富水砂卵石地层地铁联络横通道人工冻结数值分析

人工地层冻结法作为一种常用的土层加固方法,被广泛应用于煤矿、地铁等地下结构工程中。成都地区的砂卵石地层含水量丰富,渗透系数大,实施冻结法难度更大。以成都地铁10号线某隧道区间为工程依托,研究采用人工冻结法在砂卵石地层中修建联络横通道的问题。对冻结工程进行现场监测,根据冻结管实际布置形式建立考虑冰水相变的非线性三维弹塑性热—力耦合数值模型,通过现场监测和数值模拟两种手段对积极冻结期温度场和位移场的发展及分布规律进行研究。结果表明：数值模拟结果与现场监测数据吻合较好,建立的数值模型比较可靠;冻结壁交圈时间是冻胀变形快速增长的临界时间点,交圈时间约为25 d;冻结43.7 d时冻结壁厚度达到2 m,在37.8 d时冻结壁内平均温度达到-10 ℃,满足后续开挖施工要求。     

大跨度连续钢桁架拱桥半悬臂拼装临时墩合理标高计算

当大跨度连续钢桁架拱桥采用支架法施工时,其临时支墩标高的合理设定对大桥的拼装线形和安全顺利拼装具有重要影响。本文结合钢桁梁桥的制造线形和架设过程中的钢梁线形变化,较系统地研究了临时墩的标高计算,推导了实用的计算公式,并将该法应用于某大跨度钢桁梁柔性拱组合结构桥梁,由现场拼装和拆除结果表明本文考虑预留50mm的设置方法,能更方便临时墩拆除,同时验证了本文方法的合理性和可靠性,从而为类似桥梁施工计算提供借鉴。     

悬索桥上部结构施工中牵引系统转换技术

针对泰州长江公路大桥悬索桥主缆索股数量多、跨数多、牵引距离长的特点,深入介绍了该工程上部结构施工中牵引系统转换的施工方法,即采用单线往复式牵引系统架设猫道、双线往复式连续牵引系统架设主缆索股,.其中包括过渡索架设,牵引索架设,上、下游侧猫道架设单线往复式牵引系统的形成,索股架设双线往复牵引系统施工技术.事实表明,采用该牵引系统,施工速度快,牵引过程中索股形状保持较好,有效地控制了索股乱丝、呼拉圈、扭转等现象的发生.     

潜艇蓄电池舱有害气体超标问题探讨

潜艇上蓄电池充放电、电解水制氧装置泄露以及放射性等引起的水分解,都会产生部分氢气、锑化氢、砷化氢等有毒有害气体。针对潜艇蓄电池舱的有毒有害气体超标现状,根据现有空气净化装置的技术原理,分析有害气体超标的原因,并提出相应的改进建议,以保障潜艇的战斗力、生存能力、艇员健康;并为潜艇蓄电池舱空气净化装置的设计改进提供参考依据。     

陆上特大型沉井施工技术

泰州大桥主桥采用主跨2×1080m三塔两跨两锚碇悬索桥,其中南、北锚碇基础为特大型沉井,矩形平面尺寸为67.9m×52.0m,高度分别为41m,57m。针对锚碇基础覆盖层深厚、基础尺寸巨大、沉井下沉深度深等特点,通过施工技术的攻关,顺利完成了砂桩复合地基处理、沉井制作和拼装、钢壳沉井混凝土填充、混凝土沉井接高施工、水力机械冲吸式排水下沉和空气吸泥机吸泥下沉等多项施工工序,为今后陆上特大型沉井施工提供了借鉴。文章简要介绍了南、北锚碇陆上特大型沉井的施工技术。     

Elevated temperature compressive slow strain rate properties of several directionally solidified NiAl–(Nb,Mo) alloys

Three NiAl-based alloys containing 3Nb–10Mo, 5Nb–10Mo or 13.6Nb–18Mo (at%) were directionally solidified to develop three dimensional Mo-based dendrite networks. Examination of the alloys indicated that the desired chemistry was achieved for the 3Nb–10Mo and 5Nb–10Mo versions but the composition of the highly alloyed ingot was NiAl–14.6Nb–13.2Mo. The as-grown structure for all three materials consisted of three major phases: essentially unalloyed B2 crystal structure NiAl, Laves NiAlNb phase alloyed with ∼8.5 Mo, and a bcc metallic Mo solid solution containing 27Nb–7Ni–7Al. Compressive properties were measured between 1200 to 1400 K in air under constant velocity and constant load creep conditions with strain rates ranging from ∼10⁻⁴ to ∼10⁻⁸ s⁻¹. The flow strengths of the two alloys with 10Mo were nearly identical and much weaker than those for NiAl–14.6Nb–13.2Mo under all conditions. Comparison the properties of this latter alloy with other directionally solidified NiAl-based eutectics revealed that it was the strongest material under lower temperature/fast deformation conditions, but this advantage was lost at higher temperatures and/or slower strain rates.     

Coagulation and precipitation of a mechanical pulping effluent—I. Removal of carbon,colour and turbidity

This study examined the effects of metal coagulant concentration, effluent dilution and pH on the removal of total carbon, colour and turbidity from a combined bleached chemithermomechanical/thermomechanical (BCTMP/TMP) effluent. Both chloride and sulphate salts of iron and aluminum were effective in treating the mechanical pulping effluent in batch jar screening tests. pH had a pronounced affect on precipitation. In terms of minimizing the total carbon (TC), colour and turbidity levels, the optimum adjusted pH ranges were: 4.0–6.5 for ferric chloride, above 7.4 for ferrous sulphate, 5.0–6.0 for aluminum chloride and 5.8 to 6.8 for aluminum sulphate. Removal of TC, colour and turbidity of up to 88, 90 and 98%, respectively, were observed. The precipitation yielded a supernatant which was virtually clear and colourless.     

Cone bit bearing seal failure analysis based on the finite element analysis

Failure analysis of cone bit bearing seals is important in reducing production cost and preventing in-service component failure. However, a generally accepted criterion for their failure has not yet been established because of complexities in both their material properties and the environment. In this study, a two-dimensional axisymmetric finite element analysis (FEA) numerical model was established. FEA software was developed based on the Mooney–Rivlin constitutive model of the rubber material, and the penalty function contact algorithm. The distributions of stress, strain and contact pressure were analyzed to establish their effect on failure. The locations and causes of the failure and preventive measures were determined by comparison with an actual failure case. It was found that stress concentration and uneven pressure distribution occur at the seal. Rubber rings are highly and unequally compressed. Metal ring structure mainly determines sealing performance. To reduce the occurrence of failure, the structure must be improved by: designing an appropriate angle-tapered metal ring end face structure instead of a plane to change the trend in pressure distribution, increasing the contact area of the metal ring end face to reduce contact pressure and make the contact pressure distribution more uniform to reduce sealing surface wear, reducing the radial thickness to reduce the compression of the rubber ring, and improving back support structures to reduce the stress concentration. Results from the study can prevent and minimize risk for future failures to increase bit life and reduce drilling costs.