富水软弱地层矩形混凝土顶管施工地表沉降研究

随着城市隧道建设环境的日益复杂,很多矩形隧道不再具备明挖条件,而采用顶管施工,合理预测矩形顶管施工引起的地表沉降是工程成败的决定性因素之一.依托苏州地铁5号线某车站矩形顶管工程,建立基于随机介质理论的地层损失模型和基于弹性力学Mindlin解的计算模型,得到矩形顶管施工引起地表沉降的计算公式.选取K34断面,对比了现场实测数据与理论计算的结果.研究结果表明:建立的矩形顶管地表沉降预测模型能较准确地预测矩形顶管引起的地表沉降,其预测值和现场实测数据的误差仅为10.6％;地层损失引起的地表沉降是总地表沉降的主要组成部分,侧摩阻力与正面顶推力占比较小;理论预测曲线的沉降槽宽度与实际沉降槽宽度较为接近,约为2～3倍隧道埋深.     

矩形顶管管-土接触面状态及顶推力预估

天津地区采用较大直径的矩形顶管施工地铁车站出入口可借鉴的工程经验较为匮乏.考虑施工停顿、管体悬浮和减阻剂体积等因素的影响，提出了耦合有限差分法和顶力-顶程控制方法的顶推力计算模型，并应用于矩形顶管顶推力的预估.针对天津地层情况，采用该模型预估地铁车站出入口顶管施工中的顶力.现场试验与监测数据证明顶力预估模型的正确性，有助于顶管工作井后背墙的设计优化及长距离大直径顶管施工中继间的布置.     

砂土地层顶管施工土体变形规律三维数值分析

为得到顶管施工引起的土体变形分布规律、施工扰动范围和土体塑性区特征,以某污水干管顶管工程为依托,采用构建三维弹塑性有限元计算模型的方法,分别考虑正面推进力、地层损失和结构与土体的共同作用等因素对土体变形的影响。结果表明:仅地层损失作用下,管道周围2D范围内土体受扰动明显,推进面前后方土体均出现沉降,但推进面后方土体下沉趋势较前方土体幅度大;仅顶推力作用下,施工从横向和竖向对土体的扰动分别集中在管道周围1D和2D范围内,顶进面纵向前方2D范围内土体受扰动明显,推进面后方土体出现沉降,而前方的土体则出现隆起现象,但隆起值较小;在顶推力和地层损失2种因素共同作用下,地层损失是引起土体沉降的主要因素。通过以上分析认为砂土地层顶管管道周围2D范围内土体易产生位移,在施工中应引起重视,并采取一定措施减少其扰动程度。     

超大类矩形断面复合顶管施工力学性能研究

依托上海轨道交通14号线静安寺站工程，介绍了超大类矩形断面钢-混凝土复合顶管的结构构造、加工制作与施工监测方案，重点分析应力监测数据并结合数模结果揭示了管节在顶进及后续施工中的受力性能，以此来研究大埋深软土地层中新型超大断面顶管的施工力学特性．结果表明：对于顶管中的任一管节，钢板与纵向肋板的应力在该管节顶进初期与全钢管顶推完成时出现较大波动，而中间段基本稳定在某一数值，且钢板轴向受力相比环向受力对管节纠偏更敏感；同一顶管不同管节在施工过程中的应力和位移分布一致：应力分布较为均匀，峰值应力位于顶推面拐角附近；变形趋势为竖向内凹、横向小幅外凸，峰值形变位于竖向跨中；管节峰值应力随顶管推进逐步增大，但均未超过弹性极限，峰值形变保持稳定；钢板的环向应力由水土压力控制，应力分布为上部受拉、左右受压，轴向应力由顶推力控制，其中竖直方向上的轴向应力也受管节竖向偏转和外壁环向荷载的影响；纵向肋板的轴向应力在水平方向上由顶推力控制，在竖直方向上由外壁环向荷载控制；后续施工过程中，顶管受力相对稳定．影响范围方面：注浆加固对钢板和纵向肋板的受力均有较大影响；管节环向焊接主要对钢板的环向与轴向受力有较大影响；...     

水平布置的先行顶管对后续顶管顶推力的影响分析

以北京新机场线顶管工程为依托,针对水平布置的先行顶管对后续顶管顶推力的影响开展了现场试验和数值模拟研究,并对先行顶管的位置和数量进行了参数影响分析.研究结果表明,先行顶管对后续顶管侧摩阻力存在放大效应,增大顶管间距将导致该放大效应非线性减小.先行顶管的位置和数量对后续顶管侧摩阻力存在重要影响.在顶管间距为1.1倍钢管直径的情况下,当先行顶管位于后续顶管一侧时,侧摩阻力最大增长率为28.5％;当先行顶管位于后续顶管两侧时,侧摩阻力最大增长率达到41.9％.基于此提出了水平顶管施工中的顶推力群管效应理论,为大体量顶管顶推力的设计提供依据.     

深埋曲线钢顶管接触压力现场监测试验分析

为了研究深埋条件下曲线钢顶管接触压力分布和变化规律,以拱北隧道曲线顶管管幕工程为背景,通过对曲线顶管施工现场监测的接触压力进行分析.结果表明:顶进力随顶进距离的增加基本呈线性增长,且中粗砂地层单位面积摩阻力大于砂质黏性土地层;接触压力顶进时发生波动并增大,顶进停止后逐渐趋于平稳,在浮力和顶进力侧向分力作用下,管道顶部和底部的接触压力数值较为接近,且顶部接触压力略大于底部压力,水平位置管道弯曲内侧接触压力小于弯曲外侧;附加接触压力随着掘进面与监测断面距离减小而增加,机头穿过监测断面后,已顶管道水平位置附加接触压力减小,而顶部接触压力由于土拱效应反而持续增长.     

顶管电缆隧道施工对邻近建筑物和地下管线的扰动影响

采用离心机物理模型试验和有限元数值计算方法探究了软土地区顶管电缆隧道施工对邻近浅基础建筑物和地下管线的扰动影响,并提出修正Peck公式评估顶管施工对邻近浅基础建筑物的扰动影响.首先,通过离心机物理模型试验,定性分析了顶管电缆隧道施工过程中地层损失率变化对邻近浅基础建筑物和地下管线的影响;其次,将有限元数值计算结果与离心机试验数据进行对比分析,验证有限元计算的有效性;最后,通过有限元模拟结果提出用于评估顶管施工对邻近浅基础建筑物扰动影响的修正Peck公式,并与现场监测数据进行对比分析.研究结果表明:顶管电缆隧道施工对邻近浅基础建筑物和地下管线的扰动影响随着地层损失率的增大而增大,地下管线刚度的增加可以有效减小邻近顶管隧道施工的影响;有限元数值方法可以较好地评估不同地层损失率下顶管隧道的施工工况;修正Peck公式能较好地反映在软黏土区域内顶管电缆隧道开挖对周围地层产生的扰动影响.研究结果可为软黏土地区顶管电缆隧道的施工提供一定参考价值.     

双层顶管隧道施工引起的土体竖向变形规律研究

采用数值分析方法,研究了双层顶管隧道施工引起的土体竖向变形规律。研究表明:顶管隧道施工引起的地层移动主要是由于地层损失引起的。地层移动主要是垂向位移,其水平位移很小,可忽略不计。在垂直顶管走向上,地面沉降呈以顶管轴线为对称轴且开口向上的抛物线形状,其最大值发生在顶管正上方。在顶管施工过程中,先行施工的下层顶管引起的沉降约占总沉降量的80%;当上层顶管位置不变时,总沉降量随着下层顶管埋深的增大而线性增大;当顶管间距逐渐增大时,上层顶管开挖引起的沉降量与总沉降量之比逐渐减小,下层顶管引起的沉降量与总沉降量之比逐渐增大,下层顶管对上层顶管影响逐渐减弱。     

真实复杂地层大直径钢顶管三维数值模拟研究

为了揭示地表沉降与管周土体扰动沿顶进方向的真实变化规律,本文提出了真实复杂地层三维数值建模方法。依托某市北线引水工程隐患整改顶管工程项目,采用FLAC3D分析平台开展了真实复杂地层和简化均匀地层条件下的大直径钢顶管施工数值模拟研究。模拟结果及现场地表沉降实测结果对比表明：基于真实复杂地层模型的模拟结果与现场沉降监测结果吻合较好,能够准确反映地表沉降沿纵向的变化规律,而简化地层模型模拟结果与监测值差距较大。扰动分析表明顶管施工时会引起其上方地层的沉降变形和下方地层的抬升变形,其变形值大小与地层土体性质和分布有关。顶管上覆土体横向位移基本朝向顶管轴线,其变形受土体空间分布的影响较小,但顶管下部土体的横向变形受土体空间变化影响较大。地表沉降的横向影响范围为?5.3D（D为顶管直径）,且受土层分布影响较小,但地表沉降值受地层分布影响较大。     

负斜桩顶部水平受拉响应及p-y曲线特征试验研究

为研究倾斜桩的水平受拉响应特征,在模型砂土中设置0°、10°、20°倾斜桩及桩底嵌岩20°倾斜桩,桩顶施加水平拉力,拉力方向与倾斜方向相反,测试4根模型桩的水平位移、应变片与土压力盒应变,获得桩身水平位移、弯矩、土抗力和p-y曲线特征随倾斜角和桩底约束条件的变化规律. 结果表明：1）桩顶水平受拉时,随着倾斜角的增加,负斜桩顶部水平位移逐渐增大,弯矩峰值随之增大,而土抗力峰值逐渐减小,土抗力峰值点位置逐渐降低,单桩的水平承载力随之降低,抗弯能力减小;2）随着桩底约束程度的提高,负斜桩顶部水平位移减小,桩身弯矩峰值、土抗力峰值减小,单桩水平承载力增大,抗弯能力增强;3）水平荷载作用下,本模型的负斜桩破坏模式为“转动+弯曲”,转动点位置随倾斜角的减小或桩底约束程度的提高而下降;4）0°～20°负斜主动桩p-y曲线可采用p/pub= α（y/y50） β进行拟合,倾斜角与桩底约束程度对α影响不大,倾斜角对β值变化幅度影响较小,β值变化幅度随桩底约束程度提高而降低.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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