黄土地区降雨入渗模型初探

基于饱和下渗理论和考虑新入渗雨水驱替旧土壤水分的作用,根据力学原理提出了一个简明的入渗模型及计算下渗锋面处毛管吸力的方法.模型参数物理概念明确,便于根据实际情况进行修正,有较大的灵活性.模型在团山沟径流场进行了验证.     

济南市南部山区渗漏带汇水区景观恢复与优化

通过分析龙洞和渴马渗漏带所在汇水区地表景观格局,发现龙洞流域自然景观占优势,植被覆盖良好、景观聚集度高、林地破碎度低,景观空间布局合理;渴马流域虽然景观类型丰富、多样性高,但农田等半自然景观占优势,植被覆盖率低,景观聚集度低,而林地破碎度高,地表景观呈退化趋势。前者的景观格局明显优于后者。这两个流域都有地表水汇流、入渗的生态功能,地表景观格局的优劣影响到地表水源涵养和渗漏带入渗功能的发挥,因而龙洞渗漏带的渗漏功能好于渴马渗漏带。从熵值角度,通过两个流域间的比较分析找出了致使渴马流域景观格局不合理的驱动因素,继而提出了在该流域内的景观格局空间优化措施。     

基于遗传算法的煤层注水渗透特征参数反演

煤层注水是防治矿井冲击地压灾害发生的最有效的方法。确定煤层渗透特征参数，是合理确定注水工艺参数、有效控制防灾效果的关键，有很强的现实意义。遗传算法是全局收敛的方法，用该算法对煤体导水、贮水等渗透特征参数反演，方法稳定可靠。以观测水分增值与计算结果的相对偏差作为最优搜索目标函数，建立GA反演适应度函数及迭代收敛准则；GA操作采用无条件保护最优个体、种群个体无死亡及每个体只有1次参与交换机会等规则。提出通过对已知参数正向问题结果(水分增值)的反演计算，验证遗传算法精度。算例结果表明，繁衍迭代至第41代时，反演参数结果与理论参数几乎完全拟合。达到最优解，精度符合工程要求。     

降雨入渗补给灵敏度及其计算方法研究

对两类降雨入渗计算模型进行了研究：①简单的水量平衡模型；②数值模拟模型。这两类模型的假定条件和非饱和的理论概念差别很大。两类模型在非饱和区中的应用表明，在非饱和区均质土壤条件下，水量平衡模型计算的降雨入渗补给量与应用数值模拟模型计算所得结果基本相吻合。灵敏度分析表明了地下水位变动对降雨入渗补给的影响。假定地下水位不变所造成的误差可作为水文地质参数的一个函数来处理。本文研究成果在一定水文地质条件下的非饱和水流模型、饱和水流模型或排水模型系统计算中具有十分重要的参考应用价值。     

河水入渗过程中蒸发损失的实验模拟研究

为了深化河流入渗机理的认识以及提高地下水资源评价的精度,本文就河水入渗过程中蒸发损失量的计算进行了室内模拟试验研究.试验结果表明,常年有水河流的河水入渗量的蒸发损失率小于10%,即有90%以上的河水入渗量补给地下水.     

Isotopic and hydrochemical studies of groundwater flow and salinity in the Southern Upper Rhine Graben

In order to determine the origin and the propagation mechanisms of highly concentrated chloride brines within the Quaternary aquifer system in the southern part of the Upper Rhine Graben, a combined isotope (H, O, C) and hydrochemical analysis was carried out. Groundwater recharge in this area is a complex system, consisting of local precipitation, river bank filtration, lateral flow from the Graben borders and, to a minor extent, an old Pleistocene component. In some areas, groundwater consists of up to 90% of recent bank filtrate, reaching depths down to at least 100 m. The isotopic and hydrochemical results show, that the elevated chloride concentrations in the Quaternary aquifer mainly result from leaky settling basins charged by the French potash mines until the mid 1970s. Input of natural brines coming from tertiary salt diapirs is of only minor importance. While infiltrating, the anthropogenic brines were strongly diluted by local river bank filtrate of the Rhine. Nevertheless, maximum chloride concentrations nowadays still reach some 10,000 mg/l at the base of the aquifer at a depth of more than 100 m below surface. The main volume of the brines is stored in the less permeable lower part of the quaternary sediments (Breisgau-Formation) whereas only a minor part is transported northwards with the rapid convective groundwater flow. Brines undergoing only dilution preserve their hydrochemical characteristics (NaCl-type). In contrast, brines recirculated from the Breisgau-Formation show a northwards increasing alteration through ion exchange processes. Potassium and sodium may be fixed in the fine grained aquifer material while calcium is set free into the groundwater. After a flow distance of about 12 km, complex hydraulic interactions between groundwater and surface waters lead to the rise of strongly diluted and hydrochemically altered brines with chloride contents up to maximum 700 mg/l. The presented case study is an example for a detailed analysis of a multi-component groundwater mixing system using combined isotope and hydrochemical methods. Furthermore, cation exchange is shown as a major process affecting the hydrochemical evolution of the young groundwater in the southern Upper Rhine Graben which is locally strongly polluted by chloride as a consequence of former potash mining.     

石羊河流域平原区土壤入渗特性空间变异的研究

在野外原位入渗试验的基础上,建立了简化Philip入渗模型及其土壤转换函数,借助ARCVIEW软件生成了石羊河流域平原区土壤入渗特性参数的空间分布图,并分析了入渗特性的空间变异特征。研究表明,简化Philip入渗模型是点面转化中比较理想的模型,模型参数α的土壤转换函数可以简便地估算土壤入渗特性,两者的结合是研究大尺度土壤入渗空间变异的一种有效方法。     

Carbonation of Cl-rich scapolite boudins in Skallen, East Antarctica: evidence for changing fluid condition in the continental crust

Spectacular reaction textures in poikiloblastic scapolitite boudins, within marbles in the continental crust exposed in the Lützow–Holm Complex, East Antarctica, provide insights into the changing fluid composition and movement of fluid along grain boundaries and fractures. Petrographic and geochemical features indicate scapolite formation under contrasting fluid compositions. Core composition of scapolite poikiloblasts (Scp_I) are marialitic (Cl = 0.7 apfu) whereas rims in contact with biotite or clinopyroxene are meionite rich. Fine‐grained recrystallized equigranular scapolite (Scp_II) shows prominent chemical zoning, with a marialitic core and a meionitic rim (Cl = 0.36 apfu). Scapolite poikiloblasts are traversed by Scp_III reaction zones along fractures with compositional gradients. Pure CO₂ fluid inclusions are observed in healed fractures in scapolite poikiloblasts. These negative crystal‐shaped fluid inclusions are moderately dense, and are believed to be coeval with Scp_III formation at temperatures >600 °C and a minimum pressure of c. 3.8 kbar. Grain‐scale LA‐ICPMS studies on trace and rare earth elements on different textural types of scaplolites and a traverse through scapolite reaction zone with compositional gradient suggest a multistage fluid evolution history. Scp_I developed in the presence of an internally buffered, brine‐rich fluid derived probably from an evaporite source during prograde to peak metamorphism. Recrystallization and grain size reduction occurred in the presence of an externally sourced carbonate (CaCO₃)‐bearing fluid, resulting in the leaching of Cl, K, Rb and Ba from Scp_I along fractures and grain boundaries. Movement of fluids was enhanced by micro‐fracturing during the transformation of Scp_I to Scp_III. Fractures in fluorapatite are altered to chlorapatite proving evidence for the pathways of escaping Cl‐bearing fluids released from Scp_I. The present study thus provides evidence for the usefulness of scapolite in fingerprinting changing volatile composition and trace element contents of fluids that percolate within the continental crust.     

A simulation model for unified interrill erosion and rill erosion on hillslopes

A mathematical model was developed for simulating runoff generation and soil erosion on hillslopes. The model is comprised of three modules: one for overland flow, one for soil infiltration, and one for soil erosion including rill erosion and interrill erosion. Rainfall and slope characteristics affecting soil erosion on hillslopes were analysed. The model results show that the slope length and gradient, time distribution rainfall, and distribution of rills have varying influence on soil erosion. Erosion rate increases nonlinearly with increase in the slope length; a long slope length leads to more serious erosion. The effect of the slope gradient on soil erosion can be both positive and negative. Thus, there exists a critical slope gradient for soil erosion, which is about 45° for the rate of erosion at the end of the slope and about 25° for the accumulated erosion. Copyright © 2005 John Wiley & Sons, Ltd.     

现行几个主要产流模型的剖析

目前广泛应用的几个主要产流模型各有特点，但以往对它们的综合比较及其相互关系研究得不多，从而造成了用户选择模型的困难。通过深入剖析与对比，搞清了这几个模型之间的联系与区别，以及应用中需要注意的问题，一般情况下，应优选用综合产流模型。