Experimental study on the effects of the moisture content of bituminous coal on its gas seepage characteristics     

Dingyi Hao  Lei Zhang  Zhiwei Ye  Shihao Tu  Cun Zhang 《Arabian Journal of Geosciences》2018,11(15):436

Moisture content is the main factor affecting the occurrence and flow of gas in bituminous coal and restricts the gas permeability of the coal seam, which affects the effectiveness of gas extraction from the coal seam directly. In order to study the influence of moisture content on the gas seepage characteristics of bituminous coal, this paper focused on bituminous coal from the Xutuan coal mine and used a bespoke laboratory unit called a Gas Flow and Displacement Testing Apparatus (GFDTA). The moisture content of bituminous coal was measured, and the axial and radial gas seepage experiments of bituminous coal under different moisture content conditions were carried out. The average original moisture content (1.3%) and the average saturated moisture content (2.4%) of the bituminous coal sample were obtained. It was observed that, with the increase of time, the original moisture content of the coal decreased with a negative exponential function and the wetting moisture content increased with an Exponential Association function. The gas axial seepage experimental results showed that when the moisture content was lower, the coal adsorbed CH₄; when the moisture content was higher than M_ad, the two fields of gas and liquid are coupled and affect the axial flow of the CH₄, decreasing the moisture content. With higher moisture content, the interaction between the two is more readily evident and the diffusion behavior of the CH₄ has a greater impact on the moisture content. Axial and radial gas seepage experiments, under the same gas pressure, axial pressure, and confining pressure, revealed that with the increase of moisture content, the axial and radial permeability of bituminous coal first increased and then decreased. This phenomenon is analyzed by the water lock effect, the effects of sorption on gas seepage and moisture content on gas adsorption effects. Among them, critical moisture content of approximately 1% exists when the axial and confining pressures are loaded or unloaded at the same time as well as the axial pressure loading or unloading alone. However, the critical moisture content is about 0.5% under confining pressure loading or unloading alone. In addition, in radial seepage experiments, it was observed that the volumetric strain of the coal decreased with the increase in the moisture content.  相似文献   

Determination of groundwater solute transport parameters in finite element modelling using tracer injection and withdrawal testing data   总被引：1，自引：0，他引：1       下载免费PDF全文

Nguyen Van Hoang 《地下水科学与工程》2021,9(4):292-303

The groundwater tracer injection and withdrawal tests are often carried out for the determination of aquifer solute transport parameters. However, the parameter analyses encounter a great difficulty due to the radial flow nature and the variability of the temporal boundary conditions. An adaptive methodology for the determination of groundwater solute transport parameters using tracer injection and withdrawal test data had been developed and illustrated through an actual case. The methodology includes the treatment of the tracer boundary condition at the tracer injection well, the normalization of tracer concentration, the groundwater solute transport finite element modelling and the method of least squares to optimize the parameters. An application of this methodology was carried out in a field test in the South of Hanoi city. The tested aquifer is Pleistocene aquifer, which is a main aquifer and has been providing domestic water supply to the city since the French time. Effective porosity of 0.31, longitudinal dispersivity of 2.2 m, and hydrodynamic dispersion coefficients from D = 220 m²/d right outside the pumping well screen to D =15.8 m²/d right outside the tracer injection well screen have been obtained for the aquifer at the test site. The minimal sum of squares of the differences between the observed and model normalized tracer concentration is 0.00119, which is corresponding to the average absolute difference between observed and model normalized concentrations of 0.035 5 (while 1 is the worst and 0 is the best fit).  相似文献   

Study of diclofenac removal by the application of combined zero-valent iron and calcium peroxide nanoparticles in groundwater          下载免费PDF全文

Liang Wen  Zhou Nian-qing  Dai Chao-meng  Duan Yan-ping  Zhou Lang  Tu Yao-jen 《地下水科学与工程》2021,9(3):171-180

Diclofenac(DCF) is one of the most frequently detected pharmaceuticals in groundwater, posing a great threat to the environment and human health due to its toxicity. To mitigate the DCF contamination,experiments on DCF degradation by the combined process of zero-valent iron nanoparticles(nZVI) and nano calcium peroxide(nCaO_2) were performed. A batch experiment was conducted to examine the influence of the adding dosages of both nZVI and nCaO_2 nanoparticles and pH value on the DCF removal.In the meantime, the continuous-flow experiment was done to explore the sustainability of the DCF degradation by jointly adding nZVI/nCaO_2 nanoparticles in the reaction system. The results show that the nZVI/nCaO_2 can effectively remove the DCF in the batch test with only 0.05 g/L nZVI and 0.2 g/L nCaO_2 added, resulting in a removal rate of greater than 90% in a 2-hour reaction with an initial pH of 5. The degradation rate of DCF was positively correlated with the dosage of nCaO_2, and negatively correlated with both nZVI dosage and the initial pH value. The order of significance of the three factors is identified as pH value nZVI dosage nCaO_2 dosage. In the continuous-flow reaction system, the DCF removal rates remained above 75% within 150 minutes at the pH of 5, with the applied dosages of 0.5 g/L for nZVI and 1.0 g/L for nCaO_2. These results provide a theoretical basis for the nZVI/nCaO_2 application to remove DCF in groundwater.  相似文献   

Local stress analysis in granular materials at a mesoscale     

Ngoc‐Son Nguyen  Hélène Magoariec  Bernard Cambou 《国际地质力学数值与分析法杂志》2012,36(14):1609-1635

The purpose of this paper is to contribute to the change of scale techniques developed for granular materials. The proposed approach consists in considering an intermediate scale between the macroscales and microscales, called the mesoscale, using the classical homogenization scheme. In this approach, the mesoscale for 2D granular materials was defined at the level of local volumes, called mesodomains, which are local closed structures composed of particles in contact. In this paper, we focused on defining a local stress field at this scale. Two different methods are proposed, both based on the equivalent continuum mean stress but using different approximations of the mean stress tensor for each mesodomain. The two proposed methods were then compared to each other. Analyses performed on the stress field at the mesoscale show that this local field is heterogeneous and, in particular, that its heterogeneity is significantly structured at this scale. The distribution of the local mean stress (first invariant of the local stress tensor) is uniform in any mesodomain, whereas the distribution of the stress deviator (second invariant of the deviatoric part of the local stress tensor) is significantly dependent on the elongation direction and on the elongation degree of the mesodomains. The local stress ratio (ratio of the stress deviator to the mean stress) is higher within the mesodomains that are elongated in the global compression direction than that within the ones elongated in the global extension direction. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Cordilleran vein type Pb-Zn-polymetallic deposits of the Xidamingshan district, Guangxi, SW China: Fluid inclusion and geochemical studies   总被引：1，自引：0，他引：1  

Wei Tu  Yang Song Du  Gong Wen Wang  Ying Ping Lei 《Geology of Ore Deposits》2013,55(6):494-502

There are a lot of clastic-sedimentary-rock-hosted hydrothermal vein type polymetallic deposits in the Xidamingshan district, Guangxi, SW China. Two major ones of them, the Fenghuangshan Pb-Zn-Ag-Mn deposit and the Lujing Pb-Zn deposit, have been selected for fluid inclusion and geochemical research in this paper. From fluid inclusion microthermometry, it has been found that they were deposited from fluid with low salinities at medium to low temperatures and low pressures. From hydrogen, oxygen, sulfur and carbon stable isotope studies as well as some trace element composition of sulfides, we have got the conclusion that they were formed in an intrusion-related ore-forming system, which means that they belong to Cordilleran vein type deposits.  相似文献   

Constraining the cosmological time variation of the fine - structure constant     

Le Duc Thong  Tran van Hung  Nguyen Thi Thu Huong  Ha Huy Bang 《Astrophysics》2010,53(3):446-452

The variation of the fine-structure constant α = e ² / ħc can be probed by comparing the wavelength of atomic transitions from the redshift of quasars in the Universe and laboratory over cosmological time scales t ~ 10¹⁰ yr. After a careful selection of pairs of lines, the Thong method with a derived analytical expression for the error analysis was applied to compute the α variation. We report a new constraint on the variation of the fine-structure constant based on the analysis of the C_IV, N_V, Mg_II, Al_III, and Si_IV doublet absorption lines. The weighted mean value of the variation in α derived from our analysis over the redshift range 0.4939 ≤ z ≤ 3.7 is = ( 0.09 ± 0.07)×10⁻⁵. This result is three orders of magnitude better than the results obtained by earlier analysis of the same data on the constraint on Δα/α .  相似文献   

Moisture Movement Through Cracked Clay Soil Profiles   总被引：1，自引：0，他引：1  

Delwyn G. Fredlund  Sandra L. Houston  Quan Nguyen  Murray D. Fredlund 《Geotechnical and Geological Engineering》2010,28(6):865-888

A continuum mechanics approach is used for the formulation of unsaturated hydraulic conductivity functions and the water storage functions for fractured or cracked clay soils in this parametric study. Suggested procedures are based on available research literature related to the behavior of cracked unsaturated porous media. The soil–water characteristic curve, hydraulic conductivity and water storage functions take on the character of bi-modal unsaturated soil property functions. The bimodal character arises out of the independent behavior of the cracks and the intact clay soil. Matric suction changes beneath a slab-on-grade foundation placed on a cracked clay soil profile are modeled for varied surface flux conditions using the proposed unsaturated hydraulic conductivity and water storage functions. The impact of various levels of surface cracking on soil suction distributions is discussed. Suction distribution patterns are dependent on the initial soil surface suction. In particular, the results are dependent upon whether the initial matric suction is less than or greater than the air entry of the cracked clay. There is an extremely wide range of possible conditions that could be modeled but the parametric study results presented in this paper are limited to a series of selected crack widths and densities for an exfiltration case and an infiltration case.  相似文献   

河南栾川地区铅锌矿床地质和硫同位素地球化学   总被引：8，自引：0，他引：8       下载免费PDF全文

段士刚  薛春纪  刘国印  燕长海  冯启伟  宋要武  涂其军  高永宝  高炳宇 《地学前缘》2010,17(2):375

河南栾川地区是我国著名斑岩钼矿集区,近年铅锌矿勘查取得重要进展,但对铅锌矿成因认识分歧颇多。研究表明,栾川地区铅锌矿产在燕山期斑岩钼矿床外围,矿区地层为中元古界官道口群和新元古界栾川群碳酸盐岩-碎屑岩沉积变质建造,地层中侵入有晋宁期辉长岩、正长岩和燕山期酸性斑岩,铅锌矿呈脉状或透镜状,发育3种类型:受燕山期斑岩与元古界钙质地层接触带控制的夕卡岩型铅锌矿、受北西西向层间断裂构造控制的脉状铅锌矿和受北东或近南北向张-张扭性断裂控制的脉状铅锌矿。铅锌矿石中硫化物δ~(34)S_(V-CDT)为近零的正值(骆驼山0.37‰～4.20‰、赤土店-0.32‰～8.30‰、百炉沟-1.20‰～10.90‰、冷水北沟0.70‰～12.10‰),岩浆来源硫特征明显;夕卡岩型铅锌硫化物的δ~(34)S_(V-CDT)与本地斑岩型钼矿石中硫化物的δ~(34)S_(V-CDT)(1.24‰～3.30‰)极为相近,脉状铅锌硫化物的δ~(34)S_(V-CDT)与斑岩型钼矿石中硫化物重合,但有地层中硫(δ~(34)S_(V-CDT)为12.43‰～18.63‰)的影响。总体上δ~(34)S_(黄铁矿)>δ~(34)S_(闪锌矿)>δ~(34)S_(方铅矿),指示矿石中主要硫化物矿物硫同位素分馏基本达到平衡,赤土店铅锌矿石中共生方铅矿与闪锌矿的硫同位素温度计指示硫化物矿物沉淀温度较高(388.29℃)。河南栾川地区铅锌矿主体应为受燕山期构造-岩浆作用控制的中高温热液铅锌矿床。  相似文献   

Loss of 40Ar(rad) from leucite-bearing basanite at low temperature: implications on K/Ar dating.     

Kadosa Balogh  Károly Németh  Tetsumaru Itaya  Ferenc Molnár  Robert Stewart  Ngo X. Thanh  Hironobu Hyodo  Lajos Daróczi 《Central European Journal of Geosciences》2010,2(3):385-398

The Bakony-Balaton Highland Volcanic Field (BBHVF) is located in the central part of Transdanubia, Pannonian Basin, with over 50 alkali basaltic volcanoes. The basanite plug of Hegyestu erupted in the first phase of volcanic activity. K/Ar and Ar/Ar ages were published for the BBHVF. K/Ar and Ar/Ar ages of the leucite-bearing basanite of Hegyestás were conflicting. This is caused by the special Ar retention feature of leucite in this basanite. K/Ar ages measured in the usual way were 25–45% younger, but after HCl treatment of the rock, or after reducing the baking temperature of the argon extraction line from 250°C to 150°C, they became similar to the Ar/Ar ages. All Ar/Ar determinations were performed after HF treatment. HCl treatment dissolved olivine, nepheline, leucite, magnetite and from 1-1 sample analcime or calcite. K dissolution studies from different locations of Hegyestü have shown that K content is mostly ≈2%, but it may decrease to ≈0.3%. HCl treatment dissolved 28.0–63.5% of the K content. The calculated K concentration for the dissolved part of samples with ~2%K was 4.02-6.42%: showing that leucite is responsible for the low temperature loss of ⁴⁰Ar(rad). Ar may release at low temperature from very finegrained mineral, or when the Ar release mechanism changes. A ⁴⁰Ar(rad) degassing spectrum has been recorded in the 55–295°C range of baking temperature and the data were plotted in the Arrhenius diagram. The diagram shows that a change of the structure in the 145–295°C range caused the loss of ⁴⁰Ar(rad). On fractions of HCl treated rock 7.56±0.17 Ma isochron K/Ar age has been determined. This is regarded as minimum age of eruption and it is similar to the Ar/Ar isochron age (7.78±0.07 Ma).  相似文献   

G-WADI PERSIANN-CCS GeoServer for extreme precipitation event monitoring     

Kuolin Hsu  Scott Sellars  Phu Nguyen  Dan Braithwaite  Wei Chu 《寒旱区科学》2013,5(1):0006-0015

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