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191.
192.
巷道围岩温度分布及调热圈半径的影响因素分析 总被引:3,自引:3,他引:3
分析了巷道壁面水分蒸发情况下通风时间、岩石的热物理性质、巷道几何尺寸、巷道风流与围岩壁面的对流换热系数、壁面湿度系数与风流相对湿度的变化对围岩温度分布及调热圈半径的影响。随着通风时间的延长 ,围岩冷却范围逐渐向围岩内部推移 ,推移速度逐渐降低 ;巷道壁面水分蒸发和风流相对湿度对靠近壁面处围岩温度分布影响很大 ,但对深部围岩温度分布的影响逐渐变小 ,所以对调热圈半径的影响很小 ;岩石导温系数对调热圈半径及其内部的温度分布影响较大。巷道壁面风流与围岩的换热系数和巷道的几何尺寸对巷道围岩的冷却范围影响非常小。 相似文献
193.
Collins David N. Harrison John Kitcher John M. S. 《Water, Air, & Soil Pollution: Focus》2002,2(2):191-207
Measurements of electrical conductivity and discharge ofmeltwaters in the Gornera, which drains from the 83%glacierised basin containing Gornergletscher, PennineAlps, Switzerland, were undertaken between May andSeptember in both 1979 and 1998. Discharge in theGornera was 43% higher in 1998, average air temperatureduring the ablation season being 2.1 °C warmer andpreceding winter precipitation 28% lower than in 1979. Mean electrical conductivity of meltwater in 1998 wasreduced by 40%. In the same 60 day period in 1998,however, solute flux was augmented by only 2% bycomparison with 1979. Year-to-year climatic variations,reflected in discharge variability, strongly affectsolute concentration in glacial meltwaters, but havelimited impact on solute flux. Climatic conditionstranslate into meltwater quality through inter-relationships between mineral reaction rates, subglacialresidence time in contact with sediment, and discharge. Annual variability in solute flux depends on the extentto which volume of flow can offset decline in soluteconcentration brought about by reducing residence time. 相似文献
194.
Duane T. Gardiner Qingguo Sun 《Journal of the American Water Resources Association》2002,38(4):1061-1067
ABSTRACT: Irrigation reduces infiltration rates for subsequent irrigations or rains, thus decreasing the efficiency of water use and impacting watersheds in agricultural areas. Reduced infiltration causes greater runoff with its accompanying erosion, pollution, and sedimentation. Small rates of polyacrylamide (PAM) improve infiltration and reduce erosion on irrigated fields. The effects of PAM on infiltration of rainwater, the longevity of the effects of various rates of PAM, and the effects of repeated or intermittent PAM applications are not understood. This study measured the effects of four PAM application rates (0, 10, 25, and 40 ppm) on the subsequent infiltration of wastewater or simulated rainwater for seven weeks following the initial treatments. Also, effects of repeated and intermittent PAM applications on infiltration were determined. Hydraulic conductivity was determined for each soil column using the falling head method. Two soil types from the coastal plain of south Texas were tested — a soil high in clay (Victoria) and a sandy loam (Willacy). Effects of PAM rates were significant, but effects of water type were not (P > 0.05). Benefits from single PAM applications disappeared within two weeks. Water enriched with PAM is so viscous and infiltrates so slowly that applying PAM in every irrigation event may not be feasible. However, repeating PAM applications every two weeks maintained high infiltration rates on the alternate weeks. This intermittent application of PAM may be a practical approach for improving infiltration rates on irrigated lands. 相似文献
195.
ABSTRACT: Customarily, it has been assumed that hydraulic conductivity is a stationary, homogeneous stochastic process with a finite variance for stochastic analysis of solute transport in the subsurface. That the distribution of hydraulic conductivity may have a fractal behavior with long range correlations was suggested from field data analyses. This motivates us to further investigate how the fractal behavior of permeability distribution impacts solute transport in porous media. This study provides longitudinal and transverse macrodispersivity coefficients and the variance of the solute concentration. Longitudinal and transverse macrodispersivity coefficients are found to depend strongly on the fractal dimension (D) of logarithmic hydraulic conductivity (logK). The longitudinal and transverse macrodispersivity coefficients are the highest when D = 1, and the values decrease monotonically to zero at D = 2. Both coefficients correspond to the characteristic length scale of the logK distribution, thus are scale dependent parameters. The ratio of the transverse to the longitudinal macrodispersivity coefficient is on the order of 10‐1 to 10‐4. Concentration variance also decreases with the fractal dimension of logK. There is no spatial spreading of solute for D = 2, and the concentration variance reaches zero for this case. 相似文献
196.
堤坝蚁穴系统的水力-岩土模型及稳定性 总被引:6,自引:0,他引:6
堤(坝)身蚁穴系统由蚁路及其周边白蚁活动范围内的土体构成,因土栖白蚁的生物化学作用,其表现出与围护土层完全不同的性质.将有关条件适当简化后,整个蚊道可简化为一个具有两弯折头的自由出流短管系统的水力-岩土计算模型.当洪水水位涨至蚁穴系统之上时,可按泄水短管计算;当洪水水位退至蚁穴系统最高点之下时,可按虹吸管系统计算.通过对蚁穴系统的水力变化特征、岩土工程特性及其相互间共同作用的分析与计算,可较准确地预测堤身的破坏点位置.同时,根据其破坏特征,提出了相应的处理措施. 相似文献
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企业为了节约成本,在实际酸洗过程中反复利用酸洗废液,致使Fe2+浓度接近饱和,而对于该类废液的处理,一直还局限在传统处理方法中,存在着很多弊端。经过对传统工艺的实验与分析,提出一种高效率、低耗能的新工艺——雾化喷蒸法,并设计出相应的处理设备。 相似文献