Microfractographic study of heated and non-heated Stripa granite

Microfissures of thermal origin were investigated in granite rock specimens, taken from the area of a heater test performed at the Stripa Test Site in Sweden. Optical and electron microscope techiques were simultaneously applied to obtain a complete information of the rock microfractography related to the texture and mineralogy. This microfractography network was quantified by digital image processing. Original microphotographs were digitized by a flat microdensiometer. Then, segmentation, thinning and line-following algorithms were successively applied for enhancing, detecting and measuring the microfissures. The described technique was applied to material subjected to one, slow in situ heating cycle reaching a maximum temperature of about 2200C and to non-heated material taken from the same area. No significant differences in the fissuration density were detected when comparing heated and non-heated material. (author)