The Toki granite has been classified into three zones by Iwatsuki and Yoshida ([1999]) based on the intensity of fracturing and fracture widths: an intact zone, a moderately fractured zone, and an intensely fractured zone.
A vertical fracture zone also forms between the caved zone and fractured zone above the gob.
The height of the caving zone and the freely flowing water fractured zone of different mining thicknesses were separately calculated.
The longest naturally fractured zone is located between 1,170- and 1,215-m 1,215-mndepthchandcterised by euhedral barite, galena, pyrite, and geodicharacterized
A 0.4 m fractured zone at roof holes was ignored and thus the maximum strength of the coal was 17.85 MPa, the minimum was 7.65 MPa, and the average was 12.43 MPa.
The results show that a mining thickness greater than 3.5 m causes the height of the freely flowing water fractured zone to be sufficient to touch the weathered zone and the bottom of the Quaternary system aquifer, to various degrees.
Finally, a linear relation was derived between energy of approximated section of water saturation log and fracture density, allowing us to estimate the number of fractures in each fractured zone.
At this point, it remains unclear as to the influence of geomechanical properties on fracture stimulation and its effective permeability, nature of the fractured zone (whether single extensive fracture or network), and extent of fractured zone.
The moderately fractured zone has relatively thin fractures with minor alteration of the rock matrix, and the dominant fracture-filling minerals are smectite and chlorite.
Additionally, bedrock of just one location is fractured, and this is at Idere, and the fractured zone occurs at shallow depth of 5.8 m (Table 5, Fig. 9).
After the well drilling has been completed, hydraulic fracturing would be adopted to form a fractured zone in the coal seam.
