Dispersive soil has the characteristic of being dispersed and lost when encountering water. In engineering practice, lime and cement are often used to modify dispersive soil, but doing so often has such problems as environmental pollution. The Si/Ca compound system composed of nano-silica sol and calcium chloride is selected as the modified material for dispersive soil. The effect of the modification is studied by pinhole test, mud ball test, and dispersion and disintegration test. The mechanism of dispersive soil modified by Si/Ca compound system is explored by physical and chemical properties tests. The results show that the dispersibility of soil can be completely eliminated by using nano-silica sol alone at 25% dosage or using calcium chloride alone at 0.40% dosage. However, the Si/Ca compound system composed of 1% nano-silica sol and 0.05% calcium chloride can also completely eliminate the dispersion of soil, which effectively reduces the dosage of the two materials used alone. The disintegration process of the soil modified by nano-silica sol modified is different from that of dispersive soil, with a shorter fmal disintegration time and a more stable disintegration rate. The fmal disintegration time is further shortened and the disintegration rate increases when the nano-silica sol and calcium chloride are used together. The mechanism of dispersive soil modified by Si/Ca compound system includes reducing the percentage of exchangeable sodium ions and the pH of the soil, and generating calcium silicate hydrate. The results demonstrate that the Si/Ca compound system composed of nano silica sol and calcium chloride can effectively modify the dispersive soil.

为了探究城市化进程对城市降水量的影响,使用简单移动平均法探究分区研究的可靠性和代表性;改进降水变率和增雨系数,定义2个全新的年际衡量指标—指数化降水变率,新增雨系数,从定性和定量2个角度研究城市化对二者的影响及相关关系.结果表明:重庆市城市化的水平受多方面的影响,在时间序列上呈现稳步上升的趋势,如今已处于成熟阶段并趋于稳定状态.重庆市城市化进程促进同期的新增雨系数的增加,抑制城市中指数化降水变率的变化,使得年平均降水量在小范围内波动,可通过控制城市化的发展进程协调城市降水量与降水变率,进而合理管控水资源循环过程,调整城市生态环境,改善人们生活环境,促进社会全面健康可持续发展.

Arid regions are sensitive to changes in precipitation, while El Niño-Southern Oscillation strongly influences worldwide hydrometeorological processes. Temporal and spatial changes of characteristics including precipitation, annual mean temperature and area in China's arid region were analyzed, using daily precipitation and temperature data from 117 meteorological stations of 1961–2016. The results show that: (1) The arid region is getting warmer and wetter. During the past 56 years, the precipitation in the arid region have shown an increasing trend. The annual and quarterly precipitation all exist a cycle of about 4 years. There is a negative correlation between the area of the arid region and the annual mean temperature, which is significant at the 0.01 level. (2) The area of arid region has been on a downward trend since 1968, and there was a mutation in 1992. There are three main cycles of 24 years, 13 years and 5 years in the area of the arid region. During the study period, the spatial center of the arid region’s precipitation moved 0.14° to the north and 0.77° to the east. (3) The response of precipitation to ENSO is different between the eastern and the western arid region. El Niño events increased the area of China’s arid region in El Niño years and La Niña events increased the precipitation of China’s arid region in La Niña years. The response of China’s arid region to ENSO in the first half of the following year is opposite and the response in spring is the most significant. To sum up, in El Niño years the eastern arid region increased in area and precipitation, while in La Niña years the western arid region decreased in area and the eastern arid region increased in precipitation, which was related to the eastward movement of the spatial center of the precipitation.

Abstract Arid region is sensitive to changes in precipitation, while global warming and El Niño-Southern Oscillation strongly influence worldwide hydrometeorological processes. Temporal and spatial changes of characteristics including precipitation, annual mean temperature and area in China's arid region were analyzed, using daily precipitation and temperature data from 117 meteorological stations of 1961-2016. The results show that: (1) During the past 56 years, the precipitation in the arid region have shown an increasing trend. The annual and quarterly precipitation all exist a cycle of about 4 years. (2) The area of ​​the arid region has been on a downward trend since 1968, decreased significantly after 1998. There are two main cycles of 13 years and 5 years in the area of ​​arid region. During the study period, the center of the arid region’s precipitation moved 0.14° to the north and 0.77° to the east. (3) During the past 56 years, increasing of the arid region’s temperature has been more obvious than the average temperature increasing in China. In 1990, the annual average temperature in arid region changed from a decreasing trend to an increasing trend and there is a negative correlation between the area of arid region and the annual mean temperature, which is significant at the 0.01 level. (4) The degree of precipitation response to ENSO in the eastern part of the arid region is more obvious than that in the western part. El Niño events extended the size of China's arid region and increased the average precipitation in the arid region. The precipitation of the east increased more than the west. And La Niña events significantly reduced the area of ​​the arid region, with more precipitation than the average in the eastern part and less precipitation in the western part. The impact of ENSO is one of the reasons for the arid region's center of precipitation shifting eastward.

针对地表植被覆盖差异对遥感监测区域干旱精度的影响问题,通过GLDAS获取1978-2017年吉林省44个区县的降水、潜热通量和显热通量数据,以此构建了标准化波文比指数(SBI),在此基础上结合标准化降水指数(SPI),通过Copula函数构建出反映土壤水分和降水的综合干旱指数(MSBP),并用其分析吉林省的干旱时空特征,通过比较SBI、SPI和MSBP在历史干旱严重年份上的表现,以及分析3种指数与粮食产量之间的相关性,以此评估不同干旱监测指数的应用效果.结果表明:①MSBP在描述干旱特征和干旱对粮食产量影响上更加全面和准确.②MSBP能较为准确地刻画出干旱过程的持续时间以及不同时间下的干旱强度.③在历史干旱严重的年份上,MSBP所刻画的干旱特征和实际发生的干旱过程较为一致.④MSBP能较好地反映出干旱对粮食产量所引起的波动变化.以上研究结果为区域干旱监测提供参考.

分散性土在世界各地特别是干旱半干旱地区分布广泛,属于一种水敏性的特殊土,抗水蚀能力很低,容易形成管涌、洞穴、冲沟等破坏,对建筑物的安全性造成严重威胁.对分散性土的定义与内涵、分散机理、鉴定方法、改性应用进行了分析、总结与展望.分散性土是一种在水力坡降很低条件下由于土颗粒间的排斥力超过吸引力而导致土体产生分散流失的黏性土.分散性土的形成机理在于土体中的胶结物质特别是黏粒含量低或土体中含有较多的钠离子和酸碱度呈碱性.一般采用双比重计、碎块、针孔、孔隙水可溶性阳离子和交换钠离子百分比等室内试验结果来综合鉴定土样的分散性,野外调查和经验模型等方法可作为辅助鉴定手段.采用物理保护、化学改性或综合处治提高分散性土的水稳性,其中化学改性是最根本的方法.在未来的研究中,应重视与加强研究土粒间斥力与引力关系、探索分散性土渗透破坏特别是土体裂缝演变规律、研发经济高效环保的改性材料等方面工作.

Monthly streamflow has elements of stochasticity, seasonality, and periodicity. Spectral analysis and time series analysis can, respectively, be employed to characterize the periodical pattern and the stochastic pattern. Both Burg entropy spectral analysis (BESA) and configurational entropy spectral analysis (CESA) combine spectral analysis and time series analysis. This study compared the predictive performances of BESA and CESA for monthly streamflow forecasting in six basins in Northwest China. Four criteria were selected to evaluate the performances of these two entropy spectral analyses: relative error (RE), root mean square error (RMSE), coefficient of determination (R2), and Nash–Sutcliffe efficiency coefficient (NSE). It was found that in Northwest China, both BESA and CESA forecasted monthly streamflow well with strong correlation. The forecast accuracy of BESA is higher than CESA. For the streamflow with weak correlation, the conclusion is the opposite.

分散性土的抗冲蚀能力很低,对许多工程的安全性造成严重威胁.在分析土样物理化学性质和矿物学性质的基础上,采用双比重计、碎块、针孔、孔隙水阳离子和交换性钠百分比等试验方法,对大石峡水电站大坝防渗土料的分散性及其改性措施进行了研究.研究结果表明,土样1号和4号属于分散性土,2号、3号、5号属于过渡性土.土样产生分散的主要原因:一是土样中含有数量较多的钠离子,使得伊利土也像那钠基蒙脱土一样具有较强的分散性;二是酸碱度较高,使得土颗粒之间的斥力能大于引力能,促使土样分散;掺入质量分数0.26％的AlCl3·6H2O或质量分数0.35％的CaCl2都会对分散性土样产生显著的改性作用.结果表明:土样产生分散的条件是土样中含有大量的钠离子和较高的pH值;AlCl3·6H2O的改性效果明显优于CaCl2,是一种有效的分散性土改性剂.

In order to evaluate the dispersion degree of clay, based on the influential factors such as the physical, chemical and mineralogical indicators, the evaluation model is established according to principal component analysis ( PCA) method. The dispersion degree of 12 groups of clay sample is evaluated by this model. The results indicate that the dispersion degree of No. 3 soil sample is the largest because the content of montmorillonite is the highest and the sodium-ion and the total soluble salt are higher;on the contrary, the dispersion degree of No. 6 soil sample is the smallest, because the content of montmorillonite is the lowest and the sodium-ion and the total soluble salt are relatively smaller, also the organic matter and clay content is relatively large. The above results are consistent with the experimental ones. This method provides a theoretical basis for dispersive soil modification.

Soil cement is a synthetic building materials,the compacted cement soil has good mechanical properties of engineering. Damage calcula-tion model of the clay cement-soil seepage deformation was established,in order to explore the clayey soil cement penetration deformation law. The paper carried on the indoor seepage deformation experiment research of two factors on the affect clay soil-cement seepage deformation damage more prominent cement and ages by the method of indoor test. The results of statistics and regression analysis show that there is a correlation of the linear logarithmic height between the slope of the clay cement-soil seepage deformation damage and the dosage of cement and ages. Preliminary test model between them is established.

选用砂土和盐碱土并添加斥水剂,采用0、1、3和6 g/L的CaCl2溶液进行室内土柱入渗试验,对比灌水水质对土壤水盐及斥水性分布的影响.结果表明:咸水灌溉后,砂土1和亲水盐碱土的累积入渗量、湿润锋和入渗率曲线均较光滑;而砂土2和斥水盐碱土的入渗特征曲线不如砂土l的光滑,入渗过程比前者慢得多.灌水矿化度增加对盐碱土的入渗过程影响更明显.Philip模型与Kostiakov公式拟合亲水土壤入渗率过程都较好.砂土l和砂土2在咸水灌溉后剖面的滴水穿透时间都比初始值有所增加,但最大增加值仅3.6s.盐碱土灌后剖面的滴水穿透时间增加明显,最大增加值为19 s.灌水矿化度增加对电导率、Ca2+质量浓度和Cl-质量浓度分布均有影响.研究表明咸水灌溉不仅影响水盐分布,而且对斥水性也有不同程度的影响.

阐明了“水文学原理”课程的性质及其重要性，在论述课程内容基础上，分析了本门课程具有内容多、与先行课程关系密切、应用性强的特点。结合水文与水资源工程本科生教学提出了精心组织授课内容、注重积累教学方法和经验、讲究教学方法和艺术、突出重点、抓住关键和加强辅导等五点体会。

In order to understand the cement soil compaction characteristic, through indoor compaction test methods, study on the different amount of cement soil in dry and wet compaction test. The results showed that in the standard compaction power, the optimum moisture content and the maximum dry density of cement soil present a certain regularity with different cement quantity. When the cement quantity and compaction work at the same time, the optimum moisture content and the maximum dry density are significant differences in the dry and wet compaction conditions. It is of practical significance to the geotechnical engineering construction of using cement soil construction or reinforcement.

针对西北农林科技大学"水利水能规划"课程的教学现状,提出采用多种教学手段,提高教学效率、建立"水利水能规划"实践课、建立合理的教学大纲体系、完善考核制度以及灵活选用教材等,从而提升该课程教学成效。

双语教学是近年来各高校积极倡导和推行的一种新的教学模式,是当前高校教育改革的热点。文章在论述双语教学的意义和重要性的基础上,分析了西北农林科技大学双语教学过程中存在的问题,并就如何搞好双语教学提出了自己的几点看法。

基于水利水能规划及课程设计历年授课经验，作者通过分析思考，指出课程授课及课程设计等理论教学和实践教学环节中出现的问题，并提出相应的对策和改革方案，以增强改革教学效果，提升教学质量。

针对青海省抗旱服务组织的发展现状和存在的主要问题,结合全省干旱灾害特点及发展趋势,以青海省编制抗旱规划的有利时机为契机,探讨了青海省抗旱服务组织的发展设想和新思路。

In order to find out the qualitative and quantitative relationships between triaxial tensile strength and triaxial shear strength,contrast experiments are carried out including triaxial tensile,triaxial shear and uniaxial tensile with remolded samples of unsaturated clay in core wall of Heihe Dam in Xi'an,Shannxi province under different moisture contents. The experimental results show that:(1) the shear intensity index of unsaturated clay c and ? decrease with the increasing of moisture contents;(2) though triaxial or uniaxial experiments of unsaturated clay,the Mohr circle,which is decided by confining pressure as major principal stress and axial stress as minor principal stress,accords with Coulomb criterion;and (3) there is functional relationship between tensile strength and shear strength of different unsaturated clay samples with same physical nature. Based on these conclusions, tensile strength of unsaturated clay can be estimated through results of shear tests without tensile strength test conditions.

依据国家计委、水利部《河道管理范围内建设项目管理的有关规定》(水政[1992]7号),对在河道管理范围内建设的码头工程,应进行防洪评价。根据2004年8月印发的《河道管理范围内建设项目防洪评价报告编制导则》(试行)内容要求,进行了拟建码头工程防洪影响分析,主要内容包括河道演变分析、防洪评价计算和防洪综合评价等。河演分析结果表明,工程河段多年来河势稳定,河道深槽位置及两岸的江岸基本保持稳定;码头工程附近江岸基本稳定,工程水域河床冲淤幅度相对较小,具备开发利用的条件。平面二维数学模型计算结果表明,工程修建后对河道水位及流场的影响较小,码头工程的修建不会对其所在河段河势及行洪产生明显不利影响。