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Peng J.,Chang'an University | Peng J.,Key Laboratory of Western Chinas Mineral Resources and Geology Engineering | He K.,Chinese Academy of Geological Sciences | Tong X.,Chang'an University | And 3 more authors.
International Journal of Geomechanics | Year: 2017

Failures of metro tunnels that pass obliquely through ground fissures at low angles are a common problem; however, their mechanism is unknown. In the city of Xi'an, China, Line No. 3 of the Xi'an Metro intersects ground fissures at a low angle (<25°) in certain zones. In this study, particle flow numerical analysis and physical model tests were used to investigate ground-surface deformation, structural distortions, and failure characteristics caused by ground fissures. Tests revealed an integrated bend-shear-torsion failure mode of any tunnel that entered a ground fissure obliquely at an angle of 20° or less, under the action of activities associated with a ground fissure. The tunnel structure indicated damage characterized by long longitudinal cracks and multiple groups of subparallel vertical cracks. The range in failure of the tunnel was up to 3.5 times the tunnel diameter on the hanging-wall side and up to 4.5 times the tunnel diameter on the foot wall. When metro tunnels intersect ground fissures at low angles, traditional tunnel designs do not meet minimum safety standards. It is therefore necessary to explore alternative metro tunnel designs in fissure-prone areas. © 2016 American Society of Civil Engineers.

Bai C.-Y.,Chang'an University | Bai C.-Y.,Key Laboratory of Western Chinas Mineral Resources and Geology Engineering | Zhao R.,Chang'an University | Greenhalgh S.,ETH Zurich | Greenhalgh S.,University of Adelaide
Pure and Applied Geophysics | Year: 2010

A novel hybrid approach to earthquake location is proposed which uses a combined coarse global search and fine local inversion with a minimum search routine. The method exploits the advantages of network ray tracing and robust formulation of the Fréchet derivatives to simultaneously update all sampled initial source parameters in the solution space to determine the best solution. Synthetic examples, involving a three-dimensional (3-D) complex velocity model and a challenging source-receiver layout, are used to demonstrate the advantages over direct grid search algorithms in terms of solution accuracy, computational efficiency, and sensitivity to noise. Therefore, this is a promising scheme for earthquake early warning, tsunami early warning, rapid hazard assessment, and emergency response after strong earthquake occurrence. © 2010 Birkhäuser / Springer Basel AG.

Peng J.-B.,Chang'an University | Peng J.-B.,Key Laboratory of Western Chinas Mineral Resources and Geology Engineering | Chen L.-W.,China Nuclear Power Engineering Co. | Huang Q.-B.,Chang'an University | And 6 more authors.
Engineering Geology | Year: 2013

Numerical modeling and physical simulation experiment are two important steps to investigate the stress and strain fields of overlying strata, but sometimes it is very difficult to do the test of the physical experiment on a large-scale soil sample due to the financial consideration and the available test site. To investigate the features of the ground fissures prevailing in Xi'an City, we undertook in this study a series of physical simulation tests on the large-scale soil sample to analyze the stress and displacement fields caused by the underlying normal fault activity. Comparing with the fracturing modes of the ground fissures and the failure patterns of construction building, it is evident that the experiment results coincide with the failure patterns of the building, but not with the fracturing modes of the ground fissures, which indicate that the ground fissures in Xi'an may be an old fracture surface having already spread to superficial layer covered by a very thin layer of loose soils, and the groundwater over-pumping is just a factor to make them exposed on the ground surface. © 2013 Elsevier B.V.

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