双台风相互作用的数值研究   总被引：6，自引：3，他引：6  

炎利军  田永祥  黄先香 《热带气象学报》2004,20(2):167-175

无基本气流的情况下，应用无辐散正压模式对初始呈西北-东南等方位的双台风相互作用进行数值研究，探讨了非对称理论在双台风相互作用中的应用。试验结果表明：双台风的运动特征能够运用非对称理论进行解释；非对称流函数场中，通风气流分别控制着双台风的移动，同时双台风的移动对其对应的非对称结构具有反作用。试验还表明，台风非对称结构内小尺度涡旋的强度及其绕台风中心逆时针旋转的快慢与台风路径的摆动关系密切：模式可以模拟出台风逆时针打转、“蛇形”摆动等异常移动路径。  相似文献   

基于双剪强度理论土拱效应的基坑支护桩间距分析   总被引：1，自引：1，他引：0       下载免费PDF全文

陈秋南  周亚军  马晓朋  李腾飞  张主华 《水文地质工程地质》2012,39(4):38-42

在分析桩间土拱效应形成机理的基础上,以圆形支护桩为研究对象,利用合理拱轴线和起拱点土体破坏面等几何特征,建立抛物线土拱分析模型,通过桩间土拱静力平衡条件和双剪强度理论来确定桩间距,推导出圆形支护桩的合理桩间距计算公式,桩间净距随桩后土体粘聚力或内摩擦角的增大而增大,却随着桩后主动土压力或中主应力参数m的增大而减小,且随着参数m的增大,桩后主动土压力是逐渐增大的.最后通过工程实例计算支护桩间距,并与有限元法和规范法计算结果进行比较,验证了基于双剪强度理论土拱效应的基坑支护桩间距计算结果的合理性和安全性.  相似文献   

论石英双晶的复杂性     

赵珊茸  王勤燕  肖平  许娅玲 《地质科技情报》2012,(5):8-14

石英双晶的复杂性远远超出了人们的想象。首先介绍了石英的11种双晶律,然后介绍测试鉴定石英双晶律的各种方法及存在的局限性,综述了近年来石英双晶与温压条件关系、晶格结构匹配理论方面的研究成果,最后结合我们近期用EBSD对岩石中石英双晶的观察、测试结果,指出存在的问题及今后的研究方向。  相似文献   

双线盾构施工时邻近地下管线安全性判别     

魏纲  林雄  金睿  丁智 《岩土力学》2018,39(1):181-190

研究双线盾构隧道施工时邻近地下管线的安全性判别方法。基于Winker弹性地基梁模型,考虑管土效应,建立连续管线应变与地表沉降关系式;假设管线位移与土体位移相同,建立非连续管线接头转角与地表沉降关系式;同时考虑管线老化,定义与时间相关的折减系数,建立一种通过测量地表沉降值即可判断管线安全性的方法。当管线应变或接头转角为安全允许值时,对应的地表沉降即为控制值。施工时,若地表沉降超过该值,则表明管线存在危险。该方法将不易监测的管线状态转化为可见的地表沉降。研究结果表明：预测值与实测值的对比说明了所提方法具有可靠性;双线隧道水平间距L值对地表沉降控制值的影响非常大。当L较小时,最大值出现在两隧道中轴线处;当L较大时,最大值出现在隧道轴线上方附近处;随着L的增大,最大控制值逐渐减小。  相似文献   

Reliability assessment of ultimate limit state of twin caverns     

Wengang Zhang 《Geomechanics and Geoengineering》2017,12(1):48-59

Construction of a cavern in close proximity to an existing cavern modifies the state of stresses and movements in a zone around the existing cavern, as some degree of interaction between these two caverns generally takes place. This study investigates the interaction of two parallel caverns and the influence of such interaction on stress-induced global stability in terms of a global factor of safety. A series of finite difference analyses were performed to derive the global factor of safety of a system of two parallel and adjacent caverns. A mathematical response surface model was then built using the multivariate adaptive regression splines (MARS) approach and a series of charts based on this surrogate model were developed to relate the global factor of safety to the critical parameters. The built MARS model is of high accuracy and is simple to interpret and can be used to perform probabilistic assessment of ultimate limit state of twin caverns.  相似文献   

Twin lintel belt in steel for seismic strengthening of brick masonry buildings   总被引：2，自引：1，他引：1  

C.V.R.Murty JayantaDutta S.K.Agrawal 《地震工程与工程振动(英文版)》2004,3(2):215-222

A single-room, single-storey full-scale brick masonry building with precast RC roofing system was tested thric eunder displacement controlled lateral cyclic loading, to assess the effectiveness of the basic repair and seismic strengthening techniques. Initially, the virgin building specimen was loaded laterally to failure, In the second stage, the damaged building was repaired by stitching across the cracks, and tested under the same lateral loading. In the third stage, the twice-damaged structure was repaired once more by stitching and strengthened by twin lintel belt in steel and vertical corner reinforcement,and re-tested. The building strengthened by twin lintel belt in steel showed about 28% higher strength under lateral loading than the virgin building.  相似文献   

基于准连续介质方法模拟纳米多晶体Ni中裂纹的扩展   总被引：1，自引：0，他引：1  

邵宇飞  王绍青 《海洋学报》2010,32(10):7258-7265

通过准连续介质方法模拟了纳米多晶体Ni中裂纹的扩展过程.模拟结果显示:裂纹尖端的应力场可以导致晶界分解、层错和变形孪晶的形成等塑性形变;在距离裂纹尖端越远的位置,变形孪晶越少;在裂纹尖端附近相同距离处,层错要远多于变形孪晶.这反映了局部应力的变化以及广义平面层错能对变形孪晶的影响.计算了裂纹尖端附近区域原子级局部静水应力的分布.计算结果表明:裂纹前端晶界处容易产生细微空洞,这些空洞附近为张应力集中区,并可能促使裂纹沿着晶界扩展.模拟结果定性地反映了纳米多晶体Ni中的裂纹扩展过程,并与相关实验结果符合得很好  相似文献   

High Pressure Response of Rutile Polymorphs and Its Significance for Indicating the Subduction Depth of Continental Crust     

MENG Dawei  WU Xiuling  FAN Xiaoyu  ZHANG Zhengjie  CHEN Hong  MENG Xin  ZHENG Jianping 《《地质学报》英文版》2008,82(2):371-376

α-PbO2-type TiO2 （TiO2-Ⅱ） is an important index mineral for ultrahigh-pressure metamorphism. After the discovery of a natural high-pressure phase of titanium oxide with α-PbO2- structure in omphacite from coesite-bearing eclogite at Shima in the Dabie Mountains, China, a nanoscale （〈2 nm） α-PbO2-type TiO2 has been identified through electron diffraction and high-resolution transmission electron microscopy in coesite-bearing jadeite quartzite at Shuanghe in the Dabie Mountains. The crystal structure is orthorhombic with lattice parameters a = 4.58×10-1 nm, b = 5.42×10-1 nm, c = 4.96×10-1 nm and space group Pbcn. The analysis results reveal that ruffle {011}R twin interface is a basic structural unit of α-PbO2-type TiO2. Nucleation of α-PbO2-type TiO2 lamellae is caused by the displacement of one half of the titanium cations within the {011}R twin slab. This displacement reduces the Ti-O-Ti distance and is favored by high pressure. The identification of α- PbO2-type TiO2 in coesite-bearing jadeite quartzite from Shuanghe, Dabie Mountains, provides a new and powerful evidence of ultrahigh-pressure metamorphism at 4--7 GPa, 850℃-900℃, and implies a burial of continental crustal rocks to 130-200 kilometers depth or deeper. The α-PbO2-type TiO2 may be a useful indicator of the pressure and temperature in the diamond stability field.  相似文献   

面向数字孪生城市的自然场景构造方法     

贺彪  郭仁忠  张琛  马丁  王伟玺  洪武扬  陈业滨 《测绘通报》2022,(7):87-92

自然场景内要素种类繁多、结构复杂,在数字孪生城市中还原自然场景具有挑战性。数字孪生城市中的自然场景不仅要使用高逼真的三维模型,还要能表现自然环境中要素的生长过程、结构组成和分布规律,同时满足不同尺度下的场景变换,构造出既符合空间分布规律又具有沉浸式体验的场景。本文从自然场景构造过程的角度分析了场景构造的4个关键技术问题,回顾了目前场景要素建模和场景构造方法,并提出了一种面向数字孪生城市的自然场景构造技术框架。  相似文献   

Experimental study on the performance of twin plate breakwater     

郭传胜  张宁川  李艳阳  李靖波  房卓  崔成 《中国海洋工程》2011,25(4):645-656

The wave transmission characteristics and wave induced pressures on twin plate breakwater are investigated experimentally in regular and random waves.A total of twenty pressure transducers are fixed on four surfaces of twin plate to measure the wave induced dynamic pressures.The spatial distribution of dynamic wave pressure is given along the surface of the twin plate.The uplift wave force obtained by integrating the hydrodynamic pressure along the structure is presented.Discussed are the influence of different incident wave parameters including the relative plate width B /L,relative wave height /i H a and relative submergence depth s /a on the non-dimensional dynamic wave pressures and total wave forces.From the investigation,it is found that the optimum transmission coefficient,t K occurs around B /L 0.41 ~ 0.43,and the twin plate breakwater is more effective in different water depths.The maximum of pressure ratio decreases from 1.8 to 1.1 when the relative submergence depth of top plate is increased from 0.8to +0.8.  相似文献