Geology Reference
In-Depth Information
Project concept: high arch dam with high-pressure penstock tunnels (120m hydraulic head)
leading to underground power house, tailrace tunnels and surge chamber. Structures to be
considered include reservoir, ancillary buildings, roads, power lines and diversion tunnel.
Sources of concrete aggregate need to be identi
ed, as well as locations for disposing construction
waste.
General setting: valley with narrowing point suitable for arch dam (high stresses). Topography and
hydrology adequate for reservoir capacity. Steep slopes above reservoir.
Geology from preliminary desk study: major fault along valley, maybe more. Right abutment
(looking downstream) in granitic rock, sometimes deeply weathered. Left side, ancient schist,
greywacke, mudstone and some limestone. Folded and faulted with many joints. Alluvial sediments
along valley.
Environmental
Issues
hazards of
landslide into
reservoir
storms
..
time
quality of water
sedimentation
earthquakes
high pressure
tunnels
construction
stability
lining
abutment
failure
in situ stress
state−
important for
high pressure
tunnels and
underground
chambers
water leakage from reservoir
dam construction
-aggregate source?
-waste disposal
σ
1
σ
2
σ
3
fault
active?
water
pressure
sliding failure
leakage
load from dam
piping failure
stressed zone
Figure B4-5.1 Schematic model of site for new hydroelectric scheme with some of the most important
hazards that need to be quantified during the site investigation.
K
ey issues for investigation:
Dam: stability of foundations and abutments, settlement, leakage, overtopping from landslide into
reservoir, silting up.
Tunnels and powerhouse: rock quality, in situ stress state, construction method, stability, lining and
support requirements.
Reservoir: leakage, siltation, water quality.
Construction: source of aggregate, waste disposal, access, river diversion.
