存在高渗透区的黏土心墙土石坝渗流稳定性分析

黏土心墙土石坝是重要的挡水建筑物,心墙的低渗透性可以大幅降低坝体水力梯度,减少坝体发生渗透破坏的风险。然而心墙的质量问题（如局部高渗透区）会影响坝体的渗透稳定性,甚至酿成管涌溃坝等严重后果。以瀑布沟心墙土石坝为原型开展坝体渗流大型水槽模型试验,并结合有限元数值模拟方法研究高渗透区对坝体内部渗流场和渗流稳定性的影响。试验表明高渗透区域将改变心墙的渗流场,成为优势渗流通道,导致高渗透区域附近孔压值大幅上升,同时高渗透区域的存在将显著提升坝体渗漏速率。试验与模拟结果一致表明,随着高渗透区域逐步上移,高渗透区所在位置处的孔隙水压力增大,坝体渗漏量减小。高渗透区和心墙的渗透系数增加都会使心墙孔压值和渗漏量增加;随着高渗透区的渗透系数的增大,心墙坝渗流稳定性系数降低,导致坝体稳定性下降;随着心墙渗透系数的增大,高渗透区水力梯度略微减小,但心墙整体临界水力梯度下降,坝体稳定性降低。所得结论可为基于监测数据反演分析心墙的质量问题和评估坝体的安全性能提供依据。     

海相沉积淤泥复合固化强度的试验研究

针对现有淤泥固化试验采用的固化剂相对单一的问题,为了系统研究多材料固化滨海沉积淤泥强度特性,以唐山南堡典型滨海沉积淤泥为研究对象,通过对比单掺、双掺及三掺等固化剪切强度,结合粉煤灰废物利用问题,系统研究了水泥、生石灰及粉煤灰等不同固化剂组合对滨海相沉积淤泥固化强度的影响。结果表明:不同固化剂对滨海相沉积淤泥抗剪强度影响的差异较为明显,抗剪强度基本随掺加固化剂的种类增加而增加,掺加6%生石灰、10%水泥和6%粉煤灰28 d龄期的固化淤泥抗剪强度最高,其黏聚力为238.4 kPa、内摩擦角为32.94°;抗剪强度指标的提高随龄期的变化存在差异,即淤泥单掺生石灰抗剪强度指标的提高主要在养护后期,施工中可适当增加闷料时间以使生石灰和淤泥颗粒反应充分;采用水泥来固化淤泥可在短期内明显提高强度,在高含水率的淤泥材料施工中有更好的工程效果;固化剂掺量相同情况下,抗剪强度随着龄期增长而增加。研究成果对滨海沉积淤泥的固化和工程应用具有参考价值。     

波形钢腹板PC组合箱梁桥面铺装力学特性分析

结合郑州市陇海路主线高架桥工程,针对波形钢腹板PC组合箱梁桥面沥青铺装结构,利用ANSYS软件建立三维有限元计算模型,对铺装层厚度、铺装层弹性模量、车辆荷载、汽车冲击力等影响桥面铺装受力的因素进行敏感性分析,同时分析温度效应对铺装结构的影响。研究结果表明:车辆荷载对铺装层受力影响显著,且各应力与轴载大小基本成线性关系; 铺装层厚度与弹性模量对铺装层受力有一定影响; 汽车冲击力对铺装层受力影响较大; 温度变化会使铺装结构产生较大的温度应力。     

简支薄壁箱梁自由振动的摄动法解析解

为研究简支薄壁箱梁中剪力滞效应对结构动力特性的影响,基于模态摄动法提出了一种求解薄壁箱梁自由振动的新方法.该方法以相同跨度等截面欧拉梁的频率和模态为Ritz基函数,将箱梁自由振动的微分方程组转化为一组非线性代数方程进行求解.对于简支箱梁,可进一步将代数方程组简化为一元二次方程,从而得到精确的特征值和特征向量.在此基础上,利用所得箱梁振动模态的解析表达式,提出了模态剪力滞系数的概念,从而建立了箱梁固有频率和剪力滞效应之间的关系.随后研究了模态剪力滞系数随跨宽比、翼板抗弯刚度和截面抗弯刚度之比的变化规律.计算结果表明:简支梁腹板处剪力滞系数最大且大于1,为正剪力滞效应;随着模态阶数的增加、跨宽比的减小和翼板抗弯刚度和截面抗弯刚度之比的增大,剪力滞效应呈现增大的趋势.     

Characterization of polyhydroxyalkanoates synthesized in activated sludge using three carbon sources

Polyhydroxyalkanoates(PHAs) were synthesized in activated sludge using three types of carbon sources (sodium acetate,sodium propionate and sodium butyrate), and their characterization were studied. It was shown that the content of PHA synthesized by microorganisms in activated sludge were different. The biggest synthetic amount up to 36.7% of VSS was obtained when sodium acetate was used as carbon source. The polymer yield was lower when using sodium propionate as the carbon source than when using others, with 25.1% of VSS, while resulted in an increase of hydroxyvalerate(HV) units produced. The structure and thermal properties of extracted biopolymers were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and themo-gravimetry (TG).     

浙东运河闸坝控制工程及其技术特征研究

浙东运河是中国大运河的重要组成部分、是内河水运网络与海运联接的纽带。与大运河其他河段相比,浙东运河水系水文、控制工程有其鲜明特点。本文基于水利工程科技史的视角,对浙东运河水系构成及分段特点、浙东运河控制工程分布、闸坝工程型式与功能特征及其原因进行了系统分析,对浙东运河宁波段极具特色的闸坝功能划分特征、闸坝结合的工程型式产生及其技术特点进行了考证、分析,从中国大运河整体视角审视浙东运河水利工程遗产的特点及其科技价值。     

照片数量对SfM动床河工模型地形三维重构的影响研究

SfM是摄影测量领域近年来飞速发展的三维场景重构技术,目前已在地貌勘测、文物勘察、冰川演化、岩石勘探、土壤侵蚀等研究领域开展了大量尝试和应用,而在河工模型方面的应用研究尚处于起步阶段。本文开展了输入照片数量对SfM法动床河工模型地形三维数字高程地形(DEM)重构精度影响研究,采用4个不同视角对河工模型动床冲淤地形进行拍摄,选取不同数量照片作为输入开展SfM法三维地形DEM重构,然后将每组DEM重构结果与传统测针法测量进行对比。结果表明,当照片数量较少时,增加照片数量可改善SfM重构精度,但当照片数量较多时,虽可为SfM提供更多的床面变化图像信息,但同时带来由于特征点成像变化而引起的误匹配现象,反而可能导致SfM重构精度下降。鉴于不同动床模型的模型沙和光照等外部条件不同,实际应用时须针对不同模型的特点进行深入对比和分析,选取合理的照片张数开展SfM法动床冲淤地形测量。     

Physical and mechanical properties of sandstone containing a single fissure after exposure to high temperatures

In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different temperatures.Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing fissures.The results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties.When the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened.The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack failure.Tensile and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.     

青稞挤压糊化粉的研制

以青稞粉为原料,采用双螺杆挤压改性方法加工速食营养粉,研究挤压温度、螺杆转速和物料水分对物料品质的影响规律,并通过二次旋转正交组合实验（响应面实验）,优化营养粉工艺参数.结果表明,物料水分、螺杆转速和挤压温度对于青稞营养粉产品品质影响显著（P＜0.05）.响应面试验得出速食营养粉的较优加工条件：螺杆转速290 r/min,温度165℃和水分含量16.5％.在此优化条件获得青稞预糊化粉的各项指标为：膨化度3.14,吸水指数5.92,容重0.53,碘呈色度5.44.     

Characterization of microwave and terahertz dielectric properties of single crystal La2Ti2O7 along one single direction

New generation wireless communication systems require characterisations of dielectric permittivity and loss tangent at microwave and terahertz bands. La₂Ti₂O₇ is a candidate material for microwave application. However, all the reported microwave dielectric data are average value from different directions of a single crystal, which could not reflect its anisotropic nature due to the layered crystal structure. Its dielectric properties at the microwave and terahertz bands in a single crystallographic direction have rarely been reported. In this work, a single crystal ferroelectric La₂Ti₂O₇ was prepared by floating zone method and its dielectric properties were characterized from 1 kHz to 1 THz along one single direction. The decrease in dielectric permittivity with increasing frequency is related to dielectric relaxation from radio frequency to microwave then to terahertz band. The capability of characterizing anisotropic dielectric properties of a single crystal in this work opens the feasibility for its microwave and terahertz applications.