Xie Xiongyao

Risk Assessment of Voids behind the Lining of Mountain Tunnels

Accidents caused by lining damage are commonly faced problems of tunnels. These accidents may have detrimental effects on drivers and cars in the form of injury, disability, etc. One of the main causes of lining damage is void behind the lining. This study proposes a risk evaluation methodology for assessment and management of risk associated with void behind lining. In the proposed methodology, risk assessment requires the determination of probabilities and possible consequences. In order to define probability, a statistical method is used; and to define consequence, a finite element analysis is carried out; finally, the proposed method is illustrated with an example and it is found to be useful to evaluate and manage such risks.

Development of radar antennas for the detection of voids behind tunnel liner and laboratory experiments

Ground penetrating radar antennas used for voids detection in the tunnel are almost ground-coupled, which leads to a slow detection speed, and also was greatly affected by the surrounding environment and operation factors, to improve the detection speed and reduce the effect of surrounding environment, the air-coupled antenna, Vivaldi antenna I was chosen, and a series improvement were proposed, finally two kinds of novel Vivaldi antennas were introduced, namely, Vivaldi antenna II and Vivaldi antenna III, the performance of the antennas was investigated numerically, and to test the performance of the antennas, some model detection experiments are carried out, and the detections results of Vivaldi antennas also was compared with the results of commercial antennas, the results indicate that the novel Vivaldi antennas are as good as commercial antenna, and Vivaldi antenna II and III has a better performance than Vivaldi antenna I, and Vivaldi antennas are air-coupled, the detection results will be better if there is a certain distance between the antenna and the tunnel lining, which provides feasibility for fast detection of tunnel disease.

Evaluation of Bogie Frame Safety of Shanghai Metro Line 1 by 3D FEM Analysis

The vehicle bogies of Shanghai metro line 1 began to crack just in the third year after the trains operated. More than 50 cracks occurred in the succeeding six year during the train operation. This paper evaluated the safety of the motorized bogies. First, the loading conditions imposed on the vehicle structure were calculated based on the measured data in service of the train, and compared with the original design load. Then, this paper calculated simulated the stress of the vehicle bogie by 3D FEM, and presented the distribution of every stress concentration point in Goodman fatigue diagram. The computational locations of the strength less than the safety are agreed with where cracks have happened. Finally, this paper calculated the fatigue life of the motor bracket of the bogie through S‐N curve based on revised Miner theory. In conclusion, this paper think that the bogie cracks of Shanghai metro line 1 are contributed by the overburden fatigue load, and ignoring the lateral vibration load in the desig...