Numerical simulation of kink zone instability in fractured rock masses

This paper investigates the conditions favourable to the development of a kink zone instability in jointed rock masses in relation with joint properties such as friction angle, frequency of occurrence, and orientation. Numerical simulations using the distinct element code UDEC shows that kink zone instabilities develop when primary joints are oriented from 5° to 30° relatively to the major principal stress under confining pressures below 5.0 MPa. Also, results allow the definition of a failure criterion for kink zone instabilities based on geometrical properties related to the dilatancy rate. The failure criterion is τKZI=σntanψ where ψ is defined as the rotational dilatancy angle.