同沉积褶皱生长地层中沉积与构造关系   总被引：4，自引：1，他引：3  

郭卫星  漆家福 《现代地质》2008,22(4):520-524

生长地层详细记录了褶皱变形的运动学特征及发展演化过程。对同沉积褶皱的生长地层进行详细的几何学分析,结合地层年代学资料,可以揭示沉积与构造的相互影响,确定沉积速率与构造抬升速率的细微变化,及褶皱的活动期次。构造抬升速率和沉积速率的变化,可引起生长地层的上超、超覆和退覆。褶皱的形成可分为膝折带迁移和翼部旋转2种模式。以膝折带迁移为变形机制的褶皱,发展过程中翼部倾角不变,褶皱顶部与翼部的抬升速率相同,形成翼部平行状生长地层;以翼部旋转为变形机制的褶皱,发展过程中翼部长度不变,沿翼部各点的抬升速率呈线性变化,形成翼部楔状的生长地层。  相似文献   

准噶尔盆地车排子隆起西南部原油地球化学特征及油源分析   总被引：6，自引：3，他引：3  

张枝焕  李伟  孟闲龙  秦黎明  张振英  袁东山 《现代地质》2007,21(1):133-140

车排子隆起毗邻昌吉凹陷和四棵树凹陷,油源丰富,构造条件良好,具备比较有利的油气聚集条件。近年来已在车排子隆起的侏罗系、白垩系、古近系和新近系获高产工业油气流。分析了车排子隆起西南部原油（或油砂抽提物）的地球化学特征,并对其油源作初步分析。结果表明研究区具有两类地球化学性质存在明显差别的原油。第一类原油遭受了不同程度的生物降解,并存在二次充注现象,推测早期充注原油来自昌吉凹陷二叠系,并遭受了不同程度的生物降解,后期混入了来自侏罗系烃源岩生成的原油。第二类原油具有侏罗系煤系烃源岩与白垩系湖相泥质烃源岩混源的特点,这类原油的碳同位素组成、正构烷烃分布特征和姥植比等均表现出煤成油的特征,但甾、萜烷烃类化合物组成与白垩系烃源岩接近,推测是由于侏罗系煤成油在向上运移成藏过程中,受到成熟度相对较低、生物标志物相对丰富的白垩系烃源岩的浸析作用所致。  相似文献   

多年冻土区灌注桩竖向抗拔承载力试验研究   总被引：1，自引：1，他引：0  

孙学先  张慧  田明 《岩土力学》2007,28(10):2110-2114

为研究多年冻土区桥梁及建筑物桩基抗冻拔的能力和变形性质,结合青藏铁路试验段工程,对青藏高原高温细颗粒多年冻土区钻孔灌注扩底桩和直孔桩现场抗拔力试验进行了研究,得到了两种桩型在同一地质和地温条件下的抗拔承载力及变形的试验结果。依据地温测试资料的分析,给出了桩-土体系回冻时间及地温变化特征。研究成果可为类似条件下抗冻拔桩基础设计与施工提供参考。  相似文献   

基于椭圆型滑动面的砂土中条形锚板上拔承载力计算方法     

杨枭  胡伟  孟建伟  林志 《海洋工程》2023,41(3):177-184

对于砂土中的竖向拉拔锚板,锚周土体滑动面的形态会随埋深比的增大而发生变化。基于滑动面连续演化的观点,审视了既有统一模型中滑动面形态表征函数的不足,在此基础上,提出了一种新的椭圆形态函数,并建立了相应的统一力学分析模型,提出了新的承载力计算方法。结果表明：新的形态函数能更好地反映滑动面的实际形态,承载力计算新方法也表现出了更好的适应性。  相似文献   

华北稳定参考框架NChina20的建立及应用     

鲍艳  王国权  于笑  肖根如  丁晓光  赵瑞斌  甘卫军 《中国地震》2020,36(4):788-805

选用中国大陆地壳运动观测台网（CMONOC）在华北地区约8年（2011年10月～2019年9月）的连续观测数据,建立了华北稳定参考框架——NChina20。NChina20与全球参考框架（IGS14）保持坐标系缩放比例一致,两坐标系统在历元2020.0对齐。本文详细介绍了将相对于IGS14的位置时间序列转换到NChina20的方法,并列举了NChina20在城市地面升降长期观测领域的应用。NChina20的稳定性（精度）在水平方向约为0.5mm/a,在垂直方向约为0.6mm/a。参考框架的稳定性随时间的推移而退化,建议NChina20的使用范围在时间上限于2006～2025年的时间窗口内,在空间上限于华北活动地块区域内。选用华北地区5个基岩站20年（2000～2019年）的连续观测数据,建立了华北地区季节性地面升降预测模型。华北稳定参考框架将每隔几年更新一次,以缓解框架稳定性随时间的退化,并与IGS参考框架同步更新。  相似文献   

地铁车站液化上浮响应及抗浮措施研究          下载免费PDF全文

张西文  朱伟东  李虎  葛珍珍  商金华  孙崇芳  司炜 《世界地震工程》2020,(1):205-211

地铁车站的地震液化上浮是地下结构常见的灾害之一,对处于液化场地的地铁车站需增加抗液化及抗浮措施。通过数值分析的方法对比分析了抗拔桩和隔离墙2种抗浮措施的作用机理及作用效果,研究了车站的上浮位移、地表变形和周围土体超孔隙水压比等动力响应。结果表明:设置抗拔桩可提供抗拔力,隔离墙可有效阻挡液化土的流动,因此地铁车站的上浮位移明显减小;抗拔桩的长度进入非液化土层时抗浮效果最佳;隔离墙的抗浮效果随着与车站主体的距离增加而减弱。通过该项研究,可为液化场地中地铁车站的抗浮设计提供一定的理论参考。  相似文献   

饱和砂土地铁车站的振动台试验研究          下载免费PDF全文

邵帅  邵生俊    马纯阳  王平 《世界地震工程》2019,35(4):162-170

地震作用下,饱和砂土地层地铁车站的动力反应特征是城市轨道工程抗震的关键问题。以太原地铁新近沉积粉细砂地层地铁工程为对象,通过模拟地震运动输入的饱和砂土地基地下结构的振动台模型试验,分析了不同峰值加速度地震作用下饱和砂土与地下结构相互作用的动力反应性状。研究了地震波作用的放大效应与频率特征,动孔压比增长发展过程和液化区域分布,以及动土压力的变化规律。表明加速度放大系数为1.5~2.0;0.1~0.25g峰值加速度地震作用下饱和砂土均产生动孔隙水压力累计发展;0.3g峰值加速度地震作用下饱和砂土产生液化,抑制了土与地下结构的振动放大效应,地表面大量冒水,结构模型出现了明显上浮,地下结构两侧产生震陷。  相似文献   

Experimental assessment of contact forces on a rigid base following footing uplift          下载免费PDF全文

Yuanzhi Chen  Tam Larkin  Nawawi Chouw 《地震工程与结构动力学》2017,46(11):1835-1854

A number of investigations in the recent decades have shown that footing uplift can reduce the seismic loading on a structure. Guidelines to design a structure with seismic uplift capability have been proposed. However, these studies mainly focus on the structural response and neglect the impact forces on the footing from re‐contact between the footing and the supporting medium. A small number of computational studies of the induced forces on the footing have been performed. This paper presents the results of free vibrations and shake table tests on a single degree‐of‐freedom model of a bridge pier with footing uplift on a rigid base. Two support conditions are considered, that is, footing fixed to the base and footing free to uplift on a rigid base. Load cells were placed at the interface of the footing and rigid base to measure the contact forces during structural vibration. The footing responses of both flexible and rigid structures due to free vibration are compared. The results show that the flexibility of the structure has significant effects on footing uplift duration and amplitude and reduces the contact force, in some cases very significantly. The flexible structure was also subjected to harmonic base excitations. It is found that varying the characteristics of the excitation changes the uplift amplitude but does not affect the contact force significantly. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

BURIAL AND EXHUMATION OF THE XIGAZE FORE-ARC BASIN FROM LOW TEMPERATURE THERMOCHRONOLOGICAL EVIDENCE     

GE Yu-kui  ZENG Jing  ZHANG Jin-yu  LI Ya-lin 《地震地质》2019,41(2):447-466

The Xigaze fore-arc basin is adjacent to the Indian plate and Eurasia collision zone. Understanding the erosion history of the Xigaze fore-arc basin is significant for realizing the impact of the orogenic belt due to the collision between the Indian plate and the Eurasian plate. The different uplift patterns of the plateau will form different denudation characteristics. If all part of Tibet Plateau uplifted at the same time, the erosion rate of exterior Tibet Plateau will be much larger than the interior plateau due to the active tectonic action, relief, and outflow system at the edge. If the plateau grows from the inside to the outside or from the north to south sides, the strong erosion zone will gradually change along the tectonic active zone that expands to the outward, north, or south sides. Therefore, the different uplift patterns are likely to retain corresponding evidence on the erosion information. The Xigaze fore-arc basin is adjacent to the Yarlung Zangbo suture zone. Its burial, deformation and erosion history during or after the collision between the Indian plate and Eurasia are very important to understand the influence of plateau uplift on erosion. In this study, we use the apatite fission track(AFT)ages and zircon and apatite(U-Th)/He(ZHe and AHe)ages, combined with the published low-temperature thermochronological age to explore the thermal evolution process of the Xigaze fore-arc basin. The samples' elevation is in the range of 3 860~4 070m. All zircon and apatite samples were dated by the external detector method, using low~U mica sheets as external detectors for fission track ages. A Zeiss Axioskop microscope(1 250×, dry)and FT Stage 4.04 system at the Fission Track Laboratory of the University of Waikato in New Zealand were used to carry out fission track counting. We crushed our samples finely, and then used standard heavy liquid and magnetic separation with additional handpicking methods to select zircon and apatite grains. The new results show that the ZHe age of the sample M7-01 is(27.06±2.55)Ma(Table 2), and the corresponding AHe age is(9.25±0.76)Ma. The ZHe and AHe ages are significantly smaller than the stratigraphic age, indicating suffering from annealing reset(Table 3). The fission apatite fission track ages are between(74.1±7.8)Ma and(18.7±2.9)Ma, which are less than the corresponding stratigraphic age. The maximum AFT age is(74.1±7.8)Ma, and the minimum AFT age is(18.7±2.9)Ma. There is a significant north~south difference in the apatite fission track ages of the Xigaze fore-arc basin. The apatite fission track ages of the south part are 74~44Ma, the corresponding exhumation rate is 0.03~0.1km/Ma, and the denudation is less than 2km; the apatite fission track ages of the north part range from 27 to 15Ma and the ablation rate is 0.09~0.29km/Ma, but it lacks the exhumation information of the early Cenozoic. The apatite(U-Th)/He age indicates that the north~south Xigaze fore-arc basin has a consistent exhumation history after 15Ma. The results of low temperature thermochronology show that exhumation histories are different between the northern and southern Xigaze fore-arc basin. From 70 to 60Ma, the southern Xigaze fore-arc basin has been maintained in the depth of 0~6km in the near surface, and has not been eroded or buried beyond this depth. The denudation is less than the north. The low-temperature thermochronological data of the northern part only record the exhumation history after 30Ma because of the young low-temperature thermochronological data. During early Early Miocene, the rapid erosion in the northern part of Xigaze fore-arc basin may be related to the river incision of the paleo-Yarlungzangbo River. The impact of Great Count Thrust on regional erosion is limited. The AHe data shows that the exhumation history of the north-south Xigaze fore-arc basin are consistent after 15Ma. In addition, the low-temperature thermochronological data of the northern Xigaze fore-arc basin constrains geographic range of the Kailas conglomerate during the late Oligocene~Miocene along the Yarlung Zangbo suture zone. The Kailas Basin only develops in the narrow, elongated zone between the fore-arc basin and the Gangdese orogenic belt. The southern part of the Xigaze fore-arc basin has been uplifted from the sea level to the plateau at an altitude of 4.2km, despite the collision of the Indian plate with the Eurasian continent and the late fault activity, but the plateau has been slowly denuded since the early Cenozoic. The rise did not directly contribute to the accelerated erosion in the area, which is inconsistent with the assumption that rapid erosion means that the orogenic belt begins to rise.  相似文献   

Continental drift,plateau uplift,and the evolutions of monsoon and arid regions in Asia,Africa, and Australia during the Cenozoic     

Xiaodong LIU  Buwen DONG  Zhi-Yong YIN  Robin S.SMITH  Qingchun GUO 《中国科学:地球科学(英文版)》2019,(7):1053-1075

Monsoon and arid regions in the Asia-Africa-Australia(A-A-A) realm occupy more than 60% of the total area of these continents. Geological evidence showed that significant changes occurred to the A-A-A environments of the monsoon and arid regions, the land-ocean configuration in the Eastern Hemisphere, and the topography of the Tibetan Plateau(TP) in the Cenozoic. Motivated by this background, numerical experiments for 5 typical geological periods during the Cenozoic were conducted using a coupled ocean-atmosphere general circulation model to systemically explore the formations and evolutionary histories of the Cenozoic A-A-A monsoon and arid regions under the influences of continental drift and plateau uplift. Results of the numerical experiments indicate that the timings and causes of the formations of monsoon and arid regions in the A-A-A realm were very different. The northern and southern African monsoons existed during the mid-Paleocene, while the South Asian monsoon appeared in the Eocene after the Indian Subcontinent moved into the tropical Northern Hemisphere. In contrast, the East Asian monsoon and northern Australian monsoon were established much later in the Miocene. The establishment of the tropical monsoons in northern and southern Africa, South Asia, and Australia were determined by both the continental drift and seasonal migration of the Inter-Tropical Convergence Zone(ITCZ), while the position and height of the TP were the key factor for the establishment of the East Asian monsoon. The presence of the subtropical arid regions in northern and southern Africa,Asia, and Australia depended on the positions of the continents and the control of the planetary scale subtropical high pressure zones, while the arid regions in the Arabian Peninsula and West Asia were closely related to the retreat of the Paratethys Sea. The formation of the mid-latitude arid region in the Asian interior, on the other hand, was the consequence of the uplift of the TP.These results from this study provide insight to the important roles played by the earth's tectonic boundary conditions in the formations and evolutions of regional climates during geological times.  相似文献