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131.
利用江汉平原周老镇钻孔的岩心样品,分析研究了钻孔岩心沉积物10层砾石层中填充物的重矿物组分及分布特征。结果显示周老镇钻孔10个砾石层自下而上可以分为3个矿物段。对比3个阶段稳定重矿物、非稳定重矿物的变化特征:阶段Ⅰ、阶段Ⅱ,沉积物主要以近源物质为主,含有少量的远源物质;而阶段Ⅲ,沉积物主要以远源物质为主,含有少量的近源物质。结合周老镇钻孔岩性及钻孔砾石含量和江汉平原第四系岩相剖面特征,判断在阶段Ⅲ,深度112.30~109.05m(1.17~1.12MaB.P.)处,钻孔沉积环境发生了重大改变,江汉平原水系发生重要调整,长江三峡贯通形成。 相似文献
132.
在考虑工程地质条件和投资费用的前提下,介绍了素混凝土桩复合地基在侯马高层中的设计、施工工艺及处理效果,从而论证了素混凝土桩在侯马地区高层建筑地基处理中的可行性和实用性。 相似文献
133.
A grain-size record from Beijing region in Northern China: Late Quaternary paleoclimate oscillation in response to global change 总被引:1,自引:0,他引:1
Guifang Yang Zhiliang Ge Qing Dai Jie Cheng Gongming Yin Lihong Zan Jingwei Liu 《Frontiers of Earth Science》2009,3(2):164-170
Numerous samples taken from one core at the Beijing plain were utilized to characterize the paleoclimatic configuration of
the study area and its possible relation to global control since the last interglaciation. We presented here a detailed grain-size
record for the full length of Late Pleistocene, along with the optical simulated luminescence (OSL) dating. Our findings revealed
that Late Pleistocene of the study area started approximately at 110 ka B.P. represented by the thick sediments of 31 m in
Changping depression. Four sedimentary cycles were outlined in the core during Late Pleistocene, corresponding to marine isotope
stage (MIS) 5 to 2. Controlled by regional geology and global climatic setting, eight paleoclimatic periods were identified
simultaneously in the study area on the time scale of 104 year, with the warm and moist climate being found at 110 — 96, 92 — 76, 67 — 56, and 28 — 18 ka B.P.. The climatic instabilities
on a millennial scale in Late Pleistocene were characterized largely by the occurrence of 6 strong Heinrich events shown by
comparatively coarse groups. These variations correlate well with those documented in the GRIP Greenland and in the Northern
Atlantic Ocean, though more complex features may exist on the long time scale. 相似文献
134.
135.
Anis Chekirbane Maki Tsujimura Atsushi Kawachi Hiroko Isoda Jamila Tarhouni Abdallah Benalaya 《水文科学杂志》2013,58(5):1097-1110
Abstract The Wadi Al Ayn plain is a coastal system on the eastern coast of Cap Bon in northeastern Tunisia. The area is known for its intensive agriculture, which is based mainly on groundwater exploitation. The aim of this study is to identify the sources of groundwater salinization in the Wadi Al Ayn aquifer system and deduce the processes that drive the mineralization. Surface water and groundwater samples were taken and analysed for major ions and stable isotopes. The geochemical data were used to characterize and classify the water samples based on a variety of ion plots and diagrams. Stable isotopes are useful tools to help us understand recharge processes and to differentiate between salinity origins. The oilfield brines infiltrated from the sandy bed of Wadi Al Ayn comprise the main source of groundwater salinization in the central part of the plain, while seawater intrusion is mainly responsible for the increased salinity in the groundwater of the coastal part of the plain (at Daroufa). Citation Chekirbane, A., Tsujimura, M., Kawachi, A., Isoda, H., Tarhouni, J., and Benalaya, A., 2013. Hydrogeochemistry and groundwater salinization in an ephemeral coastal flood plain: Cap Bon, Tunisia. Hydrological Sciences Journal, 58 (5), 1097–1110. 相似文献
136.
Abstract Agricultural use and related water erosion may lead to significant changes in the sedimentological and hydrological characteristics of watersheds, and therefore negative consequences for rural development. This research aimed to put present-day soil erosion of the important Mejerda catchment into a historical context. The catchment of Wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impacts for thousands of years. We used historical texts and results from archaeological research that go back to 1000 BC, as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analysed together with information on the soils' production potential, the hydrographic network and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain by as much as 15 km2/century. However, soil productivity has decreased significantly. Moreover, due to in channel sedimentation and river choking, the number of flooding occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings should be considered for better water and soil management in the context of semi-arid areas. Editor Z.W. Kundzewicz Citation Jebari, S., Berndtsson, R., Lebdi, F., and Bahri, A., 2012. Historical aspects of soil erosion in the Mejerda catchment. Hydrological Sciences Journal, 57 (5), 901–912. 相似文献
137.
ABSTRACTThe point dilution test is a single-well technique for estimating horizontal flow velocity in the aquifer surrounding a well. The test is conducted by introducing a tracer into a well section and monitoring its decreasing concentration over time. When using a salt tracer, the method is easy and inexpensive. Traditionally, the horizontal Darcy velocity is calculated as a function of the rate of dilution and is based on the simple assumption that the decreasing tracer concentration is proportional both to the apparent velocity into the test section and to the Darcy velocity in the aquifer. In this article, an alternative approach to analyse the results of point dilution tests is proposed and verified using data acquired at a test site in the middle Venetian plain, northeast Italy. In this approach, the one-dimensional equilibrium advection–dispersion equation is inverted using the CXTFIT model to estimate the apparent velocity inside the test section. Analysis of the field data obtained by the two approaches shows good agreement between the methods and suggests that it is possible to use the equilibrium advection–dispersion equation to estimate apparent velocity over a wide range of velocities.
Editor D. Koutsoyiannis; Associate editor K. Heal 相似文献
138.
Abstract A two-dimensional (2D) hydrodynamic assessment of the Nile swamps in southern Sudan has been carried out using DHI MIKE 21 software based on a ground referenced and corrected Shuttle Radar Topography Mission (SRTM) digital elevation model. The model was set up and calibrated using available historical information as well as newly measured data. The results show the model capable of representing the hydraulic conditions in the swamps, allowing the assessment of different flow conditions and their effects on the swamp. The study has established water-level gradients, flow directions and velocities in the swamp, as well as on the seasonal flood plains, and describes the importance of evapotranspiration for losses in the system. Citation Petersen, G. & Fohrer, N. (2010) Two-dimensional numerical assessment of the hydrodynamics of the Nile swamps in southern Sudan. Hydrol. Sci. J. 55(1), 17–26. 相似文献
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140.
通过样品采集和室内分析,研究了成都平原区土壤中Cd高含量区的区域分布特征和第四纪分布的空间响应关联。在绵远河、石亭江流域冲积物中存在Cd含量高值区。在同一流域Ⅰ、Ⅱ级阶地→Ⅲ级阶地→Ⅳ级或Ⅴ级阶地冲积物中Cd含量逐渐降低。发育于龙门山的河流(绵远河、石亭江)沉积物Cd含量显著高于其他水系沉积物。Cd高含量分布区与不同级次的阶地相吻合的特征表明其控制因素显著,属于地质作用的产物。这一结论与多数研究者认为的人为因素引起的具有根本区别。 相似文献