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991.
Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock,
but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact,
and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced
ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration.
The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a
screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration,
namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in
two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were
analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness
of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes,
distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used
as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with
and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier
transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method
of blast-induced waves was considerably effective under certain design conditions. The design details for field application
have also been proposed. 相似文献
992.
Jen-Chen Fan Che-Hsin Liu Chih-Hsiang Yang Hsiao-Yu Huang 《Environmental Geology》2009,57(7):1509-1519
In this study, soil samples collected from the sides of two streams with high debris flow potential at Shenmu and Fengchiou
village in Nantou County, Taiwan, were used for seepage tank tests in the laboratory. While the tests were being conducted,
observations were made to investigate the relationships among displacement of the slope, quality of the seepage water and
occurrence of mass movement. The results showed that according to the change rate, displacement could be divided into two
stages, namely, the initial failure displacement stage and primary failure displacement stage. While the displacement of the
slope was in primary failure displacement stages, the probability of slope failure became much higher. Before general slope
failure, electrical conductivity (EC) and sulfate ion (SO4
2−) concentration of the seepage water increased significantly. The time when EC of the seepage water started to increase rapidly
was much earlier than that when displacement of the slope started to increase significantly. Therefore, from the hazard mitigation
view, there will be a longer time for response if EC of the seepage water was monitored. 相似文献
993.
Pan Wu Changyuan Tang Congqiang Liu Lijun Zhu TingQuan Pei Lijuan Feng 《Environmental Geology》2009,57(7):1457-1467
The chemical characteristics, formation and natural attenuation of pollutants in the coal acid mine drainage (AMD) at Xingren
coalfield, Southwest China, are discussed in this paper based on the results of a geochemical investigation as well as geological
and hydrogeological background information. The chemical composition of the AMD is controlled by the dissolution of sulfide
minerals in the coal seam, the initial composition of the groundwater and the water–rock interaction. The AMD is characterized
by high sulfate concentrations, high levels of dissolved metals (Fe, Al, Mn, etc.) and low pH values. Ca2+ and SO4
2− are the dominant cation and anion in the AMD, respectively, while Ca2+ and HCO3
− are present at significant levels in background water and surface water after the drainage leaves the mine site. The pH and
alkalinity increase asymptotically with the distance along the flow path, while concentrations of sulfate, ferrous iron, aluminum
and manganese are typically controlled by the deposition of secondary minerals. Low concentrations of As and other pollutants
in the surface waters of the Xingren coalfield could be due to relatively low quantities being released from coal seams, to
adsorption and coprecipitation on secondary minerals in stream sediments, and to dilution by unpolluted surface recharge.
Although As is not the most serious water quality problem in the Xingren region at present, it is still a potential environmental
problem.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
994.
Stabilization of Expansive Clays Using Granulated Blast Furnace Slag (GBFS) and GBFS-Cement 总被引:1,自引:0,他引:1
Expansive clays undergo swelling when subjected to water. This can cause damage, especially to light weight structures, water
conveyance canals, lined reservoirs, highways, and airport runways unless appropriate measures are taken. In this study, granulated
blast furnace slag (GBFS) and GBFS-cement (GBFSC) were utilized to overcome or to limit the expansion of an artificially prepared
expansive soil sample (sample A). GBFS and GBFSC were added to sample A in proportions of 5–25% by weight. The effects of
these stabilizers on grain size distribution, Atterberg limits, swelling percentage and rate of swell of soil samples were
determined. GBFS and GBFSC were shown to successfully decreasing the total amount of swell while increasing the rate of swell. 相似文献
995.
Marleen Coetsiers Petra Blaser Kristine Martens Kristine Walraevens 《Environmental Geology》2009,57(5):1155-1168
Aquifers from the same typology can have strongly different groundwater chemistry. Deducing the groundwater quality of less
well-characterized aquifers from well-documented aquifers belonging to the same typology should be done with great reserve,
and can only be considered as a preliminary approach. In the EU’s 6th FP BRIDGE project “Background cRiteria for the IDentification
of Groundwater thrEsholds”, a methodology for the derivation of threshold values (TV) for groundwater bodies is proposed.
This methodology is tested on four aquifers in Flanders of the sand and gravel typology. The methodology works well for all
but the Ledo-Paniselian aquifer, where the subdivision into a fresh and saline part is disproved, as a gradual natural transition
from fresh to saline conditions in the aquifer is observed. The 90 percentile is proposed as natural background level (NBL)
for the unconfined Pleistocene deposits, ascribing the outliers to possible influence of pollution. For the Tertiary aquifers,
high values for different parameters have a natural origin and the 97.7 percentile is preferred as NBL. The methodology leads
to high TVs for parameters presenting low NBL, when compared to the standard used as a reference. This would allow for substantial
anthropogenic inputs of these parameters. 相似文献
996.
Mineralization of pegmatites in parts of the Oban Massif, Southeastern Nigeria: A preliminary analysis 总被引:1,自引:0,他引:1
The Oban Basement Massif of southeastern Nigeria is composed of metamorphosed rocks including phyllites, schists, gneisses and amphibolites cut by pegmatitic dykes of varying length and thickness, which intruded the metamorphic rocks. Preliminary geochemical study and analysis of these pegmatites from western Oban Massif at Uyanga, Akwa Ibami, Iwuru I, Iwuru Ⅱ and Igbofia showed that the pegmatites are highly albitized. This is incon-sistent with earlier postulations that the pegmatites in this part of Nige... 相似文献
997.
Thomas M. Soniat Eileen E. Hofmann John M. Klinck Eric N. Powell 《International Journal of Earth Sciences》2009,98(1):99-114
The eastern oyster (Crassostrea virginica) is affected by two protozoan parasites, Perkinsus marinus which causes Dermo disease and Haplosporidium nelsoni which causes MSX (Multinucleated Sphere Unknown) disease. Both diseases are largely controlled by water temperature and salinity and thus are potentially sensitive to climate variations resulting from the El Niño-Southern Oscillation (ENSO), which influences climate along the Gulf of Mexico coast, and the North Atlantic Oscillation (NAO), which influences climate along the Atlantic coast of the United States. In this study, a 10-year time series of temperature and salinity and P. marinus infection intensity for a site in Louisiana on the Gulf of Mexico coast and a 52-year time series of air temperature and freshwater inflow and oyster mortality from Delaware Bay on the Atlantic coast of the United States were analyzed to determine patterns in disease and disease-induced mortality in C. virginica populations that resulted from ENSO and NAO climate variations. Wavelet analysis was used to decompose the environmental, disease infection intensity and oyster mortality time series into a time–frequency space to determine the dominant modes of variability and the time variability of the modes. For the Louisiana site, salinity and Dermo disease infection intensity are correlated at a periodicity of 4 years, which corresponds to ENSO. The influence of ENSO on Dermo disease along the Gulf of Mexico is through its effect on salinity, with high salinity, which occurs during the La Niña phase of ENSO at this location, favoring parasite proliferation. For the Delaware Bay site, the primary correlation was between temperature and oyster mortality, with a periodicity of 8 years, which corresponds to the NAO. Warmer temperatures, which occur during the positive phase of the NAO, favor the parasites causing increased oyster mortality. Thus, disease prevalence and intensity in C. virginica populations along the Gulf of Mexico coast is primarily regulated by salinity, whereas temperature regulates the disease process along the United States east coast. These results show that the response of an organism to climate variability in a region is not indicative of the response that will occur over the entire range of a particular species. This has important implications for management of marine resources, especially those that are commercially harvested. 相似文献
998.
Alexandre Lisboa Lago Vagner Roberto Elis Welitom Rodrigues Borges Giovanni Chaves Penner 《Environmental Geology》2009,58(2):407-417
Geophysics has been shown to be effective in identifying areas contaminated by waste disposal, contributing to the greater efficiency of soundings programs and the installation of monitoring wells. In the study area, four trenches were constructed with a total volume of about 25,000 m3. They were almost totally filled with re-refined lubricating oil waste for approximately 25 years. No protection liners were used in the bottoms and laterals of the disposal trenches. The purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar (GPR) methods in characterizing the contamination of this lubricant oil waste disposal area in Ribeirão Preto, SP, situated on the geological domain of the basalt spills of the Serra Geral Formation and the sandstones of the Botucatu Formation. Geophysical results were shown in 2D profiles. The geophysical methods used enabled the identification of geophysical anomalies, which characterized the contamination produced by the trenches filled with lubricant oil waste. Conductive anomalies (smaller than 185 Ωm) immediately below the trenches suggest the action of bacteria in the hydrocarbons, as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature. It was also possible to define the geometry of the trenches, as evidenced by the GPR method. Direct sampling (chemical analysis of the soil and the water in the monitoring well) confirmed the contamination. In the soil analysis, low concentrations of several polycyclic aromatic hydrocarbons (PAHs) were found, mainly naphthalene and phenanthrene. In the water samples, an analysis verified contamination of the groundwater by lead (Pb). The geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area, and could be applied in the study of similar areas. 相似文献
999.
Steven Creighton Thomas Stachel Sergei Matveev Heidi Höfer Catherine McCammon Robert W. Luth 《Contributions to Mineralogy and Petrology》2009,157(4):491-504
The oxidation state, reflected in the oxygen fugacity (fO2), of the subcratonic lithospheric mantle is laterally and vertically heterogeneous. In the garnet stability field, the Kaapvaal
lithospheric mantle becomes progressively more reducing with increasing depth from Δlog fO2 FMQ-2 at 110 km to FMQ-4 at 210 km. Oxidation accompanying metasomatism has obscured this crystal-chemical controlled depth-fO2 trend in the mantle beneath Kimberley, South Africa. Chondrite normalized REE patterns for garnets, preserve evidence of
a range in metasomatic enrichment from mild metasomatism in harzburgites to extensive metasomatism by LREE-enriched fluids
and melts with fairly unfractionated LREE/HREE ratios in phlogopite-bearing lherzolites. The metasomatized xenoliths record
redox conditions extending up to Δlog fO2 = FMQ, sufficiently oxidized that magnesite would be the stable host of carbon in the most metasomatized samples. The most
oxidized lherzolites, those in or near the carbonate stability field, have the greatest modal abundance of phlogopite and
clinopyroxene. Clinopyroxene is modally less abundant or absent in the most reduced peridotite samples. The infiltration of
metasomatic fluids/melts into diamondiferous lithospheric mantle beneath the Kaapvaal craton converted reduced, anhydrous
harzburgite into variably oxidized phlogopite-bearing lherzolite. Locally, portions of the lithospheric mantle were metasomatized
and oxidized to an extent that conversion of diamond into carbonate should have occurred.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
1000.
Yanxin Wang Teng Ma B. N. Ryzhenko O. A. Limantseva E. V. Cherkasova 《Geochemistry International》2009,47(7):713-724
Mineral equilibria were analyzed in the system As-bearing rock-meteoric water. It was shown that carbonate rocks are the most probable source of As and Sr in the waters of the Datong Basin (People's Republic of China). The reason for groundwater enrichment in As is the shift of the equilibrium FeCO3 (siderite) + H2O = FeOOH(goethite) + CO2(g) + H2(g) to the left (toward siderite formation) owing to organic matter oxidation by atmospheric oxygen and an increase in the equilibrium partial pressure of CO2, while the Eh of the system remains below ?0.30 ± 0.06 V. 相似文献