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1.
冻结层上水的分布及工程影响研究现状与展望 总被引：1，自引：1，他引：0
作为一种多年冻土区的特殊水文地质现象,冻结层上水（或多年冻土层上水）的分布受局地因素的控制,且随活动层的季节性冻融而变化,影响地表水和地下水循环以及多年冻土环境中的水热平衡。多年冻土将冻结层上水限制在一个狭窄的空间内,在暖季冻结层上水侧向和竖向的渗流传热将加剧多年冻土的退化,也会对上覆工程构筑物的稳定运营造成极大威胁。目前关于冻结层上水的研究主要集中在分布特征、变化规律、流量计算、渗流模拟、水热耦合等方面。研究发现：在全球升温背景下,多年冻土退化速率加剧,随着冻土厚度变薄和融区出现,冻结层上水的流量及其与地下水的交换量均发生变化,除了影响局地水文特征外,还与工程病害密切相关,如坡脚积水、路基沉降以及路面裂缝等。以区域分布特征为出发点,对冻结层上水的研究现状进行了归纳和总结,并对其工程影响有关的渗流传热理论研究成果进行了梳理,对今后需要进行深入研究的方向进行了展望。这有助于全面理解冻结层上水在冻土区水文过程中的功能,为相关研究提供了进一步的理论参考。 相似文献
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气候变暖对黄河源区生态环境的影响 总被引：15，自引：2，他引：13
黄河源区位于多年冻土区,严酷寒冷的气候条件和冻土共同构建成一种特殊的冻结水环境,使地下水类型和水文地质结构均发生变化,与非冻土区有显著的差别,形成特殊的水文地质区。近几十年来,由于全球性气候温变暖,出现大面积冻土退化,以及过度放牧、鼠害加剧等原因,造成草场退化,沙漠化趋势日渐明显,严重地冲击着黄河河源区的水源养涵功能,导致黄河在源头段多次出现断流。通过水平衡计算,探讨了气候变暖对黄河源区多年冻土退化的影响,并阐述了冻结层上水环境变化和人类活动对生态环境的影响。 相似文献
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黄河源区冻土对植被的影响 总被引：8，自引：1，他引：7
黄河源区由于近年来气候变化的影响,打破了高寒植被与冻土环境之间稳定的适应性关系,由此引发了一系列生态环境退化的现象.在黄河源区多年野外工作的基础上,定量分析了冻土与植被之间的关系.研究表明:多年冻土埋深通过影响浅层土壤含水量影响植被生长的,多年冻土的埋深与浅层土壤含水率和植被的覆盖率具有良好的相关性规律.冻土埋深<2 m时,冻土埋深决定浅层土壤含水率,成为影响植被的生长主要因素;埋深>2 m时,冻结层上水水位低、补给量少,冻结层上水水量小,毛细上升高度不能达到植被根系分布的浅层土壤中,植被生长环境干旱化,多数植被生长受限制,这时只有少量根系发达的耐旱植被存活,覆盖率小,一般不超过35%.因此,2 m的多年冻土埋深为“生态冻土埋深”.近20 a来,黄河源区地温长期处于增温状态,多年冻土出现表层融化,形成深埋的或少冰的冻土等现象;部分地带完全融化消失,连续多年冻土变成不连续冻土或岛状冻土.多年冻土退化后,土壤含水量减少,导致植被物种更替、“黑土滩”等退化现象. 相似文献
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祁连山西段诸盆地水文地质条件 总被引：1，自引：0，他引：1
祁连山西段诸盆地地下水的形成与分布不仅取决于第四系厚度、孔隙、冻土等条件，更重要的还取决于山前平原与基岩的接触关系及其地质结构。盆地内地表水与地下水的相互转化，不仅使地下水的水质、水量具明显的水平分带性，而且也影响着主干河流流量的大小。在海拔３８００ｍ以上多年冻土区，地下水以冻结层上水和冻结层下水形式存在；在海拔３８００ｍ以下非多年冻土区，地下水主要以潜水形式存在，富水性中等或强。诸盆地地下水主要以ＨＣＯ３－Ｃａ－Ｍｇ型水为主，水质优良 相似文献
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为从整体上认识多年冻土活动层土壤水文过程季节变异特性,以黄河源区巴颜喀拉山北坡冻土剖面为例,结合大气降水、冻土土壤水分、冻土层上水的野外观测,采用HYDRUS-1D软件冻融模块进行模拟分析,分析冻融作用对活动层土壤水文过程的影响,研究结果表明:(1)冻土层上水位与土壤水热之间存在着相互影响、相互作用的关系,依据活动层土壤温度变化,基于冻融过程,多年冻土活动层土壤水分与冻土层上水位可划分为冻结稳定、快速融化、融化稳定和快速冻结4个阶段。(2)降雨入渗是坡面尺度下活动层土壤水文过程的主要驱动力,活动层冻融锋面是主要限制性因素,受冻融过程影响,冻结期降雨减少,土壤冻结,土壤储水能力下降,土壤水分下渗停止,坡面侧向流动减弱,土壤水分和冻土层上水位处于下降趋势;融化期降雨增多,土壤融化,土壤储水能力上升,土壤水分下渗强烈,坡面侧向流动增强,土壤水分和冻土层上水位处于上升趋势。(3)受坡面地形影响,上坡活动层厚度大于下坡,上坡冻融锋面变化较下坡平缓,上坡土壤水分和冻土层上水位的变化幅度相对下坡较为平缓,而上坡土壤水分相对下坡含量较低,下坡冻土层上水位相对稳定。 相似文献
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黄河源区高寒植被主要特征初探 总被引：3，自引：2，他引：1
位于青藏高原东北部多年冻土与季节冻土交错带的黄河源区高寒生态环境及其变化一直备受关注. 气候变暖、冻土退化条件下,为了解黄河源区不同冻土区植被状况,在源区布设了4个场地：查拉坪（CLP,源区南部连续低温多年冻土区）;扎陵湖南岸（ZLH,源区中南部岛状多年冻土区）;麻多乡（MDX,源区西部的不连续多年冻土区）;鄂陵湖北岸（ELH,源区中北部季节冻土区）. 结合植被调查和场地监测,分析了源区各冻土区植被的差异. 结果显示：总体上低温多年冻土区植被盖度、多样性指数高,表现为连续多年冻土区（查拉坪）>不连续多年冻土区（麻多乡）>季节冻土区（鄂陵湖北岸）,其中岛状多年冻土区（扎陵湖南岸）例外,该场地平均盖度最低,多样性指数介于查拉坪和麻多乡之间,局部植被退化较严重. 均匀度指数均表现为扎陵湖南岸最高,查拉坪次之. 地上生物量调查结果显示：查拉坪>麻多乡>扎陵湖南岸>鄂陵湖北岸,且鄂陵湖北岸出现指示植被退化的植物. 尽管黄河源区高寒植被研究为理解冻土退化条件下的生态环境变化提供了一些基础数据,评估气候变化和冻土退化的生态和水文效应需要更系统的调查和监测研究. 相似文献
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青藏铁路冻土区路桥过渡段沉降原因分析 总被引：4，自引：4，他引：0
青藏铁路开通近10 a以来,各类冻土工程稳定,保证了列车平稳安全的运行。然而,青藏铁路工程也不可避免出现了一些病害问题。现场调查资料表明,冻土区路桥过渡段下沉现象较为严重。通过冻土区路桥过渡段的沉降特点和工程地质条件综合分析,结果表明：地表水或冻结层上水水热侵蚀,引起人为多年冻土上限下降、高含冰量冻土层融化,致使路基发生强烈的融化下沉。建议这类工程病害应采取主动降温措施增强地基土的冻结能力,并加强防排水设施和改善地表水条件,消除水热侵蚀所产生的融化下沉。研究结果为青藏铁路路桥过渡段的稳定性和养护提供了科学依据。 相似文献
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青藏高原冻土及水热过程与寒区生态环境的关系 总被引：65，自引：36，他引：29
从青藏高原冻土及水热过程出发,利用青藏高原活动层监测数据,讨论了冻土水热过程与植被生长环境的关系,比较了季节冻土区与多年冻土区水热过程的差异及与植被的关系,同时讨论了不同草地生态冻融过程的变化.结果表明,冻土及水热过程与寒区生态环境有着密切的关系,冻土及水热过程不仅控制着地表状态的变化,影响着植被的发育程度,同时二者之间也存在着强烈的相互作用的关系.一旦地表条件被破坏,干扰了冻土水热过程与地表植被生长间的平衡关系,将引起生态环境的退化,出现荒漠化,甚至沙漠化. 相似文献
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东濮凹陷北部沙三中亚段广泛发育盐岩和烃源岩,这两个看似不能共存的物质却在这里互层共生。该时期研究区沉积特征为多盐韵律与多层烃源岩互层共生、连续沉积,单个盐韵律厚度从几米到十几米,烃源岩有机质丰度高、类型好。平面上,两者在湖盆沉积沉降中心共生;垂向上,高有机质丰度、好干酪根类型与高盐度地层具有较好的对应关系。因而成为恢复古气候和古环境的重要研究对象。通过岩石学、古生物学以及Sr/Ba、B/Ga、(V+Ni+Mn)、Fe/Mn、Sr/Cu、Mg/Ca、V/(V+Ni)、稀土元素含量和氯同位素等方法对凹陷北部沙三中亚段的沉积环境进行研究。结果表明,凹陷北部沙三中亚段为深水沉积的还原环境,古盐度较高,达到半咸水-咸水沉积;微量元素和孢粉化石特征表明研究区沙三中亚段为温暖潮湿的环境。 相似文献
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The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads 总被引：3，自引：1，他引：2
Clemente Irigaray Francisco Lamas Rachid El Hamdouni Tomás Fernández José Chacón 《Natural Hazards》2000,21(1):65-81
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning. 相似文献
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郯庐断裂南段研究进展与断裂性质讨论 总被引：13，自引：3，他引：13
据1：5万区域地质调查和专题研究资料，就郯庐断裂带是否南延与消失的原因，其与大别—苏鲁造山带交截形成的假位错效应，以及与中新生代沉积盆地形成演化的关系等作了新的阐述。在此基础上，讨论了郯庐断裂带是否为巨大的左行平移断层或转换断层。认为郯庐断裂带可能是在“古郯庐带”的基础上于早侏罗世重新活动、白垩纪强烈活动的地堑型枢纽断裂带。 相似文献
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Guboglo M. N. 《GeoJournal》1980,4(1):53-58
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen. 相似文献
16.
Dean S. Oliver 《Mathematical Geology》1998,30(7):911-933
In reservoir characterization, the covariance is often used to describe the spatial correlation and variation in rock properties or the uncertainty in rock properties. The inverse of the covariance, on the other hand, is seldom discussed in geostatistics. In this paper, I show that the inverse is required for simulation and estimation of Gaussian random fields, and that it can be identified with the differential operator in regularized inverse theory. Unfortunately, because the covariance matrix for parameters in reservoir models can be extremely large, calculation of the inverse can be a problem. In this paper, I discuss four methods of calculating the inverse of the covariance, two of which are analytical, and two of which are purely numerical. By taking advantage of the assumed stationarity of the covariance, none of the methods require inversion of the full covariance matrix. 相似文献
17.
某高速公路下伏煤矿采空区稳定性分析 总被引：10，自引：0，他引：10
在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上, 进行了稳定性数值模拟分析, 定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明: 该煤矿采空区的变形尚未完成, 对拟建的高速公路将产生很大的危害, 必须采取相应的工程治理措施。 相似文献
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Jiayu Rong Michael Melchin S. Henry Williams Tatyana N. Koren Jacques Verniers 《《幕》》2008,31(3):315-318
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs. 相似文献
19.
Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth
B. P. Kondratyev 《Astronomy Reports》2017,61(8):709-714
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″. 相似文献
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Important tendencies in development of the world mineral-resources sector at the beginning of the 21st century were an increase in production and consumption of mineral materials differentiated by types of metals and nonmetallic mineral raw materials, by countries and regions, as well as the concentration of the production of mineral raw materials in a small number of countries, and a reduction in industrial reserves of minerals in the world economy, even at the current stage of their extraction. These tendencies should be taken into account in working out a strategy for development of the Russian mineral raw-material base. 相似文献