共查询到20条相似文献，搜索用时 15 毫秒
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红层泥质胶结物在干燥条件下会因含水率变化产生开裂,裂缝进一步发展贯通最终导致红层泥岩崩解破坏。目前对红层泥岩崩解机制的研究多为定性描述,缺乏定量分析方法。因此,定量研究红层泥质胶结物开裂的产生及扩展对深化红层泥岩崩解理论研究具有重要意义。基于线弹性断裂力学及非饱和土力学,建立了考虑含水率变化的红层泥质胶结物裂缝深度及间距计算公式,并对公式参数敏感性进行了分析。应用CT试验数据对PFC2D数值模型进行了校准,并基于干缩开裂数值试验结果,对裂缝深度及间距计算公式进行了对比验证。结果表明：提出的计算公式能较好地预测红层泥质胶结物的开裂深度及间距,裂缝深度随含水率减小呈先快速增加再缓慢增长的特点。研究成果有助于加深对红层泥岩崩解的量化理论分析,并为预测工程中红层泥岩的开裂程度提供参考。 相似文献
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音频大地电磁法在怀化方石坪村红层找水中的应用研究 总被引：1，自引：1，他引：0
文章采用音频大地电磁法,在怀化方石坪村红层进行找水应用研究。结果表明:（1）音频大地电磁法在该红层区是一种有效的物探方法,虽然该红层区电阻率值低,电性差异小,但音频大地电磁法是综合利用岩土层（体）的电性特征和磁性特征来分辨异常,电性差异对其影响相对较小;（2）数据处理的结果能很好地指示出异常特征和比较具体的异常位置,推断结果与钻井验证结果基本一致,最大涌水量为82.94 m3·d-1 ;（3）钻孔处视电阻率测深曲线ρs能有效地对地下电性结构进行评价,其K曲线将ρs 曲线中的微弱变化进行放大,突出异常,标示该红层区地下异常比较具体的深度和分层位置,分层结果与钻孔结果基本一致。 相似文献
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采用25 m分辨率的DEM并收集多年洪水位、潮位数据,以保证源数据的精度和可靠性.结合研究区地貌特征和水系分布,基于ArcGIS的空间分析工具采用种子蔓延法进行了有源淹没分析计算,得到淹没区范围和水深分布图.结果表明：淹没区主要分布在水库和河流下游的冲洪积平原和海积平原,淹没面积共318.08 km2,占全区陆域面积的18.6%.洪水淹没深度为0~7.6 m.以水库为种子点的淹没区域较大,淹没水深自种子点到海岸线逐渐增大;以河流为种子点的淹没区域呈带状分布,淹没水深自河流中线向两侧逐渐减小. 相似文献
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以西科1井第四系乐东组生物礁-碳酸盐岩地层为研究对象, 通过偏光显微镜观察、茜素红-S和铁氰化钾混合溶液染色、扫描电镜和矿物阴极发光性观察等分析方法研究了生物礁-碳酸盐岩的岩石学和成岩作用特征.西科1井生物礁-碳酸盐岩成岩作用包括较弱的压实作用、新生变形作用、微生物泥晶化作用、溶解作用、胶结作用.以典型胶结物岩相学产状为标志, 结合矿物阴极发光性特征识别出了大气水和海水成岩环境.其中, 大气水成岩环境以典型的新月形或悬垂形方解石胶结物为识别标志, 海水成岩环境以纤维状-针状文石为识别标志.成岩环境的垂向分布表现为: 0~27 m深度内为显著的大气水成岩环境; 27~42 m深度内以大气水成岩环境为主, 其次为海水成岩环境; 42~105 m深度内以大气水成岩环境为主, 海水成岩环境的影响弱; 105~172 m深度内大气水和海水成岩环境均出现; 172.00~214.89 m深度内为海水成岩环境. 相似文献
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F. Fabio Fussi Letizia Fumagalli Francesco Fava Biagio Di Mauro Cheik Hamidou Kane Magatte Niang Souleye Wade Barry Hamidou Roberto Colombo Tullia Bonomi 《Hydrogeology Journal》2017,25(8):2263-2279
A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population. 相似文献
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Three-Dimensional Gravity Model Applied to Underwater Navigation 总被引：1，自引：0，他引：1
YAN Lei FENG Hao DENG Zhongliang GAO Zhengbing Beijing Key Lab of Spatial Information Integration Its Applications Institute of RS GIS Peking University Beijing Beijing University of Posts Telecommunications Beijing 《《地质学报》英文版》2004,78(3):838-842
At present, new integrated navigation, which usesthe location function of reference gravity anomaly map to control the errors of the inertial navigation system (INS), has been developed in marine navigation. It is named the gravity-aided INS. Both the INS and real-time computation of gravity anomalies need a 3-D marine normal gravity model. Conventionally, a reduction method applied in geophysical survey is directiy introduced to observed data processing. This reduction does not separate anomaly from normal gravity in the observed data, so errors cannot be avoided. The 3-D marine normal gravity model was derived from the J2 gravity model, and is suitable for the region whose depth is less than 1000 m. 相似文献
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选取位于中国北方干旱区的湖泊乌梁素海为研究区,基于2002-2004年的LandsatTM数据以及同期实测水深数据,根据水深遥感原理,通过1次,2次,3次实测水深数据与遥感影像反射率及其组合之间的相关关系,选取五变量,三变量,二变量及一变量的非对数及对数模型进行湖泊水深估值,继而通过误差分析及模型对比,最终确定出3次实测数据五变量非对数模型作为乌梁素海的最优估值模型。该模型利用多光谱组合确定水深的估值模式,克服了单光谱信息难以综合反映沉水植物、芦苇、水色及底质空间变化的困难,符合干旱区浅水湖泊的特性,结果可为干旱区其它浅水湖泊水深反演提供新的思路和参考。 相似文献
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南海北部陆坡深水沉积体系研究 总被引：25，自引：2，他引：23
陆源碎屑物质是深水地质研究的重要内容,在全球“从源到汇”研究计划中占有重要地位。海底峡谷-水道搬运沉积体系和块体搬运沉积体系（海底滑坡）是大陆坡最重要的两种搬运沉积过程。根据高分辨率2D、3D多道反射地震资料、多波束测深法、旁扫声纳、重力与活塞取样等资料研究发现,在南海北部陆坡地层中,广泛发育大型深水块体搬运体系和相应深水水道沉积体系。针对白云凹陷和琼东南盆地深水陆坡区的实例研究,揭示了典型深水块体搬运的平面形态、内部结构和变形过程,进而深入认识这一地质体的形成演化过程。采用2D/3D地震资料和多种数值模拟新方法发现了第四系深水高弯曲水道及其沉积相特征、上新世琼东南盆地中央水道及中新世古珠江深水水道体系。深水沉积体系对研究我国深水油气资源的成因机理和分布规律,以及深水工程的地质灾害预测和防护具有十分重要的意义。 相似文献
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Hassan Mohamed AbdelazimNegm Mahmoud Salah Kazuo Nadaoka Mohamed Zahran 《Arabian Journal of Geosciences》2017,10(2):42
Bathymetric information for shallow coastal/lake areas is essential for hydrological engineering applications such as sedimentary processes and coastal studies. Remotely sensed imagery is considered a time-effective, low-cost, and wide-coverage solution for bathymetric measurements. This study assesses the performance of three proposed empirical models for bathymetry calculations in three different areas: Alexandria port, Egypt, as an example of a low-turbidity deep water area with silt-sand bottom cover and a depth range of 10.5 m; the Lake Nubia entrance zone, Sudan, which is a highly turbid, unstable, clay bottom area with water depths to 6 m; and Shiraho, Ishigaki Island, Japan, a coral reef area with varied depths ranging up to 14 m. The proposed models are the ensemble regression tree-fitting algorithm using bagging (BAG), ensemble regression tree-fitting algorithm of least squares boosting (LSB), and support vector regression algorithm (SVR). Data from Landsat 8 and Spot 6 satellite images were used to assess the performance of the proposed models. The three models were used to obtain bathymetric maps using the reflectance of green, red, blue/red, and green/red band ratios. The results were compared with corresponding results yielded by two conventional empirical methods, the neural network (NN) and the Lyzenga generalised linear model (GLM). Compared with echosounder data, BAG, LSB, and SVR results demonstrate higher accuracy ranges from 0.04 to 0.35 m more than Lyzenga GLM. The BAG algorithm, producing the most accurate results, proved to be the preferable algorithm for bathymetry calculation. 相似文献
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海洋水深信息对研究珊瑚礁海域资源与环境具有重要作用。南海珊瑚礁海域测深数据受多种条件限制施测困难,在时间与空间方面数量非常有限。文章针对南海岛礁海域以I类水体为主导的海水光学特性,以南沙群岛库归沙洲海域为例,使用Sentinel-2多光谱卫星遥感影像和同期过境的MODIS卫星数据,构建底质光谱,采用半分析半经验模型计算海水表面遥感反射率与海水叶绿素浓度,通过对数比值模型进行该地区光学浅水海域遥感水深反演分析,并进一步通过多时相反演水深融合提升精度。经与多波束实测水深数据验证,研究区域反演水深总体均方根误差和平均相对误差分别为2.68 m 和9.99%。该方法通过叶绿素浓度推演部分海水光学特性,可以从多光谱卫星影像中快速获取南海岛礁光学浅水海域初步水深信息,供相关海洋领域分析与应用。 相似文献
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Khamis Naba Sayl Nur Shazwani Muhammad Ahmed El-Shafie 《Environmental Earth Sciences》2017,76(10):368
The major limitation in planning water harvesting is the lack of knowledge in the estimation of surface area and storage volume at any depth of dam reservoir. The area–volume–elevation (AVE) curve of a reservoir plays a key role in estimating the most suitable depth, optimum surface area and highest capacity of reservoir storage. The existing methods to estimate the AVE curve are costly and time-consuming and require laborious work. This study attempts to develop a method to optimize the AVE curve for earth dams, using the digital elevation model generated by the Shuttle Radar Topography Mission (SRTM) data, and integrate it with the geographic information system (GIS), known as the GIS–SRTM. The proposed method was tested using field data in the Western Desert of Iraq, which is an arid environment. Three constructed small earth dams were selected for this study. The AVE curves were extracted for Horan 2 (H2), Al-gara 2 (G2) and Al-gara 4 (G4) earth dams. Comprehensive analyses have been carried out to evaluate the performance of the AVE curves using the proposed GIS–SRTM method and the field data. From the comparison, the proposed GIS–SRTM method was able to produce reliable AVE curves with a relative error less than 20%. Additionally, the proposed method was less time-consuming and the AVE curves can be visualized immediately. The proposed GIS–SRTM method is relatively supportive in analyzing spatial data to select the optimal site for rainwater harvesting and prevent excessive evaporation losses. 相似文献
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传统Green-Ampt入渗模型由于假设过于简化而限制了计算精度,针对这一问题,在分层假设的基础上对模型进行了改进:将均质入渗土壤分为饱和层、过渡层和干土层,采用Richards模型分析了不同入渗条件下各层的厚度以及各层内含水率和导水率的变化规律,结果表明,入渗条件一定时,过渡层占湿润层(包括饱和层和过渡层)比例会随湿润层厚度的增加线性减小,积水深度和土壤初始含水率分别会影响这一线性关系的纵轴截距和斜率,而土壤饱和导水率则对其没有明显影响;过渡层内土壤含水率分布为椭圆形曲线,而导水率随深度增加线性减小。在此基础上,通过引入湿润层的等效导水率并相应给出锋面吸力的计算方法,对传统Green-Ampt模型进行了改进。结果显示,改进后模型计算精度显著提高。 相似文献
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Anne M. Graese David N. Baynard James C. Hower John C. Ferm Yuejin Liu 《International Journal of Coal Geology》1992,21(4)
The stratigraphic and regional variation of petrographic and chemical properties within the coals of the Upper Carboniferous Tradewater Formation and surrounding rocks in the Western Kentucky coal field were analyzed with the intent of constructing a depositional model for the occurrence of these low sulfur coals. Cores were megascopically described, and coal samples were analyzed for maceral, ash, and sulfur contents. These data were then analyzed to determine regional variation within the study area, as well as vertical variation within single coal columns.Sedimentological data from core logs indicate that the majority of the Tradewater rocks consist of irregularly distributed, coarsening-upward, fine-grained detrital material that was deposited in shallow bodies of water. Fossiliferous shales and limestones indicate a marine influence. Less common coarse-grained, fining-upward sequences appear to represent deposits of meandering or braided channels.Like the detrital rocks, the coal seams are irregularly distributed and exhibit substantial variation in petrographic and chemical properties which reflect changes in the Eh and pH of the coal swamp waters. These individual swamps were relatively limited in extent and probably occupied a low-lying coastal area. The relatively high vitrinite content of most of the coals suggests a reasonable degree of preservation of decaying plant materials. The study of benched samples from surface mines suggests a distinct dichotomy between swamps that were in more or less continuous contact with sulfate-rich marine or brackish water and those in which peat accumulated in a dominantly fresh-water setting. Most of the latter show a pattern of upward increasing sulfur content and decreasing vitrinite content, indicating increasing influences of oxygenated water that would encourage microbial action and which would degrade the peat and increase the tendency for sulfide precipitation. The high sulfur coals do not display this variability. The high rates of lateral variability encountered in the data suggest that future study should concentrate on smaller areas where variation can be completely documented. 相似文献
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参照青海省柴达木盆地北缘寒武纪和奥陶纪地层相关文献资料,通过野外地质调查和系统样品分析结果,在柴北缘寒武纪—奥陶纪地层中梳理和识别出了19层海相红层。其中,寒武纪地层中识别出了12层海相红层,奥陶纪地层中识别出了7层海相红层。除奥陶纪石灰沟组海相红层(QORB3,QORB4,QORB5及QORB6)为深水大洋红层外,其余15层海相红层均属浅水—半深水陆棚红层。依据海相红层及其上下层位所含化石,本文初步论述了各海相红层的大致时代,并与我国主要块体的同期海相红层进行对比。上述研究对进一步开展全国乃至全球寒武纪、奥陶纪海相红层分布及对比提供了基础数据和资料。此外,通过国内同期红层的对比,本文还讨论了河北唐山寒武纪海相红层的分布及中国南方中奥陶世大坪期—达瑞威尔期早期海相红层广布事件。 相似文献
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鄂尔多斯盆地准格尔东部煤田石炭?二叠系 6 煤层为巨厚煤层,煤层底板面临奥陶纪灰岩含水层威胁尤为突出,由于采动效应的影响会形成底板采动破坏带,可能会形成新的导水通道引起突水灾害。针对底板采动破坏带测试问题,提出采用动源动接收的孔中瞬变电磁法,在采前和采后工作面底板钻孔中获取岩层电阻率特征数据的方法。首先通过数值模拟对比孔中瞬变电磁法在完整和二层岩层模型中呈现的电阻率差异性,验证该方法对二层岩层模型具有较好分辨率;然后在准格尔煤田酸刺沟煤矿6119巨厚煤层综放工作面进行试验,通过探查底板电性差异层得到底板破坏深度,经过验证结果准确可靠。研究表明:孔中瞬变电磁法探测技术与测试钻孔相结合,通过对比采前与采后结果获取了较为准确底板破坏深度,对类似条件下的工作面破坏深度测试提供了一种新的方法。 相似文献
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The early Mesoproterozoic Rohtas Limestone in the Son valley area of central India represents an overall shallowing-upward
carbonate succession. Detailed facies analysis of the limestone reveals outer- to inner-shelf deposition in an open marine
setting. Wave-ripples, hummocky cross stratifications and edgewise conglomerates argue against a deep marine depositional
model for the Rohtas Limestone proposed earlier. Stable isotope analysis of the limestone shows that δ13C and δ18O values are compatible with the early Mesoproterozoic open seawater composition. The ribbon limestone facies in the Rohtas
Limestone is characterized by micritic beds, each decoupled in a lower band enriched and an upper band depleted in dissolution
seams. Band-wise isotopic analysis reveals systematic short-term variations. Comparative enrichment of the heavier isotopes
in the upper bands is attributed to early cementation from sea water and water derived from the lower band undergoing dissolution
because of lowering of pH at depth. The short-term positive shifts in isotopic compositions in almost every upward gradational
transition from a seamed band to a non-seamed band support the contention that dissolution seams here are of early diagenetic
origin, although their formation was accentuated under overburden pressure. 相似文献