Overview of the seismic input at dam sites in China          下载免费PDF全文

Houqun Chen 《地震科学（英文版）》2022,35(5):410-425

The current Chinese national standard, the Standard for Seismic Design of Hydraulic Structures (GB51247), released in 2018, is strictly based on China’s national conditions and dam engineering features. A comprehensive and systematic overview of the basis of the seismic fortification requirements, the framework of the fortification criteria, and the mechanisms of seismic input related to the seismic design of dams are presented herein. We first analyzed and clarified several conceptual aspects in traditional seismic design of dams. Then, for the seismic input at the dam site described in the first national standard for hydraulic structures, we expounded innovative concepts, ideas, and methods to make relevant provisions more realistic and practical and discussed whether reservoir earthquakes must be included in the seismic fortification framework of dams. This study seeks to incorporate seismic input at the dam site into traditional seismic design practice to promote its improvement from the quasi-static method to the dynamic method and from the closed vibration system to an open wave propagation system, to ensure that the seismic design of dams becomes more reasonable, reliable, scientific, and economic.  相似文献   

低坝影响下的流场与淤积形态特性试验研究          下载免费PDF全文

晏自立  朱德军  段炎冲  张鹏  李丹勋 《水科学进展》2021,31(6):917-926

为研究径流式低坝影响下的水流流动与泥沙淤积特性,开展水槽试验,基于图像测量技术,获取并解析坝附近区域流场信息及典型淤积形态。结果表明：坝前附近流段纵向流速在垂线上出现衰减区,减幅随水流强度增大而减小;坝顶断面纵向和垂向流速沿垂线的分布均呈现显著的分区特性,分区界限几乎不受水流强度的影响;随坝顶水深增加,坝下游漩涡涡心向下游及河底移动,面积和强度皆增大;坝上游淤积形态特性对水流强度的变化非常敏感,在较低强度来流下,呈接近坝体的稳定曲面斜坡,而在高强度来流下,不形成稳定淤积体;坝下游形成动态稳定的淤积斜坡,纵剖表面线呈抛物线规律,随来流强度变异程度小。  相似文献   

(Dis)Connectivity in catchment sediment cascades: a fresh look at the sediment delivery problem   总被引：2，自引：0，他引：2  

Kirstie Fryirs 《地球表面变化过程与地形》2013,38(1):30-46

The concept of the sediment delivery problem was introduced into the literature in 1983 by Des Walling. This concept describes how only a fraction of sediment eroded within a catchment will reach the basin outlet and be represented as sediment yield, and that sediment storage mechanisms operating within a catchment explain this discrepancy. Since this paper was published, geomorphologists have been examining in great detail the fate of sediment eroded from the landsurface, and the pathways and timeframes of sediment transport and storage in catchments. However, to fully understand the internal dynamics of sediment flux requires a ‘fresh look at the sediment delivery problem’. A framework is required that can incorporate the various processes involved in sediment movement from source areas through a basin to its outlet, and can take account of the spatial distribution of, and timeframes over which, these processes operate. This paper presents a conceptual framework for analysis of catchment (dis)connectivity that incorporates both spatial and temporal variability in the operation of the sediment cascade. This approach examines where blockages occur to disrupt these longitudinal, lateral and vertical linkages in catchments. Depending on the position of blockages (termed buffers, barriers and blankets), and their sediment residence time, various parts of a catchment may be actively contributing sediment to the sediment cascade and be switched on, or inactive and switched off. This paper discusses how such a framework can be used to model response times to disturbance and explain the manifestation of geomorphic change in catchments. The paper then highlights challenges geomorphologists face in applying such a framework to understand the internal dynamics of the catchment sediment cascades, and forecast how environmental change might affect the operation of sediment fluxes into the future. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A Case Study on MJO Energy Transport Path in a Local Multi-scale Interaction Framework     

Yuanwen ZHANG  Guiwan CHEN  Jian LING  Shenming FU  Chongyin LI 《大气科学进展》2021,38(11):1929-1944

A new local kinetic energy (KE) budget for the Madden-Julian Oscillation (MJO) is constructed in a multi-scale framework. This energy budget framework allows us to analyze the local energy conversion processes of the MJO with the high-frequency disturbances and the low-frequency background state. The KE budget analysis is applied to a pronounced MJO event during the DYNAMO field campaign to investigate the KE transport path of the MJO. The work done by the pressure gradient force and the conversion of available potential energy at the MJO scale are the two dominant processes that affect the MJO KE tendency. The MJO winds transport MJO KE into the MJO convection region in the lower troposphere while it is transported away from the MJO convection region in the upper troposphere. The energy cascade process is relatively weak, but the interaction between high-frequency disturbances and the MJO plays an important role in maintaining the high-frequency disturbances within the MJO convection. The MJO KE mainly converts to interaction KE between MJO and high-frequency disturbances over the area where the MJO zonal wind is strong. This interaction KE over the MJO convection region is enhanced through its flux convergence and further transport KE to the high-frequency disturbances. This process is conducive to maintaining the MJO convection. This study highlights the importance of KE interaction between the MJO and the high-frequency disturbances in maintaining the MJO convection.  相似文献   

On the use of pore pressure measurements in safety reassessments of concrete dams founded on rock     

《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2013,7(2):117-128

In probabilistic stability analyses of concrete dams founded on rock, the uplift pressure is often a parameter of major importance. In previous literature, it has been suggested that assessing uplift with pore pressure measurements, instead of using empirical assumptions, could improve the calculated dam safety. This paper presents a coherent methodology to investigate whether incorporating pore pressure measurements has any impact on the calculated dam safety, based on Bayesian linear regression of pore pressure data in combination with series-system and the first-order reliability method. The study concludes that the probability of sliding failure is closely related to the probability of an extreme increase in uplift. Hence, measured uplift should only be incorporated while this probability remains sufficiently small, which requires proper programs both for uplift monitoring and for maintenance of drains and grout curtains.  相似文献   

Climate change impacts on groundwater hydrology – where are the main uncertainties and can they be reduced?     

J.C. Refsgaard  T.O. Sonnenborg  M.B. Butts  J.H. Christensen  S. Christensen  M. Drews 《水文科学杂志》2013,58(13):2312-2324

ABSTRACT

This paper assesses how various sources of uncertainty propagate through the uncertainty cascade from emission scenarios through climate models and hydrological models to impacts, with a particular focus on groundwater aspects from a number of coordinated studies in Denmark. Our results are similar to those from surface water studies showing that climate model uncertainty dominates the results for projections of climate change impacts on streamflow and groundwater heads. However, we found uncertainties related to geological conceptualization and hydrological model discretization to be dominant for projections of well field capture zones, while the climate model uncertainty here is of minor importance. How to reduce the uncertainties on climate change impact projections related to groundwater is discussed, with an emphasis on the potential for reducing climate model biases through the use of fully coupled climate–hydrology models.