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Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault or a normal fault: A parametric study

Masoud RANJBARNIA, Milad ZAHERI, Daniel DIAS

《结构与土木工程前沿（英文）》 2020年第14卷第4期页码 998-1011 doi: 10.1007/s11709-020-0621-8

摘要： Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting.

关键词： urban tunnel sprayed concrete reverse fault normal fault finite difference analysis

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Climate change and China’s mega urban regions

Chaolin GU, Sunsheng HAN

《结构与土木工程前沿（英文）》 2010年第4卷第4期页码 418-430 doi: 10.1007/s11709-010-0075-5

摘要： China’s mega urban regions are focal points of economic development and environmental concerns. This paper positions four mega urban regions (i.e., the Yangtze River Delta, the Pearl River Delta, the Bohai Bay Area, and the South-eastern Fujian Province) along China’s coast into the national economy and elaborates their development challenges and planning innovations. Mega urban regions in China are spatial consequences of rapid economic transition. They deserve close scrutiny and demands for innovative planning responses in order to maintain their key role in driving economic growth but limiting their greenhouse gas emission.

关键词： climate change mega urban region urban planning

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土质隧道深浅埋界定方法研究

赵占厂,谢永利

《中国工程科学》 2005年第7卷第10期页码 84-86

摘要：

针对现有隧道深浅埋界定方法存在的问题，结合现场测试和数值仿真结果，明确了应从围岩压力性质角度进行深浅埋界定。首次提出了以数值仿真技术为手段，利用拱上中心线土体侧压力系数变化规律为依据进行深浅埋界定的思路，并用2个工程实例进行了验证，新方法对土质隧道衬砌设计和施工有重大意义。

关键词：土质隧道深埋和浅埋界定方法

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Effect of cutterhead configuration on tunnel face stability during shield machine maintenance outages

《结构与土木工程前沿（英文）》 2023年第17卷第4期页码 522-532 doi: 10.1007/s11709-023-0930-9

摘要： Owing to long-distance advancement or obstacles, shield tunneling machines are typically shut down for maintenance. Engineering safety during maintenance outages is determined by the stability of the tunnel face. Pressure maintenance openings are typically used under complicated hydrogeological conditions. The tunnel face is supported by a medium at the bottom of the excavation chamber and compressed air at the top. Owing to the high risk of face failure, the necessity of support pressure when cutterhead support is implemented and a method for determining the value of compressed air pressure using different support ratios must to be determined. In this study, a non-fully chamber supported rotational failure model considering cutterhead support is developed based on the upper-bound theorem of limit analysis. Numerical simulation is conducted to verify the accuracy of the proposed model. The results indicate that appropriately increasing the specific gravity of the supporting medium can reduce the risk of collapse. The required compressed air pressure increases significantly as the support ratio decreases. Disregarding the supporting effect of the cutterhead will result in a tunnel face with underestimated stability. To satisfy the requirement of chamber openings at atmospheric pressure, the stratum reinforcement strength and range at the shield end are provided based on different cutterhead aperture ratios.

关键词： tunnel face stability cutterhead configuration aperture ratio pressure gradient support ratio

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Treatability aspects of urban stormwater stressors

Anthony N. TAFURI, Richard FIELD

《环境科学与工程前沿（英文）》 2012年第6卷第5期页码 631-637 doi: 10.1007/s11783-012-0420-0

摘要： Pollution from diffuse sources (pollution from contaminants picked up and carried into surface waters by stormwater runoff) has been identified as a significant source of water quality problems in the U.S. scientists and engineers continue to seek solutions that will allow them to optimize existing technologies and develop new ones that will provide the best possible protection to people, wildlife, and the environment. This paper addresses the various pollutants or stressors in urban stormwater, including flow (shear force), pathogens, suspended solids/sediment, toxicants (organic and metals), nutrients, oxygen demanding substances, and coarse solids. A broad overview of the pollutants removed and the removal mechanisms by and of conventional best management practices (BMPs) is also presented. The principal treatment mechanisms of conventional wet ponds, vegetative swales/buffer strips, and wetlands are sedimentation and filtration. These mechanisms have the capability to remove significant amounts of suspended solids or particulate matter and are a vital component of strategies to reduce pollutant loads to receiving waters. In addition, because most of the nation’s receiving water violations are caused by pathogen indicator bacteria, it is of utmost importance that research efforts address this problem. Further research is also needed on the treatment of emerging contaminants in BMPs and on the costs and affects of maintenance and maintenance schedules on the long-term performance of BMPs.

关键词： stormwater wet weather flow urban runoff

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ECOLOGICAL EFFECTS OF NITROGEN DEPOSITION ON URBAN FORESTS: AN OVERVIEW

《农业科学与工程前沿（英文）》 2022年第9卷第3期页码 445-456 doi: 10.15302/J-FASE-2021429

摘要：

● Patterns and effects of N deposition on urban forests are reviewed.

关键词： biodiversity carbon sequestration nitrogen deposition nutrient imbalance soil acidification urban forest

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Bending failure performance of a shield tunnel segment based on full-scale test and numerical analysis

《结构与土木工程前沿（英文）》页码 1033-1046 doi: 10.1007/s11709-023-0973-y

摘要： This study focuses on the bending failure performance of a shield tunnel segment. A full-scale test was conducted to investigate deformation and failure characteristics. During the loading, the bending failure process can be divided into four stages: the elastic stage, working stage with cracks, failure stage, and ultimate stage. The characteristic loads between contiguous stages are the cracking, failure, and ultimate loads. A numerical model corresponding to the test was established using the elastoplastic damage constitutive model of concrete. After a comparative analysis of the simulation and test results, parametric studies were performed to discuss the influence of the reinforcement ratio and proportion of tensile longitudinal reinforcement on the bearing capacity. The results indicated that the change in the reinforcement ratio and the proportion of tensile longitudinal reinforcement had little effect on the cracking load but significantly influenced the failure and ultimate loads of the segment. It is suggested that in the reinforcement design of the subway segment, the reinforcement ratio and the proportion of tensile longitudinal reinforcement can be chosen in the range of 0.7%–1.2% and 49%–55%, respectively, allowing the segment to effectively use the reinforcement and exert the design strength, thereby improving the bearing capacity of the segment.

关键词： shield tunnel bearing capacity failure mechanism segment reinforcement

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Discontinuous mechanical behaviors of existing shield tunnel with stiffness reduction at longitudinal

《结构与土木工程前沿（英文）》 2023年第17卷第1期页码 37-52 doi: 10.1007/s11709-022-0920-3

摘要： An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. The opening and relative dislocation of the longitudinal joints can be calculated using Dirac delta functions. Compared with other approaches, our method yields results that are consistent with centrifugation test data. The effects of the stiffness reduction at the longitudinal joints (α and β), the shearing stiffness of the Timoshenko beam GA, and different additional pressure profiles on the responses of the shield tunnel are investigated. The results indicate that our proposed method is suitable for simulating the discontinuous mechanical behaviors of existing shield tunnels with longitudinal joints. The deformation and internal forces decrease as α, β, and GA increase. The bending moment and shear force are discontinuous despite slight discontinuities in the deflection, opening, and dislocation. The deflection curve is consistent with the additional pressure profile. Extensive opening, dislocation, and internal forces are induced at the location of mutation pressures. In addition, the joints allow rigid structures to behave flexibly in general, as well as allow flexible structures to exhibit locally rigid characteristics. Owing to the discontinuous characteristics, the internal forces and their abrupt changes at vulnerable sections must be monitored to ensure the structural safety of existing shield tunnels.

关键词： tunnel–soil interaction discontinuous analysis longitudinal joints existing shield tunnel Timoshenko beam Dirac delta function

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A survey of physical activity among urban women in China

Shilin DENG MD, Tongyuan LIU,

《医学前沿（英文）》 2009年第3卷第4期页码 463-469 doi: 10.1007/s11684-009-0081-y

摘要： Few studies have been conducted to assess the level of physical activity (PA) of women in China. The purpose of this study was to describe the prevalence of PA among women in Wuhan and explore sociodemographic and behavioral correlation to PA for the population. A total of 1359 community-dwelling women (42.9713.60 years old) participated in this study. The long-version IPAQ was used to define the level of PA. 45.7% of women were considered physically active, and 27.5% were vigorously active. The proportion of physical inactivity was around 26.8%. The total and 4 domains of PA showed significant age, education level, and occupation variation. PA tended to be lower as the age declined. PA in transportation, housework, leisure time, and the total tended to be the lowest or the second lowest among the women aged 18–35 years old. PA tended to be lower as the level of education increased. Among the 5 indices, PAwas the lowest among women with college education, especially those with postgraduate education. PA tended to be the lowest among the women of office staff and instructor or technician. Generally, the total and 4 domains of PA showed significant age, education level, and occupation variation. Physical inactivity appears to be more common among younger women, or college-educated women, office ladies, and female instructor and technicians.

关键词： physical activity urban women China

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Green Innovation for Urban Traffic

Yu Zhao,Sheng-quan Wang,Ke-chao Zhu

《工程管理前沿（英文）》 2015年第2卷第1期页码 35-38 doi: 10.15302/J-FEM-2015016

摘要： With the development of economy, the issue of urban traffic is becoming highlighted, the pollution of the urban traffic has become one of the main factors to influence environment. It faces the broader problem of achieving sustainable development of urban transportation at present. The current situation of urban traffic is analyzed through studying the existing articles at home and abroad in this paper; the problems such as green innovation of urban traffic are elaborated. In addition, this paper puts forward the relevant measures to promote the development of green innovation of the urban traffic.

关键词： urban traffic green innovation green transportation sustainable development

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Urban design based on public safety-Discussion on safety-based urban design

Kaizhen CAI, Jianguo WANG

《结构与土木工程前沿（英文）》 2009年第3卷第2期页码 219-227 doi: 10.1007/s11709-009-0023-4

摘要： Because of public safety problems in construction of urban surroundings, this paper expounds the necessity of the study on public safety-based urban design in perspective of modern city. It brings forward the concept of safety-based urban design and attempts to explore the basic connotation and contents with framework for studies.

关键词： urban public safety urban design safety-based urban design

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Coupling analysis of passenger and train flows for a large-scale urban rail transit system

《工程管理前沿（英文）》 2023年第10卷第2期页码 250-261 doi: 10.1007/s42524-021-0180-2

摘要： Coupling analysis of passenger and train flows is an important approach in evaluating and optimizing the operation efficiency of large-scale urban rail transit (URT) systems. This study proposes a passenger–train interaction simulation approach to determine the coupling relationship between passenger and train flows. On the bases of time-varying origin–destination demand, train timetable, and network topology, the proposed approach can restore passenger behaviors in URT systems. Upstream priority, queuing process with first-in-first-serve principle, and capacity constraints are considered in the proposed simulation mechanism. This approach can also obtain each passenger’s complete travel chain, which can be used to analyze (including but not limited to) various indicators discussed in this research to effectively support train schedule optimization and capacity evaluation for urban rail managers. Lastly, the proposed model and its potential application are demonstrated via numerical experiments using real-world data from the Beijing URT system (i.e., rail network with the world’s highest passenger ridership).

关键词： urban rail transit coupling analysis passenger–train interaction large-scale simulation

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A real-life stability model for a large shield-driven tunnel in heterogeneous soft soils

Xinyu HU, Zixin ZHANG, Scott KIEFFER

《结构与土木工程前沿（英文）》 2012年第6卷第2期页码 176-187 doi: 10.1007/s11709-012-0149-7

摘要： The current models that have been published to date only allow for homogeneous soil at the tunnel face. This paper presents a real-life face stability model to determine the minimal pressure needed at the tunnel face for a large shield-driven tunnel in heterogeneous soft soils. It is found that the influence of multilayered soil boundaries is significant, especially for the mixed-layer (e.g., sand and clay) soils. The suggested M-M model is developed by considering the influence of the heterogeneity of the soil on the angle of slip and the minimal support pressure. Comparisons of the solutions in mixed-layer soils are conducted, and the effects of the involved parameters for a large, multilayered, shield-driven tunnel are also investigated.

关键词： analytical solution shield-driven tunnel multilayered soil face stability

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Construction risks of Huaying mount tunnel and countermeasures

Haibo YAO, Feng GAO, Shigang YU, Wei DANG

《结构与土木工程前沿（英文）》 2017年第11卷第3期页码 279-285 doi: 10.1007/s11709-017-0414-x

摘要： The Chongqing-Guang’an motorway is planned to cross Huaying mount at Jingguan town of Chongqing city. The whole mount is a colossal anticline whose core is consisted of coal measure strata (upper Permian Longtan formation P l) and the limbs are limestone strata (middle Triassic Leikoupo formation T l and lower Triassic Jialingjiang formation T j). The tunneling is full of risks of collapse, gas explosion or gas outburst, water (mud) inrush, gas inrush because of existence of faults, high pressure gas, karst tectonics and coal goafs around the tunnel. In order to cope with the high risk, two main countermeasures were taken to ensure security of construction. One is geology prediction, and the other is automatic wireless real-time monitoring system, which contains monitoring of video, wind speed, poisonous gas (CH , CO, H S, SO ), people location, and automatic power-off equipment while gas contents being more than warning threshold. These ascertained the engineering safety effectively.

关键词： tunnel?construction gas?outburst geology?prediction automatic?monitoring?system