Experimental study on time-dependent stress and strain of in-plane shear (Mode II) fracture process of rock
Zhi Wang , Qiu-hua Rao , Hai-feng Xie
Journal of Central South University ›› 2010, Vol. 15 ›› Issue (Suppl 1) : 496 -499.
Experimental study on time-dependent stress and strain of in-plane shear (Mode II) fracture process of rock
Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear (Mode II) fracture process of rock and to reveal the mechanism of Mode II fracture. Numerical results show that the maximum shear stress τmax at the crack tip is much larger than the maximum tensile stress σ1 and the ratio of τmax/σ1 is about 5, which favors Mode II fracture of rock. Test results indicate that the strain-time curve comprises three stages: the linear deformation stage, the micro-cracking stage and the macroscopic crack propagation. The strain in the direction of the original notch plane is negative, due to restraining effect of compressive loading applied to the original notch plane. Both σ1 and τmax are increased as the load increases, but the slope of τmax is larger than that of σ1 and the value of τmax is always larger than that of σ1. Therefore, τmax reaches its limited value at peak load before σ1 and results in Mode II fracture of rock. Shear-box (i.e. compression-shear) test becomes a potential standard method for achieving the true Mode II fracture and determining Mode II fracture toughness of rock.
time-dependent stress and strain / Mode II fracture / strain measurement / fracture mechanism / finite element method / rock
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