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A 3D discrete FEM iterative algorithm for solving the water pipe cooling problems of massive concrete structures 
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下载免费PDF全文 Water pipe cooling has been widely used for the temperature control and crack prevention of massive concrete structures such as high dams. Because both under‐cooling and over‐cooling may reduce the efficiency of crack prevention, or even lead to great harm to structures, we need an accurate and robust numerical tool for the prediction of cooling effect. Here, a 3D discrete FEM Iterative Algorithm is introduced, which can simulate the concrete temperature gradient near the pipes, as well as the water temperature rising along the pipes. On the basis of the heat balance between water and concrete, the whole temperature field of the problem can be computed exactly within a few iteration steps. Providing the pipe meshing tool for building the FE model, this algorithm can take account of the water pipe distribution, the variation of water flow, water temperature, and other factors, while the traditional equivalent algorithm based on semi‐theoretical solutions can only solve problems with constant water flow and water temperature. The validation and convergence are proved by comparing the simulated results and analytical solutions of two standard second‐stage cooling problems. Then, a practical concrete block with different cooling schemes is analyzed and the influences of cooling factors are investigated. In the end, detailed guidance for pipe system optimization is provided. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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褶皱的水力连通长度是复合褶皱渗漏量评估的关键参数,褶皱网络的水力连通性分析还缺乏客观高效的分析方法。基于对漏洞周围水头分布的简化,提出以搜索长度为标准判定褶皱间水力连通性。通过将褶皱线段化,建立了褶皱网络连通性数字化分析方法,并编制了相应的分析程序,研究了该方法在文献报道的褶皱网络和处于良好状态的GM/GCL（土工膜/土工复合膨润土垫）衬垫中的应用。结果表明：搜索长度的定义给出了判定褶皱间水力连通性的客观标准,能反映衬垫的不同参数（如水头、界面导水系数以及渗透系数等）对褶皱间水力连通性的影响。褶皱线段化使褶皱位置和尺寸的描述更容易,数字化的水力连通分析简便且高效。基于该水力连通性分析方法的渗漏量评估结果偏保守。在进行渗漏量计算时,若假定统一的长度来描述褶皱网络,则需要根据漏洞频率的不同选择不同值。该水力连通性分析方法作为渗漏量评估完全数字化的关键环节,具有重要的应用前景。 相似文献
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Change of groundwater chemistry from 1896 to present in the Mid-Levels area, Hong Kong 总被引：1，自引：0，他引：1
In this study, groundwater quality information collected in 1896 (well waters), 1980/1981 (piezometric and seepage samples)
and 2002/2003 (seepage samples) in the regions centered by the Mid-Levels area, Hong Kong Island, was compared to illustrate
how groundwater quality has changed over a century and the processes controlling it. As shown by saline ammonia and nitrate
levels in the late nineteenth century, groundwater was severely polluted by widespread and obvious leakage from poorly designed
wastewater collection systems, although groundwater was still a drinking water source for local residents. The extremely high
residual chlorines in groundwater demonstrated that large doses of disinfection agents were added to wells at that time. In
view of the decline in saline ammonia and nitrate levels, groundwater became less organically polluted in the 1980s probably
due to significant improvement of the design of underground sewers. However, more leakage from sources such as salty flushing
water and fresh water pipes emerged in the past few decades which added complexity to groundwater chemical systems. Some chemicals
were used to identify possible locations of leakages. The temporal variations of the distribution of these chemicals over
the area may shed light on the rate of leakage. Leakage from service pipes seems to have improved from the early 1980s to
2002/2003. However, the area is still suffering from widespread and small-scale leakage from service pipes. More efforts should
be paid to control small leakages in the future. The findings will be instructive to various government organizations such
as the Water Supplies Department and Drainage Services Department to identify possible locations of unobvious leakages in
the area. 相似文献
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褶皱网络中褶皱的空间分布是水力通性分析及渗漏量评估的基础。褶皱的空间分布规律尚待研究。基于一个典型场地的场底褶皱网络,利用K-S检验方法分析了褶皱几何参数服从的概率分布类型,统计得到了褶皱几何参数相应的统计参数。提出了基于褶皱几何参数的统计规律随机生成褶皱网络,并对随机褶皱网络进行渗漏量评估,然后从随机分析得到的渗漏量中选择特征值来表征场地的渗漏量的方法。通过案例分析,研究了该方法的应用。结果表明：对典型场底褶皱网络的统计分析为确定类似场地中褶皱几何参数的概率分布类型和统计参数具有重要的参考价值。由随机生成的褶皱网络得到的渗漏量样本的均值可以作为特征值,用来保守地评估场地内实际的渗漏量。基于案例分析,在对褶皱几何参数统计规律积累了丰富的经验后,可以实现对待建场地的设计不再需要获取整个场地的航拍图像,从而为有褶皱场地渗漏量评估提供了新思路。 相似文献
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基于煤矿井下陷落柱、小断层等地质异常体精确探查对漏失地层近水平孔取心钻进的迫切需要,采用双壁水力反循环连续取心技术进行井下地质异常体探查,分析其技术原理及特点,研制配套的ø89/42 mm双壁取心钻杆和反循环取心钻头,并在某地面矿山进行功能性试验,共施工完成3个近水平取心钻孔,单孔最高取心率为83.6%,最大回次进尺69 m,平均钻进效率为3.61~6.26 m/h。针对漏失地层冲洗液漏失严重的问题,提出双壁取心钻具的结构改进优化方案,采用改进后的取心钻具岩心上返通道返水流量和流速大幅提升,最后指出该套反循环取心施工中出现的钻孔环空排渣及岩心卡堵问题并提出了针对性的解决方案,包括采用正反循环排渣法解决钻孔环空排渣问题和采用中心通道打水解卡方法解决岩心卡堵问题。试验表明:该套双壁取心钻具满足煤矿井下地质异常体探查的施工需要,为煤矿井下地质异常体探查提供新的技术途径。 相似文献
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为了验证常规圆孔筛管和割缝筛管在瓦斯抽采过程中煤粉抗堵性上的差异,利用PFC3D离散元分析软件分析了常规圆孔筛管和割缝筛管的煤粉通过性能,根据模拟结果优选了割缝参数,并在阳泉矿区寺家庄煤矿15117工作面回风巷15号煤层中进行了常规圆孔筛管和3种不同割缝参数的割缝筛管的瓦斯抽采试验。数值模拟结果表明：总体趋势上,割缝筛管的煤粉通过量要小于圆孔筛管,对于割缝筛管,割缝宽度对煤粉通过量的影响要大于割缝长度;现场试验表明：抽采试验中采用割缝筛管护孔的抽采孔平均瓦斯流量和瓦斯浓度分别是常规圆孔筛管护孔抽采孔的6倍和3.8倍,验证了煤粉通过量越小的筛管,其抗堵性能越优,瓦斯抽采效果也越好。 相似文献
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为了研究水热型融雪化冰路面结构中金属导热管合理布设间距, 建立了基于传热学理论的路面融雪化冰有限元分析模型, 对不同外界气温、 不同埋设间距工况下金属热管融雪化冰能力进行计算分析. 结果表明: 外界气温在0~-10 ℃之间时, 热管融雪效果明显. 气温低于-10 ℃时, 热管尽量埋设至路面中部; 热管最优间距为100~200 mm, 当热管间距>200 mm时, 即使管内水温高达40 ℃, 0 ℃ 等温线将不再连续. 相似文献
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在阐述油压夯管技术及特点的基础上,说明了油压夯管锤结构及工作原理,建立了油压夯管锤数学模型,进行了较深入的内部工作华而不实结构参数的优选,介绍了油压夯管设备的研制内容及过程。 相似文献
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The Messina Copper Mines comprise a group of breccia pipes, disseminated replacement and fissure deposits within an area 20 km long by 1 km wide, emplaced within high-grade metamorphic rocks of the Limpopo mobile belt. Breccia pipes as well as associated hydrothermal copper deposits are aligned along a northeast trend which forms a southwestern projection of the Nuanetsi Igneous Province. The "L" and West lode breccia columns are known over a vertical extent of 1 250 metres, and are not exposed on surface; they are circular to polygonal in plan outline, as a result of joint controls. Peripheral microbreccia grades downwards and inwards to macrobreccia. Downward displacement of country rock marker zones indicate a maximum 1 – 3 per cent volume increase, while observed interfragmental fill constitutes 15 – 25 per cent. Hydrothermal alteration of wallrock gneiss mantles the breccia columns and does not extend to surface; it is comprised of distinct zones, the outermost characterized by sericitized gneiss, grading to an albitite, and finally to zoisite-quartz rock around the immediate brecciated contacts, and within the pipes. The interfragmental fill consists largely of quartz and sulphides, and grades downwards to albite + sulphides in the West Lode pipe. Sulphide mineral distribution is zoned, pyrite dominating in the apex of the pipes, grading downwards to chalcopyrite-bornite and then bornite-chalcocite at deeper levels. The nature of the fragmentation precludes normal stoping collapse mechanisms for brecciation and suggests a single implosive event. Chemical reaction induced shrinkage of fragments probably created the bulk of the interfragmental volume. 相似文献
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中国北方岩溶地下水污染分析 总被引：5，自引：0，他引：5
近年来,受气候变化和强烈人类活动的影响,环境物质及能量多频次、大范围的输入,极大程度上改变着岩溶水系统的水环境质量,岩溶水生态环境遭受不同程度的威胁和破坏,岩溶水水质日趋恶化。本文归纳分析了我国北方岩溶水系统水质特征、污染现状、污染来源及污染途径。我国北方岩溶水水质类型中硫酸盐型水和氯化物型水的分布逐渐增加,主要污染组分为总硬度、SO42-、F-、NO3-和TDS等。其中硫酸盐和硝酸盐污染强度和范围最大,呈现出显著的人类活动影响特征。依据我国北方岩溶系统结构及水力学特征,将岩溶水污染途径概括为:①连续入渗型——主要包括岩溶区地表水（河流、水库等）渗漏污染,城镇污水渠或排污管道破损引起的污水渗漏污染;②越流型污染——污染孔/裂隙水（含矿坑水/老窑积水等）越流污染岩溶水;③间歇入渗型——固废淋溶入渗和污水灌溉渗漏污染等。据此提出了推进岩溶水水资源保护和污染防治的合理化建议。 相似文献
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基于MapInfo的城市综合管网信息系统的开发 总被引：7，自引：0，他引：7
在分析城市综合管网信息管理现状和发展趋势的基础上,初步论述了在GIS平台下开发城市综合地下管网信息系统的意义和步骤,分析了系统应具有的功能和开发模式,并在此基础上介绍了开发设计的城市综合管网信息系统。 相似文献
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从混凝土管材的选定、工作坑的设计及施工、顶管顶进中若干关键问题入手,介绍了手掘式顶管施工技术在成都市中心城水环境综合整治工程G标段管道排水工程中的应用。 相似文献
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高坝洲地区岩溶水系统的研究方法与意义 总被引：2，自引：0，他引：2
本文根据高坝洲水利枢纽工程的实际需要,提出了该区岩溶水系统的划分标准,据此对研究区岩溶水系统进行了划分,并论述了各岩溶水系统的特征和相互关系。在此基础上,应用数值模拟方法对研究区相应的水文地质参数进行了识别,并对蓄水后库水的渗漏途径、渗漏量进行了预测,为防渗帷幕的设计和施工提供了科学依据。 相似文献