Experiment and modeling of soil-water characteristic curve of unsaturated residual soil

土-水特征曲线是指基质吸力与含水率或饱和度的关系曲线。土-水特征及其相关数学模型可用于非饱和土性质如渗透系数和抗剪强度模型的建立。通常,土-水特征曲线仅有脱湿曲线。笔者详细讨论了初始含水率、干密度、竖向应力及干湿循环对脱湿曲线的影响。采用滤纸法测试了厦门地区残积土的土-水特征曲线(SWCC)及滞回环。结果表明,初始含水率对SWCC影响较小,最优含水率干侧试样SWCC的进气值小,滞回环小;湿侧试样的进气值大,滞回环大;最优含水率试样的滞回环居中。初始干密度对SWCC有显著影响,低干密度试样SWCC进气值小,脱湿速率快;高干密度试样SWCC进气值高,脱湿速率低。滞回环的大小随着初始干密度的减小而增大。不同竖向应力下SWCC变化较大。随着竖向应力的增加,进气值增大,脱湿速率减小,滞回环减小并趋于稳定。第1次干湿循环对SWCC影响最大,随着循环次数的增加,进气值减小,滞回环减小并趋于稳定。由于残积砂质黏性土SWCC的过渡区和残余区不易区分,残余含水率难以确定,因此,提出5种剔除残余含水率参数的修正SWCC模型,计算分析得出,修正gArdnEr模型最适合厦门地区残积土的SWCC建模。The soil-water characteristic curve(SWCC) is defined as the relationship between the suction and the water content or degree of saturation.The soil-water characteristics and related mathematical models can be used to model the unsaturated soil properties such as the permeability and the shear strength.Conventionally, only the drying soil-water characteristic curve of soil is determined.In this work, the influences of initial water content, initial dry density, the vertical stress and drying and wetting cycles are examined and discussed in detail.The SWCCs and hysteresis loops of residual soils in Xiamen were obtained by the filter paper method.The results show that the initial water content has negligible effect on SWCCs.The specimen at the wet of optimum moisture content(OMC) has the higher air entry value and the larger hysteresis loop than that of the soil specimen at the dry of OMC.The specimen with OMC lies between them.While, the initial dry density has considerable influence on SWCCs.The specimen at lower initial dry density exhibits smaller air entry value and higher rate of desorption than that of the specimen at higher initial dry density.The size of hysteresis loop decreases as the initial dry density increases.The specimens subjected to different vertical stresses have different SWCCs.The higher the applied load on the specimen, the higher the air entry value, the higher the rate of desorption, the smaller the size of hysteresis loop.In the drying and wetting process, the size of hysteresis loop has been substantially affected by the first drying and wetting cycle.With the increasing of drying and wetting cycle, the air entry value and the size of hysteresis hoop decrease.Since the features of soil-water characteristic of sandy clay are not well defined especially for the residual state of saturation, which desaturates continuously without a distinct break point, the residual suction or residual water content, one of the key parameters in the mathematical models of SWCC, is not well defined.As a result five improved models without the residual water content are proposed to describe the SWCCs of residual soil.The improved Gardner model has been found to be the most suitable model for all SWCCs of the residual sandy clay in Xiamen.国家自然科学基金项目(No.51209180

VARIATION of THE SHEAR STRENGTH of XIAMEN UNSATURATED RESIDUAL SOILS WITH WATER CONTENT

采用普通应变控制式直剪仪对非饱和残积砂质黏性土和黏土进行慢剪强度试验,试验结果表明,砂质黏性土的黏聚力和内摩擦角均对含水量变化敏感,黏聚力随含水量的变化呈二次抛物线关系,内摩擦角随含水量增大呈幂函数减小;含水量对黏土强度的影响主要是降低了黏聚力,对内摩擦角影响很小。黏聚力随含水量的增加呈指数减小。针对上述变化规律,分别建立实用的强度经验公式,避免了吸力量测和计算困难。对提出的强度公式进行试验验证,计算预测强度并与实测强度相比较,结果表明不同竖向应力条件下,高竖向应力下强度的预测精度更高。2类残积土的强度公式预测精度均满足工程要求,可为工程实际应用提供参考。Shear strength of unsaturated sandy and clay residual soils were conducted by consolidated-drained shearing method using the conventional strain controlled direct shear apparatus.Results show that the shear strength of two kinds of residual soils decreases with increase of water content.The initial water content has effect on both cohesion and frictional angle of sandy clayey soils.The relationships between cohesion,frictional angle and water content of sandy clayey soils are quadratic and power respectively.While the initial water content has negligible effect on friction angle of clay.The considerable influence of increasing water content on shear strength of residual clay is decreasing the cohesion.The variation of cohesion with water content can be described by an exponential relationship.On the basis of variation of shear strength indexes with water content,two new strength formulas of unsaturated sandy clayey and clay were established without suction component and were demonstrated by further tests.Comparisons of the calculated and measured shear strength show that the accuracy of the prediction is higher under high vertical stress.Two strength formulas can provide the good estimation of shear strength of unsaturated residual soils in Xiamen for engineering application.福建省自然科学基金资助项目(2014J01208

管棚保护下框架桥顶进工程高程控制分析

大直径管棚保护下直接顶进预制箱涵技术是近年来国内发展起来的一种全新的施工技术,但其难度大,理论发展不完善,可借鉴的经验少.依托南昌市新龙岗大道下穿向莆铁路工程,根据实际工程情况建立力学分析模型,计算框架桥下钢管的受力,并根据钢管的受力情况假定钢管为Winkler弹性地基梁,运用弹性地基梁理论建立钢管挠曲微分方程并求解该微分方程,从而计算出框架桥顶进过程中的钢管挠曲变形,进而确定顶进过程中框架桥高程偏差情况.理论分析表明,底排管棚的支撑和引导作用有助于框架桥推进,并能有效遏制框架桥\"栽头\"和\"抬头\"现象,对于现场工程施工具有很好的参考价值.福建省自然科学基金(2014J01208

Design and Research of Optical Structure for the Visible Light in the Coaxal

在激光技术的应用中,常常要对激光束实现某种实用空间界面的准确定位和聚焦。聚焦和定位的困难在于能够透过红外或紫外辐射的光学材料往往无法透过可见光,使得各种激光束的聚焦光斑的空间定位设计成为困难,阻碍了激光技术的应用。为此,结合课题的科研工作,研究设计了二种性能各异的同轴可见光导引光路结构,并在医疗临床应用中,获得了满意的效果。The main difficulty of pointing out of the visible light in the coaxal is can be transmission the optical material of infrared radiation but often unable to transmission.Given the space fixed position of focusing facula of lasers beam in difficulty.Same of the kinds of coaxied light system of point out are designed,through the clinical application of the exact of fixed position and quick and continues variable and the safe operation is reliable.The devolopings and applications of whole mechine system of the a way of technology is supplied for.福建省科技计划项目(No.2001I017)资

Tracking of time-varying underwater acoustic channels based on multipath parameter model and hybrid optimization

针对海洋水声信道的稀疏特性,将多径水声信道冲激响应建为一个由各多径分量的时延和幅度组成的多径参数模型.该模型中输入信号向量产生的响应与多径时延参数呈非线性关系,与多径幅度参数呈线性关系.基于此特点,针对海洋水声信道的时变特性,分别采用进化算法和lMS自适应算法对模型中的多径时延和幅度参数进行混合寻优,从而解决时变信道条件下模型参数寻优困难的问题.仿真及海试信道跟踪实验结果表明:采用多径参数模型可降低模型寻优对象的维数,减少运算复杂性,提高估计效率;采用混合优化算法可减少多径参数模型的非线性寻优的复杂度,与进化算法相比,该算法具有更优越的时变信道跟踪性能.As for the structural sparsity of impulse response of an underwater acoustic multipath channel,a multipath parameter model consisting of time delays and amplitudes of multipaths is proposed.The response of the multipath parameter model is nonlinear with the time delay parameters,but linear with the amplitude parameters.Based on this characteristic,as for the time-varying character of the underwater acoustic channel,a novel hybrid optimization method is developed to facilitate the optimization of the parameters of the time varying channel model;that is,the evolutionary algorithm and the least mean square algorithm are applied to address the model's time delay parameters and amplitude parameters,respectively.The results of simulation and sea-trial data demonstrate that the multipath parameter model can decrease the orders of the optimized parameters,reduce computational complexity and improve estimation efficiency.Besides,the hybrid optimization method can reduce the complexity of nonlinear optimization of the multipath parameter model,and compared with the classic evolutionary algorithm,it has a better tracking performance of the time-varying channel.国家自然科学基金资助项目(10704063);福建省高等学校新世纪优秀人才支持计划资助项目(NCETFJ-06XMUCOE

干湿循环下花岗岩残积土抗剪强度及边坡稳定性分析

为研究干湿循环对花岗岩残积土抗剪强度特性和抗剪强度参数的影响,分析花岗岩残积土边坡的稳定性,改进了常规的单元试验方法.以整个花岗岩残积土边坡为试验对象进行干湿循环模拟,在每次循环后直接在边坡坡面上切取花岗岩残积土试样进行直剪试验.在此基础上,利用有限元软件ABAQUS对一实际边坡进行了干湿循环的数值模拟,在每次循环模拟前对上一次模拟结果进行分析,将等效塑性应变较大区域的土体强度进行适当折减,分析每次循环后花岗岩残积土边坡的应力应变、稳定性以及塑性变形.试验结果表明:花岗岩残积土的抗剪强度随干湿循环次数、循环幅度的增加而减小,其中黏聚力值衰减明显,内摩擦角的变化相对较小,在3～5次干湿循环后抗剪强度趋于稳定;通过数据分析得到干湿循环的黏聚力公式,进一步得到了干湿循环条件下花岗岩残积土的抗剪强度公式;干湿循环作用导致边坡稳定性降低,安全系数减小,且第一次干湿循环后安全系数的降幅最大

Study on the Characteristics of Loss Ratio and Loading-unloading Response Ratio before Rock Failure

以多种岩石循环加卸载声发射试验为基础,针对岩石损耗比和加卸载响应比特性进行了研究,探索岩石在受载过程中的内部损伤演化和破坏前兆特性。结果表明,在; 循环加卸载下角岩等三种岩石损耗比变化特性一致:低应力水平阶段损耗比较大,呈明显下降趋势;中等应力水平阶段比值下降趋势较平缓;高等应力水平阶段比值; 趋于稳定,在0.08 ~; 0.10时,试样破坏。而钨钼矿等三种岩石加卸载响应比变化特性一致:低应力水平阶段卸载时几乎没有声发射,加卸载响应比较大;中等应力水平阶段卸载时声; 发射较活跃,比值下降至1左右;高等应力水平阶段卸载时声发射很活跃,当比值重新大于1时,试样破坏。试验结果都体现了岩石内部损伤从很小到稳定扩展再到; 不稳定扩展的过程。可见,损耗比和加卸载响应比的变化特性均可用于评价岩石损伤情况,也可用作岩石破坏预测的参考依据。On the basis of the acoustic emission for rock under cyclic loading and; unloading,the characteristics for the loss ratio and loading-unloading; response ratio of rocks is studied,and the evolution of the internal; damage in the course of loading and the precursor characteristics of; failure are explored. The results show that the variation; characteristics of loss ratio of three kinds of rocks like hrnfelswere; are consistent under loading and unloading conditions; The loss ratio is; relatively large in the low stress level stage,and it shows a clear; downward trend. After entering the medium stress level,the ratio; decreases with a relatively flat trend. In higher stress level,the ratio; tends to be stable,and the specimen fails at 0.08~ 0.10. At the same; time,the variation characteristics of loading-unloading response ratio; of three kinds of rocks like tungsten and molybdenum ores are; consistent. There were almost no acoustic emission at the unloading; stage in the low stress level stage,and the loading-unloading response; ratio were relatively large. Acoustic emission was more active at the; unloading stage in the medium stress level,and the ratio dropped to; about 1. In higher stress level,acoustic emission was very active at; unloading stage,and the specimen failed when the ratio increased over 1; again. The results reflect the process of rock internal damage from; small to steady expansion and then to unstable expansion. So the; variation characteristics of loss ratio and loading-unloading response; ration can be used to evaluate the damage of rock,and also can be used; as a reference for prediction of rock failure.国家十二五科技支撑计划项

The research of the reference value of urinary mercury for 0-6 years old children in coast area

目的通过对厦门市0~6岁儿童尿汞水平调查,了解厦门市儿童汞暴露水平。方法根据行政区划以及儿童人数分布从全市选取代表性的8个社区,进行分层随机抽样,共收集到1076例0~6岁儿童尿样。样本采用随意尿,每个儿童统一使用聚乙烯塑料瓶收集不少于5 M l尿样,尿样统一采用dMA-80自动测汞仪测定。结果儿童尿汞测定值呈偏态分布,因此使用几何平均数表示儿童尿汞的平均水平。男女儿童尿汞几何平均值分别为0.77μg/l和0.74μg/l,经非参数T检验比较,差异无统计学意义(P>0.05)。0~1岁、2~3岁和3~6岁3个年龄段的儿童尿汞几何平均值分别为0.74μg/l、0.75μg/l和0.78μg/l,经非参数T检验比较,差异无统计学意义(P>0.05)。对1076名儿童尿汞值分析得出尿汞的几何平均值为0.76μg/l,95%置信区间0.70~0.81μg/l。结论厦门市0~6岁儿童的尿汞水平的调查结果可以为国内沿海城市0~6岁儿童汞暴露水平的本底值研究提供参考。Objective To understand the mercury exposure level in 0-6 year-old children of Xiamen city through the survey.Methods A total of 1 076 healthy infants and young children aged 0-6 year-old were selected from 8 communities with stratified and cluster sampling method respectively.The spot urine samples of the children were collected( more than 5m L per child).The concentration of mercury was determined by DMA-80 automatic mercy instrument.Results The urine mercury values of the healthy children were in skewed distribution and the results were expressed in geometric mean.The urine mercury values for boys and girls are0.77μg / L and 0.74μg / L,respectively.There was no significant difference for the urine mercury values between boys and girls( P >0.05).Meanwhile,the urine mercury values for groups of 0-1 year-old,2-3 year-old,and 4-6 year-old were 0.74μg / L,0.75μg / L and 0.78μg / L,respectively.The urine mercury values among the three age groups had no significantly difference neither( P > 0.05).The upper 95 th percentile in 1076 urine samples was 0.85 μg / L,95% confidence interval was 0.70-0.81μg / L.Conclusion The average value of 0-6 year-old children's urine mercury level in Xiamen was close to those in the reports of two researches in Shenyang and Germany.Therefore,results will be helpful for the understanding of mercury exposure in 0-6 year-old children of Xiamen city

Synthesis of Ru(dpp)_3(ClO_4)_2 doped polyacrylonitrile nanoparticles and its applications in ratiometric pH sensing

采用乳液聚合法制备了掺杂有4,7-二苯基-1,10-邻菲咯啉钌(ru(dPP)3(ClO4)2)的聚丙烯腈纳米颗粒(ru-PAn).经扫描电子显微镜(SEM)表征,制备的ru-PAn的尺寸为135±15 nM,呈规则球型,尺寸分布均匀且在水中的分散性较好.实验考察了氧气、共存离子和PH值对其荧光性质的影响以及其荧光稳定性.以异硫氰根荧光素(fITC)为PH荧光指示剂、ru-PAn为参比信号,初步建立了一种比率荧光PH检测的方法.In this paper Ru(dpp)3(ClO4)2 doped polyacrylonitrile nanoparticles(Ru-PAN) were prepared using emulsion polymerization method.Morphology characterizations of the nanoparticles were performed using scanning electron microscope,the particle diameter was about 135±15 nm.The interference of the oxygen,coexisting ions,pH and photo-stability were investigated.A new ratiometric fluorescence pH sensing system was established via fluorescein isothiocyanate(FITC) as pH-sensitive dye and Ru-PAN as a reference.国家自然科学基金资助项目(20975085

厦门地区非饱和残积土抗剪强度的试验研究

非饱和残积土是厦门地区诸多填方工程的工程用土,而岩土工程的强度与稳定性问题都涉及到非饱和土的抗剪强度及其指标.采用滤纸法测定非饱和残积土的基质吸力,通过一系列的直接剪切试验,测定不同初始含水量状态下土的抗剪强度及其强度指标.试验结果表明:基质吸力随着含水量、体积含水量或饱和度的增加而减小.当含水量小于16%,体积含水量大于35%或者饱和度大于70%时,基质吸力对含水量的变化非常敏感.在低基质吸力区,抗剪强度随着基质吸力的增加显著增加,表观粘聚力随基质吸力的增大而线性增加;在高基质吸力区,强度随基质吸力的增加变化不大,表观粘聚力的增长速率减小.表观内摩擦角仅在基质吸力较小时增加而后可近似为某一定值