SEISMIC SAFETY EVALUATION OF THE 250 M HIGH DERINER
ARCH DAMM. WIELAND
Chairman, ICOLD Committee on Seismic Aspects of Dam DesignPöyry Energy Ltd., Zurich, Switzerland
Location of Deriner Dam Site, Turkey
Deriner
Layout Deriner HPP
1. arch dam,
2. diversion tunnel,
3. surface spillway
4. power intake
5. upstream cofferdam
6. cable crane
Dam Site, view from downstreamHangsicherung:
2300 vorgespannte Anker
Arch dam crest el. 397Batching plant, cement silos
Cofferdam
Cable cranesloading platform
Switchyard
Diversion tunnel outlet
Dam Site, view from upstream
Technical Project DataHydrology• Catchment area 18,839 km²• Mean annual flow at dam site 4,847 million m³• Mean annual discharge at dam site 154 m³/s• Design flood 10,110 m³/s
Reservoir storage• Total 1,969 million m³• Active 963 million m³
Diversion Tunnel• Horseshoe tunnel, diameter 11.70 m, 876 m long• Number1 Design discharge 1,804 m³/s
Dam Type• Double curvature arch dam• Max. height 250 m• Length at crest 740 m
Technical Project DataOverflow spillways• Type: Tunnel, diameter 8.00 m, with frontal inlet• Number: 2 Design discharge 2 x 1,125 = 2,250 m³/sOrifice spillways• Type: 8 Orifices in the dam body: size (W x H) 2.80 x 5.60 m• Design discharge 8 x 875 = 7,000 m³/sPowerhouse: Underground, concrete lined• Size (W x H x L) 20 m x 45 m x 126 mTurbines: 4 Francis vertical• Gross head 206 m• Design discharge 4 x 90 = 360 m³/s• Installed capacity 4 x 167.5 = 670 MWTotal annual energy production 2,118 GWh• Firm 1,212 GWh• Secondary 906 GWh
Crushing and sieving plant 2 x 1000 m3/h
Betonierarbeiten
Cable Cranes
• Capacity 3 x 9 m3 buckets• Supplier: KRUPP, Germany
Loading platform
Batching plant• Capacity 360 m3/h
Arch Dam – Site installations
Cement Silos
Batching Plant
Concrete Lab
Arch Dam - Batching plant loading station
Arch Dam – Formwork
Arch Dam – Battery of vibrators
…
Arch Dam – Start of concreting Dec. 2005
Arch Dam – Concreting
Arch Dam
Nov 2003Nov 2003Nov 2003
Arch Dam – Post cooling system
Arch Dam - Concreting
Toe gallery
Post-cooling pipes
Joint grouting system
Arch Dam – Grouting tests from gallery
Deriner Dam & HEPP: > 2000 rock anchors
Overflow Spillway RB - Excavation
Power Cavern
Tailrace Tunnels
Nov 2003Nov 2003Nov 2003
SEISMIC ASPECTS OF
DAM DESIGN
Seismic hazard – multiple hazard• ground shaking: vibrations in dams,
appurtenant structures, equipment and foundations
• fault movements in dam foundation
• fault displacement in reservoir bottom: water waves in reservoir or loss of freeboard
• mass movements into reservoir: impulse waves in reservoir
Ground shakingEarthquakes affect all components of a
dam project at the same time:dam
foundation safety devices
pressure systemunderground works
appurtenant structures hydro-mechanical equipment
electro-mechanical equipment etc.
Seismic design criteriaDam and safety-relevant elements:Operating basis earthquake, OBE (145 years) Safety evaluation earthquake, SEE/MCE (ca. 10,000 years) Appurtenant structures Use of seismic building codes (ca. 475 years)
Temporary structures:Use of seismic building codes (< 475 years)
Design Earthquake Title Element / Component
CE DBE OBE/ SEE
Diversion Facilities - Civil Intake/outlet structures X Tunnel, tunnel liner X - Geotechnical Rock slopes X Underground facilities X Cofferdams X - Electrical/Mechanical Gate equipment X
Dam: Dam Body Dam body X
- Individual Blocks OBE Crest bridge X Crest spillway cantilevers X X Bottom Outlet cantilevers X Foundation/Abutments Abutment wedges X X Bottom Outlet Main gates, Valves X X Guard gate X Operating equipment X X Dam: Electrical/Mechanical Essential parts X
Design Earthquake Title Element / Component
CE DBE OBE/ SEE
Underground powerhouse
- Excavation and Rock Support Rock slopes X - Service Bay Civil Design Substructure X Superstructure X Surface powerhouse - Civil Excavation, foundation X Substructure X Superstructure X - Architectural Layout and Finishes X - Cranes and Lifting Devices Cranes X Support structures X - Generators & Exciting System Stationary components X Rotating components X - Turbine X - Transformers and other components X
SEISMIC STABILITY ANALYSIS OF
DETACHED CONCRETE BLOCKS
SEE/MCE analysis of Deriner arch dam
Dam-foundation model MCE (horizontal PGA: 0.35 g)
Results of linear-elastic dynamic analysis
Large dynamic responses in central upper portion of dam
– Very high accelerations– Large tensile stresses
(exceeding dynamic tensile strength of mass concrete)
Consequences– Contraction joints open – Horizontal cracks develop
along lift joints
Crest deflection under different MCE’s
Selection of detached concrete blocks
Simplified dynamic stability analysis of cracked dam
Step 1: Linear-elastic 3D analysis assuming incompressible (or compressible) reservoir and massless foundation;
Step 2: Nonlinear 2D rocking-sliding analysis of detached concrete blocks
Simplified dynamic stability analysis of concrete blocks: Methodology
1.Linear-elastic dynamic time history analysis;2.Selection of detached concrete blocks;3.Calculation of absolute acceleration response at
base of each block;4.Dynamic rocking-sliding analysis of detached
concrete blocks using 2D FE models; and5.Calculation of the maximum sliding and crack
opening displacements.
Main assumptions
1.Cracks are assumed to form along the vertical contraction joints and horizontal lift joints only.
2.Damping ratio for MCE: 7%. 3.The acceleration response in the central upper
portion of the dam can be obtained from a linear-elastic dynamic analysis.
4.Detached concrete blocks can slide only towards the upstream due to the geometry of the arch dam.
5.Effect of shear keys in contraction joints ignored.
Selection of detached concrete blocks
Finite element model for dynamic stability (rocking-sliding) analysis of 20 m high block
Rocking-sliding analysis of 20 m high block
Initial state During earthquake shaking
Final state
Typical results of rocking-sliding analysis
Horizontal displacement(sliding)
Crack opening displacement at downstream face (rocking)
Results of dynamic stability analysis
• MCE1* reversed MCE1 etc.
Input ground motion
Max. sliding displacement along
crack at lift joint (mm)
Max. crack opening displacement at upstream edge
(mm)
Max. crack opening displacement at
downstream edge (mm)
A) Empty reservoir MCE1 272 129 58
MCE1* 580 154 47
MCE2 525 149 40
MCE2* 622 110 55
MCE3 708 142 76 MCE3* 1045 179 66
B) Full reservoir MCE1 346 136 96 MCE1* 193 65 36
MCE2 307 143 86
MCE2* 233 93 39
MCE3 280 110 30
MCE3* 284 144 47
15 s
25 s
32 s
Results of dynamic stability analysis
Final displacement towards upstream(sliding response)– Empty reservoir: max. 1045 mm– Full reservoir: max. 346 mm– A sliding displacement of about 1 m is
acceptable (dam thickness: 17 m).
Results of dynamic stability analysis
Maximum crack opening displacement (rocking response)– Empty reservoir condition:
Upstream: max. 179 mmDownstream: 76 mm
– Full reservoir condition: Upstream: 144 mmDownstream: 96 mm
– Weaker rocking towards upstream
Discussion of results
•Full resevoir: final sliding displacement is small due to the restoring effect of the water pressure.
•Empty reservoir: The sliding movement towards the upstream tends to be cumulative.
Discussion of results
•The dynamic impulse is shared by a combination of rocking and sliding motions. Thus, smaller rocking response towards the upstream is accompanied by a larger sliding response.
•For a symmetrical concrete block, the final sliding movement of the block towards the upstream would be considerably smaller.
Sensitivity analyses: 20 m block, empty reservoir
Input ground motion
Max. sliding displacement
(mm)
Max. crack opening displacement at upstream edge
(mm)
A) Friction coefficient: 0.7
MCE2 (PGA: 0.35 g) 525 149
2 × MCE2 (PGA: 0.70 g) 1067 336
3 × MCE2 (PGA: 1.05 g) 2648 588
B) Friction coefficient: 0.5
MCE2 (PGA: 0.35 g) 437 18
2 × MCE2 (PGA: 0.70 g) 1691 168
3 × MCE2 (PGA: 1.05 g) 2339 515
Sensitivity analyses: 20 m block, empty reservoir
Effects of lower friction coefficient
• Higher sliding response, and smaller rocking response
• However, not necessarily higher maximum sliding displacement (as lower friction also increases likelihood of reversed sliding)
Conclusions1.Maximum sliding and rocking displacements can
vary considerably. Dynamic stability analyses shall be carried out for several statistically independent input earthquakes.
2.As the effect of the shear keys in the vertical contraction joints has been neglected, the results of simplified rocking-sliding analysis are conservative.
3.The computation of the inelastic response of detached concrete blocks needs careful checks, because the results are sensitive to several numerical integration parameters.