亚欧大陆桥与青海旅游业     

张忠孝  朱丽东 《干旱区地理》1996,(1)

在简述亚欧新陆桥在我国境内基本概况及旅游潜力估价的基础上，从青海旅游资源特征出发，探讨了青海旅游业在新陆桥中国旅游业中的特殊地位及青海旅游业发展在青海经济开发中的战略意义．  相似文献   

古丝绸之路与新亚欧大陆桥：河西走廊经济发展思考     

姚建华  郎一环 《干旱区地理》1996,19(1):10-13

河西走廊在古丝绸之路中占有重要的地位和作用。新亚欧大陆桥开通之后，河西能否依桥再现辉煌，必须从古丝路与新陆桥的特点出发，作对比研究。本文分析了沿海和沿桥的历史特点与现状，提出了河西经济发展应采取的积极主动对策，即主动上桥、逼桥赐惠；人车分离与千方引客；西进东出、走出封闭。  相似文献   

Seismic response of isolated bridges with soil–structure interaction     

N. P. Tongaonkar  R. S. Jangid   《Soil Dynamics and Earthquake Engineering》2003,23(4):287-302

The modern transportation facilities demand that the bridges are to be constructed across the gorges that are located in seismically active areas and at the same time the site conditions compel the engineers to rest the pier foundation on soil. The purpose of this study is to assess the effects of soil–structure interaction (SSI) on the peak responses of three-span continuous deck bridge seismically isolated by the elastomeric bearings. The emphasis has been placed on gauging the significance of physical parameters that affect the response of the system and identify the circumstances under which it is necessary to include the SSI effects in the design of seismically isolated bridges. The soil surrounding the foundation of pier is modelled by frequency independent coefficients and the complete dynamic analysis is carried out in time domain using complex modal analysis method. In order to quantify the effects of SSI, the peak responses of isolated and non-isolated bridge (i.e. bridge without isolation device) are compared with the corresponding bridge ignoring these effects. A parametric study is also conducted to investigate the effects of soil flexibility and bearing parameters (such as stiffness and damping) on the response of isolated bridge system. It is observed that the soil surrounding the pier has significant effects on the response of the isolated bridges and under certain circumstances the bearing displacements at abutment locations may be underestimated if the SSI effects are not considered in the response analysis of the system.  相似文献   

Damping/global energy balance in FE model of bridge foundation lateral response     

R. Dobry  A. Pecker  G. Mavroeidis  M. Zeghal  B. Gohl  D. Yang   《Soil Dynamics and Earthquake Engineering》2003,23(6):483-495

A global energy analysis is presented of three static unloading–reloading foundation lateral loading cycles, calculated using the nonlinear finite element (FE) program DYNAFLOW. This simulates seismic action on an offshore pier foundation in the Rion-Antirion Bridge in Greece, located in deep-sea water (65 m). A cyclic horizontal force is applied at a height of 30 m to a rigid raft 78 m in width placed on the surface of an idealized 2-layer soil profile consisting of a 3.5 m man-made gravel layer over soft deep natural clay, with elastic vertical steel inclusions reinforcing the soil. Results of the two-dimensional FE run are used for the energy analysis. It is verified that for the three cycles, the sum of energies associated with the external forces and moments, mostly dissipated through hysteresis loops, is about equal to the sum of the total internal energies dissipated or stored in the system. For the smaller loops almost all energy is dissipated in the soil, while for the largest loop about half of the energy is dissipated by horizontal sliding at the raft-soil interface. Global damping ratios obtained from the areas of the horizontal and rocking moment hysteresis loops are about double of those computed from the corresponding static backbone curves using the Masing criterion.  相似文献   

Environmental hazards in Xinjiang Line of New Eurasian Continental Bridge     

陈亚宁  李卫红  杨思全  徐海量 《中国科学D辑(英文版)》2002,45(Z1)

Xinjiang Line of New Eurasian Continental Bridge is the important lifeline project inwestern China. Various disasters, such as flood, strong wind, sandstorm, and roadbed disasters,have been seriously affecting the railway transportation. The field investigation and analysis on thedata collected since 1959 show that: serious floods often occurred when the rain intensity reached25 mm/h or 30 mm/d; the critical wind speed for turning over a train is between 35 m/s and 67 m/s,and such cases happened in draught places of mountain opening and trunk valley; the angle be-tween wind direction and railway is closely related to the thickness of accumulative sand along thelines; roadbed disasters taking the form of side-slope sliding, roadbed sinking and silt turning uptook place in spring when the temperature rapidly rose to 10-15℃ from zero and precipitationcame forth or when the thickness of snow cover on shade slope reached above 20 cm in winter;the disasters taking place in the 1990s were far stronger than those of the 1980s and the order ofhazard intensity along the Xinjiang Line is Urumqi＞Shihezi＞Kuitun＞Liuyuan＞Shanhan＞Hami.  相似文献   

芜湖长江大桥北岸接线工程软基处理     

聂宜斌  程华龙 《安徽地质》2002,12(4):273-277

介绍了芜湖长江大桥北岸接线工程约2.1km软土地基的特征及物理力学性质,采用袋装砂井及砂垫层联合使用的处理方法,技术可行,经济合理,效果良好,提高了地基强度,保证了工程质量,具有施工周期短、施工速度快等优点.  相似文献   

山西运城市城区主要桥梁的震害预测     

董斌  王跃杰 《山西地震》2007,(3):25-26,44

采用经验统计法对山西省运城市的4座主要桥梁进行了震害预测计算,给出了4座桥梁的震害预测结果。认为,4座桥梁的破坏程度不同主要是由于桥主跨长度、桥墩高度、支座形式不同及在计算中采用的系数不同引起的,运城市桥梁的破坏程度较低,在遭遇Ⅷ度地震破坏时,中等以上破坏程度的桥梁占25%。  相似文献   

Limit state model for R.C. bridge joints under seismic loading     

D. Timosidis  S. J. Pantazopoulou 《Bulletin of Earthquake Engineering》2007,5(3):391-423

Most of the available models of monolithic reinforced concrete joints under seismic action focus on estimation of cracking and ultimate shear strengths. Very few studies have been directed towards developing expressions for the associated joint deformations at the milestone response points so as to compose a limit-state model for joints that would be compatible with the emerging framework of deformation based seismic assessment and design methods. This objective is pursued in the present paper with particular emphasis on monolithic bridge joints. Deformation capacity at yielding and failure of joints is derived by establishing equilibrium and geometric compatibility of smeared stresses and strains, and satisfying material constitutive relationships. Expressions and model parameters are calibrated with the database of published bridge joint tests assembled from International literature, using statistical evaluation. From the mean values of the design parameters simplified equations for shear strength and ultimate shear strain of bridge joints are proposed.  相似文献   

东海陆架盆地西南部中生代地层的发现   总被引：14，自引：1，他引：13  

王可德  王建平  徐国庆 《地层学杂志》2000,24(2):129-131

东海陆架盆地福州凹陷的中生代地层发育较全 ,分布较广泛 ,而且夹有滨海相地层 ,但曾解释为第三纪地层。根据岩性及孢粉 ( Cyathidites- K lukisporites- Dictyophyllidites,Classopollisannulatus- Schizaeoisporites- Exesipol-lenites tumulus)组合 ,介形类 ( Eucypris?sp.,Metacypris sp.)形态的分析对比 ,可与我国东部、尤其是浙闽等地的同年代地层相比拟。结合同位素绝对年龄测定数据、地震反射界面性质和倾角测井等项资料 ,自下而上建立福州组、渔山组和闽江组 ,依次划归下—中侏罗统 ,上侏罗统—下白垩统和上白垩统。  相似文献   

苏北东海地区片麻岩的Nd—Sr同位素定年及其地质意义   总被引：2，自引：1，他引：1  

樊金涛  李金玉 《江苏地质》2000,24(4):193-199

苏北驼峰、牛山片麻岩的原岩是造山后拉张环境下形成的碱性花岗岩。其全岩Rb -Sr等时线法地质年龄为(80 4 8± 0 39)Ma、(797 7± 1 5 )Ma ,此值代表原岩的形成年龄 ,表明苏胶造山带于新元古代中期 (距今 80 0Ma± )已开始向裂解转化。由此推断碰撞造山运动应发生于新元古代早期 (距今 10 0 0Ma～ 90 0Ma)。其时代可与北美格林威尔造山带相当 ,应是Rodinia超大陆汇聚和裂解的组成部分。此外 ,其Nd模式年龄为 186 9Ma～ 1915Ma、1417Ma～ 144 0Ma ,揭示物质来源于前中元古代地壳重熔岩浆与上地幔物质的不同比例混合。  相似文献