Li W.-B.,China Railway First Survey and Design Institute Group Co.
Journal of Railway Engineering Society | Year: 2013
Research purposes: To adapt the terrain condition of mountainous area, the large longitudinal slope often has to be built to the highway in mountain area. For building the large longitudinal slope, there are many restrictions stipulated in the specifications at home and abroad. However, the traffic accidents caused by the braking failure of the heavily loaded vehicle in down slope still happen from time to time. The investigation shows the incidence of the traffic accident happened in the large longitudinal slope in France is much lower than China because the French specifications are more rational and effective. Based on inducting and analyzing the cases, this paper analyzes the reason for the braking failure of the heavily loaded vehicle in down slope, presents the risk indicators of the large longitudinal slope based on referencing the current French specifications and relevant provisions and gives the measures for reducing the driving risks for the purpose of providing the reference to highway design. Research conclusions: In the highway's section with the large longitudinal slope of more than 3%, the gentle slopes should not be designed frequently. The emergency lane should be built when the elevation difference of one large longitudinal slope reaches at 130 meters. In addition, the warning signs should be added and the slow lane should be built in the conditional section to reduce the driving risk and protect the driver and the other people.
Dai Z.,China Railway First Survey and Design Institute Group Co.
Zhongguo Tiedao Kexue/China Railway Science | Year: 2013
On the premises of ideal simultaneous backfill grouting, and without regard to the influences of the change of grout characteristics, the upward movements of segments in three-dimensional annular space at the rear of shield tail were researched. The upward buoyancy acted on segments was divided into two parts, namely, the generalized dynamic buoyancy changing with ground conditions and buried depth of tunnel, and the static buoyancy depending on surrounding liquid grout. The formulas of the two types of upward buoyancy were derived. The dynamic buoyancy existed for a long time within certain distance range at the rear of shield tail. The action range of static buoyancy was given based on the change law of the grout pressure gradient in the cross section of tail void. On the basis of the whole floating mode of the segments at the rear of shield tail, and considering the longitudinal constraints between segments, the expression for the least yield strength of grout was obtained to maintain the anti-floating stability of tunnel. The decisive role of the yield strength of grout on maintaining the anti-floating stability of tunnel was made clear, and the positive role of surrounding pressure on improving the yield strength of grout was also made clear.
Zhao L.,China Railway First Survey and Design Institute Group Co.
Modern Tunnelling Technology | Year: 2013
Full-face tunnel boring machines (TBMs) can be classified as open, single shield, double shield, and compound machines. The proper selection of a TBM is key to guaranteeing the safe and rapid construction of urban rail transit projects. This paper describes the principles for TBM selection and, using the Chongqing metro line 6 as an example, the most appropriate TBM is selected after an analysis of the alignment conditions, tunnel depths, geological and hydrological conditions, tunnel operating requirements, support and lining forms, and construction schedule and costs for this specific line. It is recommended that open TBM option is preferred than compound TBM option for an urban rail transit project in hard rock.
Yu J.,China Railway First Survey and Design Institute Group Co.
Modern Tunnelling Technology | Year: 2014
Based on experience from the Qinling tunnel on the Xi'an-Ankang Railway and the application of a TBM in the Zhongtianshan tunnel at the Turpan-Korla section of the Southern Xingjiang Railway Line 2, the adaptability of TBMs is analyzed considering the topographical and geological conditions of the Zhongtianshan tunnel. According to the geological parameters and advance rates measured in the survey, design and construction stages, the effects of geological factors on TBM advance efficiency is discussed and an approach for adapting a TBM to geological conditions and improving the advance rate by specific measures is analyzed. The results show that the geological properties of surrounding rock greatly affect TBM advance efficiency and that an effective way to improve advance efficiency includes adopting high-quality wear-resistant cutting tools and increasing the gross thrust of the TBM.
Zhang J.-E.,China Railway First Survey and Design Institute Group Co.
Journal of Railway Engineering Society | Year: 2014
Research conclusions: (1) The integrated design of Xi'an North railway station and subway station is analyzed from the planning, organization, location choosing and structure adaptability, the problems and experiences of integration organization and implementation are introduced. (2) Xi'an North railway station uses the model of the "the unity of buildings and bridges", fuses three kinds of structure form of building on the ground, bridges and subway structure. Combination of the whole subway and railway hub satisfies the requirement of long span and large space in the big passenger distribution place. (3) A variety of layout patterns are summarized, and have the reference value for all types of integrated transport hub design.Research purposes: In order to improve the overall transfer efficiency and function space security comfort of the integrated transport hub, the various transportation transfer relationships need to be studied, to avoid the various separated space, the complex indicating system and the long walking distance. How to combine the overall planning, achieve the design and synchronous implementation and integrated transport hub, reasonable arrangement of the location about the subway stations, to achieve rapid evacuation of large passenger flow, which is a key problem in the design of integrated transport hub. ©, 2014, Editorial Department of Journal of Railway Engineering Society. All right reserved.