上海地区深基坑周围地面沉降特点及其预测

通过研究上海地区32个深基坑工程的监测数据,得到以下地面沉降特点:大多数地面沉降曲线呈凹槽型,存在沉降槽偏心距;最大沉降量δvm的变化范围在0.4δhm～1.9δhm之间(δhm为最大侧向位移),其平均值和最大侧向位移相等;所有基坑的支撑系统相对刚度都较大,支撑系统相对刚度对最大沉降量影响很小;抗隆起安全系数增大,基坑最大沉降量减小,同时绘制了基于抗隆起安全系数的最大沉降量预测曲线.最后,基于上海地区深基坑的沉降实测曲线特征,提出了考虑沉降槽偏心距的地面沉降预测方法,并结合四个工程实例进行了验证,结果表明,该方法预测精度较高,是一种实用的基坑周围地面沉降预测方法.     

砂土地区深基坑稳定性评价及力学效应分析

结合某地铁车站基坑开挖工程,基于基坑支护结构的现场实测数据,对排桩内支撑基坑支护体系桩顶水平位移,桩体侧向位移及基坑周边土体沉降量进行分析,得出基坑围护结构各项位移和周边土体沉降随时间及开挖深度的变化规律.建立研究区二维有限元模型,并将实测数据与模拟值进行对比,研究支护结构内力变化及桩后土体应力状态.研究结果表明:基坑长边桩顶水平位移约为短边桩顶水平位移的3倍,桩体最大侧向变形量位于1/2H(H为基坑开挖深度)处;基坑开挖及降水引起地面沉降范围约3H,基坑周边各监测断面最大沉降量出现在距基坑边22m处(约0.82H~0.96H),内支撑架设有助于增大基坑整体稳定性.     

车站深基坑变形规律与稳定性分析

针对车站深基坑施工中的变形与稳定性问题,以地表沉降变形≤22 mm 、土体侧向位移≤20 mm及等效安全系数SSR等为评价指标,研究不同深基坑开挖进程中地表沉降变形、底部土体隆起变形、深基坑内支撑稳定性和连续墙及墙后土体变形的演化规律,结果表明：地表土体受基坑开挖引起的变形规律呈“抛物线型”,最大沉降量0.5 mm;基坑底部最大隆起量23 cm,主要发生在粉质黏土层,在风化花岗岩层终止;支护结构以受压为主,局部受拉,整体稳定性良好;连续墙长轴方向中间墙体受后方土体挤压向基坑内产生1.25 cm变形,连续墙后2 m处土体最大变形量为1 mm,整体稳定;通过实测地表沉降量并与模拟结果进行对比,表明数值模拟结果可较好的获取基坑开挖过程中的变形规律,研究结果可为施工顺利进行提供有益指导。     

超大深基坑支护结构综合选型及变形规律研究

针对超大深基坑支护方案选择问题,以洛阳龙门站综合交通枢纽北广场工程为依托,建立超大深基坑支护方案指标评价体系,采用层次分析法和熵权法计算指标组合权重,利用模糊综合评价法选出合理的支护形式.运用Midas-GTS NX建立有限元模型,结合数值模拟和现场监测,分析在该支护形式下,基坑施工过程中土体和支护结构的变形规律.研究结果表明：通过计算确定基坑北侧、东侧和西侧采用放坡+土钉墙支护、南侧采用灌注桩+预应力锚索支护的方案.周边地表沉降分布规律符合沉降槽曲线,基坑西侧最大沉降发生在距坑边9 m位置,最大沉降量为18.32 mm,基坑南侧最大沉降发生在距坑边7 m位置,最大沉降量为15.82 mm,影响范围较基坑西侧减少9 m.基坑边坡水平位移和竖向位移最大值均发生在坡脚处.灌注桩水平位移随桩深呈先增大后减小趋势,桩身最大水平位移为15 mm,发生在桩长约10 m处.桩体产生向上位移,隆起量最终稳定在13.42 mm.现场监测结果均未超过控制值,基坑支护方案选取合理.     

深基坑土钉支护整体三维有限元分析

运用非线性有限元软件ADINA,建立了一个深基坑土钉支护结构整体三维有限元模型.研究了土钉的轴力、开挖面水平位移、坑后地面沉降、坑底隆起.结果表明:在纯土钉支护结构中,中部土钉受力最大,最大开挖面水平位移出现在开挖面顶部,坑后地表沉降曲线呈"勺子"形状,最大沉降值处距基坑边的距离约为1倍的开挖深度.     

长江漫滩地区深基坑地下连续墙受力变形特性研究

针对长江漫滩地区特殊条件,通过收集南京青奥轴线——梅子洲过江通道两种不同地下连续墙作为围护结构的深基坑工程实测数据,从统计学角度对比分析了格栅地下连续墙和普通地下连续墙受力变形特性,研究了地下连续墙顶水平位移、墙体深层侧向位移、地表沉降、支撑轴力等随基坑开挖及时间的变化规律。主要结论如下:1墙顶水平位移在支撑设置后均有回弹变形趋势,变形受支撑架设、预加轴力及拆除影响较大;2两种墙体侧向位移随深度均呈"胀肚型"变化趋势,两者最大侧移均发生在埋深中部区域;3格栅地下连续墙在基坑开挖初期,受支撑设置影响,地表先小幅隆起,普通地下连续墙无隆起现象,且沉降明显偏大,两者随距墙体距离增大沉降逐步变小,且不同距离处差异沉降在基坑开挖后期均有增大趋势。     

圆排式异型深基坑稳定性数值模拟分析

为定量分析圆排式异型深基坑支护的侧向变形特性与抗隆起稳定性,利用数值仿真软件Midas GTS NX对矩形深基坑及圆排式异型深基坑进行对比研究。研究结果表明:矩形深基坑受侧向挤压成"类工字型",最大侧向位移超过6 m,在实际工程中,基坑已经破坏坍塌,安全性差。对于圆排式异型深基坑,沿深度方向,粉质黏土层是易发生破坏的薄弱土层,同时开挖时隆起值最大,为17. 2 cm;在地连墙边界两侧,墙身侧向位移取得最大值2. 96 cm,充分证明圆排式异型深基坑相比于矩形深基坑具有足够的安全性与稳定性。     

天津市某医院深基坑工程变形特性及预测研究

依托天津地区软土大背景下的深基坑工程,对天津市某医院大尺度深基坑开挖施工过程中的现场观测数据进行理论分析,并利用FLAC~(3D)软件建立3D基坑模型并对基坑开挖支护全过程进行动态模拟,将软件计算结果与基坑现场监测数据进行对比。对比结果表明:模拟所得数值与现场观测数据规律较为贴切,随着基坑开挖进一步进行,外侧土体位移量逐步增加,当基坑开挖全部完成时,土体出现最大沉降量,桩顶水平位移与深层水平位移均满足监控测量标准的要求,说明所选取的支护结构等措施可以较好地控制基坑围护结构的变形并提出预测最大侧向位移的公式为后续类似工程提供一定的参考依据。     

一种新型基坑支护结构的力学性能分析

水泥土预应力支护桩墙工法(HCMW工法)是在SMW工法的基础上发展起来的基坑支护新方法,该方法具有抗弯能力好、止水性强、对周围土体扰动小等优点。结合工程实际,从工况力学分析、地表沉降量、抗倾覆稳定性验算、整体稳定性验算、抗隆起稳定性验算等角度对HCMW工法的支护规律和效果进行研究,结果表明:支护结构的水平位移在加撑前后有较明显的变化,从地表到坑底呈现逐渐减小的趋势,由于开挖时土体卸载,导致侧支护土体的压力减小,在开挖范围内向基坑移动导致基坑下部土体位移减小,一般出现在距坑底0～2m的范围;基坑周围整体沉降量和距坑边距离呈抛物线状,基坑的最大沉降量为18mm,发生在距离坑边5.6m的位置;最后,对基坑抗倾覆稳定性、整体稳定性和抗隆起稳定性进行验算,得到其稳定安全系数分别为1.974、1.386和2.793,均大于规范规定的安全系数,满足安全要求,表明HCMW工法具有较好的支护效果。     

城市地铁车站基坑变形监测分析

深基坑工程的施工监测可以对深基坑的开挖施工提供控制依据。结合上海地铁临港新城站基坑监测实例,分析了该基坑工程的工程概况及监测内容,并对基坑坑外地表沉降、围护墙顶部变形、围护墙体侧向变形、支撑轴力、坑外潜水水位、承压水水位、立柱桩垂直位移的监测数据进行了分析,为基坑的变形预测提供了基础数据条件。研究成果可为类似的基坑工程提供参考和借鉴。     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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

正~~