Factors affecting performance of permeable groins in channel bank erosion control

The factors affecting the performance of permeable groins are investigated by an analytical approach supplemented with field observation. These factors are broadly divided into three classes: (1) the properties of the soil where the groin is embedded; (2) the flow characteristics of the river channel that are imposed on the groin; and (3) the makeup of the groins. Factors relating to the properties of the soil and flow are then combined into an expression for the factor of safety against failure by overturning. This enables a deterministic sensitivity technique involving partial differentiation of the factor of safety with respect to each contributory factor to be applied. The results obtained show that depth of the groin is the most critical factor that determines groin stability. The depth is followed by flow velocity and discharge, unit weight of water, unit weight of soil, and cohesion. This order of importance agrees with the analysis of observed groin performance in a pilot project at Kaiama in the Niger delta.     

中国大河三角洲发育的共同性与差异性

本文主要根据作者对国内外三角洲调查分析资料，论证了中国沿海大河三角洲的沉积旋回、基底构造、形成年代、沉积层序和沉积特点的可比性，但其形态类型、沉积相组合和发育程度颇有差别，体现了世界全新世各大三角洲发育的共同性与差异性。     

渤海湾淤泥质海岸潮汐汊道的发育过程

本文以黄河三角洲沿岸为例，论述淤泥质海岸上潮汐汊道的发育过程。研究表明，淤泥质海岸潮汐汊道与废弃河口深化化有密切关系。它的外侧海岸是在高海面时形成并被现代动力过程所切割的贝壳砂堤或砂堤。     

Saline fresh water interface structure in Mahanadi delta region, Orissa, India

 Saline/fresh water interface structure is one of the most important and basic hydrogeological parameter that needs to be estimated for studies related to coastal zone management, well-field design and understanding saline water intrusion mechanism/processes. The success and stability of a groundwater structure in a coastal region depend upon an accurate estimate of interface structure between saline and fresh water zones, aquifer-aquiclude boundaries and their lateral continuities and the interstitial water qualities of aquifers. Self-potential and resistivity logs provide a reasonably good basis for such estimates and for sustainable development of fresh groundwater resources. The interface depth structure for the Mahanadi delta region, as obtained and interpreted through self-potential and resistivity logs, provides a fairly clear picture of the regional extensions and boundaries of aquifers, aquicludes and interstitial water quality patterns. Aquifers in the northern sector of the basin and within the framework of Birupa and Mahanadi are characterized by an interface depth range that varies between 40 and 280 m below ground level (bgl) with brackish water on the top underlain by freshwater aquifers. The aquifers in the southern sector within the framework of Khatjori/Devi and Koyakhai/Daya/Kushbhadra/Bhargavi are characterized by an interface depth range that varies from 10 to 120 m with freshwater aquifers near the surface underlain by saline, brackish water aquifers. The inversion of these major fluid systems appears to have taken place over a narrow zone between Mahanadi and Khatjori tributaries, possibly over a wide subsurface ridge with separate basin characteristics. Received: 29 November 1999 · Accepted: 2 May 2000     

潮控与河控下三角洲平原成煤的岩石学和地球化学特征

从显微煤岩组成特征、不同显微组分中有机硫的含量、伴生元素组成、硫同位素的分布特征等方面对内蒙古乌达矿区潮控下三角洲平原形成的高硫煤 9煤层和河控下三角洲平原形成的低硫煤 13煤层进行了研究。结果表明 ,潮控下三角洲平原形成的煤层较之河控下三角洲平原形成的煤层具有较高的镜质组含量 ;伴生元素中 Na、K、V、Mg等含量偏高 ,而稀土元素含量较低 ,稀土元素的含量与煤中的粘土矿物含量成正比 ;黄铁矿和有机硫同位素都比较轻 ,表明高硫煤中硫的来源主要是海水中细菌还原的硫酸盐。     

新疆尼勒克地区下侏罗统三工河组辫状河三角洲沉积

新疆伊宁盆地早侏罗世为一内陆坳陷盆地 ,沉积了一套冲积—湖泊环境下的碎屑岩沉积体 ,其中三工河期盆地周缘广泛发育辫状河进积到湖泊中而形成的辫状河三角洲。三角洲三层结构清楚 ,由下而上出现前辫状河三角洲亚相、辫状河三角洲前缘亚相及辫状河三角洲平原亚相 ,呈明显的进积层序。辫状河三角洲特征显著 ,明显有别于其它类型的三角洲 ,可见到九种特征各异的微相。辫状河三角洲的主体是由含砾砂岩及中、粗粒砂岩组成的辫状河道砂坝及水下分流砂坝 ,单一砂坝呈下粗上细的透镜状 ,透镜体最大厚度在 0 .5～ 3m不等。垂向上许多砂坝透镜体相互叠置而成巨厚砂体。三角洲中交错层理丰富 ,其中尤以水道砂坝侧向迁移加积而形成的侧积交错层异常发育为标志。     

汉江三角洲结构与时空过程

汉江三角洲开发较早,生产水平较高,人文地貌景观十分触目,自然本色大为改观。本文通过汉江三角洲系统空间结构的形成和时空过程分析,揭示其天然结构自组织的趋向性,指出其流通系统（河湖布局结构）自动调整与人工调整之间存在着某些方向性的差异。为建立汉江三角洲表层动态平衡系统提供导向性信息,为三角洲区域协调发展提供科学依据。     

用泥岩压实法推算东营期剥蚀厚度

本文依据泥岩压实的物理化学过程,建立了超深井泥岩压实趋势模型;提出推算东营期剥蚀厚度应在正常的机械压实段,以压实泥岩时差为下限,向上作统计趋势线;并讨论了压实斜率和地表传播时差取值问题。     

DEPOSITIONAL CHARACTER AND SHORELINE CHANGES OF THE NANDUJIANG DELTA,HAINAN ISLAND,CHINA

.Introducti0nTheNandujianghiver,withalengthOf3llkIn,adrainageareaof684lkm2andanaverageannunldischargOf60xl09m',isthelargstriveronHainanIsland.IttransportsanaveragannualsedimentloadOfO.68xlO6tonsnorthwdintoQangrhouStrait,wherethetidalrangnisca1.Om,andwavesandlongrhorecurrentsarerelativelystrong.TheNandujiangdeltacoves20OkIn2.ThedePOsitionalSystemOfthedeltaconsistsofrivermouthbars,distribotarymouthbars,marshdepositsfOrmedinbaysandlagoons,sandridges,sandsPitsanddunes.ThedistributionPatt…     

扇三角洲序列样式及其控制因素：以伊通地堑为例

扇三角洲沉积是伊通地堑主要沉积体系，地堑内发育水下水道型和水下水道一河口坝复合型扇三角洲，完整的扇三角洲序包括进积，加积和退积３个阶段，在不同的构造沉降和沉积物供给条件下，形成了３种各具特色的扇三角洲序列样式，即缓慢沉降和低速沉积物供给型，快速沉降和低速沉积物供给型，快速沉降和高速沉积物供给型。