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本文针对复合土工薄膜在电站防波堤作防渗和隔热体进行了研究,其防渗作用采用渗流与应力相结合的三维计算方法,给出了渗流场、应力应变等值线分布及热水渗流量,该渗流量在隔热计算中作为内部热源处理。结果表明,复合土工薄膜的防渗隔热效果是相当显著的。 相似文献
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本文通过青岛沿海地区四座施工围埝的工程实践,对土石挡水围埝的使用条件、设计原则、施工要点和主要的经验教训作了全面的的论述。并着重阐述了为保证围埝安全、控制埝内最高充水位的稳定计算;围埝的渗透计算;合拢与开口方法和施工中的质量控制等问题。以供交流和探讨。笔者认为,在低水头、透水层较薄的地基上,采用就地取材的土石挡永围埝,作为主体工程干施工的手段,是经济合理的。鉴于它涉计到的水文、地质和水、土力学中的问题较多;对防渗、防浪、防冲的技术要求较高,所以设计的实现有一定的难度。但实践证明,只要从设计和施工上认真做好围埝防渗层的“清基”、夯实和接头、沉降等技术处理工作;周密考虑围埝的合拢、开口措施;加强质量控制,就能收到良好的技术、经济效果。 相似文献
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一种新型筑堤结构：轻质硬壳堤坝 总被引：10，自引：1，他引：9
针对软弱地基存在的堤坝不均匀沉降、滑坡、位移、倒塌等问题,提出了一种新型的筑堤结构──轻质硬壳堤坝。该结构采用发泡塑料作为堤坝材料,或铺设于软基面上,或填充于易沉陷部位,或搅拌于土石方中;以高强度材料,制成堤坝外壳或堤坝某一部分的外壳,然后填入其他松散材料,使其产生减重、加筋、防渗、隔离、堆高的作用,以增强堤坝刚度,提高堤坝稳定性。这种新型堤坝结构具有较高的防洪、抗地震能力,以及缩短建筑工期,降低造价,废物利用等优点。 相似文献
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兴建河口海湾水库是国内外解决水资源不足的一项重要措施,其对水资源的充分利用具有极其重要的意义。本文依托沐官岛海湾水库工程,考虑海洋水文和地质条件因素,采用有限元分析软件ABAQUS建立了大型三维渗流和稳定性仿真有限元模型,开展多种潮位工况下拦海坝的孔隙水压、渗流速度和竖向沉降仿真计算,对沐官岛拦海坝渗流与稳定性进行分析。分析得出,在20年一遇潮位下,拦海坝的防渗性能良好,对海水与淡水起到阻隔作用。在50年、100年一遇潮位时,防渗墙内部产生渗流速度,这是由于水压差过大、渗流强度增加而产生的结果。拦海坝的不均匀沉降控制较好,不会发生坝体尤其是心墙的开裂。提出防渗墙加固措施,为坝基渗流预防、稳定性设计以及后续拦海坝建设与使用的安全性保证提供参考依据。 相似文献
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Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
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Sediments of the continental slope are commonly bioturbated by endo- and epibenthic organisms, particularly in and around submarine canyons and channels. This study reviews the architecture and depositional environments associated with canyons and channels on the continental slope, and assesses the key physical and chemical conditions encountered in and around these conduits. Hydrodynamic energy, concentration and quality of organic carbon, dissolved oxygen concentration and sedimentation rate are identified as key controls on the composition of benthic ecosystems in slope environments. Submarine canyons and channels focus a variety of turbid and clear-water currents, all of which serve to increase the concentration of oxygen, labile organic carbon and other nutrients, which tend to elevate the abundance and biodiversity in the seafloor sediments, compared with those of the surrounding slope. Ancient slope channel and canyon systems reflect some of the variation in ichnological assemblages that is seen in modern analogues, although processes of erosion and trace fossil preservation mean that the benthic environment is often incompletely preserved in the ancient record. By integrating current understanding of sedimentology, oceanography, biology and ichnology of slope environments it is possible to provide a first order summary of the inter-relationships between ichnology and depositional environments on the continental slope. The combination of these data has the potential to improve our understanding of changes in deep marine benthic ecosystems through geological time, and to further the use of ichnology in assessing hydrocarbon reservoir presence, quality and performance from bioturbated slope, canyon and channel-levee hydrocarbon reservoirs. 相似文献
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The state-of-the-art in modelling the marine ecosystem of the greater North Sea is reviewed, providing an overview especially about three-dimensional models that describe and predict how the marine ecosystem of the greater North Sea area functions and how concentrations and fluxes of biologically important elements vary in space and time, throughout the shelf and over years, in response to physical forcing. Articles with a strong concentration on modelling were selected from the available literature, and all articles around the existing “ecological modelling groups” dealing with the area of the North Sea were sorted in chronological order of their appearance in the literature. We found eleven of such groups and described their different modelling efforts. Selecting the seven three-dimensional models (NORWECOM, GHER, ECOHAM, ERSEM, ELISE, COHERENS and POL3dERSEM), we characterized the complexity of the models, by comparing the resolution in time and space, and the resolution of the trophic structure by discussing the number and kind of state variables and of the processes relating these state variables to each other.The review of biogeochemical/ecological modelling for the greater North Sea shows that important findings by model simulations have either confirmed existing knowledge derived from field work or have given new insight into the mechanisms of the functioning of the North Sea system: the temporal and spatial development and magnitude of primary production, its spreading from the coasts to the north-west over the open North Sea, its mechanisms of limitation, the functioning of the pelagic small food web and of the benthic web, the mechanisms of nutrient regeneration, the effects of riverine and atmospheric nutrient inputs causing eutrophication of coastal waters, the extent of eutrophication in the North Sea, and the budgets for nitrogen, phosphorus, and silicon. The three-dimensional ecological models of the greater North Sea have provided consistent distributions and dynamics of the lower trophic levels on their regional, annual and decadal scales which cannot be derived to this degree of coverage by observations.The state-of-the-art in validation for these models is presented in part 2 相似文献
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本研究采用解剖学及组织学方法对管角螺消化系统的结构进行了系统分析．结果表明,管角螺的消化系统由消化道和消化腺两大部分组成．消化道包含吻、食道、嗉囊、胃、肠、直肠及肛门;消化腺由唾液腺、肝及食道腺组成,其中肝为最大消化腺．唾液腺细胞分为粘液细胞和分泌细胞;食道腺细胞由排泄细胞和杯状细胞组成．在光学显微镜下,消化道的管壁由外向内依次为：外膜、肌层、粘膜下层和粘膜层4层;唾液腺、肝及食道腺均为复管状腺．管角螺的肝由肝被膜和许多盲管（肝小管）组成,肝管的组织结构与消化道基本相同,内有单层纤毛柱状上皮,可观察到肌层和管腔。 相似文献
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Bacterial and cyanobacterial diversities determined by T-RFLP analyses in the Jiaozhou Bay 总被引：2，自引：0，他引：2
1Introduction Bacteriaareactivelyinvolvedinthedecomposi tionanddegradationoforganicmatterandxenobiotic compound,biogeochemicaltransformationsandnu trientrecyclingoflife essentialelements.Owingto freshwaterrunoff,wastewaterdischargeandaquacul turalpractice… 相似文献
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目的：探讨人参醇提物及其沉淀对小鼠肠道菌群的影响。方法：利用环磷酰胺制备免疫低下小鼠模型,以人参水提物为对照,观察人参醇提物及其沉淀对小鼠肠道菌群的影响;肠道菌群数据采用Flash 1.2.11、Qiime 1.9.1、Mothur 1.30.2及PICRUSt 1.1.0等软件分析。结果：通过样本多样性指数分析,发现小鼠十二指肠、结肠、直肠所在部位肠道菌群结构差异具有统计学意义（P＜0.05或P＜0.01）。群落组成分析得知,小鼠肠道菌群差异较大的是Firmicutes(厚壁菌门),Bacteroides(拟杆菌门),Proteobacteria (变形菌门)与 Epsilonbacteraeota,Actinobacteria(放线菌门),Tenericutes(柔壁菌门)等。物种差异分析显示,免疫低下模型小鼠直肠部位的Epsilonbacteraeota数量显著增多(P=0.02),表明菌群失调;人参能调节肠道菌Epsilonbacteraeota失衡,其功效由大到小依次为人参水提物、醇提物及其沉淀。功能预测显示,肠道菌群结构改变,其对应的基因功能信息也改变,免疫低下模型小鼠直肠菌群结构与数量改变,引起RNA processing and modification, Chromatin structure and dynamics, Energy production and conversion 等方面基因改变。结论：免疫低下小鼠肠道菌群结构与功能改变,人参的不同提取物及其沉淀对小鼠肠道菌群有一定的影响。 相似文献
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Xiaojun Xie Wu Tang Gongcheng Zhang Zhigang Zhao Shuang Song Shixiang Liu Yibo Wang Jia Guo 《海洋学报(英文版)》2023,42(3):123-137
This study involved outcrop, drilling, seismic, gravity, and magnetic data to systematically document the geological records of the subduction process of Proto-South China Sea (PSCS) and establish its evolution model. The results indicate that a series of arc-shaped ophiolite belts and calcalkaline magmatic rocks are developed in northern Borneo, both of which have the characteristics of gradually changing younger from west to east, and are direct signs of subduction and collision of PSCS. At the same time, the subduction of PSCS led to the formation of three accretion zones from the south to the north in Borneo, the Kuching belt, Sibu belt, and Miri belt. The sedimentary formation of northern Borneo is characterized by a three-layer structure, with the oceanic basement at the bottom, overlying the deep-sea flysch deposits of the Rajang–Crocker group, and the molasse sedimentary sequence that is dominated by river-delta and shallow marine facies at the top, recording the whole subduction–collision–orogeny process of PSCS. Further, seismic reflection and tomography also confirmed the subduction and collision of PSCS. Based on the geological records of the subduction and collision of PSCS, combined with the comprehensive analysis of segmented expansion and key tectonic events in the South China Sea, we establish the “gradual” subduction-collision evolution model of PSCS. During the late Eocene to middle Miocene, the Zengmu, Nansha, and Liyue–Palawan blocks were separated by West Baram Line and Balabac Fault, which collided with the Borneo block and Kagayan Ridge successively from the west to the east, forming several foreland basin systems, and PSCS subducted and closed from the west to the east. The subduction and extinction of PSCS controlled the oil and gas distribution pattern of southern South China Sea (SSCS) mainly in three aspects. First, the “gradual” closure process of PSCS led to the continuous development of many large deltas in SSCS. Second, the deltas formed during the subduction–collision of PSCS controlled the development of source rocks in the basins of SSCS. Macroscopically, the distribution and scale of deltas controlled the distribution and scale of source rocks, forming two types of source rocks, namely, coal measures and terrestrial marine facies. Microscopically, the difference of terrestrial higher plants carried by the delta controlled the proportion of macerals of source rocks. Third, the difference of source rocks mainly controlled the distribution pattern of oil and gas in SSCS. Meanwhile, the difference in the scale of source rocks mainly controlled the difference in the amount of oil and gas discoveries, resulting in a huge amount of oil and gas discoveries in the basin of SSCS. Meanwhile, the difference of macerals of source rocks mainly controlled the difference of oil and gas generation, forming the oil and gas distribution pattern of “nearshore oil and far-shore gas”. 相似文献
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海洋锋面存在于特征明显不同的2种或多种水系或水团交界处,锋面区域形成的次生环流和辐聚作用可显著影响到海洋中的物质输运与生物生产,故受到海洋学家的广泛关注。研究发现,我国近海陆架存在14个永久性的准静止锋面（渤海海峡锋面、山东半岛沿岸锋面、苏北沿岸锋面、西韩湾锋面、京畿湾锋面、济州岛西锋面、长江环形浅滩锋面、闽浙沿岸锋面、黑潮锋面、台湾沿岸锋面、闽粤沿岸锋面、珠江口沿岸锋面、琼东锋面和北部湾锋面）,且部分海域观测到双锋面、穿刺锋面和锋面波等现象。它们与陆架环流及其他动力过程（如：涡旋、内波等）共同控制着我国边缘海的物质能量输运与交换以及生物生产力格局。近岸物质沿锋面、跨锋面输运与锋区的垂向输送过程对我国边缘海生物地球化学循环和生态过程存在显著季节性影响。冬季到春季,沿岸锋面松弛能够加强物质从近岸向陆架的输运,进而在空间上调制春季藻华暴发的时间与量级;夏季到秋季,我国边缘海存在显著的潮汐锋面系统,锋面的辐聚效应以及次级环流可显著提高锋面区域的营养盐浓度和改善光照水平,对浮游植物的生长聚集起到促进作用,故在富营养化的河口与沿岸海域,锋面区域容易成为赤潮或缺氧高发区。此外,锋面的物理屏障作用使得两侧水团保持相对独立的物理与化学特征,因而在我国边缘海生境区划和生物多样性梯度变化等方面扮演重要角色,这些研究对认识我国边缘海物质循环与生物生产的控制机制具有重要作用。未来仍需充分结合观测与卫星资料,运用多过程耦合的高分辨率模型,深入认识锋面的精细结构与动态变化,加强亚中尺度和小尺度过程及其生态效应的研究。 相似文献