东营凹陷北带东部古近系近岸水下扇储集物性演化及其油气成藏模式

以东营凹陷北带东部沙河街组三段、四段近岸水下扇为例,应用多种方法求取近岸水下扇有效储层物性下限与埋藏深度的定量函数关系,以此为基础研究了近岸水下扇不同亚相的孔隙度随深度的演化及其对油气成藏的控制作用。埋藏深度小于3200m的近岸水下扇扇根、扇中、扇缘亚相均发育有效储层,主要形成"自生自储"或"古生新储"型构造油气藏或构造-岩性油气藏。埋藏深度大于3200m的近岸水下扇扇根砂砾岩物性低于有效储层物性下限,不发育有效储层,可作为油气侧向封堵层,扇中砂砾岩有效储层发育。物性变化使扇中亚相依靠扇根的侧向封堵和湖相泥岩的封盖形成"自生自储"型岩性油气藏,具有"扇缘输导、扇中富集、扇根封堵"的油气成藏特征。     

Determination of noise spectra from strong motion data recorded in Greece

A large number of strong ground motions inGreece have been recorded by analogaccelerographs. The processing of analogstrong motion recordings and conversion toa digital form introduces noise in thesignal, due to the digitization andprocessing whichsignificantly affects the record. In thepresent paper a unified processing anddetermination of digitization andprocessing noise for the Greek strongmotion records is presented. Moreover,appropriate relations are proposed for thelower cut-off frequency with respect tothe epicentral distance and earthquakemagnitude for record filtering.     

留家水库坝基渗漏分析

留家水库是一座中型水库，多年来一直存在着渗漏问题，根据水库大坝的勘察资料，对水库渗漏问题进行了分析，并提出截渗措施。     

Quantifying channel development and sediment transfer following chute cutoff in a wandering gravel-bed river

Three-dimensional morphological adjustment in a chute cutoff (breach) alluvial channel is quantified using Digital Elevation Model (DEM) analysis for a ca. 0.7 km reach of the River Coquet, Northumberland, UK. Following cutoff in January 1999, channel and bar topography was surveyed using a Total Station on five occasions between February 1999 and December 2000. Analysis of planform change coupled with DEM differencing elucidates channel and barform development following cutoff, and enables quantification of sediment transfers associated with morphological adjustment within the reach. This exercise indicates an initial phase of bed scour, followed by a period characterised by extensive bank erosion and lateral channel migration where erosion (including bed scour) totalled some 15,000 m³ of sediment. The channel in the post-cutoff, disequilibrium state is highly sensitive to relatively low-magnitude floods, and provision of accommodation space by bank erosion encouraged extensive lateral bar development. Bar development was further facilitated by infilling of channels abandoned by repeated within-reach avulsion and large-scale aggradation of sediment lobes deposited by higher magnitude floods. Calculations indicate that at least 6600 m³ of sediment was deposited on emerging bars within the reach over the survey period, and >2300 m³ deposited within the channel. Sediment losses from the reach may have exceeded 6500 m³.     

黄河下游断流引起的环境问题及其防治措施

黄河下游断流是我国最大的环境问题之一。本文根据作者1983年以来对黄河及黄河三角洲的调查研究,从探讨断流原因入手,提出缓解和解决断流问题的多种综合措施。     

越过截渗墙渗流自由面的求解

对于越过截渗墙的剖面二维含自由面的渗流,应用保角变换方法求解,通过引入速度矢端平面和应用Schwarz-Christoffel变换,推导出了物理平面Z(x,y)和复势平面ξ(Φ,Ψ)的映射关系式.主要的待求参数和积分常量有4个,提出了相应的联立求解关系式.算例表明所提出的求解方法是可行的.     

五甲渡裁弯工程主要效益与负面的影响

五甲渡裁弯工程是显著提高曹娥江中、下游河道行洪能力的防洪工程,也是浙江省迄今最大的河道裁弯工程。在简述五甲渡裁弯工程与曹娥江中、下游水文及河床演变主要特性的基础上,分析了该裁弯工程显著的防洪效益、节省标准塘建设巨大投资费用等的经济效益,并对由于裁弯使河道长度缩短而造成咸水上朔距离有所增加等负面的影响进行了介绍。     

Hydraulic and geomorphic processes in an overbank flood along a meandering,gravel‐bed river: implications for chute formation

Hydraulic interactions between rivers and floodplains produce off‐channel chutes, the presence of which influences the routing of water and sediment and thus the planform evolution of meandering rivers. Detailed studies of the hydrologic exchanges between channels and floodplains are usually conducted in laboratory facilities, and studies documenting chute development are generally limited to qualitative observations. In this study, we use a reconstructed, gravel‐bedded, meandering river as a field laboratory for studying these mechanisms at a realistic scale. Using an integrated field and modeling approach, we quantified the flow exchanges between the river channel and its floodplain during an overbank flood, and identified locations where flow had the capacity to erode floodplain chutes. Hydraulic measurements and modeling indicated high rates of flow exchange between the channel and floodplain, with flow rapidly decelerating as water was decanted from the channel onto the floodplain due to the frictional drag provided by substrate and vegetation. Peak shear stresses were greatest downstream of the maxima in bend curvature, along the concave bank, where terrestrial LiDAR scans indicate initial floodplain chute formation. A second chute has developed across the convex bank of a meander bend, in a location where sediment accretion, point bar development and plant colonization have created divergent flow paths between the main channel and floodplain. In both cases, the off‐channel chutes are evolving slowly during infrequent floods due to the coarse nature of the floodplain, though rapid chute formation would be more likely in finer‐grained floodplains. The controls on chute formation at these locations include the flood magnitude, river curvature, floodplain gradient, erodibility of the floodplain sediment, and the flow resistance provided by riparian vegetation. Copyright © 2015 John Wiley & Sons, Ltd.     

Morphodynamics of the exit of a cutoff meander: experimental findings from field and laboratory studies

The morphological evolution of the entrances and exits of abandoned river channels governs their hydrological connectivity. The study focusses on flow and sediment dynamics in the exit of a cutoff meander where the downstream entrance is still connected to the main channel, but the upstream entrance is closed. Two similar field and laboratory cases were investigated using innovative velocimetry techniques (acoustic Doppler profiling, image analysis). Laboratory experiments were conducted with a mobile‐bed physical model of the Morava River (Slovakia). Field measurements were performed in the exit of the Port‐Galland cutoff meander, Ain River (France). Both cases yielded consistent and complementary results from which a generic scheme for flow patterns and morphological evolution was derived. A simple analogy with flows in rectangular side cavities was used to explain the recirculating flow patterns which developed in the exit. A decelerating inflow deposits bedload in the downstream part of the cavity, while the upstream part is eroded by an accelerating outflow, leading to the retreat of the upstream bank. In the field, strong secondary currents were observed, especially in the inflow, which may enhance the scouring of the downstream corner of the cavity. Also, fine sediment deposits constituted a silt layer in a transitional zone, located between the mouth of the abandoned channel and the oxbow‐lake within the cutoff meander. Attempts at morphological prediction should consider not only the flow and sediment conditions in the cavity, but also the dynamics of the main channel. Copyright © 2010 John Wiley & Sons, Ltd     

Long‐term river meandering as a part of chaotic dynamics? A contribution from mathematical modelling

In the present contribution we focus our attention on the possible signatures of a chaotic behaviour or a self‐organized criticality state triggered in river meandering dynamics by repeated occurrence of cutoff processes. The analysis is carried out examining, through some robust nonlinear methodologies inferred from time series analysis, both the spatial series of local curvatures and the time series of long‐term channel sinuosity. Temporal distribution of cutoff inter‐arrivals is also investigated. The analyzed data have been obtained by using a suitable physics‐based simulation model for river meandering able to reproduce reasonably the features of real rivers. The results are consistent and show that, at least from a modelling point of view, no evidence of chaotic determinism or self‐organized criticality is detectable in the investigated meandering dynamics. Copyright © 2010 John Wiley & Sons, Ltd.