subsurface, much of the groundwater is partially confined. Movements of groundwater are sufficiently restricted area to cause slightly different in head depth zones during periods of heavy pumping. During periods of less draught, the various groundwater levels will be recovered to their respective original level. This condition resulted from discontinuous nature of sediments where zones of permeable sand and gravel are layered between less permeable beds of silt and clay. Aquifer characterization and geological data are given to assist the local agencies on the water resources planning of the study area.
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Konstantopoulou, G., and I. Vacondios. "Engineering geological map of the urban area of Kastoria, NW Greece." Bulletin of the Geological Society of Greece 40, no. 4 (January 1, 2007): 1664. http://dx.doi.org/10.12681/bgsg.17070.
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In the present work, the engineering geological conditions of the urban area of Kastoria were examined. More specifically a geotechnical assessment of subsoil and rock outcrops within a minimum depth of 20 m bellow surface is made, for urban planning purposes. Landslide potential of the studied area including mainly rock falls and ground subsidence was also evaluated. Eleven engineering geological units were identified and mapped at 1:5.000 scale, which constitute the foundation ground of the old Kastoria town, as well as of its new areas of built-up extension. The identified ground units consist of six soil and five rock types. Soil units comprise one fill formation of variable composition and consistency with a ranging thickness between 2 m and 6 m and five loose to cohesive deposits, Holocene to Upper Pliocene in age, with high variation in grain size, density and plasticity factors. Rock lithologies range from highly to moderately weathered, closely fractured serpentinites and schists to fresh, widely fractured limestones. The old city of Kastoria is founded mainly on stable rocky ground and does not show any remarkable geotechnical problems. However, the need of built-up extension however and improvement of infrastructures, led to configurations of the marshy areas and to the use of foundation ground with poor mechanical properties, which locally need a special treatment to become stable.
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Singh, K. P. "Nonlinear estimation of aquifer parameters from surficial resistivity measurements." Hydrology and Earth System Sciences Discussions 2, no. 3 (June 10, 2005): 917–38. http://dx.doi.org/10.5194/hessd-2-917-2005.
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Abstract. The present study is focused on an examination of the correlation relationships for hydraulic permeability and transmissivity with electrical resistivity in a range of fractured and alluvial aquifers. The observed permeability data for fractured rock aquifers at some locations is correlated nonlinearly with electrical resistivity of the aquifers estimated from resistivity sounding data and it is found that the permeability of the aquifer in this region exponentially decreases with increase in resistivity. Permeability of the hard rock aquifer within the weathered zone and alluvium aquifers increases exponentially with increase in resistivity, and transmissivity decreases exponentially. However, in case of fracture rock and sandwiched aquifers, transmissivity increases exponentially with increase in resistivity. An attempt has been made to find general functional relationship between hydraulic parameters and resistivity of the aquifer, and therefore, published and observed data from India and other parts of the world has been taken under consideration. It is found that for fracture rock and alluvium aquifers, permeability and the transmissivity are best defined as the exponential functions of aquifer resistivity. The application of electrical parameters obtained from resistivity data for evaluation of hydraulic parameters has been demonstrated in detail within the Osmania University Campus, Hyderabad (India). The empirical relations between aquifer parameters and resistivity are established for transforming resistivity distribution into permeability and transmissivity of the aquifer. The information thus obtained from resistivity data on permeability of the aquifer and transmissivity distribution in the study area can be used for optimal use and assessment of water resources.
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Deepa, J. Nagaraju, Binod Chetia, Rajeev Tandon, P. K. Chaudhuary, and A. Bhardwaj. "Integrated study of a fractured granitic basement reservoir with connectivity analysis and identification of sweet spots: Cauvery Basin, India." Leading Edge 38, no. 4 (April 2019): 254–61. http://dx.doi.org/10.1190/tle38040254.1.
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Basement exploration in India has seen increased interest after the recent discovery of a field in the Cauvery Basin in southeastern India, with an average individual well production of 700 b/d from a fractured basement reservoir. The field is presently under development, with several development well locations identified for drilling. Optimized development of a fractured basement reservoir requires identification of areas with a permeable fracture network. To meet this objective, we adopted a comprehensive integrated workflow involving the use of common reflection angle migrated seismic data, fracture modeling, a 1D mechanical earth model (MEM), identification of critically stressed fractures in 3D space, fracture permeability/connectivity analysis, and sweet spot identification. The workflow yielded a robust discrete fracture network model based on 3D directional fracture intensity, a 1D MEM that gave regional stress gradients (pore pressure, overburden, Shmin, and SHmax), and rock strength and elastic properties. In addition, we generated a critically stressed 3D fracture model and performed sequential stratal surface restoration for predictive strain modeling that was calibrated at wells. Our fracture permeability and connectivity analysis showed that existing hydrocarbon-producing wells are located within areas that have a fracture cluster/swarm with associated good fracture connectivity. A 3D basement facies model constructed by integrating well data and a poststack inversion impedance volume showed that major flow zones occur in weathered basement associated with low impedance. This model, in combination with fracture intensity data, provides good indication of the location of basement sweet spots in the Cauvery Basin. The understanding gained on the controls of occurrence of basement fractures explains why some wells in the field are producers and others are dry. This led to greater confidence in optimizing the locations of previously proposed new development wells.
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Mandaglio, Maria Clorinda. "Geomechanical Characterization of the Rock Mass along a Deep Vertical Borehole." Geotechnics 4, no. 1 (February 20, 2024): 209–28. http://dx.doi.org/10.3390/geotechnics4010011.
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Deep vertical boreholes play a crucial role in underground exploration, resource extraction such as geothermal energy extraction, oil and gas exploration, underground waste storage and various underground engineering applications. The geomechanical properties of the rocks surrounding these boreholes are essential for designing safe, efficient drilling operations, for using adequate technologies and equipment and for providing mitigation measurements. Specifically, when the excavations are performed inside in-depth, extremely fractured and weathered rocks, the identification of zones more susceptible to crossing is a primary goal. This paper presents a thorough investigation into the rock masses surrounding a deep vertical borehole that involved the collection of core samples from the deep vertical borehole, laboratory testing, in situ tests and the application of geomechanical models to characterize the crossed rock masses. After a lithological and structural description of the rock masses and a description of the methodology used for their characterization, this paper focuses on the geomechanical parameterization of the rock mass using the uniaxial compressive strength of the intact rock (σci) and the Geological Strength Index (GSI). The obtained findings highlight the extreme variability in the depth of the geomechanical parameters of crossed rocks, which decreased with the depth. This methodology can be used to characterize rock masses along other deep boreholes, for which there is a lack of research, and to define the most problematic zones for underground crossing where different support works must be designed.
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Adamu, S., A. K. Yusuf, A. G. Kodomi, and I. B. Wulo. "A Reconnainsances Study to Delianate Conductive Groundwater Zone Using Resistivity Sounding in Some Part of Kwara State North-Central, Nigeria." Journal of Geography and Geology 12, no. 2 (August 31, 2020): 57. http://dx.doi.org/10.5539/jgg.v12n2p57.
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From the results, three to four electrostratigraphic layers with resistivity value ranging from 44 to 997 ohm/m and thickness ranging from 0.5 to 39.7 m were observed in the study area. The top loose rocks, the weathered conductive zone, the fractured basement rock and the fresh basement rock of older granite suite were encountered respectively. From this research, it can be deduce that, the thicker top soil and deeper weathered basement rock at the depth of 30 to 45 meters within this area produce a productive site for sitting future borehole. Insufficient groundwater supply in some places leading to scarcity is noticed in VES 10, VES 12 and VES 13. H, I, and A curve types are generally the most common in the area and are typical of basement complex area. Geographical Positioning System tool (model: GPSmap 76CSx), was used to locate the VES points. Fifteen VES points with electrode spacing [AB/2] of 100 meters separation around Ndanaku and environs were undertaken using Schlumberger configuration. IPI 2 Win [1990-2003] Geosoft resistivity sounding software was used to model the field curves from the measured data on the field. Groundwater in the area is regarded as poor due to localized nature of the aquifer and the study aimed at addressing this scarcity of water within the area by studying the conductive zone and knows the aquifer types through resistivity sounding techniques for future drilling.
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Lapides, Dana A., W. Jesse Hahm, Matthew Forrest, Daniella M. Rempe, Thomas Hickler, and David N. Dralle. "Inclusion of bedrock vadose zone in dynamic global vegetation models is key for simulating vegetation structure and function." Biogeosciences 21, no. 7 (April 11, 2024): 1801–26. http://dx.doi.org/10.5194/bg-21-1801-2024.
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Abstract. Across many upland environments, soils are thin and plant roots extend into fractured and weathered bedrock where moisture and nutrients can be obtained. Root water extraction from unsaturated weathered bedrock is widespread and, in many environments, can explain gradients in vegetation community composition, transpiration, and plant sensitivity to climate. Despite increasing recognition of its importance, the “rock moisture” reservoir is rarely incorporated into vegetation and Earth system models. Here, we address this weakness in a widely used dynamic global vegetation model (DGVM; LPJ-GUESS). First, we use a water flux-tracking deficit approach to more accurately parameterize plant-accessible water storage capacity across the contiguous United States, which critically includes the water in bedrock below depths typically prescribed by soil databases. Secondly, we exploit field-based knowledge of contrasting plant-available water storage capacity in weathered bedrock across two bedrock types in the Northern California Coast Ranges as a detailed case study. For the case study in Northern California, climate and soil water storage capacity are similar at the two study areas, but the site with thick weathered bedrock and ample rock moisture supports a temperate mixed broadleaf–needleleaf evergreen forest, whereas the site with thin weathered bedrock and limited rock moisture supports an oak savanna. The distinct biomes, seasonality and magnitude of transpiration and primary productivity, and baseflow magnitudes only emerge from the DGVM when a new and simple subsurface storage structure and hydrology scheme is parameterized with storage capacities extending beyond the soil into the bedrock. Across the contiguous United States, the updated hydrology and subsurface storage improve annual evapotranspiration estimates as compared to satellite-derived products, particularly in seasonally dry regions. Specifically, the updated hydrology and subsurface storage allow for enhanced evapotranspiration through the dry season that better matches actual evapotranspiration patterns. While we made changes to both the subsurface water storage capacity and the hydrology, the most important impacts on model performance derive from changes to the subsurface water storage capacity. Our findings highlight the importance of rock moisture in explaining and predicting vegetation structure and function, particularly in seasonally dry climates. These findings motivate efforts to better incorporate the rock moisture reservoir into vegetation, climate, and landscape evolution models.
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Zhao, Sihan, Hongchang Hu, Ciaran Harman, Fuqiang Tian, Qiang Tie, Yaping Liu, and Zhenyang Peng. "Understanding of Storm Runoff Generation in a Weathered, Fractured Granitoid Headwater Catchment in Northern China." Water 11, no. 1 (January 11, 2019): 123. http://dx.doi.org/10.3390/w11010123.
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Few of the classical field studies of streamflow generation in headwater watersheds have been conducted in catchments with thin soils and deeply weathered crystalline silicate bedrock. As such, the role of the (potentially very large) storage capacity of weathered, fractured rock in baseflow and storm event discharge remains poorly characterized. Here we present a study of streamflow generation in an upland semi-humid watershed (Xitaizi Experimental Watershed, XEW, 4.22 km2) dominated by baseflow feeding one of the main water supply reservoirs for the city of Beijing, China. This catchment is relatively dry (625 mm/yr precipitation, 480 mm/yr Evapotranspiration), but has strongly seasonal precipitation that varies in phase with strongly seasonal potential evapotranspiration. The catchment was instrumented with four weather stations and precipitation collectors, 11 deep wells drilled into the bedrock along three hillslopes, and additional soil moisture sensors and water samplers along one hillslope. In six storm events over two years, samples of rainfall, soil water (10–80 cm depth), groundwater, and stream water were collected with high frequency and analyzed for stable water isotopes (δ18O and δ2H). Tracer-based hydrograph separation showed that event water (precipitation) makes up the majority of the hydrograph peak above baseflow, and pre-event water contributions (on average) simply represent the steady release of groundwater. The quantity of event water corresponded to a very small effective contributing area (<0.2% of the catchment) that nevertheless showed a clear dependence on catchment wetness as measured by the streamflow. The streamflow itself was isotopically identical to the deep groundwater in wells. This suggests that the fractured, weathered, bedrock system dominates the production of streamflow in this catchment.
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Kolawole, T., O. O. Ajani, A. A. Adeniji, F. O. Aweda, and T. A. Adagunodo. "Geophysical Investigation of the Subsurface Structural Competency Around College of Computing and Communication Studies, Bowen University, Iwo, Osun State, South West Nigeria." International Journal of Research and Innovation in Applied Science IX, no. III (2024): 57–68. http://dx.doi.org/10.51584/ijrias.2024.90306.
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Mapping of the subsurface structures within the environment is highly essential in engineering site characterization. The subsurface structure around the college of computing and communication studies, Bowen University Nigeria was studied using the very low frequency electromagnetic (VLF-EM) and the geo-electrical resistivity method. This was aimed with a view to investigate the weak and competent geological zones. In this study, five traverses were generated for both the VLF-EM and geoelectrical resistivity method, using the VLF-EM 16 equipment and OHMMEGA-Terrameter respectively. The results of the VLF-EM revealed the presence of positive and negative anomalies responses. The positive anomalies indicate the weak zones, which may be caused by geological structures such as faults/fractures, and contacts between rocks and the negative anomalies indicate the competent zones, which may be due to hard rock/laterite. The geo-electrical resistivity results revealed the vertical and lateral inverted resistivity values of the subsurface structure. The result revealed four layers such as top soil, weathered layer, fractured and fresh basement. From both the interpreted results, the weak/fractured zones mapped in the basement are points of interest in this research. The results of the investigation revealed that the probable cause(s) of the structural failures within the study area are evidence of geological features mapped as fracture and clayey formation that is present in the study area. Therefore, in order to evade future structural problems and minimize capitals used in restoring distressed structures in the University, a geophysicist services should be engaged for pre-foundation studies, which will act as a guide before and during construction.
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Bedoya-Gonzalez, Diego, Sylke Hilberg, Günther Redhammer, and Thomas Rinder. "A Petrographic Investigation of the Carboniferous Sequence from the Ibbenbüren Mine: Tracing the Origin of the Coal Mine Drainage." Minerals 11, no. 5 (April 30, 2021): 483. http://dx.doi.org/10.3390/min11050483.
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The mine drainage of the Ibbenbüren anthracite coal mine is characterized by exceptionally high concentrations of dissolved iron and sulfate. The elevated position of the coal field with respect to the surrounding area makes the neighboring sediments an unlikely source of these elements. Accordingly, it has been hypothesized that interaction between infiltrating rainwater and the fractured overburden is a key process governing the mine drainage chemistry. To test this hypothesis, two full-diameter core samples drilled above the discharging adit of the coal mine were investigated. The methodology combined several analytical techniques to identify and characterize traces of water–rock interaction related to both diagenesis and relatively recent weathering processes along open fractures. The coupled appearance of kaolinite-dickite-illite minerals in weathered and unweathered rock sections was clearly connected to the burial history of the Carboniferous sequence. In contrast, the formation of iron (oxide-) hydroxides together with the presence of oxidized pyrite in weathering profiles along both sides of the fractures was positively related to the geochemical footprint of the coal mine drainage. Thus, open fractures, possibly originated from mining activities, may play a significant role in the drainage chemistry, especially considering the rather poor hydraulic conditions of the overburden.
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Park, Adrian F., and Bruce E. Broster. "Influence of glacitectonic fractures on wall failure in open excavations: Heath Steele Mines, New Brunswick, Canada." Canadian Geotechnical Journal 33, no. 5 (November 6, 1996): 720–31. http://dx.doi.org/10.1139/t96-098-319.
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Recognition and detailed mapping of glacigenic fractures and reactivated joints, along with such glacigenic features as striae and till fabrics, prove critical in predicting ground control hazards such as pit wall failure. Following a period of heavy rain in the autumn of 1991, a failure occured on part of the wall of an open-pit mining operation on the Heath Steel Mines property. The failure surfaces bounding the complex landslips of the pit wall were all either original glacigenic fractures or other joints reactivated during Late Wisconsinan glacier overriding. Apart from differential movement, such features include joints filled with coarse sand or clay. Comparaison of the geometry of glacigenic fractures in failed areas with the same features in areas just as densely fractured, but which did not fail, reveal a combination of circumstances where failure was predictable. In this case failure of an unstable rock mass resulted from unfavourable kinematic relationships involving the following: the low strength of clay- and sand-filled joints, the presence of highly permeable and weathered joint conduits, the unfavourable geometry between wall and joint orientation, and an occurrence of increased fluid pressure along the joints from high rainfall that triggered movement. Key words: glacitectonics, geotechnical, wall failure, excavations, rock-quality data, instability.
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MOMOTA, Hironobu, and Kuniaki SATO. "Three-dimensional groundwater analysis of tunnel and cavern in fractured rock ground with weathered layer." Doboku Gakkai Ronbunshu, no. 364 (1985): 41–50. http://dx.doi.org/10.2208/jscej.1985.364_41.
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Adekoya, S. A., H. T. Oladunjoye, J. O. Coker, and O. A. Adenuga. "Identification of lithological units using geo-electrical method, Olabisi Onabanjo University Campus, Southwestern Nigeria." Scientia Africana 20, no. 1 (April 23, 2021): 171–82. http://dx.doi.org/10.4314/sa.v20i1.15.
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The study presented the results obtained from estimation of the depth to the bsement bedrock (overburden thickness) in Olabisi Onabanjo University, Ago-Iwoye using two configurations of electrical resistivity methods. The study was aimed to delineate the stratigraphy and thicknesses of the subsurface layer present in the study area for comprehensive study of the lithostratigraphic information of the area. Vertical Electrical Sounding (VES) and 2-D Horizontal Electrical Profiling (HEP) techniques were used to obtain 1-D and 2-D subsurface resistivity images of the study area. The VES data were plotted manually on the Bi-log graph. The curve obtained was partially curve – matched to obtain the layer resistivities and thicknesses for further iteration. The 2-D resistivity imaging data were analyzed and processed to obtain the inverted (true) resistivity image. From the results, five (5) VES type curves weredelineated. These includes H, HA, QH and KH type. The geoelectric sections and 2-D resistivity images showed three to four geoelectric layers. These layers are topsoil/laterite, weathered basement, partly weathered/fractured basement and fresh basement. The study showed that materials with resistivity values that ranged between 10 and 298 Ωm and 152 and 589 Ωm representing clayey weathered layer and partly weathered/fractured basement were delineated beneath some sounding points. The clayey and weathered layer are indicative of soil formations that are inimical to foundation of civil engineering structure. Likewise, they can serve as reservoir for groundwater potential (if the porosity and permeability are high). Due to this, detailed lithostratigraphic evaluation through petrophysical analysis is encouraged for the purpose of mapping and correlation of the rock units before embarking on any engineering construction in the study area. The study concludes in providing assistance to subsequent research on the stratigraphic related studies in the area.
Keywords: Geo-electric , Stratigraphy, Lithology, Layer,
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Olumuyiwa, O. Falowo. "Engineering Site Investigation and Shallow Foundation Design in Ore Area of Ondo State, Nigeria." Materials and Geoenvironment 67, no. 1 (June 29, 2020): 21–33. http://dx.doi.org/10.2478/rmzmag-2020-0004.
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AbstractThe study integrates geophysical and geotechnical methods for subsoil evaluation and shallow foundation design. The study involved six vertical electrical sounding and geotechnical investigation involving cone penetration test and laboratory soil analysis. Three major geologic units were delineated; the topsoil, weathered layer and partly weathered/fractured/fresh bedrock. The overburden thickness is in between 15.2–32.9 m. Based on resistivity (16–890 ohm-m) and thickness (12.7–32 m) the weathered layer is competent to distribute structural load to underlying soil/rock. The groundwater level varies from 4.5 to 12.3 m. Therefore an average allowable bearing capacity of 200 kPa is recommended and would be appropriate for design of shallow foundation in the area, at a depth not less than 1.0 m with an expected settlement ranging from 9.03–48.20 mm. The ultimate bearing and allowable bearing capacity for depth levels of 1–3 m vary from 1403–2666 kPa and 468–889 kPa for strip footing while square footing varies in between 1956–3489 kPa and 652–1163 kPa respectively.
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Fonseca, António V., Luis F. M. Ribeiro, António Arêde, João Guedes, Esmeralda Paupério, Karim Karam, Aníbal Costa, and José E. T. Q. Menezes. "Suggested Methodology for Rehabilitation of Ancient Masonry Castles and Forts on Rock Hills." Soils and Rocks 37, no. 2 (May 1, 2014): 133–50. http://dx.doi.org/10.28927/sr.372133.
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Forts, including in this designation military castles, present high complexity due to their nature. Methodologies followed in the rehabilitation of forts are briefly presented, with the emphasis on characterization of materials and rock masses and on tests and numerical models developed for ancient forts. Studies concerning forts with Portuguese legacy are presented. The first case is related with rehabilitation of foundations and walls of the Guimarães Castle, Portugal. The causes of the appearance of holes or torn threads in the exposed face of the wall and the tower of the extreme southwest of the castle were assessed. The intervention performed was focused on the stabilization of the rock mass and careful sealing of discontinuities in the high strength rock mass and consolidation of the most weathered fractured rock mass. The second case is related to forts existing at Muscat, Oman. The protection of the Jalali Fort is studied in detail. During 2007, cyclone Gonu caused substantial damage to the seawall adjacent to the fort. The study addresses the redesign of the seawall.
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Sakai, K., M. Yamagami, T. Tani, and K. Fumimura. "Evaluating face stability in mountain tunnel excavation by inclination monitoring at the tunnel crown - Atoda tunnel case study." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012034. http://dx.doi.org/10.1088/1755-1315/1124/1/012034.
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Abstract The authors have been developing a prediction method for changes of ground stiffness ahead of a tunnel face by monitoring inclination at the tunnel crown (along the face advance axis). During the Atoda tunnel construction project, inclination monitoring was conducted at measurement intervals of 10 m. This is the first tunneling project practically using the proposed method throughout the excavation length. There is used a newly developed tilt sensor equipped with a Low-Power and Wide-Area (LPWA) wireless communication system that collects inclination data and transmits it to a data gateway automatically. During excavation work zones of weathered and fractured tuff breccia were recognized; face instability and partial collapse were experienced at those locations, though tunnel deformation was generally no more than 10 mm. Inclination values had a tendency to decrease in tunnel advance direction before the face encountered the soft/weak weathered rock, verifying the effectiveness of the method for monitoring tunnel stability and safety.
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Ariyo, Stephen Oluwafemi, Julius Ogunmola Fatoba, Olateju O. Bayewu, Kamaldeen Olakunle Omosanya, and Muhedeen Ajibola Lawal. "Geophysical Assessment of Subsurface Conditions at Proposed Building Sites: Implications for Foundation Failure and Building Collapse." GeoScience Engineering 64, no. 3 (September 1, 2018): 8–20. http://dx.doi.org/10.2478/gse-2018-0013.
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Abstract Building collapse has been a recurrent environmental hazard in Nigeria in the last two decades. This is a corollary of inadequate foundation investigation prior to construction, poor government policies, and general lack of awareness on the importance of geophysical and geotechnical investigations. In this study, geological mapping and detailed geophysical investigation using Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were carried out to understand the suitability of proposed building sites at the main campus of the Olabisi Onabanjo University (OOU), Ago-Iwoye, Nigeria for construction. Both Wenner array and dipole-dipole were used for profiling and Schlumberger for sounding. Four transverses and VES were used in each of the three areas investigated. Our results show that the subsurface of the study areas is underlain by Precambrian basement rock of Nigeria. Rocks in the study area include banded gneiss, porphyroblastic gneiss, biotite-hornblende granite and quartzite schist. The sounding stations across the three areas and 2D resistivity imaging revealed three principal geoelectric layers, the topsoil, the weathered layer and the fractured/fresh basement with varied resistivity values for each layers. At the VES stations, the three geoelectric layers have resistivity values of 62 to 1182 Ωm, 3.2 to 1360Ωm and 87 to 4680 Ωm. On the 2D resistivity imaging profiles, the resistivity of the three layers varies from 2 to 1182 Ωm, 30to 1360 Ωm, and 40 to 2904 Ωm for the topsoil, the weathered basement, and fractured/fresh bedrock. Our work demonstrates that some of the proposed sites are structurally incompetent for engineering or foundation purposes. Excavation of the topsoil and reinforcement are required to sustain the proposed structures.
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Sun, Xiaochang, Yin Jiang, Yong Huang, Yue Su, and Kehan Miao. "Modelling Groundwater Flow and Contaminant Migration in Heterogeneous Fractured Media at a Municipal Solid Waste Landfill in Nanjing Lishui, China." Geofluids 2022 (February 27, 2022): 1–15. http://dx.doi.org/10.1155/2022/8391260.
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The migration of groundwater flow and contaminants in fractured medium is complicated owing to the strong heterogeneity and anisotropy of fractured rock mass. Taking the environmental restoration and groundwater protection of the Lishui domestic waste landfill in Nanjing as the background, the groundwater environmental impact assessment and prediction are conducted for the groundwater environmental pollution that may be caused by the leakage of the landfill leachate after the closure of the domestic waste landfill. The strata of the landfill site are clay-cobble gravel, strongly and moderately weathered breccia, with obvious anisotropy and significant differences in rock mass permeability. A 3D numerical model of groundwater flow and contaminant migration in the landfill area is established by integrating the hydrogeological field tests and a conceptual model in the study area. Based on the parametric inversion method, the heterogeneous anisotropic permeability coefficient of the fractured medium is calibrated, and the temporal and spatial migration characteristics of contaminants such as ammonia nitrogen and mercury are predicted using the corrected model under the normal and failure conditions of the antiseepage curtain. The calculated results show that when the antiseepage fails, the maximum migration distances of contaminants in the horizontal direction after 100 days in the old and new landfills are 7.66 m and 15.64 m, respectively, and the maximum migration distances after 20 years are 192.5 m and 113.89 m, respectively. The migration direction and distances of contaminants are consistent with the hydrogeological conditions of the study area. The model calculation results provide a corresponding basis for the antiseepage control of contaminants.
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Sugianto, Nanang, and Refrizon Refrizon. "Struktur Kecepatan Gelombang Geser (Vs) di Daerah Rawan Gerakan Tanah (Longsor) Jalan Lintas Kabupaten Bengkulu Tengah-Kepahiang." INDONESIAN JOURNAL OF APPLIED PHYSICS 11, no. 2 (October 17, 2021): 134. http://dx.doi.org/10.13057/ijap.v11i2.41699.
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Shear wave velocity <em>(V<sub>s</sub>)</em> structure at along of Central Bengkulu-Kepahiang crossline has been mapped. This research aims to identify the subsurface structure and to estimate the constituent material type of rock in landslide-prone areas (Central Bengkulu-Kepahiang crossline). Shear wave velocity structure on each site is obtained by the HVSR-inversion of 146 microtremor data (ambient noise recording of seismometer). <em>V<sub>s</sub></em> structure at the line mapped from the surface until to 30 meters of the depth. Groups of Vs are identified in class E (<em>V<sub>s</sub></em> <180), Class D (180≤<em> V<sub>s</sub></em> <360), Class C (360≤<em> V<sub>s</sub></em> <760), and Class B (760≤<em> V<sub>s</sub></em> <1500). The subsurface structure at the depth of 0 to 10 meters are dominated by stiff soil, very dense soil, and soft rock which has highly fractured and weathered rock properties. At the depth of 15 meters to 30 meters, the subsurface structure is dominated by hard rock but it is high potential or easy to fracturing and weathering like the properties of the rocks in areas that have landslides in the past. Based on <em>V<sub>s</sub></em> value, rock constituent materials are deposition of sand, clay, gravel and alluvium ranging from soft to relatively hard structures at the depth.
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TSUKAMOTO, Hitoshi, Masahiko MAKINO, Tatsuya SUMITA, and Shiro WATANABE. "Surface and borehole geophysical methods to detect hydraulic pathways in fractured granitic rock masses and its weathered surface." Journal of Japanese Association of Hydrological Sciences 39, no. 4 (2010): 103–16. http://dx.doi.org/10.4145/jahs.39.103.
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Haque, Syeda Jesmin, and Norsyafina Roslan. "The Delineation of the Langat Basin Aquifer Based on Geological and Hydrogeological Characterization of Three Urban Areas of Malaysia." Journal of Geography, Environment and Earth Science International 27, no. 7 (July 7, 2023): 45–56. http://dx.doi.org/10.9734/jgeesi/2023/v27i7695.
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Aims: The aim of this study is to find out the hydrogeological settings and aquifer properties of Kajang, Bangi, and Semenyih urban areas to overcome the mismanagement of groundwater.
Study Design: The scarcity of groundwater is one of the major concerns of urbanization in growing populated countries like Malaysia. Lack of knowledge of subsurface geology, hydrogeology and aquifer properties is the main reason for the groundwater mismanagement of the Langat Basin.
Place and Duration of Study: The study targeted three growing urban areas Kajang, Bangi and Semenyih of Malaysia. Data were collected from the Mineral and Geosciences Department, Malaysia. Borehole logs, pumping tests and groundwater level monitoring data have been analysed and interpreted for this study.
Methodology: Subsurface logs have been produced by the Strater Demo4 software; Water level analyses have been done by the groundwater level monitoring data, the contour map was plotted by using ArcGIS software with calculated groundwater head values and the Pumping test curve has been prepared by using Excel 2007.
Results: Study areas are situated in Kenny Hill formation. Water is pumped from four types of formations they are; hard rock, weathered sedimentary, shallow sedimentary and a combination of alluvium and hard rock. Groundwater flow direction is controlled by the topography, from the hilly north-eastern side to the low elevated south-western side. The identified aquifer condition of the Kajang area is confined, boundary and consolidated fractured. Water is pumped from the confined fractured aquifer in Bangi town and from the leaky, consolidated fractured and unconfined aquifer in Semenyih town. Transmissivity and Specific capacity of all types of aquifers show a range of 2.35m2/day to 25.92m2/day and 2.64 m2/day to 41.28m2/day respectively.
Conclusion: This study will help to establish robust policies for the sustainable development of groundwater.
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P, Anandhan, Chidambaram S, Manivannan R, Paramaguru P, Karthikeyan C, Srinivasamoorthy K, and Prakash R. "Occurrence of Uranium in Groundwater from Cuddalore District Tamil Nadu Aided by Geospatial and Statistical Techniques." International Journal of Civil, Environmental and Agricultural Engineering 2, no. 2 (October 30, 2020): 1–16. http://dx.doi.org/10.34256/ijceae2021.
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An attempt has been made to examine uranium distribution in groundwater from Cuddalore district, Tamil Nadu, India. Groundwater occurs under porous sedimentary, fractured, and weathered hard rock formations ranging in age from recent sediments to the oldest Archean formations. A total of 186 groundwater samples were collected during Pre- Monsoon (May) and Post-monsoon (January) and analyzed for major cations, anions, and uranium using standard procedures. Major anions and cations follow the order Cl- >H4SiO4>HCO3- >NO3- > Na+> Ca2+> Mg2+>K+>SO42- > F-> PO43- irrespective of seasons. Uranium in groundwater ranges from 0.1 micro gram per liter (µg/l ) to 24.67 µg/l with average 1.82 µg/l. The spatial representation maps isolated areas of higher and lower uranium and statistical analysis inferred uranium sources to the groundwater environment.
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Hussain, Yawar, José Eloi Guimarães Campos, Welitom Rodrigues Borges, Rogério Elias Soares Uagoda, Omar Hamza, and Hans-Balder Havenith. "Hydrogeophysical Characterization of Fractured Aquifers for Groundwater Exploration in the Federal District of Brazil." Applied Sciences 12, no. 5 (February 28, 2022): 2509. http://dx.doi.org/10.3390/app12052509.
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The present study applies a geophysical approach to the Federal district of Brazil, a challenging hydrogeologic setting that requires improved investigation to enhance groundwater prospecting to meet the rising water demand. The geophysical characterization of a complex hard-rock aquifer sub-system was conducted using direct current (DC) electrical resistivity tomography (ERT) integrated with surface geological information. With a total of twenty-seven ERT profiles, the resistivity acquisition was carried out using a dipole-dipole array of electrodes with an inter-electrode spacing of 10 m. Based on resistivity ranges, the interpretation of the inverted resistivity values indicated a ground profile consisting of upper dry soil, saprolite, weathered, and fresh bedrock. Along with this layered subsurface stratigraphy, the approach allowed us to map the presence of significant hydrogeological features sharp contrasting anomalies that may suggest structural controls separating high-resistivity (≥7000 Ω m) and low-resistivity (<7000 Ω m) conducting zones in the uppermost 10 m of the ground. The assumed impacts of these features on groundwater development are discussed in light of the Brasilia aquifer settings.
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Wang, Jianjun, Yang Yang, Zhongsheng Tan, Dongfeng Li, and Qianli Liu. "Correction of Point Load Strength on Irregular Carbonaceous Slate in the Luang Prabang Suture Zone and the Prediction of Uniaxial Compressive Strength." Applied Sciences 12, no. 18 (September 12, 2022): 9147. http://dx.doi.org/10.3390/app12189147.
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Uniaxial compressive strength (UCS) testing requires high-quality core samples, which is a difficult task for weak, highly fractured, thinly bedded, foliated, and weathered rocks. In addition, it is time-consuming and expensive. Because of the good relationship between rock point load strength (PLS) and UCS, the PLS could be used to estimate rock UCS quickly. The lump structure and layer structure of carbonaceous slate are revealed in the tunnels of the China–Laos Railway in the Laos Luang Prabang Suture Zone as one of the important factors leading to tunnel squeezing deformation and support structures. To reveal the relationship between the PLS and UCS of carbonaceous slate in the Luang Prabang Suture Zone, PLS tests and UCS tests of lump-structure carbonaceous slate (lamina plane inconspicuous) and layer-structure carbonaceous slate (lamina plane conspicuous) were performed. Results show that the Is(50) of lump-structure carbonaceous slate ranged from 0.06 MPa to 0.30 Mpa, the Is(50) of layer-structure carbonaceous slates which were loaded perpendicular to the lamina plane ranged from 0.64 MPa to 1.25 MPa, the Is(50) of layer-structure carbonaceous slates which were loaded parallel to the lamina plane ranged from 0.49 MPa to 0.71 MPa, and the correction power index m ranged from 0.42 to 0.51 with an average value of 0.47. Four correlation expressions of carbonaceous slate relationships between PLS and UCS were fitted by zero-intercept linear expression, nonzero intercept linear expression, power expression, and logarithmic expression, and the calculation results were compared with results calculated by the International Society of Rock Mechanics (ISRM) correlation equation. It is concluded that the correlation equation between UCS and PLS recommended by ISRM specifications easily causes soft rock strength overestimation, which affects the correct evaluation of the surrounding rock property and the structural design safety of tunnels and underground projects. The zero-intercept linear equation UCS = 18.45Is(50) has better goodness of fit and higher accuracy in predicting the UCS of the carbonaceous slate in the Luang Prabang Suture Zone.
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Neradovskii, Leonid G. "Technology for studying the electrophysical characteristics of sedimentary rocks of South Yakutia at the railway station Kyurgellyakh using the method of remote inductive probing." Geoinformatika, no. 4 (December 25, 2023): 39–51. http://dx.doi.org/10.47148/1609-364x-2023-4-39-51.
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The possibilities of a new technology for applying the method of remote inductive sensing at a frequency of 1,125 and 0,281 MHz in the separation interval of the emitting and receiving antennas in terms of quantitative assessment of electrophysical characteristics in the rock foundation of engineering structures at the railway station Kyurgellyakh in South Yakutia are studied. In the strata of icy and clay deluvial-eluvial formations and sedimentary rocks (dolomites, limestones), a general increase in depth of the effective values of the electrical resistance and the real part of the complex relative permittivity, which is atypical in AC geoelectrics, has been established. The range of variability of resistivity and permeability is 600–1600 Ohm·m and 3–7 arb. units. According to a sharp change (from a smaller to a larger one) in the growth rate of resistance and permeability, two boundaries were found. The first structural boundary lies at a depth of about 10 m and corresponds to the lower boundary of the area of intense weathering. The second petrophysical boundary lies at a depth of about 20 m and characterizes the transition of the highly weathered and highly fractured upper part of the sedimentary rock mass into the lower consolidated solid part located in the area of thermal rest. The obtained results give grounds to recommend a proven technology for solving the problems of geomechanics and thermophysics of frozen soils in terms of determining their strength and depth of the lower boundary of the layer of annual heat exchanges.
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Bayewu, O. O., M. O. Oloruntola, G. O. Mosuro, O. O. Odugbesan, K. O. Bakare, O. O. Olukayode, O. A. Adenuga, and O. O. Oyebolu. "Hydrogeophysical exploration of groundwater potential in southwestern basement terrain of part of Ago-Iwoye, South western Nigeria." Scientia Africana 21, no. 1 (June 1, 2022): 37–52. http://dx.doi.org/10.4314/sa.v21i1.4.
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Electrical resistivity survey of Ago-Iwoye southwestern Nigeria was done with the aim of delineating potential zones for groundwater exploitation. The rock types present are mainly gneissic rocks; granite gneiss, banded gneiss, biotite gneiss and porphyroblastic gneiss.Forty five (45) Vertical Electrical Soundings (VES) of schlumberger array were carried out using maximum electrode spacing (AB/2) of 100m. The results obtained were interpreted using partial curve matching which serves as model input for the computer iteration using WINRESIST software to determine the resistivity, thickness and depth of each layer in the subsurface. The identified curve types are H, KH, HKH, A, K and QH types while the H type curve is predominant. The three prominent geo-electric layers were inferred, these are the topsoil, weathered layer (sand/clay/clayey sand) and fresh/fractured bedrock with resistivity values of 33.4Ωm - 2266.3Ωm, 8.3Ωm - 1106.3Ωm and 68.4Ωm - 21729.6Ωm respectively. The isopach reveals overburden thickness range of 2m – 52m, bedrock resistivity ranges from 1000Ωm - 19000Ωm and reflection coefficient range from 0.62 -0.92.The study area is predominantly of low yield but areas in the northeastern and western part of the study area have high aquiferous groundwater potential areas are only noticeable in the northeastern and western part of the study area.
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Shaibu, Ojoka Benjamin, O. Wasiu Osisanya, Saleh A. Saleh, E. Peter Asarhasa, and Emeka Caleb Okpala. "An Integration of Geophysics and Petrophysics in Study of Rock at Elete, Lokoja Southwestern Nigeria." British Journal of Earth Sciences Research 11, no. 3 (March 15, 2023): 47–74. http://dx.doi.org/10.37745/bjesr.2013/vol11n34774.
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Granitic Gneiss and Banded Gneiss make up the bulk of the local rock types, and quartz veins are the most common intrusions seen there. Tectonic upheavals in the earth's crust are responsible for the region's structural features, including as foliations, folds, joints, and fissures. The goal of this research is to integrate several scientific techniques to subsurface structure definition. For this study, 16 Vertical Electrical Sounding (VES), petrophysical study, and background knowledge of geology were used to delineate subsurface rock. The Schlumberger array with a maximum electrode separation of 300m was employed for VES. Elete's true aquifer resistivity map shows that the South-Eastern and North-Eastern axis has relatively low resistivity values, which may indicate the presence of an aquiferous zone, while the North-Central and Southern regions have a wider range of resistivity values, which may not be consistent with a water-bearing zone. Additionally, petrographic analysis of the rock reveals that the mineral composition of Granitic Gneiss is Quartz (41.72%), Plagioclase (10.79%), Biotite (25.17%), Muscovite (19.42%), and Opaque (2.87%). While biotite makes up the granite gneiss. Biotite (45%), Muscovite (9.93%), Quartz (36.87%), Plagioclase (4.26%), and Opaque (3. 55%).Hydrogeologically, it stands to reason that Elete and its surroundings are situated in a region with medium to good groundwater potential based on the information at hand and the results of the geophysical investigation. Weathered/fractured basements are anticipated to contain productive aquifers.
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Omowumi, Ademila. "Geophysical and geostatistical reserve estimates of migmatite-gneiss deposits from parts of southwestern nigeria." Global Journal of Geological Sciences 20, no. 1 (August 31, 2022): 109–28. http://dx.doi.org/10.4314/gjgs.v20i1.11.
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The plan for durable rock base road construction and other civil engineering works necessitated this study to establish the thickness and quantify migmatite-gneiss deposits. This intends to facilitate its exploitation and proffer specific details for diverse applications. Comprehensive geological field mapping, laboratory density measurements and geoelectrical resistivity were employed for the resource quantification. The extent of migmatite-gneiss deposits and its contacts with other rock types were identified. Seventeen (17) fresh migmatite-gneiss rock samples collected from different rock outcrops were taken to the laboratory for measurement of their density. Schlumberger vertical electrical sounding (VES) technique with a total of forty-two sounding stations were employed across the area with electrode spread (AB/2) ranging 1 - 200 m. The average density of the deposits is 2.70 ± 0.10 g/cm3. Three to five geologic layers characterized the area subsurface sequence. Thick fractured rock layer across the area would facilitate the exploitation of the deposits as construction aggregates. Basement topographical highs at northeastern, northwestern and southeastern parts serve as the best zones viable for mining. The basement resistivity (> 3000 Ωm), resistivity contrast, reflection coefficient values and high transverse layer resistivity (ρT) (> 500 Ωm) corroborate the freshness of the deposits. The average thickness of the deposit is 29.3 m, though, thicker at northeastern and northwestern parts of the area where the deposit is fresh and less weathered. The study area occupies a total area of 71,300,000 m2 with volume of the deposits calculated as 2,089,090,000 m3. Distantly-spaced data points of the variogram reveal high degree of variability with respect to locations. The estimated migmatite-gneiss resource tonnage of 5,640,543,000 tonnes shows prospects for sustainable large scale mining as construction aggregates and diverse applications of economic purposes using open pit coupled with underground mining for deeper sections of the migmatite-gneiss deposit.
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Poddar, M., and Walter L. Anderson. "Transient electromagnetic modeling of shallow A‐type sections with 3-D inhomogeneities." GEOPHYSICS 57, no. 6 (June 1992): 774–80. http://dx.doi.org/10.1190/1.1443291.
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A hard rock area underlain by granitic/gneissic or basaltic rocks often has an A‐type three‐layer geoelectric section in which resistivity increases with depth. The middle layer of moderate resistivity caused by fracturing/fissuring that lies between the surface‐weathered layer and the substratum of unfractured rock is not a good target for a direct current (DC) resistivity sounding since it is generally suppressed in the observations. Moreover, its definition requires expanding the electrode spacing to a length several times the depth of the target layer, and this may be a drawback if the target layer is either laterally variable or limited in its horizontal extent. We first studied the transient electric field of a horizontal electric dipole (HED) source excited by a step turn‐off current for a 1-D model of an A‐type geoelectric section. The results of this theoretical study are presented as graphs of normalized apparent resistivity versus a time‐related dimensionless parameter. Irrespective of the separation between the transmitter and receiver dipoles, these transient sounding curves become similar to the corresponding Schlumberger sounding curves at late time. Hence the transient electric field measurement offers the possibility of sounding at a fixed transmitter‐receiver spacing that may be shorter than the target depth. Also, at early times, for a certain ratio of the dipole separation to the target depth, there is a dramatic increase in the resolution of the response. Thus, it is possible to resolve suppressed layers of an A‐type section in this type of sounding. A study of the effects of transmitter ramp time and receiver bandwidth on the transient apparent resistivity curves shows that a very fast current shut‐off and wideband measurement are required to realize all the possibilities suggested by this modeling. Some 3-D transient electromagnetic (TEM) modeling was also done to simulate (1) a lateral variation in the resistivity of the middle layer of an A‐type section and (2) a weak zone of limited horizontal extent in the substratum of a two‐layer section. We observed that the 3-D inclusion has less effect at late time but is more pronounced at early time. In view of the above results, we conclude that the transient E‐field sounding with a grounded wire source can be used in place of a conventional DC resistivity sounding to overcome the problem of poor resolution due to the suppression of the intermediate layer in a geoelectric section where the resistivity increases with depth. As such, it has a potential application in groundwater as well as geotechnical surveys, because together with the overlying weathered layer, the fractured rock constitutes the aquifer in hard rocks.
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Verdian, Joseph P., Leonard S. Sklar, Clifford S. Riebe, and Jeffrey R. Moore. "Sediment size on talus slopes correlates with fracture spacing on bedrock cliffs: implications for predicting initial sediment size distributions on hillslopes." Earth Surface Dynamics 9, no. 4 (August 27, 2021): 1073–90. http://dx.doi.org/10.5194/esurf-9-1073-2021.
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Abstract. The detachment of rock fragments from fractured bedrock on hillslopes creates sediment with an initial size distribution that sets the upper limits on particle size for all subsequent stages in the evolution of sediment in landscapes. We hypothesize that the initial size distribution should depend on the size distribution of latent sediment (i.e., fracture-bound blocks in unweathered bedrock) and weathering of blocks both before and during detachment (e.g., disintegration along crystal grain boundaries). However, the initial size distribution is difficult to measure because the interface across which sediment is produced is often shielded from view by overlying soil. Here we overcome this limitation by comparing fracture spacings measured from exposed bedrock on cliff faces with particle size distributions in adjacent talus deposits at 15 talus–cliff pairs spanning a wide range of climates and lithologies in California. Median fracture spacing and particle size vary by more than 10-fold and correlate strongly with lithology. Fracture spacing and talus size distributions are also closely correlated in central tendency, spread, and shape, with b-axis diameters showing the closest correspondence with fracture spacing at most sites. This suggests that weathering has not modified latent sediment either before or during detachment from the cliff face. In addition, talus at our sites has not undergone much weathering after deposition and is slightly coarser than the latent sizes because it contains unexploited fractures inherited from bedrock. We introduce a new conceptual framework for understanding the relative importance of latent size and weathering in setting initial sediment size distributions in mountain landscapes. In this framework, hillslopes exist on a spectrum defined by the ratio of two characteristic timescales: the residence time in saprolite and weathered bedrock and the time required to detach a particle of a characteristic size. At one end of the spectrum, where weathering residence times are negligible, the latent size distribution can be used to predict the initial size distribution. At the other end of the spectrum, where weathering residence times are long, the latent size distribution can be erased by weathering in the critical zone.
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Pajock, Jamuth, Jagadeshan Gunalan, Muralitharan Jothimani, and Abel Abebe. "Assessment of groundwater potential zones using an integration of Remote Sensing, GIS and 2D Electrical Resistivity imaging in the Echway watershed, Baro River Basin, Southwest Ethiopia." IOP Conference Series: Materials Science and Engineering 1282, no. 1 (October 1, 2023): 012012. http://dx.doi.org/10.1088/1757-899x/1282/1/012012.
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Abstract The objective of this study is to delineate and identify the groundwater potential zone of degraded land in the Echway watershed, southwest Ethiopia, employing a combined approach that includes 2D electrical resistivity, the analytical hierarchy process (AHP), geographic information systems (GIS) and remote sensing (RS). Using a geographic information system (GIS) and remote sensing data, groundwater potential zones were identified by taking into account the soil types, drainage density, geology, lineament density, Land use and land cover, rainfall and slope. Using the AHP method, calculate the weight of thematic layers and rank of subclasses based on the effects of various thematic layers on groundwater potential. A significant weight was provided on the geology of the research region, total annual rainfall, and lineament density. Due to significant effects on groundwater potential zones, only three of the seven theme levels were assigned significant weight in this analysis. The weighted overlay analysis was used to construct the diagram of the zones with groundwater potential. 2D electrical resistivity was utilized to find the groundwater aquifer, and four major electrical layers were discovered: clayey silt, sand, moderately weathered/fractured rock, and basement parent rock. The groundwater potential zones in the study area have been classified into five categories: very low (22.97%), low (13.43%), moderate (32.50%), high (25.12%), and very high (5.98%) covered, respectively. The groundwater potential zone image was created by combining GIS, remote sensing, AHP, and an electrical survey
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Shang, Yan-Jun, Chang-Gen Yang, Wei-Jun Jin, Yan-Wei Chen, Muhammad Hasan, Yue Wang, Kun Li, Da-Ming Lin, and Min Zhou. "Application of Integrated Geophysical Methods for Site Suitability of Research Infrastructures (RIs) in China." Applied Sciences 11, no. 18 (September 17, 2021): 8666. http://dx.doi.org/10.3390/app11188666.
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Research Infrastructures (RIs) are essential to achieve excellence in innovative scientific research. However, because of limited land availability and specific geological requirements, evaluating the viability of a site for a new RI can be a challenging task. Stringent safety construction requirements include developing site-specific architectural and geoengineering solutions, minimizing construction disturbances, and reinforcing rock and soil in a timely fashion. For successful development of the RIs in China, such as the Daya Bay Neutrino Laboratory (DBNL) and the China Spallation Neutron Source (CSNS), an integrated approach of joint geophysical methods including the electrical resistivity tomography (ERT), controlled-source audio-frequency magneto telluric (CSAMT)), gravity and seismic refraction methods, and geological mapping and surveys were carried out. Geophysical parameters, such as electrical resistivity, density, and seismic velocity, show inverse proportion to the degree of rock fracturing or weathering. The results show that the low values of geophysical parameters suggest the weathered/fractured rock, while high values reveal the fresh bedrock. The Engineering Geological Suitability Index (EGSI) value can represent the individual EGSI values at a constant and summed over varying depths. EGSI methodology is an improvement on the existing siting process and has been applied to CSNS. Our integrated approach provides clearer insight into the subsurface for site suitability of RIs in challenging geological engineering conditions and removes any ambiguity caused by a single geophysical parameter. The obtained geological knowledge of the area not only provides engineers with much-needed information about the construction conditions of a potential site but also gives scientists the opportunity to explore the local geology. In this study, we demonstrate our innovative approach for siting RIs, as demonstrated by the synthetic evaluation of the site location and utilization for two established RIs (DBNL and CSNS).
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Lukačić, H., M. Krkač, S. Bernat Gazibara, Ž. Arbanas, and S. Mihalić Arbanas. "Detection of geometric properties of discontinuities on the Špičunak rock slope (Croatia) using high-resolution 3D Point Cloud generated from Terrestrial Laser Scanning." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012006. http://dx.doi.org/10.1088/1755-1315/1124/1/012006.
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Abstract Rock mass characterization is a very important part of engineering geological investigation. For a better understanding of the rock mass behaviour, it is crucially important to obtain as much as possible information about the discontinuity network, especially about orientation and the number of dominant discontinuity sets. The traditional methodology includes field mapping which dominantly produces a limited amount of data and consequently only a rough estimate about discontinuity network. To increase the number of measurements and to eliminate orientation bias, rock mass on the Špičunak rock slope in Gorski kotar, Croatia, was analysed using a combination of 3D Point Cloud and Textured Mesh Model generated from 3D Point Cloud by Poisson surface reconstruction. Both models were obtained from Terrestrial Laser Scanning. Two considerably different parts of a rock slope, with different weathering conditions and different degrees of fracturing were mapped. Discontinuities were mapped in the field and on the models using manual mapping techniques and semi-automated methods. Manual mapping on a 3D Point Cloud and Textured Mesh Model was done by Compass plugin and by Trace a polyline tool in Cloud Compare software version V2.12 and semi-automated mapping methods were done by Discontinuity Set Extractor and qFacet Fast Marching plugin for Cloud Compare software version V2.12. This study was used to show how the application of different methodologies, for the detection of geometric properties of discontinuities, influences the result. Statistical analyses were performed on the collected data to determine differences in the accuracy between the mapping techniques. Manual mapping on the 3D Point Cloud and high-resolution Textured Mesh Model showed good agreement with field measurements, apart from the higher number of discontinuities mapped by remote sensing methods. On the other hand, significant deviations were found between manual and semi-automated mapping techniques. Semiautomated methods did not correctly detect certain discontinuities, especially bedding planes that are perpendicular to a rock face. Also, semi-automated methods overestimate the number of discontinuity sets, especially in a highly weathered and highly fractured rock mass. These differences between methods can influence kinematic analysis results. Based on the results, an appropriate methodology was proposed to utilize the advantages of both manual and semiautomated methods. The proposed approach presents a powerful tool to accurately map and measure discontinuity orientation with results comparable to the field measurements.
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ALABI, A. A., A. O. ADEWALE, O. O. ADELEKE, F. G. AKINBORO, AYODEJI AFE, and ADAM GANIYU. "GEO-ELECTRIC INVESTIGATION OF GROUNDWATER POTENTIAL IN LADERIN HOUSING ESTATE, ABEOKUTA, SOUTHWESTERN, NIGERIA." Journal of Natural Sciences Engineering and Technology 19, no. 1 (December 2, 2021): 74–91. http://dx.doi.org/10.51406/jnset.v19i1.2098.
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Vertical Electrical Sounding (VES) and 2D Electrical Resistivity Tomography (ERT), with Schlumberger and Wenner electrode array configurations respectively were employed to investigate the groundwater potential of Laderin Housing Estate located at Oke-mosan, Abeokuta, Ogun state, southwestern Nigeria. The area is underlain by the basement complex of the southwestern Nigeria. The research aimed at determining the aquifer/groundwater zone and characterizes the lithology of the study area. The geophysical survey involving nine VES and four profile of 2-D ERT lines with lengths varying from 100 m to 150 m were carried out. The field data from both the ERT and VES were processed and interpreted using RES2DINV and WINRESIST software respectively. Geometrical effects from the pseudo-section were removed and an image of true depth and true formation resistivity were produced. Three to four geo-electric layers were revealed in all, which are; topsoil, weathered layer, fractured and fresh basement rock. The result of 2 D inversion provide lithologic unit, weathering profile and geological structure favourable for groundwater potential. The results show that the basement rock was delineated with resistivity values that range between 701.3 Ωm and 9459.3 Ωm. The bedrock topography has a variable thickness of overburden between 3 m and above 16.4 m, which is fairly shallow. The geophysical survey show that VES 2, VES 3, VES 4, VES 5, and VES 6 are possible location for groundwater extraction. The difficult terrain, where thick overburden are located are also promising target for groundwater development.
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Boisson, A., N. Guihéneuf, J. Perrin, O. Bour, B. Dewandel, A. Dausse, M. Viossanges, S. Ahmed, and J. C. Maréchal. "Determining the vertical evolution of hydrodynamic parameters in weathered and fractured south Indian crystalline-rock aquifers: insights from a study on an instrumented site." Hydrogeology Journal 23, no. 4 (February 4, 2015): 757–73. http://dx.doi.org/10.1007/s10040-014-1226-x.
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Flowers, Rebecca M., Francis A. Macdonald, Christine S. Siddoway, and Rachel Havranek. "Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth." Proceedings of the National Academy of Sciences 117, no. 19 (April 27, 2020): 10172–80. http://dx.doi.org/10.1073/pnas.1913131117.
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The Great Unconformity marks a major gap in the continental geological record, separating Precambrian basement from Phanerozoic sedimentary rocks. However, the timing, magnitude, spatial heterogeneity, and causes of the erosional event(s) and/or depositional hiatus that lead to its development are unknown. We present field relationships from the 1.07-Ga Pikes Peak batholith in Colorado that constrain the position of Cryogenian and Cambrian paleosurfaces below the Great Unconformity. Tavakaiv sandstone injectites with an age of ≥676 ± 26 Ma cut Pikes Peak granite. Injection of quartzose sediment in bulbous bodies indicates near-surface conditions during emplacement. Fractured, weathered wall rock around Tavakaiv bodies and intensely altered basement fragments within unweathered injectites imply still earlier regolith development. These observations provide evidence that the granite was exhumed and resided at the surface prior to sand injection, likely before the 717-Ma Sturtian glaciation for the climate appropriate for regolith formation over an extensive region of the paleolandscape. The 510-Ma Sawatch sandstone directly overlies Tavakaiv-injected Pikes granite and drapes over core stones in Pikes regolith, consistent with limited erosion between 717 and 510 Ma. Zircon (U-Th)/He dates for basement below the Great Unconformity are 975 to 46 Ma and are consistent with exhumation by 717 Ma. Our results provide evidence that most erosion below the Great Unconformity in Colorado occurred before the first Neoproterozoic Snowball Earth and therefore cannot be a product of glacial erosion. We propose that multiple Great Unconformities developed diachronously and represent regional tectonic features rather than a synchronous global phenomenon.