增湿减湿对黄土湿陷性的影响研究

黄土湿陷性的研究主要局限于狭义浸水饱和后的最终沉降量;但实际工程中常遇到的是不同增湿减湿含水率产生的广义湿陷,所以研究不同增湿减湿含水率对黄土湿陷性的影响更具实际意义。通过验测定由同一土桶制备的原状、增湿和减湿试样的含水率、湿陷系数和压缩量,并结合现有相关理论对数据进行统计、对比和分析,得出不同含水率的增湿、减湿对黄土湿陷性的影响规律。结果表明:在相同条件下,湿陷系数随增湿后含水率的增大而有明显的减小,初始含水率较低比初始含水率较高对湿陷性影响大;试验所取土样的峰值压力为100 k Pa左右,增湿界限含水率大概为26%;在相同条件下,增湿减小了黄土的湿陷量,却增大了压缩量;减湿减小了黄土的压缩量却增大了湿陷量。     

基于湿陷性和震陷性的黄土微结构

试验通过对原状及湿陷和震陷土样的微结构SEM图像的观测和分析,定量研究力和水两个外因作用下黄土的孔隙大小,数量及其分布规律的变化,通过不同外因的作用效果分析黄土结构特性.结果表明黄土震陷后孔隙较湿陷后大,认为胶结作用极易因浸水而软化破坏,胶结作用愈强,黄土发生湿陷的可能性愈大;但是胶结作用可以抵御外力作用,使黄土不容易...     

旱区陡坡黄土的低压力抗剪强度特性试验研究

黄土强度指标的准确确定是地质体稳定性分析的基础依据。以延安地区某边坡上更新统黄土为研究对象,利用改进的直剪仪,开展不同初始含水率、密度、干湿循环条件下原状与重塑黄土的低压力抗剪强度试验,研究原状与重塑黄土的低压力抗剪强度及抗剪强度指标随初始含水率、密度及干湿循环次数的变化规律,建立黄土的低压力抗剪强度指标与初始含水率、密度及干湿循环次数之间的函数关系。结果表明,黄土的低压力抗剪强度与初始含水率的关系可采用指数函数描述,与土体密度和干湿循环次数的变化关系可采用线性函数描述;原状与重塑黄土的黏聚力、内摩擦角与初始含水率之间呈负相关,且原状黄土抗剪强度指标高于重塑黄土;黄土的抗剪强度指标随土体密度增加而显著提高,随干湿循环次数增加呈明显减小趋势。     

冬灌区黄土湿陷性的反复冻融效应

为了探索冻融循环对冬灌区黄土湿陷性的作用规律,结合宁夏气候和黄土区域性特点,应用封闭单向冻融法,试验研究了冬灌区黄土湿陷性的反复冻融效应。试验结果表明:冻融使黄土的湿陷性增大,冻融引起的湿陷系数增量随冻融循环次数的增加而增大,在冻融循环12次后基本达到稳定,二者间存在相关性很好的双曲线关系。在含水率为定值14.0%时,黄土湿陷系数的冻融效应随干密度的增大逐渐增大;在干密度为定值1.45 g/cm~3时,黄土湿陷系数的冻融效应随含水率的增大呈先增大后减小的趋势,最不利含水率约为22.0%。湿陷系数的冻融效应存在最不利含水率,黄土工程应尽量避免在最不利含水率下受冻,尤其是密实度大的压实黄土。     

磐安结构性黄土的构度及动强度衰减特性

 以磐安黄土为样本,基于无侧限单轴抗压试验得到的磐安黄土构度指标,分析了原状黄土与重塑黄土的结构性差异;通过动三轴试验,对原状黄土、重塑黄土在天然含水率、饱和含水率条件下的动强度衰减特性进行了对比研究。结果表明,天然含水率的原状黄土及重塑黄土均具有较强的结构性,原状黄土的结构性更强,其动强度明显高于重塑黄土的动强度;虽然饱和过程使得原状黄土的动强度大大降低,但饱和原状黄土的动强度仍高于饱和重塑黄土的动强度,且饱和原状黄土的动孔压增长趋势明显慢于饱和重塑黄土;具有较强结构性的黄土,其动强度曲线不会出现归一化。     

湿陷性地区强夯地基检测与地基施工

湿陷性黄土的最大特点是大孔隙、欠压密,遇水后颗粒及团粒间的天然粘结强度急剧降低,引起原状结构破坏,土柱相互错位并重新排列,从而引起湿陷,强夯法处理涅陷性黄土地基是一种有效的办法。本文对湿陷性地区强夯地基检测与地基施工进行了研究。     

重塑黄土的湿陷性与微观试验研究

黄土广泛分布于中国西北地区。随着人类社会的发展,越来越多的工程项目需要在黄土地区展开。黄土的特殊性质导致其具有水敏感性,这种水敏感性的典型表现便是湿陷;而黄土的湿陷与其微结构的变形过程紧密相关。以重塑黄土为研究对象,在反复湿陷试验的基础上,对不同含水量、不同湿陷次数的重塑黄土试样进行CT扫描与电镜扫描等微观试验,结合IPP图像处理软件对微观试验结果进行定性与定量分析,得到重塑黄土湿陷性与其微结构的关系。认为:(1)黄土的自重湿陷系数主要受其含水量的影响,即含水量越小,越容易湿陷;且当含水量为6%时试样具有二次湿陷性;不同含水量的试样随着湿陷次数的增加,湿陷系数逐渐减小,且经过3次湿陷后其自重湿陷系数均趋于一个稳定的值;(2)随着湿陷次数的增加,土体中大的团粒与大孔隙逐渐消失,土体密度逐渐均匀,颗粒丰度逐渐变大,孔隙颗粒面积比逐渐减小,颗粒定向角度逐渐趋于水平;(3)黄土发生湿陷的主要原因是水的浸润或溶滤作用导致其结构强度的弱化,使大的团粒逐渐崩解成小颗粒填充到孔隙中造成土体压密。     

湿陷性黄土隧道基底加固处理技术

湿陷性黄土是由于黄土在一定的压力作用下受水浸湿后,土的结构迅速破坏而产生显著的附加下沉,并且强度也随之降低的一种特殊结构。黄土的湿陷性有自重湿陷和非自重湿陷两类。在我国60%以上的黄土地区为湿陷性黄土,而且大多出现在地表浅层,黄土地基的湿陷性特征会给即将修建的结构物带来不同程度的危害,可能会使结构物出现大幅度的沉降、裂缝、倾斜、甚至影响其安全和寿命。因而,必须对其进行处理后方可使用。另外湿陷性黄土隧道多位黄土土质结构疏松,孔隙、垂直节理发育,地基承载力不高,具有湿陷性,在遇水侵蚀或较大荷载的作用下,隧道则产生较大沉降。其基底承载力很难满足要求,通常需对基底进行加固处理,湿陷性黄土隧道基底处理常用的方法有水泥挤密桩和树根桩等。     

晋南地区大厚度湿陷性黄土场地现场浸水试验研究

结合大同—西安客运专线,对晋南地区大厚度湿陷性黄土进行了现场浸水试验研究;并在典型地区(山西省运城市闻喜县)采集大量原状土样,进行室内试验,获得了一系列黄土力学参数。试验结果表明:该地区黄土属Ⅱ级自重湿陷性黄土;不同深度土层均会出现多次湿陷,湿陷次数随土层深度的增加而减少;在距离试坑边缘不同位置处含水量不同,同时,在深度方向上,10 m以内水分入渗较为容易,10 m以下入渗较为困难;现场实测场地黄土的自重湿陷下限为10 m,和计算得到的场地黄土自重湿陷下限基本吻合;水分扩展形态呈喇叭形,扩散角大致在41°~45°变化;裂缝呈连续环形分布,宽度深度都较小;埋设的张力计和压力计验证了场地黄土湿陷性等级的正确性。该研究对大西客运专线建设具有现实指导意义和应用价值。     

冻融循环对结构性黄土构度指标影响研究

为研究冻融循环对结构性黄土构度指标的影响,以山西阳曲一号隧道黄土为研究对象,基于综合结构势和构度概念为理论基础,对不同含水率黄土进行了不同冻融循环次数的无侧限抗压试验。试验表明:原状土样和重塑土样在含水率变大的过程中,单轴抗压强度均减小,且呈现出相同的变化趋势,而原状土样的无侧限单轴抗压强度均高于同含水率重塑土的无侧限单轴抗压强度,有着明显的结构强度。黄土的无侧限抗压强度和构度随着含水率和冻融循环次数的增加而减小的主要原因是由于黄土的结构性被土中水和冻融循环综合作用破坏的结果,该研究可为季节性黄土地区隧道建设提供科学依据。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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