聚丙烯纤维混凝土抗拉性能试验研究

以聚丙烯纤维的掺量和长度为变化参数,对二组各15个混凝土试件分别进行抗弯、抗劈拉试验,研究聚丙烯纤维对混凝土抗拉性能的影响。以试验结果为依据,分析了聚丙烯纤维掺量和长度对混凝土抗弯强度、抗劈拉强度及其韧性的影响规律,探索了聚丙烯纤维掺量和长度对混凝土抗弯强度、抗劈拉强度及其韧性影响的机理。研究结果表明,掺入聚丙烯纤维后,混凝土的抗拉性能明显改善,特别是混凝土劈拉韧性、抗弯韧性有较大幅度的提高。     

聚丙烯纤维对渠道矿渣混凝土力学性能影响的研究

为降低渠道衬砌混凝土的脆性,将聚丙烯纤维、粒化高炉磨细矿渣、聚羧酸系超塑化剂加入普通混凝土中。共采用体积含量占混凝土的0.1%、0.2%、0.3%、0.4%、0.5%、0.6%、0.7%和0.8%八个掺量的聚丙烯纤维,以及矿渣替代水泥量的35%、45%、55%、65%、75%五个掺量的矿渣组成的21个混凝土配合比。试验结果表明,掺加矿渣和聚丙烯纤维使硬化混凝土密度减小;对于大多数配合比的矿渣混凝土,聚丙烯纤维降低了抗压强度,提高了抗折强度和劈拉强度;其中0.2%~0.4%的聚丙烯纤维和45%~55%的矿渣是最优掺量。进一步以电镜扫描图(SEM)显示的混凝土基体微观结构解释了其宏观力学性能。     

基于温度梯度条件下混凝土衬砌结构的设计与应用

混凝土衬砌是地下工程结构的普遍形式,但在地热条件下,除温度作用外,地下水往往也具有一定的侵蚀性,这严重地影响了混凝土的耐久性,从而影响到衬砌结构的安全性.基于温度梯度及环境水侵蚀条件下,对隧洞衬砌应用双层混凝土结构,内层(保护层)为C20聚丙烯纤维混凝土,外层(结构层)为C30钢筋混凝土,并通过结构计算及室内试验研究,确定了各层混凝土的厚度与材料的最佳配比.采用的结构设计方法与混凝土配合比可供类似工程参考.     

抗冻混凝土外加剂掺量的合理化探讨

北方寒冷地区,混凝土的抗冻性能直接影响着工程质量耐久性.通过某工程C30F300混凝土配合比配选,就如何在满足混凝土抗冻耐久性和强度要求情况下,本着合理经济为原则,对外加剂掺量进行优化研究,并根据具体工程提出了混凝土外加剂的合理掺量.     

混杂纤维轻骨料混凝土压拉性能及强度预测

为了研究混杂纤维对浮石轻骨料混凝土力学性能的影响,对聚丙烯纤维掺量为0.6 kg/m³,改变纤维素纤维掺量的6组浮石轻骨料混凝土试块进行立方体抗压和劈裂抗拉试验.结果表明：立方体抗压强度和劈裂抗拉强度都先升高后降低.劈裂抗拉强度增加显著,最优掺量时为3.2 MPa,比基准组增加了77.8%,纤维掺入可以有效阻止裂缝发展并起到增强增韧的作用.最优掺量为聚丙烯纤维掺量0.6 kg/m³,纤维素纤维0.9 kg/m³,此时拉压比相比基准组提高了57.7%,显著改善了其脆性;最优掺量时3,7,14 d早期强度比基准组分别提高了25.2%,20.7%,15.6%.纤维素纤维对早期强度影响较大,根据其力学特性,提出了天然浮石轻骨料混凝土28 d立方体抗压强度的计算公式,并与其他公式进行了对比验证.采用BP神经网络对28 d强度进行预测,并用预测数据对抗压强度计算公式进行验证,验证结果良好.     

聚丙烯纤维增强混凝土的室内试验

通过对聚丙烯纤维增强混凝土的室内试验，研究了不同掺入工艺和微细掺料对纤维分散性能的影响，对比分析了聚丙烯纤维增强混凝土与普通混凝土的性能差异，同时掺入粉煤灰补偿因聚丙烯纤维的粘滞作用而导致混凝土流动性的降低，使混凝土具有良好的粘聚性和可塑性，改善混凝土的和易性,从而为聚丙烯纤维增强混凝土配合比设计提供了新的思路和理论依据。     

聚丙烯纤维混凝土衬砌堤坝应用数值模拟

素混凝土衬砌破坏一直是灌区建筑物健康发展的难题,由于素混凝土衬砌断面厚度较大、造价较高、衬砌自身刚性与背后堤坡之间存在较大间隙,在外界荷载的作用下常常发生破坏,从而严重威胁到灌区堤坝工程的安全运行。从堤坝衬砌破坏机理出发,针对破坏的位置以及破坏现象提出一种新型材料(聚丙烯纤维混凝土)堤坝衬砌形式,并利用通用有限元软件ADINA对素混凝土衬砌与聚丙烯纤维混凝土衬砌堤坝进行了数值模拟分析,结果表明:聚丙烯纤维混凝土衬砌同素混凝土衬砌堤坝相比应变基本相同,但其韧性与抗剪性能显著特高,是一种科学实际的衬砌方法。     

渠道衬砌胶粉混凝土性能试验研究

以C20W6F100混凝土为基准,配制胶粉掺量为6%、9%的胶粉混凝土和粉煤灰掺量为20%粉煤灰混凝土,进行拌合物性能、力学及耐久性能对比试验。结果表明:胶粉使混凝土拌合物的含气量增加,强度、弹性模量降低;胶粉混凝土的抗渗性能、抗冻性能以及抗冲磨性能优异,优于基准混凝土和粉煤灰混凝土。这表明,在胶粉掺量一定的条件下,胶粉混凝土应用于渠道衬砌是可行的。     

基于陶粒纤维混凝土的衬砌渠道抗冻胀性能研究

为改善北方寒区预制混凝土衬砌渠道存在衬砌板件自重大、尺寸小、装配效率低等问题,探讨将陶粒纤维混凝土用于衬砌渠道。基于正交试验法开展9组陶粒纤维混凝土和1组C35普通混凝土冻融前后力学性能试验,并结合冻胀数值模拟分析衬砌渠道抗冻胀性能变化。结果表明：陶粒纤维混凝土抗压强度因素影响次序为页岩陶粒体积取代率>聚丙烯纤维（PP）掺量>陶粒预湿时间,抗拉强度因素影响次序为PP掺量>页岩陶粒体积取代率>陶粒预湿时间,冻融后陶粒纤维混凝土抗压、抗拉强度损失率低于普通混凝土;衬砌渠道数值模拟的抗冻胀性能变化与材料性能变化趋势一致,陶粒纤维混凝土衬砌渠道抗冻胀性能损失小于普通混凝土衬砌渠道,最优抗冻胀性能损失减小4.68%,同时衬砌板重量减小18.47%;陶粒纤维混凝土作为渠道衬砌材料具有明显质轻的装配化优势。     

双掺粉煤灰及纤维混凝土在预制U型渠道防渗工程中的应用研究

针对预制U型混凝土渠道高抗裂性和高抗渗性的要求,结合宾阳那洪水库灌区渠道防渗工程特点,通过双掺粉煤灰及聚丙烯纤维实现预制U型混凝土渠道高抗裂性和高抗渗性,研究结果表明：粉煤灰掺量为胶凝材料总量的20%,聚丙烯纤维掺量为0.9kg/m3时,预制U型混凝土渠道的抗裂性和抗渗性显著提高,经济效益显著。     

有机硅集水措施对作物生长影响试验研究

采用有机硅喷涂、拍光压实及自然坡面3种集流措施收集雨水,研究在不同集流措施下种植带内水分动态变化,以及对作物生长发育的影响。结果表明,有机硅喷涂措施在作物生长季节能大大提高种植带内的土壤含水量和集水量。     

Economic analysis of rainwater harvesting and irrigation methods, with an example from China

The purpose of this paper is to evaluate the economic feasibility of agriculture with rainwater harvesting and supplemental irrigation in a semiarid region. The results show the importance of making full use of every open-air hardened surface to collect rainwater and to establish rainwater catchment areas by utilizing unoccupied land. The results also show that the usefulness of the harvested rainwater is enhanced when water saving and prevent seepage techniques are employed. The results indicate that in order to maximize investment it is essential to select crops with a water requirement process that coincides with local rainfall events. Potato was found to be the most suitable crop in the studied region. The economic indices for potato were superior to spring wheat, corn and wheat/corn intercropping. Therefore, potato production using rainwater harvesting and supplemental irrigation is the best alternative for cropping systems in the semiarid region of Gansu, China.     

内蒙准格尔旗雨水集蓄利用工程投资效益分析

为了解目前集雨节灌工程投资、效益状况以及发展过程中存在的主要问题,对内蒙准格尔地区集雨工程进行了经济投入产出分析,研究结果表明,旱井和水窖年收集1 m3水的成本分别为0.95元和1.56元,窖水滴灌玉米、蔬菜、果树的单方水平均产投比为6.14、12.52、9.10,经济效益十分可观。在内蒙准格尔地区,由于集雨工程及配套设施投资较大,农民收入水平较低。近期内农民不可能成为集雨工程投资的主体。在此基础上,作者提出将雨水集蓄利用工程纳入国家农村基本建设投资范畴,多方投入,加快工程发展速度,降低技术设备成本,完善集雨管理制度和办法等建议。     

Economics of rainwater harvesting for crop enterprises in semi-arid areas of East Africa

This paper presents an analysis of economics of rainwater harvesting by poor farmers in Tanzania. A questionnaire was used to survey 120 households to obtain information on the performance of their enterprises over 6 years (1998–2003). The information was mainly based on recollection as few farmers kept detailed records. Actual monitoring and measurements of yield and inputs was done in the farmers’ enterprises over 2 years during 2002/2003 and 2003/2004 production seasons. The analysis was done for four categories of rainwater harvesting systems differentiated by the size of catchments from which water is collected and the intensity of concentration and/or storage of the collected rainwater. These categories are: micro-catchments, macro-catchments, macro-catchments linked to road drainage and micro or macro-catchments with a storage pond. Results show that rainwater harvesting for production of paddy rice paid most with returns to labor of more than 12 US$ per person-day invested. These benefits are very high due to the fact that without rainwater harvesting it is not possible to produce paddy in the study area and rainfed sorghum crop realizes a return to labor of only US$ 3.7 per person-day during above-average seasons. For the rainwater harvesting systems, those designed to collect water from macro-catchments linked to road drainage, performed best during both categories of seasons. The results also show that contrary to expectations, improving rainwater harvesting systems by adding a storage pond may not lead to increased productivity. Another finding that goes against the widely held belief is that rainwater harvesting results in more benefits during the above-average seasons compared to below-average seasons. It is therefore, concluded that there is a potential for combining rainwater harvesting with improved drainage of roads. The construction of rural roads in semi-arid areas can beneficially be integrated with efforts to increase water availability for agricultural needs.     

雨水集蓄利用中的水质问题及对策

针对目前雨水集蓄利用中的雨水水质安全问题,从大气污染、雨水收集、窖水贮存、窖水消毒等几个方面分析了集蓄雨水污染成因,提出了研发筛选集流和窖体新材料、优化水窖结构设计和改进消毒方法、加强集流面与水窖管理等防止窖水污染和改善窖水水质的措施。     

集雨水质净化方法及应用

在对集雨水质特点进行简要分析的基础上,结合现有集雨水质净化处理的各种传统方法,重点介绍了初期雨水弃流技术、雨水粗滤处理技术、窖水慢滤净化技术、窖水终端过滤净化技术等几种集雨水质处理的新型实用技术,同时对其应用效果和特点给予分析。本文可为集雨利用地区选择集雨水质净化方法提供借鉴。     

橡胶浮石混凝土的抗冻性能及微观结构

为探究冻融循环条件下橡胶浮石混凝土宏观性能和孔隙结构的变化规律,进行冻融循环、单轴压缩试验,通过扫描电子显微镜(SEM)以及核磁共振(NMR)技术对橡胶浮石混凝土抗冻性进行分析,同时建立其抗冻性预测模型.结果表明:加入0.12～0.18 mm的橡胶可有效降低冻融条件下浮石混凝土表面的剥蚀、内部的损伤以及力学性能的衰减,...     

不同集雨垄面和垄沟宽度对马铃薯产量和土壤含水量的影响

研究了不同覆膜集雨垄面和垄沟宽度对土壤含水量、产量、商品薯率和产量WUE的影响。试验结果表明,对0~100cm土层土壤含水量的影响是随着集雨垄面宽度的增加而增加;对产量WUE、产量和商品薯率的影响具体表现为M_(50)G_(20)M_(60)G_(10)M_(40)G_(30)CK,随着集雨垄面宽度的增加,影响是先增加,当集雨垄面宽度为50cm,垄沟宽度为20cm时影响最大,而后随着集雨垄面宽度的增加影响逐渐降低。综合分析,初步推出M_(50)G_(20)这种模式集雨效果最好,能最大程度增加经济效益。     

水工抗冲磨混凝土试验研究

结合某工程实际,研究其大坝抗冲磨部位使用的抗冲磨混凝土的配合比设计.并对试验配合比的抗冲磨混凝土的力学变形性能、抗冲磨性能、抗裂性能以及抗渗性能和抗冻性能进行试验研究.同时,对掺入抗冲磨剂、聚羧酸类减水剂、萘系减水剂的抗冲磨混凝土的抗裂性能进行对比试验研究,结果表明:不同种类的外加剂对抗冲磨混凝土的抗裂性能有较大的影响.     

Hydrological impacts of rainwater harvesting (RWH) in a case study catchment: The Arvari River, Rajasthan, India: Part 2. Catchment-scale impacts

A key question in relation to rainwater harvesting (RWH) is whether the technique increases the sustainability of irrigated agriculture. A conceptual water balance model, based on field data from the Arvari River catchment, was developed to study and understand catchment-scale trade-offs of rainwater harvesting (RWH). The model incorporates an effective representation of RWH function and impact, and works on a daily time step. Catchment spatial variability is captured through sub-basins. Within each sub-basin hydrological response units (HRUs) describe the different land use/soil combinations associated with the case study catchment, including irrigated agriculture. Sustainability indices, based on irrigated agriculture water demand, were used to compare conceptual management scenarios. The results show that as RWH area increases, it reaches a limiting capacity from where additional RWH structures do not increase the benefit to groundwater stores, but reduces stream flow. If the irrigation area is increased at the optimal level of RWH, where the sustainability indices were greatest, the resilience of the system actually decreased. Nevertheless RWH in a system increased the overall sustainability of the water resource for irrigated agriculture, compared to a system without RWH. Also RWH provided a slight buffer in the groundwater store when drought occurred. The conceptual analysis highlights the important link between irrigation area and RWH area, and the impact of RWH on the catchment water balance.