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1.
油井套管往往处于管内外复杂的受力环境下,揭示和分析这些因素对套管抗挤能力的影响就显得非常重要,并可为套管强度设计提供理论依据。根据套管在受到外部非均匀载荷和内压作用下的受力特点和材料力学理论,建立了单位长度的理想圆管的环向应力的计算模型,得到了套管内外壁的环向应力分布规律。计算结果表明：套管发生破坏失效位置在圆周方向与最大水平地应力成90°角的内壁上。依据Von Mises屈服准则由失效点得到了非均匀外挤载荷和内压作用下套管屈曲时抗外挤能力的新公式。实例计算表明：在影响套管的抗挤能力的因素中,外载荷的非均匀系数对套管抗外挤能力影响最大,外载荷的非均匀系数越大,套管抗外挤能力下降得越快;在外载荷非均匀性较小的条件下,提高套管外载荷承载能力可通过增大内压和减小套管径厚比来实现。 相似文献
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目前大多数油井套管的损坏很大程度上是由非均匀载荷引起的,外载荷的非均匀性等因素大大降低了套管的承载能力,为此,揭示这些因素对套管抗挤能力的影响具有重要的实际意义。根据非均匀椭圆载荷作用下套管的受力特点,利用材料力学理论建立了理想套管的环向应力计算模型,分析了套管的应力分布规律,结果表明：套管承载的危险点为圆周方向与最大水平地应力成90°夹角的内壁上,与有限元数值模拟结果有着很好的一致性。并以危险点应力状态为依据,得到了套管在不同的非均匀载荷下的等效外挤压力计算的新公式。计算结果表明,椭圆载荷中的非均匀部分对套管等效外挤压力影响极大;外载荷非均匀度越大,径厚比越大,套管承受外挤载荷能力越差,越容易发生挤毁失效。 相似文献
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在含水率大、抗剪强度低的淤泥中采用抛石挤淤的办法加固地基或建造围埝,处理效果好且经济效益显著,因此得到了广泛地应用。抛石在软弱地基中下沉,直至其重力与地基承载力平衡为止。挤淤所形成截面的形状及抛石下沉深度的计算是此项研究的重点,基于抛石截面为倒梯形和矩形两种形状的假定,考虑淤泥表面隆起对承载力的影响,利用土体极限平衡理论,推导出抛石挤淤深度与抛石高度的关系。通过抛石挤淤的模型试验和现场挤淤的数据,分析比较两种假定下挤淤公式的准确性和适用性,试验结果与公式吻合性很好,该研究结果可为相关工程的设计和施工提供参考。 相似文献
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通过对挤扩支盘桩和常规泥浆护壁钻孔灌注桩两种桩型的对比分析，前者具有承载力高、用料省的优点。介绍了挤扩支盘桩的成桩工艺，并对其单桩承载力进行了计算。经载荷试验检测，挤扩支盘桩单桩极限承载力〉5000kN，累计沉降量仅25mm，完全满足设计要求。 相似文献
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用标贯击数确定抗液化振动挤密砂桩的间距 总被引：2，自引：0，他引：2
在考虑了抗液化振动挤密砂桩的侧向和竖向加密的同时,又考虑了砂桩的充盈系数对加固作用的影响,从而提出了一种基于抗震规范的液化判别方法,根据标准贯入击数确定抗液化振动挤密砂桩间距的经验关系。 相似文献
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本文通过用２：８灰土挤密桩处理湿陷性黄土地基的几个典型工程试验成果的分析与总结，揭示了灰土桩复合地基承载力的相应公式，为灰土挤密桩地基设计提供了更为方便的，切合实际的计算方法，便于工程设计人员使用。 相似文献
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本文通过用２：８灰土挤密桩处理湿陷性黄土地基的几个典型工程试验成果的分析与总结，揭示了灰土桩复合地基桩土应力比值ｎ与荷载、相对应变之间的关系，给出了在允许承载力下ｎ值的大小及计算桩间土承载力和复合地基承载力的相应公式，为灰土挤密桩地基设计提出了更为方便的、切合实际的计算方法，便于工程设计人员使用． 相似文献
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Inter-regional correlation of transgressions and regressions in the Cretaceous period 总被引：1，自引：0，他引：1
T. Matsumoto 《Cretaceous Research》1980,1(4):359-373
Well investigated platforms have been selected in each continent, and the history of Cretaceous transgressions and regressions there is concisely reviewed from the available evidence. The factual records have been summarized into a diagram and the timing of the events correlated between distant as well as adjoining areas.On a global scale, major transgressions were stepwise enlarged in space and time from the Neocomian, via Aptian-Albian, to the Late Cretaceous, and the post-Cretaceous regression was very remarkable. Minor cycles of transgression-regression were not always synchronous between different areas. Some of them were, however, nearly synchronous between the areas facing the same ocean.Tectono-eustasy may have been the main cause of the phenomena of transgression-regression, but certain kinds of other tectonic movements which affected even the so-called stable platforms were also responsible for the phenomena. The combined effects of various causes may have been unusual in the Cretaceous, since it was a period of global tectonic activity. The slowing down of this activity followed by readjustments may have been the cause of the global regression at the end of the Cretaceous. 相似文献
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A Barremian microflora is recorded in the terrigenous facies (Weald) of the Lower Cretaceous in the northern region of the Province of Valencia (Spain), these beds have been poorly dated up to now due to the absence of fossils. The Villar del Arzobispo microflora correspond unquestionably to the Barremian-Aptien period, but the numerical importance of derived forms from the Jurassic, the remarkable variety of forms of Cicatricosisporites, and the rareness of pollen of Angiosperms, indicate a Barremian age to be more likely.This discovery permits us to establish the stratigraphical relationship of this terrigenousfacies of Villar del Arzobispo with the dated “Weald” of other areas of the Iberian Chain and to give a complete chrono-stratigraphical interpretation to the different litho-stratigraphical units that constitute the Lower Cretaceous of this region. 相似文献
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根据丽江至香格里拉铁路中义隧道变形及电磁辐射的现场监测资料，对隧道变形过程中的电磁辐射特性及电磁辐射强度极大峰值事件数N、超过强度平均值的极大峰值事件数M与隧道水平收敛变形的关系进行了统计分析。研究表明：（1）电磁辐射最大强度平均值E在初期支护破坏前，随隧道变形的增大而增大，初期支护破坏后，随隧道变形的增大而减少，电磁辐射最大强度平均值先升后降的出现时间与初期支护破坏的时间接近。（2）电磁辐射强度极大峰值事件数、超过强度平均值的极大峰值事件数的波动速率 、 与隧道变形速率呈正线性相关关系；电磁辐射强度极大峰值事件数、超过强度平均值的极大峰值事件数的百分比 、 与隧道累计变形呈正线性相关关系。结论对深化地下洞室变形过程中的电磁辐射特性的认识，提高电磁辐射监测技术的现场应用水平具有指导意义。 相似文献
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苏皖坡缕石粘土中蛋白石特征及其成因意义 总被引：1，自引：0，他引：1
TEM和XRD研究表明，在苏皖坡缕石粘土矿床的蛋白石坡缕石层中存在0pal-A和0pal-CT两种结构的蛋白石。蛋白石坡缕石层主要含坡缕石、opal-A、opal-CT，以及少量白云石和其它矿物，由富opal-A层和富opal-CT层互层组成，交互层的厚度在几个厘米左右。蛋白石坡缕石层中的矿物基本是自生矿物，从蒸发湖水中化学沉淀形成。矿物组成特征研究表明，蛋白石坡缕石层的矿物组分(Si、Mg、Al)来源于盆地周围玄武岩淋滤的浅层地下水。根据Opal-A和Opal-CT溶解度图解和城缕石、白云石形成物理化学条件图解，当湖水具有高浓度溶解SiO2和Mg^2 时，有利于opal-A和坡缕石形成，当湖水具有低浓度溶解SiO2时，有利于opal-CT结晶。因此，沉淀SiO2的结构状态取决于地下水补给的湖水溶解SiO2浓度。富opal-A和富opal-CT交互层的形成是古气候、古水文周期性变化的指示。富opal-CT层指示高地下水补给流入量，低蒸发量，湖水低盐度和溶解组分，代表湿润气候时期；而富opal-A层代表低地下水补给流入量，高蒸发量，高溶解组分浓度，代表干旱气候时期。 相似文献
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B. D. Webby 《Australian Journal of Earth Sciences》2013,60(1-2):41-63
Much of South Australia, western New South Wales, and Tasmania was affected by the Late Cambrian‐Early Ordovician Delamerian Orogeny. Areas of the former shelf margin exhibit molasse‐type conglomerates overlying a major late Middle to Late Cambrian unconformity (Jukesian Movement in Tasmania or Mootwingee Movement in western N.S.W.). In continental platform areas to the north the effects of the orogeny were less intense with, in the Georgina Basin for instance, only dis‐conformable relationships, and the overlying deposits consisting of fine elastics and carbonates. Regression accompanied this first phase of tectonic upheaval and was followed by a period of ‘late Tremadoc’ transgression of the sea into several embayment areas of the continental platform. This short‐lived transgression was succeeded by ‘early Arenig’ regression which appears to be related to a second, less intense Delamerian orogenic phase. Expression of this phase ranges from unconformity in west Tasmania (Haulage and Lynchford Movements) to disconformity in the Georgina Basin (Kelly Creek Movement). A second, more extensive and long‐lived transgression of the sea from the ‘middle Arenig’ to about the end of the ‘Llanvirn’ resulted in the development of the epicontinental Larapintine Sea, permitting interchange of warmer and cooler waters from either ends of the seaway. Combined fossil, lithological and palaeomagnetic evidence suggests that, of the fragments of Gondwanaland, Australia alone straddled the Ordovician equator, with its present west coast approximately along the line of Lat. 30°S. Influxes of sand from the areas of mild‐high relief to the south appear to have been deflected in an anticlockwise direction along the open, ocean‐facing Gnalta Shelf of western N.S.W. towards the eastern end of the Larapintine Sea perhaps as a result of a major westward‐flowing equatorial current. The influxes progressively constricted and finally blocked off the eastern end of the seaway by the end of ‘Llanvirn’ time. The closure, and final regression of the sea from all continental platform areas, seems to have been accompanied by a phase of local uplift and erosion (Dullingari Movement of northeastern South Australia). In cratonic areas of central and northern Australia a period of Late Ordovician or Early Silurian uplift and erosion (Rodingan Movement) followed. Dullingari and Rodingan Movements may be correlated with phases of the Benambran Orogeny of the Tas‐man Geosyncline. Late Ordovician cratonic sedimentation was restricted to the shelf margin. On the Tasmanian Shelf carbonates accumulated during a long period of relative tectonic quiescence and gentle subsidence. First signs of onset of the Benambrian Orogeny are shown by the appearance of clastics in the topmost beds of the Tasmanian Ordovician sequence. 相似文献
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László Ódor Richard B Wanty István Horváth Ubul Fügedi 《Journal of Geochemical Exploration》1998,65(1):47-60
Regional geochemical baseline values have been established for Hungary by the use of low-density stream-sediment surveys of flood-plain deposits of large drainage basins and of the fine fraction of stream sediments. The baseline values and anomaly thresholds thus produced helped to evaluate the importance of high toxic element concentrations found in soils in a valley downstream of a polymetallic vein-type base-metal mine. Erosion of the mine dumps and flotation dump, losses of metals during filtering, storage and transportation, human neglects, and operational breakdowns, have all contributed to the contamination of a small catchment basin in a procession of releases of solid waste. The sulfide-rich waste material weathers to a yellow color; this layer of `yellow sand' blankets a narrow strip of the floodplain of Toka Creek in the valley near the town of Gyöngyösoroszi. Contamination was spread out in the valley by floods. Metals present in the yellow sand include Pb, As, Cd, Cu, Zn, and Sb. Exposure of the local population to these metals may occur through inhalation of airborne particulates or by ingestion of these metals that are taken up by crops grown in the valley. To evaluate the areal extent and depth of the contamination, active stream sediment, flood-plain deposits, lake or reservoir sediments, soils, and surface water were sampled along the erosion pathways downstream of the mine and dumps. The flood-plain profile was sampled in detail to see the vertical distribution of elements and to relate the metal concentrations to the sedimentation and contamination histories of the flood plain. Downward migration of mobile Zn and Cd from the contaminated upper layers under supergene conditions is observed, while vertical migration of Pb, As, Hg and Sb appears to be insignificant. Soil profiles of 137Cs which originated from above-ground atomic bomb tests and the Chernobyl accident, provide good evidence that the upper 30–40 cm of the flood-plain sections, which includes the yellow sand contamination, were deposited in the last 30–40 years. 相似文献
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The experimental study of the hydrodynamics of the sediments and the physical analysis of the process of exchange at the water-sediment interface in a zone of swash are essential for the understanding of the sedimentary transport processes in coastal environments, in particular to control and forecast the evolution of the coastline. The objective of this study was to exploit the technique of Ultrasonic Doppler Velocimetry (UDV) to examine the evolution of the velocity field at the water-sediment interface in a zone of swash in various conditions of incidental regular waves in a wave flume. The velocities were measured in different conditions of the swash within the sediment bed, and in the fluid vein at the swash edge. These measurements show: an exponential distribution of velocities inside the sediment bed; a difference in the velocity gradient at the water-sediment interface, between the velocity in the water vein at the swash edge and the interstitial flow in the swash. The measurements obtained in the wave flume made it possible to observe an evolution of the velocity profiles according to the phases of the swash, which are characterized by a phase shift between the free flow at the swash edge and the interstitial flow during the two phases of the swash: uprush and backwash. 相似文献
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哈密尾亚地区花岗岩类副矿物特征对比 总被引：1，自引：0，他引：1
壳－幔混合源型、壳源高铝型、深源碱性型等不同成因的花岗岩类，在演化过程中，其副矿物组合特征是不同的。主要表现在磁铁矿与钛铁矿，锆石与磷灰石之间的含量及比值，以及花岗岩形成演化到中－晚期时，褐帘石、萤石、独居石、石榴石等的出现及其含量多少，在副矿物组合图上表现出不同的曲线形态。尤其锆石晶体形态（在皮藩“ｐｕｐｉｎ”群型图上）的分布位置，与花岗岩成因类型密切相关。锆石的晶面、晶棱特点，可直接反映花岗岩时代的新老。而锆石晶体的长短轴之比、包裹体特征和磷灰石的晶面、晶棱特点、包裹体特征等，在不同代，不同成因类型的花岗岩中都有区别，均具有对比意义。 相似文献
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Summary Finite element analyses were conducted to investigate the magnitude of tensile strains imposed on landfill liners due to the
formation of subsurface cavities. The study incorporated the significance of using geogrids to reduce the magnitude of strains
and possibly the potential for collapse of landfill liners. Variations of key parameters included depth of overburden (D) and diameter of the cavity (B). Estimated stress distributions were compared to theoretical values obtained from a model reported in the literature.
Results indicated that, contrary to conventional wisdom, the critical area based on the mechanics of arching was above the
edge of the cavity where stress concentration occurred. Incorporation of geogrid reinforcement reduced the magnitude of tensile
strains. The tensile force in the geogrid was dependent upon the size of the cavity, the depth of the overburden, and the
applied pressure. 相似文献