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自升式钻井船桩靴的插拔过程将会对临近井口平台的桩靴基础产生不利影响。开展了室内模型试验研究,将试验结果与理论分析结果相结合,得到了桩靴插拔的影响范围及影响范围内土体强度的变化规律,并推导了桩靴插拔影响区内临近桩靴承载力的计算方法,与模型试验结果进行了对比验证。研究表明,桩靴插拔后砂土相对密实度降低,其降低程度随距桩靴距离的增加而逐渐减小,影响范围约为1倍桩靴直径。受桩靴插拔影响,临近桩靴的承载力下降,降低比例随两桩靴相对间距的增大而减小,随桩靴相对插深的增加而增加。当两桩靴相对间距大于2倍插拔桩靴直径时,可认为桩靴插拔对临近桩靴基础承载力无影响。 相似文献
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自升式平台在遗留桩坑附近就位时,桩靴的滑移风险对于平台结构安全具有重大威胁。基于耦合欧拉?拉格朗日方法,建立了遗留桩坑附近插桩过程的有限元模型,对加载速率和网格密度等进行参数分析,确定了合理的模型参数,并进一步研究了相关参数的影响规律。结果表明,滑移载荷产生的主要原因在于桩靴贯入过程中土体破坏面的不对称;峰值滑移载荷随桩坑坡度、深度和直径的增大而增大;减小桩靴底面坡度可以有效减小桩靴上的滑移载荷。研究揭示了桩坑和桩靴几何参数对滑移载荷的影响机制及其规律,对于深刻认识“踩脚印”问题和有效指导桩坑附近二次就位作业具有科学意义。 相似文献
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桩靴接触应力是影响插桩深度的主要因素之一,桩靴的锥尖型式可能会影响接触应力的大小及分布。以江苏省启东市某插桩试验项目为例,针对不同的桩靴端部型式基于桩靴接触应力现场实测数据,分别采用国内外规范方法及数值计算方法对插桩深度开展预测分析,揭示桩靴端部型式对插桩深度的影响规律。结果表明：在插桩过程中不同锥端类型桩靴的接触应力呈现出中央大周边小的分布特征,表明现场桩靴为柔性结构类型;采用不考虑桩靴端部形状的规范方法进行桩靴插深预测,得出的预测结果同现场实测结果基本吻合;采用小变形有限元数值方法进行插深预测也可以得出令人满意的结果,研究结果可为类似工程实践提供参考。 相似文献
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介绍一种在嘉兴地区应用较为成熟的桩型——平底大头桩，它是一种采用预制扩大头的特殊型式的沉管灌注桩，能够充分利用浅部持力层的承载性能，提高单桩承载力，既能满足上部荷载及变形要求，又能达到节省造价的目的。 相似文献
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为考虑钻井船插桩对邻近平台群桩相互作用的影响,以海洋平台群桩设计中使用的修正Poulos法为基础,提出了一种考虑桩靴贯入影响的群桩分析方法。该法基于非线性地基梁模型确定桩靴贯入土层时单桩桩头位移;依据桩同时承受桩头荷载与土体位移时对应的地基反力系数确定土层的弹性模量,进而在Poulos群桩相互作用分析理论框架内,分析桩靴贯入对群桩相互作用的影响,确定桩靴贯入过程中由于群桩相互作用导致的附加桩头位移及相应的群桩桩头位移;依据群桩桩头位移,确定考虑桩靴贯入影响的群桩p-y曲线Y因子及相应的p-y关系。为了说明分析方法的可行性,进行了桩靴贯入砂土时对邻近单桩和群桩相互作用影响的离心模型试验,方法预测与试验结果基本一致,从而验证了方法的合理性。对于文中的工况,桩靴贯入没有导致群桩p-y关系进一步弱化,此时采用桩靴贯入前的群桩p-y关系确定考虑桩靴贯入影响的群桩响应,得到的结果偏安全。 相似文献
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本文叙述砂桩施工的五种方法,1、回转钻进法,使用轻便岩心钻机钻孔,提钻后向孔内灌砂密实。2、水力冲击法,利用水力喷射和冲击相结合成孔,孔内灌砂密实或放入袋装砂。3、全套管静正法,由专用砂桩机把底端带桩靴的套管压到设计深度,管内放入袋装砂,然后拔管。4、锤击或振动沉管法,用锤击或振动沉桩机把底端带柱靴的柱管沉入土层至设计深度,然后从桩管上端的加料斗灌砂,边拔管边锤击或振动密实砂桩。5、法兰基钴机法,先在桩管中灌入足够高度的砂,后用内落锤密实砂子形成砂塞,把桩管沉入设计深度,在拔管中从加料斗加入砂量。砂桩施工质量的控制参数包括桩的深度、桩的定位、砂子粒度、含泥量和灌砂量。在采用袋装砂时,必须严格控制袋料质量和加工规格。 相似文献
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自升式钻井平台在东海的作业量随着西湖地区勘探开发的不断发展而在增加。因受台风影响及在同一地点多次作业的原因,自升式钻井平台不可避免地会在上一次作业位置附近重复作业,引起桩靴滑移现象,可能造成就位后悬臂梁覆盖能力下降,无法满足钻井作业需求,甚至影响平台结构安全,造成工程事故,大大增加了作业风险。本文以H9自升式钻井平台桩靴为例,分析了桩靴部分重合工况下的受力特点,研究了海底土体破坏形式,提出了不同类型土质条件下的桩靴水平力计算模型,并利用滑移线有限差分法近似计算桩靴极限载荷。对H9平台在现场重复就位时采取的措施进行了分析,并根据海上作业要求提出了一系列安全控制措施,为安全高效地实现平台重复就位提供了参考。 相似文献
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钻井船拔桩对筒基平台稳定性影响的敏感分析 总被引：1，自引：0，他引：1
利用通用的有限元程序ANSYS软件,以渤海8号自升式钻井船和歧口17-2筒型基础平台为对象,采用三维8节点的块体等参元和Drucker-Prager模型,分3步模拟了钻井船桩靴的拔出过程,并在钻井船桩靴与筒型基础筒体之间距离一定的情况下,考虑土性参数的敏感性,就桩靴在拔出过程中对筒型基础平台地基强度以及筒体变位的影响进行了三维有限元分析。分析结果表明,随着筒土相对刚度的减小以及内摩擦角、黏聚力的增大,钻井船拔桩对平台地基承载力的影响逐渐减小;就土性参数中弹性模量、内摩擦角以及黏聚力对筒边地基土体承载力的影响而言,弹性模量和内摩擦角的影响规律更为明显。 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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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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Chronological analyses of correlations between certain global repeating events (mass extinctions of marine organisms, meteorite impacts, and flashes in the frequency of geomagnetic reversals) during the Phanerozoic Eon and the motion of the solar system in the Galaxy are presented for five rotationally symmetrical models for the regular Galactic gravitational field. Thirteen of sixteen mass-extinction events can be described by a repetition interval of 183±3 million years. This is in agreement with the anomalistic period (interval between two subsequent passages of the Sun through the apocenter of its Galactic orbit) in the model of Allen and Martos. The positions of the minima and maxima in Gaussian functions approximating the frequency distribution for geomagnetic reversals also agree with the times of passage of the Sun through the apocenter and pericenter, respectively, of its Galactic orbit in this model. The maximum in the distribution of the deviations of the dates of mass extinctions from the nearest dates of impacts of large, crater-forming bodies is close to zero, providing evidence that many such events are correlated. As a rule, extinctions follow impact events. The impacts of large bodies have occurred most often when the solar system passes through the Galactic plane, while mass extinctions occur more often at some distance from the Galactic plane (about 40 pc). As a rule, intervals of increases in the frequency of geomagnetic reversals coincide with dates of impacts of large bodies. At the same time, these intervals do not show a clear correlation with the dates of mass extinctions. The intensity of mass extinctions, like the energy released by impacts, is consistently higher in periods when the Sun is moving from the apocenter toward the pericenter of its orbit, than when it is moving from the pericenter toward the apocenter. Thus, there is evidence for a variety of relationships between repeating global events in the Phanerozoic and the motion of the Sun in the Galaxy. Long-period variations in the frequency of geomagnetic reversals are correlated with the orbital motion of the Sun, and increases in the frequency of geomagnetic reversals are correlated with impacts. Mass extinctions are correlated with the impacts of large bodies, whose motions may have been perturbed by clouds of interstellar material concentrated toward the Galactic plane and by the shock front associated with the Perseus spiral arm, through which the solar system passes. The velocity of the Sun relative to the spiral pattern is estimated. 相似文献
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摩擦桩基桩土间极限摩阻力取值问题探讨 总被引：1，自引：0，他引：1
通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。 相似文献
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位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压，而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩，榴辉岩及其他直接围岩皆呈包体存在于其中，并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体，表明新元古代花岗岩的组成物质也经受过超高压变质作用，且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次（或阶段）却少于榴辉岩。椐上述可得如下推断：超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部（俯冲板块前部）形成的；榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的，其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升，遭受剥蚀。 相似文献
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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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The structure of the eastern Pyrenees consists mainly of south-directed thrusts involving basement and cover rocks. An antiformal stack developed by the piling up of basement thrust sheets which outcrop in the Axial zone. These structures account for a thin-skinned thrust model rather than a vertical fault model in which the Axial zone would be essentially autochthonous, and the North-Pyrenean fault the axial plane of a fan thrust system. New data from the Eastern Pyrenees and the thin-skinned model suggest that(1) the structure east of the Pedraforca nappe is similar to that of the Central Pyrenees; (2) the cover rocks of the South-Pyrenean units and of the Axial zone-after restoration—built up a northwards-thickening prism consistent with the existence of a unique Pyrenean sedimentary basin during Mesozoic time; (3) the Axial zone is only a complex antiformal stack developed as a part of South-Pyrenean system related to the Paleogene thrusting-tectonics. The Axial zone palaeogeographic area had no special meaning during Mesozoic time. 相似文献
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Michel Westphal Mikhail L. Bazhenov Jean Paul Lauer Diamar M. Pechersky Jean-Claude Sibuet 《Tectonophysics》1986,123(1-4)
We first re-examined the apparent polar wander curves for stable Eurasia and Africa since the Triassic. These curves were then combined together with curves of North and South America according to the kinematics of the Atlantic ocean and a synthetic polar wander curve was given. Then, most of the paleomagnetic results from the Tethys mobile belt, from the Atlantic to the Pamirs, were analysed.Several groups of plates, microplates and blocks can be seen. First, relatively stable regions like Maghreb and Sicily, which have not moved much. Then we have a group formed by Iberia, Sardinia, Italy and, to a lesser extent, Corsica and the Western and Central Alps. For these blocks, movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of Africa, but they are sometimes stronger.To the east, a major change takes place. The north of the Aegean Sea and the Ionian zone are clockwise rotated and these rotations are recent: Oligocene-Miocene for the first part, Pliocene to the present for the second part.A major problem arises in Turkey, Caucasus and Iran. Paleomagnetic results indicate a position far to the south of Eurasia, and, at the same time, geological evidence is in favour of a position close to Eurasia. We discuss these discrepancies. 相似文献