隧道近距下穿管线的爆破振动特征及安全标准

采用ANSYS/LS-DYNA软件中的ALE算法建立隧道-地层-管线三维数值模型,在地面测试爆破振动,验证数值模型可靠性;研究隧道爆破振动下地下管线横向和纵向的峰值振速和应力响应特征,探究管线和周边围岩的振动响应差异;分析净距、掏槽起爆药量和周边岩土性质对管线振动的影响。研究结果表明:数值模型中,地面测点的振速峰值与现场实测振速峰值相对误差均不超过5.0%;隧道爆破地震波引起管线横断面底部的峰值振速最大,中部次之,顶部最小,而管线中部的峰值拉应力最大,底部次之,顶部最小;沿管线纵向各点的振速峰值和拉应力峰值均出现在距离爆源0～4 m处,并随着与爆源距离的增大而逐渐减小;接触面处管线各单元的峰值振速和振动频率均明显比相应位置处土层单元的大;地下管线的峰值振速和拉应力均随着净距减小、掏槽装药量增大而不断增大,且管线上部的峰值振速和拉应力增量要比底部和中部的小;当地下管线周边为含卵石砂层时,管线的峰值振速和峰值拉应力最大,地下管线周边为回填黏土和夯实砂土时则较小。根据最大拉应力强度理论,建议管线的最大振速控制在4.68 cm/s以下。     

不同土质中隧道埋深对地表沉降的影响

分析地铁隧道开挖引起的地表沉降对建筑物安全具有重要意义.通过有限差分软件FLAC3D分别对粉质黏土、粉砂、黏土条件下的隧道开挖进行了数值模拟,分析三种不同土质中地表沉降随埋深的变化规律以及三种土质中同一埋深下地表沉降槽曲线的变化规律.结果表明:相同埋深下粉质黏土、粉砂、黏土中的地表沉降值依次减少;粉质黏土、粉砂、黏土的地表沉降槽曲线宽度随埋深的增加而增大;粉砂沉降槽相对于黏土较窄而深,说明土质条件越好,沉降槽宽度越小.     

暗挖隧道施工对既有地铁车站的影响与控制分析

针对暗挖隧道施工过程中对既有地铁车站的影响,笔者结合实际隧道暗挖工程模拟其施工全过程。结果显示:呈现狭长特性的隧道,其基坑周围地表的最大竖向位移出现在隧道南、北两侧且呈对称分布;基坑地表变形最严重的一层其沉降曲线呈现明显的"凹陷状";随着开挖深度的逐渐增加,隧道北侧地表竖向位移的增加值与其呈现非线性的变化趋势。结论:暗挖隧道施工对于既有地铁车站的影响很小。     

品字形隧道安全间距与开挖长度地表沉降分析

为研究三孔平行通风隧道的开挖对围岩和地表沉降的影响,依托贵阳地铁车站新型通风结构品字形隧道工程,结合理论推导和数值模拟,分析三孔隧道的最小安全距离和合理布置方式,以及由不同隧道开挖长度产生的围岩应力和地表竖向位移.结果表明:最大直径为9 m的品字形三孔隧道的最小间距为10 m;开挖长度5～20 m对地表沉降变化几乎无影响;随着三孔隧道依次开挖,呈现出地表沉降变化率增大的递进式影响.分析了开挖小净距三孔品字形隧道的实际可行性,将模拟数据与现场监测数据进行对比,验证了本模型数据分析的准确性.     

地面堆载引起下卧盾构隧道剪切错台变形计算研究

采用Boussinesq公式求解得到地面堆载工况下隧道轴线处的土体附加应力;基于剪切错台模型,运用最小势能原理计算得到下卧地铁盾构隧道的纵向位移以及相邻盾构衬砌环之间的错台量和环间剪切力。通过算例分析,研究堆载面荷载q、堆载偏移距离s、隧道上部覆土厚度h以及堆载尺寸B和L对隧道纵向位移的影响。研究结果表明:q越大,盾构隧道的沉降量就越大,但隧道沉降影响范围并没有增大;随着s增大,隧道沉降量越来越小且沉降量减小的速率加快,隧道的水平位移则先增大后减小;随着h增加,隧道最大沉降减小,同时隧道沉降影响范围加大;B的改变对隧道竖向位移影响非常小,L的改变对隧道沉降量及范围的影响较大;隧道的竖向位移要明显大于隧道的水平位移。     

黄土地铁隧道施工围岩及地表变形规律研究

以西安地铁3号线某暗挖站区间双线地铁隧道施工为背景,采用有限差分软件FLAC3 D建立土体三维力学模型对双线地铁隧道台阶法施工过程进行动态模拟;并结合现场实测数据分析台阶法施工引起的地铁隧道围岩及地表变形规律。结果表明:(1)台阶法施工诱发的横向地表沉降呈"V"形,最大地表沉降出现在隧道中线偏右方约3 m,最终形成的沉降槽宽度约为隧道洞径的2倍。(2)台阶法施工诱发的纵向地表沉降在开挖面前地表沉降量最大,随着开挖掌子面距离越远,沉降量越小,最后在开挖进尺40 m附近趋于稳定。(3)隧道拱顶纵向沉降曲线与地表沉降变化趋势基本一致。帮部围岩变形呈现出先快速增长后逐渐平稳的趋势,且影响范围逐渐增大。所得结论可为双线地铁隧道施工和变形预测提供参考。     

西安盾构法施工引起的地面沉降有限元分析

本文运用有限元基本原理，利用大型通用有限元软件ANSYS时西安地铁尤家庄到南康村站隧道区间段进行数值模拟，分析对开挖面施加不同平衡反力时沉降的变化情况，建议西安地铁施工时将其控制在100kPa～150kPa范围内。分析了不同开挖时间地面各点沉降和水平位移变化规律；埋深不同各点的沉降和位移的时间历程变化规律，横断面埋深不同沉降和水平位移的变化规律。     

双隧道开挖对地表沉降及地埋管线的影响研究

地铁建设中双隧道施工往往不是同步进行的,双隧道的布置间距及施工顺序的多样性将诱发复杂的地层响应,因此针对交叠双隧道施工对地层和管线的影响展开研究很有必要。以肩驮式双隧道开挖为研究对象,重点考虑开挖顺序和双隧道垂直间距不同时对地层和管线的影响机理。文章首先对比双隧道开挖对地埋管线的离心试验及数值分析的结果,验证了数值模拟的准确性和有效性。随后对双隧道开挖工况进行进一步数值拓展分析,着重研究了不同垂直间距及双隧道开挖顺序引起的地表沉降、管线竖向应变、土体剪应变和土体主应力的变化规律。研究结果表明,对于肩驮式双隧道,先上后下开挖时会产生较大的管线变形和地表沉降;随着双隧道垂直间距的增大,地表沉降和管线变形减小,但管线和周围土层受开挖影响的范围增大;当双隧道之间的垂直间距大于3.0D_T时,双隧道之间的相互扰动效应基本消失。     

盾构隧道施工参数对地表沉降的影响研究

以广州市地铁十八号线万顷沙站—万横中间风井盾构区间隧道工程为研究背景，运用有限元软件，探讨了隧道埋深比、掘进压力、注浆厚度3种因素引起的地表变形的影响。在分析中使用控制变量法，在其他条件不变的情况下，改变掘进压力等施工参数并选取合理的值域后进行数值模拟，研究各种参数对地表沉降的影响程度。结果表明：(1)随着隧道埋深比的增大，横向地表沉降量峰值出现先增加后下降的变化规律，沉降槽曲线也逐步趋于缓和；(2)地面横向沉降峰值随掘进压力的增大而增大，当掘进压力超过掌子面土体应力释放值时，沉降量峰值与掘进压力成正比；(3)地面横向沉降量与注浆层厚度成反比。     

西安地铁盾构下穿高铁路基沉降及变形分析

为研究盾构下穿高铁路基时道床、路基响应规律,依托西安地铁一号线下穿郑西高铁实际工程,基于沉降理论估算了双线隧道施工引起上方路基沉降量,建立了区间隧道下穿既有高铁路基数值模型,分析了不同桩底与隧道净距下道床、路基、CFG桩竖向沉降与CFG桩受力响应规律。结果表明：CFG桩轴力、道床、路基竖向沉降变形随桩底与隧道净距逐渐增大而增大,施工至隧道正上方时达到最大,平行于掘进方向随与隧道水平距离增加,沉降逐渐减小,沿盾构施工方向沉降逐渐增大,道床与路基结构产生倾斜但垂直倾斜高度均不超过2mm；CFG群桩基础最大轴力集中两侧单桩,而隧道正上方范围内CFG所受轴力较小,在h=3.235m与5m工况下,CFG桩所受轴力值达到最小、最大,褥垫层以内的CFG桩未出现受压破坏。     

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Editorial note for the special topic on ＂Nanopore Analysis＂

The concept of nanopore analysis, using the pore-forming protein a-hemolysin to detect individual nucleic acids at a single-molecule level, was first proposed in 1996. Over the past two decades, tremendous progress has been made in the nanopore field, and nanopore analysis has become a label-free and high-throughput method for probing bio- molecules and other analytes with single-molecule sensi- tivity, especially holds the promising for ＂third generation＂ DNA sequencing. However, challenges still remain in the experimental strategies and the design of whole nanopore-based instruments. Here, we proudly present a special topic dedicated to the topic of ＂Nanopore Analysis＂, with 8 reviews/articles providing up to date coverage of the experimental strategies, theoretical calcu- lations and simulations, and instrument design. Reviews and articles on the experimental strategies cover control of DNA partitioning into a nanopore, detection of target DNA, and the advantages of nanopore-based DNA sequencing. The theoretical calculations and simulations discuss the translocation behavior of DNA, and an inte- grated measurement system and data analysis software are presented for instrument design.     

Effects of climate change on biodiversity

1 Rise of studies on climate change＇s effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America＇s annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].     

Discussing the Expansive Learning in Modern Organizations

<正>1 Introduction Endeavours on learning methods have long occupied the mind spaces of scholars and there have been theories abound on how people learn and in what way organisations can use some of the knowledge gained in the art of learning to maximise human productivity.While the theories by themselves are not solutions to problems,they are steps of inquiry that provide us with interesting perspectives that we can use to extend our knowledge of the dimensions of learning.This paper is an exploratory work on the theories postulated by three notable scholars including Zimmerman     

Progress in Linear Scaling Non-Orthogonal Localized Molecular Orbitals Method

The non-orthogonal localized molecular orbital(NOLMO)is the most localized representation of electronic degrees of freedom.As such,NOLMOs are thus potentially the most efficient for linear scaling calculations of electronic structures for large systems.However,direct ab initio calculations with NOLMO have not been fully implemented and widely used,partly because of the slow convergence issue in the optimization of NOLMO.We devel-     

An Accurate and Universal HEOM Approach to Strongly Correlated Quantum Impurity Systems

A hierarchical equations of motion(HEOM)approach is developed for general open quantum systems coupled to fermionic environment.The HEOM method is in principle formally exact,as it resolves nonperturbatively the combined effects of many-body interaction,system-bath dissipation,and non-Markovian memory.In practice,the HEOM approach is highly accurate and efficient for the characterization of strongly correlated quantum impurity sys-     

关于有理混合吸引子的Ciric型非唯一不动点定理

本文我们应用有理混合吸引子条件去证明具非唯一不动点的映射Ciric型的若干不动点定理.结果推广并改进已知的一些结果.     

次线性算子交换子在变指数Herz-Morrey空间上的有界性

本文主要利用给出的次线性算子分别与BMO函数及Lipschitz函数生成的交换子在变指数L~(p(·))(R~n)空间上的有界性,证明了其在变指数Herz-Morrey空间MK_(q,p(·))~α~((·)),λ(R~n)上的有界性.     

利用GPS双频观测值实现PPP电离层延迟高阶项改正

给出了利用双频观测值计算L3组合电离层延迟高阶项改正的方法,并与全球电离层延迟文件的改正效果进行对比.利用赤道附近的15个国际全球卫星导航定位系统服务组织(IGS)站的数据进行比较,结果表明:2种方法计算的电离层二阶项延迟互差最大不超过1 cm,三阶项延迟互差最大不超过5 mm;电离层高阶项改正后的观测值精密单点定位(PPP)解算结果N、E、U方向互差平均值分别为0.4、0.5、1.0mm,因此2种改正方法效果在同一水平.