Geomechanics and Engineering

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Crack behaviour of top layer in layered rocks

  • Chang, Xu (International Joint Research Laboratory of Henan Province for Underground Space Development and Disaster Prevention) ;
  • Ma, Wenya (School of Civil Engineering, Henan Polytechnic University) ;
  • Li, Zhenhua (School of Civil Engineering, Henan Polytechnic University) ;
  • Wang, Hui (School of Civil Engineering, Henan Polytechnic University)
  • Received : 2017.06.29
  • Accepted : 2018.03.15
  • Published : 2018.09.20
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Abstract

Open-mode cracks could be commonly observed in layered rocks. A concept model is firstly used to explore the mechanism of the vertical cracks (VCs) in the top layer. Then the crack behaviour of the two-layer model is simulated based on a cohesive zone model (CZM) for layer interfaces and a plastic-damage model for rocks. The model indicates that the tensile stress normal to the VCs changes to compression if the crack spacing to layer thickness ratio is lower than a threshold. The results indicate that there is a threshold for interfacial shear strength that controls the crack patterns of the layered system. If the shear strength is lower than the threshold, the top layer is meshed by the VCs and interfacial cracks (ICs). When the shear strength is higher than the threshold, the top layer is meshed by the VCs and parallel cracks (PCs). If the shear strength is comparative to the threshold, a combining pattern of VCs, PCs and ICs for the top layer can be formed. The evolutions of stress distribution in the crack-bound block indicate that the ICs and PCs can reduce the load transferred for the substrate layer, and thus leads to a crack saturation state.

Keywords

Acknowledgement

Supported by : National Natural Science Fund of China, Henan Polytechnic University

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