Evaluation of dynamic characteristics of silt in Yellow River Flood Field after freeze-thaw cycles

Frothing is a main disease of highways in Yellow River Flood Field, due to the loss of dynamic strength of roadbed soils under the couple effects of temperature, salt, and vehicle traffic load. This is strongly linked to the dynamic characteristics of silt in this region. To analyze these couple effects on the dynamic characteristics of silt, a series of tests(i.e., freeze-thaw cycling tests, vibration triaxial tests and ultrasonic wave velocity tests) were conducted and two kinds of silt(i.e., salt-free and 3%-salt silt) were designed. The results indicate that the dynamic shear strength and dynamic modulus decrease with increasing freeze-thaw cycles, while the damping ratio simultaneously increases. Furthermore, compared to salt-free silt, the decrement of dynamic shear strength and dynamic modulus of silt with 3% salt is more significant, but the damping ratio of 3%-salt silt is larger. In ultrasonic wave velocity tests, ultrasonic wave velocity of frozen soil specimens decreases as the number of freeze-thaw cycles increases. Based on the results of ultrasonic wave velocity tests, a preliminary model is proposed to evaluate damage of silt through field measurement ultrasonic data. The study could provide a theoretical basis for the treatment of silty soil highway.

Yellow River Valley flood and drought disaster：spatial－temporal distribution prediction and early－warning

By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features of severe flood and drought in Yellow River Valley. Statistical methods of varianceanalysis, probability transition and the principles of scale correspondence were employed tocomprehensively predicate 90's tendency of severe flood and drought in the Yellow River Valley. In addi-tion, this paper pointed out the possible breaching dikes, sectors and the flooding ranges by future's se-vere flood, meanwhile estimating the associated economic losses and impact to environment.

The characteristics of dike-break flood in different scenarios of the lower Yellow River based on numerical simulations

The lower Yellow River still faces the threat of flood due to the unusual precipitation caused by global environmental change, river channel sedimentation, hidden danger in the dike and unfavorable river regime of ＂hanging river＂. According to the characteristics of the dike-break flood of the Yellow River, this paper has simulated, in six different scenarios, the dike-break flood routing by inputting the terrain data, typical historical flood data and land use data of study area to two-dimensional unsteady flow model. The results show that： firstly, the routing process of flood will occupy other rivers on the way and return to the rivers after reaching the lower reaches; secondly, in the same river reach, flood inundating area of north band is bigger than that at corresponding location of south bank under the same historical flood; thirdly, it is different in the degree of flood inundation in different regions due to different geographical locations in flood plain; fourthly, the area of mainstream where flood is deep and flow velocity is quick is relatively smaller, but the area of non-mainstream, where flood is shallow and flow velocity is slow, is relatively big; and finally, the possible influenced area of the dike-break flood is 141,948 km^2.

Natural Disasters of the Lower Reaches of Yellow River during the Longshan Period——The Natural Background of Dayu's Flood Control

It is very important to study the archaeological culture and origin of civilization in ancient China.The changes of the channels in the lower reaches of the Yellow River in the prehistoric period are part of the natural environmental background of the development of the ancient civilization in that area to be explored.This paper presents a series of legends,indications,scientific evidence,and macroscopic geographical background information of the evolution in the lower reaches of the Yellow River during the Longshan period.At first the river flowed from Northern Henan and Hebei to southwestern Shandong Province and Northern Anhui–Jiangsu provinces,and the mainstream of the Yellow River changed from the southeast to return to the north and flowed into the Bohai Sea in the late Longshan Period.During this period,floods were frequent.Various ethnic groups in the northern China plains suffered natural disasters and made great migrations which also contributed to the ethnic exchanges and integration.The people of the Central Plains made more dynamic adjustments in the relationship between mankind and the land by primitively escaping from the water and self–defensively controlling the rivers then to maintaining the local ecological environment by large–scale flood control measures,which promoted the settlement of Shandong,Henan,Jiangsu and Anhui provinces,the urban cultural development,and social evolution.Based on these events,the culture symbol of Dayu's Flood Control could be formed.

隧道施工引发粉土地面沉降模拟与分析

为研究黄泛区粉土地层内开挖双线地铁隧道对地上及其周边地面沉降的影响,以某双线地铁隧道开挖工程为例,考虑地下水、隧道间距对地面沉降的影响,采用流固耦合数值方法和理论分析方法对隧道施工引起的地面沉降规律进行分析。将数值模拟数据与Peck公式进行反演计算,并考虑隧道间隔和埋深的影响提出修正Peck公式,再结合叠加原理建立适用于双线隧道开挖引起地面沉降的修正叠加公式。结果表明:隧道开挖扰动地层将引起超静孔隙水压力现象;数值模拟与理论计算得到隧道间隔为4 m时,地面沉降曲线呈现“V”型,隧道间隔为8 m、12 m时,则沉降曲线呈现“U”形;粉土内开挖双线地铁隧道,地面容易受到扰动且沉降量大,随着隧道间距的增加,隧道上方土体沉降量逐渐减小;基于修正Peck公式计算结果与数值模拟结果基本一致,相对误差在3%左右,表明该公式具有很好的实用性。研究可为粉土地区隧道及地下工程建设提供理论依据和技术支撑。

黄河防汛抢险技术虚拟试验场构建技术研究

黄河防汛抢险技术试验场由“虚”“实”两部分组成,虚拟平台是实体试验场的数字孪生体。以建设黄河防汛抢险技术虚拟试验场为目标,依托总体布置方案对场地结构进行分解,针对7组模块化构件,通过实体尺寸参数驱动三维模型,同时根据附加材质对不同构件分别进行多边形建模和曲面建模;采用C4D等工具构建三维场景;采用光滑粒子流体动力学(Smoothed Particle Hydrodynamics,SPH)方法求解纳维—斯托克斯方程组,基于Realflow软件在蓄水池内生成流体粒子和网格,在时间、空间两个维度获取粒子水力要素;采用Octane render对三维场景和流体网格进行渲染。最终构建完成强真实感、高可信度的试验场虚拟场景。

黄河流域防洪形势与对策

在全球极端暴雨频发背景下,黄河流域防洪安全对保障全面建设社会主义现代化国家具有十分重要的意义。分析了黄河流域防洪安全现状及存在问题,剖析了保障黄河长治久安面临的严峻挑战,以确保堤防不决口、确保河床不抬高、让黄河成为造福人民的幸福河为目标,提出了新时期黄河流域防洪减灾体系的对策措施,论证了黄河长治久安的前景和保障思路。

新形势下黄河下游控导工程建设思路探讨

2021年黄河中下游发生历史罕见秋汛洪水,下游控导工程经受了长历时中常洪水过程的检验。针对部分控导工程在洪水过程中暴露出来的坝顶高度不够、根石不足、裹护段长度不够、抢险道路交通能力不足等问题,从工程设计、管理上进行分析,认为水沙条件变化、控导工程设计流量降低、河道下切、平滩流量增大、抢险机械设备大型化等是出现这些问题的原因,并提出了今后避免类似问题发生的措施和建议。

黄河秋汛洪水防御实践与思考

黄河秋汛洪水相比夏汛洪水,具有洪峰低、持续时间长、含沙量低的特点。2021年黄河发生严重秋汛,干支流、中下游汛情多区域交织,多场次叠加,洪量之大、历时之长,历史罕见。文章以2021年黄河秋汛洪水为例,从水库群精细联合调度、洪水防御工作部署、防洪调度成效等方面回顾了秋汛洪水防御工作,总结了此次洪水防御过程中的技术支撑及组织保障经验,展望了新形势下秋汛洪水防御工作重点,为今后秋汛洪水防御工作提供借鉴参考。

黄河下游花园口至孙口河段高效输沙洪水阈值研究

河流能量耗散率变化反映了河道水沙输移能力以及河床形态的调整规律。本文研究区域为黄河下游花园口至孙口河段,从能量耗散角度出发,结合对实测资料的统计分析,探究了河流边界阻力能耗率与来水来沙、断面形态以及河床稳定性之间的定量关系,并基于边界阻力能耗率与河床稳定性双重指标,确定了花园口至孙口河段的高效输沙洪水阈值。研究结果表明:流量是影响边界阻力能耗率的主要因素,并与边界阻力能耗率的幂次呈线性相关;随着流量增大到2000 m^(3)/s以上,边界阻力能耗率随含沙量增加呈先减弱后增强的趋势。大流量条件下边界阻力能耗率与宽深比呈负相关关系,花园口与夹河滩断面形态复杂,相关性较弱;相比之下高村与孙口断面形态简单,相关性增强。非恒定水沙条件下的河床大多处于失稳状态,在综合考虑河床形态稳定及边界阻力能耗率最低的前提下,计算得出花园口至孙口河段的洪水高效输沙临界流量约为1500 m^(3)/s,含沙量约为23 kg/m^(3)。

黄河下游花园口以上河道滞沙指标研究

水沙搭配关系是影响黄河下游河道冲淤调整的重要因素,局部河段滞沙则是改善下游水沙关系的有效手段之一。小浪底水库运用后,河槽沿程冲刷不均衡,河床粗化,细沙补给不足,输沙效率明显降低。分析黄河下游河道冲淤特性及水沙演进规律,建立不同类型洪水滞沙河段(花园口以上河段)与排洪瓶颈河段(高村—艾山河段)的冲淤关系。基于滞沙对河道行洪和稳定性的影响,以排洪瓶颈河段不淤积为约束,提出洪水滞沙的水沙优化配置指标。中泥沙洪水滞沙指标为:洪水平均流量为1800~3700 m^(3)/s,平均含沙量为66~235 kg/m^(3)。

明清时期黄河下游决泛区的时空变化及其人地关系规律

明清黄河下游决泛水沙对颍河沿岸平原地区的环境和地表塑造的影响相对较轻,颍河两岸未形成显性决口扇地貌,历次黄泛水沙一般未越过颍河向西南漫溢,颍河干流长期作为黄泛水沙的良好容受体及其向西南蔓延扩张的界隔线。涡河沿岸地区受到明清黄河独流干道决口水沙向南泛滥及涡河本身被黄水夺溜时决泛水沙的双重影响,黄河主故道南岸核心决口扇的边缘带与沿涡次级决口扇相互交集,在涡河地区形成叠加型决口扇地貌,涡河干流长期作为黄泛重灾区与影响轻微地区的分界线。大型湖泊洼地的积水面通常与黄泛决口扇的前缘互为进退,鱼台县的土壤分布及农作物结构特征,较好地证明了南四湖洼地长期作为黄泛决口扇的边界,南四湖是明清时期黄泛水沙向北蔓延扩张的重要蓄洪区和调剂区。

黄河下游漫滩洪水滩槽分流比变化及其影响因素分析

采用实测资料分析的方法,研究了黄河下游漫滩洪水滩槽分流比变化及其影响因素。研究结果表明:花园口4次漫滩洪水滩槽分流比均值为0.18,说明主槽是黄河下游泄洪排沙的主体;黄河下游上宽下窄,滩槽分流比沿程变大。1986年后,下游河道萎缩,平滩流量下降,滩槽分流比增大;2000年后,下游河道冲刷,平滩流量增大,滩槽分流比减小。滩槽分流比随滩槽糙率比的增大而减小,随滩槽水面宽度比、滩槽水深比的增大而增大。提高主槽过流能力,必须采用综合治理措施维护下游主槽适宜规模的平滩流量;提高滩地过流能力,必须降低人类活动对滩地的影响,给滩地留有足够的行洪空间,确保全断面行洪安全。

黄河源区汛期降水径流序列多尺度小波分析

基于黄河源区15个地面站点日降水数据、唐乃亥水文站逐日径流数据以及小波分析方法,分析了黄河源区1961—2020年汛期降水和径流的周期规律、变化趋势及相关关系。结果表明,1)黄河源区近60 a汛期降水、径流均存在多时间尺度的变化特征,且不同时间尺度汛期降水、径流丰枯变化趋势均不同;2)汛期降水、径流序列均具有63 a左右、35 a左右特征时间尺度的主周期,两个时间尺度下的平均周期分别为41、25 a左右,汛期降水、汛期径流具有一定的正相关性;3)在63 a特征时间尺度可预测2020年之后未来5~10 a内黄河源区汛期降水、径流整体均呈减小趋势。

汛期与非汛期水沙条件对黄河下游不同河段过流能力的影响

20世纪80年代以来黄河下游水沙输移特性显著改变,下游河道经历强来沙作用下的持续淤积与小浪底水库调控下的持续冲刷过程。基于黄河下游1986—2020年实测水沙数据与固定断面地形,计算了河段尺度的平滩流量,量化了汛期与非汛期水沙过程对各河段过流能力的相对贡献。结果表明:①小浪底枢纽运行前水流冲刷强度随时间减弱,下游河道呈汛期淤积、非汛期冲刷的整体淤积态势,平滩流量持续减小,最小过流能力小于2000 m^(3)/s。②小浪底枢纽运行后水流冲刷强度显著增大,尤其在非汛期,对河床冲刷产生重要影响;各河段过流能力显著恢复,其中游荡段恢复最为迅速。③各河段平滩流量与前5 a汛期、非汛期平均水流冲刷强度呈良好的幂律关系,该关系能较好地反映汛期与非汛期累积水沙过程对过流能力的综合影响。④小浪底枢纽运行后,非汛期水沙条件对平滩流量的贡献率增大,尤其是对游荡段具有重要影响(占比53%),对过渡段与弯曲段贡献则较小(占比不到20%)。

黄河下游游荡河段高含沙洪水期输沙规律研究

黄河下游河床长期处于淤积抬升状态,其冲淤演变规律对于下游河道治理有着重要影响。因此,快速预测不同量级高含沙洪水各河段的冲淤量以及判断高含沙洪水期黄河下游游荡河段冲淤影响很有必要。根据1960—2021年54场高含沙洪水的实测水沙资料,分析高含沙洪水期黄河下游游荡河段下站输沙率与上站流量、含沙量、输沙率之间的相关关系并建立关系式,系统地研究高含沙洪水的输沙规律。结果表明,下站输沙率与上站输沙率存在极强的相关性,进一步按来沙系数分级得到高含沙洪水期的输沙率公式,能够很好地模拟冲淤过程,极大地提高了与实测水沙资料的贴合度。以小浪底水文站为黄河下游游荡河段的进口控制水文站,采用按来沙系数分级所求的输沙率关系式能够较准确推求花园口站、夹河滩站、高村站的输沙率,从而计算小浪底—花园口、花园口—夹河滩和夹河滩—高村河段的累计冲淤量。

Sediment delivery ratio and its uncertainties on flood event scale:Quantification for the Lower Yellow River

Sediment delivery ratio(SDR)for fluvial rivers was formulated with sediment rating curve.The observed data of SDR on flood event scale of the Lower Yellow River(LYR)were adopted to examine the formulation and to calibrate the model parameters.A regression formula of SDR was then established and its 95%prediction interval was accordingly quantified to represent its overall uncertainties.Three types of factors including diversity of the incoming flow conditions,river self-regulation processes,and human activities were ascribed to the uncertainties.The following were shown:(1)With the incoming sediment coefficient(ISC)being a variable,it was not necessary to adopt the incoming flow discharge as the second variable in the formulation of SDR;and(2)ISC=0.003 and therefore SDR=2 might be a threshold for distinguishing the characteristics of sediment transport within the LYR.These findings would highlight sediment transport characteristics on the scale of flood event and contribute to uncertainty based analysis of water volume required for sediment transport and channel maintenance of the LYR.

黄泛区非饱和粉土动模量和阻尼比特性研究

黄泛区粉土水敏感性强,力学性质独特,易受振动荷载的影响。本文通过循环三轴试验,研究固结围压和饱和度对黄泛区粉土动模量、阻尼比特性的影响。研究结果表明,黄泛区粉土骨干曲线符合双曲线关系;随动应变的增大,黄泛区粉土动弹性模量先急剧减小而后逐渐趋于稳定;随固结围压的增大和饱和度的减小,粉土动弹性模量逐渐增大,阻尼比则逐渐减小;二元线性方程可用于估算最大动弹性模量随固结围压和饱和度的变化规律,修正Hardin-Drnevich模型可较为准确预测黄泛区非饱和粉土的动弹性模量和阻尼比。本研究可为黄河流域工程建设提供理论支撑。

Efficiency of sediment transport by flood and its control in the Lower Yellow River

This paper presents the characteristics of sediment transport by flood in the Lower Yellow River with the reach from Huayuankou to Gaocun, which is regarded as a typical braided pattern. The Artificial Neural Network Model on Water Use for Sediment Transport (WUST) by flood was established based on the measured data from 1980 to 1998. Consequently, simulations of controlling process of sediment transport by flood were made in terms of the control theory under different scenarios. According to the situation of sediment transport by flood in the Lower Yellow River, Open-Loop control system and feedback control system were adopted in system design. In the Open-Loop control system, numerical simulations were made to reveal the relationship between average discharge of flood and the WUST with varying sediment concentrations. The results demonstrate that sediment concentration has significant influence on the controlling process of flood flow to WUST. It is practical and efficient to control WUST if sediment concentration is less than 20 kg/m3. In the feedback control system, controlling processes of sediment concentration and flood discharge for sediment transport were simulated respectively under given conditions, and it was found that sediment transport process could be controlled completely by sediment concentration and discharge at the inlet of the reach from Huayuankou to Gaocun. Using the same method, controlling processes of sediment transport by flood in other reaches in the Lower Yellow River were also simulated. For the case of sediment concentration being 20 kg/m3, the optimized controlling discharge ranges from 2390 to 2900 m3/s in the lower reach of Huayuankou. This study is also of significance to flood control and flushing sediment in the Lower Yellow River with proper operation modes of Xiaolangdi Reservoir.

1938年黄泛事件中赵口掘堤点选择新探

1938年6月国民政府为阻敌西进,先后在黄河赵口和花园口河段掘开大堤,引水南泛。相比于花园口掘堤点选择的偶然,赵口则是经慎重商议后首选的掘堤地点,一定程度上体现了决策者对黄泛的态度。通过整理掘堤者的回忆资料及对赵口河段大堤、地形的复原,本文认为赵口掘堤点的选择经历了“掘堤区-掘堤河段-掘堤点”范围逐步精确的过程,军事形势、地势、民生和河道微地形是掘堤点选择的主要影响因素。