深基坑开挖施工中对跨越基坑原水管的信息化监测保护     

陈基炜 《上海国土资源》1999,(1):60-62,5

上海市地铁二号线东昌路车站施工对跨越基坑的Φ１２００ｍｍ上游原水管的信息化监测保护实例,就深基坑开挖施工过程中对原水管一类的重要管线的监测点位布设方法,点位布设原则,监测原则,险情预报以及监测结果的分析与评价进行了总结,并提出了建议。  相似文献   

莫斯科、伊尔库茨克至南极长城站短波衰落特性分析          下载免费PDF全文

张添益  王聚杰  张雪枫 《极地研究》1999,11(2):76-83

为了研究过极区的短波长电路的衰落特性,在南极长城站收测莫斯科、依尔库茨克的短波授时台信号,并给出各频率对应的衰落深度、衰落率、衰落平均持续时间等参数的统计特征和衰落幅度分布曲线。结果表明：（１）在莫斯科、依尔库茨克－南极长城站两条电路上,其电离层短波信道是快衰落信道,信号幅度衰落绝大部分服从瑞利分布,分布特性与频率、时间、距离、位置关系不大;（２）莫斯科－南极长城站电路的衰落深度与频率、时间有关,频率低,其衰落深度大。但依尔库茨克－南极长城站电路的衰落深度与频率、时间无关,说明衰落深度与频率、时间的关系还要受距离、位置等因素的影响。（３）频率越高,衰落率也越高,０４：００～０９：００时段内衰落率高于其他时段。  相似文献   

船舶碰撞中空夹层钢管混凝土导管架平台损伤分析     

商文翰  张纪刚  吴书义  刘菲菲  陈文礼  赵阳 《海洋工程》2023,41(2):22-30

针对船舶与中空夹层钢管混凝土（CFDST）导管架平台碰撞问题,利用ABAQUS/Explicit非线性有限元软件建立中空夹层钢管混凝土导管腿导管架数值模型,对船舶碰撞进行数值模拟,对比分析1 m/s、2 m/s和3 m/s的3种碰撞速度下工况下导管架抗碰撞性能、耗能及损伤。从碰撞力、碰撞区域变形以及导管架能量耗散等方面详细研究中空夹层钢管混凝土导管腿作用下导管架整体的损伤模式和动力响应。结果表明：CFDST导管架在船舶碰撞荷载作用下主要由CFDST导管腿耗能,有效控制了结构整体位移变形,提升了整体刚度,有效发挥平台各构件之间组合耗能,结构抗碰撞能力得到明显提升。  相似文献   

Atmospheric Equilibrium Tide Theory     

张德宇 《海洋通报(英文版)》2004,6(2):28-33

Based on the equilibrium tide theory of the seawater, a model of longperiod variations in air pressure with the lunar motion is derived to advance the climatic tide concept and formulate the climatic tide formula, which provides useful leads for predicting the heavy meteorological catastrophe in Shandong area, even in China. as well as in the whole world.  相似文献   

Morphology,structure and flow phases in soil pipes developing in forested hillslopes underlain by a Quaternary sand–gravel formation,Hokkaido, northern main island in Japan     

Tomomi Terajima  Tomoki Sakamoto  Tomoki Shirai 《水文研究》2000,14(4):713-726

Preferential flow pathways, such as soil pipes, are usually present in the soil of slopes. Subsurface flow through the soil pipes affects the subsurface drainage system and is responsible for sediment removal from slopes. However, a record of the inner structure of soil pipes has rarely been reported for slopes. A fibrescope examination of the morphology and flow phases in soil pipes in hillslopes underlain by a Quaternary sand–gravel formation provided the following information: the main pores of the soil pipes ran mostly parallel with the slope gradient; the cross‐sections of the soil pipes were approximately circular; and occurred on a few occasions; with some triple junctions being present. In addition, both full flow and partly full‐depth conditions occurred simultaneously in the soil pipe. The full flow condition has long been used in hydrological studies to model the pipe flow mechanism. Both the full flow condition and the partly full‐depth condition, however, must be examined closely in order to evaluate the subsurface hydrology in heterogeneous soil and the hydrogeomorphological processes of subsurface hydraulic erosion. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

江苏海岸辐射沙洲地层中大直径钢管桩基础承载性能试验研究     

吴荣辉  叶锦峰  骆光杰  沈晓雷  张强 《海洋工程》2021,39(1):121-132

江苏海岸辐射沙洲是江苏重要的海上风电规划区域,该海域的地层资料和试桩资料极为缺乏。通过钢管桩的现场静荷载试验,对江苏海岸辐射沙洲地层中大直径钢管桩基础承载性能进行研究,以揭示各地层的主要承载性能参数。试桩结果表明,江苏海岸辐射沙洲地层中钢管桩实际的轴向极限承载力明显小于高应变动测结果,只有高应变动测结果的79.09%。总侧摩擦阻力占总承载力的95.61%,而桩端阻力只占总承载力的4.39%。桩内土对管壁的侧摩阻力作用很小,主要是桩外土对管壁的侧摩阻力在发挥作用。辐射沙洲地层中粉土夹粉质黏土的承载性能一般,不适应作为钢管桩的持力层。轴向抗压静载试验得到的极限侧摩阻力高于静力触探的测试结果和API法的计算值。浅部砂层实际的极限水平土体抗力高于API法计算值,在水平荷载作用下上部砂层的p-y曲线具有明显软化效应,土体的软化效应在设计时需进行考虑。  相似文献   

多龄期钢框架时变损伤模型研究   总被引：2，自引：0，他引：2       下载免费PDF全文

郑山锁  张晓辉  黄威曾  赵旭冉  孙乐彬 《地震工程学报》2018,40(3):389-397

对3种不同厚度的钢材标准试件进行酸性大气环境气雾加速腐蚀试验,并对锈蚀后的试件进行单向拉伸试验,得到钢材力学性能随失重率的衰变规律。同时考虑构件截面削弱与材料力学性能降低,建立不同锈蚀程度下的钢框架有限元分析模型,利用非线性静力推覆分析得到锈蚀钢框架结构的整体初始刚度随锈蚀程度增大的退化规律,以表征结构因锈蚀造成的损伤。提出同时反映最大变形效应和累积耗能效应的双参数结构整体地震损伤模型,并在此损伤模型的基础上集合钢材材性试验结果及有限元分析结果,提出适用于锈蚀钢结构的"时变"损伤模型。对比分析以层间位移角及时变损伤模型为性能指标建立的不同龄期钢框架结构的地震易损性曲线,结果表明:随着锈蚀程度的增加,在相同地震动强度下结构超越某一极限状态的失效概率均增大。  相似文献   

基于小比例缩尺模型结构试验的小型钢架反力墙优化设计与力学性能分析     

孙柏涛  姜琪  闫培雷 《震灾防御技术》2018,13(4):869-877

为了降低模型制作加工成本和节约试验空间,开展结构缩尺比例小于1:10的小模型结构抗震试验。目前,国内相关的试验设备较少,本文将参考大型反力墙的结构形式,研究小型钢架反力墙,并对其进行优化设计和力学性能分析,为后续的制作加工提供理论依据。  相似文献   

Transport measurement with a horizontal and a vertical pipe microphone in a mountain stream: taking account of particle saltation          下载免费PDF全文

Daizo Tsutsumi  Masaharu Fujita  Michinobu Nonaka 《地球表面变化过程与地形》2018,43(5):1118-1132

The pipe microphone has been shown to be an effective means for monitoring bedload transport in mountain streams. It is commonly installed perpendicular to the flow direction on a stable river bed, such as that of a check dam. Acoustic pulses caused by bedload collisions with the pipe are detected by a microphone. However, bedload particles saltating over the pipe remain undetected. To overcome this disadvantage, we installed a horizontal as well as a vertical pipe microphone in the Ashi‐arai‐dani supercritical channel located in the Hodaka mountain range, Japan. The vertical pipe was installed on the wall of the channel and the horizontal pipe was installed on the channel bed. The acoustic response of the horizontal pipe is expected to be larger than that of the vertical pipe, because the bedload concentration decreases with increasing height above the bed. However, at high amplifications, the peak pulse value from the vertical pipe is higher than that from the horizontal pipe. We explain this observation as follows: under high bedload discharge conditions, the pulses of the horizontal pipe are saturated but those of the vertical pipe are not. We proposed a ratio (R_hv) between the pulses detected by these sensors, and applied this ratio for calibrating the contemporaneous pulses detected by a microphone located immediately upstream of a bedload slot sampler. Indeed the R_hv‐corrected pulses correlated well with the bedload discharge calculated from the sampler, supporting our explanation. We conclude that bedload monitoring using concomitant vertical and horizontal pipe microphones can be used to calibrate centrally located pipe microphones when the bedload concentration is approximately homogeneous laterally across the width of the channel cross‐section, and thereby represent bedload discharges more accurately than with only a single pipe microphone. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Mechanistic Study and Multi‐Response Optimization of the Electrochemical Treatment of Petroleum Refinery Wastewater          下载免费PDF全文

Chandrakant Thakur  Vimal C. Srivastava  Indra D. Mall  Ajay D. Hiwarkar 《洁净——土壤、空气、水》2018,46(3)

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