泥石流启动试验的数值模拟研究

采用离散元颗粒流程序PFC3D(Particle Flow Code)对泥石流启动过程的模型试验进行数值模拟研究.考虑泥石流启动过程中砂土的非饱和特性,在前期研究的基础上对模型进行改进,利用微小颗粒模拟水团,并通过设置黏结模型模拟土颗粒间的基质吸力.将数值模拟结果与室内模型试验进行对比分析,分析得出泥石流的启动表现为后部土体推挤前部土体快速下滑.非饱和状态下,颗粒间的基质吸力提供了一定的土体强度,当渗透力和重力引起的下滑力克服这种颗粒间的黏结力时,土体由非饱和状态逐渐转变为饱和状态,泥石流才会启动.与原有未考虑非饱和特性的数值模拟方法对比,结果表明,使用PFC3D并考虑土体非饱和特性,可以更接近地模拟流滑型泥石流的破坏形态和启动过程.     

岩体隧洞损伤破坏过程实验及其颗粒流数值模拟

在以往有关节理模型实验和数值模拟的研究基础上,设计了几组含孔洞节理模型材料的压缩实验,并采用颗粒流软件Partide Flow Code(PFC2D)对模型实验过程进行数值模拟.以模型实验应力-应变曲线与数值模拟的曲线吻合作为PFC细观力学参数选取的准则,并利用获得的力学参数对含孔洞节理岩体破坏过程进行数值再现.分析了...     

不同埋深盾构隧道开挖面稳定问题数值模拟

通过对照物理模型试验,采用二维颗粒流程序(PFC2D)对不同埋深和不同密度条件下的盾构掘进过程进行数值模拟,从而分析开挖面前方土体破坏机理.首先通过研究支护力和地表沉降的变化规律,将模型箱试验结果和数值模拟结果进行对比分析,分别确定了极限支护力;利用二维颗粒流程序对土拱效应进行研究,揭示了开挖面前方土体的失稳破坏机理.结果表明,支护力和地表沉降的变化规律都可分为2个阶段,且不受埋深条件的影响;发生局部失稳破坏后,土拱继续向上发展最终导致整体失稳破坏;埋深比较小时,未能形成土拱,而埋深比较大时,滑动区与土拱区随埋深比的增大而增大.数值模拟结果与模型箱试验结果基本一致,验证了采用纵面进行颗粒流模拟的可行性,因此可利用PFC2D进行深入颗粒流模拟.     

自然崩落采矿法的颗粒流数值模拟

以自然崩落采矿法为研究对象,利用二维颗粒流数值模拟(PFC2D)的原理和方法,研究了自然崩落法矿体崩落规律. 以某镍铜矿的地质条件及矿岩物理力学性质为依据,采用数值模拟的方法分析了自然崩落法的崩落规律. 结果表明:PFC2D模型在分析自然崩落过程中力学机理的同时,能有效地模拟自然崩落法采矿过程,并且能直观地给出矿体在崩落过程中各种参数的具体形态变化. 利用PFC2D模型预测该镍铜矿自然崩落法初始崩落拉底半径为10 m,连续崩落的拉底半径为22 m,有效地指导该矿自然崩落法的放矿.     

三峡库区龚家方2号斜坡破坏过程离散元数值模拟

以2008年11月三峡库区龚家方2号斜坡破坏问题为基础,采用离散元软件PFC2D对此斜坡进行模拟,模拟结果表明,三峡水库蓄水后,斜坡上覆崩坡积层会沿着岩土分界面向下滑动;整个滑动过程可以分为底端变形、上段及中段垮塌、整体滑动、固化稳定等4个阶段,其中底端变形形成的"鼓包"是否破裂是斜坡启动的关键;斜坡的滑动速度在初始阶段速度会迅速增大,之后缓慢减小,直至稳定。将模拟结果与观测资料对比分析,与实际破坏情况一致,说明二维离散元软件PFC2D能够较好地模拟三峡库区龚家方2号斜坡破坏过程。     

三峡库区龚家方2号斜坡破坏过程离散元数值模拟

以2008年11月三峡库区龚家方2号斜坡破坏问题为基础,采用离散元软件PFC2D对此斜坡进行模拟,模拟结果表明,三峡水库蓄水后,斜坡上覆崩坡积层会沿着岩土分界面向下滑动;整个滑动过程可以分为底端变形、上段及中段垮塌、整体滑动、固化稳定等4个阶段,其中底端变形形成的“鼓包”是否破裂是斜坡启动的关键;斜坡的滑动速度在初始阶段速度会迅速增大,之后缓慢减小,直至稳定。将模拟结果与观测资料对比分析,与实际破坏情况一致,说明二维离散元软件PFC2D能够较好的模拟三峡库区龚家方2号斜坡破坏过程。
     

水-岩相互作用对砂岩劣化效应的离散元模拟

以三峡库区消落带典型砂岩为研究对象,通过室内单轴压缩试验来获得水-岩作用对岩样的力学性质的劣化规律,并利用PFC2D离散元软件模拟单轴试验应力-应变曲线与室内水-岩作用试验曲线相符合的方式,来研究水-岩作用下三峡库区典型砂岩的微观力学参数的变化规律,揭示水-岩作用下岩石宏观力学性质的劣化机理.结果表明:在长期水-岩作用下,PFC2D数值模拟的细观参数变化规律与室内试验岩石的宏观力学参数的劣化规律基本一致;模拟得出的应力-应变曲线与室内试验结果匹配良好;数值试样的破坏模式变化规律性与室内试验的也完全一致.说明PFC2D数值模拟能够很好地模拟水-岩作用对砂岩的劣化效应,并反应岩石真实的劣化规律,同时也验证了水-岩作用对砂岩的劣化效应的显著性.     

基于颗粒流理论的煤与瓦斯突出数值模拟研究

针对煤与瓦斯突出机理的复杂性,基于颗粒流离散元理论,利用PFC3D(particle flow code)软件对煤体进行340组单轴压缩及巴西劈裂试验,建立了煤体宏观参数与颗粒流数值模拟所需细观参数之间的关系。基于寺河矿煤样单轴压缩和抗拉物理实验的实测宏观参数,推算出模拟煤与瓦斯突出所需的细观参数。在PFC3D流固耦合理论的基础上,利用PFC模拟软件进行了煤与瓦斯突出的数值模拟,再现了煤体的堆积过程。研究表明:在突出准备阶段,煤壁深部瓦斯压力较高,突出孔洞附近瓦斯压力梯度较高;发动及发展阶段,平衡状态被破坏,形成口小腔大的突出孔洞,破坏范围由巷道高度的中间位置向顶底板处扩展;在突出过程中,工作面前方煤体靠近煤壁的暴露面处的最大主应力向量逐渐偏离垂直方向,且应力向量连线形成一个凸向煤壁深部的圆弧。     

基于PFC模拟的坡面物源体启动机理

松散物源体含水率是反映降雨入渗程度的重要参数,对研究坡面泥石流的启动机理具有重要意义.以北京西山门头沟区清水镇扫帚港沟为例,在野外详细调查的基础上,采用室内直剪试验,研究了松散物源体在4种不同含水率水平下的强度特性,借助于PFC数值模拟手段,探讨了不同含水率下坡面泥石流启动的内在力学机制和外在表现形式.结果表明:松散物源体抗剪强度随含水率的增加而减小,随着含水率的增大,其内聚力和内摩擦角均呈减小的趋势.当含水率达到25%～30%时,松散物源体强度骤减,原有平衡状态被打破,坡趾碎屑物率先失去支撑牵引后部土体发生坍滑,产生由前至后的溯源破坏,并加速形成坡面泥石流.     

CO_2气爆含控制孔煤层裂隙演化颗粒流模拟

CO_2深孔预裂爆破是实现低透煤层瓦斯抽采的重要煤层增透技术手段。为更加准确地分析CO_2气爆作用下煤层裂隙演化规律,解决CO_2爆破过程存在非连续、大变形的问题,基于颗粒流方法(PFC)建立细观数值模型。通过将CO_2气爆应力波等效为半球面谐振波,分析CO_2气爆作用下煤层颗粒速度场;以颗粒膨胀加载法和动边界条件处理法,应用PFC2D构建二维数值模拟模型,分析CO_2气爆含控制孔煤层裂隙演化规律。结果表明:CO_2爆破应力波入射过程中,钻孔边界发生明显的动力效应,自孔周呈现推进式破坏区;煤层埋深增加,起裂压力增大,主裂纹形成后裂隙扩展范围增大;设置控制孔能有效加速裂隙发育,裂隙扩展深度和影响范围均有显著增加。该模拟可以解释爆破应力波的传播规律和描述煤岩体的动力破坏过程。     

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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