Full-scale model testing on a ballastless high-speed railway under simulated train moving loads

Model testing in laboratory, as an effective alternative to field measurement, provides valuable data to understand railway׳s dynamic behaviors under train moving loads. This paper presents comprehensive experimental results on track vibration and soil response of a ballastless high-speed railway from a full-scale model testing with simulated train moving loads at various speeds. A portion of a realistic ballastless railway comprising slab track, roadbed, subgrade, and subsoil was constructed in a larger steel box. A computer-controlled sequential loading system was developed to generate equivalent vertical loadings at the track structure for simulating the dynamic excitations due to train׳s movements. Comparisons with the field measurements show that the proposed model testing can accurately reproduce dynamic behaviors of the track structure and underlying soils under train moving loads. The attenuation characteristics of dynamic soil stresses in a ballastless slab track is found to have distinct differences from that in a ballasted track. The model testing results provide better understanding of the influence of dynamic soil–structure interaction and train speed on the response of track structure and soils.     

A study on low strain integrity testing of platform-pile system using staggered grid finite difference method

To study the three-dimensional characteristics of wave propagation in platform-pile system, a three-dimensional computation model for transient vibration of platform-pile-soil system is established. Based on initial and boundary conditions, the numerical solution of this model is obtained. A MATLAB program is compiled through using staggered grid finite difference method. The dynamic response of the integrate pile in platform-pile-soil system is got under vertical impact force, and the reliability and feasibility of the numerical simulation are corroborated by comparing calculation result with measured data of low strain integrity testing of platform-pile system. The optimal sensor location at platform top is studied. The results show the position distancing the pile center 0.5R~0.6R (R is pile radius) is the optimal sensor location, which the line between sensor location and pile center parallels the short side. It plays a certain role in reducing three-dimensional interference through increasing shear wave velocity of surrounding soil and appropriately increasing the ratio of characteristic wavelength to pile radius. In addition, contact area has less influence on low strain integrity testing of platform-pile system.     

The numerical and empirical evaluation of chimneys considering soil structure interaction and high-temperature effects

During the past strong ground motions, chimneys constructed according to international standards are representative of similar structures at industrial areas throughout the world, including those collapsed or moderately damaged in earthquake-prone regions. This is due to the specialty of structural characteristics and the special loads acting on the structure such as earthquakes, wind and differences in the level of temperature, etc. In this context, the researchers and designers should focus on the dynamic behavior of chimneys especially under high temperature and seismic effects. For this purpose, the main focus of this study is to evaluate the dynamic response of a chimney under the above-mentioned effects considering soil-structure interaction (SSI). A 52 m steel chimney in Yeşilyurt township of Samsun City in Turkey was studied. The in-situ model testing and numerical models were compared. Before the commissioning of the chimney, a series of tests was realized to define its dynamic characteristics in case of no-heat and after the fabric got to work, the same tests were repeated for the same sensor locations to understand the heat effect on the dynamic response of the chimney. The ambient vibration tests are proven to be fast and practical procedures to identify the dynamic characteristics of those structures. The dynamic testing of the towers promises a widespread use, as the identification of seismic vulnerability of such structures becomes increasingly important. The data presented in this study are considered to be useful for the researchers and engineers, for whom the temperature and SSI effects on steel chimneys are a concern. Using the modal analysis techniques, presented finite element simulation for the soil/pile foundation-chimney interaction system is verified. The results of modal analyses using numerical solutions are shown to have acceptable accuracy compared with results obtained by in-situ test. The present study also aims to provide designers with material examples about the influence of these on the seismic performance of steel chimneys by means of reflecting the changes in the dynamic behavior.     

三种红层岩石常规三轴压缩下的强度与变形特性研究

利用MTS815Teststar程控伺服岩石力学试验系统研究了川东地区一红层边坡中的砂岩、粉砂岩和泥岩围压为03MPa的应力-应变全过程曲线,建立了峰值强度、峰值强度前弹性模量以及峰值强度后的弹性模量和围压的关系。将低围压下红层的全应力-应变曲线概化成5个阶段,分别为压密段、弹性段、屈服段、应变软化段和塑性流动阶段。试验结果得出,红层弹性模量随围压的增加而提高且变化明显,砂岩和粉砂岩在此围压内为脆性破坏,泥岩为塑性破坏的规律。     

广域差分GPS系统PNP-20的接收机及配套软件的研制与应用

论述了局域差分GPS技术受到的限制和广域差分GPS的原理及技术特点,介绍了PNP20广域差分系统 工作原理,并详细叙述其主要的软、硬件的特点和各种功能,分析了该系统的各种检测数据,最后对这套系统的 应用前景和主要优、缺点进行了评述。     

ICT切片重构模型的剖切及应用

在ICT切片重构模型的可视化中,为了分析重构模型的任意截面形状,并且观察该截面的内部结构,需要对重构模型进行剖切.本文针对剖切提出一种简单方法,该方法利用剖切面对重构模型所在的立方体图像空间进行剖切,生成交点集合,然后将空间剖切平面映射到二维图像平面上,最后计算空间剖切平面图像的灰度值,得到剖面图像.通过剖面图像,可以直观地看到内部结构形状,为后续无损检测奠定基础.     

Pseudocycnus appendiculatus Heller, 1868 (copepoda,dichelesthiidae) in New Zealand waters

Pseudocycnus appendiculatus Heller is described and recorded, for the first time from New Zealand, on Thunnus alalunga (Bonnaterre, 1788). Pseudocycnus spinosus Pearse, 1951 and P. thynnus Brandes, 1955 are thought to be synonyms of P. appendiculatus. Other species previously placed in the genus are discussed and the action of Yamaguti (1963) in removing them to other genera supported. It is suggested that the family Pseudocycnidae Yamaguti, 1963 cannot be differentiated from the family Dichelesthiidae Bassett‐Smith, 1898.     

基于探地雷达的混凝土无损检测反演成像方法

本文针对水利水电工程中的混凝土构件无损探测问题,提出了一种新的反演成像方法.传统方法主要依赖人工经验观察偏移探测数据,精度无法保证.这种方法以Maxwell方程的TM问题为数学模型,在混凝土的表面放置发射源与接收器,根据探地雷达的接收数据,采用同伦优化方法结合收敛速度较快的阻尼高斯牛顿方法作为反演算法,其成像结果更具定量化和可视性.该成像方法克服了传统雷达剖面图只能近似地反映混凝土中埋藏物及缺陷的深度、大小等缺点,不仅能够探测混凝土内部异物的位置,而且能够比较准确地确定异物的大小及属性.通过计算机模拟以及对实际资料的处理,验证了该反演成像结果直观、可靠、具有一定的应用价值.     

多元热流体热采技术在海上探井测试中适应性研究

稠油黏度高,流动性差,常规测试难以正确评价储层的真实产能。随着多元热流体热采技术在海上油田生产平台的成功应用,提出了在探井测试中应用多元热流体热采技术。通过对支撑平台的适应性分析研究,运用数值模拟方法预测多元热流体热采测试的开采效果,并对相应的井口、供给方式等进行了优化研究。通过现场实施,多元热流体热采测试的日产油量可达常规冷采测试产油量的2倍以上,实际效果与数值模拟的结果基本相当。该技术的应用更能准确反映油田的真实产能,为海上稠油油田的探井测试提供了一个新方法。