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徐兴华;尚岳全;唐小明;游省易;冯杭建 《中国地质灾害与防治学报》2013,24(4):6-15
山地丘陵地区,暴雨是一种灾害性天气,其持续性强降雨可诱发山体滑坡。对于因高等级公路建设而实施坡脚开挖的斜坡条件,其在连续性强降雨作用下的暂态渗流场及暂态安全稳定性的变化情况是值得探讨的问题。基于浙南山区某路堑斜坡实际工况,针对已经实施坡脚开挖的条件,采用数值模拟和极限平衡计算,研究斜坡在不同强降雨雨型作用下的饱和-非饱和暂态渗流场,并对其安全稳定性变化规律进行流固耦合分析。研究表明:在坡脚开挖的激发作用下,坡体达到失稳破坏的时间大大缩短;坡体暂态渗流场和强降雨雨型密切相关,强降雨持时越长,强降雨量越大,暂态渗流场向坡体表面扩散的趋势越明显,则滑体饱水面积比越大,基质吸力越小,坡体稳定系数的下降幅度也越大;坡体稳定系数的变化趋势与暂态渗流场的扩展变化情况密切相关,暂态渗流场越向坡体表面扩展则坡体稳定系数越低,可见在坡脚开挖和强降雨激发的综合作用下,斜坡极易失稳破坏。此规律性成果可为相应滑坡整治提供参考依据。 相似文献
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清江水布垭大岩淌滑坡位于水布垭水电站坝址区后部,正处于溢洪道泄洪时产生的雾化强暴雨中心地带,这种强雾化雨会显著影响滑坡体内的地下水分布,并给滑坡体的稳定带来不良后果。利用三维饱和非饱和稳定渗流有限元法对大岩淌滑坡在天然降雨以及高强度雾化降雨条件下的地下水流场分布进行了计算分析,后比较了滑体不同防、排渗措施的渗控效果。 相似文献
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降雨条件下酉阳大涵边坡滑动机制研究 总被引：1，自引：0，他引：1
以某厚堆积层滑坡为例,基于非饱和土力学理论,利用有限元方法,对雨水入渗条件下坡体的渗流及动态稳定性进行了计算和分析,研究了水分在坡体内的运移对边坡稳定性的时间效应。结果表明：边坡堆积体结构松散,土体强度差,边坡前缘坡降大,坡脚的开挖,为滑坡形成提供了便利条件;强降雨条件下使得坡脚附近首先发生变形失稳,牵引坡体后缘产生张拉裂。雨水沿坡面入渗,在坡体内形成渗流场,弱化岩土体参数,同时坡面形成饱和径流,使滑坡体前缘产生向下的渗透力,促使前缘坡体发生滑动,进而引发分级坡体产生滑移;强降雨初始阶段,滑坡体安全系数降低较快,很容易发生滑坡。该研究揭示了降雨入渗诱发厚堆积层边坡滑动机制,并以此建议采取以截、排、堵措施对边坡进行排水,同时设置嵌岩锚索抗滑桩及进行削坡清方措施对边坡进行综合治理,通过稳定性计算,效果良好。 相似文献
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高坝泄洪雾化雨入渗是影响其水垫塘边坡稳定的关键因素之一。为分析乌东德水电站水垫塘边坡受泄洪雾化雨影响程度,选取水垫塘边坡典型断面,建立二维非饱和、非稳定渗流计算模型,采用有限元法模拟泄洪雾化雨入渗过程,分析雾化雨入渗条件下坡体饱和区范围及压力水头的变化规律,同时对比研究坡面防护措施的效果。结果表明,对于坡体内部渗透性上强、下弱的部位,随着入渗补给量的持续增加,在阻水部位压力水头会逐渐升高;当坡面采取弱透水材料防护后,可显著减少坡面雾雨入渗量,从而显著降低雾化雨入渗对坡体渗流场的影响 相似文献
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基于Richards方程,对坝体的饱和-非饱和渗流场进行了模拟,再根据饱和-非饱和渗流场和非饱和土抗剪强度公式,对坝体的稳定性进行了分析。结果表明,水位骤降过程中坝体的安全系数通常呈现先缓慢增加后迅速减小的变化过程,分析坝体失稳时塑性区和位移场发现,水位下降的初期,坝体左侧坡体的安全系数要低于坝体右侧坡体,但水位下降到一定程度,右侧坡体的安全系数迅速减小,并先于左侧坡体失稳;采用有限元强度折减法用于多坡面边坡稳定分析时,只能获得最小安全系数的包络线;心墙具有隔水防渗的作用,对水位变化渗流具有阻尼作用。 相似文献
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滇西山前地带广泛分布着一层具有弱膨胀性的粉质粘土,在降雨条件下常诱发滑坡灾害,成为当地一种典型的滑坡灾害类型。从土体非饱和特性出发,通过土体吸力测试,提出了基质吸力-含水量土水特征关系,确定了饱和含水量在37%左右,残余含水量约3.5%,进气值约190 kPa;三轴力学试验取得了非饱和土强度参数,土体吸力内摩擦角为4.3°;建立了饱和—非饱和渗流数值模型,对不同雨强条件下的滑坡失稳过程、机制进行了模拟。模拟结果为:强降雨引起滑坡稳定性明显降低的时间效应为2 d左右,雨强16 mm/d以上,持续降雨3 d后滑坡失稳滑动,雨强6 mm/d以下的降雨对滑坡稳定性没有明显影响。为该类型滑坡灾害的防治提供了重要科学依据。 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
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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
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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
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Fouad N. Ibrahim Dr. 《GeoJournal》1988,17(1):133-141
Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators. 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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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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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