城市浅埋隧道的抗震及减震措施研究

随着城市浅埋隧道建设的快速发展,地下工程的抗震性能愈来愈受到关注,隧道结构的抗震、减震分析变得日益重要。文章综合论述了城市浅埋隧道的震害特点及减震措施,并阐述了浅埋隧道地震反应分析的实用方法,进而提出目前抗震设计中应该注意的问题,对改善城市浅埋隧道的抗震设计具有重要意义。     

铅芯橡胶支座在厦漳跨海大桥北汊北引桥抗震中的应用

以厦漳跨海大桥北汉北引桥为例,结合新颁布的《公路桥梁抗震设计细则》中特殊桥梁抗震验算理论,采用非线性时程计算方法对该桥的常规强度抗震方案及采用铅芯橡胶支座减震方案进行了对比计算,并对桥墩及桩基的地震反应采用特殊桥梁的性能目标进行了分析验算,计算结果表明,当遭受强地震作用时,采用铅芯橡胶支座的桥梁结构整体还在弹性范围,抗...     

盾构隧道管片接头弯曲刚度计算及影响因素分析

盾构隧道管片接头弯曲刚度是隧道设计关键参数之一。管片接头弯曲刚度的研究引起了广泛的兴趣,但主要集中在无传力衬垫的管片接头上。文章针对南京地铁盾构隧道粘贴了传力衬垫的管片接头刚度开展了研究,结果表明,粘贴了传力衬垫的管片接头弯曲刚度随着接头荷载的增加表现出了明显的非线性。最后对传力衬垫的厚度、螺栓预紧力和螺栓数量等弯曲刚度影响因素进行了分析,其计算结果对隧道设计具有明显的参考价值。     

地下结构专业抗震计算软件的开发与应用

在采用反应位移法和反应加速度法进行地下结构抗震设计时,考虑到在地震动参数确定、土层地震动反应、边界条件设置等方面存在的复杂性,采用VC＋＋开发面向道路隧道、地铁区间隧道、沉管隧道、地铁车站等地下结构的专业抗震计算软件SAUS。该软件由软件界面平台、建模前处理、抗震计算分析、结果后处理四部分构成。前处理功能可自动快速地完成建模、设定单元属性、施加荷载和设置边界条件等;抗震计算提供常用的多种圆形和矩形结构的反应位移法和反应加速度法的自动计算;后处理功能提供结构的位移和内力云图显示、结果数据查询以及自动生成计算书等。通过实际工程的应用,极大提高了地下结构在抗震设计方面的工作效率。     

邻近建筑物盾构隧道开挖引起的地表沉降预测研究

城市地铁区间施工主要以盾构法为主,但盾构法施工会使周围一定范围内的既有建筑物受到影响。目前对邻近建筑物地铁隧道施工引起的地表沉降分布规律研究偏少,且Peck经验公式在预测沉降时忽略了建筑物的存在及其刚度的不同对沉降分布曲线的影响。文章通过分析盾构隧道开挖邻近建筑物时引起的土体变形规律,得出如下结论:当地表沉降分别呈"塞形分布曲线"、"偏态分布曲线"和"正态分布曲线"的变化时,隧道分别在位于建筑物正下方、扰动范围内以及扰动范围外的三种工况下进行施工,同时给出了"塞形分布曲线"和"偏态分布曲线"的计算公式及相关参数。通过分析算例验证盾构隧道开挖位于建筑物不同位置处引起的地表沉降呈"塞形曲线"、"偏态曲线"和"正态曲线"分布的合理性,可为邻近建筑物隧道施工及设计提供理论指导。     

地震波斜入射下山岭隧道横向动力响应数值分析

近断层地震具有显著的方向性特征,地震波斜入射引起的非一致激励对隧道结构具有不可忽视的影响。文章基于粘弹性边界的波动数值理论,采用ANSYS进行汶川卧龙波输入下某山岭隧道横向地震响应数值分析,研究了地震波入射角度对衬砌动力响应的影响。计算结果表明:地震波斜入射时,衬砌结构的地震响应与垂直入射时有明显差异,呈现竖向受力特征,结构反应随着入射角度的增加而增大;斜入射时,隧道抗震的薄弱部位在拱顶、拱腰和拱脚处。研究结果可为山岭隧道抗震设计提供参考。     

基于耦合模型的土与浅埋隧道非线性动力分析

文章在考虑了土体和结构的动相互作用基础上,采用耦合模型对浅埋隧道进行抗震分析.该模型中不同的单元可以模拟结构不同的部位有限元可以模拟土体非线性本构关系、土体的分成性;接触面单元可以模拟土体和钢筋混凝土之间的滑移、拉裂、嵌入等现象;无限元可以模拟无限远处土体位移为零的特征.文中首先阐述了接触元的原理以及单元刚度矩阵的积分形式;然后推导了平行无限元的单元刚度矩阵.通过对某双洞矩形截面隧道的地震反应分析,为同类型工程的抗震设计提供指导性意见.     

瑞利波作用下隧道洞口段的抗震设防长度

隧道洞口段是隧道抗震设计的薄弱部位,文章从瑞利波动方程出发,推导了洞口段地层在瑞利波作用下的峰值位移、峰值加速度和地层曲率的计算公式,并探讨了洞口段抗震设防长度。分析结果表明:在瑞利波作用下,地层位移、曲率和加速度随隧道埋深的增大而迅速减小,因此当洞口埋深达到一定程度后,地层对隧道的强加位移已很小,无需再设防;现行隧道设计规范规定的洞口段抗震设防长度偏短,应延长。最后,结合汶川地震隧道洞口段破坏长度,进行了分析验证,分析结论可供隧道抗震设计、灾后重建和今后有关规范修订参考。     

泥水盾构下穿已有隧道施工过程数值模拟研究

针对2010年上海世博会重大配套工程——打浦路隧道复线工程,进行了数值模拟研究。根据工程实际,土体采用Drucker-Prager弹塑性本构关系,建立了沿弯曲路径下穿几何特性复杂的已有隧道的三维非线性数值模型,通过施加开挖面泥水压力模拟了泥水盾构施工过程,采用Newton-Raphson方法进行非线性求解。比较了轴线地表沉降数值模拟计算结果与工程实测数据,表明模拟模型可靠、可信;分析了泥水盾构施工对周围土体及已有隧道的影响,得到了已有隧道的位移和应力的变化规律,可为实际工程提供参考。     

震区同震地表破裂统计经验关系及其对隧道抗震设计的意义

震区的同震地表破裂位移是隧道产生剪切破坏和塌方的主要因素。文章系统地总结了前人关于震区同震地表破裂特征参数的统计经验关系,并对汶川地震期间的隧道震害进行了对比分析。研究结果表明:与隧道抗震设计直接相关的参数是地表破裂长度、最大同震破裂位移、平均同震破裂位移,地表破裂长度主要反映震区所产生的剪切位移的影响范围;在实际隧道抗震设计中,可以考虑采用平均同震破裂位移来估算地震发生时对地下结构的损害程度,同时应参考隧道与主要的深大断裂和附属断层的相对位置关系;而地下破裂长度、下倾破裂宽度和破裂面积可以用于估算一次地震影响范围,进而预估隧道可能遭受的地震灾害损失;发震断层附近的附属断层在地震时也会产生同震位移,并对地下结构和隧道产生破坏。     

Characterization of traffic oscillation propagation under nonlinear car-following laws

Unlike linear car-following models, nonlinear models generally can generate more realistic traffic oscillation phenomenon, but nonlinearity makes analytical quantification of oscillation characteristics (e.g, periodicity and amplitude) significantly more difficult. This paper proposes a novel mathematical framework that accurately quantifies oscillation characteristics for a general class of nonlinear car-following laws. This framework builds on the describing function technique from nonlinear control theory and is comprised of three modules: expression of car-following models in terms of oscillation components, analyses of local and asymptotic stabilities, and quantification of oscillation propagation characteristics. Numerical experiments with a range of well-known nonlinear car-following laws show that the proposed approach is capable of accurately predicting oscillation characteristics under realistic physical constraints and complex driving behaviors. This framework not only helps further understand the root causes of the traffic oscillation phenomenon but also paves a solid foundation for the design and calibration of realistic nonlinear car-following models that can reproduce empirical oscillation characteristics.     

Calibration of nonlinear car-following laws for traffic oscillation prediction

Frequency-domain analysis has been successfully used to (i) predict the amplification of traffic oscillations along a platoon of vehicles with nonlinear car-following laws and (ii) measure traffic oscillation properties (e.g., periodicity, magnitude) from field data. This paper proposes a new method to calibrate nonlinear car-following laws based on real-world vehicle trajectories, such that oscillation prediction (based on the calibrated car-following laws) and measurement from the same data can be compared and validated. This calibration method, for the first time, takes into account not only the driver’s car-following behavior but also the vehicle trajectory’s time-domain (e.g., location, speed) and frequency-domain properties (e.g., peak oscillation amplitude). We use Newell’s car-following model (1961) as an example and calibrate its parameters based on a penalty-based maximum likelihood estimation procedure. A series of experiments using Next Generation Simulation (NGSIM) data are conducted to illustrate the applicability and performance of the proposed approach. Results show that the calibrated car-following models are able to simultaneously reproduce observed driver behavior, time-domain trajectories, and oscillation propagation along the platoon with reasonable accuracy.     

高墩大跨连续刚构桥非线性稳定计算分析

文章以赫章特大桥为工程背景,以压溃准则为失稳判定准则,利用有限元ANSYS结构分析软件,对采用均布力和集中力两种不同加载方式时的高墩大跨连续刚构桥进行非线性稳定计算。计算结果表明：（1）采用集中力加载方式的计算结果更符合实际情况;（2）失稳模态与风荷载的作用方向有关;（3）结构塑性区域与施加的荷载方式和所施加的风荷载有关。     

Prediction of ambient carbon monoxide concentration using nonlinear time series analysis technique

This study evaluates the potential of nonlinear time series analysis based methods in predicting the carbon monoxide concentration in an urban area. To establish the functional relationship between current and future observations, two models based on local approximations and neural network approximations are used. To compare the performance of the models, an autoregressive integrated moving average model is also applied. The multi-step forecasting capabilities of the models are evaluated.     

Stochastic capacity expansion models for airport facilities

It is important and also challenging to plan airport facilities to meet future traffic needs in a rapidly changing environment, which is characterized by various uncertainties. One key issue in airport facility development is that facility performance functions (delay levels as functions of capacity utilization rates) are nonlinear, which complicates the solution method design. Potential demand fluctuations in a deregulated aviation market add another dimension to the decision making process. To solve this problem, a deterministic total cost minimization model is proposed and then extended into stochastic programs, by including uncertainties in traffic forecasts. After the exploration of properties of the delay cost function, an Outer-Approximation (OA) technique which is superior to the existing discrete approximation is designed. After model enhancements, an efficient solution framework based on the OA technique is used to solve the model to its global optimality by interactively generating upper and lower bounds to the objective. Computational tests demonstrate the validity of developed models and efficiency of proposed algorithms. The total cost is reduced by 18.8% with the stochastic program in the numerical example.     

An online speed profile generation approach for efficient airport ground movement

The precise guidance and control of taxiing aircraft based on four-dimensional trajectories (4DTs) has been recognised as a promising means to ensure safe and efficient airport ground movement in the context of ever growing air traffic demand. In this paper, a systematic approach for online speed profile generation is proposed. The aim is to generate fuel-efficient speed profiles respecting the timing constraints imposed by routing and scheduling, which ensures conflict-free movement of aircraft in the planning stage. The problem is first formulated as a nonlinear optimisation model, which uses a more flexible edge-based speed profile definition. A decomposed solution approach (following the framework of matheuristic) is then proposed to generate feasible speed profiles in real time. The decomposed solution approach reduces the nonlinear optimisation model into three tractable constituent problems. The control point arrival time allocation problem is solved using linear programming. The control point speed allocation problem is solved using particle swarm optimisation. And the complete speed profile between control points is determined using enumeration. Finally, improved speed profiles are generated through further optimisation upon the feasible speed profiles. The effectiveness and advantages of the proposed approach are validated using datasets of real-world airports.     

基于非线性渗流模型的管道型岩溶隧道突水机理研究北大核心CSCD

管道型岩溶突水是一个复杂的多场耦合的非线性渗流问题,致灾具有突发性。为揭示管道型岩溶突水灾害的发生机理,文章基于多物理场耦合作用机理,开展了不同溶腔水压、岩溶管道内不同填充介质、不同岩溶管道宽度及岩溶管道长度条件下的多场耦合分析。得到以下结论:(1)管道型岩溶破坏模式下发生的突水灾害,根据填充介质透水性能的异同而表现不同;(2)流体从富水溶腔中流出时流速较小,流经岩溶管道后流速逐渐增加,进入隧道后达到最大值;(3)影响突水过程的因素主要有:富水溶腔水压、岩溶管道或断层裂隙带内填充介质的种类、岩溶管道的宽度、隧道与水源的距离,其中,岩溶管道宽度及岩溶管道内填充介质类型对突水影响大于其他因素。     

复杂条件下地铁车站施工关键技术

在复杂条件下为使地铁车站项目的施工质量、工期、造价和安全目标得以实现,关键施工技术的正确采用至关重要。文章以沈阳中街地铁站为例,针对工程施工所面临的复杂条件,对施工技术路线的确定和施工方案涉及的关键技术进行了分析和探讨。工程实践及良好的施工效果表明,项目施工中采取的注浆加固、大跨度扣拱、超前地质预报以及施工防水等关键技术,对近接建筑物、不稳定地层下开挖大跨度隧道施工中有效控制地表沉降、保护周边建筑物及管线安全起到了关键作用。