Clear water scour around a finite array of cylinders     

《Applied Ocean Research》2017

This experimental study presents clear-water scour and deposition patterns around hexagonal arrays of circular cylinders in steady flow conditions. Understanding the scour processes around such configurations could facilitate the design of several hydraulic and marine engineering structures, such as bridge piers and piles. The flow alteration caused by the examined porous obstacles depends on the solid volume fraction of the obstacles and on the angle of attack of the incoming flow, due to the limited number of cylinders constituting the array. Flume experiments with erodible bed were carried out for four array densities (solid volume fractions: 0.14, 0.20, 0.32 and 0.56) under three different orientations (regular, angled and staggered configurations). The scour/deposition characteristics were obtained by means of laser scanner and the results were compared to solid cylinders of equal circumambient diameter. Different angles of attack of the incoming flow lead to different blockage ratios, which have direct impact on the scour characteristics and deposition patterns. The arrays with the higher solid volume fraction generated scour/deposition patterns similar to solid cylinder, while in the arrays with the lower solid volume fractions, local scour around the individual small cylinders became evident. Finally, considering that the load bearing capacity of a pier basically depends on the area of its cross-section, a comparison of the maximum induced scour depth and volume by the cylinder arrays and the solid cylinder with equal solid cross-sectional area is presented, in order to introduce an alternative pier configuration that induces less scour. The results showed that the array of cylinders could generate 27% less scour volume and 22% less scour depth compared to its single solid cylinder counterpart.  相似文献   

Finite element analysis of structure-borne vibration from high-speed train   总被引：5，自引：0，他引：5  

S.H. Ju   《Soil Dynamics and Earthquake Engineering》2007,27(3):259-273

Finite element analyses were used to investigate the behavior of the building vibration induced by high-speed trains moving on bridges. The model includes the bridge, nearby building, soil and train. Finite element results indicate that trainload frequencies are more important than the natural frequencies of bridges and trains for building vibrations. If the building natural frequencies approach to the trainload frequencies, which equal an integer times the train speed over the compartment length, the resonance occurs and the building vibration will be large. Moreover, the vibration shape is similar to the mode shape of the resonance building frequency. To isolate the building vibration induced by moving trains, this paper investigates three common types of foundations, which include the extension of retaining walls, pile foundation and soil improvement around the building. Soil improvement around the building is the best way to reduce the building vibration both in horizontal and vertical directions.  相似文献   

基于高铁震源简化桥墩模型激发地震波的数值模拟          下载免费PDF全文

王之洋  李幼铭  白文磊 《地球物理学报》1954,63(12):4473-4484

高铁列车运行过程中绝大部分时间都是行驶在高架桥上的,高铁列车经过桥梁时,通过与大地耦合的桥墩激发地震波发震过程和平地不完全一样.本文探索高铁列车行驶经过高架桥桥墩,通过桥墩对地下介质激发地震波的机理及过程.为了便于理论分析,文中将高铁列车简化为在高架桥上沿一个方向运动的移动线源,通过每节车厢前后组轮对,对每一个桥墩施加力的作用,而桥墩插入地面几十米深至围岩,与表层土壤和深层围岩双重耦合,由此给出高铁列车通过桥墩激发地震波的震源时间函数.同时,基于广义连续介质力学框架下的修正偶应力理论,推导包含介质特征尺度的弹性波动方程,并应用此弹性波动方程以及构建的高铁震源时间函数,采用优化的交错网格有限差分算法,实现数值模拟,将合成的地震记录与实际地震记录对比分析,其结论将为进一步的基于高铁震源的成像和反演研究提供理论依据.  相似文献   

港珠澳大桥西人工岛桥结合段波浪演变数值模拟     

李岩汀  刘清君  闫禹  王登婷  琚烈红 《海洋工程》2022,40(4):18-25

近年来海洋极端天气频发,港珠澳大桥西人工岛地处外海,与其相连接的桥梁非通航跨的桥面高程较低,容易受到海浪侵袭,威胁到岛桥功能的正常发挥和结构自身安全。针对西人工岛桥结合部周围的复杂地形条件,采用OpenFOAM^®开源程序,分别对S、SSW和SW三个方向的极端波浪进行了数值模拟。通过数值计算结果与物理模型试验测量值的比较验证了的模型的准确性。分析了不同方向入射波的波高和沿岛体斜坡爬高的变化规律。随着波浪入射角的增大,人工岛南侧斜坡的波浪爬高呈逐渐减小,但在岛体西端靠近桥梁的位置处,波浪爬高逐渐增大;同时也反映了越浪和桥面上水风险的大小。研究旨在为实际工程的管理和设计提供参考。  相似文献   

中国东北发现似海德堡人头颅化石     

季强  季燕南  王旭日 《江苏地质》2018,42(3):349-350

科学界普遍认为海德堡人是现代人、尼安德特人以及神秘的"杰尼索娃人"的共同祖先。就在海德堡人发现之后25年,即1933年,中国东北哈尔滨的一位农民被日本军队强征去当劳工,在修建东江桥时发现了1件非常奇怪的人头化石,该化石显得十分粗壮,而且眉骨特别厚。这位农民虽然对海德堡人一无所知,但意识到这件人头化石可能非常珍贵,没有将其交给日本兵,而是偷偷地带回家,包裹好后扔进了自家的水井中,连夜用土将水井封埋。2017年,他的孙子在桂林遇见了季强并讲述了此事,经劝说,将这件人头化石捐献给了河北地质大学,永久性收藏于该校的地球科学博物馆。这件人头化石十分完整,许多形态特征与欧洲发现的海德堡人非常相似。目前,季强正在组建研究团队,对这件珍稀的古人类头颅化石开展研究。研究成果有望改变人们对人类发展历史的认识。  相似文献