This document discusses mine dewatering and groundwater control. It describes various approaches to dewatering such as exclusion methods using cut-off walls or grouting, and pumping methods using wells, drains or sumps. Both open pit and underground mines are addressed. The key aspects of successful mine dewatering projects are explained as understanding the hydrogeology, appropriate dewatering technology, and environmental considerations.
3. www.preene.com
PRACTICE PROFILE
Preene Groundwater Consulting is the Professional Practice of
Dr Martin Preene and provides specialist advice and design
services in the fields of dewatering, groundwater engineering
and hydrogeology to clients worldwide
Dr Martin Preene has more than 25 years’ experience on
projects worldwide in the investigation, design, installation and
operation of groundwater control and dewatering systems. He is
widely published on dewatering and groundwater control and is
the author of the UK industry guidance on dewatering (CIRIA
Report C515 Groundwater Control Design and Practice) as well
as a dewatering text book (Groundwater Lowering in
Construction: A Practical Guide to Dewatering)
4. www.preene.com
MINE DEWATERING
There are 3 aspects to the design and implementation of mine
dewatering
An understanding of:
• Hydrogeology
• Dewatering technology
• Environmental sensitivities
5. www.preene.com
MINE DEWATERING
There are 3 aspects to the design and implementation of mine
dewatering
An understanding of:
• Hydrogeology
• Dewatering technology
• Environmental sensitivities
7. www.preene.com
WATER MANAGEMENT FOR MINING
Water Management
Treatment if necessary
PumpingExclusion
Groundwater controlSurface water control
Diversion Pumping
Disposal to
Waste
Environmental
Mitigation
Beneficial
use
On site Off site
8. www.preene.com
WATER MANAGEMENT FOR MINING
Water Management
Treatment if necessary
PumpingExclusion
Groundwater controlSurface water control
Diversion Pumping
Disposal to
Waste
Environmental
Mitigation
Beneficial
use
On site Off site
20. www.preene.com
UNDERGROUND METHODS
• In underground mines, the conventional approach is to use the mine itself to
control groundwater, by allowing the workings to act as drains
• Once the water is in the mine it is passed along roadways (by pumping or gravity)
to a deeper part of the mine (sump) or shaft bottom, to be pumped out via shaft
or decline
• Due to depth there may be a need for staged pumping to get the water out of the
mine
• In hard rock mines drain holes may be
drilled out from workings
• Important to minimise ‘dirty water’
(that has run along the floor/walls)
and segregate ‘clean water’ (that has
come straight from drain holes),
because the water treatment
requirements are different
21. www.preene.com
UNDERGROUND METHODS
• Where fractured or water bearing zones are encountered,
exclusion methods can be used to reduce water inflows.
Grouting to seal inflow pathways is the most common
approach
• Grouting may be:
– Planned or responsive
– From surface (limited depth) or from workings (interferes with mining)
• Most common type of grout is cementitious based grouts, but
problems with grouting through flowing water and may be
washed out before they set
• Specialist chemical ‘water stopping’ polyurethane grouts are
available to deal with flowing water but are expensive
22. www.preene.com
SHAFT SINKING METHODS
• Deep shafts for mining present particular problems:
– Depth
– Limited space and complex working sequence
– May pass through multiple aquifers
• Common to use the exclusion approach
– Cementitious grouting (cover grouting)
– Artificial ground freezing
• Rare to use external pumped wells apart from for shallow depths through
granular soils
• Even with exclusion methods there is a need to remove water from shaft
bottom
– Too deep to pump in one lift
– Water often bailed out in hoisting kibble