砂层在黄土中的减渗作用及其计算

本文根据非饱和土壤水的达西定律，对砂层在黄土中的减渗作用及在整个过程中使入渗率由非线性衰减阶段转为线性稳渗阶段的机理做了分析论述。在此基础上提出了不同砂层质地(中值粒径d50)与埋深条件下稳渗率，D的计算方法，建立了砂层质地的中值粒径d50及埋深Z与吸力值Sm的关系。根据水量平衡原理，得到了入渗过程中由非线性衰减阶段开始进入稳渗阶段的时间t1。经试验资料验证，以上计算式不仅计算精度较好，且具有一定的实用性，特别是在缺少土、砂水分运动参数的情况下，仅需积水入渗试验资料即可通过计算取得所需结果。     

基于Winpest反演分析的降雨入渗补给量分区

在水文地质条件复杂地区进行地下水数值模拟时,需要对降雨入渗补给量进行主观确定,参数识别过程比较复杂。利用Modflow软件,建立了Winpest反演模型对渗透系数进行优化,并通过分析反演过程中观测孔模拟水位和实测水位的拟合情况,进行降雨入渗补给量分区优化。将该模型运用于壁板坡隧道隧址区,结果表明:研究区需先按表层出露的不同层位进行降雨入渗补给量初次分区,再对已有分区按不同高程范围进行二次分区和降雨入渗补给量优化方能实现地下水初始渗流场的高精度拟合。利用Winpest反演分析方法,降低了人为设定降雨入渗补给量的盲目性,为水文地质条件复杂地区的地下水初始渗流场数值模拟提供了一种更加快捷高效的途径。     

流动沙丘降雨入渗和再分配过程

本文通过野外监测和模拟降雨试验对流动沙丘降雨入渗补给、再分配过程和蒸发消耗几个方面作了定量研究。结果表明：科尔沁沙地流动沙丘0～200cm深度土壤层特性具有明显的垂直变化，0～20cm为表层干沙层；20～140cm为降雨影响变化层；140cm以下为深部稳定层。土壤入渗速率受降雨强度的控制，强度大，入渗也大，入渗深度与降雨量和降雨强度之间存在线性关系。湿润锋迁移速率在降雨开始较小，而后逐渐增大，达到峰值之后，又随时间而降低，最后趋于稳定。13.4mm的降雨是无效降水和补给地下水的分界点；≥20mm的降雨可使蒸发层土壤在再分配结束后达到最小持水量；≥50mm的降雨通过土壤水分的再分配可以使120cm深度土壤水分达到饱和持水量，进而下层进行饱和排水入渗。     

城市屋顶降雨径流过程单位线模型研究

城市屋顶按透水性质可分为不透水与绿色(渗透)屋顶.对于绿色屋顶,基于土壤水饱和下渗理论,考虑基质土壤层厚度有限性及表面积水深影响,推导建立了降雨径流过程的单位线模型,再联合不透水屋顶降雨径流过程单位线模型,共同构成城市屋顶降雨径流过程的单位线模型,并建立了统一的数学方程表达形式,参数包括响应速率与径流(产流)起始时间....     

施用EN-1 固化剂后土壤入渗能力评价模型研究

本文以0～30cm和30～100cm土层的填土和黄绵土为供试土壤,研究了EN-1固化剂的施用对土壤入渗能力、土壤结构、土壤持水能力和土壤酸度的影响.以表征土壤结构、土壤持水能力和土壤酸度的指标作为土壤入渗能力评价指标,利用逐步回归分析法,建立了经固化剂处理后的土壤入渗能力评价模型.研究结果表明,EN-1固化剂对土壤物理和化学性质的影响程度与固化剂掺量、土壤类型和土壤的取土层次有关.在评价土壤入渗能力的模型中,除大于0.25mm的毛管饱和水稳性团聚体含量和滞留含水量是共有指标外,其它指标的选取随土壤类型和取土层次的不同而改变.     

南方丘陵区多层土壤结构水平和垂向渗流特征试验与模拟研究

南方丘陵地区地形起伏,上下游田块及田块内部不同层之间土壤质地差异较大,存在复杂的水分转化关系。为揭示该地区田块内多层土壤水分运动规律,在湖北省漳河水库灌区团林灌溉试验站,开展田块变化水层条件下水分通过犁底层垂直入渗以及通过耕作层侧向入渗试验,观测土壤累积入渗量及各层含水率的变化过程;建立基于HYDRUS-2D的土壤水分二维渗流模拟模型。经验证,模型模拟值和田间实测值基本吻合;试验发现由于土壤性质差异,田块犁底层的存在会抑制水流的垂直运动,减少深层渗漏,但同时增强了水流沿耕作层侧向运动的能力。试验期间,水分沿犁底层平均垂向入渗速率为0.094 cm/min,沿耕作层平均侧向入渗速率为0.138 cm/min;入渗稳定后,渗漏水量占田面累积入渗量的21.11%,其中垂直渗漏水量占0.46%,侧向渗漏水量占20.65%,耕作层侧向渗漏水量占侧向渗漏水量的81.06%。结果表明,土壤侧向渗漏对水量损失的贡献较大,控制田块渗漏特别是耕作层侧向渗漏对南方地区节水减排具有十分重要作用。     

Comparison of soil moisture at different depths for drought monitoring based on improved soil moisture anomaly percentage index

To better understand the characteristics and mechanisms of droughts at different drought stages, this study selected the Xiangjiang River Basin in China as the study area, and evaluated soil moisture (SM) at different depths for drought monitoring, through SM data simulated with the variable infiltration capacity (VIC) model. To solve the problem of unreasonable drought/wetness classifications based on the soil moisture anomaly percentage index (SMAPI), an improved soil moisture anomaly percentage index (ISMAPI) was developed by introducing the Box–Cox transformation. The drought/wetness frequency generated by ISMAPI demonstrated preferable spatial comparability in comparison with those from SMAPI. The lag time of ISMAPI relative to the standardized precipitation evapotranspiration index was closely related to soil depth, and was characterized by a fast response in shallow soil layers and a relatively slow response in deep soil layers. SM in shallow soil layers provided a measure for monitoring short-term droughts, whereas SM in deep soil layers provided a better measure for long-term persistent drought events. Furthermore, the occurrence and mitigation time of drought events identified by SM in deep soil layers usually lagged behind that identified by SM in shallow soil layers. Compared with deep SM, SM in shallow soil layers responded faster to meteorological anomalies, thereby resulting in shorter periods of SM persistence in shallow soil layers than in deep soil layers. This can explain the differences of SM at different depths in drought monitoring.     

土石山区山坡降雨入渗产流模型

在分析土石山区下垫面特性的基础上,引入碎石体积比例系数量化土壤中碎石对入渗的影响,并考虑山坡基岩凹凸面及封闭裂隙储留,构建了一种包括植被截留、洼地储留、土壤入渗、壤中流、基岩凹凸面及封闭裂隙储留等计算模块的土石山区山坡降雨入渗产流模型;采用径流小区天然降雨产汇流试验对模型进行验证,并与现有山坡降雨入渗产流模型的模拟结果进行了对比分析。结果表明:与现有模型相比,构建的入渗产流模型可以较好地模拟地表径流强度和土壤入渗率,实测值与模型模拟值较为吻合;暴雨期土壤入渗率的模拟值远小于实测值,可能原因在于该模型忽略了碎石与土壤的直接接触面间可能形成的水流快速通道,未考虑土石山区山坡土壤层和基岩层中可能存在的优先流,模型尚需进一步完善和改进。     

土体初始饱和度对降雨入渗的影响

基于水、气两相流理论,采用有限单元法计算了壤土在不同饱和度下的降雨入渗过程,以研究初始饱和度变化对降雨入渗的影响。数值模拟结果表明:降雨入渗初期孔隙气压会逐渐增大,入渗强度会因孔隙气的顶托作用逐渐减小并最终趋于稳定。稳定后的降雨入渗强度主要取决于土体基质吸力和渗透特性,与土体初始饱和度大小直接相关;入渗强度存在最大、最小值,最大值通常会出现在初始饱和度为0或1时,而最小值所对应的饱和度与土体非饱和特性有关;受土体基质吸力和水、气渗透性的双重影响,入渗强度会先随饱和度的增大而逐渐减小,当降至最小值后,入渗强度又会随饱和度的增大而增大。根据计算结果,提出了一个可计算相对稳定入渗强度的公式。     

半干旱草原型流域土壤入渗过程及转换函数研究

为了进一步探究半干旱草原砂质草甸地土壤入渗过程与影响因素相互作用的关系,以内蒙古锡林河流域为研究区,在厚栗黄土、草甸沼泽土、草原风沙土、石灰性草甸土、淡黑土等5种土壤类型下设置38个土壤入渗试验点以及62个土壤生态调查点,测定了各点位土壤的粒径、容重、有机质、含水率、地下生物量等理化特征。使用Green-Ampt、Philip、Kostiacov、Horton、Mezencev及USDA-NRCS等6种入渗模型模拟入渗过程,结果显示Horton和USDA-NRCS模型模拟效果最好,Adj-R~2分别为0.975和0.911,并利用模拟效果最好的Horton模型计算稳定入渗率,对土壤入渗特性和入渗影响要素进行了主成分和相关性分析并建立土壤转换函数,在此基础上对整个研究区的土壤稳定入渗率进行了1 km×1 km精度的面尺度拓展。研究表明,半干旱草原型流域的土壤入渗主要受到土壤物理属性与外界环境两种要素的影响,使用相关性显著的影响要素建立的土壤转换函数可以较好地模拟半干旱草原型流域的土壤入渗特征值,在小流域尺度上使用土壤转换函数的预测效果相较入渗模型的面尺度拓展更加精细。     

岩土体边坡在降雨入渗作用下的稳定性及影响因素分析

为合理评价降雨入渗对边坡稳定性的影响,选取西南地区某工程边坡建立模型,并结合区内实际降雨工况,运用GeoStudio等软件进行模型建立及参数选取,利用有限元法对考虑降雨历时、强度、主降雨类型、前期降雨的边坡稳定性进行分析。结果表明：短时强降雨在作用时间内会造成边坡稳定性短时间内剧烈下降,给边坡的安全性带来巨大威胁;降雨入渗作用对边坡安全系数有滞后的影响。再通过单因素分析法对边坡稳定性影响因素的敏感度进行对比分析,得出不同岩土层不同影响因素间的敏感性大小关系,可为实际工程中的边坡稳定性分析提供参考。     

The Effect of Geological Heterogeneity and Groundwater Table Depth on the Hydraulic Performance of Stormwater Infiltration Facilities

Urbanization has led to a substantial change in the hydrological cycle of urban catchments. Increased runoff and urban flooding, decreased direct subsurface infiltration and groundwater recharge, deterioration of water quality are among the major effects of this alteration. To alleviate these effects, Low Impact Development (LID) practices have been frequently adopted for stormwater management. Among LID infrastructures, infiltration facilities are particularly challenging to design and model due to the considerable amount of uncertainties related to the hydrogeological configuration of installation sites. To date, analysis on how soil heterogeneity, groundwater table depth, and thickness of the unsaturated zone affect the hydraulic performance of infiltration facilities are lacking. To address this knowledge gap, a series of numerical experiments under transient variably water saturated conditions were performed for a hypothetical infiltration facility. Numerical simulations showed that i) infiltration rates increase considerably as the initial depth of the groundwater table increases, ii) the contribution of the bottom of the facility to the infiltration of water is generally higher than the sides, iii) the presence of a less conducting soil layer at a short depth from the bottom of the facility reduces infiltration rates dramatically, iv) the complete clogging of the bottom of the facility has a dramatic impact on the hydraulic performance, v) the stochastic heterogeneity of the soil controls the overall stormwater infiltration process through the facility, and the hydraulic performance may largely deviate from the case when heterogeneity is absent.

     

基于SWMM的北京市典型城区暴雨洪水模拟分析

以SWMM为基础,选取北京市典型小区,计算不同频率设计暴雨下小区排水效果以及积水、道路坡面流等情况,同时进行不同情景下的暴雨洪水模拟并评价其影响,包括改凸式绿地为平式和凹式、设置蓄洪区等。模拟计算的结果显示,以上3种方式对入渗、径流、洪峰流量、坡面流等均有较大影响,作为城市防洪排水的重要辅助措施,可以极大地缓解排水管道压力,同时削减洪峰、增加入渗。     

On the process of fine sediment infiltration into static gravel bed: A CFD–DEM modelling perspective

The gravel bed clogging, caused by infiltration and accumulation of fine sediment, degrades the river ecology. A proper understanding of the infiltration process, and underlying mechanism and causes, are necessary to take preventive measures. The process of fine sediment infiltration into static gravel bed is studied by distinguishing between bridging and percolation behaviours, as they affect the river ecology and physical processes occurring in the river system differently. However, several contradicting observations, concerning their occurrences, are reported. We employed the unresolved CFD–DEM method to simulate and investigate the infiltration process. The theoretical size ratios, corresponding to different geometrical configurations for a binary mixture of mono-disperse spherical particles, representing bridging and percolation processes, are considered and simulated with and without flowing water effects. The effects of several turbulence models on the infiltration process are also studied. We found that fine sediment infiltration in fluvial deposits is mainly gravity-dominated, supporting Cui's hypothesis that fine sediment infiltration through intra-gravel flow is similar to fine sediment infiltration driven by gravity. In contrast to consensus in the field, our results demonstrate that the occurrences of different infiltration processes (bridging and percolation) seem to be independent of gravel bed thickness, rather depend only on the relative grain size distribution of fine sediment and gravel. However, a precise definition of a ‘thick enough’ gravel bed is necessary to distinguish between bridging and percolation behaviours. Here, we hypothesize a suitable gravel bed thickness, which might be regarded as a ‘thick enough’ gravel bed.     

间歇入渗影响因素的大田试验研究

间歇灌是一种新的地面节水灌溉技术。本文以141组大田连续及间歇单点入渗试验资料为依据,针对陕西关中地区中壤质地土壤,分析了土壤初始含水量、土壤结构及灌水参数等因素对间歇入渗减渗效果的影响。结果表明,土壤初始含水量的大小主要影响入渗过程的初始阶段,对减渗效果影响甚微;随着表土容重增大,减渗率减小;灌水参数对减渗效果有不同程度的影响,其中循环率影响最大。     

Metal concentrations in soil and seepage water due to infiltration of roof runoff by long term numerical modelling.

The qualitative effects of stormwater infiltration on soil and seepage water are investigated with long term numerical modelling. The retention behaviour of different soils and materials used in infiltration devices is determined with batch and column tests. Results of the laboratory tests are adsorption isotherms which represent input data for numerical transport modelling. The long term simulations are performed with combinations of different solutions (types of roof runoff) and infiltration devices (swale and trench) under different hydrogeological conditions. The presented results contain the infiltration of low polluted roof runoff, runoff from a roof with zinc sheets and from a roof with copper sheets concerning the heavy metals zinc, copper and lead. The increase of concentrations in the infiltration body is high. For the infiltrated water, the results show a migration to groundwater only for the low adsorbing soil.     

城市径流雨水渗滤处理设施渗滤层改良研究进展

综述常见的雨水渗滤设施中填料的作用,包括天然材料如沸石、石英砂、木料,废弃材料如煤灰渣、蟹壳,以及人工材料如纤维膜、活性炭和零价铁等;比较分析不同渗滤材料的特性及其用于改良渗滤层时对污染物的去除效果及去除机理,认为传统的渗滤材料(如土壤)难以去除径流雨水中的难降解污染物(如重金属、多环芳烃等),而改良的渗滤材料不但可改善出水效果,且可提高设施处理效率,减少滤料层阻塞。由于不同渗滤材料各有利弊,针对不同的雨水水质及处理要求,多种渗滤材料的配合使用以及对新材料的开发将有益于提高雨水渗滤填料层的处理效果。     

黄土中降雨入渗规律的现场监测研究

已有许多人工降雨试验确定的黄土入渗深度有限,一般很少超过4m,由此认为降雨难以通过正常渗流途径到达地下水位;而是通过裂隙、落水洞等通道灌入深部补给地下水的。然而调查发现,这种入水通道仅在黄土塬边的卸荷区常见,塬的中部很少。为了了解黄土地区地表水以何种方式补给地下水,在甘肃正宁县建立了一个监测站,通过在一深度为10 m的探井井壁上埋设土壤水分计,对天然降雨入渗条件下不同深度黄土层的体积含水率变化情况进行了为期一年的连续监测,同时采用雨量计记录其间的日降雨量。结果表明：2 m以内的浅部土层,土壤水分具有周年的背景变化趋势,该趋势和蒸发量的变化趋势吻合。当日降雨量小于18mm/d时,水分仅在表层循环,对地表以下（>20cm）的含水率几乎没有影响。当日降雨量大于18mm/d时,才会引起土壤含水率骤增,降雨量越大,土壤含水率增幅越大,影响深度越大,随着深度增加,增幅减小,时间上渐有滞后。观测点黄土的浸润带约为2m,2m以下的非饱和黄土中,水分以非饱和渗流或水汽形式迁移,水汽迁移量很小,但不可忽视,当遇到透水性差的古土壤层时,会在其顶部富集,长期作用则可能形成软弱带,诱发黄土滑坡。     

小浪底工程地下厂房三维渗流计算分析

在分析小浪底地下厂房区工程地质和水文地质资料的基础上，根据地下厂房的排渗布置，建立了地下厂房排渗工程的渗流数学模型，通过对具体问题的处理及三维有限元计算，对地下厂房的排渗设计作出评价。计算结果表明：地下厂房排渗工程盎应考虑透水岩层层状分布的特点，厂房上游的排水幕应穿越Ｔ１＾４、Ｔ１＾３－２和Ｔ１＾３－１岩层，特别是Ｔ１＾４和Ｔ１＾３－１两个主要透水层为好。同时，要降低西沟水库对厂房后部尾水洞区的影     

地下水流数值模拟中随机因素的灵敏度分析

本文以待定系数摄动随机有限元法为基础，在以渗透系数、给水度、边界、源汇项为随机变量的条件下，建立了二维潜水非稳定流随机模型，编制了二维摄动随机有限元通用程序。通过对太原盆地地下水系统的随机模拟，分析了渗透系数、给水度、边界、开采量4个随机因子对水头模拟值的影响程度。结果表明，对水头期望值影响的灵敏度：渗透系数最大，其次为给水度和边界值，井开采量最小；对水头方差影响的灵敏度：给水度最大，其次为渗透系数和边界值，井开采量最小；对水头摄动量影响的灵敏度，两个随机参数中渗透系数较大，给水度较小。