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Shi Y.,China Institute of Technology | Li Z.,Inner Mongolia Joint Venture Road and Bridge Ltd Liability Company | Li J.,Inner Mongolia Joint Venture Road and Bridge Ltd Liability Company | Sang Y.,Shanghai Tong Yan Civil Engineering Ltd.
Modern Tunnelling Technology | Year: 2014

Based on the rock joint characteristics of the Gaozhushan tunnel in Yushan county, a 2D calculation model is established using the discrete element software UDEC, and the effects of the joint dip angle and joint spacing on tunnel deformation under two sets of joint couplings is studied by calculating the vault collapse heights in different conditions. Results show that by increasing the joint dip angle, the collapse height decreases (30° to 45°) after initially increasing (0° to 30°), and then increases again (45° to 90°); the calculated collapse height is closest to PU's theoretical value when the dip angle is 60°; and with an increase in joint spacing, the collapse height decreases nonlinearly. When the joint spacing is 0.2~1.0 m, the collapse height can be calculated with equation (1) and the calculated value is closest to PU's theoretical value when spacing is no more than 0.2m. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

Yu W.,Jiangxi Highway Investment Group Co. | Yu W.,Changsha University of Science and Technology | Sang Y.,Shanghai Tong Yan Civil Engineering Ltd.
Modern Tunnelling Technology | Year: 2014

A model plain concrete lining structure with longitudinal cracks in the vault (with a crack depth of one-third of the original lining thickness) was made of gypsum at a similarity ratio of 1:10 and a superimposed concrete cover arch was adopted for reinforcement. After curing, loose earth pressure was applied in a graded manner on the crown by means of indoor peripheral radial loading appliances to study the bearing capability and failure law of the cracked lining reinforced by a superimposed cover arch by considering the effects of stratum resistance. Testing results show that the deforming process of the cracked lining under loading undergoes three stages after reinforcement of the superimposed cover arch: initial loading - cracking of the cover arch vault; cracking at the cover arch vault - cracking at the superimposed interface; and cracking at the superimposed interface of the vault - specimen failure. The sequence of key position failure is: cracking on the vault, ductile failure of the vault, and brittle fracture of the haunch; the failure mode is generally ductile in nature. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

Sang Y.,Shanghai Tong Yan Civil Engineering Ltd. | Li J.,Inner Mongolia Transport Design and Research Institute | Liu X.,Tongji University
Modern Tunnelling Technology | Year: 2015

In this paper, based on the construction of the Yaogou tunnel in Hohhot, the characteristic parameters of approximate horizontal and vertical developed joints are collected for areas of the typical section; additionally, the kinematic behaviors and force characteristics of the overlaying rock are analyzed and the deformation and instability patterns of the surrounding rock are studied by adopting field monitoring, a laboratory model test and numerical simulation. The results show that: 1) without support, the stability of the strata is very poor during construction with the caving and loosening zones concentrated above the vault, of which the maximum caving height is 0.48 times the tunnel width, the caving area is 0.51 times the section area, the equivalent load of the vault is 0.084 MPa and the loosening zone extends to the ground surface in an almost triangular distribution; and 2) with a primary lining, the loosening range of the strata is significantly reduced, with a maximum caving height of 1.1 times the tunnel width, and the maximum settlement of the vault is reduced to 7.7 mm and the sidewall convergence becomes 3.4 mm. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

Liu X.,Tongji University | Li X.,Tongji University | Sang Y.,Shanghai Tong Yan Civil Engineering Ltd. | Lin L.,Chongqing Construction Science Research Institute
Tunnelling and Underground Space Technology | Year: 2015

Understanding earthquake fault rupture propagation is important in building and lifeline engineering, especially in the construction of mountain tunnels. Thus, studying rupture propagation in strata and tunnel failure with fault displacement is significant. For this purpose, an experiment has been designed to simulate normal fault displacements with different dip angles. The influence of normal faults on tunnels has been observed by examining the rupture and strata deformation and analyzing the shear zone, tunnel stain, position, and forms of tunnel cracks. The results show that more than one strata rupture appears when the normal fault moves, and at least one rupture reaches the ground surface as the vertical fault dislocation is approximately 4.4% of the covering depth. In general, those ruptures form an inverted triangle zone in which strata deform significantly. The range of the rupture shear zone increases as the fault dip angle decreases. Strata-tunnel -fault can be considered as a beam on an elastic foundation. The lining of the tunnel in the hanging wall and shear zones is subjected to sagging, and that in the foot wall zone is subjected to hogging. Failure modes appear to change with fault dip angle. The lining damage form is flexure failure occurring mainly in the foot wall with the circumferential cracks, when the dip angle is 75°. When the dip angle is 60° and 45°, the failures are caused by a combination of flexure and shear both in the shear and foot wall zones with a lot of circumferential and diagonal cracks. Furthermore, to guide design work reasonably, the calculation method in determining the weak parts of the tunnel and feasible reinforcement measures are discussed. © 2015. Source

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