A comparative study on unfilled and filled crack propagation for rock-like brittle material

The mechanical behavior of rock is strongly dependent on its embedded discontinuities such as cracks and joints. Natural rock joints are found to exist mostly with filling materials such as sand or clay as weak bond. The filling has been observed in engineering practice to have influence on rock failure behavior. To investigate this topic, the crack propagation behavior of the filled and unfilled crack is studied and compared by testing rock-like specimens subjected to uniaxial compression. A qualitative analysis of the crack propagation paths is described where crack is classified into four types, namely the original, secondary, wing and anti-wing cracks. The experiments indicate the crack initiation time, initiation location and propagation behavior are different between filled and unfilled joints. The experimental results also showed that the peak stress for filled joint is higher than for the unfilled. Numerical tests simulating the experimental process are carried out using the extended finite element method (XFEM) to explore complementary explanations and provide proofs to the experiments.