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Yao Z.,China Communications Construction Company Ltd.
Modern Tunnelling Technology | Year: 2015

Because of the complexity and uncertainty of geological conditions, risk assessments for the construction safety of underwater shield tunnels have become an important research topic in underground engineering. Based on the Nanjing Weisan Road river-crossing tunnel construction, this paper analyzes the identification of construction risk factors and evaluation of construction risks in the shield-driven section and formulates control measures for the various risk factors. The analysis results show that hyperbaric intervention in the shield chamber is the primary goal of risk control for such shield tunnels as the Nanjing Weisan Road river-crossing tunnel, which passes through mixed ground with high water pressure and permeability for long distances. Risk may be reduced by reducing the changing times of cutters, setting a reasonable face support pressure and ensuring the formation of a stable filter cake on the working face. Risk during the process of shield tunnelling is mainly controlled by the detection of shield tunnelling parameters and cause analysis of parameter anomalies while the shield machine is shut down; complete risk control measures, such as a risk emergency plan and emergency supplies, are also important measures for reducing risks. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Zhou Y.,Chongqing Traffic Engineering Supervision and Consultation Co. | Yang L.,China Communications Construction Company Ltd.
Modern Tunnelling Technology | Year: 2013

In this paper, the basic principles of risk analysis such as acceptable risk criteria and definitions, the calculation methods for individual risk, societal risk, and environmental risk are introduced. Types of highway tunnel disasters and their proportion of casualties are obtained and the most two common highway tunnel disasters (fires and vehicle collisions) are determined by statistical analysis of highway tunnel disasters at home and abroad. Based on investigations of some highway tunnel disasters and fire accidents in Britain, the F-N curve of those tunnels is drawn by means of F-N acceptable risk criteria; the effects of traffic patterns, traffic capacity, lane width, and vehicles on the probability of tunnel disaster are then analyzed.

Lv B.,China Communications Construction Company Ltd.
Modern Tunnelling Technology | Year: 2014

Considering the great strength and stability of medium weathered slate, the innovative arch-cover method was successfully adopted for the first time in construction of the large-span shallow-buried bored metro stations of the Dalian metro project. Based on the design and construction of the Zhongshan Square station, the core concept and advantages and disadvantages of the arch-cover method are compared with the PBA method in this paper. After completion of the primary support at the arch, the three different construction sequences of top-down, semi-top-down and semi-bottom-up, and bottom-up were analyzed and compared in detail from the aspects of safety, quality, progress, and additional measures. Results show that the top-down method was undoubtedly the most reliable when experience and relevant data are lacking. Countermeasures against construction problems, such as a large arch spring, arch support, medial plate, drill-blasting, and steel pipe column protection, as well as surrounding rock support for the high side wall, are put forward. Finally, the optimization suggestion of the arch-cover method is presented.

Xia R.,China Communications Construction Company Ltd.
Modern Tunnelling Technology | Year: 2014

Using domestic and foreign experiences in non-ballasted track construction and related technical documents as references and the double-block non-ballasted track construction of tunnel groups on the Gui-Guang railway as a background, the equipment configuration and organization of logistics for non-ballasted track construction for tunnel groups in mountain areas were studied and the related procedures for construction in a double-track tunnel are proposed in this paper. Engineering practices indicate that in-situ assembly of the track panel using a combined track framework could be adapted to adjust to the curve radius of the track and guarantee the technical indexes of non-ballasted track construction, therefore having rapid construction conversion capability. With high precision and stiffness, the assembled track framework is recyclable to shorten the construction period and save construction costs.

Tan Y.-Q.,Harbin Institute of Technology | Zhang L.,Harbin Institute of Technology | Gong W.-Q..,China Communications Construction Company Ltd. | Guo M.,Harbin Institute of Technology
Construction and Building Materials | Year: 2012

To protect the environment and reduce the consumption of energy, warm asphalt has been used widely in recent years. In this paper, Brookfield rotational viscometer test and dynamic mechanical analysis method are employed to investigate the effect of a kind of commercial wax named Sasobit® on the properties of three kinds of asphalt. It can be found that this kind of wax can increase the value of softening point, complex modulus, anti-rutting factor and reduce the value of the penetration and the phase angle; when the temperature is higher than 110°C, the Sasobit® modified asphalt has a lower viscosity, comparing with the original sample; when the temperature is lower than 70°C, the complex viscosity of Sasobit® modified asphalt is higher than the original sample, and the higher the Sasobit® content, the higher the complex viscosity. From the statistics analysis, it can be found that the effects of Sasobit® on rheological properties of asphalt are significant. © 2012 Elsevier Ltd. All rights reserved.

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