Effects of wind barrier on a vehicle passing in the wake of a bridge tower in cross wind and its response

Vehicles passing behind a bridge tower in strong cross winds are affected by sudden change of wind forces acting on them, which may cause accidents due to miss-steering of the drivers. As a countermeasure, wind barrier has sometimes been applied. However, the efficiencies of wind barrier are not known quantitatively, because the characteristics of the aerodynamic forces acting on a vehicle and the response of the vehicle due to those forces are not clear.In this paper, aerodynamic forces acting on a vehicle passing in the wake of a bridge tower with wind barrier are measured and their characteristics are presented first. Then, using the prediction procedures proposed in a previous study by the authors (J. Wind Eng. Ind. Aerodyn., submitted for publication), a vehicle response simulation was conducted and the effects of the wind barrier on the vehicle response were examined.In the experiment, the change of wind speed is confirmed to become moderate and the magnitude of the aerodynamic forces variation is found to reduce with the installation of wind barrier.Based on simulation results without wind barrier, the vehicle response becomes larger due to increased wind and vehicle speed, and reaches maximum when the wind direction is skewed 30° from the axis normal to the bridge axis and against the vehicle heading direction. The effects of the wind barrier were studied with a fixed steering simulation, and the responses such as side acceleration and yaw angular acceleration are found to be reduced effectively.     

Unified construction of running track tunnel and crossover tunnel for subway by rectangular shape double track cross-section shield machine

Construction has commenced on the world's first shield driven double track subway tunnel of rectangular shape for the Kyoto Municipal Subway. Full-scale loading tests were performed on lining segments to confirm the adequacy of their design. Also, as a method to excavate a rectangular cross-section, a ‘wagging cutter shield,’ which is equipped with rotating cutters that perform oscillating movement, was adopted. This paper presents a report on the overall planning, the tests that were performed in the process of planning, and the results of initial driving.     

新加坡路陆交通管理局T206项目运用系统模板的经验（英文）

通过分享临时工程设计和施工,讨论并强调承包商如何在其施工过程和挡土墙支护系统(ERSS)中进行模板支护设计;将新加坡建筑行业目前采用不同分包模式作对比,阐述良好模板支护系统设计具有减少人力、时间,节约成本并改善安全性。选择和购买系统模板运用于建设施工看似简单,但在地下车站和隧道施工中,挡土墙支护系统中有支撑体系,使系统模板的采用变得困难。     

Three-dimensional orthotropic equivalent modelling method of large-scale circular jointed lining

Due to the large spatial scale differences between the structure details and the global tunnel, the large-scale shield tunnels were usually modeled as continuous ‘pipes’ in the 3-D numerical analyses. The details (e.g. joints) that greatly affect the integral stiffness of the continuous 3-D tunnel models have seldom been discussed in literatures. This paper presents an idea of orthotropic equivalence for the modeling of the large-scale circular shield tunnel and the optimization procedure for the identification of the nominal material constants. Considering the tunnel’s structural characteristic in its radial, circumferential and axial directions and its periodicity, the segmentally erected lining is equivalently modeled as an orthotropic continuous structure. An optimization procedure based on the idea of inverse analysis and FE method which can quickly identify the equivalent constants is also proposed. Validation example shows that a reasonable consistency between results predicted by the equivalent/segmental models and the analytical formulas is achieved.     

Modeling of the thrust and torque acting on shield machines during tunneling

The paper analyzes the total load in the shield tunneling process. The cutterhead load is the most complicated component which provides a real-time response to geological conditions and operating states. This study calculates the normal and tangential loads on cutterhead by decoupling the cutterhead-soil system on excavation face. Then a comprehensive consideration is made of the influences of the overburden, the soil cutting, the chamber support, and the friction between the shield and the soil on loads. This study establishes a predicting model for the total load that fully reflects the influences of geological, operating, and structural parameters. The model is applied into two cases. Its effectiveness is verified by comparing the load calculated by the model, measured during tunneling and predicted by the Krause empirical model. The paper provides a reference for load designs and parameter controls during construction.     

软土基坑引起下卧隧道隆起的非线性流变

软土地区深基坑开挖改变了周边土体的初始应力,引起周边土体的位移,对周边构筑物造成不均匀沉降、混凝土开裂等不利的影响,并且可能危及临近地铁隧道的安全.对基坑开挖引起的下卧隧道的隆起变形进行了研究并提出了实用的预测方法.基坑开挖土体卸载引起的土体变形采用了Boussinesq应力解进行求解,隧道反力引起的土体变形采用了弹性半空间Mindlin应力解进行分析.隧道本身变形采用了弹性的地下连续梁进行分析,并且考虑隧道与土体的相互作用.通过引入软土的非线性流变模型,考虑了软土变形的时间效应,因此可以对复杂开挖过程进行模拟分析.还对基坑开挖对隧道隆起的效应进行了讨论,通过上海市某重点工程实例的隧道隆起量的预测结果与实测值对比分析,隧道隆起的监测结果证实了该方法的有效性.     

沉井基础下沉阻力分布特征研究

以海口某大桥主墩的沉井基础为研究对象,对沉井的下沉全过程进行了实时监测,根据大量现场实测资料,系统分析了沉井基础的下沉机理和下沉过程中的受力特性,得出了沉井下沉不同深度,经过不同土层时井壁侧摩阻力和刃脚端阻力的大小及分布规律,提出了下沉系数K和侧壁摩阻力值σf的计算方法和经验公式,以及土压力系数ki的取值范围。在此基础上建立了下沉阻力的计算模型,给出了最大侧壁摩阻力f0的计算公式和分布特征,所得出的结论可供同类工程借鉴与参考。     

Double-O-tube shield tunneling technology in the Shanghai Rail Transit Project

Double-O-tube (DOT) shield tunneling technology characteristics and research are described. Taking the construction of the DOT shield tunnel in the Shanghai Rail Transit Project as a case study, the sophisticated techniques and knowledge applied to soft soil DOT shield tunneling are summarized, creating a firm foundation for the broad application of DOT shield tunneling technology in the future.     

基坑开挖引起紧贴运营地铁车站的变形控制研究

监测数据表明:紧贴运营地铁车站单侧基坑开挖卸载引起车站结构不对称变形。以紧贴上海某地铁车站的基坑工程为背景,运用FLAC3D软件,建立三维数值分析模型模拟基坑开挖过程,计算结果与监测数据基本吻合。详细讨论了影响车站变形的几项主要施工措施,指出在车站开挖侧设置托换桩、旋喷桩及搅拌桩加固和分块开挖是控制车站变形的有效措施。研究表明,车站地下连续墙的水平位移随加固深度的增加而减小,但由于墙体与加固体之间的接触摩擦力,使墙体竖向位移随加固深度的增加而增大。