Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Low overburden.
Zeitschriftenartikel zum Thema „Low overburden“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Zeitschriftenartikel für die Forschung zum Thema "Low overburden" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Zeitschriftenartikel für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Ji, Yanju, Shangyu Du, Lijun Xie, Kai Chang, Yang Liu, Yi Zhang, Xiaoming Xie, Yuan Wang, Jun Lin und Liangliang Rong. „TEM measurement in a low resistivity overburden performed by using low temperature SQUID“. Journal of Applied Geophysics 135 (Dezember 2016): 243–48. http://dx.doi.org/10.1016/j.jappgeo.2016.09.027.
Der volle Inhalt der Quelle
2
Lo, S. C. R. „Pull-Out Resistance of Polyester Straps at Low Overburden Stress“. Geosynthetics International 5, Nr. 4 (Januar 1998): 361–82. http://dx.doi.org/10.1680/gein.5.0126.
Der volle Inhalt der Quelle
3
Su, Xiaochao, Zhilong Chen, Xudong Zhao, Xiaobin Yang, Qilin Feng und Haizhou Tang. „Optimization Design of Underground Space Overburden Thickness in a Residential Area Concerning Outdoor Thermal Environment Evaluation“. Sustainability 10, Nr. 9 (07.09.2018): 3205. http://dx.doi.org/10.3390/su10093205.
Der volle Inhalt der QuelleAnnotation:
Reasonable design of the overburden thickness of underground space (OTUS) can influence the outdoor thermal environment by affecting the ground plant communities. To optimize the design of the OTUS for improving the outdoor thermal environment, this study summarized the influence mechanism of the OTUS on the outdoor thermal environment and proposed a framework of the optimization design of underground space overburden thickness. A typical row layout residential area in Nanjing, China, was taken as the research object on which to perform a numerical study of the influence of plant communities formed by two types of plant collocations (a middle- and low-level plant collocation and a middle- and high-level plant collocation) on the outdoor thermal environment (airflow field, air temperature, relative humidity and thermal comfort) under three different ratios of trees to shrubs (2:3, 1:2, and 1:3), and to provide suggestions regarding the design of the OTUS according to the designer’s requirements. The conclusions were summarized as follows: (1) If a designer wants to enhance outdoor ventilation, the OTUS should be designed to satisfy the requirements for the middle- and low-level plant collocations and the overburden thickness of the 2/5 underground space development area should be set to 80~100 cm, the overburden thickness of the other 2/5 area should be set to 45~60 cm and the overburden thickness of the remaining 1/5 area should be set to 30~45 cm. (2) If a designer wants to reduce air temperature, increase relative humidity, and improve outdoor thermal comfort, the OTUS should be designed to satisfy the requirements for middle- and high-level plant collocations and the overburden thickness of the 1/4 underground space development area should be set to 80~100 cm, and the overburden thickness of the remaining 3/4 area should be set to 45~60 cm.
4
Gastrich, Holger, Claus Gößling, Reiner Klingenberg, Kevin Kröninger, Till Neddermann, Christian Nitsch, Thomas Quante und Kai Zuber. „The Dortmund Low Background Facility — Low-background gamma ray spectrometry with an artificial overburden“. Applied Radiation and Isotopes 112 (Juni 2016): 165–76. http://dx.doi.org/10.1016/j.apradiso.2016.03.025.
Der volle Inhalt der Quelle
5
Kapure, G. U., C. B. Rao, V. D. Tathavadkar und R. Sen. „Direct reduction of low grade chromite overburden for recovery of metals“. Ironmaking & Steelmaking 38, Nr. 8 (November 2011): 590–96. http://dx.doi.org/10.1179/1743281211y.0000000028.
Der volle Inhalt der Quelle
6
Das, Sarat Kumar, Mahasakti Mahamaya und Krishna R. Reddy. „Coal mine overburden soft shale as a controlled low strength material“. International Journal of Mining, Reclamation and Environment 34, Nr. 10 (11.02.2020): 725–47. http://dx.doi.org/10.1080/17480930.2020.1721043.
Der volle Inhalt der Quelle
7
Negrão, Leonardo Boiadeiro Ayres, Herbert Pöllmann und Marcondes Lima da Costa. „Production of low-CO2 cements using abundant bauxite overburden “Belterra Clay”“. Sustainable Materials and Technologies 29 (September 2021): e00299. http://dx.doi.org/10.1016/j.susmat.2021.e00299.
Der volle Inhalt der Quelle
8
Pettifer, G. R., N. Djordjevic, D. Heislers, J. Schaeffer und J. A. Withers. „Geophysical and image processing methods for detection of fireholes in brown coal, Latrobe Valley“. Exploration Geophysics 20, Nr. 2 (1989): 153. http://dx.doi.org/10.1071/eg989153.
Der volle Inhalt der QuelleAnnotation:
Fireholes at the top of the thick Latrobe Valley brown coal seams pose a geotechnical hazard to overburden dredges and reduce coal reserves. Overburden thickness (typically 10 to 15 m) is up to 50 m in the fireholes, which are from 20 to hundreds of metres in diameter and are infilled with baked clays, soft lacustrine clays and alluvial deposits.Given the complexity of firehole geometry and overburden geology, firehole definition prior to overburden stripping, by drilling alone, is expensive and is not definitive. To improve firehole exploration, geophysical methods were tried in a test area with good borehole control (115 holes), near Morwell open cut.Grid geophysics (20m. � 20m., 2805 grid stations) using gravity, EM34 20 m loop conductivity and high resolution magnetics gave very good results. Shallow seismic reflection methods were not successful.Residual gravity defined overburden thickness variations best with gravity highs of up to 6.5 micrometres/sec2 over the fireholes. EM conductivity showed reasonable correlation with overburden thickness, with EM conductivity highs over fireholes infilled with lower resistivity lacustrine clays and silts. High resolution magnetics using a TM-3 caesium vapour magnetometer, despite high cultural interference, showed broad, low amplitude highs over fireholes where higher susceptibility baked clays are thickest. The three geophysical data sets and overburden data were gridded (5m. � 5m.) and the grids dumped to a MicroBrian image processing system. Conventional image processing analysis was carried out to compare, enhance, filter, display and classify the complementary data sets. A classification scheme for overburden type based on geophysical responses plus a routine firehole exploration methodology using residual gravity, EM, magnetics, progressive drilling data and the image processor was devised to reduce drilling costs and increase exploration confidence. The case history presents the results of the grid geophysics and image processing approach.
9
El-Aswad, Ali, Intesar Elagil und Salem Fatooh. „STRESS EFFECT ON CEMENTATION FACTOR OF SANDSTONE ROCKS TYPE EVIDENCE FOR A VARIABLE ARCHIE POROSITY EXPONENT “m”“. Scientific Journal of Applied Sciences of Sabratha University 1, Nr. 1 (27.12.2018): 50–66. http://dx.doi.org/10.47891/sabujas.v1i1.50-66.
Der volle Inhalt der QuelleAnnotation:
Ancient sandstones include important reservoirs for hydrocarbons (oil and gas). This research provides an experimental investigation on the influence of variations in confining pressure on cementation factor of two wells located in Sirt basin. Measurements of formation resistivity factor versus cementation factor for sandstone samples which were collected from both wells at different confining pressures were carried out. The Effects of confining stress on the electrical properties of the rock samples were studied and analyzed. The results showed that the confining pressure variations depend on the pore structure of the studied rock. Furthermore, it can be concluded that the electrical resistivity of rocks is function of pore size distribution and how the fluids were distributed in the pore spaces. The effect of overburden pressure and the porosity variation on cementation factor is also investigated for different rock types. It has been concluded that the compaction due to overburden pressure generally causes a considerable increase in resistivity, especially in poorly cemented rocks. In low-porosity rocks, resistivity measurements determined under representative overburden pressures that are strongly recommended to improve well log interpretation.
10
Dreesen, David R., John T. Harrington, Anne M. Wagner, Leigh Murray und Peixin Sun. „TESTING NATIVE GRASSES FOR SURVIVAL AND GROWTH IN LOW pH MINE OVERBURDEN“. Journal American Society of Mining and Reclamation 2001, Nr. 1 (2001): 2–17. http://dx.doi.org/10.21000/jasmr01010002.
Der volle Inhalt der Quelle
11
Mancinelli, Dotting L. „Evaluation of superficial settlements in low overburden tunnel TBM excavation: Numerical approaches“. Geotechnical and Geological Engineering 23, Nr. 3 (Juni 2005): 263–71. http://dx.doi.org/10.1007/s10706-003-6257-3.
Der volle Inhalt der Quelle
12
Sánchez, Paul, und Daniel J. Scheeres. „Seismic waves in the asteroid environment“. EPJ Web of Conferences 249 (2021): 13001. http://dx.doi.org/10.1051/epjconf/202124913001.
Der volle Inhalt der QuelleAnnotation:
Through numerical simulations, we investigate impact generated seismic wave transmission in granular media under extremely low pressure. This mimics the conditions in the interior of asteroids and other small planetary bodies. We find a dependency not only on the overburden pressure on the medium, but also on the velocity of the impact that generates the wave. This is, at extremely low values of overburden pressure, the wave speed depends no only on the imposed pressure, but also on the increment in pressure created by the passing of the wave. We study crystalline and random packings and find very similar behaviour though with different wave speeds as expected. We then relate our results to different mission-related events on asteroids.
13
Chen, Xuejun, Ruijian Guo, Lingming Tang und Xiaochen Zhang. „Study on Ground Collapse of Covered Karst Soil Caves by Sudden Drop of Groundwater“. Advances in Civil Engineering 2021 (10.08.2021): 1–12. http://dx.doi.org/10.1155/2021/7796401.
Der volle Inhalt der QuelleAnnotation:
In this study, the ellipsoidal soil cave with vertical collapses in the covering karst area is studied. Based on certain assumptions, the mechanical model of karst collapse caused by groundwater drop was established. Then, based on the negative pressure calculation formula of soil cave cavity according to Boyle–Mariotte’s law, the expression of the stability coefficient of the soil cave was proposed. Subsequently, the feasibility of the theoretical formula was verified. The calculation example analyzed the relationship of groundwater parameters and overburden thickness. The results show that when the initial groundwater level is higher than the top of cave, the law between the stability coefficient of soil cave and groundwater drawdown shows the jumping horizontal broken line. Thus, soil cave tends to collapse when the falling groundwater level drops over the vault; when the initial groundwater level ranges from the bottom to the top of the cave body, the stability coefficient and groundwater drawdown show a negative correlation law, the curve is steep at the early stage and then becomes gentle at the latter stage, and the higher the initial groundwater level in the cave is, the greater stability coefficient of soil cave reduces; when the initial groundwater level is lower than the bottom of the cave, the effect of drawdown is limited. In addition, for the small drawdown or low initial groundwater level, the stability coefficient of soil cave first decreases and then increases with the increases in thickness of overburden, and the thinner the overburden is, the greater the drawdown rate is; when the drawdown or the initial groundwater level is higher, the stability coefficient of soil cave positively relates to the thickness of the overburden layer.
14
Brown, G. M. C., und C. D. Grant. „Nutrient status of pasture ecosystems established on rehabilitated overburden and topsoil sites in the Hunter Valley, New South Wales“. Soil Research 38, Nr. 2 (2000): 479. http://dx.doi.org/10.1071/sr99061.
Der volle Inhalt der QuelleAnnotation:
The rehabilitation of disturbed areas at the Howick Coal Mine (Hunter Valley, New South Wales) involves re-creating pasture ecosystems. Some sites are rehabilitated using topsoil, whereas others are established directly into the overburden mine waste due to the low availability and poor quality of topsoil. Pastures on both substrate types are then maintained by periodic applications of fertiliser. A comparison was made between nutrient levels held in the soil and the roots and stems of the dominant pasture grass (Rhodes grass, Chloris spp.) in an overburden (rehabilitated in 1990) and a topsoil site (rehabilitated in 1991). Sampling was conducted in autumn 1998 at 3 random locations along 3 replicate transects established on both substrates. Laboratory analyses were conducted to determine levels of N, P, S, Ca, K, Mg, and Na for both soil and plants samples; Mn, Fe, Zn, Cu, and Al for the plant samples only; and NO 3-N, PO 4-P, organic carbon, pH, and EC for the soil samples only. Multivariate analysis showed a distinct difference in the nutrient status of topsoil and overburden sites, across the 7 nutrients common to the roots, stems, and soil. The concentration of all macronutrients was significantly higher in the overburden compared with the topsoil sites. The majority of macronutrients were in greatest concentrations in the stems but the highest levels of micronutrients were found in the roots. There was a higher concentration of micronutrients in the overburden sites. Both of the rehabilitated sites had adequate macronutrient concentrations of S, Ca, Mg, and K. However, there were deficient concentrations of NO3-N in both the topsoil and overburden sites and a deficient concentration of PO4-P in the topsoil site. Long-term management options to improve the nutrient status of rehabilitated coal mines in the Hunter Valley include increased grazing, increasing fertiliser inputs, and burning the rehabilitated areas.
15
Harrington, J. T., D. R. Dreesen, A. M. Wagner, L. Murray und P. Sun. „RESULTS OF SPECIES TRIALS ON LOW pH OVERBURDEN MATERIALS FOR MINE LAND RECLAMATION“. Journal American Society of Mining and Reclamation 2001, Nr. 1 (2001): 112–20. http://dx.doi.org/10.21000/jasmr01010112.
Der volle Inhalt der Quelle
16
Bhaskar, Kiran Lata, und Bhagyadhar Bhoi. „Iron and Nickel Enrichment in Low Grade Chromite Overburden to Produce Ferronickel Alloys“. Transactions of the Indian Institute of Metals 74, Nr. 6 (16.03.2021): 1321–32. http://dx.doi.org/10.1007/s12666-020-02176-4.
Der volle Inhalt der Quelle
17
Lappegard, Gaute, und Jack Kohler. „Determination of basal hydraulic systems based on subglacial high-pressure pump experiments“. Annals of Glaciology 40 (2005): 37–42. http://dx.doi.org/10.3189/172756405781813681.
Der volle Inhalt der QuelleAnnotation:
AbstractWe have conducted short-term pump experiments with pump pressures exceeding ice overburden to study the seasonality of the subglacial hydraulic system of Engabreen, Norway. Data were collected from load cells installed flush with the ice–bedrock interface and pressure transducers installed in boreholes leading from bedrock tunnels underneath the glacier to the ice–bedrock interface. The water-pressure recordings, seen in relation with the load-cell record, show the existence of hydraulically connected vs unconnected bed areas. Monitored boreholes have been used to inject water at high pressures. Each experiment led to the growth of a high-pressure water cavity whose spatial extent could be inferred from load-cell and pressure transducer records. Post-pump pressures were low after summer pump tests and close to ice-overburden level after winter pump experiments. We conclude that drainage takes place in a fast-flow, low-pressure, channel-based drainage system during summer, and a low-flow, high-pressure, linked-cavity drainage system during winter.
18
Kim, Byeong-Su, Satoru Shibuya, Seong-Wan Park und Shoji Kato. „Application of suction stress for estimating unsaturated shear strength of soils using direct shear testing under low confining pressure“. Canadian Geotechnical Journal 47, Nr. 9 (September 2010): 955–70. http://dx.doi.org/10.1139/t10-007.
Der volle Inhalt der QuelleAnnotation:
The primary objective of this study is to evaluate effects of suction on shear strength of unsaturated soils under low confining pressure and to examine the relationships between suction, shear strength behavior, and volumetric deformation using newly developed direct shear testing equipment for compacted weathered granite soils. The soil-water retention curves (SWRCs) of unsaturated soils were obtained under various overburden pressures. To analyze test results from the direct shear test under unsaturated conditions, a new method, suction stress–SWRC method (SSM), is proposed to determine the suction value for each overburden pressure and the suction stresses. As a result, it has been found that the stress states at the peak shear strength point are on the same failure line for the saturated state when the suction stress is treated as a component of confining pressure. The relationship between stress ratio and dilatancy for the saturated state can be extended to the unsaturated state. It is also noted that the estimated unsaturated shear strengths using the SSM agree well with the measured values from laboratory testing.
19
Guo, Qiang, und Tariq Alkhalifah. „Datum-based waveform inversion using a subsurface-scattering imaging condition“. GEOPHYSICS 84, Nr. 4 (01.07.2019): S251—S266. http://dx.doi.org/10.1190/geo2018-0615.1.
Der volle Inhalt der QuelleAnnotation:
Full-waveform inversion (FWI) solves model optimization problems by fitting simulated data to the observed data. The implementation of FWI requires involving as many physical features of the subsurface medium in the simulation as possible. The computation can be extremely costly and complex because the FWI algorithm usually deploys a consistent discretization over the entire model space, whereas a high-resolution analysis (and the accompanying complex physics) is often only required in the reservoir region. As an alternative, we have developed an FWI optimization scheme based on a convolution type of modeling from the datum. The solution of such an inversion consists of the overburden, which includes the medium above a datum level, and the virtual data at the datum, which represent the underlying medium, i.e., the reservoir. We formulate the redatuming operation using a modified expression of the extended Born representation. Based on that, the virtual data can be retrieved by using the subsurface-scattering imaging condition. By measuring the data misfit at the surface acquisition, we implement a simultaneous inversion for the overburden velocity and the virtual data at that datum. This velocity inversion is crucial to the redatuming, but we can rely on fairly simple physics compared to the complex reservoir region. The redatumed data, in turn, are involved in resolving the overburden velocity. We develop a robust estimate of the velocity using low-wavenumber updates along the reflection wavepaths generated by our modeling process including the overburden scattering and those coming from the datum. Using numerical examples, we determine that our optimization is capable of mitigating the complex wave-propagation effects of the overburden medium and output redatumed data with plausible relative amplitude, which is achieved given little knowledge of the model.
20
Sunderland, Andrew, Ray Lockwood, Li Ju und David G. Blair. „Low-frequency rotational isolator for airborne exploration“. GEOPHYSICS 82, Nr. 2 (01.03.2017): E27—E30. http://dx.doi.org/10.1190/geo2015-0521.1.
Der volle Inhalt der QuelleAnnotation:
We have determined the performance of a passive rotational vibration isolator for a time-domain airborne electromagnetic (TDEM) receiver. The isolator uses neutrally buoyant flotation to provide very soft suspension and a very low resonant frequency of 0.065 Hz ± 0.005 Hz. One of the limitations of mapping deeper targets in areas of conductive overburden with TDEM systems is that low-frequency coil-vibration noise provides a lower bound to the transmitter base frequency (typically limited to 25 Hz). The purpose of this new isolator is to improve coil vibration related noise between 5 and 20 Hz to allow the transmitter base frequency to be reduced. A fixed-wing flight test determined that a receiver inside the new isolator had five times less rotational noise at 10 Hz than a current commercial system.
21
Hernández Díaz, Ianeya, Federico Galizia, Orquidea Coto Pérez und Edgardo R. Donati. „Reduction of Heavy-Metal Content in Overburden Material by Bacterial Action“. Advanced Materials Research 71-73 (Mai 2009): 653–56. http://dx.doi.org/10.4028/www.scientific.net/amr.71-73.653.
Der volle Inhalt der QuelleAnnotation:
In previous studies it has been showed that bacterially produced sulphuric acid is a good leaching agent for laterite tailings. In this work we evaluated heavy metals leaching from low grade laterite ore for cobalt and nickel extraction using sulphuric acid produced in situ by Acidithiobacillus thiooxidans under different culture conditions. In studies where that material was initially added to the cultures, considerable percentages of metals were leached (100 % Mn, 70 % Co, 7.5 % Ni, less than 5 % of Cr and Fe) after 18 days of incubation at low pulp densities (1 % and 2.5 %) of overburden. The maximum percentages were reached when cultures pH was approximately or below than 1.5. At higher pulp densities material was added to the cultures after different pre-cultivating times; also higher sulphur amounts were assayed; in such way about 100 % Mn, 60 % Co, 9 % Ni and Fe and 2.5 % Cr were leached. Although toxic metals were not completely leached, sequential extractions results indicate that these metals are not readily available. All studies finally suggest that bioleaching is a suitable technology for recovery of valuable metals as Co and remediation of mining residues by extraction of heavy metals.
22
Guo, Qiang, und Tariq Alkhalifah. „Target-oriented waveform redatuming and high-resolution inversion: Role of the overburden“. GEOPHYSICS 85, Nr. 6 (01.11.2020): R525—R536. http://dx.doi.org/10.1190/geo2019-0640.1.
Der volle Inhalt der QuelleAnnotation:
Target-oriented inversion (TOI) is an approach aimed at enhancing the ability of full-waveform inversion (FWI) to achieve a high-resolution delineation of a reservoir. FWI has demonstrated its potential to address the challenge of imaging complex structures on a considerable number of field data applications. Nevertheless, it is still impractical costwise to implement FWI with the full band of seismic data because, in this case, we need to discretize the whole subsurface model space with a fine grid to handle the high frequencies and satisfy the interpretation of, for example, reservoir-scale features. Redatuming techniques enable us to obtain a virtual data set at the target level from the original data acquisition that is most commonly deployed on the earth’s surface. The virtual data set can help us apply a high-resolution FWI to the target region, which often occupies a small area of the entire model space. To analyze such a redatuming process, we need to estimate an overburden model that can accurately describe the kinematics and dynamics of the wave propagation. Fortunately, our virtual data retrieval can rely on the overburden estimation with relatively low resolution, because the high-frequency multiple scattering has a limited effect on the deep part and on the corresponding virtual data. Therefore, we start with macro-overburden models that contain reasonably accurate kinematics, and we then apply FWI on the overburden with only low-frequency data. The resulting model is used to implement a least-squares waveform redatuming using the full band. The Marmousi model and Chevron 2014 benchmark data set are used to demonstrate the effectiveness of our strategy, which results in the high-resolution inversion of the target areas. Our TOI workflow leads to an obvious boost in efficiency and reduces the memory requirement because the finer grid needed for the high frequencies is only adopted for the redatuming and the TOI.
23
Buselli, G., K. G. McCracken und M. Thorburn. „Transient electromagnetic response of the Teutonic Bore orebody“. GEOPHYSICS 51, Nr. 4 (April 1986): 957–63. http://dx.doi.org/10.1190/1.1442153.
Der volle Inhalt der QuelleAnnotation:
Transient electromagnetic (TEM) measurements have been made with SIROTEM on four separate surveys over the Teutonic Bore orebody (Western Australia), both before mining operations began and subsequently during different stages of stripping overburden from the mineral deposit. In the late stage of the transient decay the target response was relatively free of the overburden and host‐rock response. Beyond ∼ 6 ms, the maximum anomalous response was a factor of 8 to 10 greater than the combined overburden and host‐rock response. Analog modeling with a copper plate in free space shows that the TEM response of the target consists of a single peak at early delay times, while at delay times beyond ∼ 4.2 ms, the response becomes a double‐peak anomaly with a low directly over the top of the plate. Mathematical modeling of the TEM response with a free‐space infinitely thin plate produces profile characteristics similar to those obtained by analog modeling beyond a delay time of ∼ 4.2 ms. Inversion of premining survey profiles in the delay time range 7.0 to 13.2 ms gives values of 82 m for target depth d, and 86 degrees for dip angle θ. These agree well with the values d = 86 m and θ = 82 degrees derived from drilling data. A target conductance value in the range 250 to 320 S is obtained from the TEM data, indicating that the massive sulfide target is highly conductive. Responses calculated for surveys made during overburden stripping are lower than corresponding field values at early delay times because of the absence of overburden response in the model measurements. At delay times beyond 8.5 ms, the model values are consistent with the field values. These results indicate that for a case similar to the Teutonic Bore orebody, where the maximum anomalous late‐time response is a factor of 8 to 10 times greater than the background response, important target parameters may be derived from free‐space models.
24
Ganesh, P., Dishwar Kumar, S. Agrawal, Mandal Kumar, N. Sahu und O. P. Sinha. „Feasibility of nickel extraction from Indian chromite overburden by solid state reduction and smelting route“. Journal of Mining and Metallurgy, Section B: Metallurgy 56, Nr. 2 (2020): 229–35. http://dx.doi.org/10.2298/jmmb190908007g.
Der volle Inhalt der QuelleAnnotation:
The present work demonstrates the extraction of nickel from low-grade chromite overburden by using solid state reduction and direct smelting route. Goethite & Quartz are present as major phases whereas chromite, hematite were identified as minor phases in the mineral. Solid state reduction of pellets were carried out inside a horizontal tube furnace at 1000?C, 1200?C, 1400?C for 30, 60, 90 and 120 minutes respectively with creating reducing atmosphere. Pellets of varying basicity (i.e. 0.5, 0.6, 0.7, 0.8 and 0.9) were used directly in the EAF for smelting studies. Highest percent of nickel (2%) having ~ 91% recovery were obtained in solid state reduction route for pellets which was reduced at 1400?C for 120 minute. Similar recovery (~90%) of nickel was obtained inside the ingot (0.67% Ni ) by using pellets of 0.9 basicity through smelting route. From the present investigation, it could be concluded that the solid state reduction as well as smelting routes are feasible for the recovery of nickel from low grade chromite overburden. The production of nickel pig (low grade ferronickel) could also be feasible by smelting route.
25
Skousen, J. G., und C. A. Call. „SOD-SEEDING LOW MAillTEIIAllCE PLANT SPECIES INTO COASTAL BERMIIDAGRASS SOD ON LIGNITE OVERBURDEN IN TEXAS“. Journal American Society of Mining and Reclamation 1985, Nr. 1 (1985): 18–23. http://dx.doi.org/10.21000/jasmr85010018.
Der volle Inhalt der Quelle
26
Ghavam-Nasiri, Ali, Abbas El-Zein, David Airey, R. Kerry Rowe und Abdelmalek Bouazza. „Numerical Simulation of Geosynthetic Clay Liner Desiccation under High Thermal Gradients and Low Overburden Stress“. International Journal of Geomechanics 19, Nr. 7 (Juli 2019): 04019069. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0001425.
Der volle Inhalt der Quelle
27
Hou, Jing Feng, Dong Ming Guo, Hui Dong Xu und Zeng Kun Yang. „Experimental Study on Impermeability and Frost Resistance of High Strength Concrete Used in Shaft of Coal Mine“. Advanced Materials Research 287-290 (Juli 2011): 1019–23. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1019.
Der volle Inhalt der QuelleAnnotation:
This paper presents results of impermeability and frost resistance tests of a series of high strength concrete which will be used in Yuncheng coal mine shaft lining. And the shaft is one of the most difficult to construct using freezing method because of the extreme thick overburden soil. The results show the impermeability and frost resistance of the selected concrete mix proportion options can meet the special requirements of the shaft construction. It’s due to the low water-cement ratio, admixture and water-reducing agent decreases void caused by excess water. And the composite mineral admixture forms bubbles to cut off the tiny water permeable channels in cement stone. Also the filling effect and pozzolanic effect caused by fly ash contribute a lot. The research on high strength concrete used in shaft of coal mine with thick overburden soil is still rare worldwide.
28
Rochlitz, Raphael, Matthias Queitsch, Pritam Yogeshwar, Thomas Günther, Andreas Chwala, Sascha Janser, Nina Kukowski und Ronny Stolz. „Capability of low-temperature SQUID for transient electromagnetics under anthropogenic noise conditions“. GEOPHYSICS 83, Nr. 6 (01.11.2018): E371—E383. http://dx.doi.org/10.1190/geo2017-0582.1.
Der volle Inhalt der QuelleAnnotation:
Transient electromagnetics (TEM) is a well-established method for mineral, groundwater, and geothermal exploration. Superconducting quantum interference device (SQUID)-based magnetic-field receivers used for TEM have quantitative advantages and higher sensitivity compared with commonly used induction coils. Special applications are deep soundings with target depths [Formula: see text] and settings with conductive overburden. However, SQUIDs have rarely been applied for TEM measurements in environments with significant anthropogenic noise. We compared a low-temperature SQUID with a commercially available induction coil in an area affected by anthropogenic noise. We acquired four fixed-loop data sets with totally 61 receiver stations close to Bad Frankenhausen, Germany. The high sensitivity of the SQUID enables low noise levels, which lead to longer high-quality transient data compared with the induction coil. The effect of anthropogenic and natural noise sources is more critical for the coil than for the SQUID data. In the vicinity of the transmitter loop, systematic distortion of the coil signals occurs at early times, most probably caused by sferic interferences. We have developed 1D inversion results of both receivers that matched well in general. However, the SQUID-based models were more consistent and showed greater depths of investigation. This led to a superior resolution of deeper layers and even enabled a potential detection of thin conducting targets at up to a 500 m depth. Moreover, we find that the SQUID data inversion revealed multidimensional effects within the conductive overburden. In this regard, we applied forward modeling to analyze systematic differences between inversion results of SQUID and coil data. We determine that low-temperature SQUIDs have the potential to significantly improve the reliability of subsurface models in suburban environments. Nevertheless, we recommend combined application of both types of receivers.
29
Deidda, G. P., und R. Balia. „An ultrashallow SH‐wave seismic reflection experiment on a subsurface ground model“. GEOPHYSICS 66, Nr. 4 (Juli 2001): 1097–104. http://dx.doi.org/10.1190/1.1487057.
Der volle Inhalt der QuelleAnnotation:
An SH‐wave seismic reflection experiment was conducted to evaluate the feasibility and cost effectiveness of reflection imaging ultrashallow targets commonly encountered in engineering, groundwater, and environmental investigations. It was carried out on a purpose‐built subsurface ground model consisting of a concrete layer, at a depth from 2.85–5 m, and a low‐velocity overburden (<80 and 150 m/s for S‐ and P‐waves, respectively), constituted of filling material, with the water table 2.60 m deep. High‐quality CDP data, acquired by using a 10‐kg sledgehammer and newly designed horizontal detectors, allowed us to obtain an extremely detailed stacked section with a minimal amount of processing. Uncertainty in determining the depth and horizontal dimensions of the concrete model was estimated to be 0.2 and 0.3 m, respectively; however, the dominant frequencies lower than 150 Hz, the low‐transmission coefficient at the upper interface, and the relatively high velocity (900 m/s) of the concrete layer prevented us from resolving the layer thickness. The experiment demonstrates that when overburden materials exhibit low velocities (a common condition in near surface), the SH‐wave seismic reflection method is a reliable, detailed, and cost‐effective technique to image ultrashallow targets, even in disturbed material and below the water table.
30
Ren, Shi Guang, Yong Ping Wu und Jian Hui Yin. „Research on Stability of Overburden Structure around Longwall Mining Face in Steeply Dipping Seam Group“. Applied Mechanics and Materials 724 (Januar 2015): 100–110. http://dx.doi.org/10.4028/www.scientific.net/amm.724.100.
Der volle Inhalt der QuelleAnnotation:
The steeply dipping seam group is defined by the two or more coal seams ,a pitch between 35°~55°. Using masonry beam theory, longitudinal bending theory and “R-S-F” dynamics control theory built a lower area overburden structure mode. Analysed the stability of low position coal seam. The balance requirement and the strength of the structure which is affected by the caving rock and lower coal roof were given. It easily generates two lower position steps rock structure in inclination along working face. Regular breaking of the second structure is the main reason leads to the imbalance of the structure between upper coal pillar and upper coal mining face.The interaction among multiple coal seam panels and overburden structures is the main reason that causes the rock disaster, the unbalance of the lower area may lead to pushing accident, the imbalance of the upper area can generate shock pressure.
31
Brower, K. R., und N. R. Morrow. „Fluid Flow in Cracks as Related to Low-Permeability Gas Sands“. Society of Petroleum Engineers Journal 25, Nr. 02 (01.04.1985): 191–201. http://dx.doi.org/10.2118/11623-pa.
Der volle Inhalt der QuelleAnnotation:
Abstract A problem in formation evaluation of tight gas sands is that their permeabilities are sometimes surprisingly sensitive to variations in overburden pressure. Photomicrographs of pore casts show an interconnected system of Photomicrographs of pore casts show an interconnected system of sheet pores, which are somewhat like the surfaces of a randomized honeycomb. A mathematical relation for predicting the pressure dependence of flow rate in sheet predicting the pressure dependence of flow rate in sheet pores has been derived from the dimensions of the pores pores has been derived from the dimensions of the pores and the elastic constants of the matrix. The equation has been validated by measurements on artificial media containing cracks of known dimensions in glass and concrete. The observed pressure sensitivity of the gas sands used in this study requires the aspect ratio of the pores (in this case, the ratio of average large dimensions to sheet thickness) to be greater than 100. Aspect ratios have been determined by taking the large dimension from photomicrographs of pore casts or grain size and the thickness photomicrographs of pore casts or grain size and the thickness from mercury injection pressure or the slope of a plot of apparent permeability vs. the reciprocal of mean gas pressure. The latter gives the diffusive contribution to gas pressure. The latter gives the diffusive contribution to gas flow from which the pore size can be calculated. The two methods for measuring pore size give satisfactory agreement. The aspect ratio's for the sheet pores in tight gas sands are large enough to explain the dependence of permeability on overburden pressure. permeability on overburden pressure. Introduction Sensitivity of permeability to overburden pressure is often a key factor in formation evaluation of tight gas sands. Gas permeability reductions of more than an order of magnitude have been observed in dry cores when overburden pressure is increased to typical formation values. Although this sensitivity to pressure has been related to the presence of clays and shales, the current consensus is that the pressure behavior of crack-shaped pores-i.e., pores characterized by two large dimensions and one small pores characterized by two large dimensions and one small one-is largely responsible. A similar conclusion was reached earlier by Fatt with respect to the less severe, but still significant, sensitivity exhibited by conventional sandstones. In this paper, the effect of pressure on pore structure and consequent changes in gas permeability pore structure and consequent changes in gas permeability are examined for a variety of natural and synthetic porous media. Pore Structure Pore Structure Pore Casts The pore structure of tight sands is revealed Pore Casts. The pore structure of tight sands is revealed in three dimensions by resin pore casts such as those shown in Fig. 1. The cast is prepared by injection of epoxy resin into the sample, followed by etching after the epoxy is set. Pore casts for over 20 samples, 12 of which were selected for the variety they provided in geologic character, typically showed sheet pores that are linked to give random polyhedra. Within this structure are distributed relatively large pore spaces commonly formed by solution of individual grains and cements. These spaces are often filled partially with matrix material. Inspection of pore casts before and after etching, and dun sections of samples containing injected resin, indicates that individual grains are largely bounded by sheet pores; individual polyhedra, seen in the pore cast, appear to be associated with individual grains or local regions bounded by grain surfaces. Thin sections generally show that, as a sediment is compacted over geologic time by pressure-solution and recrystallization processes, the grains fit pressure-solution and recrystallization processes, the grains fit together more and more snugly and may even fracture, but they maintain their individual identities with respect to neighboring grains. The polyhedral structure, therefore, is related strongly to grain size distribution. Contact Between Grains The ability of etchant, used in preparation of pore casts, to penetrate the sheet pores through many layers of particles may imply the existence of areas of cementation or direct contact between grains. However, from examination of sheet pores studied to date, the areas of actual contact between grains generally are difficult to identify from the pore casts and probably are small. For some sediments with permeability less than about 0.005 md, it was difficult to prepare satisfactory pore casts, possibly because the casts had very poor pore casts, possibly because the casts had very poor structural integrity or because the resin did not penetrate the space, if any, between grains. From our observations to date, it seems likely that most tight sands of potential commercial interest contain a network of polyhedral sheet pores that largely control permeability. pores that largely control permeability. Pore Thickness. Electron micrographs of the sheet pore Pore Thickness. Electron micrographs of the sheet pore edges, such as shown in Fig. Id, for sands of less than 1 md permeability, show their thicknesses to range typically from about 0.2 to 4 mu m. The lower limit may be related to difficulties of preparing casts of even finer cracks, since the presence of much smaller pores is indicated by mercury porosimetry and NMR measurements. Surface Area The two-dimensional network at the surface of the pore cast permits estimates of crack length per unit area to be made. These can be translated to approximations of crack surface area, Ac, per unit volume. SPEJ P. 191
32
Plastino, Wolfango, und Lauri Kaihola. „Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry“. Radiocarbon 46, Nr. 1 (2004): 97–104. http://dx.doi.org/10.1017/s0033822200039400.
Der volle Inhalt der QuelleAnnotation:
Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus™ has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.
33
Skrypnyk, O. O., N. S. Ostapenko und S. Kriuchkova. „The Reduction of Greenhouse Gas Emissions Through the Implementation of Low-carbon Technologies for the Use of Lands disturbed by Mining Operations“. Agrology 4, Nr. 2 (2021): 59–64. http://dx.doi.org/10.32819/021007.
Der volle Inhalt der QuelleAnnotation:
The climate change is a global environmental problem. Its solution requires thereduction of greenhouse gas emissions, especially CO2, as soon as possible. The developmentand implementation of low-carbon technologies can help in achievement this goal. Disturbedlands, which are a source of environmental pollution, can be used to reduce CO2 emissions. Wepropose to introduce technologies for locating solar and wind power plants on disturbed lands,primarily on mining dumps of overburden. The capacity of such solar and wind power plants canreplace thermal power plants, which generate the main volumes of CO2 emissions. Placing onthe mining dumps of overburden of solar power plants has advantages due to the use of southernexposures of the slopes. The wind power plants on the top of mining dumps of overburden takemore opportunities to use of wind speed by attracting additional height. Mining dumps haveemitted carbon dioxide due to the decomposition of limestone and the spontaneous combustion ofcarbon-containing rocks. Counteraction of CO2 emissions by coating the surface with inert materialsthat block the access of moisture and acid solutions to hazardous rocks is proposed. The useof new technologies for the rehabilitation of disturbed lands through the formation of secondaryecosystems creates opportunities to reduce greenhouse gas emissions. This have avoids additionalCO2 emissions during the operation of machines and mechanisms at the mining–technicaland biological stages of reclamation. Secondary soils able to accumulate carbon in the form oforganic matter up to 11 t / ha for 30–50 years. The study of technogenic soils formation on loess-like loams in the landscape reserves “Vizyrka” (Inguletsky GOK), “Hrushivka” (MarganetskyGOK), “Vershina” (Prosyansky GOK) are have evidenced of this facts. Plant components of ecosystemshave even more opportunities. Secondary vegetation absorbs CO2 from the atmosphereduring photosynthesis, creates the coating of surface of lands disturbed by mining operations.Clover plant group show the greatest ability to accumulate carbon (up to 57 t/ha per year). Theresearch was carried out at the research area of Inguletsky GOK. Our assessment testifies that theintegrated application of the above technologies will reduce emissions in Kryvbas by 95 milliontons of CO2 per year. The work was carried out under the target program of the National Academyof Sciences of Ukraine “Scientific and technical and economic and ecological foundations oflow-carbon development of Ukraine”.
34
Hamdani, Ahmad Helman, Johanes Hutabarat und Agus Didit Haryanto. „The Acid-Base Accounting (ABA) of Overburden Rock to Predict Acid Mine Water in Kasai Coal Mining, Indonesia“. Oriental Journal of Chemistry 35, Nr. 3 (20.05.2019): 1103–11. http://dx.doi.org/10.13005/ojc/350325.
Der volle Inhalt der QuelleAnnotation:
The Acid-Base Accounting (ABA) and TCLP methods from overburden samples collected from the coal mine in Kasai were undertaken to predict pre-mining acid mine water quality. Maximum potential acidity (MPA), acid neutralization capacity (ANC), net acid generation (NAG), net acid producing potential (NAPP) and ANC/MPA ratios were determined on the Acid-Base Accounting (ABA) protocol. Most of the samples from KS-10, KS-11 and KS-12 show the pH of NAG of overburden ranges from 5.53–7.86 negatively net acid neutralization potential (NAPP). The ANC/MPA ratio varied from 1.09–26.60 and is classified as non-acid-forming except at an interval depth of 7.00–9.00 m in KS-12, where it is classified as uncertainty. The potentially acid mine water detected in KS-39 at an interval depth of 16.00–36.00 m was classified as potential acid forming (PAF), indicated by a positive NAPP, a low ratio of ANC/MPA (below 1.0) and high dissolved metal iron.
35
ISHIKAWA, Tatsuya, Ippei KIJIYA, Tetsuya TOKORO und Satoshi AKAGAWA. „ESTIMATION OF FROST HEAVE RATIO OF SOILS IN CONTEMPLATION OF MATRIC SUCTION UNDER LOW OVERBURDEN PRESSURE“. Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 70, Nr. 3 (2015): I_65—I_70. http://dx.doi.org/10.2208/jscejpe.70.i_65.
Der volle Inhalt der Quelle
36
Bello, Rereloluwa, und Toluwaleke Ajayi. „Geoelectric evaluation of groundwater potential within sunshine garden estate, akure southwestern Nigeria“. International Journal of Physical Research 7, Nr. 2 (22.07.2019): 61. http://dx.doi.org/10.14419/ijpr.v7i2.29172.
Der volle Inhalt der QuelleAnnotation:
The Vertical Electrical Resistivity surveys in the Sunshine Garden Estate have contributed to a better understanding of the basement complex of Southwestern Nigeria. Nine (9) vertical electrical sounding (VES) using the Schlumberger electrode array were interpreted and the results shows three (3) subsurface geoelectric layers within the study area. These are the weathered layer, topsoil, fresh/fractured basement. Groundwater pockets such as fractured zones, valley fills/basement depressions, and weathered zones were delineated in the study area. Weathered/partially weathered layer and weathered basement/fractured basement were the two major aquifer mapped out and these aquifers are characterized by thick overburden, found within basement depressions. The groundwater potential of the study area was zoned into low, medium and high potentials. Zones where the overburden thickness (which constitutes the main aquifer unit) is greater than 13m and of low clay composition (average resistivity value between 200 - 400Ωm) are considered zones of high groundwater potential. Area where the thickness of the aquifer ranges from 11-13m with less clay composition are considered to have medium groundwater potential and the areas where the thickness of the aquifer is less than 11m are considered to have a low groundwater. The VES station underlained by high and medium groundwater potential zones are envisaged to be viable for groundwater development within the area.
37
Mosseler, A., und J. E. Major. „Coppice growth responses of two North American willows in acidic clay soils on coal mine overburden“. Canadian Journal of Plant Science 94, Nr. 7 (September 2014): 1269–79. http://dx.doi.org/10.4141/cjps-2014-046.
Der volle Inhalt der QuelleAnnotation:
Mosseler, A. and Major, J. E. 2014. Coppice growth responses of two North American willows in acidic clay soils on coal mine overburden. Can. J. Plant Sci. 94: 1269–1279. Acid-generating mine spoils with low pH are a major problem for revegetation and site reclamation. We compared growth responses of 15 genotypes from two widespread willow species, Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI), native to eastern and central North America on two adjacent coal mine spoil sites that differed strongly in both pH (3.6 vs. 6.8) and soil texture. Despite significantly poorer growth responses for several coppice biomass traits on a highly acidic clay deposit compared with adjacent shale overburden, these willow clones demonstrated a surprising tolerance for extremely acidic soil conditions. Analysis of survival and growth uncovered genotype×environment interactions, indicating that both species and genotypic differences within species could be used to select better-adapted genotypes for extreme conditions. Most ERI and DIS clones grew comparatively better on the shale overburden site, but two of eight ERI clones and one of seven DIS clones grew significantly better on the acidic clay site, indicating the possibility for clonal selection for specific site adaptations within a species. Allometric relationships between coppice height and basal stem diameter were constant at both the species and site levels. However, there was a divergence of height and diameter in their relationship with green mass yields on the two different site types.
38
Dooley, Tim P., Michael R. Hudec, Dan Carruthers, Martin P. A. Jackson und G. Luo. „The effects of base-salt relief on salt flow and suprasalt deformation patterns — Part 1: Flow across simple steps in the base of salt“. Interpretation 5, Nr. 1 (01.02.2017): SD1—SD23. http://dx.doi.org/10.1190/int-2016-0087.1.
Der volle Inhalt der QuelleAnnotation:
Passive margins underlain by a salt detachment are typically interpreted as kinematically linked zones of updip extension and downdip contraction separated by a zone of translation above a smoothly dipping base of salt. However, salt flow is affected by the base-of-salt geometry across which it flows, and early-stage gravity gliding induced by basin tilt may be complicated by the presence of salt-thickness changes caused by the pre-existing base-salt relief. We investigate these effects using physical models. Dip-parallel steps generate strike-slip fault zones separating domains of differential downslope translation and structural styles, provided the overburden is thin enough. If the overburden is thicker, it resists breakup, but a change in the structural trend occurs across the step. Steps with mild obliquity to the dip direction produce transtensional and transpressional faults in the cover separating structural domains. Deformation complexity in the overburden increases where base-salt steps strike at a high angle to salt flow, and it is especially dependent on the ratio between the thick ([Formula: see text]) and thin ([Formula: see text]) salt across the step at the base of salt. Where the salt-thickness ratio ([Formula: see text]) is high, basal drag generates major flux mismatches, resulting in a contractional thickening of the salt and associated overburden shortening in thin salt above a base-salt high block. Shortening is transient and superseded by extension as the salt thickening allows the flow velocity to increase. When transitioning off a base-salt high block into a low block, the greater flux within the thick salt results in a monocline with extensional and contractional hinges. Structures are further deformed as they translate through these hinge zones. Our physical models demonstrate that extensional diapirs and compressional fold belts can be initiated anywhere on a slope as the salt accelerates and decelerates across base-salt relief. A fold belt from the Campos Basin, offshore Brazil, is used to illustrate these processes.
39
Lozynskyi, O. Ye, und V. O. Lozynskyi. „Geological-Field Simulation of the "Well – Formation" System for Low-permeable Reservoirs“. Prospecting and Development of Oil and Gas Fields, Nr. 3(72) (30.09.2019): 51–57. http://dx.doi.org/10.31471/1993-9973-2019-3(72)-51-57.
Der volle Inhalt der QuelleAnnotation:
The aim of the research is the creation of an algorithm and a computer program to study the feasibility of poor wells developing. The research method is hydrodynamic simulation of the “well – formation” system by studying the behavior of low-permeable oil-filled reservoirs in the process of creating rising overburdens on the formation (abnormal formation pressures). Geological factors limiting the productivity of an oil well are analyzed. The degree of the decrease of the negative effect of these factors on oil influx to the bottomhole is predicted. The authors have studied the possibility of creating supplementary filtering channels in the bottomhole zone and the possibility of increasing hydroconductivity of the exposed reservoirs within the maximum possible drainage area. The authors also suggest the method to study poor wells using multiple injection of fluid into the reservoir and a gradual increase of the injection pressure and the overburden on the formation. In order to simulate the bottomhole pressure drop in a multi-cycle study, the authors make an algorithm based on an equation linking the pressure at a certain time point after the well shut-in to record the pressure decline curve with an integrated indicator. This indicator takes into account the volume of injection of fluid into the reservoirs before the well shut-in, the total duration of the injection of fluid into the reservoirs, the duration of time from the beginning of the injection of fluid into the reservoirs till the end of the process and the coefficient of the reservoir conductivity at each research cycle. The developed algorithm and computer technology provide the accumulation, storage, processing and reproduction of objective geological-field information. This will give a possibility to make a grounded decision about taking measures to increase the influx of production to the wells. The final result of these measures will be the transfer of out-balance reserves in the drainage areas of the wells to balance reserves and an increase in the total oil production at the field.
40
An, Ni, Yu-Jun Cui, Nathalie Conil, Jean Talandier und Sebastien Conil. „Soil–atmosphere interaction in the overburden of a short-lived low and intermediate level nuclear waste (LLW/ILW) disposal facility“. Computers and Geotechnics 124 (August 2020): 103610. http://dx.doi.org/10.1016/j.compgeo.2020.103610.
Der volle Inhalt der Quelle
41
Zhao, Lei, und Greg You. „Brown Coal in Victoria, Australia and Maddingley Brown Coal Open Cut Mine Batter Stability“. Journal of Civil Engineering and Construction 9, Nr. 3 (15.08.2020): 109–18. http://dx.doi.org/10.32732/jcec.2020.9.3.109.
Der volle Inhalt der QuelleAnnotation:
Brown coal is young, shallowly deposited, and widely distributed in the world. It is a fuel commonly used to generate electricity. This paper first reviews the resources and characteristics of brown coal in Victoria, Australia, and its exploitation and contribution to the economy or power supply in Victoria. Due to the shallow depth of the brown coal seam, e.g. very favorable stripping ratio, open pit mining is the only mining method used to extract the coal at low cost for power generators. With the large-scale mining operations, cases of batter failure were not rare in the area. From the comprehensive review of past failures, overburden batter tends to fail by circular sliding, coal batter tends to fail by block sliding after the overburden is stripped due to a weak water-bearing layer underneath the coal seam and tension cracks developed at the rear of the batter, and batter failure is typically coincided with peak raining seasons. Secondly, the paper reviews the case study of Maddingley Brown Coal (MBC) Open Cut Mine batter stability, including geology, hydrogeology, and hydro-mechanically coupled numerical modelling. The modelling employs three-dimensional finite element method to simulate the MBC northern batter where cracks were observed in November 2013. The comprehensive simulation covers an overburden batter, a brown coal batter, two rainfall models, and a buttressed batter. The simulated results agree well with observed data, and it is found that the rainfall at the intensity of 21mm substantially lowered the factor of safety of the coal batter.
42
Wojtanowicz, A. K., und D. Zhou. „Borehole Failure Resulting From Formation Integrity (Leak-Off) Testing in Upper Marine Sediments Offshore“. Journal of Energy Resources Technology 120, Nr. 2 (01.06.1998): 111–17. http://dx.doi.org/10.1115/1.2795020.
Der volle Inhalt der QuelleAnnotation:
This paper presents the results of a theoretical study, supported with the finite element analysis, into potential loss of external integrity around a casing shoe resulting from leak-off testing (LOT) in upper marine sediments (UMS). Three types of possible failures from LOTs were considered: vertical fracture, horizontal fracture, and a channel outside cemented annulus. It is proved in the paper that vertical fracture is the most unlikely failure of the three. The other two types of failure can be distinguished by different values of propagation pressures. Although horizontal fractures are initiated at low pressure in the plastic zone around the wellbore, they cannot propagate beyond the plastic zone until wellbore pressures exceed overburden pressures. Annular channels, on the other hand, may propagate upwards at pressures lower than overburden pressure. The paper shows that these channels are initiated at pressures equal to the contact stress between cement and rock and their propagation pressures are on average 3.5-fold greater than contact stress. It is also explained how to identify the UMS with high risk of annular channeling during LOTs.
43
Chen, Liang, Shaowu Fan, Can Zhao, Lang Zhang und Zhiheng Cheng. „Calculation Method of Overburden Damage Height Based on Fracture Mechanics Analysis of Soft and Hard Rock Layers“. Geofluids 2019 (27.02.2019): 1–15. http://dx.doi.org/10.1155/2019/3790264.
Der volle Inhalt der QuelleAnnotation:
Under the geological condition of soft and hard rock interaction stratum, the overburden damage height can provide a quantitative support for the design of the locations of gas drainage boreholes in the roof mining fracture zone and the determination of the hydraulic fracture zone in coal seam mining. The interbedded structure of overlying mud rock and sandstone in the Lu’an mining area in Shanxi is a typical soft and hard rock interaction stratum. In view of the lack of soft rock fracture mechanics analysis and the improper calculation of the damage height of overburden rock caused by constant rock residual bulking coefficient to be used regularly in the analysis, in this paper, we constructed a fracture model of soft and hard strata by giving a quantitative classification criterion of soft and hard rocks and introducing a fracture failure criterion of soft rock strata and the space constraint condition of broken-expansion rock formation. Aiming at improving the calculation precision of overburden damage height, we presented a calculation method based on fracture mechanics analysis of soft and hard strata, which could delineate the extent of intact rock in overlying strata from bottom to top to determine the damage height of overburden rock. This research took Yuwu coal mine in Lu’an mining area as an example. Results showed that (1) by the calculation method, the overburden damage height of the N1102 fully mechanized caving face in Yuwu coal mine was 51.44 m, which was less than the value obtained by an actual borehole TV method as well as the numerical simulation result of 53.46 m, with a calculation accuracy about 96.22%, which is quite high for both. The calculation accuracy of the proposed method was higher than that of the three conventional theoretical methods, and it effectively solved the limitation of the fracture analysis method without the inclusion of the soft rock layer in design and the distortion problem due to the residual bulking coefficient to be improperly used in simulation. (2) There was no noticeable fractures in the broken soft rock zone, and the whole fractures were mainly low-angle rupture; the fractures in hard rock layer had obvious ruptures and multiangle cracks, and the average fracture width of soft rock was 2.8 mm smaller than that of hard rock. The fracture modes of soft rock and hard rock were mainly tensile failure and tensile shear failure, which verified the correctness of the fracture mechanics model of soft and hard rock layers constructed in this paper. (3) It is noticed that the tensile strength of rock in this method needs to be obtained through rock mechanics experiment on overlying strata in the study area, and our proposed method was applicable to the mining conditions of near horizontal coal seam. The calculation accuracy of this method meets the engineering error requirements and can be applied to the prediction of overburden damage height in near horizontal coal seam mining.
44
Selyukov, A. V. „THE EFFICIENCY OF DUMPING LOW-PROFILE EXTERNAL OVERBURDEN DUMP IN OPEN COAL MINING IN THE KEMEROVO REGION“. MINING INFORMATIONAL AND ANALYTICAL BULLETIN 12, Nr. 38 (2017): 120–27. http://dx.doi.org/10.25018/0236-1493-2017-12-38-120-127.
Der volle Inhalt der Quelle
45
Adabanija, M. A., und R. A. Ajibade. „Investigating groundwater corrosion and overburden protective capacity in a low latitude crystalline basement complex of southwestern Nigeria“. NRIAG Journal of Astronomy and Geophysics 9, Nr. 1 (01.01.2020): 245–59. http://dx.doi.org/10.1080/20909977.2020.1723867.
Der volle Inhalt der Quelle
46
Johnston, H. M., R. W. Gillham und J. A. Cherry. „Distribution coefficients for strontium and cesium in overburden at a storage area for low-level radioactive waste“. Canadian Geotechnical Journal 22, Nr. 1 (01.02.1985): 6–16. http://dx.doi.org/10.1139/t85-002.
Der volle Inhalt der QuelleAnnotation:
Distribution coefficients for strontium and cesium, as one component of a hydrogeological site investigation, were determined by the batch method on 12 samples of glacial till and 7 samples of sand from the radioactive waste operations site 2 of the Bruce Nuclear Power Development. The tests were performed using two types of equilibrating solutions traced with radioisotopes; one was a solution with cation concentrations equal to the concentrations obtained in 1:1 solid–solution extracts and the other was natural groundwater obtained from piezometers at or near the depths from which the soil samples were obtained. The measured Kd values were relatively uniform within an individual hydrogeological unit, and differences between units were related to the chemical properties of both the solid and solution phases. The Kd values for both Sr and Cs obtained in the tests performed using the synthetic solutions differed from those obtained in tests using natural groundwater. The differences appeared to be related to the major chemistry of the test solutions and indicated that, to obtain Kd values that were most representative of the in situ conditions, natural groundwater should be used in the batch procedure.The measured Kd values, when used in the linear retardation equation, indicated that in the till materials, 90Sr would migrate at a rate no greater than 0.2 cm∙year−1 and 137Cs would migrate at a rate no greater than 0.001 cm∙year−1. Based on the relatively high Kd value for Cs in the sand (300 mL∙g−1), 137Cs migration through the sand unit would be of little environmental concern. On the other hand, the relatively low Kd for Sr (2 mL∙g−1) indicates that attention should be paid to the pathway role of the sand layer in any assessment of the isolation capability of the site.
47
Coetzee, A., und A. F. M. Kisters. „Spatial variations of sills and implications for magma dispersal across the Karoo basin“. South African Journal of Geology 123, Nr. 4 (26.10.2020): 511–30. http://dx.doi.org/10.25131/sajg.123.0035.
Der volle Inhalt der QuelleAnnotation:
Abstract Dolerite sill complexes of the Karoo Large Igneous Province (ca. 183 Ma) show systematic variations in emplacement style and size throughout the Karoo basin. These variations are explained in terms of three main, interrelated factors, namely the overburden thickness or emplacement depth, variations in host rock rigidities as a result of sedimentary facies changes in the Karoo basin, and proximity to magma feeders. In the northern parts of the thinner (<500 m) and more coarse-clastic Karoo stratigraphy, sills intrude preferentially below more rigid sandstone horizons that acted as stress barriers causing the arrest of magma ascent and lateral spreading below sandstone beds. The low overburden promotes roof uplift above sills and associated brittle faulting can initiate the formation of inclined sheets that limits the lateral propagation path of inner sills. Roof uplift is further promoted by the proximity to magma feeders in the basement and resulting variations in magma pressure that control the spreading rate and inflation of sills. Localised dyke networks spaced at regular intervals and rooted in underlying sills reflect the stretching of roof rocks above inflating sills. The combination of these effects results in relatively small (<10 km) diameters of sills in the northern parts of the basin. Sills emplaced at intermediate depths (ca. 700 m) in the central Karoo basin are marked by larger diameters (>30 km) and thicknesses of up to 100 m. This reflects the higher overburden pressures and the delay of roof failure and subsequent formation of inclined sheets. Dyke networks in the roof of these sills become more irregular and non-systematic at these greater depths. At even greater depths of up to 2 km in the southern parts of the Karoo basin, mega-sills reach diameters of 50 to 80 km, but thicknesses of only up to 35 m. Thick shale-rich sequences in the southern Karoo basin facilitate sill emplacement through internal host-rock deformation and ductile flow. The thicker overburden and different host rock rigidity delay or suppress roof failure and formation of inclined sheet, thus allowing for the lateral propagation of sills. The deeper-seated sills are typically not associated with local dyke networks.
48
Rokich, Deanna P., Kathy A. Meney, Kingsley W. Dixon und K. Sivasithamparam. „The impact of soil disturbance on root development in woodland communities in Western Australia“. Australian Journal of Botany 49, Nr. 2 (2001): 169. http://dx.doi.org/10.1071/bt00015.
Der volle Inhalt der QuelleAnnotation:
The impact of soil disturbance of the Banksia woodland soil profile and particularly the effect of different reconstructed soil profiles (overburden profile, white profile and yellow profile) and soil ripping within rehabilitation sites, was investigated in terms of root development and architecture for eight species that are key structural elements in Banksia woodland. The aim was to determine the soil environment best suited for root development and architecture likely to contribute to high seedling survival in post-mined sites. Root development and architecture differed significantly between native woodland, and rehabilitation sites. In general, roots were longer in native woodland with low lateral root production (for all species studied) compared to rehabilitation sites where the roots were shorter, tended to divide or lose geotrophy and consisted of numerous laterals. When comparing the different soil profiles in the rehabilitation sites, the commonly reconstructed profile of ‘topsoil over overburden’ (overburden profile) was the least favourable for root development and architecture. Ripping of the soil to 80 cm depth had a positive effect on root growth. There were differences between native woodland and rehabilitation sites, in soil impedance, soil bulk density, soil moisture percentage and organic carbon content. In general, reconstructed soils in rehabilitation sites have (1) soil impedance and soil bulk density values likely to seriously impede root development and architecture, (2) soil moisture percentages higher than those in undisturbed woodland during all months of monitoring and at most depths down to 40 cm and (3) lower organic carbon content than native woodland. When comparing the different soil profiles in rehabilitation sites, the overburden profile (a) had the highest impedance values, (b) was one of the profiles with the highest bulk density values and (c) had the highest soil moisture percentages during most months and at most depths examined. Ripping the soil decreased soil impedance and soil moisture contents. The major conclusion from this study is that soil impedance, which influences water movement, is a key characteristic of soil conditions that are not conducive to the development of deep penetrating root systems. These deep root systems may be directly linked to survival.
49
Neff, Peter D. „A review of the brittle ice zone in polar ice cores“. Annals of Glaciology 55, Nr. 68 (2014): 72–82. http://dx.doi.org/10.3189/2014aog68a023.
Der volle Inhalt der QuelleAnnotation:
AbstractMaintaining ice-core quality through the brittle ice zone (BIZ) remains challenging for polar ice-core studies. At depth, increasing ice overburden pressurizes trapped air bubbles, causing fracture of cores upon exposure to atmospheric pressure. Fractured ice cores degrade analyses, reducing resolution and causing contamination. BIZ encounters at 18 sites across the Greenland, West and East Antarctic ice sheets are documented. The BIZ begins at a mean depth of 545 ± 162 m (1 standard deviation), extending to depths where ductile clathrate ice is reached: an average of 1132 ± 178 m depth. Ice ages in this zone vary with snow accumulation rate and ice thickness, beginning as young as 2 ka BP at Dye-3, Greenland, affecting ice >160 ka BP in age at Taylor Dome, Antarctica, and compromising up to 90% of retrieved samples at intermediate-depth sites. Effects of pressure and temperature on the BIZ are explored using modeled firn-column overburden pressure and borehole temperatures, revealing complex associations between firn densification and BIZ depth, and qualitatively supporting expected thinning of the BIZ at low ice temperatures due to shallower clathrate stability. Mitigating techniques for drilling, transport, sampling and analysis of brittle ice cores are also discussed.
50
Birt, Christopher, Danang Priyambodo, Simon Wolfarth, Johnathan Stone und Ted Manning. „The value of high-density blended OBN seismic for drilling and reservoir description at the Tangguh gas fields, Eastern Indonesia“. Leading Edge 39, Nr. 8 (August 2020): 574–82. http://dx.doi.org/10.1190/tle39080574.1.
Der volle Inhalt der QuelleAnnotation:
The Tangguh gas fields in Eastern Indonesia are overlain by a complex overburden, including a thick, heavily faulted, and intensely karstified carbonate interval that tends to scatter and attenuate seismic energy. Development drilling is challenging, with the potential for pack-offs and stuck pipe when drilling into unstable, partially collapsed caves or karstified fault planes while on total losses. Ideally, these karst features are to be avoided when planning and drilling wells, but avoiding them depends on having a well-resolved seismic image. Historical towed-streamer and sparse ocean-bottom cable seismic is low fold and does not give a satisfactory image for well planning. Advances in ocean-bottom node technology, computer processing, and capacity coupled with efficient survey design and blended acquisition utilizing multiple source vessels allowed a step change in data density. This provided a new high-quality seismic image to support future development activities. The advantages of densely sampled, full-azimuth data include rapid delivery of fast-track products (because high-quality images can be constructed with relatively simple processing flows), greatly improved overburden imaging, and a corresponding uplift in deeper imaging leading to enhanced reservoir characterization.