Experimental investigation on seismic behavior of scoured bridge pier with pile foundation          下载免费PDF全文

Shiou‐Chun Wang  Kuang‐Yen Liu  Chia‐Han Chen  Kuo‐Chun Chang 《地震工程与结构动力学》2015,44(6):849-864

This study investigated the seismic performance and soil‐structure interaction of a scoured bridge models with pile foundation by shaking table tests using a biaxial laminar shear box. The bridge pier model with pile foundation comprised a lumped mass representing the superstructure, a steel pier, and a footing supported by a single aluminum pile within dry silica sand. End of the pile was fixed at the bottom of the shear box to simulate the scenario that the pile was embedded in a firm stratum of rock. The bridge pier model was subjected to one‐directional shakes, including white noise and earthquake records. The performance of the bridge pier model with pile foundation was discussed for different scoured conditions. It is found that the moment demand of pile increases with the increase of scoured depth whereas the moment demand of the bridge pier decreases, and this transition may induce the bridge failure mechanism transform from pier to pile. The seismic demand on scoured pile foundations may be underestimated and misinterpreted to a certain degree. When evaluating the system damping ratio with SSI, the system response may not be significantly changed even if the soil viscous damping contribution is varied. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

三峡库首区高桥断裂带断层泥分形特征研究     

高红亮  姚运生  王秋良  张丽芬  陈星星 《大地测量与地球动力学》2015,35(6):963-968

三峡水库蓄水前后,沿高桥断裂带发生了一系列地震活动。为了解断层泥特征与断裂活动的关系,在野外地质调查基础上,对高桥断裂带内的断层泥进行X光衍射和粒度分布测试。结果显示,高桥断裂带断层泥的粘土矿物含量一般低于35%,并且主要矿物为不具膨胀性的绿泥石和伊利石|断层泥分维值在2.20～2.67之间变化,表明高桥断裂带的运动方式以粘滑为主。断层力学性质和断层泥分维计算均表明其具有分段性,结合断裂附近的地震活动认为,北东段较南西段稳定,但不排除高桥断裂带未来有发生中强地震的可能性。  相似文献   

The climatic impacts of land use and land cover change compared among countries   总被引：2，自引：0，他引：2  

Jiyuan Liu  Quanqin Shao  Xiaodong Yan  Jiangwen Fan  Jinyan Zhan  Xiangzheng Deng  Wenhui Kuang  Lin Huang 《地理学报(英文版)》2016,26(7):889-903

Land use and land cover change (LULCC) strongly influence regional and global climate by combining both biochemical and biophysical processes. However, the biophysical process was often ignored, which may offset the biogeochemical effects, so measures to address climate change could not reach the target. Thus, the biophysical influence of LULCC is critical for understanding observed climate changes in the past and potential scenarios in the future. Therefore, it is necessary to identify the mechanisms and effects of large-scale LULCC on climate change through changing the underlying surface, and thus the energy balance. The key scientific issues on understanding the impacts of human activities on global climate that must be addressed including: (1) what are the basic scientific facts of spatial and temporal variations of LULCC in China and comparative countries? (2) How to understand the coupling driving mechanisms of human activities and climate change on the LULCC and then to forecasting the future scenarios? (3) What are the scientific mechanisms of LULCC impacts on biophysical processes of land surface, and then the climate? (4) How to estimate the contributions of LULCC to climate change by affecting biophysical processes of land surface? By international comparison, the impacts of LULCC on climate change at the local, regional and global scales were revealed and evaluated. It can provide theoretical basis for the global change, and have great significance to mitigate and adapt to global climate changes.  相似文献   

华北克拉通南缘汝阳群大型具刺疑源类时代再厘定及早期真核生物群演化意义^*   总被引：1，自引：0，他引：1       下载免费PDF全文

彭楠  旷红伟  柳永清  耿元生  夏晓旭  王玉冲  陈骁帅  郑行海 《古地理学报》2018,20(4):595-608

华北克拉通南缘汝阳群中以大型具刺疑源类为代表的真核生物群的时代归属问题一直存在争议。新近在豫西汝州阳坡村洛峪群洛峪口组中获得的凝灰岩锆石SHRIMP U-Pb年龄为1639±13Ma,结合熊耳群和汝阳群已获得的其他年龄数据,将这类形态复杂的真核生物群出现的时间限定在1.75—1.64Ga,即中元古代的早期。这说明,过去一直被认为的代表进化程度较高但仅属于新元古代的一些真核生物群,其实在中元古代早期就已经出现了;由此可以进一步推测,在更古老的地层中应有更原始的微体化石出现,从而华北克拉通南缘中元古界(>1.60Ga)将成为探寻最古老真核生物祖先的重要窗口。同时,将这些在中元古代早期就已经出现并在以后较长地史时期都存在的真核生物群用于标定地层形成时代或作为相关地层的对比标志,值得重新考虑和商榷。  相似文献   

山东沭河裂谷带早白垩世晚期恐龙足迹群与古地理背景^*          下载免费PDF全文

旷红伟  柳永清  吴清资  程光锁  许克民  刘海  彭楠  许欢  陈军  王宝红  徐加林  汪明伟  章朋 《古地理学报》2013,15(4):435-453

山东沭河裂谷带由北至南发育8个早白垩世晚期(大盛期）的恐龙足迹群化石点,其中5处为本研究首次报道。沭河裂谷带足迹化石点多,分布广,层位多,足迹数量和造迹恐龙种类丰富。郯城新发现的单个蜥脚类巨型足迹直径近1.0m,可能仅次于前人描述过的兰州西南盐锅峡下白垩统河口群内中国最大的蜥脚类足迹化石。沭河裂谷带的恐龙足迹产出于大盛群田家楼组,地质年代为110～100Ma,属于早白垩世晚期Aptian晚期—Albian期。恐龙足迹一般为凹形印痕,造迹者以蜥脚类恐龙为主,其次为鸟脚类和兽脚类。足迹多保存在发育波痕、泥裂、雨痕等沉积构造的细砂—粉砂岩沉积物层面。足迹和行迹特征显示造迹恐龙为群居和在栖息地漫步行走状态。足迹原位保存特征及赋存地层沉积学研究表明,早白垩世中晚期气候处于由温暖潮湿变得炎热干旱的过渡期,湖泊、三角洲广布,恐龙栖息于湖滨环境。沭河裂谷带早白垩世晚期恐龙足迹群的发现和综合研究进一步证实,中国早白垩世恐龙动物群有着更广阔的地理分布和相似的古地理环境。  相似文献   

山东临沭地区早白垩世晚期恐龙足迹化石特征^*   总被引：1，自引：0，他引：1       下载免费PDF全文

陈军  旷红伟  柳永清  吴清资  程光锁  许克民  彭楠  许欢  刘海  徐加林  汪明伟  王宝红  章朋 《古地理学报》2013,15(4):505-516

主要记述了山东临沭地区早白垩世晚期(大盛群沉积时期）、生活于干旱炎热气候条件下滨浅湖环境的恐龙所留下的大规模足迹化石群。初步研究表明,这些足迹以蜥脚类恐龙足迹占绝大多数,见少量鸟脚类、兽脚类和疑似甲龙类足迹(甲龙类足迹在中国罕见),足迹总体行进方向以向西和南西为主。通过对其中的2条蜥脚类和1条鸟脚类行迹及其行为学的分析认为其均处于慢行状态,而鸟脚类行迹的运动速度极慢,可能处于一种特殊的慢行状态。临沭地区早白垩世晚期大盛期如此大规模足迹化石群的发现,说明中国乃至东亚地区早白垩世普遍存在着以恐龙为代表的(包括鸟类在内）陆生脊椎动物群。足迹化石的研究将对进一步了解晚中生代陆地生物群的演化有着重要意义。对比其他地区早白垩世晚期地层中发现的恐龙足迹化石特征后认为,足迹的保存与当时的沉积环境有密切的关系,因此对恐龙足迹的研究又能进一步为恢复古生态、古地理环境等提供更丰富的信息。  相似文献   

岩浆中心成矿系——岩浆岩体和矿床组合的空间分带理想模式   总被引：1，自引：0，他引：1  

岑况  田兆雪 《现代地质》2012,26(5):1051-1057

系统总结和分析了当前大量热液金属矿床与岩浆岩体的空间和成因关系,参考首先由俄罗斯地球化学家提出的以矿床为中心的元素地球化学理想分带模式,提出了以岩浆岩为中心的矿床理想分布模式--“岩浆中心成矿系”。该模式以侵入近地表含水围岩的岩浆岩体顶部为中心,一个完整的高温矿床→中温矿床→低温矿床从内带-过渡带-中带-外带有规律分布。内带主要为Nb、Ta、Hf、Li等经常在岩浆岩体内生成的矿床,形态受岩浆岩体控制,多为等轴状;过渡带为W、Sn、Mo、Bi等高温热液矿床,形态以三维等轴状为主;中带为Cu、Pb、Zn等中温矿床,以透镜状、脉状为主;外带为Au、Hg、Sb等低温矿床,矿体呈脉状、串珠状,受构造线控制,顺从构造线分布。矿床系列围绕岩浆中心成矿有独特的形成过程：岩浆岩侵入含水围岩后,形成局部高温度场并导致热液和矿床物质循环和温度场内的时空温度差是岩浆中心成矿系形成的关键。在理想模式下产生的个体(岩体矿床组合体）同时受到形成条件的影响：岩浆体侵入的深度、围岩的岩性或含水性,岩浆的物理化学性质、侵入温度、岩浆规模都会导致岩浆中心成矿系的完整性和形态等变异。  相似文献   

Spatio-temporal patterns of intra-urban land use change in Beijing, China between 1984 and 2008   总被引：1，自引：1，他引：0  

Wenhui Kuang 《中国地理科学(英文版)》2012,22(2):210-220

Urban internal structure is essential information for urban geography researchers and urban planners or managers. This research aims to examine the spatial structure changes of internal urban land use based on the interpreted datasets of 1984 and 2008. Spatio-temporal patterns of internal land use conversion and urban expansion are analyzed, and then dominant driving factors (e.g., social economy, population growth and urban planning) were identified. The results indicate that Beijing′s intra-urban layout has experienced tremendous adjustment from compact to disperse configure, otherwise its function objects have shifted from the major economic and industrial development before the 1990s to the combination with cultural, high-technological and inhabitable city at present. The dominant urban land use transformations include the relocation of industrial lands from core districts to suburban or other provinces, and the accelerating expansion of residential areas and green spaces for supplying the demand of housing and ecological protection. Although Beijing′s urban planning has experienced three major adjustments and improvement since the 1980s, its optimization of urban internal patterns still remains a challenge.  相似文献   

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金蕾  匡翠林 《大地测量与地球动力学》2012,32(6):119-122

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匡翠林  张晋升  曾凡河  戴吾蛟 《大地测量与地球动力学》2012,32(6):139-143

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