充气胶囊堵头浮运法在钢管桩水上输送施工中的应用

为了降低工程成本,在桩基施工中,结合工程实际情况采取了钢管桩现场拼接、充气胶囊堵头拖带浮运的方法。在分析钢管浮运可行性的基础上,系统介绍了浮运时堵头的加工、安装方法,介绍拖带浮运模式,并对其优势进行分析。施工中采用此运输模式取得了较好的效果。     

高速公路除雪技术探讨

及时地清除冰雪,保障冬季高速公路的安全、畅通,是高速公路养护部门的一项非常重要的工作。从提高除雪效果、降低环境污染、减少行车事故损失的角度,论述了采用新型除雪剂的意义,结合使用经验介绍了新型除雪剂的性能、喷洒方法和应用效果,并对经济效益和社会效益进行了分析。     

A comparative analysis of the fluid-structure interaction method and the constant added mass method for ice-structure collisions

The constant added mass (CAM) method and the fluid-structure interaction (FSI) method are widely used to simulate ship-ship and ship-ice collisions. In the CAM method, the hydrodynamic effect of the surrounding water is treated as a constant added mass, whereas in the FSI method the surrounding fluid flow is explicitly modelled. The objective of the paper is to compare the two methods and to explain the causes of the differences in the results. We considered collision between a freshwater ice mass and a floating steel structure. For both methods, the numerical simulations were performed with the LS-DYNA software. The behaviour of the ice mass was modelled using an elliptic yield criterion and a strain-based pressure-dependent failure criterion. To ensure realistic ice behaviour, the ice model was calibrated using general trends found in laboratory and in-situ indentation tests with focus on the laboratory-grown ice and the fluid model in the LS-DYNA was verified by comparing the added mass coefficients for a spherical body and a rectangular block with the corresponding WADAM results. To validate and benchmark the numerical simulations, experimental data on ice-structure interactions in water were used, including the acceleration of the floater wall measured with the dynamic motion unit (DMU), the relative velocity between the ice mass and the floater before the impact and some images extracted from video recording of the test. The comparisons indicated that the FSI method yields better results for the motion of the floater, i.e., the acceleration of the floater wall caused by the ice mass’s impact and the relative velocity were in reasonably good agreement with experimental measurements. It was also found that the CAM method was faster but predicted a higher peak contact force and more dissipated energy in the ice mass than in the FSI method.     

江西省高速公路冰雪灾害应急对策

为制定江西省高速公路冰雪灾害应急对策,基于高速公路冰雪灾害特点,系统阐述了高速公路冰雪管理目标,并提出了防治冰雪处治策略。     

雪灾对接触网覆冰及其影响的探讨

2008年初的严重冻雨气候使得接触网和电力架空线路覆冰严重,给正常运行造成极大困难,个别地方出现了独立锚柱拉断的现象.如何提高接触网抗击雪灾能力,确保电气化铁道在恶劣气候条件下正常运行是设计人员今后必须面对的问题.     

极端冰雪条件下边坡稳定性分析

极端冰雪天气可能造成边坡的稳定性下降。结合算例,分析了极端冰雪天气发生时,各个工况下边坡的稳定性。首先研究了气温开始下降时,边坡内部温度分布规律,并考虑冻融界面的强度损伤,计算了表面土体冻结时边坡的安全系数。接着,针对边坡融化过程,分析了坡面土体部分融化及全部融化后边坡的应力状态,孔隙水压力分布及安全系数。结果表明,边坡开始冻结和融化时,都能造成边坡的稳定性下降,但其发生原因和机理略有不同。     

极区船舶冰带构件极限载荷评估

弹性设计准则下,极区船舶通常需要过度的结构加强以确保航行安全。若采用极限载荷设计准则,考虑结构的塑性承载能力,利用一部分屈服点之后的强度储备,则能大大减轻结构重量。本文以中国船舶及海洋工程设计研究院（MARIC）研发的某20000吨级PC5级极地多用途运输船为目标船型,基于IACS URI规范关于冰载荷及相应计算工况的要求,进行了非线性有限元分析。基于计算结果,工程计算推荐100mm×100mm的网格尺寸,材料定义推荐使用理想弹塑性材料。通过对比不同极限载荷准则,认为两倍弹性斜率准则相对更适用于船舶构件。研究成果可为极区船舶结构的设计与强度验证提供参考。     

N2O／H2富燃火炬式点火器研究

本文介绍N2O/H2富燃火炬式点火器的初步研究情况,包括结构设计和试验结果。该点火器具有结构独特、设计灵活、启动快速、点火能量高而且无毒无污染的特点,试验表明:点火器可在较宽的工况范围内可靠地重复生成稳定的点火火炬。     

Winter–spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean

An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom (r values ≥ 0.74, p < 0.01). These relationships suggest that algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.     

船舶管道空气塞的形成与消除措施

船舶管道在气囊作用下往往形成空气塞,阻碍燃油等液体的流通,对柴油机的正常工作带来不利影响。作者根据长期工作经验,分析了空气塞的成因,提出了消除空气塞的若干措施。