溪洛渡电站软弱夹层剪切强度分析研究

岩体的力学强度参数,特别是软弱夹层剪切强度参数c、f的优化选取进行分析对比,对大型和特大型水电工程来说是非常必要的.本文采用多种力学参数选取方法讨论了溪洛渡水电站软弱夹层剪切强度参数c、f的取值问题,使剪切强度的选取有了更大的可比性,提高了c、f值的选取精度和可靠性.     

三种红层岩石常规三轴压缩下的强度与变形特性研究

利用MTS815Teststar程控伺服岩石力学试验系统研究了川东地区一红层边坡中的砂岩、粉砂岩和泥岩围压为03MPa的应力-应变全过程曲线,建立了峰值强度、峰值强度前弹性模量以及峰值强度后的弹性模量和围压的关系。将低围压下红层的全应力-应变曲线概化成5个阶段,分别为压密段、弹性段、屈服段、应变软化段和塑性流动阶段。试验结果得出,红层弹性模量随围压的增加而提高且变化明显,砂岩和粉砂岩在此围压内为脆性破坏,泥岩为塑性破坏的规律。     

渤海莱州湾晚第四纪底栖有孔虫分布特征及其地质意义

通过对渤海莱州湾GK138、GK111及GK95孔的255个沉积物样品中的有孔虫定量统计分析,共鉴定出底栖有孔虫15属32种。根据底栖有孔虫的丰度和分异度等分布特征和AMS14C和光释光（OSL）测年结果,揭示晚第四纪以来研究区共发育3套海相地层,分别是中更新世晚期的第三海相层、晚更新世的第二海相层和全新世的第一海相层,通过与全球海面变化曲线对比,发现其与MIS7、MIS5和MIS1阶段的高海面有良好的对应关系。样品的Q型聚类及主成分分析划分出3组代表不同沉积环境的有孔虫化石组合,第III化石组合带为中更新世晚期海侵的产物,为河口-滨岸浅海环境。第Ⅱ化石组合为晚更新世海侵的产物,为潮间带-潮下带沉积环境,第I化石组合带为潮上带-潮间带沉积环境。海相地层顶、底板高程和厚度的分析结果显示中更新世晚期至晚更新世期间发生过不同期次、不同强度的构造活动,而进入全新世以后构造活动相对减弱。     

中国北方晚中生代陆相盆地红-黑岩系耦合产出对砂岩型铀矿成矿环境的制约

为研究中国北方陆相盆地红层-黑色岩系对砂岩型铀成矿的制约,文章研究了国内外红-黑岩系与砂岩型铀矿赋存岩层的时空关系,筛选了10万余m岩心钻探资料,选择准噶尔、鄂尔多斯和松辽盆地这3个典型产铀盆地,通过编制盆地钻孔柱状图、典型地区连井剖面图及关键岩层的地球化学测试等方法,对红-黑岩系和砂岩型铀矿的赋存岩层进行了垂向、横向上综合分析与对比。研究发现:北方陆相盆地自西向东铀矿赋存地层的时代由中侏罗世过渡到晚白垩世;晚中生代至少存在6次大规模的富氧红层沉积事件:Ⅰ中侏罗世—晚侏罗世早期(BathonianOxfordian),Ⅱ早白垩世早中期(Berriasian-Barremian),Ⅲ早白垩世中期(Barremian),Ⅳ晚白垩世早期(Cenomanian),Ⅴ晚白垩世中期(Coniacian)和Ⅵ晚白垩世晚期(Campanian)。其中第Ⅰ、Ⅴ和Ⅵ期红层之下沉积了时代相近的黑色层,与之构成"红-黑岩系"的沉积结构,是北方砂岩型铀成矿的3个重要层位。典型盆地内地球化学表明,红层与黑色层的B、Sr和Cu元素含量及Fe~(2+)/Fe~(3+)、B/Ga、Sr/Cu和FeO/MnO比值具有明显的差异,结合黑色岩层中草莓状黄铁矿、碳屑、油斑和红层中碳酸盐岩的发育,认为红层为相对较强氧化环境,黑色层为相对较还原环境。连井剖面资料显示红层、黑色层与砂岩型铀矿空间关系密切,铀矿多产于红层与黑色层之间过渡带上,呈板状矿体赋存于灰色、绿灰色砂岩和细砂岩中。一般红层与黑色层垂向距离超过500 m不利于成矿。晚中生代陆相盆地内耦合产出的黑色岩系和红色岩系是古沉积环境由还原向氧化转变形成的垂向分带,前者为铀矿物质沉淀提供了"障",后者为表生流体溶解铀矿提供了"场"。文章初步提出了红-黑岩系垂向环境变化制约着北方陆相盆地砂岩型铀大规模成矿作用的新认识。这些认识不仅对砂岩型铀矿成矿环境、成矿规律及成矿模式研究具有重要意义,更对目前正在开展的砂岩型铀矿勘查工作具有实践指导意义。     

A comparison between different methods for determining grain distribution in coarse channel beds

The determination of grain size distribution in alluvial channels plays a crucial role in understanding fluvial dynamics and processes (e.g., hydraulic resistance, sediment transport and erosion, and habitat suitability). However, to determine an accurate distribution, tremendous field efforts are often required. Traditionally, the grain size distribution of channel beds have been obtained by manually counting a set of randomly selected stones (the“pebble count”). Based on this elementary principle, many authors have proposed different adaptations to overcome weaknesses and problems with the original method; with the development of digital technology, photographic methods have been developed in order to sig-nificantly reduce the time spent in the field. Two of these“image-assisted”methods include Automated Grain Sizing, AGS, and Manual Photo Sieving, MPS. In this study, AGS and MPS were applied under ideal laboratory conditions, to be used as reference, and in two field conditions with different degrees of difficulty in terms of visual determination of the grain size distribution; these included an artificial unlined channel and two natural mountainous streams. The results were compared with those obtained with the pebble-count method. In general, strong agreement between the methods was found when they were applied under favorable conditions (”the laboratory”), and the differences between the image-assisted and pebble count methods were similar to those found in previous studies. Despite being more time consuming, MPS was deemed preferable to AGS when conditions are not optimal;in these cases, the time spent on image elaboration significantly increased in the AGS method (approximately three-fold), but the estimation error of the median grain size decreased by approximately 37%. The use of image-assisted analysis has proven to be robust for characterizing sediment in watercourse beds and reducing fieldwork time, but because field conditions can significantly affect the accuracy of results, the method choice must be carefully considered.     

基于气候变化特征的红层划分对比——以东营凹陷南坡为例

首次利用气候变化特征,对由于缺少特征古生物化石资料而长期难以进行地层划分的东营凹陷南坡始新统沙河街组四段下亚段——孔店组一段的红层进行了有效划分。采用基于孢粉化石Ephedripites相对含量约束下的测井数据法恢复相对古气候变化,首先根据Ephedripites相对含量的变化确定气候变化拐点(最干旱点)的位置段,再根据能谱测井数据或常规测井数据计算出的连续粘土矿物组成确定气候拐点的具体点,即为层位界线。根据标准井测井数据建立的数学模型,可以对该井附近新钻探井的红层进行划分对比,其科学性、合理性已被之后的勘探成果所证实。该方法为缺少古生物化石数据的"哑地层"划分提供了一种新思路。     

再论华南志留系红层的时代

牙形刺P.eopennatus带的确立和P.celloni带、P.amorphognathoides带的细分,使华南Llandovery统的划分和对比发生了变化,以往归入P.celloni带的地层,极大多数都要归属到P.eopennatus带,层位变低。依据牙形刺生物地层的分析,溶溪组（下红层）的时代可能为埃隆期晚期,...     

淮南市朱集东矿井新生界松散层地下水开采保证程度评价

利用淮南市朱集东矿井新生界松散层供水水文地质勘探成果和抽水试验资料,查明了区内新生界松散层供水含水层的供水水文地质条件,认为第一含水层埋藏浅,易受污染,水量随季节变化大,不宜作为生活饮用水供水水源,第三含水层水质较差,亦不作为生活饮用水供水水源,确定了第二含水层为矿区主要供水层位。采用解析法对第二含水层的水量进行了计算,并设计了布井方案,计算了井群水量;水位预报结果表明,开采50a后,3#、4#井中的水位最大降深为35.229m,小于其顶板埋深,说明拟建井群布置是合适的。评价结果为矿井供水设计提供了依据。     

Early Devonian synorogenic alluvial-fan deposits of the Maccullochs Range,western New South Wales

The Early Devonian, Maccullochs Range beds (new) of the Winduck Interval largely comprise non-marine fine-grained sheet-flood-deposited sandstones which lie in the southeast sector of the Darling Basin Conjugate Fault System. Deposition of the >2.5 km-thick sequence occurred on the Wilcannia, Towers and Coolabah Bore alluvial fans, that were sourced largely from lightly indurated sandstone caps overlying a large basement high lying north of the Darling River Lineament, and also from west of Maccullochs Range (Coolabah Bore Fan). Four lithofacies are recognised. Lithofacies 1, massive sandstone, is proximal and was deposited from hyperconcentrated sheet floods. The more distal lithofacies 2 is partly massive, partly laminated and partly affected by soft sediment slumping during its deposition. It contains 1.3 – 3.5 m-thick sheet-flood successions that rarely show cross-bedding. Lithofacies 3 and 4 are minor: lithofacies 3, stream-flood deposited, comprises coarse-grained, pebbly sandstone and lithofacies 4, transient playa lake deposits that are locally intercalated with lithofacies 2. In lithofacies 2, thick massive fine-grained sandstone is commonly overlain by laminated sandstone that was deformed when soft. Incised channel deposits in lithofacies 2 deposits are rare and palaeosols were not discovered. Permanency of the positions of two of the alluvial fans, and by inference their feeder streams, remained unchanged for ～9 million years. The fans overlie probable floodplain deposits observed in a quarry in the easternmost part of the study area. Marine fossils are very minor in the range—the brachiopod Howellella jaqueti at one locality indicates an Early Devonian age for one of the brief marine incursions into what was normally an alluvial-fan environment. Very brief marine incursions elsewhere in the group are deduced from the presence of very rare fossil gastropods.