The recent theories and many modeling attempts in the field of sciences which originated in the XXth century put forward the idea of informational fields as an objective necessity when it comes to explaining numberless phenomena having non-standard behaviour. The existence of informational fields is conditioned by information transmission and by the informational feedback. For this reason the basic instrument that we are going to use within this modeling is informational feedback defined by accurate means. Results show that rock joints can significantly affect the transmission and the attenuation of shock waves, and can therefore influence the stability of the adjacent underground structures. The spacing of joint set can also remarkably affect the propagation process. It indicates that as a discontinuum-based approach, fractal theory is good at simulating the propagation and attenuation of blasting wave in jointed rock masses, and in modeling the stability of underground structures subjected to blasting loads.
Blasting loads resulting from detonation have been attached great importance to the design and protection of underground structures in these years. In order to analyze the dynamic response and stability of underground structures, a number of numerical approaches such as FEM and BEM have been introduced. However, numerous discontinuities existing in the rock masses in the forms of faults, joints or bedding planes (Goodman, 1976), on the one hand, can dominate the mechanical response of rock masses to blasting loads; on the other hand, the conventional numerical methods employed in the simulation are usually continuum based. As a result, it is not very easy for these methods to give reasonable predictions. Discrete element method (DEM), a discontinuous model for simulating fractured rock masses (Cundall, 1971), can be an alternative. At the early stage, DEM was mostly employed to simulate static problem. In 1987, Lemos developed a numerical technique to study the dynamic response of a jointed rock mass (modeled as an infinite elastic medium with a single discontinuity) subjected to a line source of incident waves (Lemos, 1999). He demonstrated the validity of the numerical technique. Chen S G, et al employed the UDEC and 3DEC to model shock wave propagation in rock masses, and reported that reasonable results were obtained by using the velocity history obtained from another code, AUTODYN. In this study, the shock wave propagation as well as the response of underground structures to farfield detonation in jointed rock masses are investigated through two case studies by using the fractal theory. Fractal results are compared with test data, and some conceptual conclusions are drawn accordingly.