Luo X.,China Academy of Railway Sciences |
He F.,China Railway Southeast Research Institute Co.
Modern Tunnelling Technology | Year: 2014
Water bursts are one of the most serious geological disasters that can occur during the construction of long deep-buried tunnels, and their occurrences are closely related to the aquifer ahead of the working face or outside the free face. In this paper, the causes of water burst occurrences in long deep-buried tunnels are analyzed. Five kinds of structures and models are systematically presented: a highly fractured zone at upper wall of an uncemented and water-rich compressive fault; an uncemented and water-rich tensional fault zone; an uncemented and water-rich faulted bedding plane (a closely jointed rock mass); water-filling karst; and an underground water-bearing syncline structure and its water burst model. Moreover, disasters that occurred in five kinds of structures are analyzed through examples.
Zhang B.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2012
Simulation and line test on typical mountain railway of Xiang-Yu Line were conducted to study the feasibility and concerning problems for the operation of HX D1 (9 600 kW 8-axle locomotive) on line with long steep grades, based on which, reasonable tonnage of traction for this type of locomotive was provided for hauling freight train on typical mountain railway in western China. Study results show that the tonnage of traction for this type of locomotive should be no more than 4 500 t for line with 12.8‰ gradient. Under fine weather condition, the adhesion utilization of the locomotive is good, operations such as starting on slopes, stopping and starting at stations with difficult conditions can be successfully completed. But the traction force is applied to the utmost and slight slips are found. Operations including starting on slopes and operating in stations with difficult conditions are suggested to be avoided under unfavorable adhesion conditions, such as, light rain, dense fog and so on. Compared with DC driven locomotives, when hauling freight train of same weight, AC driven locomotives can save 33.6% energy. Moreover, the restoration of locomotive after neutral section is proved to be slow, which does not satisfy the requirement of quick restoration for operation on line with long steep grades. It is suggested to optimize the control logic of locomotive's neutral section passing.
Li Q.,Beijing Jiaotong University |
Ren S.,China Academy of Railway Sciences
IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews | Year: 2012
Discrete surface defects are the most common anomalies of rails and they should be carefully inspected. However, it is a challenge to detect such defects in a vision system because of illumination inequality and the variation of reflection property of rail surfaces. This paper presents an intelligent vision detection system (VDS) for discrete surface defects and focuses on two key issues of VDS: image enhancement and automatic thresholding. We propose the local Michelson-like contrast (MLC) measure to enhance rail images. MLC-based method is nonlinear and illumination independent; therefore, it notably improves the distinction between defects and background. In addition, we put forward the new automatic thresholding method-proportion emphasized maximum entropy (PEME) thresholding algorithm. PEME selects a threshold that maximizes the object entropy and meanwhile keeps the defect proportion in a low level. Our experimental results demonstrate that VDS detects the Type-II defects with a recall of 91.61% and Type-I defects with a recall of 88.53%, and the proposed MLC-based image enhancement method and PEME thresholding algorithm outperform the related well-established approaches. © 1998-2012 IEEE.
Yu H.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2013
In order to treat the diseases (such as base subsidence and mud pumping) in tunnel under the condition of heavy axle load train on certain existing railway, drilling combined with geophysical drilling detection methods were used for detecting the disease section of tunnel. Detection results show that the base plate of tunnel disease section is plain concrete and is thinner (25 cm or so). There is a weak interlayer of about 5 cm between the bedrock and concrete. The water content of the base in disease section is greater, which causes serious damage of base plate concrete. On the basis of mastering the present situation of tunnel base, treatment measure by combining well point dewatering and grouting is put forward. Through theoretical calculations, the numerical analysis of dewatering effect, construction feasibility analysis, and taking into account construction costs, the specific programs are determined as follows. Unilateral dewatering is adopted, and then well point system will be arranged in the lateral line of heavy vehicle. Fifty well points will be laid in 100 m disease section with the spacing of 2 m. Grouting is carried out at both ends of the sleeper in heavy vehicle line. Grouting pipe diameter is 60 mm, length is 2.0 m, spacing is 1.0 m, and grouting pressure is 0.3 MPa. After the treatment measure by combining well point dewatering and grouting has been implemented, the water level of the tunnel base in this section always keeps at about 1.5 m under the base. No such diseases as base subsidence and mud pumping occur, which indicates that the measure is very effective.
Tao X.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2013
In order to study the influence of different structures on the stress and the fatigue performance of orthotropic steel bridge deck, three section models were designed and the static and fatigue tests were carried out. Results show that the thickness of bridge deck has significant influence on the stress of the attachment weld between bridge deck and U rib. We suggest that the thickness of bridge deck should be more than 14 mm. The spacing of diaphragm plates directly influences the out-of-plane stress of the intersection between diaphragm plate and U rib attachment weld, the out-of-plane deformation of diaphragm plate and the vertical deformation of middle U rib. The stress of arc opening decreases with the increase of the thickness of diaphragm plate. The crack of orthotropic steel bridge deck caused by secondary stress grows slowly, and will not directly affect the bearing capacity of the whole bridge deck. It is disadvantageous to the fatigue performance of orthotropic steel bridge deck that welding holes are left in the upper intersection between the diaphragm plate and U rib.