海口某城市干道粉砂土路基施工技术

海口某城市干道位于冲积平原地区,路基填筑用土大部分采用周边地区粉砂土,本文主要阐述粉砂土路基施工技术要点。     

Exergetic analysis of closed Brayton thermal power cycle with reheater,regenerator and intercooler

Energy and exergy analysis of a Brayton cycle gas turbine power plant with regenerator, reheater and intercooler is carried out in this work. It has been found that the effects of the regenerator, intercooler and reheater are significant. Although, the energy analysis shows that the first law efficiency is more effective than the second law efficiency and there are significant losses in these components which cannot be neglected, and hence proper care should be taken for the size and operating conditions of these components. Efficiency of some components is 100% especially when energy balance is applied, while it is not 100% in the case of energy consuming/conversion systems like compressor, turbine, etc. The energy loss in reheater is zero while there is a small amount of exergy loss. The intrercooler has both energy and exery losses, so proper care should be taken in intercooler.     

对城市道路中淤泥固化土处理软土地基的浅析

在软土地基上修建道路,对软基的处理不当会产生严重的质量隐患,因而软基处理方法的选取,是城市道路建设的关键点之一。淤泥固化土具有一定整体强度和稳定性、环保节能等特点,满足作为地基材料的相关要求。结合连云港市的道路工程,从技术与经济、社会效益等方面分析淤泥固化土在城市道路中处理软土地基的优势。     

黄河淤泥多孔砖砌体的抗剪强度试验研究

本文通过对黄河淤泥多孔砖砌体抗剪强度的试验研究和对试验结果的分析,得出了黄河淤泥多孔砖这种新型墙体材料的抗剪强度规律及其抗剪破坏特征.结果表明,砂浆强度相同条件下,黄河淤泥多孔砖砌体的抗剪强度高于普通烧结砖和空心砖砌体强度的规范计算值.为此,提出了黄河淤泥多孔砖砌体抗剪强度平均值的计算公式,为黄河淤泥多孔砖的进一步研究提供了依据.     

基于FLUENT天然气集输管道直角弯管磨损分析

应用Fluent软件对直角弯管磨损情况进行数值模拟,研究天然气集输过程中有浮升力和无浮升力条件下不同颗粒直径、不同气流流速条件对弯管磨损的影响,研究结果表明:无浮升力和有浮升力条件下,随着粒径增大,弯管壁面的1.5 s累计最大冲蚀量先减小后逐渐增大,粒径小于50μm的微小颗粒对管壁的冲蚀磨损程度较小。有浮升力条件下,管道壁面的1.5 s累计冲蚀量有所增大,这是由于颗粒在浮升力作用下更多地碰撞弯管壁面。无浮升力和有浮升力条件下,随着粒径增大,弯管壁面的1.5s累计最大沉积量先快速下降而后缓慢增加。有浮升力的条件下,颗粒运动对壁面的沉积效应有所缓解,随着粒径的不断增大,浮升力对管壁的沉积影响逐渐变小。较小粒径的颗粒受浮升力影响在管道沉积方面表现更为敏感。无浮升力和有浮升力条件下,随着气流入口流速的不断增大,弯管壁面的1.5 s累计最大冲蚀量逐渐增大。有浮升力条件下,当入口流速增大时,增大的浮升力导致颗粒跳跃增多,浮升力作用增强了颗粒对弯管壁面的冲蚀破坏。无浮升力和有浮升力条件下,随着气流入口流速的不断增大,弯管壁面的1.5 s累计最大沉积量呈现先减小后逐渐增大的趋势。有浮升力条件下,入口流速增大时,边界层内速度梯度使颗粒旋转而产生更大的浮升力,致使颗粒的沉积量减少。但随着入口流速的继续增大,边界层厚度逐渐变薄,,浮升力的影响作用减小,颗粒沉积量增大。合理控制入口流速能够有效减少管道磨损。     

考虑胶结作用的木质素固化粉土边界面塑性模型

为研究木质素固化粉土的应力–应变特性,通过无侧限抗压强度试验和微观结构分析,探讨木质素固化土的胶结特性。基于边界面塑性理论,引入硬化参数、应力剪胀参数和胶结破坏速率等参数,提出考虑胶结作用的木质素固化土边界面塑性模型,采用非相关联流动法则和改进映射法则描述土体的不同破坏模式,并阐述模型中各参数的意义及计算方法。根据室内固结试验和三轴压缩试验,对木质素固化粉土的应力–应变、应力剪胀和超孔隙水压力变化特征进行分析,并验证了本文所提模型的有效性。研究表明:木质素产生的胶结作用是土体工程性质改善的主要原因之一;12%掺量木质素固化土屈服应力和不排水抗剪强度较素土分别提高约90%和40%,高、低围压下土体应力剪胀特性不同,围压对超孔隙水压力的变化影响较大;通过试验验证了模型计算的准确性,该模型可描述土体在不同受力状态下的应变特征,具有原理简单,参数明确的特点,可为固化土应力–应变的数值计算提供相应的理论基础。     

淤泥优化处理方法在环境岩土工程中的应用

淤泥优化处理在南部沿海地区已成为环境岩土工程中的重要组成部分。结合广东科学中心地基处理过程中所挤出的淤泥,对其产生的环境岩土工程问题进行了分析,并就淤泥的处理问题提出了前处理与后处理相结合的方法,即“吹砂填淤、填土挤淤,化淤为土、混土为料”,使淤泥实现资源化利用,防止了环境的污染与破坏,对同类工程具有一定的参考价值。     

风沙对钢结构涂层的冲蚀磨损性能研究

采用气流挟沙喷射法,在不同的冲蚀速度、角度、浓度和时间等风沙冲蚀参数下,对钢结构涂层进行了风沙冲蚀的模拟试验,对试验材料质量损失、抗冲蚀磨损性能和微观失效表面进行了分析.结果表明:钢结构涂层的耐磨性较差;冲蚀率随冲蚀速度呈指数增长,在冲蚀角度为45°时存在低速和高速2个冲蚀阶段;涂层的质量损失在冲角为45°时最大,90°时最小,表现出从脆性材料向塑性材料过渡的特征;低冲角时,材料破坏方式以微切削作用为主,决定材料耐冲蚀性能的主要因素是其硬度;在高冲角时,材料破坏方式以挤压凿削作用为主,决定材料耐冲击性能的主要因素是其柔韧性;涂层质量损失随下沙率的增大在300g/min时出现峰值;涂层累积质量损失随时间大致呈线性增长,冲蚀过程存在明显的潜伏期、加速期和稳定期.     

黏土矿物及粉粒对昔格达组粉质黏土可塑性的影响

结合西昌钒钛钢铁新基地所揭露的昔格达组粉质黏土的矿物组成及颗粒级配,通过验证性试验及前人研究成果,对黏土矿物及土体的颗粒级配对昔格达组粉质黏土塑性指数的影响进行分析。结果表明:黏土矿物及高粉粒含量是影响昔格达组粉质黏土可塑性的主要因素,高粉粒含量对昔格达组粉质黏土可塑性的影响比粉质黏土中黏土矿物种类及含量对其可塑性的影响大。但粉粒含量对黏性土体的塑性指数的贡献值具有一定范围,一般介于6～10。     

不同应力路径加荷时粉土的应力应变关系

对粉土在常规三轴仪上用改进的加荷方法进行了多种应力路径的试验,揭示了应力路径对粉土应力应变特性的影响;探讨了粉土的剪胀性以及用常规三轴试验得出的参数能否反映不同加荷路径等问题;推荐了几个合适的本构模型并给出了模型参数.     

Recycling of dredged river silt reinforced by an eco-friendly technology as microbial induced calcium carbonate precipitation (MICP)

A large amount of river silt is continuously dredged and usually dumped in landfills or oceans, resulting in land occupation and environmental pollution. Traditionally, cement-based materials are used to cement dredged river silt as building materials, which not only increases carbon dioxide emissions but also uses very little dredged silt. In order to realize the resource utilization of dredged river silt, microbial induced calcium carbonate precipitation (MICP) technology, which has the advantages of lower energy consumption, less environmental pollution and lower carbon emissions, is adopted to solidify the dredged river silt as roadbed materials in this paper. The unconfined compressive strength (UCS) test, calcium carbonate (CaCO₃) content test and microstructure test are carried out to analyze the mechanical properties of the solidified dredged river silt. The test results show that the MICP mixing method can be employed to solidify loose dredged river silt into high-strength construction materials. The concentration of the cementation solution has a significant effect on the solidification effect, and the most reasonable concentration of the cementation solution is 1.5 mol/L. With the increase of treatment times, the pores in the soil are filled with CaCO₃, and the UCS of the specimens after 10 times of treatment can reach 6.75 MPa with a relatively uniform CaCO₃ content of 27.8 %. The main crystal form of CaCO₃ is calcite, which can fill the pores and make the river silt particles cement as a whole, which is the main reason for the improvement of mechanical properties of dredged river silt.     

基于微观图像处理技术的土体三轴试验颗粒流模型

以扫描电子显微镜拍摄获取的粉土图片为研究对象,把数字图像处理技术引入土体的细观结构观察和定量分析中,求解土颗粒孔隙度、颗粒粒径及颗粒形状等微观颗粒组成参数,为建立颗粒流离散元细观模型提供物理参数。在此基础上,对土样的三轴试验进行模拟,并研究细观力学参数(包括:摩擦系数、平行连接强度及刚度比)对宏观性质的影响。研究表明:通过颗粒簇模型和颗粒排斥法可以实现土体微观颗粒形状和粒径组成模拟。所建立的颗粒流模型能够很好地拟合土体的应力-应变关系和模拟试验中的剪缩-剪胀现象;摩擦系数、平行连接强度和刚度比对土体的初始模量和残余强度的影响规律有所不同;通过监测孔隙率的变化,可以反映土体剪切带发展的过程。     

粉粒含量对尾矿力学特性的影响

 尾矿的力学特性与粉粒含量有关,但目前对粉粒含量的影响机制研究较少。为了研究粉粒含量对尾矿力学性质的影响及其细观机制,通过显微观测、三轴试验和离散元模拟,研究砂粒和粉粒的显微特征,分析尾矿的临界粉粒含量,并讨论粉粒含量效应的细观力学机制。结果表明：砂粒和粉粒在粒径分布、棱角性和表面形貌方面存在差异,粒径小于30 µm的颗粒具有独特的显微特征;随着粉粒含量的增加,混合尾矿逐渐由砂性尾矿过渡到粉性尾矿,临界粉粒含量在30%～50%范围;理论推导证明,粉粒的粒径和弹性模量越小,相同力作用下的土体形变越大;从介观上看,粉粒含量的增加弱化了原有的强力链,是导致粉粒含量效应的重要原因。研究结果揭示了混合尾矿的细观力学行为机制,为宏细观关联性研究提供了参考。     

Development of draft tube in hydro-turbine: a review

The efficiency of a hydraulic reaction turbine is significantly affected by the efficiency of its draft tube. The shape (profile) and velocity distribution at the inlet affect the performance of the draft tube. So far, the design of draft tubes has been improved through experimental observations resulting in ‘rules of thumb’ and empirical formulae. In the last two decades the use of computational fluid dynamics (CFD) for research and designing complex profiles has improved significantly due to its flexibility and cost-effectiveness. A CFD-based design can further be aided with robust and user-friendly optimisation. Numerical analysis of fluid through a draft tube is challenging and time consuming due to complex flow features. Hence there is a need for developing accurate and reliable CFD models together with efficient optimisation. Studies of the principles of draft tube, internal flow pattern, various turbulence models and associated divergence along with results have been presented in this paper. The objective of this paper is to present the application of CFD simulation in design and flow analysis of the draft tube and also find out the factors which influence the deviation of CFD results with experimental results. From the literature, it has been observed that there are several factors (accurate inlet conditions, turbulent models selected for simulation, modification in geometric parameters and accuracy in measurement of experimental results) that influence the draft tube design and performance. Thus, there is a scope of research for optimisation of geometrical parameters of the draft tube for its best performance at full load condition using CFD simulation. It is carried out by applying 3D velocity as an inlet boundary condition measured with particle image velocimetry/laser Doppler velocimetry.     

诱导风机设置对排烟效果影响模拟研究

运用FDS分析诱导排烟系统的布置方式、机械排烟量、诱导风速等敏感参数对排烟效果的影响,与风管式排烟系统进行比较。结果表明,诱导排烟系统在合理布置的条件下比风管式排烟系统更利于维持车库内的能见度;诱导排烟的能见度随机械排烟量的增加而提高;诱导风机风速受机械排烟能力的限制。     

低液限粉土路基施工方法探析

商开高速公路处于豫东低液限粉土地区,是公路路堤填筑的主要土料来源。针对低液限粉土的力学参数和用作填料的不利特点,经过分析和试验,找出了达到要求的施工参数。     

淤泥注浆加固技术在城市地道工程中的应用

提高淤泥自稳能力是淤泥中超浅埋暗挖地道施工的关键 ,本文结合福州某地道工程施工介绍了淤泥中的注浆加固技术 ,实践证明采用水泥—水玻璃双液劈裂注浆提高淤泥自稳能力是有效的     

Control of Airborne Particle Concentration and Draught Risk in an Operating Room

The influence of location of airborne particle source, ventilation rate, air inlet size, supply air velocity, air outlet location, and heat source on the dkributiuns of airborne particle concentration and draught risk in an operating room is investigated. The investigation is carried out by using a flow program with the k-E mdel of turbulence. Based on a standard case, five cases, each with one changed parameter, are computed, and the detailed field distributions of air velocity, temperature, airborne particle concentration, and draught risk are presented. The parametric study concludes that, for a better air quality and thermal comfort, it is desirable to use a higher inflow rate, a larger inlet area, and a uniform velocity profile of supply air. Outlet location and heat source have little influence on the disrributions of the particle concentration in the room. It has also been found that the distributions of particle concentration in the recirculating zone are very sensitive to the location of the particle sources.     

南通淤泥烧结多孔砖原料物理性能试验研究

对南通辖区6个不同土质特点的区域进行江海河沟淤泥取样,对淤泥密度、堆积密度、含水率、塑性指数等进行了测试,并进行颗粒分析.试验结果表明,典型样本大部分颗粒级配较好,塑性指数75.76％处在适合生产烧结砖的范围,同一河道不同河段塑性指数有时相差较大.并按JTG E40-2007《公路土工试验规程》进行试验,对GB/T 50123-1999《土工试验方法标准》测得的塑性指数进行复核.对南通地区淤泥烧结砖原料资源开发利用等提出建议.     

泥水盾构泥浆输送渣土冲蚀磨损力学性能的研究

为探究泥水盾构泥浆输送渣土时对弯管的冲蚀磨损规律,基于计算流体力学方法,利用FLUENT软件对泥浆弯管输送含粗渣土(≥20mm)泥浆的冲蚀磨损过程进行模拟仿真,采用单因素方法分析了泥浆流速、泥浆黏度和渣土体积分数3种因素对弯管冲蚀磨损的影响规律。通过室内试验对泥浆磨损性能进行探究并验证模拟仿真的正确性。研究表明：泥浆流速对弯管的磨损率和磨损位置均影响显著,并且与磨损率呈正相关;渣土体积分数主要影响磨损率;泥浆黏度对弯管磨损状况影响不大;主要磨损区域均集中在弯管30°附近。