基于可拓联系云模型的隧道塌方风险等级评价方法

为准确预测隧道塌方风险等级,基于塌方相关理论和工程实际,建立塌方风险等级评价因子体系,借助云理论中云雾化现象检验采用综合权重方法确定的评价因子权重,利用物元可拓理论与联系云模型实现评价因子定性与定量之间的转换,提出1种基于可拓联系云的隧道塌方风险等级评价方法。计算待评价物元与联系云模型间的综合确定度,结合模糊等级特征值确定塌方风险等级,并引入距离相似性判断风险的演变趋势。研究结果表明:可拓联系云模型评价结果与实际塌方风险等级一致,模型可以较好地适用于隧道塌方风险等级评价。     

沪宁城际铁路高架桥段CRH动车组运行引起的地面振动现场测试与分析

对沪宁城际铁路CRH动车组运行引起的高架桥段地面振动竖向速度和加速度进行了现场测试,分析了地面振动特征及其传播的衰减规律。结果表明:CRH动车组运行引起的地面振动主频在70Hz以下,属于低频振动;地面振动峰值速度和加速度随着离高架桥距离的增大而减小,20m以内地面振动衰减幅度较大;地面振动峰值随列车时速的提高而增大,车厢数量对地面振动峰值和主频成分的影响不明显;CRH动车组运行引起的地面振动对一般性建筑物影响不大,列车时速为300km左右时,地面振动速度超过办公室等公共建筑的允许值,列车时速为200km左右时,地面振动速度超过居民住宅的允许值;与其他高速铁路的地面振动实测值相比,沪宁城际铁路CRH动车组运行引起的高架桥段地面振动强度相对较低。     

城乡建设用地增减挂钩中拆旧地块选址适宜性评价研究——以辽宁省桓仁县华莱镇为例

为了更加合理的选择拆旧地块,以辽宁省桓仁县华莱镇为例,通过实际分析与特尔菲法选取14个评价指标,通过层次分析法确定指标的权重,采用加权指数和法计算评价得分,并运用累积曲线分级法将评价对象分为四类区域。结果表明最适宜拆旧区占居民点总面积的4.14%,适宜拆旧区占居民点总面积的6.16%,不适宜拆旧区占居民点总面积的31.91%,最不适宜拆旧区占居民点总面积的57.79%。     

模拟地下水微生物除铁技术的探索性研究

为探讨模拟地下水微生物除铁技术的若干控制因素以及微生物除铁的部分规律,对四个装有不同粒径石英砂填料的滤柱进行人工模拟实验及分析测试。实验结果表明：滤柱的成熟过程是铁细菌有规律的增殖并固定滤料表面的铁质活性滤膜实现对亚铁离子氧化的过程。根据细菌的成长过程,滤柱除铁效果以及滤柱能够承受的负荷,把滤砂的成熟过程分为适应期、第一增长期、第二增长期和稳定期等四个时期。在实现除铁的过程中,填料大小、滤速等条件对除铁效果有着影响。     

Estimating Nitrogen Loading to Ground Water and Assessing Vulnerability to Nitrate Contamination in a Large Karstic Springs Basin,Florida1

Abstract: A nitrogen (N) mass‐balance budget was developed to assess the sources of N affecting increasing ground‐water nitrate concentrations in the 960‐km² karstic Ichetucknee Springs basin. This budget included direct measurements of N species in rainfall, ground water, and spring waters, along with estimates of N loading from fertilizers, septic tanks, animal wastes, and the land application of treated municipal wastewater and residual solids. Based on a range of N leaching estimates, N loads to ground water ranged from 262,000 to 1.3 million kg/year; and were similar to N export from the basin in spring waters (266,000 kg/year) when 80‐90% N losses were assumed. Fertilizers applied to cropland, lawns, and pine stands contributed about 51% of the estimated total annual N load to ground water in the basin. Other sources contributed the following percentages of total N load to ground water: animal wastes, 27%; septic tanks, 12%; atmospheric deposition, 8%; and the land application of treated wastewater and biosolids, 2%. Due to below normal rainfall (97.3 cm) during the 12‐month rainfall collection period, N inputs from rainfall likely were about 30% lower than estimates for normal annual rainfall (136 cm). Low N‐isotope values for six spring waters (δ¹⁵N‐NO₃ = 3.3 to 6.3‰) and elevated potassium concentrations in ground water and spring waters were consistent with the large N contribution from fertilizers. Given ground‐water residence times on the order of decades for spring waters, possible sinks for excess N inputs to the basin include N storage in the unsaturated zone and parts of the aquifer with relatively sluggish ground‐water movement and denitrification. A geographical‐based model of spatial loading from fertilizers indicated that areas most vulnerable to nitrate contamination were located in closed depressions containing sinkholes and other dissolution features in the southern half of the basin.     

Seasonal and Long‐Term Variations in Hydraulic Head in a Karstic Aquifer: Roswell Artesian Basin,New Mexico1

Abstract: Water levels in the karstic San Andres limestone aquifer of the Roswell Artesian Basin, New Mexico, display significant variations on a variety of time scales. Large seasonal fluctuations in hydraulic head are directly related to the irrigation cycle in the Artesian Basin, lower in summer months and higher in winter when less irrigation occurs. Longer‐term variations are the result of both human and climatic factors. Since the inception of irrigated farming more than a century ago, over‐appropriation of water resources has caused water levels in the artesian aquifer to fall by as much as 70 m. The general decline in hydraulic head began to reverse in the mid‐1980s due to a variety of conservation measures, combined with a period of elevated rainfall toward the end of the 20th Century.     

Hydrology of Clay Settling Areas and Surrounding Landscapes in the Phosphate Mining District,Peninsular Florida1

Abstract: The objective of this study was to use applied and naturally occurring geochemical tracers to study the hydrology of clay settling areas (CSAs) and the hydrological connectivity between CSAs and surrounding hydrological landscapes. The study site is located on the Fort Meade Mine in Polk County, Florida. The CSA has a well‐developed, subangular‐blocky, clay‐rich surface layer with abundant desiccation cracks and other macropores, and a massive, clay‐rich sublayer that is saturated below ～1.0‐2.5 m. A bromide tracer was applied to study hydrological processes in the upper part of the CSA. Bromide infiltrated rapidly and perched on a massive, clay‐rich sublayer. Bromide concentrations decreased in the upper part of the profile without being transported vertically down through the lower part of the profile suggesting that bromide was lost to lateral rather than to vertical transport. Infiltration and lateral flow were rapid suggesting that preferential flow through desiccation cracks and other macropores likely dominates flow in the upper part of the CSA. Naturally occurring solute and stable isotope tracers were used to study the hydrological connectivity between the CSA and the surrounding hydrological landscape. Three‐end mass‐balance mixing model results indicate that shallow and/or deep CSA water can be found in all downgradient waters and must be as much as ～50% of some downgradient waters. Discharge from the CSA to the surrounding surface water‐bodies and surficial aquifer occurs laterally through the berms and/or vertically through the massive, clay‐rich sublayer. However, the precise flow paths from the CSA to the surrounding hydrological landscape are unclear and the fluxes remain unquantified, so the precise effects of CSAs on the hydrology of the surrounding hydrological landscape also remain unquantified.     

Differences in Dissolved Organic Carbon and Nitrogen Responses to Storm‐Event and Ground‐Water Conditions in a Forested,Glaciated Watershed in Western New York1

Abstract: Differences in the storm‐event responses of dissolved organic carbon (DOC) and nitrogen (DON) in streamflow and ground water were evaluated for a glaciated forested watershed in western New York. Eight to ten storm events with varying rainfall amounts, intensities, and antecedent moisture conditions were studied for three catchments (1.6, 3.4, and 696 ha) over a three‐year period (2003‐2005). Concentrations of DOC in streamflow exiting the catchments were significantly higher for storm events following a dry period, whereas no similar response was observed for DON. Highest DON concentrations in streamflow were typically associated with storm events following wet antecedent moisture conditions. In addition to antecedent moisture conditions, DOC concentrations were also positively correlated with precipitation amounts, while DON did not reveal a consistent pattern. Streamwater and ground‐water concentrations of DOC during storm events were also strongly correlated with riparian ground‐water depths but a similar relationship was not observed for DON. Ground‐water DON concentrations were also more variable than DOC. We hypothesized that the differences in DOC and DON responses stemmed from the differences in catchment sources of these solutes. This study suggests that while DOC and DON are intrinsically linked as components of dissolved organic matter, their dynamics and exports from watersheds may be regulated by a different set of mechanisms and factors. Identifying these differences is critical for developing more reliable and robust models for transport of dissolved organic matter.     

WATER QUALITY IN SHALLOW ALLUVIAL AQUIFERS,UPPER COLORADO RIVER BASIN,COLORADO, 19971

ABSTRACT: Shallow ground water in areas of increasing urban development within the Upper Colorado River Basin was sampled for inorganic and organic constituents to characterize water‐quality conditions and to identify potential anthropogenic effects resulting from development. In 1997, 25 shallow monitoring wells were installed and sampled in five areas of urban development in Eagle, Grand, Gunnison, and Summit Counties, Colorado. The results of this study indicate that the shallow ground water in the study area is suitable for most uses. Nonparametric statistical methods showed that constituents and parameters measured in the shallow wells were often significantly different between the five developing urban areas. Radon concentrations exceeded the proposed USEPA maximum contaminant level at all sites. The presence of nutrients, pesticides, and volatile organic compounds indicate anthropogenic activities are affecting the shallow ground‐water quality in the study area. Nitrate as N concentrations greater than 2.0 mg/L were observed in ground water recharged between the 1980s and 1990s. Low concentrations of methylene blue active substances were detected at a few sites. Total coliform bacteria were detected at ten sites; however, E. coli was not detected. Continued monitoring is needed to assess the effects of increasing urban development on the shallow ground‐water quality in the study area.     

中国西北干旱区的地下水资源及其特征

分析了中国西北干旱区自然地理环境、水资源形成和分布及其利用状况,重点讨论了该区地下水资源分布的地区差异与赋存特征。该区平原地下水资源是山区水资源(包括降水和雪冰融水)在平原区内的转化;山区水资源是内陆河流和平原地下水的惟一补给来源;盆地平原地下水和地表水构成一个统一的水资源系统、独立的水文单元和完整的水生态体系。充分了解干旱区降水-地表水-地下水资源链的特征,正确认识干旱区“三水”转化自然规律,合理利用“三水”,对该区域社会经济持续发展具有重要意义。