Institut za rudarstvo i metalurgiju Bor

directly connection to the water level
change in the river. In the period of low
water, the drainage of aquifers is done by
highlighting the river, or stream, or trickling
through the part where alluvial sediments
deposited over the limestone where they
supply the fracture - karst aquifer. Thickness
of gravel and sand range from 0.30 – 2.55 m
and the average of 10 drillhoeles was 1.60
m. In the northern and north-western part of
the open pit “Potrlica”, the inner waste dump
was formed. The roof marls and accompanying
deposits of thickness over 25 m are
dumped. Before dumping, in the space of
the internal dumps, two sources at bench
levels of 708 and 704 m were registered.
Over them, the mined masses were dumped
without drainage, and they affect the aquifer
feeding in the dumped masses, which is
drained over resources in its foot.The estimated
aggregate yield of the source is approximately
10 l/s. The area where the
dumped masses lay over sloping surface of
limestone, the aquifer drainage is also done
in the limestone massif.
Fracture type of aquifer is in the roof
marls but also in the coal layer. Average
thickness of marl is 41 m and maximum
131 m. The marls are bedded and various
fall of 15-48º.The fracture of rocks in the
surface area is larger than the deeper areas.
Marls cover an area of 7 km 2 , which
coincides with the distribution of surface
carbon layer. Aquifer feeding is done by
the infiltration of atmospheric water, infiltration
from alluvion of the river Ćehotina
and infiltration of water from the Triassic
limestone deposits in the rim area (the
accumulation of “Durutovici”). Drainage
of aquifers is leakage from the frontal
prominence of groundwater along the
floor or a concentrated source of contacts
along light gray fractured and dark gray
compact marls as well as on a contact of
the main coal layer and its roof. The yield
zone of sources varies. Mapping registered
multi areas of leakage and expiration
of the highest to the deepest levels of
work in the southern part of the mine yield
of 1 l / s to over 10 l / s. The aquifer in the
marls was released in the free level. The
depth to aquifer is 50-50 m. In the coal
series its thickness is 20 m, where in addition
to the main layers two or three carbon
layers, thickness up to 15 m, the fractured
aquifer was formed. Aquifer was formed
in the part where the actual tectonic fissures
and fault systems are. The main water
supply comes from aquifers from the
eastern and central part of the basin, on
the south of mining front of the open pit
“Potrlica”, where the coal layer lies directly
on limestone. Feeding the aquifers
in the coal is also possible from the roof
marls, but they are weaker sources in the
feeding compared to the karst aquifer.
Karst type of aquifers is in Triassic limestone,
and the space of open pit “Potrlica”
is just a part of large and spatial accumulation
which covers an area of 500 km 2 .
Limestones are substratum of Neogene
deposits throughout the basin, and also
built the northern and eastern edge of the
basin. By prospecting drilling, the limestones
are only bored, and in the majority
of cases the drill holes were ended in the
Neogene, so it is estimated that the thickness
of limestone is several hundred meters,
while the base of karstification is not
clearly defined. The area where the limestone
was discovered, the aquifer is with a
free level. The sources “Tvrdaš” and
“Kutlovača “, the characteristic of karst
was confirmed that the open pit drops to
the next level of outflow. Due to the exploitation
of source “Tvrdaš” and periodical
source “Kutlovača“, the elevation levels
of outflow were dropped from 775.3 m
to 660 m, resulting in an overall lowering
the open pit in the karst aquifer. The area
where the limestone is covered by Neogene,
the open pit is subarteritic. The presence of
karst groundwater is found in every drill
completed in the basin substratum. Groundwater
level oscillations were mild and consistent
with clear influence rainfall. For this area
the average amount of precipitation 795.2
mm/year, and the quantity of most dives and
No 1,2010. 96
MINING ENGINEERING