库岸斜坡失稳及其涌浪灾害风险分析          下载免费PDF全文

罗冠枝  高文伟  王国卫  蒋明光  陈全明 《中国地质灾害与防治学报》2020,31(1):8-17

库岸斜坡失稳及其引发涌浪问题是库岸斜坡灾害的重要研究部分,开展库岸斜坡失稳及其涌浪灾害风险分析研究对指导库岸斜坡防灾减灾具有重要意义。以湖南省麻阳县大水冲水库滑坡为例,探讨库岸斜坡失稳引发涌浪灾害的分析方法,采用Geostudio软件进行10年和50年一遇5日累积降雨的滑坡稳定性模拟分析,绘制滑坡影响范围内建筑物风险变化图和室内人员风险变化图。总结了在最危险工况下,大水冲水库滑坡总经济风险为249.3万元,室内人员的风险值达到27.8,并有产生翻坝的可能,但对沟口居民和水库坝体破坏的风险低。  相似文献   

深海弯曲水道内部一种特殊的沉积单元:凹岸坝     

冯潇飞  赵晓明  谭程鹏  齐昆  谢涛  张迎春  陆文明  徐睿 《沉积学报》2020,38(2):440-450

在深海水道研究过程中,识别出深海弯曲水道内部存在一种特殊的沉积单元--凹岸坝,基于尼日尔三角洲陆坡区浅层高频三维地震资料,利用地震相分析技术,探究了凹岸坝的沉积结构特征和形成机制,讨论了其与水道弯曲丘(nested mounds)、曲流河凹岸滩坝之间的差异。研究结果表明:凹岸坝是分布于曲率较大、以垂向加积为主的末期水道弯曲凹岸处的坝体沉积单元,该沉积单元在地震剖面上表现为强振幅、连续性较好的反射特征,其内部沉积界面倾向于水道弯曲凸岸处,倾角约1°~20°,且在凹岸弧顶处达到最大值。凹岸坝形成的关键在于惯性作用,其造成水道内部重力流流体在弯曲处发生溢岸,导致流量减少,流体动能相应降低,流体携砂能力小于沉积物负载,造成沉积物快速沉降,从而形成凹岸坝。由于凹岸坝是一种连续性较好的砂体沉积,所以其可成为潜在的、储集性能较好的油气储集体。  相似文献   

Scales and magnitude of hyporheic,river–aquifer and bank storage exchange fluxes          下载免费PDF全文

Roger H. Cranswick  Peter G. Cook 《水文研究》2015,29(14):3084-3097

Many studies have investigated the exchange processes that occur between rivers and groundwater systems and have successfully quantified the water fluxes involved. Specifically, these exchange processes include hyporheic exchange, river–aquifer exchange (groundwater discharge and river loss) and bank storage exchange. Remarkably, there are relatively few examples of field studies where more than one exchange process is quantified, and as a consequence, the relationships between them are not well understood. To compare the relative magnitudes of these common exchange processes, we have collected data from 54 studies that have quantified one or more of these exchange flux types. Each flux value is plotted against river discharge at the time of measurement to allow the different exchange flux types to be compared. We show that there are positive relationships between the magnitude of each exchange flux type and increasing river discharge across the different studies. For every one order of magnitude increase in river discharge, the hyporheic, river–aquifer and bank storage exchange fluxes increase by factors of 2.7, 2.9 and 2.5, respectively. On average, hyporheic exchange fluxes are almost an order of magnitude greater than river–aquifer exchange fluxes, which are, in turn, approximately four times greater than bank storage exchange fluxes for the same river discharge. Unless measurement approaches that can distinguish between different types of exchange flux are used, there is potential for hyporheic exchange fluxes to be misinterpreted as river–aquifer exchange fluxes, with possible implications for water resource management decisions. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Dynamic river–groundwater exchange in the presence of a saline,semi‐confined aquifer          下载免费PDF全文

N. P. Unland  I. Cartwright  E. Daly  B. S. Gilfedder  A. P. Atkinson 《水文研究》2015,29(23):4817-4829

Understanding groundwater–surface water exchange in river banks is crucial for effective water management and a range of scientific disciplines. While there has been much research on bank storage, many studies assume idealized aquifer systems. This paper presents a field‐based study of the Tambo Catchment (southeast Australia) where the Tambo River interacts with both an unconfined aquifer containing relatively young and fresh groundwater (<500 μS/cm and <100 years old) and a semi‐confined artesian aquifer containing old and saline groundwater (electrical conductivity > 2500 μS/cm and >10 000 years old). Continuous groundwater elevation and electrical conductivity monitoring within the different aquifers and the river suggest that the degree of mixing between the two aquifers and the river varies significantly in response to changing hydrological conditions. Numerical modelling using MODFLOW and the solute transport package MT3DMS indicates that saline water in the river bank moves away from the river during flooding as hydraulic gradients reverse. This water then returns during flood recession as baseflow hydraulic gradients are re‐established. Modelling also indicates that the concentration of a simulated conservative groundwater solute can increase for up to ~34 days at distances of 20 and 40 m from the river in response to flood events approximately 10 m in height. For the same flood event, simulated solute concentrations within 10 m of the river increase for only ~15 days as the infiltrating low‐salinity river water drives groundwater dilution. Average groundwater fluxes to the river stretch estimated using Darcy's law were 7 m³/m/day compared with 26 and 3 m³/m/day for the same periods via mass balance using Radon (²²²Rn) and chloride (Cl), respectively. The study shows that by coupling numerical modelling with continuous groundwater–surface water monitoring, the transient nature of bank storage can be evaluated, leading to a better understanding of the hydrological system and better interpretation of hydrochemical data. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Uncertainty and sensitivity in a bank stability model: implications for estimating phosphorus loading          下载免费PDF全文

Roderick W. Lammers  Brian P. Bledsoe  Eddy J. Langendoen 《地球表面变化过程与地形》2017,42(4):612-623

Eutrophication of aquatic ecosystems is one of the most pressing water quality concerns in the United States and around the world. Bank erosion has been largely overlooked as a source of nutrient loading, despite field studies demonstrating that this source can account for the majority of the total phosphorus load in a watershed. Substantial effort has been made to develop mechanistic models to predict bank erosion and instability in stream systems; however, these models do not account for inherent natural variability in input values. To quantify the impacts of this omission, uncertainty and sensitivity analyses were performed on the Bank Stability and Toe Erosion Model (BSTEM), a mechanistic model developed by the US Department of Agriculture – Agricultural Research Service (USDA‐ARS) that simulates both mass wasting and fluvial erosion of streambanks. Generally, bank height, soil cohesion, and plant species were found to be most influential in determining stability of clay (cohesive) banks. In addition to these three inputs, groundwater elevation, stream stage, and bank angle were also identified as important in sand (non‐cohesive) banks. Slope and bank height are the dominant variables in fluvial erosion modeling, while erodibility and critical shear stress had low sensitivity indices; however, these indices do not reflect the importance of critical shear stress in determining the timing of erosion events. These results identify important variables that should be the focus of data collection efforts while also indicating which less influential variables may be set to assumed values. In addition, a probabilistic Monte‐Carlo modeling approach was applied to data from a watershed‐scale sediment and phosphorus loading study on the Missisquoi River, Vermont to quantify uncertainty associated with these published results. While our estimates aligned well with previous deterministic modeling results, the uncertainty associated with these predictions suggests that they should be considered order of magnitude estimates only. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

库区陡峻土质岸坡路基塌岸预测     

王哲 《中国地质灾害与防治学报》2011,22(2):39-44

对山区顺直陡峻岸坡路基塌岸的预测,与普通图解法比较,采用考虑土体内聚力的图解法可有效避免解算难以收敛的问题,更为符合塌岸的真实形态。通过预测实例的分析发现：天然休止角的提高可大幅减小塌岸范围;水下磨蚀角的提高则可有效减小塌岸深度;合理调节运行水位变幅,对控制塌岸范围和深度较为理想;而通过小范围抬高公路线位来控制塌岸的效果并不明显。对塌岸影响因素的深入分析,为塌岸段路基的治理提供了合理的思路。  相似文献   

川西北地区下三叠统飞仙关组滩相储层的形成条件分析     

崔卫东 《地质与资源》2011,20(1):56-61

鲕粒滩相碳酸盐岩作为储层的气藏是川西北地区下三叠统飞仙关组地层中最主要的气藏类型.影响飞仙关组滩相储层形成的条件较多,主要受构造作用、沉积作用和成岩作用的影响.分析认为同生断裂导致的地貌升降运动对滩体的展布有着明显的控制作用,上升盘边缘易于滩体的形成与演化;高能沉积相带的台地边缘鲕粒滩最有利于储层的形成与演化;经过白云...  相似文献   

杭州湾北岸岸滩变化对海平面上升的响应——以龙泉—南竹港岸段为例     

施伟勇  许雪峰  应剑云  羊天柱 《海洋学研究》2011,29(4):77-82

相对海平面上升引发的海岸潜在侵蚀是海岸带资源利用与规划的重点关注内容.基于杭州湾北岸龙泉—南竹港岸段实测断面资料,利用历史岸线后退和淹没法则计算法分析了该地区的海岸变化对海平面上升的响应.结果表明:近10 a来岸滩呈侵蚀后退趋势,年侵蚀速率为3.7～5.7 m/a,相对海平面上升对岸滩迁移后退的贡献为2％～6％;未来1...  相似文献   

均质土岸坡崩塌与河床冲淤交互过程试验     

李国敏  余明辉  陈曦  胡呈维 《水科学进展》2015,26(1):66-73

在弯道水槽中展开系列试验,研究水力冲刷过程中均质土岸坡冲刷崩塌输移与河床冲淤过程及其影响因素。该过程及变化特征可描述为:水下坡面侵蚀及坡脚淘刷导致岸坡失稳崩塌;暂时堆积在凹岸坡脚处的崩塌体加剧附近水流紊动程度利于其输运与分解;分解后较粗的颗粒随弯道螺旋流以推移质形式被输移至下游凸岸落淤,较细的颗粒大部分都随水流以悬移质形式被携带至下游出口;水流结构随岸坡及河床变形而调整;如此循环往复。试验成果进一步表明:冲刷状态下,试验材料黏性越小、近岸流速越大、作用时间越长,岸坡冲刷崩塌量及河床冲刷量都越大;同条件下岸坡冲刷崩塌总量大于河床冲刷总量,且河床相对冲刷率随岸坡冲刷崩塌量的增大而减小,数值范围为0.40~0.92。  相似文献   

Seismic random noise attenuation and signal-preserving by multiple directional time-frequency peak filtering     

《Comptes Rendus Geoscience》2015,347(1):2-12

Time-frequency peak filtering (TFPF) is an effective method for seismic random noise attenuation. The linearity of the signal has a significant influence on the accuracy of the TFPF method. The higher the linearity of the signal to be filtered is, the better the denoising result is. With this in mind, and taking the lateral coherence of reflected events into account, we do TFPF along the reflected events to improve the degree of linearity and enhance the continuity of these events. The key factor to realize this idea is to find the traces of the reflected events. However, the traces of the events are too hard to obtain in the complicated field seismic data. In this paper, we propose a Multiple Directional TFPF (MD–TFPF), in which the filtering is performed in certain direction components of the seismic data. These components are obtained by a directional filter bank. In each direction component, we do TFPF along these decomposed reflected events (the local direction of the events) instead of the channel direction. The final result is achieved by adding up the filtering results of all decomposition directions of seismic data. In this way, filtering along the reflected events is implemented without accurately finding the directions. The effectiveness of the proposed method is tested on synthetic and field seismic data. The experimental results demonstrate that MD–TFPF can more effectively eliminate random noise and enhance the continuity of the reflected events with better preservation than the conventional TFPF, curvelet denoising method and F–X deconvolution method.  相似文献