厦门海绵化改造区入渗性能测定及特征

为探究厦门海绵城市改造完成区的入渗性能,利用Guelph入渗仪法测量了两条海绵道路及一个海绵小区的土壤饱和导水率,对比分析了5 cm单水头、10 cm单水头、单水头均值及双水头法所测得土壤饱和导水率的差异,并与传统城市建设区进行了对比分析。结果表明:设有生态多孔纤维棉的新顺路绿化带入渗性能最好,采用一般转输型植草沟的新景路绿化带次之,而设有隔水顶板、地下为停车场的洋塘居住区B13绿地入渗性最差。不同测量方法的结果对比显示,5 cm单水头法计算所得的土壤饱和导水率标准差最小,双水头法的土壤饱和导水率标准差最大;在厦门进行土壤入渗试验时,推荐采用5 cm单水头法计算土壤饱和导水率。     

Local infiltration devices at parking sites--experimental assessment of temporal changes in hydraulic and contaminant removal capacity.

On site infiltration of stormwater is a common practice in order to avoid hydraulic overload of the urban drainage system. If hydrological conditions allow on-site infiltration--this is even mandatory from a legal point of view. Focus in this work is on surface infiltration of stormwater from parking lots. Proper operation of those devices is assumed to be appr. 15 years, as permits granted are limited to this time. Questions are raised whether this considered life expectancy is feasible. One apprehension is a possible clogging effect reducing the hydraulic capacity of the swale. The second aim was to identify magnitudes of accumulated pollutant loads with respect to limitations onto lifetime. The experimental investigation covered infiltration swales of different ages from eleven supermarket parking lots in Tyrol. Hydraulic permeabilities were assessed as well as chemical conditions of the soil material regarding hydrocarbon index (HI) and heavy metals (Cu, Zn, Pb and Cd). Further mass balance of contaminants has been performed in order to assess the operational life time based on pollutant load consideration. Calculations were based on load estimations using literature based minima and maxima concentrations from surface flows. Testing the correlation of hydraulic and pollutant measurements against site specific parameters (age, traffic load) revealed no distinct relation. In general all measured pollutants were found under limit concentrations. Mass balance calculations showed that limit concentrations are not exceeded either for worst case loading and considering 15 years of operation.     

温度对简化蒸发法测定土壤水分特征曲线和导水率曲线的影响

根据Schindler(1980)提出的简化蒸发法,在微型土柱的两个高度安装张力计测定土壤吸力,并采用称重法得到土壤含水率,通过公式再计算土壤水分特征曲线和导水率曲线。结果表明:温度的差异影响土壤水分特征曲线和导水率曲线。在砂土、砂壤土-1和砂壤土-2的水分特征曲线上,当吸力小于10 kPa时,同一吸力时25℃曲线的含水率均小于16℃曲线的含水率;当吸力大于10 kPa时,砂土和砂壤土-2在同一吸力时25℃曲线的含水率均大于16℃曲线的含水率,而砂壤土-1无此变化。在砂土、砂壤土-1和砂壤土-2的导水率曲线上,砂土在10kPa以下时25℃导水率值低于16℃导水率值,其他情况下,在同一吸力时,三种土样的25℃导水率值均高于16℃导水率值。     

水景社区的雨水收集与综合利用设计

为研究城市雨水收集与综合利用,以上海郊区一生态水景社区为例,进行水量平衡计算。结果表明,该社区年均雨水可收集量约45 678 m3,占一年总降雨量的62%左右,不但满足社区每年的绿化浇灌、硬地冲洗以及水面蒸发等消耗量,而且富余雨水经过处理后可用作景观湖的补充水源及其他用水。雨水收集利用系统设计以景观湖为中心,屋面雨水通过2个总容积为675 m3的地下集蓄池来收集,集蓄水量可达1.83万m3/a;绝大部分绿地、道路广场以及极少数屋面的雨水径流通过长1 km的植草浅沟和500 m长的碎石沟渠收集,并汇入2个总面积为800 m2的暴雨塘系统内暂时储存。户外小停车场和小广场的雨水通过砂床过滤系统收集。     

Study on bioretention for stormwater management in cold climate,Part I: Hydraulics

Simulated storm events were applied to four large bioretention columns to approximate 1.6 years of equivalent volume in Edmonton, Alberta’s typical climate. Summer, winter, and spring runoff were simulated in temperature-controlled laboratories with a range of −20 °C to +20 °C. During summer less porous bioretention media (i.e. loam soil) effectively weakened peak flows by >83% for 1:2 year events while more porous bioretention media (i.e. sandy loam soil) maintained hydraulic conductivities >9.1 cm/h. Winter operation consisted of all columns being subjected to −20 °C and then 1 °C repeatedly. Events were applied at an air temperature of 1 °C and, although frozen initially, more porous media experienced faster water breakthrough and ponding disappearance in winter indicating that hydraulic performance during intermittent warming periods in winter may be achievable. All columns’ hydraulic performance rebounded quickly in the subsequent summer. All columns successfully managed 1:2 year events in terms of infiltration rate, ponding depth and duration. Preliminary results also showed that both media have the potential to manage less frequent (1:5 and 1:10 year) events.     

分散性黏土导热系数试验与预测方法研究

分散性黏土冻融循环导致的破坏非常普遍,在我国东北地区水利工程中尤为严重。开放系统中分散性黏土冻融特性有别于非分散性黏土,土体导热系数是土体热分析最重要的参数之一。本文以分散性黏土为研究对象,阐明了影响分散性黏土导热系数的因素;基于Johansen法的改进,建立了适合分散性黏土特点的导热系数预测方法。研究表明,分散性黏土导热系数的影响因素主要为矿物成分、含水率、孔隙率(干密度)和温度。土体温度为负温时,温度越低,土的导热系数越大。初始含水率低于10%,土的导热系数不受温度的影响;初始含水率大于15%,土的导热系数受温度影响较大。饱和状态下的分散性黏土导热系数有别于非分散性黏土,采用串联/并联预测模型方法来计算。所提出的分散性黏土导热系数预测方法和公式,可反映土体温度、土体矿物成分、含水率、干密度的影响,与试验结果吻合,并可为分散性黏土研究和工程应用提供参考和指导。     

Modeling the Infiltration Capacity of Permeable Stormwater Channels with a Check Dam System

The use of permeable stormwater channels has introduced concerns over the effects of infiltration on the hydraulic behavior of their flow and the effects of flow hydraulic conditions (e.g., the water level, channel section, flow velocity, and vegetation) on the channel infiltration capacity. A check dam system provides backwater ponding, which increases the flow water depth along a channel. In this study, a channel model was used to investigate the variation in the infiltration capacity of permeable stormwater channels under different flow hydraulic conditions. Increasing the downstream check dam height and using a grass cover increased the infiltration rate and cumulative infiltration because of the decreased velocity and increased flow depth. The presence of subsurface water did not affect the hydraulic characteristics of the channel flow but decreased the cumulative infiltration because of the fast saturation of the soil. An empirical equation was developed for predicting the infiltration capacity of grassed channels in which four hydraulic parameters (i.e., the water depth, base width, side slope, and velocity) are introduced to the modified Kostiakov model. The developed model was used to calculate the runoff reduction due to infiltration along a grassed channel with and without a check dam system. The percentage of infiltrated water increased from 8 to 14% with the check dam system. The developed model can be used to predict the infiltration capacity of permeable channels for improved stormwater management and provides a valuable decision support tool for permeable channel design.

     

湿润喀斯特地区冬季灌丛土壤水分对降雨的响应

为分析湿润喀斯特地区冬季灌丛土壤水分对降雨响应的规律,基于实地逐日监测记录的灌丛土壤水分和降雨数据,对冬季灌丛土壤水分与降雨的响应关系进行分析。结果表明：小于5.80 mm的12场小降雨事件对土壤水分无法进行有效补给,大于20 mm的2场降雨事件能够有效补给土壤水分,土壤水分的响应时间随着降雨量的增加而加快。根据土壤水分变化趋势,冬季灌丛土壤水分变化可划分为3个阶段：土壤水分消退期、土壤水分上升期、土壤水分平稳期。冬季,受植被截留、地表枯落物吸收等因素的共同影响,导致小降雨事件不能使灌丛土壤水分得到有效补给,表现出平稳或微减的变化;大降雨事件对灌丛土壤水分起到有效补给,能够促使更多水分向深层渗透,显著改善深层灌丛土壤水分状况,且雨前土壤含水量越低,降雨对表层土壤水分的补给越大。冬季灌丛土壤水分的入渗深度主要受强度适中、历时长、雨量大的降雨影响,且雨前土壤含水量越高,则降雨的入渗深度越大。     

不同容重土壤对单坑入渗土壤含水率的影响

通过不同容重土壤对单坑入渗湿润体和含水率分布规律的影响进行试验研究,得出如下结论：不同容重的土壤的湿润体形状具有相似性;容重大的土壤径向含水率在靠近水室的地方比容重小的土壤含水率大;土壤含水率随着垂向距离的增大。先增大后减小。     

Self-adaptive Green-Ampt infiltration parameters obtained from measured moisture processes

The Green-Ampt(G-A) infiltration model(i.e., the G-A model) is often used to characterize the infiltration process in hydrology. The parameters of the G-A model are critical in applications for the prediction of infiltration and associated rainfall-runoff processes. Previous approaches to determining the G-A parameters have depended on pedotransfer functions(PTFs) or estimates from experimental results, usually without providing optimum values. In this study, rainfall simulators with soil moisture measurements were used to generate rainfall in various experimental plots. Observed runoff data and soil moisture dynamic data were jointly used to yield the infiltration processes, and an improved self-adaptive method was used to optimize the G-A parameters for various types of soil under different rainfall conditions. The two G-A parameters, i.e., the effective hydraulic conductivity and the effective capillary drive at the wetting front, were determined simultaneously to describe the relationships between rainfall, runoff, and infiltration processes. Through a designed experiment, the method for determining the GA parameters was proved to be reliable in reflecting the effects of pedologic background in G-A type infiltration cases and deriving the optimum G-A parameters. Unlike PTF methods, this approach estimates the G-A parameters directly from infiltration curves obtained from rainfall simulation experiments so that it can be used to determine site-specific parameters. This study provides a self-adaptive method of optimizing the G-A parameters through designed field experiments. The parameters derived from field-measured rainfall-infiltration processes are more reliable and applicable to hydrological models.     

On-site infiltration of road runoff using pervious pavements with subjacent infiltration trenches as source control strategy

The focus in this work was on subsoil infiltration of stormwater from parking lots. With regard to operation, reduced infiltration performance due to clogging and pollutants in seepage, which may contribute to contaminate groundwater, are of interest. The experimental investigation covered a pervious pavement with a subjacent infiltration trench draining an impervious area of 2 ha. In order to consider seasonal effects on the infiltration performance, the hydraulic conductivity was measured tri-monthly during monitoring with a mobile sprinkling unit. To assess natural deposits jointing, road bed, gravel of infiltration trenches and subsoil were analysed prior to commencement of monitoring for heavy metals, polycyclic aromatic and mineral oil type hydrocarbons. Furthermore, from 22 storm events, water samples of rainfall, surface runoff, seepage and ground water were analysed with regard to the above mentioned pollutants. The study showed that the material used for the joints had a major impact on the initial as well as the final infiltration rates. Due to its poor hydraulic conductivity, limestone gravel should not be used as jointing. Furthermore, it is recommended that materials for the infiltration facilities are ensured free of any contaminants prior to construction. Polycyclic aromatic and mineral oil type hydrocarbons were, with the exception of surface runoff, below detection limits. Heavy metal concentrations of groundwater were with the exception of lead (because of high background concentrations), below the permissible limits.     

城市雨水径流生态处理研究现状与进展

从城市雨水径流产生的问题出发,分析对城市雨水径流进行生态处理的必要性。对包括植被缓冲带、植被浅沟、生物滞留系统、滞留塘和人工湿地等在内的多项雨水径流管理与利用生态技术的优缺点、净化机理、适用条件等进行了综合比较。并对我国城市雨水径流生态处理技术的应用前景进行了展望,为生态城市建设和城市水环境改善提供借鉴。     

华北山前平原灌溉农田深层土壤水分动态特征及渗漏量估算

以中国科学院栾城农业生态系统试验站的大埋深土壤水分剖面观测设施为依托,利用中子水分仪对15.4m深度的土壤水分进行连续1年的定位观测,同时通过定期采集深层土壤和水分样品,对该区土壤水分变动特征和深层入渗量进行了定量研究。结果表明:土壤水分在垂直剖面上的分布受土壤质地组成控制,同时在年内受降水事件和灌溉的影响而波动,随着土壤深度的增加,土壤水分的变异性呈减弱趋势;根区土壤水分受降水(灌溉)和作物耗水的共同影响而变化剧烈,根区以下土壤水分对降水的响应有一定延迟;在观测期间,整个15.5m深度的土壤剖面上有水分的盈余,土壤水贮量增加了216mm,但在小麦生育期土壤水分表现出耗损过程(土壤水贮量减少了208mm)。最后利用氯质量平衡法估算560cm深度处渗漏量约为65mm。     

陕西王东沟小流域野外土壤入渗试验研究

以野外土壤入渗试验为依据，利用时域反射仪进行了土壤水分动态变化的观测，并分析了积水入渗过程中土壤水分的动态变化规津及停渗后土壤水分再分布规律。结果表明：野外土壤积水入渗过程中，土体内任—埋深处士壤含水率的变化一般经历稳定不变、缓慢上升、急剧上升和再稳定4个阶段，不同土地利用类型的土壤每一阶段听经历的时间长短不同；积水深度越大，土壤剖面含水率、入渗量变化越明显，湿润锋的推移也越快；停渗后土壤水分再分布规律表现为表层0～10cm土壤含水率急剧减小，10～70cm土壤含水率开始呈增大趋势，然后再逐渐减小，70cm以下的土壤含水率略有变化。     

南方短时冻土的热物理性质及抗压强度特征

为探讨在极端冰雪条件下南方短时冻土的热物理性质及强度特征,在湖北、湖南、广西等地选取典型土样,对初始含水量不同的土样在不同温度下进行热物理参数和单轴抗压强度试验。结果表明：冻土的干密度越大,导热系数越大;含水量越大,导热系数越大;随着温度的升高,冻土的破坏应变呈现出增大的趋势,应力-应变曲线表现为弱应变软化型或应变硬化型,即冻土的塑性增强;冻土抗压强度随温度的降低而增大;相同温度条件下,饱水后冻土的单轴抗压强度大于等于饱水前的强度。     

Simulation of Soil Moisture Profiles Using K(h) from Coupling Experimental Retention Curves and One-Step Outflow Data

In the present work, the effect on the soil moisture profiles development and the cumulative infiltration when three different equations for calculating the diffusivity versus volumetric water content, D(θ) function, from one-step outflow experimental data are used, is investigated. These D(θ) functions are coupled with moisture retention curves θ(h) (h being the soil matric potential) obtained independently for the determination of the hydraulic conductivity function K(θ) or K(h). The so obtained hydraulic conductivity function, together with θ(h), were employed in solving Richards equation numerically under constant flux conditions in one dimensional vertical infiltration process. Two different porous materials were used for this investigation. It is shown that the three different equations used for the prediction of K(h) have no significant effect on the shape of the moisture profiles for the sand mixture and that a Green–Ampt advancement of the wetting front is observed. For the case of sandy clay soil there are some noticeable differences in the moisture profiles and their shape is comparatively more effusive. Also, one could mention that for both porous media the time of incipient ponding (T) differentiates among the three equations used.     

冻融条件下苏打盐渍土的水盐变化规律研究

冻融作用是导致我国北方半干旱地区土地盐渍化的主要原因之一。以吉林西部大安市为研究区域,通过野外调查和样品采集,开展了盐渍土的室内试验,研究了冻融过程中土壤水盐的运移规律。研究结果表明：该地区土壤中的水盐在冻融过程中经历了两次迁移过程,不同阶段具有各自的特点。冻结过程中,未冻层的水不断向冻层迁移并随之冻结,盐分亦随水分迁移;融化过程中,未融化的冰层阻碍水盐下渗,上层滞水向表层运移并蒸发,使表层盐分急剧增加。在水盐运移过程中,电导率与总盐的变化具有良好的相关关系。室内模拟试验为进一步阐明该区盐渍土的形成机理与影响因素提供了科学依据。     

Development of a Simulation Model for Estimation of Potential Recharge in a Semi-arid Foothill Region

The SMPR (Soil Moisture and Potential Recharge) model is developed to simulate soil moisture content and potential recharge under semi-arid conditions. In SMPR model, infiltration and soil moisture redistribution follow two successive stages. In stage (I), precipitation infiltrates and is distributed into the soil profile utilizing the soil moisture accounting fashion and in stage (II), moisture is redistributed using simplified Richards’ equation (neglecting matric-potential gradient). Liquid and vapor evaporation from bare soil are estimated based on Dual-Crop methodology [Ke and optimized Kcb (0.17)]. Two commonly applied unsaturated hydraulic conductivity functions [K(θ)] of B-C (Brooks and Corey) and V-G (van-Genuchten); and an Empirical Exponential (E-E) equation are locally calibrated and used for potential recharge estimation (as main simulation objective). Model performance (calibration/validation) is based on reasonable estimation of potential recharge and acceptable simulation of soil moisture, considering local lysimeter data. According to results, B-C, V-G an E-E equations produced acceptable simulation of soil moisture content (NRMSE?<?30%), however, potential recharge was underestimated/overestimated, using K(θ) by B-C/V-G. The best estimation of potential recharge (based on absolute annual recharge error, ?Q?<?10%) was achieved by the SMPR model with K(θ) of E-E. Results of the relative simple SMPR model [K(θ) by E-E equation] compared favorably with HYDRUS-1D sophisticated model [using locally calibrated V-G equation of K(θ)].The proposed SMPR model requiring minimal data, can be used in regions with limited data.     

温度影响下土壤水分运动模型

根据不同温度条件下的入渗资料，分析了活塞(Green-Ampt)公式在温度场中的适用性，认为，Green-Ampt公式适用于温度场影响下的土壤水分运动。温度影响下的土壤水分运动的通量主要依赖于概化区的饱和导水率、湿润锋处基质势以及温度，其中饱和导水率的温度效应较大，而基质势的温度效应较小，在较轻质地土壤中可以忽略基质势的温度效应。     

非饱和土渗透系数曲线的分段简化模型

根据影响非饱和土渗透系数变化的主要因素,选取合理特征点将土-水特征曲线划分成4个阶段。在此基础上,对大量数据进行统计分析,建立了一种分段简化模型,用于描述级配不良的非黏性土的非饱和渗透系数曲线,只需知道该模型中特征点的相关参数即可得到完整渗透系数曲线,并通过现有数据进行了验证分析。验证结果表明:在低基质吸力(0＜ψ≤ψ_a)时,lnK-ψ曲线呈线性变化;而当θ_b＜θ≤θ_a时,lnK-lnθ曲线也有类似变化规律。