超深振捣条件下混凝土墙体模板侧压力的简化计算方法

超深振捣对混凝土成品质量有害无益,研究超深振捣引起模板侧压力增大的规律,可为规避其害提供依据。为此设计4个混凝土墙体试件,实测在浇筑过程中模板侧压力的变化情况。基于振捣液化和液体压力平衡理论,建立了超深振捣情况下混凝土模板侧压力计算模型,推导了计算公式,并与实验数据进行对比验证。研究结果表明,振捣深度是影响混凝土墙体模板侧压力的重要因素,本文提出的计算模型能很好地预测墙体结构超深振捣位置的模板侧压力。     

深度模拟器液压系统仿真研究

介绍了深度模拟器总体结构及工作原理,针对深度模拟器控制系统中PID算法及其相关参数进行了仿真研究。以深度模拟器液压系统为模型,利用AMESim仿真软件工具,对整个液压系统进行了仿真分析并对系统各元器件的参数进行了优化,为深度模拟器的进一步研究提供了理论基础。     

超大型自航抓斗挖泥船作业流程载荷分析

以大型自航抓斗挖泥船为研究对象,建立相应的水动力计算模型。主要研究抓斗挖泥作业不同阶段下船舶运动、锚泊线受力情况以及其随不同环境载荷的变化规律,为船舶安全作业提供依据。研究结果表明,船舶在抓斗旋转和卸料时最为危险,船舶横荡、横摇及各锚泊线张力受其影响很大,实际作业时应尽量保持迎浪状态,进而确保船舶作业安全。     

大型耙吸式挖泥船精挖施工工艺在湄洲湾航道工程中的应用

为解决大型自航耙吸式挖泥船在航道疏浚施工、特别是在跨度较大的深水航道疏浚施工中存在的严重超挖废方问题,依托大型自航耙吸式挖泥船"长鲸6"在湄洲湾30万吨级主航道疏浚施工中采取RTK无验潮、多波速测量和分层定深开挖等技术,对潮位数据、动态分层定深和测量成果等进行分析,对潮位观测站数据与施工船舶RTK无验潮实时数据进行对比纠正,探讨自航耙吸式挖泥船挖深精确控制施工技术及管理措施。     

疏浚监控系统原理及校验方法*

耙吸式挖泥船与绞吸式挖泥船的疏浚监控系统的校验工作与施工生产是密不可分的。为提高挖泥船的疏浚监控系统校验工作的准确性和合理性，对耙吸挖泥船与绞吸挖泥船部分无溯源施工设备原理及校验方法进行分析，如绞刀深度原理及校验方法、耙臂下放深度原理及校验方法；并对部分主要施工设备原理及校验方法进行分析，如密度计原理及校验方法、流速计原理及校验方法。结合实际校验的工作经验，验证施工关键设备校验后调整方法的可行性及校验结果的可靠性，得出提高两种挖泥船校验工作质量和效率的方法，提高了施工准确度和生产效率，使疏浚项目加快顺利完成。     

全海深双球连接耐压舱的结构设计探索

钛合金耐压球壳被广泛地应用于大深度载人潜水器.但是,由于受到材料强度的限制,若采用成熟的Ti-6Al-4VELI来设计3人型的全海深载人舱,其壁厚将超出很多国家的现有制造能力.为了解决这一矛盾,该文提出了一种新的双球连接的方案,并以中国船级社最新的强度标准作为优化约束条件,用有限元分析法对这种结构形式进行了优化设计.最后,对双球结构方案与传统单球方案作了比较.     

铁路路基动态变形模量的数值模拟分析

介绍铁路路基动态变形模量理论计算公式的推导及动态变形模量的测试原理,采用有限元软件模拟动态变形模量的测试过程,分析承载板与土体接触压力、路基动态变形模量的影响因素,并计算动态变形模量的有效测试深度.结果表明:在承载板中心一定范围内,接触压力模拟结果较理论计算值大;土体的动弹性模量对接触压力影响很小,可以忽略;路基动态变形模量测试冲击荷载作用下,土体只发生弹性变形;动态变形模量与土体动弹性模量呈线性关系,路基动态变形模量的模拟结果大于理论计算值;土体的泊松比对动态变形模量影响较小;动态变形模量有效测试深度建议取0.5~0.6 m.     

北京新机场线一期8.8m直径隧道盾构选型研究

依托北京新机场线一期工程07标段,从刀盘类型、刀盘驱动设备、刀具型式、刀具布置、渣土改良系统和同步注浆系统等方面对盾构选型进行研究。通过分析工程特点、总结以往工程经验、理论计算等方法得出结论:在全断面砂卵石地层中,辐条式刀盘适应性更佳;先行刀与刮刀组合的破岩方式以及先行刀的高差设置,有利于盾构掘进开挖土体;渣土改良材料注入口布置应充分考虑地质条件。     

Modeling free-flow speed according to different water depths—From the viewpoint of dynamic hydraulic pressure

In this paper, we propose a method of modeling free flow speed from the viewpoint of hydroplaning. First, the lift forces for different water depths were estimated using Bernoulli’s equation. Compared with the result of the experimental test performed by the Japan Automobile Research Institute, the hydrodynamic pressure coefficient was determined to be 0.03 (tf s²/m⁴). The validation of the predicted lift force is found in another published paper. A very good match is found between the computed values by the proposed numerical model and the data in other published papers. Then, the loss of contact force is considered to evaluate the hydroplaning performance of a tire. To simulate the hydroplaning speed, a tire-sliding model was utilized to obtain the traction and friction forces between the road surface and the tire. The observation data obtained in Japan in 2009 is compared with the physically computed hydroplaning speed, yielding the conclusion that the traction force at the measured desired speed is, on average, 23.4% of the traction force at hydroplaning speed. The analytical model offers a useful tool to quantitatively show that the free flow speed changes as the water depth increase.     

Determination of limiting cavity depths for offshore spudcan foundations in a spatially varying seabed

The importance of accurate prediction of limiting cavity depths during offshore spudcan foundations installation has been variously highlighted in the literature. Nonetheless, most of the previous research is deterministic in nature and confined to homogenous soils. Since offshore clayey soils can be highly spatially variable, there is a practical need to take proper account of the spatial variability in the prediction of limiting cavity depths. In a bid to remedy this situation, large deformation finite element calculations combined with three-dimensional random fields were repeatedly conducted in this study within a Monte-Carlo framework. The continuous penetration of a spudcan initiated from surface was explicitly modeled until a full-localized flow-around mechanism was observed. Spatial variability was found to clearly affect the soil back-flow and thereby the limiting cavity depth, the latter of which takes a range of values that can be approximately modeled as a log-normal distribution. Characteristic limiting cavity depths at various probability levels were ascertained. An algebraic expression was proposed to explicitly predict the characteristic limiting cavity depths in random soils from the fractile. Particular attention was paid to the lower and upper 5% characteristic values, which are likely to be useful for reliability-based design.