Rock fracture under anti-plane shear (Mode III) loading

  • Rao Qiu-hua Email author
  • Liao Zhen-feng 
Geology, Mining And Civil Engineering


Anti-plane punch-through shear test and anti-plane four-point bending test are used to study the crack initiation and propagation under anti-plane shear (Mode III) loading. The tensile and shear stresses at the crack tip are calcualted by finite element method. The results show that under Mode III loading the maximum principal stress σ1 at crack tip is smaller or a little larger than the maximum shear stress τmax. Since the tensile strength of brittle rock is much lower than its shear strength, σ1 is easy to reach its critical value before τmax reaches its critical value and thus results in Mode I fracture. The fracture trajectory is helicoid and the normal direction of tangential plane with the fractured helicoid is along the predicted direction of the maximum principal stress at the notch tip. It is further proved that Mode I instead of Mode III fracture occurs in brittle rock under Mode III loading. The fracture mode depending on the fracture mechanism must be distinguished from the loading form.

Key words

Mode III loading Mode I fracture fracture mechanism finite element method rock 

CLC number

O346.1 TU458 


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Copyright information

© Central South University 2005

Authors and Affiliations

  1. 1.School of Civil and Architectural EngineeringCentral South UniversityChangshaChina

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