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Geomechanics and Engineering
  Volume 15, Number 2, June10 2018 , pages 721-728

The effect of radial cracks on tunnel stability
Lei Zhou, Zheming Zhu, Bang Liu and Yong Fan

    The surrounding rock mass contains cracks and joints which are distributed randomly around tunnels, and in the process of tunnel blasting excavation, radial cracks could also be induced in the surrounding rock mass. In order to clearly understand the impact of radial cracks on tunnel stability, tunnel model tests and finite element numerical analysis were implemented in this paper. Two kinds of materials: cement mortar and sandstone, were used to make tunnel models, which were loaded vertically and confined horizontally. The tunnel failure pattern was simulated by using RFPA2D code, and the Tresca stresses and the stress intensity factors were calculated by using ABAQUS code, which were applied to the analysis of tunnel model test results. The numerical results generally agree with the model test results, and the mode II stress intensity factors calculated by ABAQUS code can well explain the model test results. It can be seen that for tunnels with a radial crack emanating from three points on tunnel edge, i.e., the middle point between tunnel spandrel and its top with a dip angle 45o, the tunnel foot with a dip angle 127o, and the tunnel spandrel with 135o with tunnel wall, the tunnel model strength is about a half of the regular tunnel model strength, and the corresponding tunnel stability decreases largely.
Key Words
    tunnel; crack; numerical model; tunnel model test; stress intensity factor
Lei Zhou, Zheming Zhu, Bang Liu and Yong Fan: MOE Key Laboratory of Deep Underground Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China

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