TRANSPORT TREATMENT OF CRACK POPULATION IN FINITE MEDIUM .2. DAMAGE BEHAVIOR IN DIFFERENT ZONES

Extensive graphical results are given of a non-linear transport equati on approach (derived and described in part I of this work) for crack p opulation in a spherical medium surrounding a charged borehole. The ce ntral quantity numerically computed by time integration is the ''damag e'' or the total volume associated with the cracks. Typically, intensi ve cracking (large damage) appears near the borehole and close to the surface (spalling), where the detonation pulse becomes (upon reflectio n) tensile. The extents and quantities of damage in these two zones ar e given as functions of the sample size, initial crack distribution, a ttenuation length and the form of the pulse. An interesting result ari sing from this non-linear method is the disappearance of the spall zon e in spite of the relatively strong tensile part of the wave. This phe nomenon is caused by the increased attenuation of the tensile pulse (o n its way to the surface) due to the large number of cracks (either in itially present or formed later). Copyright (C) 1997 Elsevier Science Ltd.