chapter - 1 introduction - Meghalaya State Pollution Control Board

Hills Cement Co. Limited.
The pattern of drilling and blasting has been designed as follows:
Proposed bench height : 6.0m
Proposed diameter of hole : 100 mm,
Effective depth of hole : 7.0m
To maintain good fragmentation
for quick removal of blasted
muck, suggested burden : 3-3.5m
Spacing : 4.0-4.5m
Stemming column : 3.0-3.5m
Tonnage of rock per hole : 236 tonnes.
Impact on stability of slopes
Rock slides in and around the vicinity-
There are no visible signs of rock slides around the vicinity of the mine
and no tension cracks or loosened boulders are present. The mining
activity will have adverse impact on the slope stability, if appropriate
control measures are not adopted. Controlled blasting shall be adopted
to avoid tension cracks and back breaks. Such crack filled with water
reduces stability of excavated slopes and angle of slopes. Good
drainage shall be provided in and around the quarry.
Rolling boulders
When mining of a bench reaches the edge of the hill, it may give rise to
rolling of boulders downwards along the hill slopes. It may have
adverse impacts on flora and structures on the way. It may also lead to
serious injuries to human beings or animals. Adequate control
measures as given below have been proposed to prevent this
phenoena.
On end bench 8m from the edge is to be considered as “Caution Zone”.
Regular mining shall not be done in the zone. The orientation of the
face will be kept parallel to the edge of the hill in the area and the
bench height is restricted to 2m only. Controlled blasting will be
adopted for the last blast. Pre-splitting will be done, if required.
Pollution Control Consultants (India) Pvt. Ltd. 78