高速铁路软基深层搅拌桩施工工艺试验研究

通过高速铁路软土地基处理现场试验及水泥土室内试验,对深层搅拌桩的施工工艺进行了较系统的研究。结果表明:不同深层搅拌桩机型、相同机型不同机组的成桩强度均存在一定差异;施工时,选择施工队伍与选择机型同样重要;10 m复搅和全程复搅、增加复搅次数对桩体无侧限抗压强度影响不大,深层搅拌桩施工工艺宜用10 m复搅;不同地层对桩体无侧限抗压强度影响较大;浆喷桩桩长在12 m以内时,桩体无侧限抗压强度比较均匀,施工质量可控性较高。     

钉形搅拌桩单桩承载力的数值模拟分析

钉形水泥土搅拌桩是一种新型的水泥土搅拌桩技术,它解决了传统水泥土搅拌桩的诸多问题,具有良好的工程效果。该文简要介绍了钉形搅拌桩的施工机械和施工工艺,其采用的新工艺保证了桩体中的水泥掺入量,提高了水泥浆分布的均匀性,从而保证了桩身质量,特别是深部桩体的质量;主要采用三维有限差分法对钉形桩单桩承载特性进行了模拟分析,发现钉形搅拌桩单桩Q-s呈陡降型;其单桩极限承载力高于常规水泥土搅拌桩,并随扩大头高度H、扩大头直径D、桩长L和桩体模量Ep的增加逐渐增大。     

Physical processes in the ROFI regime

The distinctive feature of all ROFI (Regions Of Freshwater Influence) systems is the input of significant amounts of buoyancy as freshwater from river sources. If the spatial scale is unrestricted by coastal topography and stirring is weak, this input tends to drive a coast-parallel flow in which the Coriolis force constrains a wedge of low density water against the coastal boundary. Without frictional effects, this flow is subject to baroclinic instability which induces large meanders and eddies in the flow but in, many ROFIs, the tidal flow induces frictional effects which stabilise the density driven flow.In the absence of the effects of rotation and stirring, the buoyancy input tends to induce stratification through an estuarine circulation in the direction of the gradient. When stirring is applied, by the action of wind, waves or tidal flow, the density current is suppressed but is rapidly re-established when stirring ceases, as in the Linden-Simpson (1988) laboratory tank experiments. In real ROFI systems, a combination of all these processes operates so that the structure of the water column and the flow is the result of a competition between the stratifying influence of buoyancy input and the net stirring effect of the wind, waves and the tides. This competition is more difficult to analyse than the heating-stirring competition, because freshwater buoyancy input is not spatially uniform but enters at discrete sources along the coast and its subsequent spreading has to be determined.While the springs-neaps cycle in tidal stirring imposes a regular fortnightly modulation on vertical mixing, the influence of the wind is irregular and depends, not just on the magnitude of the stress, but also on the direction in which it acts. In some exposed shallow water situations there may also be significant stirring due to waves generated by non-local winds.ROFI systems are further complicated by the action of tidal straining in which differential advection, due to vertical shear in the tide, interacts with the density gradient to generate fluctuations in vertical stability at the tidal frequency which, in some cases, are of sufficient amplitude to switch the water column between stable stratification and vertical density homogeneity each tidal cycle. This straining along with the other ROFI processes have been incorporated into a series of 1-D models to provide a more objective test of the hypotheses about the mechanisms involved. Comparison of model hindcasts with observations indicate that we now have a first-order understanding of the complex behaviour of ROFIs.On a global scale it is clear that ROFIs represent an important component of the shelf-sea environment of particular concern in relation to the impact of pollutant discharges. To date, most studies of ROFI's have concentrated on systems in temperate latitudes but attention needs to be focused on the very extensive ROFIs in tropical regions where most of the world's river discharge enters the ocean. In monsoonal regions, these inputs exhibit strong seasonal modulation which may, in competition with tidal stirring, result in an annual cycle of stratification and the formation of fronts.     

高速公路软基加固技术应用实例

文章介绍了深层搅拌桩、袋装砂井堆载预压、管桩加固某标段高速公路软基的施工技术,分析了施工中存在的技术问题并提出相应的对策。     

粉煤灰、矿渣双掺混凝土在海底隧道二次衬砌中的应用研究

结合厦门东通道海底隧道二次衬砌混凝土配制的主要技术途径和配合比参数的合理选择,在试验基础上研究了混凝土制备过程中功能性掺合料粉煤灰和矿渣粉的性能及其双掺用量对混凝土强度和耐久性的影响,阐明采用粉煤灰和矿渣粉双掺混凝土将是解决海底隧道衬砌混凝土耐久性问题的新途径。     

盲分离技术识别发动机的机械和燃烧噪声源

简要介绍了盲分离基本思想及AC算法,提出盲分离仅用测得的柴油机混叠噪声源可分离干扰噪声、机械噪声和燃烧噪声。试验验证了在存在干扰噪声时,新办法也可识别出有用的噪声源,且测试所用的仪器少,从而为发动机噪声源识别提供了一种行之有效的新办法。     

沥青拌和站建设中有关问题的探讨

针对建设公路沥青拌和站过程,从拌和规划、选址、加热方式选择、拌和设备选型、配套设施、环保等方面入手,分析并探讨了建设合理、高效的沥青拌和站的方法及应该注意的问题.     

搅拌设备液压传动系统方案设计

根据工程中常用的2种伺服系统,讨论了搅拌设备的传动系统方案,给出了液压传动系统方案的设计.研究表明,搅拌设备的机、电、液一体化是实现智能化的必要条件之一,液压传动系统方案可由控制器、伺服阀、变量泵、低速大扭矩定量马达系统组成.     

公路沥青玛蹄脂碎石(SMA)路面混合料配合比设计及技术要求

沥青玛蹄脂碎石路面近年来较为广泛地用于高速公路的新建及大修中。根据工程的使用情况简单地介绍了沥青玛蹄脂碎石(SMA)路面混合料配合比设计及技术要求。     

砼搅拌运输车搅拌筒对数螺旋线螺距的探讨

通过在球面坐标系中推导搅拌运输车搅拌筒对数螺旋线的参数化方程,并用拌筒的设计参数表达螺距方程．总结了在UG中生成圆锥对数螺旋曲线的四种方法。