ISSN - ISRM

8 ISRM (India) Journal4.0 PETROGRAPHIC CHARACTERIZATION OF THETESTED ROCKThe rock types are identified by the names of theirrespective locations. The colour, texture andmineralogical description are used to emphasise itspredominant characteristics using macroscopic andmicroscopic petro-graphic analysis of the rock selectedfor testing. Detailed information is provided in thefollowing sections.4.1 Macroscopic CharacterizationThe macroscopic petro-graphic characterization ofseveral randomly chosen rock specimens was carriedout for all types of rock samples tested and is presentedin Tables 2 to 4. After consulting these tables, it is foundthat these rock specimens were affected by coal intrusion,discontinuities and other geological disturbances. It isobserved from the failed specimens in fatigue loadingthat traces and intrusion of coal fragments vary fromspecimen to specimen (Fig. 3). From Table 2, it is seenthat tested rock specimens are comprised of a widevariety of minerals and textures, ranging from fine grainedto coarse grained rocks, light gray to gray and whitishgray compact sandstone, as well as fine-gravel tomedium-gravel grey conglomerate with matrix formed bysandstone etc. As it was found out, the tested rockspecimens also had disturbance in terms of coalfragments, unoriented clast of coal, and other organicmaterials. In some cases, matrix was formed byconglomerate. This means that the tested rock specimensshowed mineral content variation from specimen tospecimen. This was also proved by X-Ray diffractionanalysis, a result of which is provided in the followingsection.Fig. 3 : Sample disturbance in terms of coal intrusion in one of the tested rock specimenTable 2 : Macroscopic petrographic characterization of rock samples and specimens from borehole Darkov 265-01Sample/Specimen No. Macroscopic petrographic characterizationD1/233 Medium-grained to coarse-grained, grey sandstone containing unoriented clasts of coal (up to 3cm).D1/310 Medium-grained, light grey sandstone with streaks (accumulated organic mass). The streaks aresporadically convergent, oriented diagonally (round 25°) to the axis of the core.D2/15 Medium-grained, light grey, compact sandstone, with rare content of fragments (2 mm.Volume 1 v No. 1 v January 2012