神经网络方法在基坑变形预测中的应用研究

基坑开挖过程中引起的变形是一个复杂问题。以改进的BP人工神经网络为基础，建立基坑开挖过程中支护桩水平位移与侧向位移的预测模型，实现对基坑变形的非线性预测。预测结果表明预测值与实测值相当吻合，说明了预测模型在预测基坑变形中的有效性。     

小议基坑变形及其控制

深基坑在开挖过程中不但对基坑本身存在着安全隐患，而且对基坑周围的建筑物和环境也将造成威胁，本文主要从几种常见的基坑变形现象着手，进而就这些常见变形现象的机理进行了分析，最后根据笔者多年工作经验给给出了预防基坑变形的措施，相信本文的分析将在同行们加深基坑变形的认识方面有所裨益。     

基坑支护安全的保障探讨

城市用地资源越来越稀缺，大量深大基坑不断涌现。减小基坑侧向变形，需要采取有效措施来保证基坑稳定。城市基坑工程的特殊性，很多情况下尚需在人工支护条件下进行基坑开挖。基坑工程应解决的重要问题是根据基坑工程的特点进行设计，并选择合适的支护结构。     

深挖填土基坑监测及安全性分析

为研究填土基坑破坏机理,分析沉降监测及水平位移监测中基坑变形与基坑设计、施工速度、施工质量、周围建筑及水文地质情况的相互关系,采用变形观测仪器,测试了一典型基坑不同位置监测点处的变形速率、变形量及绝对变形量等量值,理论上验算了土性参数并分析了基坑在各工况下的安全系数。结果表明基坑顶部变形在开挖过程中存有方向相反的反复过程,形成不同的局部破坏形态;是否合理选取填土层物理力学参数、超载、施工中水环境的变化及基坑支护的设计都影响着基坑边坡的安全。本基坑工程引发的问题对同类型基坑有普遍性。     

软土区管廊基坑柔性支护下基坑变形控制标准

软土区基坑工程中,控制基坑变形十分重要。本文对广州南沙柔性支护的管廊基坑进行有限元分析,得到了开挖过程中基坑的变形特征,开挖到基坑底部时,围护结构桩身变形由“悬臂式”变为“内凸型”,围护结构达到最大水平位移值31.92mm;地表沉降与坑底隆起最大值为22.26mm、54.81mm;稳定性计算结果为2.2,基坑变形及稳定性均满足规范要求。继而研究了6个不同基坑断面在临界失稳状态与稳定性满足规范这两种条件下,围护结构水平变形、地表沉降、坑底隆起的变形最大值占基坑开挖深度的百分比,建议将计算结果的平均值作为控制值的参考值。基坑临界失稳状态下,设计安全等级为二级、三级的基坑围护结构水平变形控制参考值分别为基坑深度的2.62%、3.24%。基坑稳定性满足规范要求时,设计安全等级为二级、三级的基坑围护结构水平变形控制参考值分别为基坑深度的0.8%、0.93%。     

填土深基坑施工监测及失稳分析

结合南宁某填土基坑实际破坏情况,分析了在沉降监测及水平位移监测中基坑变形与基坑设计、施工速度、施工质量、周围建筑及水文地质情况的联系。通过分析基坑不同位置监测点处的变形速率、变形量及绝对变形量,发现基坑顶部变形在开挖过程中存有反复过程,且对基坑的局部破坏有重大影响。通过验算土性参数,从理论上分析基坑在各工况下的安全系数,说明填土层物理参数的准确选取和超载的存在对基坑土钉支护的成功设计有重要影响。     

软土基坑分步开挖卸荷时效及其对邻侧隧道影响

为研究软土地层中基坑开挖卸荷时效及其对邻侧隧道影响,设计并实施了相似比为1:20的物理模型试验,得到了基坑围护结构变形、地表沉降、坑底隆起、隧道竖向变形、隧道水平变形以及隧道断面收敛变形等数据。研究结果表明：基坑开挖引起的围护结构最大侧向变形为0.61%H(H为基坑深度),大于上海软土地区地铁车站基坑围护结构最大值的上限0.50%H;分步开挖过程中的墙体侧向变形和地表沉降具有明显的时间效应,卸荷时效对基坑变形的影响随开挖深度增加而增强;基坑开挖引起隧道变形以朝向坑内的水平变形为主,同时伴随少量朝上的竖向变形;隧道侧向变形与相同深度处围护结构侧向变形大致呈线性关系,据此可预估后续开挖引起的隧道侧向变形;基坑开挖引起邻近隧道产生径向收敛变形,隧道断面呈“横向伸长、竖向压缩”的特点,横向收敛约为竖向收敛变形的1.7倍;当隧道与基坑开挖面的竖向净距在0.2H～0.5H时,基坑开挖卸荷引起的隧道变形响应十分敏感,隧道竖向变形随坑底隆起增加而显著增加。     

基坑工程的发展现状与展望

从土层性质、基坑开挖变形与稳定性机理、挡土结构内力和变形的计算理论以及参数的反馈分析确定这四个方面分析了基坑工程的发展现状，并讨论了今后的发展趋势－ 文中对软土基坑工程的发展现状与展望进行了较为深入的分析和讨论，其结论对基坑的设计与施工具有指导意义－ 表１，参２０－     

基坑变形环境效应及其控制对策

首先对基坑工程环境效应及变形控制进行了详细的论述.简介了自制的基坑工程变形控制优化设计及其有限元数值模拟系统(SDCDEFEM),利用该系统,对影响基坑变形的各因素进行了有限元数值模拟分析,得出了简明估算基坑最大变形及其位置的统计关系式.在此基础上提出了控制基坑环境变形的经济有效的对策.     

软土地区分隔型基坑群变形特性实测分析

以上海国际航空中心基坑群工程为例,通过现场实测数据统计分析结合数值分析方法,分析了分隔型基坑群变形特性.深入研究了分隔型基坑群施工过程中隔墙变形、围护结构侧向变形和坑后土体沉降的发展规律,分析对比了不同区域围护结构变形和坑外地表沉降的差异.对比基坑群工程和传统基坑工程.结果表明,基坑群施工中隔墙变形先增大后减小,受后续开挖影响显著;基坑群分隔带处围护结构最大变形平均为0.16%H(H为基坑开挖深度),远小于上海地区平均值0.60%H;分隔带处坑外地表沉降仅有0.14%H,小于上海地区平均值0.40%H.研究可以揭示基坑群变形叠加机制,评估基坑群施工对环境的影响,对后续基坑群施工和敏感建构筑物保护有一定的借鉴意义.     

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     

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