桃树坪隧道穿越富水粉细砂地层双导洞超前法施工技术

在建兰渝铁路桃树坪隧道为Ⅰ级铁路双线隧道,施工穿越上第三系富水粉细砂地层。为了解决由于出水量大,岩性软,成岩作用及稳定性差,在隧道开挖过程中,含水粉细砂层软化现象明显,常呈流塑状,无自稳性,造成大断面隧道施工极其困难的问题,结合桃树坪隧道3#斜井正洞围岩特点研究采用了双导洞超前法施工,通过导洞超前降水、先行稳固拱脚,解决了富水粉细砂层大断面隧道开挖困难、初期支护变形严重难以控制的问题。     

大跨度浅埋软弱围岩隧道施工工法比较

针对大跨度浅埋软弱围岩隧道施工问题,分析了双侧壁导坑法和微台阶留核心土法的技术特点和适用条件,双侧壁导坑法施工在控制围岩变形及地面沉降方面优于三台阶法,且产生的围岩塑性区较小,微台阶留核心土法在施工进度、资源利用、造价、工序转化及施工难度方面具有优势。结合工程实例,证实仅在围岩具有自稳能力并且可以机械开挖时,可以优先采用微台阶留核心土法,其它条件下宜采用双侧壁导坑法。     

层次权重决策分析法在浅埋隧道开挖方法选择中的应用

以浅埋公路隧道为研究对象,利用层次权重决策分析法对正台阶环形开挖法、双侧壁导坑法、交叉中隔墙法和中隔墙法等隧道施工工法进行对比分析,得出交叉中隔墙法能很好地控制地表沉降。结合FLAC3D软件,模拟交叉中隔墙法、正台阶环形开挖法施工后地表沉降,通过对比工程实际分析验证层次权重决策分析法。结果表明,层次权重决策分析法是选择开挖方法行之有效的方法,能为浅埋隧道施工方法的选择提供参考。     

江肇高速公路毛毡岭隧道洞口浅埋段施工

江肇高速公路毛毡岭左线隧道肇庆端洞口V级围岩超浅埋且为碎石土与全一强风化泥岩的软弱围岩,针对其实际情况,施工中遵循“早进晚出”的原则提前进洞,减少了隧道施工对烂柯山自然保护区的环境破坏。隧道进洞采用了长管棚、小导管注浆等措施加固岩体,洞内采用双侧壁导坑法施工方法减少了隧道一次性开挖断面,施工中结合监控量测和超前地质预报及时调整支护参数,确保了隧道安全通过超浅埋段,满足了施工工期要求和对自然保护区环境的保护。     

中速三体船型PCC的可行性研究(英文)

In the present paper, a new trimaran Pure Car Carrier (PCC) is proposed and a feasibility study on the ship is carried out. In this study, first, the effective horse power (EHP)/car of the PCC running in still water is predicted. By comparing the predicted EHP/car with that of a conventional mono-hull PCC, it is found that the trimaran PCC is superior to the conventional mono-hull PCC at rather higher speed. As ship speed increases, the reduction of the resistance of the trimaran is bigger. It is also found that at common service speed of PCCs, the EHP/car of a small PCC is lower than that of a conventional PCC. Secondly, the optimal L/B of a main-hull of the trimaran PCC in still water is determined. The optimal L/B of the main-hull varies with ship speed and size because the wave resistance decreases but the frictional resistance increases as L/B of the hull increases. As ship size increases, the optimal L/B of the main-hull of the trimaran PCC decreases.     

Steady streaming of viscous surface layer in waves

An investigation of the drift velocity induced by water waves of a contminated surface layer is carried out. The theoretical analysis is based on a thin boundary layer on the free surface. The results of the analysis reveal that the drift velocity of a viscous layer on the water surface is 7/4 times the Stokes prediction ofc(ak) ² wherec is the wave celerity andak the wave slope. The present experimental investigation confirms the validity of the theoretical prediction for the drift velocity for a lightly contaminated surface layer; however, for a heavily contaminated surface layer, the experimental results exceed the theoretical prediction. An investigation for a heavily contaminated layer is carried out assuming an inextensible surface layer. Thus, in the experiment, vinyl sheets are used to substitute the contaminated layers. By balancing the wave-induced mean thrust force with the mean drag force, the drift velocity is obtained and compared with the experimental results. Based on the theoretical and experimental analyses, formulae for predicting the drift velocities for laminar and turbulent flow conditions are proposed.     

棘轮补偿连接架卡滞对补偿绳偏移的分析研究

在六沾铁路接触网验收中,存在棘轮补偿连接架卡滞的问题,通过对连接架卡滞造成补偿绳偏移的分析研究,得出两侧小轮补偿绳在平面内对大轮的间距不均衡,其田野侧小轮补偿绳向大轮轮齿方向偏移,在运行中造成补偿绳与大轮轮齿的安全距离不足,容易产生摩擦而形成安全隐患,要在施工中重视并避免连接架卡滞的缺陷,确保棘轮补偿装置的运行安全。     

双侧壁导坑施工对偏压隧道初期支护变形的影响

随着交通基础设施建设的迅速发展,采用双侧壁导坑施工软弱围岩段偏压大跨径隧道的工程项目越来越广泛,笔者通过对工程实例的研究,对双侧壁导坑的施工顺序与偏压隧道初期支护变形的相关关系,进行了归纳和总结,以期为以后的工程施工提供参考。     

喷气燃料静电消除技术研究

详细分析了喷气燃料中产生静电的原因,静电引起火灾的条件,讨论了避免静电产生的措施和消除静电荷的办法,研究了静电消除器的设计方法、材料选择、性能特点和应用注意事项.多年的应用及测试数据证明,自感应静电消除器能高效地消除喷气燃料输送过程中产生的静电荷,能确保喷气燃料使用中的静电安全.     

冰撞载荷作用下船舶夹芯抗冲击舷侧结构设计

伴随着"冰上丝绸之路"口号的提出,也为开发北极航道带来了空前的机遇。而北极航区有大量的浮冰存在,船舶航行时难免会遇到船与冰碰撞的问题。在查阅相关文献和掌握理论知识的基础上,利用ANSYS/LS-DYNA建立船舶--浮冰碰撞模型,分别对不同船舶夹芯式舷侧结构与普通结构和浮冰碰撞的损伤情况进行数值模拟计算,根据对数据结果的比较分析选取出一种较优的抗冰载荷作用的结构形式。