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黄敬章 《中国农村水利水电》2005,(8):76-77
结和祥丰大厦施工的工程实践,介绍采用后浇带的施工方法取代变形缝的设置及控制裂缝的产生,同时详细分析了混凝土裂缝产生的原因,并通过水泥品种、混凝土级配、外加剂的选用和使用;后浇带位置的科学布置,合理组织混凝土的施工工艺、浇筑顺序、养护方法;从而控制了超长结构底板混凝土未出现任何有害的结构裂缝及温度变形裂缝。 相似文献
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混凝土表面的裂缝是混凝土结构中的一种极为普遍的现象。章文着重论述了混凝土表面裂缝产生的原因,以及裂缝对混凝土的结构性能的危害,提出了混凝土表面裂缝处理的预防与处理技术,以供参考。 相似文献
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大型箱涵竖向裂缝原因分析及防裂措施 总被引:1,自引:0,他引:1
针对大型混凝土箱涵易产生竖向裂缝的现象,分析了裂缝产生的原因:一是水化热温差及混凝土收缩,二是管道设计分节过长,提出采用“后浇带”施工方法可以消除温降及收缩产生的应力从而减少竖向裂缝产生的可能。 相似文献
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水利工程中的混凝土结构应用较为广泛,混凝土裂缝的出现会导致混凝土结构的强度和安全性显著降低。基于此,施工单位需要提高对水利工程施工中混凝土裂缝的重视,明确混凝土裂缝的类型及出现原因,有针对性地应用混凝土裂缝控制技术,提升水利工程施工的质量。 相似文献
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水工建筑物混凝土裂缝成因与控制 总被引:1,自引:0,他引:1
吴隆顺 《中国农村水利水电》2008,(6):111-112
混凝土的裂缝是工程中较普遍存在的问题。水工建筑物混凝土的裂缝主要是:设计,材料,施工养护,使用等原因造成,也应在这几方面采取控制措施。列举了表面修补法等6种修补方法。 相似文献
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漕河渡槽是南水北调中线总干渠上的一座大型交叉建筑物,渡槽主梁和上部墙体等结构部分容易在早期温升和温降阶段产生温度和收缩裂缝,特别是高温季节,温控问题更加突出。采用混凝土温度场和应力场的有限元方法对对工程施工期进行施工过程模拟,根据温度防裂仿真计算结果,给出了施工期在高温季节的温控防裂方案建议,现场运用后,没有出现早期的表面裂缝和后期的贯穿性裂缝,实施效果良好。 相似文献
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混凝土结构在建设和使用过程中会出现不同程度、不同形式的裂缝,而大体积混凝土结构出现裂缝的机率更高,危及混凝土结构的安全性和耐久性,影响其使用功能。分析地下大体积混凝土裂缝产生的原因,提出相应的控制措施,以预防裂纹的发生和发展。 相似文献
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《Journal of Agricultural Engineering Research》1998,69(3):249-254
A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian and European, containing large amount of lycopene and β-carotene, respectively, were tested. The dried powder was stored under an atmosphere with O2and at three different temperatures, 5,20 and 35°C. The surface colour of the powder was monitored during storage by a Hunter colour ratioa/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of concentration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were calculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouration took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour ratioa/bof dried powder at 25°C showed good agreement with the experimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of carrot. The use of the induction period in the manner described may enable the shelf life of dried powder to be predicted. 相似文献
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The fractional outflow rate of water from the rumen, measured as the rate of disappearance of the chromium complex of ethylenediamine tetra-acetic acid, was related to a number of dietary factors. A multiple regression equation was derived which expressed fractional outflow rate as a function of the intakes of dry matter, ash, acid-detergent fibre and crude protein.The data analysed consisted of 243 observations for sheep on 59 diets, including forage, concentrate and mixed diets. The ranges covered by the data were: fractional outflow rate 0.7–3.6 day?1; dry matter intake 560–1400g/day; ash 4–30%, acid-detergent fibre 7–41%, crude protein 5–26 % of dry matter; there were no observations for sheep of less than 34 kg liveweight.The equation accounted for 56·3 % of the total variance. Between-sheep variance could not be calculated for the whole of the data but was undoubtedly substantial since, for a sixth of the data, it was known to account for 38 % of the total variance. 相似文献
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感官检验棉花的品级,这是农村常见的一种检测手段.它的一个主要特点就是存在不确定性.这是由于检验员的品级检验水平存在一定的差异,其中有很多因素制约着检验的结果.文章对影响感官检验结果的因素进行了系统的分析. 相似文献
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从灾害经济学的角度探讨了城镇供水优化调度的必要性和可能性,认为在缺水不可避免的情况下,对供水进行优化调度可以减小缺水带来的损失,产生较好的减灾效益,特别是可以大大减小严重干旱的灾害效应。并根据水资源的特性,提出了缺水损失的计算模式以及优化调度的原则和方法。 相似文献